THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID AN ELEMENTARY COURSE OF BOTANY, STRUCTURAL, PHYSIOLOGICAL, AND SYSTEMATIC. BY PROFESSOR ARTHUR, HENFREY, F.R.S., L.S., ETC. THIRD EDITION. BY MAXWELL T. MASTERS, M.D., F.R.S., L.S., ETC. EXAMINER IN BOTANY TO THE UNIVERSITY OP LONDON. ILLUSTRATED BY UPWARDS OF SIX HUNDRED WOODCUTS. LONDON : JOHN VAN VOORST, PATERNOSTER ROW. MDCCCLXXYIII. [The right of Translation is reserved.} PRINTED BY TAYLOB AND FRANCIS, RED LION COURT, FLEET STREET. PREFACE TO THE THIRD EDITION. IN the preparation of this edition so much has been added, and so much modified, that to some extent the book may be cdn- sidered as a new one. Nevertheless, the Editor has, as far as possible, worked on the plan laid down by Prof. Henfrey, and ex- plained by him in the following quotation from the original Preface. Adverting to some remarks made by Sir Joseph Hooker and Dr. Thomson to the effect that " disservice is done to the cause of Botany by occupying the attention of students in the first instance with the abstract parts of the science," Prof. Henfrey remarks, in terms as applicable now as at the time they were first written (1857), that " The largest class of students of Botany are those who pursue the subject as one included in the prescribed course of medical education. One short course. of Lectures is devoted to this science, and three months is commonly all the time allotted to the teacher for laying the foundations and building the superstructure of a knowledge of Botany in the minds of his pupils, very few of whom come prepared even with the most rudimen- tary acquaintance with the science. To direct the attention of the student to a series of isolated facts and abstract propositions relating to the elementary anatomy of plants, is to cause him to charge his memory or his note-book with materials in which he can take but little interest, from his incapacity to perceive their value or applications. Some of the most important questions of Physiology are as yet in no very advanced state, and the conflicting evidence on many of these cannot be properly appreciated without an extensive knowledge of plants. IV PREFACE. " But if we endeavour to seize the floating conceptions furnished by common experience, and to fix and define them by a course of exact practical observation of the more accessible characters of plants (showing the relations of these as they occur in different divisions of the Vegetable Kingdom), we place the student in a position which enables him to pro- ceed at once with an inquiry into the peculiarities of the plants he meets with, and in this way to acquire a fund of practical knowledge, which is not only absolutely requisite before entering on abstract in- quiries, but is especially calculated to secure his permanent interest in the study. " Physiology is undoubtedly of the highest importance, and from its nature is that part of the Science which, were it not for the above diffi- culties, would with most advantage be taught by Lectures. If the previous education of medical students prepared them, as it should, with an elementary knowledge of the Natural Sciences, we should make Physiology the most conspicuous feature of a course of Botany in a Medical School. In the mean time we subordinate it to the other branches in practical teaching, and in this volume have dealt with it in what we regard as its proper place in the order of study." Since these remarks were written, and owing in part to the advances made in the Science o Vegetable Physiology, the subject has received more attention in this country, while at the University Examinations greater stress than heretofore is laid upon it. How- ever desirable in one sense this may be, it is at present objection- able, because few or no means are open to the average student of making himself practically familiar with Experimental Physiology. Moreover, the skill in manipulation and microscopical observation required for anatomical or physiological investigations cannot possibly be acquired in the few months devoted to the subject by the majority of students and candidates for examination in the Scientific and Medical Faculties. Sooner or later these defects in the practical teaching of Physiology will doubtless be remedied, In the mean time, practical tuition in Morphology and the rudi- ments of Classification appears to be the best and most ready method of training a student to observe, to reflect, and to classify. PREFACE. V By its means also the evil effects of the system of loading the memory with secondhand information of no use whatever outside the walls of the examination-room, and indeed of but little service in the practical examinations (now happily instituted at the Uni- versity of London and elsewhere) may be avoided. In the present edition the additions to the Morphological chap- ters have been chiefly taken from the writings of Braun, Baillon, Eichler, Warming, Van Tieghem, and others. In this department the Editor has also to acknowledge the valuable assistance ren- dered him by the Eev. George Henslow, particularly in the sections relating to phyllotaxis and aestivation. In the arrangement of the Natural Orders the plan adopted by Bentham and Hooker in their invaluable ' Genera Plantarum ' has been followed so far as that work extends. The account of the Cryptogamia has been revised, and that con- cerning the Fungi written afresh by Mr. George Murray, of the Botanical Department of the British Museum, to whom the Editor would here offer his cordial acknowledgments. The Physiological Section has been mostly rewritten, and much has been added to it. Use has been made of Sachs' ' Handbuch der Experimental Physiologie der Pflanzen'; of the English and French translations of the ' Lehrbuch/ of the same author the former published under the superintendence of Messrs. Bennett and Thiselton Dyer, the latter under that of M. Van Tieghem, whose version is enriched with numerous original notes. In addition, the Editor has availed himself of Duchartre's * Elements de Botanique,' Deherain's ' Cours de Chimie Agricole/ and more especially of numerous recent original memoirs published by Bous- singault, Darwin, Trecul, Pfeffer, Janczewski, Coren winder, Van VI PREFACE. Tieghein, Strasburger, Lawes and Gilbert, McNab, Vesque, Rau- wenhoff, Warming, and many others whom it is not possible to specify in a work of this character. Comparatively few alterations have been made to the chapters on Geographical and Geological Botany, which, for their effective treatment, would require another volume. The additions in these subjects have been chiefly derived from the writings of Hooker, Grisebach, Tchihatchef, Williamson, Crepin, and Carruthers. Some additional woodcuts have been supplied, whose source is acknowledged in the text. M. T. M. March 1878. TABLE OF CONTENTS. INTRODUCTION. Page Sect. 1. OBJECTS AND SUBDIVISIONS OF THE SCIENCE 1 Sect. 2. METHODS AND MEANS USED IN THE STUDY OP BOTANY .... 3 PART I. MORPHOLOGY, or COMPARATIVE ANATOMY. CHAPTER I. GENERAL MORPHOLOGY 7 CHAPTER II. MORPHOLOGY OF THE PHANEROGAMIA 10 Sect. 1. GENERAL OBSERVATIONS ON THE CONSTRUCTION OP FLOWERING PLANTS 10 Sect. 2. THE ROOT 14 Sect. 3. THE STEM 20 Sect. 4. THE LEAP 41 Special Modifications of the Leaf and its Parts 66 Sect. 5. THE LEAP-BUD 69 Sect. 6. THE INFLORESCENCE 74 Sect. 7. THE FLOWER AS A WHOLE 86 Sect. 8. THE FLORAL ENVELOPES 103 The Calyx 106 The Corolla , 109 The Perianth , . 114 Vlll CONTENTS. Page Sect. 9. THE ESSENTIAL ORGANS OF FLOWERS 118 The Androscium 119 The Gyncecium 127 Sect. 10. PRODUCTS OF THE ESSENTIAL ORGANS OF FLOWERS 136 The Ovule 136 The Fruit 139 The Seed . . 152 PAKT II. SYSTEMATIC BOTANY. CHAPTER 1. PRINCIPLES OF CLASSIFICATION 158 Sect. 1. SPECIES AND GENERA 158 Sect. 2. NOMENCLATURE 164 Sect. 3. DESCRIPTION OF PLANTS . 170 CHAPTER II. SYSTEMS OF CLASSIFICATION 180 Sect. 1. ARTIFICIAL CLASSIFICATION OF PLANTS 180 The Linncean System , , 181 Sect. 2. NATURAL CLASSIFICATION OF PLANTS 182 The Jutsieuan System 185 DeCandolle's System 186 JSndlicher's System 186 Brongniart's System , 187 Lindley's System 187 Bentham and Hooker's System , 187 Broun and Hanstein's System 188 Sachs 1 System (Cryptoganria only) 189 CarueVs System 190 adopted in this Work 192 CONTENTS. IX CHAPTER III. SYSTEMATIC DESCRIPTION OF THE NATURAL ORDERS. Page SUBKINGDOM I. Phanerogamia 193 CLASS I. DICOTYLEDONES . . .193 SUBCLASS I. ANGIOSPEBMIA 193 Division 1. Polypetalae 193 Series 1. Thalamijlorce Order Ranunculacese . . . .page 195 Dilleniaceffi 198 Magnoliaceae 199 Anonaceae 200 Monimiaceae 200 Menispermaceae 201 Lardizabalaceae 201 Schizandraceae 202 Sabiaceae 202 Berberidaceae 202 Nymphaeaceae 203 Cabombacese 204 Nelumbiaceae 204 Sarraceniaceae 205 Papaveraceae 205 Fumariaceae 207 Cruciferae 209 Capparidacese 212 Resedaceae 213 Bixaceae 214 Cistaceaa 214 Droseraceae 215 Violaceae 215 Sauvagesiaceae 217 Frankeniaceae 217 Tamaricaceae 217 Caryophyllaceas 218 Malvaceae 220 Sterculiaceae 222 Tiliaceas 224 Dipteraceae 225 Series 2. CalyciftorcB Celastraceae 245 Stackhousiaeeae 245 Hippocrateaceae 245 Chailletiacese 240 Rhamnaceae 246 Anacardiaceae 246 195 Order Chlaenacese 225 Ternstrcemiaceae 226 Clusiaceaa 227 Hypericaceae 228 Reaumuriaceae 229 Elatinaceae 229 Sapindaceae 229 Staphyleacese 231 Aceraceae 231 Polygalaceze 231 Tremandraceae 233 Malpighiaceae 233 Erythroxylaceaa 234 Meliace 234 Aurantiaceae 235 Linace 236 Oxalidaceae 237 Geraniaceae 237 Balsaminaceae 238 Vivianaceae 239 Tropaeolaceae 239 Limnanthaceae 239 Zygophyllaceae 240 PCutaceaa 240 Xanthoxylaceas 241 Simarubaceae 242 Ochnaceae 242 Coriarieas 242 Pittosporaceae 243 Vitacese , . 243 244 Sabiaceae 247 Connaraceae 247 Burseraceae 248 Leguininosas 248 Moringaceae 255 Rosaceae . 255 CONTENTS. Page Order Calycanthaceae 258 Myrtacese 259 Lecythidaceae 260 Barringtoniaceae 261 Chamaelauciaceae 261 Belvisiacege 261 Rhizophoraceae 261 Vochysiaceae 262 Combretaceae 262 Alangiaceae 263 Melastomaceae 263 Onagraceae 263 Haloragaceae 264 Lythraceae 264 Saxifragaceae 265 Francoaceae 267 Crassulaceae 267 Paronychiacese 268 Portulacaceae 269 Page 69 Papayaceae 270 Pangiaceae 270 Passifloraceae 270 Malesherbiaceas 271 Turneraceae 271 Saniydaceae 271 Cucurbitaceae 271 Begoniaceae 274 Datiscacea9 275 Homaliaceae 275 Loasaceae 275 Cactaceae 276 Ribesiaceae 277 Hamamelidaceae 277 Bruniaceae 278 Umbellifera 278 Araliacese 282 Cornaceae . . . 283 Division 2. Gamopctalse or Corolliflorse 284 Series 1. Epigijna 284 Qaptifoliecew 284 Rubiaceaa 285 Valerianaceae 288 Dipsaceaa 288 Calyceracege 289 Composite 289 Lobeliaceae 294 Goodeniaceae 294 Brunoniaceae 294 Stylidiacese 294 Campanulaceae 295 Series 2. Superce .... Ericaceae 296 Epacridaceae 298 Plantaginaceae 298 Plumbaginaceae 299 Primulaceaa 299 Myrsinaceae 301 296 JEgiceraceoe 301 Sapotaceae 302 Ebenaceas 302 Aquifoliaceae 303 Styracaceae 303 Series 3. Dicarpice . . Oleaceae 304 Jasmir.aceae 305 Salvadoraceae 305 Loganiaceae 306 Gentianaceae 307 Apocyiiaceae 308 Asclepiadaceae 309 Hydrophyllaceae 311 . 311 304 Polemoniaceae 311 Convolvulaceae 312 Solanaceae 31 3 Cordiaceae 317 Nolanaceae 317 Boraginaceae 317 Ehretiaceaa 318 Labiatae 319 Verbenaceaa 321 CONTENTS. XI Page J. J age Order Selaginacese 321 Acanthacese 322 Bignoniaceae 322 Pedaliaceae 323 Crescentiaceae . . 323 Page Order Gesneraceae 324 Columelliaceae 324 Orobanchaceee 324 Scroplmlariaceas 325 Lentibulariaceae . . 328 Division 3. Apetalae or Incompletae 328 Series 1. Supera 329 Polygonaceae 329 Nyctaginaceae 330 Amarantaceae 330 Chenopodiaceae 331 Basellacege 332 Phytolaccaceae 332 Paronychiaceae 332 PetiveriesB 332 Lauraceae 332 Atherospermaceae .... 334 Myristicaceae 334 Nepenthaceae 335 Thymelacese 335 Aquilariaceae 336 Elaeagnaceae 336 Proteaceae 336 Euphorbiaceae 337 Buxaceae 340 Daphniphyllaceae 340 Scepacese " 340 Penaeaceas 340 Lacisteinaceae 340 Empetraceae 340 Urticaceae 341 Caimabinaceae 342 Artocarpaceae 342 Stilaginaceae , 343 Phytocrenaceae 343 Ulmaceae 344 Platanaceae 344 Myricaceae 344 Betulaceae 345 Salicaceae 345 Oasuarinaceae 346 Cliloranthaceae 347 Piperaceae 347 Sauraraceae 348 Ceratophyllaceae 348 Callitrichace03 349 Podostemaceae 349 Series 2. Epigyna 349 Juglandaceae 349 Cupuliferaa 350 Garryaceae 351 Loranthaceas 352 Santalaceas . . 353 Balanophoraceae 353 Cytinaceae 354 Rafflesiaceas 354 Aristolochiaceae ...... 355 SUBCLASS II. GYMNOSPEEMIA Pinaceae or Coniferse . . 358 Taxaceae . .361 356 Gnetaceaa 362 Cycadacese 364 Xll CONTENTS. Page CLASS II. MONOCOTYLEDONES . 367 Division 1. Petaloideae 368 Series 1. Epigyna 308 Order Taccaceas page 368 Order Musacese 377 Dioscoreaceae 369 Amaryllidaceae 378 Orchidaceae 369 Hypoxidaceae 379 Apostasiacese 374 Haemodoraceae 379 Burmanniaceae 374 Iridaceae 380 Zingiberaceae 375 Bromeliaceae 381 Marantaceae 376 Hydrocharidaceae .... 382 Series 2. Coronariece 383 A. Syncarpite 383 Philesiaceas 383 Commelynaceae 387 Roxburghiaceae 383 Pontederaceas 387 Smilaceae 383 Mayaceae 388 Liliaceae 384 Gilliesiacese 388 Xyridacese 387 Plulydracese 388 B. Apocarpiae 388 Alismaceae 388 | Naiadaceas 389 Division 2. Spadiciflorae 390 Palmaceae 391 Aroidaceae 395 Pandanaceae 394 Lemnaceaa 397 Typhaceae 395 Division 3. Glumifiorae 398 Juncaceaa 398 Restiacese 400 Desvauxiaceae 399 Cyperaceae 400 Eriocaulaceae 399 Graminaceae 402 SUBKINGDOM II. Cryptogamia 408 General Morphology 408 CLASS I. CORMOPHYTA 415 Division 1. Vascularia 416 Series 1. Isosporia 416 Equisetaceas 416 | Lycopodiaceae 423 Klices . . 419 CONTENTS. Xlll Page Series 2. Heterosporia 424 Order Selaginellaceae .... page 424 | Order Kliizocarpeae 426 Division 2. Muscinese 427 Musci 481 Marchantieas 434 Hepaticae 433 Kicciaceee 434 Anthocerotese 433 CLASS II. THALLOPHYTA 435 Division 1. Algae 435 Characese 444 Confervoideae 451 -Rhodospermeae 446 Oscillatoriacpee 453 Eucaceae 449 Diatomaeeae 454 Phaeosporeae 450 Volvocinese 455 Division 2. Fungi 455 Phycomycetes 455 Gasteromycetes .... 464 Saprolegnieae 455 Ascomycetes 464 Peronosporeae 457 Discomycetes 465 Mucorini 458 Erysipheae 466 Hypodermii 459 Tuberaceae , 467 Uredineas 459 Pyrenomycetes 468 Ustilagineae 461 Lichenes 468 Ba'; 29 - f h ot , f , , j. .. stroyed down to the first pair respect, dependent on external conditions; of axillary buds. for both Dicotyledonous trees and Conifers F'g- A shoot, with a terminal differ much in the relative proportion of main trunk and branches, when grown in close plantations, or standing in open situations. Ordinarily, only one bud exists in an axil (fig. 30, 6); but frequent exceptions to this occur, as in some species of Maple, in Honey- suckles (tig. 31), and in the Walnut. How- ever, one of these is generally much larger than the rest, and is called the principal bud, while the others are accessory. In some plants, as in many Solanaceae, the buds occur in an irregular position, arising from the stem at a little distance above the leaf-axils. This is supposed to be due to the adhesion of the bud with the stem, and its uplifting with the latter as it lengthens. The Trunk of arborescent plants arises as an herbaceous stem from the seedling, but usually becomes more or less woody before the close of the first season ; in the autumn it ceases to develop in- ternocles at its point, and the terminal bud closes up into a resting winter-bud enclosed in leaf-scales ; buds of the same sort are pro- duced in the axils of the leaves ; and all or part of them open in the following spring, to produce a second generation of axes in the form of shoots ; the same process being indefinitely repeated, a branched trunk is produced. If the central stem is not much D 2 and solitary (6, 6, 6). Fig. 81. Numerous axillary buds of Lonicera. 36 MOEPHOLOGY, OK COMPARATIVE ANATOMY. Fig. 32. elongated, and the lateral ramifications are numerous, the result is a shrubby plant ; if the growth of the main trunk predominates for a long time, but ultimately slackens, and the side branches grow more, the form seen in ordinary trees appears, where the top of the tree is more or less globose, as in what are called " round-headed " trees, like the elm : while if the growth of the central stem by the terminal bud is predominant throughout life, we have tall straight trunks with comparatively small ascending branches, such as are seen in the Lombardy Poplar, which is an instance of afastiyiate tree. The originally cylindrical form of trunks often undergoes considerable alteration with age, depending upon peculiar modes of development of the woody structure within. Irre- gular prominences occur commonly on such old timber-trees as have large branches, greater enlargement taking place in the line between the base of the branches and the roots ; this is often seen on old Oaks. Some tropical trees produce vast buttress-like projections in the same way. The forms of the trunk of the woody climbing plants of tropical forests present very remark- able irregularities, arising either from a twining habit, or from ir- regular development caused from lateral pressure or otherwise. In some kinds of Bomlax (fig. 32), and in Delabechea (Bombaceae), the trunk is swollen out in the shape of a great flask between the root and the main branches. The Stock or caudex is an undivided woody trunk, produced by the annual unfolding of a single terminal bud. Its interuodes are commonly little developed, so that its sides are marked with the scars of its fallen leaves ; sometimes, however, the interuodes are developed, and then the stock has a jointed appearance, from scars or actual articulations at the nodes. The stocks of the Cactacea3 are remarkable for their form and consistence (figs. 35-37); their lateral buds are developed into tufts of spines, svhich are the repre- sentatives of the leaves of undeveloped branches. The stock of the Palms exhibits considerable variety of form. In the Cocoanut- ( Coco* ) and Date-palms the internodes are scarcely developed, and the scars of the leaf-stalks, arranged in spiral order, cover the sides. The same holds good of the stock of (Jycas and its allies, of Xanthorrhcea, and other arborescent Monocotyledons, and also of the stock of the Tree- Trunk of a Brazilian Bombax. THE STEM. 37 ferns (fig. 34). In other cases an internode is more or less developed be- tween each leaf, and the stem is marked by a succession of scars running nearly round the stem (fig. 33), as in Mauritia and Astrocaryum vulgare- in Geonoma and Chamcedorea the internodes are developed and the nodes thickened, so as to appear externally somewhat like those of the stems of Grasses, but they are not really articulated nor hollow like the latter. The caudex of the Palms furnishing the common Cane (Calamus) is chiefly distinguished from the last by the slenderness and extreme length Fig. 33. Fig. 34. Fig. 33. Palm-tret' (Areca) with unbranched caudex. Fig. 34. An arborescent Fern with unbranehed caudex. of the internodes. Many of these Palm-stocks, which are simple in their principal mass, send out axillary buds at or below the ground, which form runners, and ultimately grow up independently of the parent. The aerial stocks of a few branch high above the ground, as in the Doum-palm and in Pandanus (fig. 10), where the terminal bud appears to undergo successive bifurcations, but really sends off at intervals single axillary buds, the development of which soon* equals that of the parent axis, and causes the deflection of the latter so as to give a forked appearance. A similar mode of growth is observed in certain Haemodoraceae (arborescent Mono- cotyledons, natives of S. America), also in the Liliaceous genus Yucca. The stocks of some of the Cactacese are undivided, as in Melocactus (fig. 36), Echinocactus, and Mamittaria, &c. ; but in others a few branches arise, giving a compound character, as in various species of Cereus (fig. 37) and in the leaf-like stalks of Opwitia (fig. 35). Analogous structures occur in foreign species of Euphorbia. 38 MORPHOLOGY, OK COMPARATIVE ANATOMY. Fig. 38. Fig. 35. Fig. 36. Fig. 37. Fig. 35. Btem of Opuntia. Fig. 36. Stem of Melocaetus. Fig. 37. Cylindrical and ribbed stem of Cereus. Fig. 38. Diagram to illustrate the nature of a sympode, the imperfect separation (so called adhesion) of leaves, and the uplifting of the latter with the growth of the shoot; the primary shoot ending in a terminal bud which is deflected to one side, la, one of the leaves of the primary shoot 1, in its ordinary position. 1 b, another leaf of the same shoot adherent to or undetached from 2, the shoot produced in the axil of 1 b, and carried up with 2 in its upward growth. The shoot 2, 2, with its leaves 2 a, 26, grows in the same manner and others succeed it. Ihe portion of the main axis marked 1,2, 3, 4, 5 in one vertical line is a sympode. being composed not of one continuous axis of one and the same generation, but of a series of axes of different and successive generations, ranged in vertical order. Ramification. The same general methods occur in the branching of roots, of stems, of leaves, and of inflorescences, and indeed are also met with in purely cellular plants, as in Algae and Fungi. Caulerpa, though strictly unicellular, has mimic stem-hranches, leaves, and roots. Growth takes place by means of growing points (puncta veyetationis), which will he more fully described under the head of Minute Anatomy, and which, in the case of stems, are enclosed within, and form the central terminal mass of the buds. The growing point is terminal or lateral, primary or secondary. If at the end of a shoot or branch it is terminal and* primary, or of the Jirst degree; if at the side of a shoot it is lateral and secondary, or of the second degree. In the latter case it is lateral because it is pushed out from the side of the primary shoot beneath its apex, and it is secondary because it is necessarily formed after the primary growing-point, and belongs to a subsequent generation. In like mariner we may have in succession ter- tiary buds, or shoots of the third, fourth, fifth degree, and so on. Monopodial branching. By the growth of terminal buds or growing- THE STEM. 39 points the stem is continuously lengthened in one direction ; by the deve- lopment of lateral ones from below upwards (acropetal) it becomes branched. This mode of growth is called monopodial (tig. 27). Dichotomy. In some instances (e. y. the tendrils of some vines, the roots of Lycopod's, and frequently in Cryptogams) the terminal growing-point bifurcates. Each pair of new shoots so formed is then of the same degree or order, because each is formed from the same original growing-point and at the same time. The growing-point may, in this manner, divide into several divisions of the same generation or relative order. The shoots formed dichotomously, as above explained, are monopodial or indefinite as to their ramification, and may grow equally and regularly, or the growth may be arrested in certain of them, and hence may arise much difference in the appearance of the mode of branching. Dichasium. In the foregoing illustrations the terminal growing-point either continues to lengthen as growth goes on, or it divides into divisions of equal degree, though often of unequal vigour. But it very commonly happens that the terminal growing-point or bud ceases to grow after a time (figs. 28, 29). This may happen accidentally or from the effects of frost or other injury, however caused, or it may occur constantly and naturally, as in many trees, e. g. the Lilac (fig. 29). When arrest of growth in the terminal bud takes place in the manner just indicated the lateral buds often grow so vigorously, and are so closely placed, that they appear to radiate from the same point as if they were formed by dichotomy of the terminal growing-point. This false or apparent dichotomy is sometimes called a dichasium or false cyme (fig. 28). Sympode. When in the case of a dichotomous ramification one of the divisions grows more vigorously than the other, or, which amounts to the same thing, when one of them is arrested in its growth or altogether sup- pressed, then, although the two divisions are of equal degree and age, yet the stronger of the two presents the appearance of and grows in the same direction as the primaiy shoot, while the smaller one is often pushed on one side, so as to look like a lateral shoot of a subordinate degree (fig. 38). The appearance may thus be that of a continuous shoot formed by the extension of one growing-point and giving off lateral branches ; but in reality the shoot is not the result of the extension or bifurcation of on growing-point, but of a number of growing- points of different generations formed in suc- cession one after the other. In this way what is called a sympode is pro- duced, and ramification so characterized is sympodial. This arrest of growth may take place regularly or irregularly, producing corresponding variations in the form of the ramifications : thus, supposing a branch to divide into a number of subdivisions by repeated bifurcations to the right hand or to the left respectively, it may happen that all the shoots on the one side are arrested in their growth as compared with these on the other. Or it may happen that the arrest of growth may take place first on one side arid then on the other in regular alternate order. All these modifica- tions may be seen in the mode of branching in various cellular Cryp- togams as well as in higher plants. Characters of the Stem and Branches. In the description of stems and branches generally, certain technical terms are in use, in addition to those above explained. These refer principally to a. consistence ; b. direc- 40 MORPHOLOGY, OR COMPAEAT1VE ANATOMY. tion and habit of growth ; c./orw; d. condition of surface; e. ramification ; and f. dimensions. a. Consistence. The terms herbaceous (Jierbaceus) and woody (lignosus) need no further definition. Some stems are fleshy or succulent (carnosus\ as in Cactus, &c. Most steins are solid (solidus) ; those of the majority of Grasses and the Umbelliferae (Carrot, Celery, &c.) and the Horsetails (Equisetum} are hollow or tubular (Jistulosus). b. Direction. Stems may be truly erect (strictm), flexuom (flexumus) or nodding (nidans, cernuus). Stems which turn upwards from a horizon- tal base are called ascending (ascendens) ; those lying along the ground without rooting are procumbent or prostrate (decumbens, procumbens, hu- mifusus) (fig. 39) ; if a pro- strate stem roots at its nodes, it becomes creeping (repens). Slender stems neither lying on the ground nor creeping may be pendent (pendulous) Fig. 39. Procumbent stem of Thyme. when growing on rocks &c., and floating (Jluitans] when growing in water. Weak stems also rise from the ground as climbing (scandens) or twining (volubilis) stems. Climbing stems support themselves in various ways : the Ivy by tufts of adventitious roots, which attach themselves firmly to foreign bodies ; the climbing species of Clematis and the Canary-creeper (Tropceolumpere- grinum) by hooking their leaf-stalks round the support ; other plants by tendrils, as the Vine, Peas, Cucurbitaceze, &c. Twining stems coil themselves spirally round the supporting body, turning sometimes in one direction, sometimes in the other, as in the Hop, Convolvulus, Cuscutfij &c. If the direction from below is from the left upwards to the right hand of the observer, supposed to be standing in the position of the body around which the coil winds, the coil is said to be dextrorse, if in the opposite direction sinistrorse ; but by some writers the observer is supposed to stand in front of the coil, and then the application tf the terms is reversed. Some of the tropical twiners produce woody orunks resembling large cables. c. Form. The principal variations in form are designated by terms re- quiring no explanation, such as cylindrical or terete, conical, columnar, &c. If a stem presents thickenings Fig. 40. Fig. 42. opposite the origin of the leaves (nodes), it is called knotted (no- dosus) ; the reverse condition, when there are constrictions at intervals, is called jointed (articu- latus). Other terms refer to the shape as displayed in a cross sec- tion of the stem. A stem is terete (teres) when it presents a circular section ; compressed (compressus) when the section is elliptical ; angular when the section is polygonal, under which head are distinguished, in a three-angled stem for example, trique- Fig. 40. A triquetrous stem. Fig. 41. A quadrilateral or square stem. Fig. 42. A ribbed stem. THE LEAF. 41 trous if the three angles are sharp (fig. 40), triangular if they are about right angles, and trigonous when the angles are obtuse or rounded off. When the surface presents a great number of longitudinal ridges, it is called ribbed (tig. 42) : numerous longitu- dinal grooves render it furrowed (snlcatus). In some cases the projecting angles of stems are winyed (alatus), as in many Thistles ; in other cases the stem or branch is flattened, so as to resemble a leaf, in which case the term cladode is applied, as in Ruscus (fig. 43). Such leaf-like branches or cladodes are distinguishable from true leaves by their axillary position, mode of origin, internal structure, and by the circumstance that they bear flowers. Foliaceous cladodes of The apex of a stem or branch is usually pointed Pu*cu aculeatu*. or conical, but it may be globose or concave, as in the flower-stalk of a Rose. d. The surface of a stem may be smooth (Icecis) or striate (striatus), i.e. marked with tine grooves and ridges. It may be devoid of epidermal appendages or glabrous (glaber), or furnished with a more or less dense coat of hairs, bristles (setosus),or thorns (epfaofttt). Similar terms are still more commonly applied to the surfaces of leaves. e. Ramification. A stem is either simple or branched; if the ramifica- tion is excessive, it is called much-branched (ramosissimus). The branches may be erect, spreading (patens), outstretched (divaricatus), deflexed (de- flexus), OT pendulous (pendulus). These qualities especially affect the crown or head of trees. f. Dimensions. Different terms are applied to plants with woody stems, according to their size and mode of branching. A tree (arbor) is a plant with a woody trunk and branched head. A shrub or bush (frutex) is a kind of dwarf tree, where the main trunk is little developed, but the lateral branches very much so. Under-shrub (fruticulus) is the dimi- nutive of this. Sect. 4. THE LEAF. Leaves are the lateral organs issuing from the ascending portion of the stem and its branches below their growing points, and in general are flat, expanded plates, produced directly from the superficial part of the stem, and from which, after a certain term of existence, they are removed, either by breaking off at a distinct joint, or by decay. The simplest leaves occur as flat plates traversed by a nerve, as in Mosses. In many Algae and cellular Cryptogams processes of the thallus may be seen resembling leaves in form and arrangement, but not in struc- ture. The term phyllome is used in a comprehensive sense to signify any leaf, or modification of a leaf, springing from a caulome or axis. In some cases, as in Cactus (figs. 35-37), the true leaves are absent, their office being filled by the green stem. Normal leaves, belonging to the vege- tative system, are alone taken into account in this chapter ; the modified foliar organs composing flowers must be treated separately. 42 MOKPHOLOGY, OE COMPAEATIVE ANATOMY. Fig. 44. Fig. 45. The leaves arise from and mark the nodes of the stem ; and it has been already stated that it is at the nodes, in the axils of leaves, that lateral or axillary buds are as a general rule produced. From this it follows that the arrangement of the leaves must be of great importance, not only in reference to their own relative positions, but as determining more or less completely the plans of ramification of stems. It is found that the modes of arrangement of leaves are in accordance with certain general laws ; and a particular study of these laws has been pursued, under the name of Phyllotaxis. Leaves exhibit two principal types of arrangement : either they are solitary, one only occurring at a node, or two or more spring from the stem at the same level. When the leaves stand alone, they are said to be alternate or scattered (fig. 44); where two stand at the same level, facing one another, they are called opposite (fig. 45); and if more than two originate at one level, forming a circle, the leaves are called ulwrled or Verticillate. Kg. 45. Diagram of the arrangement of decussate op- Yery rarely two leaves ap- posifce and tetrastichous leaves - pear to spring from, the same node, as in what are called geminate leaves (Solanum). This condition is supposed to arise from irre- gular displacement and partial adherence of one of the leaves to the stern, or from division of one leaf into two. Really whorled leaves are not so common as is sometimes imagined, the whorled condition being imitated in some cases, as in many Stel- latae, by an excessive development of interfoliar stipules ; truly whorled leaves are seen in Paris and Myriophylluin. Representatives of the two principal types are found in the embryo of Monocotyledons and Dicoty- ledons the former having a solitary cotyledon, the latter having two, placed the one opposite to the other (fig. 3) ; but this opposite arrange- ment of the cotyledons is not always associated with a like disposition of the true leaves. Alternate leaves exhibit many modifications of arrangement. Sometimes they are truly alternate ; that is, the second leaf is exactly on the opposite side of the stem from the first, and the third exactly over the first : a series of leaves arranged in this way - 44 ' Dia ,Bm of the arrangement of alternate disti- CHOUS 1CRV68. THE LEAF. 43 form two perpendicular rows. Such leaves are termed distichous or two-ranked (tig. 44) ; examples of which are found in the Grasses. If the second leaf is not opposite to the first, but at a point dis- tant from it one third of the circumference of the stem, and the third leaf one third further round, the fourth leaf, likewise distant one third from the preceding, will stand over the first. Leaves so arranged form three perpendicular rows, constituting the tristichous or three-ranked arrangement, which is common among the Mono- cotyledons (fig. 46). Now when a line is drawn round the stem so as to pass regu- larly from leaf to leaf, we find that its course is spiral. In the distichous case the spiral line starting from any given leaf com- pletes one circuit and then commences a new one at the third leaf ; in the tristichous arrangement the spiral completes one circuit and begins a new one with the fourth leaf (fig. 46). The series of leaves included by the spiral line in passing from the first leaf to that which stands directly above it is called a cycle (fig. 47) ; the fraction of the circumference of the stem which measures the angular distance between any two succeeding leaves in a cycle when projected on a plane is termed the angular divergence. In Fig. 48. F g. 46. Projection of the ^ arrangement. Fig. 47. Horizontal projection of a cycle of the ^ arrangement. Fig. 48. Projection of the f arrangement. Fig. 49. Horizontal projection of a cycle of the f arrangement. the distichous, represented by the fraction j, it is one half of 360, or 180; in the tristichous, or j, it is 1^0. These fractions not only represent the angular divergence, but 44 MORPHOLOGY, OR COMPARATIVE AXATOMY. also the entire character of the arrangement ; for the numerator, as is seen, indicates the number of turns of the spiral forming a cycle, while the denominator expresses the number of leaves in that cycle. In the pentastichous, quincuncial, or Jive-ranked arrangement the sixth leaf stands over the first (figs. 48 & 49), commencing a second cycle ; but the spiral line passing through the iirst live leaves makes two circuits round the stem ; moreover the successive leaves stand at a distance from each other of two fifths of the circumference of the stem, or 144; while the expression of the angular divergence, -f, indicates also the number of turns round the stem in the cycle, and the number of leaves in the cycle, as before. The next degree of complexity of the arrangement is where eight perpendicular rows of leaves exist, and the ninth leaf is over the first. In this case the spiral takes .three turns in completing the cycle ; and the expression | indicates three eighths of the circumference, or 135, the angular divergence of the successive leaves. When we place the foregoing figures together, thus : J, , f , , it will be observed that each fraction has its numerator composed of the sum of the numerators of the two preceding fractions, and its denominator of the sum of the two preceding denominators ; and it is really found that all higher compli- cations, in normal conditions of steins, *% ^' exhibit some further indication of the same ratio, and are marked succes- sively by JL, ft, }, fi &c.* The simpler forms of arrangement are the most common ; those marked by higher fractions are chiefly found in plants with the leaves much crowded, as in the House-leek. The scales of the cones of Pines and Firs offer good examples of these spiral arrangements. The following- examples may be mentioned for observa- tion : Rosette of leaves of Plantago media, Plan A. Leaves of Grasses, Vanda. Iris. seen from above : the leaves on the Gladiolus, Elm, Lime, &c. |type " * [The mathematician will observe that these fractions are the successive convergents of the continued fraction r , - - &c., and that any leaf being taken as No. 1, the second must lie between 120 and 180 from it. Its position, corresponding successively to each of the above series of fractions, oscillates alternately on either side of a point indicated by the limiting value of the continued frac'tion, viz. 137 30' 28"+. G. H.] THE LEAF. 45 Plan A. Leaves of Sedges (Carex, Sci?-pus), Tulip, Alder, Birch, &c. Plan f. Leaves of Apple, Cherry, Poplar, Oak, Walnut, &c. Plan f . Leaves of Flax, Plantain (Plantayo) (fig. 50), Holly, Aconite, c. Plan jV Eyes (buds) of Potato-tubers, cones of Pinus Sirobus (fig. 51). Plan ^j. Cones of Spruce-fir (Abies excelsa). When the leaves are very numerous and much crowded, it is often difficult to trace the fundamental spiral, as the vertical ranks are not Fig. 51. 26 27 24 oo 23 20 18 13 1(3 11 14 15 12 10 Cones of Pinus Sirobus, with the scales in the J>_ arrangement. evident. In these cases the arrangement is ascertained by studying the secondary spirals which appear. These are more or less numerous, ac- cording as the fractional expression of the fundamental spiral is higher. For example, in examining the cone of the White Pine, a complex spira arrangement is at once recognized, which will be understood by 46 MORPHOLOGY, OR COMPARATIVE ANATOMY. reference to the adjoining diagram (fig. 51). Assume any scale as No. 1. Select the scale over it, in as nearly a vertical line as possible, such as that numbered 14 in fig. 51. Secondary spirals parallel to each other will be seen running to the right and to the left hand. Such are indi- cated by the numbers 1, 6, 11, 16, &c. to the left, and by 1, 9, 17, c. to the right of the reader. Or, again, very depressed spirals are formed by the scales marked 9, 11, 13 (not seen) 'to the left, and by 6, 9, ]2 (not seen) to the right. Of all such spirals, select the two most elevated, which pass by and overlap the scale immediately over that chosen as No. 1. These will be the spirals indicated by the numbers 1, 6, 11, 16, &c. to the left of No. 14, and by 1, 9, 17, 25, &c. passing to the right hand of that scale. Count the number of secondary spirals parallel to these two respectively. There will be found to be eight such parallel spirals in all sweeping round to the right; andy?^, such as 1, 6, 11, 16, c., to the left. Take the lowest of these two numbers, or 5, as the numerator, their sum, 5+8, or 13, as the denominator, and ^ will be the fraction required. To prove this, numbers must be assigned to every scale of at least the first cycle, *. e. those included between No. 1 and' that numbered 14 in the figure. Starting with the scale assumed as No. 1, add 8 (that is, the number of parallel spirals to the right) to 1, and write 9 on the next scale, as in fig. 51. Add 8 again, and write 17 on the next, and so on. Again, add 5 to 1, and write 6 on the adjacent scale on the left-hand spiral ; add 5 to 6, and write 11 on the next, and so on. Two entire secondary spirals intersecting at No. 1 will thus be num- bered. To number any other scales, we may start from either of these spirals, always adding 5 to the number of any scale on going from right to left, and 8 on going from left to right : thus, 6+8 = 14. 14+8 = 22, or, 9+5 = 14. 17+5 = 22. So that we can assign by either method the numbers 14 nnd 22 to the S'oper scales. Similarly all the scales of the cone can be numbered, nly those of a lower number than 6 and 9 are obtained by subtraction of 8 and 5. Now, it will be seen that 14 will be the number of the scale directly over No. 1. This proves that the denominator is correct, for there will be 13 scales in the cycle. Secondly, having, we will assume, numbered all the scales of the cycle between Nos. 1 and 14, if the cone be held erect, and is made to revolve while the eye passes from No. 1 to No. 2, then on to No. 3, &c., up to No. 14, the observer will find that he revolves the cone exactly five times. In other words, a spiral line passing through the scales 1, 2, 3, 4 . . . up to 14, which constitutes one cycle, will coil five times round the axis. The perpendicular distance between the points of origin of successive leaves is dependent simply on the degree of development of the internocles of the stem. These may be so short that, as in the common Stone- crop (Sedum acre), Araucaria imbricata, &c., THE LEAF. Fig. 52. the leaves overlap more or less along the developed axis ; such leaves are termed imbricate ; and this condition is verv common in the leaf-scale forms of the leaf. A great number of well-developed leaves are often crowded together by the non-development of inter- nodes at the base of the flowering stems of perennial herbs, such as the various Saxifrages, the Turnip, Dandelion, &c. ; and where these so-called " radical " leaves are arranged with some regularity, and spread out horizontally as in the House-leeks, they are said to be tufted, cwspitose or rosulate (fig. 50). A somewhat similar condition occurs upon branches of some trees, on which a number of leaves appear to spring from one point, as in the Larch (tig. 52) and the Berberry; the collections of fasciculate leaves really belong to a branch the internodes of which are not developed, so that they all spring at once from the leaf -axil in which the branch-bud was formed. Fasciculate leaves of the Larch. Fig. 53. In other Conifers the number of leaves in these bundles is smaller and very regular and characteristic ; e. (/., in Pinns sylvestris two leaves are thus associated, in P. Cembra three, in P. Strobus five, &c. In those buds of the Larch which afterwards unfold into shoots, the transition from a fasciculate into a regular spiral arrangement becomes evident. Opposite and wJiorled leaves likewise exhibit great regularity. The number of leaves in a whorl is here also sometimes expressed by a fraction, which is enclosed in a parenthesis ; the denominator in this case indicates the number of leaves in one circle. Examples of those in true leaves are furnished by the following plants : plan (opposite leaves). Pinks, Labiatse. Lysimachia vulgaris, Trillium. Paris qiiadrifolia. () Myriophyllum pectinatum. Sometimes the numbers vary on different parts of the same stem, as in TLippuris. When leaves are opposite, the pairs are almost invariably alternate * ; that is, they cross at right angles, the third pair standing over the first. Such leaves are called decussate (fig. 53). With whorls of three leaves, (I) Q-) Diagram of decussating pairs of leaves. An exception is seen in Potamogcton. 48 MORPHOLOGY, OR COMPARATIVE ANATOMY. again, we usually find a similar alternation ; the leaves of the second \vhorl stand over the intervals between those of the first, the leaves of the third whorl standing over the leaves of the first. [There is reason to believe that the arrangement of alternate leaves has resulted from the development of the internodes between opposite leaves ; for when the latter occur at the base of a stem and alternate leaves above, it will be found that, as the internodes are gradually developed, the leaves always appear in succession in a spiral order ; and most frequently the sixth falls over the first, that being the last out of three pairs of decus- sating leaves ; or else the ninth falls over the first, that being the first leaf of the fifth pair. The leaves on becoming alternate soon cease to be decussating, and gradually acquire their proper angular divergence. Moreover, as decussating pairs of leaves can give rise to the ordinary series of fractions, f , f, T 5 4 , 5 8 i> so alternating whorls of "threes" give rise to the series -I, ^ yV- Both kinds can be well studied in the Jerusalem Artichoke. G. H.] 2 o 3.8 7.4 9 Diagram illustrating the order of development of leaves when the internodes are beginning to be formed, and before the proper angular divergences exist. Conversely, if the internodes between the component leaves of any individual spiral cycle were undeveloped, while those between successive cycles were lengthened, a vertidllate arrangement would result. In certain plants (for example, the Myrtle, the Antirrhinum) alternate and opposite leaves occur on the same stem. This is the case also in those Dicotyledons where the true leaves succeeding the opposite cotyledons are alternate, as in the Scarlet Bean, Mustard, &c. It is requisite to distinguish between simultaneous whorU, where the parts composing it are developed simultaneously, and successive whorls, where the parts are developed successively, but are brought together by the non- development of the internodes. The arrangement of the leaves in the manner above indicated is to a greit extent connected with the deposition of the fibre-vascular bundles of the stem. It should, however, be stated that the arrangement of the leaves on the stem is not always the same as that on the branches. Certain terms are in common use in descriptive works to indi- cate the absolute position of the leaves upon the stem. The name radical leaves is applied to those, usually of larger size than the THE LEAF. 49 rest, which are often found collected at the base of flowering steins of herbaceous plants, such as the Dandelion, Lettuce, Turnip, Plantago (fig. 11, p. 21), &c. The ordinary leaves of the stem are sometimes distinguished as cauline or stem-leaves, while the term ramal is occasionally used for those on the shoots of trees and shrubs when these present special characters. The leaves belonging to the inflorescence are called bracts. Their phyllotaxis generally agrees with that of the stem-leaves. The point whence a leaf springs from the stem is commonly called the insertion. Leaves are either articulated there, separating when dead by a distinctly characterized line of fracture, or they merely wither down, and leave their bases as a ragged covering to the stem ; the latter condition occurs mostly in leaves with sheathing bases. A perfect leaf is divisible into two regions (fig. 54) the blade or lamina (b), and the leaf-stalk or petiole (c) ; the latter, when present, may be more or less completely represented by a sheath or vagina (a), partly or wholly embracing the stem from which it arises. At the base of the petiole often occur distinct leaf-like appendages, called stipules. All parts of the leaf blade, stalk, and stipules are much subject to modification, and may even exist in the forms of tendrils, spines, pitcher-like organs, &c., very unlike Fig. 54. Fig. 55. Diagram of the regions of a leaf : a, sheath; b, blade ; c, stalk. A st ilked simple leaf equally cordate at the base. regular leaves. These metamorphosed leaves, or parts of leaves, are best treated of separately. 50 MORPHOLOGY, OE COMPABATIYE ANATOMY, The stalk-like petiole (fig. 55), most common in Dicotyledons, always has the base slightly widened out at its point of emergence from the stem ; in the leaves of Palms, the Banana, Scitaminese, &c. the base is expanded so as to embrace the stem, while in the Grasses the petiole is entirely represented by a sheath (fig. 59). The green part of the leaves of the Hyacinth and other bulbous plants is the blade, and will be found continuous below with a colourless, fleshy, petiolar portion, forming one of the "coats " or sheaths of the bulb (fig. 17, p. 25). The leaf may, however, be represented by one only of the regions. It is very common to find leaves without distinct petioles, the blade springing directly from the stem: such leaves are called sessile (fig. 56). On the other hand, tbe petiolar region may exist with- out the blade ; and among the cases of this sort a considerable variety of conditions is met with. Petiolar structures, devoid of laminae, and more or less reduced to scales or membranous sheaths, are commonly found on subteranneous stem-structures, such as bulbs, rhizomes, &c., whence we have denominated this part of the stem the " leaf-scale region." Similar scales appear in place of green leaves in the "true-leaf" region of various parasitic plants, such as Orobanche, in which the leaves have no physio- logical function to perform; and they recur periodically on the stems of arborescent plants which form winter buds, in the shape of bud-scales. In the true-leaf region the blade is either supported on a stalk-like or sheathing petiole, or is sessile. The sessile con- Fig. 57. Fig. 58. Fig. 56. Fig. 56. A sessile leaf. Fig. 57. Phyllodium of an Acacia. Fig. 58. Two phyllodia of Ozali* latipes, one with a ternate Wade. dition is generally more common toward the upper part of stems and shoots ; and in the bracts or leaves belonging to the inflores- cence the petiolar region is comparatively seldom developed. The THE LEAF. 51 first leaf ( VorUatt of the Germans) on a branch in many Mono- cotyledons is of a different form from the rest, and is found in the angle between the branch and the stem from which it springs. In Dicotyledons there are often two such leaves at the base of a branch, right and left, and occasionally they are united into a tube. They are sometimes formed after the other leaves according to Hofmeister. In some families the true-leaf region is clothed with petioles expanded into the form of laminaB ; these are called phyllodes (figs. 57 and 58), and in such cases the true laminar region is often partially or entirely suppressed. The transition from the petiolar leaf-scale organs into perfect leaves with sheathing petioles may be observed not only in bulbs, but in many Grasses with creeping stems, which exhibit, at the junction of the leaf- scale and true-leaf regions, sheaths surmounted by short green lancet- shaped laminae, increasing in length in successive leaves. Stipules. When the petiole appears as a distinct leaf-stalk, it is often accompanied by a pair of more or less distinct foliaceous appendages at its base, 'called stipules. When these exist, the leaf is called stipulate (fig. 63) ; when they are absent, exstipulate. The presence or absence of stipules is often a very constant character of Natural Orders. The various forms of stipulate petioles form a kind of transition to the petioles with sheathing bases. Petiole. The petiole is usually of semicylindrical form, with the flat surface above ; not unf requently this upper surface is channelled (canaliculate}, giving a more or less crescentic section ; in a few instances, especially in the Aspen, it is laterally compressed. Where it is cylindrical its structure is like that of a branch. The stalk-like petiole is either simple, when it supports a single blade, or it is branched or compound, when the blade is composed of a number of distinct leaflets ; the branches are sometimes called partial petioles, and may even be articulated at their points of origin from the primary petiole. Compound petioles supporting the leaflets of compound leaves are known from branches, which at first sight they resemble, by arising independently from the stem, by having buds in their axils, and by the absence of any indication of a leaf immediately beneath them. Phyllodes. The flattened or leaf-like petiole, called a phyllode, resembles a lamina, but is known by standing edgewise on the stein that is, with its flat faces parallel with the direction of the E2 52 MORPHOLOGY, OR COMPARATIVE ANATOMY. stem ; in some cases pliyllodes exist without true laminae (fig. 57), in others the laminae are more or less developed at the summit (fig. 58). Striking examples of phyllodia with or without laminae are furnished by various species of Acacia (figs. 57 & 101), in many of which the blade is present, compound and bipinnate. Vagina. The sheathing portion or vagina is the only portion o the petiole which is developed in certain plants, as in the Grasses and Sedges (figs. 59-61), in which it forms a complete sheath to the stem, and passes at once into the blade at the top : this sheath is merely rolled round the stem in the Grasses ; but its margins are not disunited, but form a tube, in the Sedges. The vaginal petiolar region is more or less distinctly evident in many Mono- cotyledonous leaves which at first sight appear to be sessile, as in the Tulip, Hyacinth, &c. ; and it is generally more or less developed at the base where a distinct leaf-stalk exists in this class, as in the Palms and, above all, in the Musaceae. In many Dicotyledons also the base of the petiole is enlarged into a sheath, as in Umbellifers (fig. 62). Fig. 61. Fig. 62. Fig. 59. Fig. 60. Fig. 59. Leaf-sheath of a Grass, with an entire liqula, *. Fig. 60. Leaf-sheath of a Grass, with a bifid ligula, *. Fig. 61. Leaf- sheath of Eriophorum. Fig. 62. Sheathing base of the petiole of A ngelica. Sometimes the petiole is winged (alate), as when a narrow plate of the blade structure springs from its margins ; in certain cases these wings are decurrent down (or, rather, are continuous with the sides of) the stem from which the leaf arises, as in many Thistles, Verbascum, &c., producing a winged or alate stem. Cicatrix. The petiole is ordinarily more or less distinctly jointed to the stem ; and when the leaf falls, it leaves a more or less ex- tensive well-defined scar upon the stem, called the cicatrice-, in THE LEAF. 53 woody Dicotyledons there is generally a little protuberance under the cicatrix, which is termed the pidvlnus. In Monocotyledons the cicatrix is usually very broad, from the base of the petiole em- bracing the stem widely. In some cases the petiole is not regularly disarticulated, but withers down ; but then the decay generally termi- nates at a definite point a little above the base, leaving a portion of the latter in the form of a scale-like or tooth-like process projecting from the stem. Tooth-like processes left by the decay of the petioles may be seen on the underground stem of the common Primrose &c., and on the trunks of certain Palms. Stipules. The stipules or leaf-like append- Fig. 63. ages of the petiole usually stand at the base of the petiole, one on each side, free or adherent to it (fig. 63). The free leafy stipules are sometimes highly developed, and in Lathyrus Aphaca they exercise the functions of the blade, the leaves of this plant consisting merely of a petiole destitute of a lamina. TV hen the mar- gins of the stipules next the petiole are con- tinuous with that organ, forming as it were wings to it (Rosa), they are called adnate (fig. 64). They are also often united by their margins independently of the petiole, or, in other words, are not separated from each other (connate) : thus in the Plane tree and in Astragalus they are united by the outer mar- Leaf of Lotus with free stipules. Fig. 64. Fig. 65. Compound (pinnate) leaf of the Rose, with adnate stipules. Ocrea of Polygonum. gins (turned away from the petiole) so as to form a kind of leaflet on the opposite side of the stem (intrapetiolar) in Potamoyeton 54 MORPHOLOGY, OE COMPARATIVE ANATOMY. they are united by their inner margins above the petiole, so as to form a compound axillary stipule ; in the Polygonacese they are not only united on this side, but also by their outer margins on the other side of the stem, thus forming a short tubular sheath round the latter, called an ocrea (fig. 65). All the above cases relate to stipules of single leaves ; but similar coherence or lack of disunion occurs in the stipules of opposite leaves, where it is not uncommon to find the two stipules which stand between the leaves, at back and front, more or less confluent into a single leaf-like or scale- like body (interpetiolar stipule), so as to form a kind of whorl with the true leaves. This interpetiolar confluence of the stipules is very characteristic of the Order Rubiacese ; and the apparent whorls of the Stellatce (Galium, &c.) often exhibit a confluence of the highly developed leaf-like stipules. At the summit of the sheath of the leaf of Grasses exists a little membranous scale, connecting the blade with the epidermis of the stem; it is either entire or forked at the top (figs. 59 * & 60*); this structure, called the ligule, is a mere excrescence from the stalk. The stipules of some plants fall off at an early period. This is the case with the interpetiolar stipules of various Rubiaceous plants. It also occurs commonly when the stipules form the outermost envelopes of the leaf-buds, as in Magnoliacese, Ficus elastica, the Beech tree, &c. Small secondary stipules exist at the base of the partial petioles of some compound leaves, especially of LeguminosaB (Desmodium) ; they are called stipels (stipellce). For convenience of description the stipule has been here treated as if it were uniformly of the same nature, varying only in form, position, &c. In point of fact, however, the morphological nature of the stipules varies in different plants : sometimes they represent mere excrescences from the petiole ; at other times they consist of the lower leaflets of a compound leaf (Laihyrus'), or they may be leaves formed on a contracted and rudimentary axillary branch. Lamina. The lamina or blade (b, fig. 54) of the leaf constitutes the most important part of the structure, and exhibits the greatest . variety in its forms, which latter require to be studied in detail, as they often furnish the principal characters for the discrimination of species of Flowering Plants and Ferns. It is ordinarily a flat plate, possessing an upper and lower surface, turned respectively towards the sky and the earth, two margins, a base, and an apex. In plants of succulent habit the thickness of the leaves is often so great that the sides are as broad as the surfaces, or they are more or less confounded in a cylindrical, prismatic, or some similar form (Mesembryan- THE LEAF, 55 themum) ; and similar external forms are presented by the cylindrical or flattened fistular leaves of the Onion, &c. If the blade stands alone upon an undivided petiole, or is sessile on the stem, it is called simple (figs. 54, 55). Where the petiole is branched, and bears more than one distinct blade, the leaf is com- pound (fig. 64), and its separate blades are called leaflets. Both simple leaves and leaflets may be entire that is, the blade may be undivided at its margins ; or it may be more or less deeply incised or lobed. The divisions or branchings of such leaves are analogous to the monopodial branching of the stem (p. 38). Form. The general form of simple and compound leaves, and the character of the subdivisions of the blade of simple leaves and of leaflets, are associated with the plan of arrangement of the ske- leton of the leaf. The solid framework of leaves is composed of woody structures which when large are usually termed ribs (costce), the small divisions being called indifferently nerves or veins. The plan of arrangement of the framework is called the nervation or venation ; the ordinary custom is to call the principal ribs nerves, and the smaller branches veins. When a distinct principal rib, continuous with the petiole, exists, it is called the midrib. The superabundance of terms is an inconvenience here as in many other departments of Botany. Where it is necessary to select, it is advisable to choose those terms which are least objectionable as not involving hypothetical notions of function. Nervation or Venation. The modes of nervation of leaves may be classed under four principal heads : 1. Straight- or parallel-nerved (folia par allelinervia), when (with or without a midrib) the principal ribs run in more or less parallel lines from the base to the summit (fig. 66). 2. Curvinerved (/. curvinervia), when the principal ribs run in curves from the base to the summit (fig. 67), or from the mid- rib to the margin (fig. 68) differing little from the foregoing, but occurring in broader leaves. 3. Palminerved (/. palminervia), when the principal ribs radiate from a point at the base of the leaf (fig. 69). 4. Penninerved (/. penninervia), when the strong midrib gives off the side-ribs at a more or less acute angle, like the blades on the shaft of a feather (figs. 68 & 70). The term triple-nerved (triplinervia) is sometimes used for a modifica- tion of No. 4, approaching to No. 3, when the midrib gives oft' on each side near the base a strong side-rib, wliich runs up within the margin towards the summit. Feather-ribbed (penninerved) and hand-ribbed (pal- minerved) leaves are most common among the Dicotyledons, but they 56 MORPHOLOGY, OR COMPARATIVE ANATOMY. occur also in many Monocotyledons, the former, for example, in many Palms, Musacese, Zingiberacese (fig. 68), &c. ; the latter in the Fan-palms, Fig. 66. Fig. 68. Fig. 67. Fig. 66. A parallel-nerved leaf. Fig. 67. A curvinerved leaf of Gloriosa superba, terminating in a tendril. Fig. 68. A penninerved leaf of Canna, with curved secondary nerves. Smilacese and Dioscoraceae, &c., where there is a transition to a curved- ribbed condition (fig. 67), which, with the straight-ribbed (fig. 66), is most common in the Monocotyledons. Straight-ribbed leaves occur not Fig. 71. Fig. 69. Fig. 70. A palminerved serrate leaf. A penninerved entire leaf with a marginal vein. A subrotund, entire, penninerved leaf. ^infrequently in Dicotyledons, as in Lathyrus, &c. The most important distinction in the ribbing of the two groups is, that in Dicotyledons the THE LEAF. 57 main rib or ribs branch repeatedly at more or less acute angles, and anastomose by their slender twigs, so as to form a netted or reticular framework ; while in most Monocotyledons the branches passing from the main ribs go off nearly at right angles, become suddenly much more slender, and form a kind of square latticed or cancellate framework when they are strongly developed (fig. 76). Forms of Leaves. The general outline of leaves or leaflets is indicated by certain technical terms, such as : circular or orbicular (Hydrocotyle, Tropceolum majus} (fig. 87) ; roundish or subrotund, approaching the fore- Fig. 72. Fig. 73. Fig. 75. Fig. 74. Fig. 72. An elliptical serrate leaf. Fig. 73. An ovate, acute, and dentate leaf; venation arched. Fig. 74. An obovate entire leaf. Fig. 75. An entire lanceolate leaf, edges revolute. going (fig. 71) ; elliptical (fig. 72) ; ovate, egg-shaped with the broad end nearest to the stalk (fig. 73) ; obovate, the same shape, with the narrow Fig. 76. Fig. 77. A hastate leaf. A sagittate leaf. A cordate and abruptly acuminate leaf. 58 MOEPHOLOaY, OR COMPAKATIVE ANATOMY. end nearest to the stalk (fig. 74) ; lanceolate or lance-shaped (fig. 75) ; reniform or kidney-shaped (fig. 79); rhomboidal ; triangular; or the reverse of this, cuneate or wedge-shaped (fig. 88) ; deltoid ; spatulate or spatula-shaped (fig. 80) ; ensiform or sword-shaped (as in the Garden- flag) ; linear, a long narrow form with parallel margins (fig. 81) ; subu- late or awl-shaped, a slender, short linear form soon ending in a point (fig. 82) ; acerose, needle-shaped and rigid (Pines, Juniper, &c.). Fig. 83. Fig. 79. Fig. 79. A reniform crenate leaf. Fig. 81. A linear leaf. Fig. 80. A spathulate leaf. Fig. 82. A subulate leaf. Fig. 83. An obliquely cordate, serrate, and acuminate leaf. Sometimes the forms are intermediate between some of the foregoing, in which case two of the terms are combined, such as ovate-lanceolate, signifying a leaf broader than lanceolate, and with the lower half wider, as in ovate ; linear-lanceolate, a long and narrow lance-shaped blade, and so on. The term oblique is applied to leaves where the portions on either side of the midrib are unequal, as in the Begonias, Lime, Elm, &c. (fig. 83). Base of the Leaf. Special terms are also required to describe the character of the base of the leaf. Thus, sagittate or arrow-shaped (fig. 76) ; hastate or dart-shaped (fig. 77) ; cordate, the shape of a heart on playing- cards, with the broad end nearest to the stalk (fig. 78) ; obcordate, the same shape, with the point attached to the stalk (fig. 108) ; cordate at the base may be added to ovate, elliptical, or other form, where this condition exists ; if a sessile leaf has a cordate base, it becomes auriculate or eared (fig. 84) when the borders are free, amplexicaul or clasping if they adhere to the stem. The last form is a transition to the decurrent state. When the posterior lobes of a sessile leaf extend round the stem com- pletely and become confluent on the other side, the stem appears to run through the leaf, and the leaves are called per foliate (fig. 85) j when the basilar lobes of a pair of opposite leaves cohere on each side, so as to pro- duce a similar condition, the leaves are termed connate (fig. 86). Some- times the blade is gradually narrowed towards the petiole, and becomes attenuated at the base ; when the blade passes still more gradually into a broad- winged stalk, a spatulate form results. Fig. 84. An auriculate leaf. A perfoliate leaf. Connate leaves. Fig. 87. Another character relating to the base is the mode of attachment of the blade to the petiole. Usually the midrib, or set of primary ribs of the blade, is in a direct line with the petiole ; but some- times the ribs, as they pass from the petiole into the blade, separate and radiate horizontally from the top of the stalk, so that the latter appears to be inserted into the back of the leaf ; such a condition is called peltate, and occurs in Tropceolum ma/us and other plants with orbicular leaves (fig. 87). ApeX Of the Leaf. The apex Or point of the leaf A peltate orbicular leaf. has certain characters: it may be acute, or sharp (tig. 66) ; acuminate, or with the point drawn out gradually Fig. 88, (fig. 68), or abruptly (fig. 78) j or mucronate, when it is tipped with a spine (fig. 88). It may also be obtu.se, when an ordi- narily pointed form is suddenly rounded off at the tip ; emar- ginate, when there is a shallow notch where the point should be ; retuse, when a notch of this kind is deep : this last form approaches to the obcordate (fig. 108). Margin of the Leaf. The margins of the leaf are either entire, that is, with an unbroken edge (fig. 71) ; crenate, when they exhibit a series of small rounded teeth or scallops (fig. 79) ; dentate when the teeth are acute and pointed ra- nate leaf, dially (fig. 73) ; serrate, when sharp teeth point towards the apex (fig. 83) ; retroserrate, when sharp teeth point towards the base. If there are coarse teeth, the margins of which are again more finely toothed, as in the Elm, the leaves are doubly serrate (or doubly dentate). Sometimes it is requisite to say, irregularly toothed, or incised, as in many Thistles ; and these teeth, as well as those of regularly dentate or serrate leaves, may be tipped with spines, when they are termed spinose-serrate, &c. When the outline exhibits shallow wavy curves, it is sometimes called repand (figs. 86 & 87). The margin may also be revolute, or rolled back toward the lower face (fig. 75), or involute when rolled round on to the upper surface. Sometimes, through excessive growth of the marginal parenchyma, the edges of the leaf are undulated (as when the edge of a strip of paper swells from being wetted (fig. 95)). 60 MORPHOLOGY, OR COMPAEATIVE ANATOMY. Lobed Leaves. A very large number of simple leaves, and of leaflets of compound leaves, are divided more deeply between the principal ribs; to such the general name of lobed leaves is often applied, and the more or less distinct parts are called lobes; thus we may nave hi lobed (tig. 89), trilobed (tig. 90), and so on, according to the number of the divisions. Fig. t>\ Fig. 93. Fig. 89. A bilobed leaf. Fig. 01. A pinnatifld leaf. Fig. 90. A trilobed leaf. Fig. 92. A pinnatinartite leaf. Fig. 98. A pinnfttipartfte Tyrato !<>nf. But it is found requisite in Descriptive Botany to subdivide lobed leaves into more definite classes ; of these there are two principal types. defined by the character of the ribbini/. Wlu>n the ribs are arrauge'd on the feathered plan, we first take the prefix pinnati- (feathered}, and sub- join to this a word indicating the degree or kind of division, thus : pinna- tifid (feather^cleffy, if the broad notches between the lobes extend from the margin to about halfway between this and the midrib (fig. 91) ; pinnatipartite, if the notches extend nearly to the midrib (tig. 92) ; pinna- tiwt. if the separate lobes are almost free, and merely connected by a narrow strip of parenchyma. Certain less frequent modifications of these forms of the feathered type are conveniently distinguished by technical terms, such as : sinuate, a form either of the pintiatifnl or pinnatiwt leaf, when the excavations and the apices of the lobes are rounded, as in the Fig. 94. Fig. 95. A palmiflil leaf, the nine acute lobes serrated. A p:ilmip:ir(ite letif. the five oblong lobes uudulated. THK LEAF. 61 common Oak-leaf; lyrate, apinnatifid or pinnatipartite leaf, with the end lobe much larger than the ivst (Jig. 5-'>); runcinate, a /yrote or simply pinnated leaf with the points of the lateral lobes turned towards the base, as in the Dandelion. When the incisions are deep, but very irregular in size and form, the term laciniate is sometimes employed. When the ribs have the palmate arrangement, similar terms are sub- joined to the prolix pahni- or palniati-, or palniitid (tig. i>4), palm i sect (tig. iH>). and palmipartite (tig. t>.">\ according to the depth of the divi- sions. A special modification of this type occurs not uuirequently, when the lower or outer ribs, and consequently the basilar lobes, turn back more or less towards the petiole ; such leaves are generally deeply cut ; but the general prolix pedati- may be used in the words pedatifid, pedatisect, or pedatipartite (tig. 97), according to the rule given above. Such leaves may be compared to sympodial ramifications; the central lobe is the primary one from which on either side lobes of the second degree are formed : these produce tertiary lobes, and so on, but always on one side only, as in some forms of definite ramification. Fig. 96. Fig. 97. A ivilmis.vt leaf, the segments oblonR-obovate serrated. A pedatipartite leaf, the segments lanceolate. The bilobed, tt-tlobed, quinquelobed, and similar forms are usually refer- able to the palmate type, and should be more definitely named if they occur in a genus where the leaves exhibit many of these forms, in a con- stant manner ; if the leaves are inconstant in the depth of the divisions, those more general names are preferable. Simple leaves divided on the feathered plan exhibit also more compli- cated conditions. The primary lobes of a pinnately cut leaf may be sub- divided again in the same manner, and the secondary lobes again into ter- tiary lobes. These are named on the same principles, bipinnati-,tripinnati- -fi',1, -mrf, or -partite, according to the degree of division of the last set of io!><;*, i. e. of the secondary lobes ofbipinnatifid (fig. 98) and the tertiary of tripinnatitid. When the leaves are subdivided a fourth fcme, or even where tripinnatitect leaves have JUifonn segmetds, the term dissected is usually employed. It must be borne in mind that the terms above defined are applied in a similar manner to the leaflets of compound leaves, next to be described, being subjoined in description to the terms which define the plan and 62 MORPHOLOGY, OB COMPARATIVE ANATOMY. degree of division of the petiole. They also apply to the bracts, sepals, and all other organs of a leaf-like character. Compound leaves are such as have the petiole branched once or more times before it bears blades ; the branches of the petiole are called partial petioles or petiolules, and are often articulated to the main petiole, which in this case is occasionally termed the racliis. Stipels occur at the bases of some partial petioles. The Fig. 98. Fig. 99. Fig. 100. A bipinnatifid leaf. A paripinnate leaf. An imparipinnate leaf. separate blades of the leaf are called leaflets (folwla), or pinnce. Compound leaves may be classed generally into simply, doubly, Fig. 101. Fig. 103. Fig. 102. Fig. 101. A binate or unijugate pinnate leaf. Fig. 102. A bipinnate leaf, the pinnse unijugate. Fig. 103. A bipinnate leaf, the multijugate pinnae paripinnate. THE LEAF. 63 triply compound or decompound \supradecomposita), according to the number of the successive branchings of the petiole. The rami- fication follows the same types as that of the ribs of simple leaves, and exhibits analogous subordinate modifications. Pinnate leaves are such as have a rachis bearing sessile or stalked lateral leaflets arranged on the feathered plan. Sometimes there is an odd terminal leaflet, when the leaf is unequally or impari-piimate (fig. 100). When there is no end leaflet, the leaf is abruptly or pari-pinnate (fig. 99). Interruptedly pinnate means that the opposite pairs of leaflets are alternately large and small, as in Agrimonia. The pairs of leaflets are sometimes called juga ; and if only one pair exists, the leaf is unijugate (fig. 101) ; if more pairs, multijugate. If the leaflets are not in pairs, but alternate with each other, the leaf is alternipinnate. Fig. 105. Fig. 104. A bipinnate leaf, the pinnae imparipinnate. A tripinnate leaf, the pinnae imparipinnate. Bipinnate leaves are formed when the main petiole bears secondary petioles with distinct leaflets pinnately arranged (figs. 10S-104). Tri- pinnate leaves exhibit an additional (tertiary) series of partial petioles with distinct leaflets (fig. 105). When the division goes beyond the third degree, the leaves are called decompound (fig. 106) ; but it is more common to find bipinnate or tripinnate leaves with their leaflets pinnatifid, -partite, &c. Palmate (or digitate) leaves are such as have a number of distinct leaflets arising from one point, like the ribs of a simple leaf when the plan is palminerved. Si- or tripalmate leaves are very rare (Araliacese). The only modification appears to be the pedate leaf, analogous to the pedatisect simple leaf, but with distinct leaflets (fig. 107). The terms ternate, quinate, and septenate are often applied to palmate leaves with a definite number of leaflets. Ternate leaves, however, may occur either on the palmate (fig. 108) or pinnate plan ; if on the latter, 64 MORPHOLOGY, OR COMPARATIVE ANATOMY. there is only one pair of lateral leaflets and a terminal one, but in these the petiole is ordinarily developed between the pair of leaflets and the Fig. 106. Fig. 107. Pig. 106. A. pinnately decompound leaf. Fig. 107. A pedate leaf. Fig. 108. A ternate leaf with obcordate leaflets. end one. What are called Alternate (fig. 109) and triternate compound leaves are in most cases pinnate leaves with unijugate and terminal leaflets. Such leaves should perhaps be called ternato -pinnate or biternato* pinnate, &c. A modified form, apparently intermediate between pinnate and. palmate leaves, like some ternate leaves, occurs through the suppression of the main rachis of the bipinnate leaves of some Acacias, giving what may be called a palmipinnate form (fig. 110). Fig. 109. Fig. 110. A biternate leaf. A palmipinnate leaf. THE LEAF. 65 The leaflets of compound leaves of Flowering plants are ordinarily called pinnoe, and their subdivisions lobes ; but in the Ferns, where the leaves are highly compound, and the segments somewhat variable in the degree of confluence, the primary divisions of the leaf are called pinnee, the secondary pinnules, and the tertiary lobes or segments. In highly com- pound leaves, the ramification of the petiole and subdivision of the lami- nar structure become less complex toward the apex. Texture. The varieties of texture of ordinary leaves depend chiefly upon their anatomical condition ; but it is requisite to notice here several terms, such as membranous, leathery (or coriace- ous), succulent, &c., used in Descriptive Botany, but which scarcely require explanation. In aquatic plants the leaves are usually of slighter texture : when they Jtoat on water (natant leaves) the forms and general external characters are not much modified ; but when they grow wholly under water (submerged leaves), they are not only more delicate, but are sometimes cut up into fine filiform segments, as in lianunculus aquatilis. Duration. The duration is different in different plants. Those which are unfolded in spring and fall off in autumn are called deciduous. What are called evergreen leaves vary in duration : thus in ordinary evergreens, such as Ivy, Cherry-laurel (Primus Lauro- cerasus), &c., the leaves remain through the winter and fall off only when the new ones are becoming developed in the spring ; while in many Conifers, as in species of Pinus, Araucaria, &c., the leaves remain attached for many years. The anatomical structure of leaves exhibits many interesting modifica- tions, related in some degree to the media and climates in which plants grow. These will be more particularly explained in another place. Surfaces. The surfaces of leaves, like those of herbaceous stems, exhibit a variety of conditions dependent on the character of the epidermal layer. Glabrescent is used to signify that a surface, hairy when young, becomes smooth when the leaf is mature, by the hairs falling off. Some smooth surfaces are shining ; and this is very often the case with the upper surface of evergreen leaves. Hairy surfaces are differently denomi- nated, according to the character of the hairs and their mode of occur- rence. Thus a pilose surface is covered with scattered soft and small hairs, a hirsute with scattered long hairs, a hispid with scattered stiff hairs; while a pubescent surface is covered closely with short soft hairs, a villous closely with longish weak hairs ; and when the hairs are curled and interwoven, the terms silky (sericeus), woolly (lanatus), felted (torncn- tosus), Qijloccose, are applied according to the coarseness of the hairs and the thickness of the coat they form. What may be called the natural smoothness of surfaces may be interfered with by other irregularities analogous in their nature to hairs. Slight, almost invisible rigid projections render the surface scabrous: 66 MOEPHOLOGY, OR COMPARATIVE AKATOMY. hard rigid hair-like processes, called bristles or seta, make the surface setose ; and similar structures still more developed (occurring mostly at the apex and the points of the teeth of leaves), called spines, sometimes occur and produce a spinous surface. Modified, usually compound hairs, containing oily or resinous secretions, are called glandular hairs, rendering a surface viscous or glutinous, which conditions, however, are sometimes produced by glands sunk in the epidermis. The glands are sometimes superficial productions from the epidermis or skin of the leaf, at other times they are outgrowths from the tissue of the leaf itself, as will he described more fully when their structure is considered. Stings are long stiffish hairs containing an irritating fluid. Scaly (lepidotus) surfaces are produced by the occurrence of minute stalked flat scales, analogous in their nature to hairs. Sometimes the cuticular layer of the leaf separates in minute scale-like fragments, giving a scurfy appearance to the surface, which is termed furfuraceous (as in the leaves of the Pine-apple and its allies). The pruinose condition is that which results from the conversion of the cuticle into a thin detachable film of waxy matter, of which the "bloom" of plums, grapes, &c. affords an example. These structures will be more fully described under the head of Minute Anatomy. Characters afforded by Leaves and their Modifications. In Descriptive Botany attention is specially paid to the situation, attachment, duration, direction, arrangement, form (general and of base, apex, margins, surfaces), nervation, colour, texture, &c., as above described and as further illustrated in the section on the mode of describing plants. With the necessary modifications, the same directions apply to the parts of the flower, &c. Special Modifications of the Leaf and its Parts. Under the head of the petiole we have spoken of pliyllodia as blade-like forms of the petiole (figs. 57 & 58). Not only does the leaf-stalk exhibit this and other modifications, disguising its real nature, but the blade also and the stipules are subject to similar modifications, in which the organ or region is only re- cognizable by its position and relations. As these metamorphic structures fall under certain types, which are represented in different cases by all the different regions of the leaf, it is most convenient to describe them under special names. Pitchers (ascidia) are structures of the form indicated by their name, produced by peculiar modes of development of the petiole, the blade, or of both together. One of the best-known examples is found in the Nepenthes, or Pitcher- plants, in which a portion of the leaves exhibit a very long stalk, winged at the base, supporting at the extremity a pitcher-like'sac of ordinary leafy texture, furnished at its mouth with a little flat plate resembling a lid (fig. 111). The pitcher is commonly explained as a kind of phyllode, or MODIFIED LEAVES, ETC. 67 foliaceous petiole, rolled up, and with its margins confluent, the lid-like body being regarded as the lamina ; but it appears -p- -QI more correct to consider the pitcher as the lamina furnished with a distinct terminal lobe (operculum). Sarraccnia, a North-American bog-plant, has analogous pitchers, which are sessile at the base of the flowering stem; Heliamphora (Guiana) has the pitchers less complete, the inner side being slit down as it were for some distance, from the imperfect confluence of the margins of the leaf. In Dischidia Rafflesiana the pit- chers are plainly formed from the blade, and are open at the end next the petiole ; and a similar condition exists in the pitchers formed from the bracts of Marcyrama and Norantea. Somewhat allied to the above, on a small scale, are the utriculi, or sacs of the Utricularite (fig. 112), little bladder-like organs, closed at first by * of JTqwrfi*. a lid, developed from some of the lobes of the leaves of these aquatic plants, and apparently serving as " floats " and as traps for insects. In other aquatics ( Trapa, &c.) floats are formed by inflated petioles, constituting as it were indehiscent pitchers, sur- mounted by ordinary blades. Teratological illustrations of the origin of pitchers are occasionally afforded by garden plants. This has been especially observed in the Tulip, in which the leaf next the flower-stalk has been found with its margins completely confluent into a kind of spathe, which bursts by a transverse fissure to allow the flower to appear. Tendrils (cirri) are thread-like processes, curled spirally, by Fig. 113. Fig. 114. Fig. 112. utriculus or air- sacof Cftrfcictario. Fig. 113. Leaves of.Lafhyru* Aphaca, represented by tendrils, with large foliaceous stipules. Fig. 114. Leaf of Gloriosa superba, prolonged into a tendril. F 2 68 MOEPHOLOGT, OR COMPARATIVE ANATOMY. which weak-stemmed plants attach themselves to foreign bodies. They may be modifications of any part of the leaf or of a branch. In Lathyrus the blade-structure of the leaf is more or less deficient in different species. In L. Apliaca (fi. 113) it is wholly wanting, the petiole running out into a tendril, which may be regarded as consisting either of the leaf-stalk alone, or of this and the midrib of the lamina. In L. odoratus (Sweet Pea) the pinnately compound leaf has one pair of leaflets, and usually one pair of tendrils, and a terminal tendril in the ordinary place of the remaining leaflet. In the edible garden Pea there are several pairs of leaflets, and often several pairs of tendrils, with a terminal one. In Gluriosa superba, a Liliaceous plant, the broad simple lamina runs out into a terminal tendril (fig. 114). In Smilax (fig. 115) the two stipules are represented by a pair of tendrils ; while in the Cucurbitacese one tendril only occurs, which some regard as a stipule, others as a metamorphosed leaf, others, again, as a branch or peduncle. Fig. 116. Fig. 115. -Fig. 115. Tendrils ofSwilax aspera, formed from the stipules. Fig. 116. Leaves and t- ndrils of the Vine. The tendrils of the Vine (tig. 116) are modified flowering branches, originally terminal but displaced during growth so Fi<>-. 117. as to become placed opposite to leaves, and often tuberculated by the existence of abortive flower- buds. The nature of the axillary tendrils of Passion- flowers is similar. Spines (spinai) or thorns are hard, sharp - pointed woody processes, formed, like tendrils, by modification of entire organs or parts of such. Thus in the common Berberry some of the leaves are Represented by compound spines, in the axils of which arise fasciculate groups of leaves. In the False Acacia-tree (Robinia Pseudacaoia) the stipules are represented by a pair of spines at the base of the petiole (fig. 117), while in certain species of Astra ^.-. F galus the petioles are converted into spines after the fall of their leaflets. Base of the leaf of Ho- binia, with stipules de- veloped as spines. MODIFIED LEAVES, ETC. 69 Spinous processes are developed upon the petiole in the upper part of the leaves of certain Palms (Plectocomia), and even on the surfaces of some leaves, as in some varieties of Holly. True spines, however, are more frequently dependencies of the stem : thus in the Gooseberry they are developed from the pulvimis, below the base of the petiole. In the Black-thorn (Prumis spinosa) the spines are real branches (fig. 118), as also are the spines of Gleditschia triacanthos (fig. 119), and the principal spines of Furze (TJlex], in which, however, the points of the leaves are spinous also. Fig. 118. Fig. 119. Fig. 118. Spinous branch of Prumis spinom (Black-thorn). Fig. 119. Spinous branch of Gleditschia triacanthos. Prickles (aculei), properly so called, are sharp woody processes, straight or curved, occurring upon stems, leaf-stalks, at the points or on the margins, or upper surface of leaves. They are distin- guished from true spines by their originating from the epidermis, like hairs, glands, &c., and by having no connexion with the internal woody substance of the stem or ribs of the leaves &c. Glands. This is perhaps the most convenient place to mention the nodular or discoid glandular bodies that occur in connexion with certain leaves, as on the petioles of Passiflora &c. They are distinct in their nature from the epidermal glands before mentioned, and considerable attention has been directed to them on morpho- logical grounds ; hence they will be adverted to again in speaking of the flower. Sect. 5. THE LEAF-BDD. The bud is a compound structure, composed of a solid conical basis, or growing point, supporting a number of rudimentary leaves. In the leaf -bud, or rudiment of a shoot, the conical base represents the future stem, with its internodes as yet undeveloped ; the scales are either entirely rudimentary leaves, or a portion of 70 MORPHOLOGY, OR COMPARATIVE ANATOMY. them on the outside are modified leaf-structures, forming scales for the protection of the inner leaves, and destined to fall off when the bud expands. In the early conditions, the flower-bud is essen- tially analogous to a leaf -bud ; but its ultimate history is different, as will be shown hereafter. Many of the general characters of huds have been described already, under the head of the stem (pp. 34, 35) ; but there are some other more special peculiarities which require separate treatment here ; and repetition of certain more important facts will not be disadvantageous. In all seeds, except those of the few Orders which present an incomplete or acotyledonous embryo, the young plant is possessed, at or soon after the time of germination, of a rudimentary bud, called the plumule, situated at the point of growth of its ascending axis (figs. 120-122). This is the terminal bud of the young ;. 122. Fig. 121. Fig. 120. Monocotyledonous embryo of Potamogeton, cut through perpendicularly : a, radicle ; b, cotyledon ; c, plumule. Fig. 121. Dicotyledonous embryo of the Bean (Faba), with the cotyledons, b' b', separated : a, radicle ; c, plumule. Fig. 122. Diagram of a germinating Dicotyledon, with the plumule or terminal bud between the expanded cotyledons. plant ; and stems and shoots only retain the power of elongating so long as they possess such a bud at their extremity. When it is removed by artificial means, by frost, or, by metamorphosis, is replaced by a flower, the onward growth of the shoot ceases. Axillary buds are the origin of the ramifications of stems. They are developed in the axils of leaves ; and as they unfold into secondary axes, they become the terminal buds of such shoots. Other axillary buds are formed at the nodes of these secondary shoots, to repeat the ramification by developing into tertiary axes according to the type of the species '(see p. 34). Adventitious or accidental buds are those which appear, con- trary to the usual order, at indefinite points, unconnected with the axils of leaves. Generally speaking they are abnormal products, THE LEAF-BUD. 71 presenting themselves under special conditions. They usually occur on organs in a very active state of vitality, subjected to stimulating external conditions, especially where, through natural or artificial operations, there is an absence or insufficiency of normal buds to carry off the developmental energy of the plant or organ. Adventitious buds may be produced from any part of the plant. With regard to those produced on old stems, as in pollarded trees, or those which occur on subterraneous stolons, as in the Rose, Ash, &c., it is not always easy to decide without dissection whether the buds are really adventitious or merely latent axillary buds stimulated into development ; but true ad- ventitious buds do occur. The production of adventitious buds on true roots has been frequently observed, as in Pyrus japonica, Madura auran- tiaca, Paulownia imperialis, &c. ; and the Anemone japonica is commonly propagated by cuttings of the root. The formation of adventitious buds on leaves is a still more remarkable physiological phenomenon. It has been observed chiefly in succulent leaves, but it is not exclusively con- fined to them. When it takes place, the first sign of development is the production of adventitious roots, followed by the formation of a cellular nodule which subsequently assumes the character of a bud. Among natural examples, the leaves of Cardamine pratensis have been observed to form adventitious roots on the lower side when lying upon wet ground, and even to produce buds ; the leaves of several Ferns, such as Woodwar- dia radicans, root at the end, and produce buds which propagate the plant ; and many similar instances might be cited. Artificial production of buds on leaves is now a familiar fact, under the influence of heat and moisture, not only on the scales of bulbs, but on the green leaves or even fragments of the leaves of Bryophyllum, Echeveria, Gloxinia, Gesnera, Hot/a, &c. ; the Orange and the Aucuba japonica may also be propagated by their leaves. Sometimes the leaves produce rootlets alone, and remain stationary without having force enough to develop a bud. The formation of adventitious buds on leaves, especially in Bryophyllum, where a number are often produced, arranged on the margin, is of great interest in connexion with the theories of the structure of ovaries and the origin of the ovules. Bud-scales. The bud which continues the growth from the plumule of a germinating plant (fig. 122), and the axillary buds produced during a season of active growth, are composed of rudi- mentary leaves ; but the winter- or resting buds formed on most deciduous trees and shrubs of temperate climates present the modified foliar organs called bud-scales (perulce}, analogous to the scales of bulbs and other subterraneous buds of herbaceous plants (figs. 123 and 124). Buds without scales are called naked. The scales, when present, are mostly of leathery or membranous texture, and are often clothed more or less densely with hairs, which are sometimes glandular and produce a resinous or glutinous secretion, which exudes when the buds swell. 72 MOEPHOLOGT, OB COMPAEATITE ANATOMY. When winter-buds swell and open, throwing- off their scales, the inter- nodes between the latter do not elongate, while those between the nas- cent leaves do ; consequently the starting-point of each annual period of growth of a branch with an indefinitely developed terminal bud is indicated by a little band of scars marking the place where the scales stood. Fig. 123. Fig. 124. Fig. 123. Section of the end of a shoot of the Horae-chestnut, showing the terminal and two axillary buds ; the terminal bud contains an inflorescence, surrounded by scales and rudimentary leaves. Fig. 124. Bud-scales a, 6, and rudimentary leaves c, d, from the winter-bud ofPrunus Avium. The first two scales of a bud of a dicotyledonous plant, like the two cotyledons of the embryo, usually stand right and left of the axil on which the bud arises ; the succeeding scales assume at once the regular character of arrangement of the leaves of the species. In winter-buds there is commonly a gradual transition from the pure scale to the true leaf (fig. 124), as occurs in bulbs ; and the scales, as in bulbs, are referable chiefly to the vaginal or petiolar portion of the leaf. Bat the scales originate differently in different cases : thus we have petiolar scales, as in the Walnut and Horse-chestnut ; stipidar scales, as in the Vine, Oaks, Elm, Poplars, &c. ; in this case, however, especially in the outer scales, the stipules and the petiole are confluent into one organ (Pmmts, Rosa, &c.) (fig-. 124). Foliaceous scales are formed by the blade of the leaf, of which we have examples in the Lilac, Maples, Conifer, &c. Vernation. The mode in which rudimentary leaves are arranged in leaf-buds is called the vernation, and furnishes important syste- matic characters. Two points have to be regarded here, viz. : 1, the arrangement of the leaves in relation to each other ; and, THE LEAF-BUD. 73 2, the manner in which each separate leaf is folded. The general arrangement is called imbricate or valvate, according as the margins of the leaves overlap one another or simply meet without over- lapping ; but more minute distinctions are observed, and these depend to a great extent on the phyllotaxis of the species. Thus with the 5, -f , or other spiral plan, we have usually triquetrous (fig. 126) or quincuncial (fig. 128) imbricate buds proper ; with alternate ^ or distichous leaves the vernation may be equitant (fig. 125), where each leaf, sharply folded (condn plicate), completely Fig. ]26. Fig. 128. Fig. 125. Sections through Buds, showing their reciprocal vernation. Fig. 125. Imbricated, and equitant (of a Grass). Fig. 126. Imbricated, triquetrous (of a Carex). Fig. 127. Induplicate, decussate (of the Apple). Fig. 128. Imbricated, quincuncial (of a Poplar). embraces its successor (as in the Flag), or Jialf-eqidtant or obvolute, where the leaves are similarly folded, but each leaf embraces only one (lateral) half of the blade of its successor. Valvate buds occur mostly where the leaves are opposite ; a modification of this form exists where the margins of the leaves are rolled inwards (fig. 127), and is called induplicate vernation. The individual leaves Y\*. 129. Fig. 130. Fig. 131. in a bud are either flat^ folded, or rolled. For the first, of course, no special term is requisite. Of the folded leaves we have : reclinate, or inflexed,where the leaf is folded horizon- , -n ., ., . . . tally, SO that the point IS brought down to the base / r 7 7 x 7 7 . (Ltrioclendron) ; condupli- cate (fig. 125), where the leaf is folded perpendicularly at the Sections through leaves showing their individual vernation. Fig . 129 . vernation of a plicate leaf. Fig- 13 - Vernation of a convolute leaf. Fig. 131. Vernation of revolute leaves. 74 MORPHOLOGY, OK COMPARATIVE ANATOMY. midrib and the lateral halves are placed face to face (Oak) ; and plicate (fig. 129), where the blade exhibits several perpendicular folds, as in a fan (Vine, Beech, Maple, Currant, &c.) ; this last is often combined with the preceding. "When rolled up, also, the rolling may take place in either direction : where the apex of the leaf is rolled down toward the base, as in the Ferns and in the flower-stalk of Drosera, it is circinate ; if the leaf is rolled up from side to side like a plan, with only one edge free, as in the Cherry &c., it is convolute (fig. 130) ; when both margins are rolled inward toward the midrib, it is involute (fig. 127) ; and when both margins are rolled outward toward the midrib, it is revolute (fig. 131). Sect. 6. THE INFLORESCENCE. In all Flowering Plants, a portion of the buds change their character at certain periods and in certain situations. They cease to elongate and produce true leaves, while the foliaceous organs of which they are composed are gradually developed into that assem- blage of organs which constitutes a flower. So intimately are the leaf-hud and flower-bud related, that, under peculiar conditions, producing monstrous growths, flower-buds are seen to expand into tufts of green leaves, or imperfect flowers to throw out leafy shoots from their centres ; such cases are often observed, for instance, in cultivated Roses ; and leaf-shoots may likewise exhibit more or less of the characteristics of a flower, &c. Flower-buds are subject to the same laws of arrangement as leaf-buds. The buds which commence the growth of the repro- ductive structures may be at once developed into solitary flowers, or, as is more common, the blossom-buds unfold into a system of branches terminating in flowers, the branches all originating in the axils of modified leaves, called bracts. The solitary flower, or the connected system of flowers arising from one point, is called the inflorescence, which is either terminal or axillary. The inflorescence is produced from the terminal bud, or from this and one or more of the upper axillary buds, in most annual plants ; and there is often a gradual transition from the true-leaf stem into the bract-region, or inflorescence. The same is the case, to a great extent, with the flowering stems of biennials. The inflorescence of herbaceous perennials, bulbs, &c. is either terminal or axillary, as is that of arborescent plants. In the Horse-chestnut (tig. 123) and Lilac, for example, the terminal bud usually ends in a blossom, while in the Apple and its allies the inflo- rescence is axillary. When the inflorescence is developed from the terminal bud of an un- branched stem, the growth of the plant ends in the blossoming, as is the THE INFLORESCENCE. 75 case in the Ac/ave, the Talipot and other Palms, which require a number of years to bring them to the point of flowering, after which they die away, like a bulb with a terminal inflorescence, the plant being some- times propagated at the same time by oftsets from the axils of the lower leaves. The inflorescence of other unbranched Palms, such as the Cocoa- nut, is axillary, and thus may be repeated indefinitely. A flower-bud may be either sessile or stallced ; if the latter, the stalk is called the peduncle. The branches of the peduncle or the slender stalks bearing the individual flowers are called pedicels, and that portion of the main flower-stalk or axis from which the pedicels spring is sometimes called the rachis. Solitary flowers. The simplest forms of inflorescence consist of solitary flowers, either terminal (as in the Tulip), or axillary, when simple peduncles arise from the axils of ordinary leaves (as hi Lysimactda, Nummularia, see also fig. 13, p. 23). The term scape (scapus) is applied to a stem devoid of true leaves, arising underground from the terminal bud or from the axil of a scale or leaf of a rhizome, bulb, &c. It may bear a single flower, as in the Tulip, or a group of flowers, as in the Hyacinth, or a " head " of flowers, as in the .Daisy, Dandelion, c. When solitary flowers arise in the axils of ordinary leaves, the flower- leaf or bract-region of the stem is scarcely represented (fig. 13), or, at least, does not differ from the true-leaf region ; but, generally speaking, those parts of the stem which bear flowers are separated to a certain ex- tent from the true-leaf region, and form a distinct association of parts, representing the bract-region. In the flowering stems of annuals and biennials it is often difficult to draw a line at the boundary of the true- leaf region and the inflorescence, from the leaves passing insensibly into bracts from below upwards, as in the Foxglove. Bracts. The leaves of the flower-leaf region of the stem are called bracts. They are mostly smaller than the leaves preceding them, usually simple, and often scale-like, or glumaceous, consisting of the vaginal portion of the leaf only. In the generality of cases they are green ; but not unf requently they are tinged with the same colours as flowers (as in various Sages), or are even entirely petaloid. In other cases they are membranous, and then often very transient in their existence. The diminutive term bracteole is applied to the small bracts which occur on the pedicels of certain plants, often in pairs. The term bracteole is loosely applied by some authors to the smaller bracts of a compound inflorescence ; but it is much more convenient to use the term bract for all leaves which subtend branches of the inflo- rescence, and to call those scales bracteoles which occur on an ultimate pedicel, as in many Leguminosse. In Monocotyledons there is usually 76 MORPHOLOGY, OB COMPAEATIVE ANATOMY. a single bracteole, while in many Dicotyledons there are two ; in the former case the anterior surface of the bracteole is directed towards the primary axis from which the flower is produced, in the latter the two bracteoles are lateral or oblique to the axis. As a general rule, all ramifications of inflorescence arise in the axils of bracts ; but the bracts are sometimes regularly abor- tive, as in the Cruciferse. On the other hand, we sometimes find the lower part of the inflorescence crowded with bracts with empty axils. Spathe. In many plants the bract subtending the whole inflo- rescence or its principal branches is large, and forms a kind of sheath, called a spathe. Sometimes this surrounds only one flower, as in some Daffodils, &c., where it is of membranous texture ; the membranous spathe of the Onion and its allies encloses a dense inflorescence ; in the Araceae (fig. 133) it is still more developed, and sometimes of petaloid structure, as in the so-called Trumpet- lily (Richardia cethwpica\ w r here it encloses the club-like inflores- cence; while in the Palms (fig. 134) it assumes enormous dimen- sions and a leaf-like or even fibrous texture, forming a sheath to a large and greatly ramified inflorescence. Involucre. In other cases, several bracts are collected together, forming a whorl or densely packed spire, called an involucre. The Umbelliferae have frequently verticillate involucres at the base of the umbels, and sometimes secondary whorls or involucels at the base of the secondary umbels (fig. 140). In the Composite also, where the flowers are crowded on a common receptacle, the bracts form an involucre (figs. 141-146) ; smaller scale-like bracts occur- ring among the florets of these eapitula are called palece (figs. 145 & 146). Other examples of involucre are furnished by the cu pules of the Oak, Beech, Filbert, &c., wherein the bracts are united or not disconnected at the base ; also by the outer glumes or scales of the spikelets of Grasses. Forms of Inflorescence. The different forms of the Inflo- rescence are divisible into two classes : 1, the indefinite, where the terminal bud of the main or primary axis does not form a flower, the flowers being borne on secondary lateral branches, which are as a rule smaller and weaker than the main axis ; and, 2, the definite, where the primary axes either bear terminal flower- buds, while the succeeding flowers spring from secondary axillary branches produced lower down, and subsequently to the terminal bud, or branch in a forked manner without producing a flower in the centre of the fork. The secondary branches are here as strong or stronger than the main axis. The forking is not neces- THE INFLORESCENCE. 77 sarily a true dichotomy, but may apparently be so owing to the abortion of the terminal bud. Examples of the indefinite form are seen in the Ouciferse, especially the Wallflower, where a few flowers at first appear in a tuft, while the seed-vessels are afterwards wide apart on an elongated raceme, the upper- most being the youngest. In the Foxglove and similar plants we may produce a very long development of the indefinite structure by picking off the low r er flowers as they wither, when, as no seed is formed, the in- definite terminal bud retains its energy, and continues to lengthen until the plant is exhausted. On the other hand we observe, in the Sweet- William, the Elder, and the Hydrangea, the centre flower of a tuft opens first, and the definite inflorescence becomes wider and wider, but never elongates or Arrows out in the centre. Fig. 132. Fig. 134. Fig. 135. Fig. 133. Fig. 132. Spike of Verbena afflcinalis. Fig. 133. Spadix and spathe of Calla. Fig. 134. Compound spadix and spathe of a Pa]m. Fig. 135. Compound spike, with spikelets, ofJLolium, When an indefinite inflorescence is elongated the lowermost flowers open first, while if it be of a flat-topped or crowded character, the outermost flowers open first and the central ones last, as in the capitula of the Compositse. Hence the indefinite forms of inflorescence are sometimes called centripetal or progressive, and the definite centrifugal or regressive. There is an exception to the ordinary regularity in the capitula of Dipsacus (Teazel), where the florets open first halfway up ; and then proceed both centiipetally and centrifugally. 78 MORPHOLOGY, OE COMPARATIVE ANATOMY. Fig. 136. Forms of Indefinite Inflorescence. Of the Indefinite Inflores- cence the following are the most important forms : the spike, the raceme, the corymb, the umbel, and the capitulum. Spike. The spike is a long simple axis or rachis bearing sessile flowers, either standing at intervals, as in the Vervain (fig. 132), or crowded, as in the common Plantain and many Sedges. Several modifications of the spike have distinct names. When the rachis hears large, persistent, imbricated bract-scales, it forms a cone or strobile, as in the Firs and Pines. When it is thick and fleshy, with the flowers more or less imbedded in it, the term spadix is applied, of which the Araceae furnish examples (fig. 133) j the same term is con- veniently retained when this fleshy axis is branched, as in the Palms (fig. 134). The so-called spikes of many Grasses, such as Wheat, Barley, Rye-grass (fig. 135), Cat's- tail-g'rass, c., are also compound spikes, since in place of single flowers the rachis bears spikelets or short axes with several sessile flowers. The term catkin (amentum) is applied to the pendent, often caducous, spike-like inflorescence of the Willow, Poplar, Birch (fig. 136), and the male in- florescence of the Oak, Filbert, Chestnut, &c. j in these the bracts have sometimes one, sometimes several flowers in their axils. The flowers in catkins are usually unisexual. Male and female catkins of the Birch. Raceme. The raceme differs from the spike in having the flowers distinctly stalked, the main rachis being unbranched, as in the Hyacinth, &c. Corymb. The corymb is formed when the flowers originate as in the raceme, but the lower ones are raised on longer stalks than the upper ones, so as to bring them all nearly on a level, as in Ornithogalum (fig. 137), &c. As already noticed, a corymbose inflorescence sometimes grows out into a raceme while the fruits are ripening, as is seen in many Crucifene. The relation between the two forms, or, more properly, between the panicled and the corymbose state of the same inflorescence, is well seen in comparing a Cauliflower as fit for the table with the expanded in- florescence of the same plant when allowed to run to seed. Panicle. A panicle is formed when the main rachis is more or less branched ; it is hence a series of racemes on -a branched rachis. The term panicled is often used in a general sense, to signify a much-branched inflorescence, whether definite or indefinite. THE INFLORESCENCE. 79 Fig. 137. Corymb of Ornithogalum. Panicled cyme of Alisma Plantago. Fig. 140. Umbellate inflorescence of Butomus umbellatus. Compound umbel of the Carrot. Umbel. The umbel is formed by a number of single flowers borne on long stalks of nearly equal length arising from one point, as in the common Cherry, the Cowslip, &c. In the family of Um- belliferae, so called from the prevalence of this inflorescence, the umbels are mostly compound (fig. 140) ; that is, the first set of peduncles do not- bear flowers, but secondary sets of radiating branches, forming umbellules, or secondary umbels. Inflorescences of this general character are termed umbellate even when definite. 80 MORPHOLOGY, OR COMPARATIVE ANATOMY. Umbels usually have an involucre at the base of the radii, as noted above. The simple umbels of the Onion group are originally enclosed in a membranous spathe. Capitulum or Head, The capitulum is mostly formed by the rachis expanding into a thickened mass, surrounded by an involucre of overlapping bracts, presenting a convex, flat, or concave surface (common receptacle), upon which are crowded a great number of sessile flowers, as in the families of Composite and Dipsaceae (figs. 141-146). In the Composite there are often little mem- Fig. 141. Fig. 142. Fig. 143. Fig. 144. A Fig. 141. Capitulum of Scabioaa. Fig. 142, Vertical section of the capitulum of Scablosa. Fig. 143. Receptacle of the Daisy with the florets removed. Fig. 144. Receptacle of Dandelion with the florets removed ; bracts of the involucre reflexed. Fig. 146. Fig. 145. Fig. 145. Section of a capitulum of a Composite plant with palese at.the base of the central tubular and of the marginal ligulate florets. Fig. 146. Section of an empty capitulum of a Composite plant with a paleaceous receptacle. branous bracts (palzce) at the outside of each flower (figs. 145, 146) ; in the Dipsaceae each flower is surrounded by a cup-like involucel (fig. 142). The flowers crowded together in the capitula of Composite are small and of various forms, so arranged as to give the whole the outward aspect of a single flower ; hence this inflorescence was formerly called a compound Jloicer, and its involucre a common cahjx. THE INFLOBESCENCE. 81 The flowers in the capitula of the Composite are called florets', and different names are applied to this inflorescence, according to the mode of arrangement of the florets. In the Daisy, we observe a yellow middle disk and a white or pinkish ray ; the disk is com- posed of florets different in character from the spreading florets of the ray (fig. 145). Some capital* are wholly discoid, such as those of Groundsel (Senecio vulgaris), of Thistle, &c. ; others are wholly radiant, such as those of the Dandelion, Lettuce, &c. It should be observed that cultivation tends to convert tubular florets into spreading ones, and so to obliterate the yellow disk or " eye," as we observe in the Dahlia., garden Daisy, &c. Capitula of less marked character are found in other families, where, however, the involucre is wanting; for example, the flowers of Clover (TrifoUum) have a capitular arrangement, as also those of many Proteaceous plants (Banksia). In the Fig the peduncle or common receptacle is fleshy and excavated (fig. 147), the flowers being inside and developed centrifugally ; in Dorstenia (fig. 148) the receptacle is flat or slightly concave on the top, while in Artocarpus and other cases the flowers are on the outside of a convex peduncle. These forms of inflorescence are only slight modifications of the capitulum. Such inflorescences must not be confounded with the concave top of the flower-stalk enclosing the carpels of a single flower, as in the Rose. Fig. 147. Fig. 149. Fig. 148. ff 147. Inflorescence of the Fig; the flowers inside the excavated fleshy receptacle. Fie. 148. Inflorescence of Dorstenia; the flowers imbedded in.the fleshy receptacle. Fig! 149. Compound umbellate spike inflorescence of Digitaria. Forms of Definite Inflorescence. The forms of definite inflores- cence are also termed cymose, the term cyme (fig. 150) being very general in its application ; for it is used in reference to a 82 MORPHOLOGY, OR COMPARATIVE ANATOMY. number of forms more or less resembling outwardly the raceme, corymb, and others of the indefinite type, but all agreeing in Fig. 150. Fig. 151. Dichasium or dichasial cyme of Cerastium. Scorpioid cyme of Myosotis p alustris. producing a primary terminal flower on each shoot, and con- tinuing the subsequent evolution by secondary axillary develop- ment, the development of the lateral shoots being thus more vigor- ous than that of the primary shoot. The loose cymose inflorescence of many Caryophyllaceae illustrates the definite mode of growth very clearly ; the primary axis terminates in a flower (tigs. 150, 152), then branches arise in the axils of a pair of bracts lower down ; these branches repeat the process, and their branches again, until the flowering shoot is exhausted. Cymose inflorescences admit of division into two principal groups, according as they are monopodial or sympodial (see ante, p. 39). Monopodial Cymes. Each branch of the inflorescence is here terminated by a primary flower (fig. 152, i), below which are deve- loped two or more secondary flower-stalks, one on each side, and each in its turn surmounted by a flower (fig. 152, n, in, iv). The simplest form of this is the dichasium (figs. 150, 152), the cyme bipare of the French. There is no true dichotomy in such instances, the appearance of such being due to the superior development of the side branches as compared with that of the terminal one. Sympodial Cymes. These may be called unilateral, as in them the secondary branches of the same degree are developed on one side THE INFLOEESCENCE. 83 only : thus the primary flower-stalk or axis ends in a flower ; beneath this arise not two branches, one on either side, as in a dichasium, but one only, this one being terminated by a flower like the primary branch and giving off a tertiary branch as before (fig. 153). The flower-stalks here appear to be opposite to the Fig. 152. Fig. 153. irm Fig. 154. IT] "IT HFJff W o Figs. 152-154. Diagrams illustrating the centrifugal development of cymose inflorescences. Fig. 152 a globose dichasial cyme ; fig. 153 a sympodial scorpioid cyme, the dotted lines indicate the suppressed branches ; fig, 154 a corymbose cyme. One of the lateral branches at III is abortive. bracts ; but the bract in this case belongs not to the flower-stalk immediately opposite to it, which is a primary formation, but to the secondary flower-stalk which springs from its axil. The subsidiary flower-stalks are sometimes developed all on the same side when the inflorescence becomes curled from the greater growth on one side than on the other. Such cymes are called scorpioid cymes (fig. 151). At other times the subsidiary pedicels or flower-stalks are de- veloped alternately, first on one side and then on the other, when the in- florescence has a zigzag shape. When the main rachis is a sympode (p. 39), and the flowers, instead of being all on one or on two opposite sides, are dis- posed spirally, the term helicoid cyme is given. In these forms of cyme one of a pair of peduncles is generally systematically suppressed, and this happens successively on one side of the main rachis of the inflorescence, or, 84 MORPHOLOGY, OR COMPARATIVE ANATOMY. as has been said, alternately, now on this side, now on that. This main rachis is therefore not formed by one continuously growing shoot, but by a succession of shoots of different generations placed one over the other in definite order, thus forming a sympode (see ante, p. 39). In this manner we may have spicate or racemose sympodial cymes closely resembling, on a superficial inspection, spikes or racemes. If the bracts are present the true nature of the inflorescence is apparent, because in that case the pe- duncles are on the opposite side of the axis to the bracts, as \nHelianthemiim. It often happens, however, in these cases that the bracts are wholly wanting, as in Boraginaceae, in which the scorpioid cyme has been attri- buted to repeated forking of the growing point ; but the sympodial theory is the more probable. Forms of Cymes. The form of the cyme is sometimes further indicated by such terms as a globose cyme, a linear cyme, and so on. When the flowers are nearly sessile, forming a dense flat- topped bunch, such as we see in the Sweet- William and other species of Dianthus, the term fasciculus is sometimes used. Where a cymose tuft of only a few flowers, crowded together in this way, occurs in the axil of an ordinary leaf, the inflorescence is sometimes called a ylomerulus, as in many of the Labiatse. Compound Inflorescence. Some plants, especially herbaceous perennials, have compound inflorescence, wherein the flowering region of the stem appears to be composed of a number of distinct inflores- cences arranged on a regular plan. The plan of the ramification of the main axis mav be the same as that of the individual inflorescence, as in the Umbelliferse, where both the primary and the secondary umbels unfold centripetally ; sometimes the separate inflorescences are arranged in a different form belonging to the same class, as in the case of the umbellate collection of spikes in certain Grasses (Digitaria, fig. 149), &c. Mixed Inflorescence. In other cases there is a mixed condition, since in many Composite the individual capitula are centripetally developed, while they succeed one another on the main stem in a centrifugal or cymose order ; in the Labiate the cymose axillary glornerules (which, occurring opposite to each other, form verticil- lasters or false whorls) are developed from below upwards, the main stem being indefinite, and they are often crowded together above so as to form a kind of compound spike. The general facts of the morphology of the different forms of inflo- rescence are thus seen to be conformable to the laws ruling the develop- ment and ramification of the stem, as already explained. The different modes of inflorescences often pass one into the other, and .such inflorescence as scorpioid cymes may originate either in the manner above described, or, very rarely, by direct forking of the growing point [Warming]. The difference between a dichotomy of the growing point THE INFLORESCENCE. 85 and lateral ramification is not fundamental j and, again, where true dicho- tomy exists it is rare for the two divisions to be developed in the same manner. In some scorpioid cymes one division "becomes a flower-bud, the other repeats the ramification of the axis. Modifications of the Inflorescence. In certain cases we have the normal condition of the inflorescence greatly disguised, as in folictceous peduncles, and in cases of what is called fasciation, as also where the flower-stalks are apparently removed from their usual place by adhesion of various kinds and degrees. Fig. 156. Fig. 155. Fig. 155. Foliaceous peduncles of Ruscu* avuleaius. Fig. 156. Foliaceous flowering branch of Xylophylla. In many kinds of Cactus, as already noticed (p. 38), the stem assumes more or less the outward aspect of a leaf; and when a flower springs from such a stem, it looks like an abnormal growth ; but it is really produced from the terminal or axillary bud of an al or';ive branch. In the Butchers-broom (Ituscus, fig. 155) the single branches or pe- duncles are flat leaf-like plates, and bear the flowers in the axils of little scales or reduced leaves which arise on the upper surface, seemingly from tho midrib of a leaf ; but these foliaceous pedun- cles grow from the axils of scale- like leaves (fig. 155 *). In XylopTiylla (fig. 156) we find a compound foliaceous peduncle, consisting of a large leaf-like branch bearing numerous flowers on its margins, arising there in the axils of bracts. Fasciation is usually an abnormal condition, consisting of the develop- ment of a large number of buds in close approximation, and the conse- quent congenital fusion of a number of peduncles (or in some cases leafy shoots) into a solid mass, bearing the flowers on the borders. It produces the crest-like condition of the flower-stalk of the garden Cockscomb j and converts a paniculate inflorescence into a ribbon-like axis. Adhesion, or want of separation of the peduncle from the leaf or bract, produces an appearance as if the flower sprang from the latter, as in the case of the Lime-tree. A similar union or, rather, lack of separation between the flower-stalk and the branch, the former being in such cases often raised above its normal level by the growth of the latter, produces extraaxillary inflorescence, as in some species of Solanum. Where the inflorescence is placed opposite to a leaf, as in the case of the Vine, &c., the inflorescence is in reality terminal (as may readily be seen in the young state) ; but as growth goes on it bends downwards into nearly a horizontal position, while the axillary bud next beneath it deve- 86 MORPHOLOGY, OE COMPARATIVE ANATOMY. lops into a shoot which assumes a vertical direction, thus occupying the position of the inflorescence. Such branches are called by French botanists usurping branches. In a few cases absolute partition of the growing point has been observed one division forming a tendril or an inflorescence, the other forming a new vegetative axis, as in Vitis vulpina observed by Warming. Duration. The inflorescence, like the leaf, varies in its duration. The staminal catkins of the Amentaceae, such as the Oak, Hazel, Poplar, &c., fall off as soon as the pollen is discharged from the stamens, and they are called caducous. In many cases the inflo- rescence, or the individual peduncles, separate by a disarticulation when the fruit is ripe, as in the Apple, Cherry, &c. ; the term de- ciduous is then applied. In the Rose we observe the dried-up fruit long remaining, like the cones of Firs, &c., after the seeds have become matured ; these are persistent. Sometimes the peduncles undergo expansion during the ripening of the seeds, so as to form part of the fruit ; such an inflorescence or peduncle is called ex- crescent. The Fig, the Pine-apple, and other fruits are formed of excrescent inflorescences; the Cashew-nut (Anacardium) has an excrescent peduncle. Characters afforded by the Inflorescence. For descriptive pur- poses the inflorescence must be treated as the ramifications of the stem, noting also the number of the flowers, their mode of expansion, and other peculiarities as explained in the foregoing sections. Sect. 7. THE FLOWEE. The Flower, the characteristic reproductive apparatus of the higher plants, consists of no new elements superadded to the fun- damental organs of the vegetative regions, but is merely an assem- blage of these organs modified in certain essential particulars so as to fit them for exercising new functions. A flower is a modified shoot, in which the internodes of the stem are seldom developed ; while the leaves, arranged according to the general phyllotactic laws, are more or less different in form and texture, and have part of their tissues developed into more highly specialized products, dis- tinguished both in anatomical and physiological characters from those associated with vegetative leaves. The theory of the construction of the flower rests upon proofs derived from various sources, such as teratology, or the study of exceptional growths. The strongest confirmation of the views arising out of the ob- servation of such cases is obtained by comparative morphology, by the in- ternal structure, and by the investigation of progressive development, or u or- ganoyeny" which latter supplies a clue to the original ancestral form. THE FLOWEB. 87 We may, in the first place, remark upon what is taught by the study of development. Flowers are common in which the organs stand in regular circles, and in which the organs of each circle agree in colour, size, and so on; but in many cases we find deviation from this regularity: the arrangement of the organs becomes changed, and the parts of parti- cular circles become more or less different among themselves as, for ex- ample, in the flowers of the Pea-tribe, of Labiatse, &c. But when we examine the buds of these flowers in a very young state, we often, but not always, find the rudimentary organs regularly arranged, and, while in the state of cellular papillaB, agreeing exactly in all external characters. The subsequent irregularity is a result of special growth, for a special purpose, at a later epoch. In didynamous stamens, for example, the longer pair do not exceed the others until a late period of their develop- ment. Transitional Forms. The original uniformity and homogeneity of the organs of flowers are not always so completely lost in the maturation of the structures, that the different secondary types of organs, sepals, petals, &c. become entirely distinct. The study of comparative morpho- logy reveals many cases of transition from one kind of organ to another, illustrating, in a very interesting manner, the doctrines of morphology. In Calycanthusjloridus and the Camellia the numerous pieces of the floral envelopes present a spiral arrangement, and it is impossible to find a distinct line of demarcation between the bracts, the calyx, and the corolla. In species of Cornus and Euphorbia, the coloured bracts of the involucre assume quite the aspect of a coloured calyx or corolla. In the White Water-lily (Nympheea), a transition between sepals and petals is seen in the segments of the calyx, which are green outside and petaloid internally, while we have perfectly petaloid sepals in many flowers, as in Aconites, Larkspurs, &c., and particularly in the showy bulbous Mono- cotyledons commonly cultivated, e. g. the Lily (Lilium), Tulip, Crocus, &c. In the Water-lily (Nymphaa) we observe a gradual transition between petals and stamens, the latter appearing first as petaLoid plates, with anther- structure on the edges. In Canna it is the ordinary rule for the stamen to be a kind of petal bearing an anther-lobe on one upper edge. A more or less expanded petaloid state of the filament is not unusual, and in the Mistletoe the stamens are flat, leafy organs, with the pollen developed in the parenchyma of the inner face. The stamens and pistils being so diametrically opposed in their physio- logical characters, we naturally do not expect to find any transition between these organs in normal flowers, though in monstrous develop- ments such transitions are frequent. Teratology. The study of Teratology, the interpretation of exceptional growths by reference to laws of development more or less interfered with by external agency, is very instructive in regard to Morphology. In the exceptional products of nature or, still more, of art, we find illustrations of almost every possible kind of the general proposition above mentioned. Phyllody. Cases are not unfrequently observed where the entire flower is replaced by a fascicle of green leaves, especially in the Alpine Strawberry. In wet seasons it is not uncommon to find flowers of the 88 HOEPHOLOGY, OE COMPAEATIYE ANATOMY. White Clover with more or fewer of the organs modified in this way, the pistil, one or more of the stamens, &c. appearing- in the form of green leaves, occasionally compound and ternate, as on the stem below. In the Double Cherry of gardens, the place of the pistil is often occupied by a pair of green leaves ; in the Fraxinella a circle of green leaves has been observed in the place of the ovary. Substitution and Metamorphoses. Almost all polypetalous flowers, and many gamopetalous, are capable of being " doubled by cultivation, that is to say, the number of petals maybe increased at the expense of the stamens, or of these and the pistils. For example, the Wild Rose has bat live petals, and many stamens and pistils, but in our garden Roses the numerous stamens and pistils are often altogether replaced by petals. In many cases intermediately formed structures exist in such double flowers : in the double early Tulip, for example, we almost always find monstrous organs, half-petal and half-stamen, and even half-stamen and half-carpel ; the same may be observed in double Pinks and Carnations. The ovules have been seen bearing pollen, while it is frequent to find the stamens bearing ovules. Illustrations obtained in this way might be multiplied ad itifinitum. It should be observed, however, that in double flowers we frequently find not only all the essential organs replaced by petals, but an actual multiplication of the natural number of organs, as in Roses, Camellias, double Daffodils, &c. Prolification, In the last place, we may advert to the phenomena of the abnormal evolution of buds within the limits of flowers. Cultivated Roses sometimes send out a leafy shoot from the centre (prolification), the terminal bud not becoming arrested as is natural; on Apples and Pears we occasionally see one or two leaves growing out from the summit, from the same cause. In addition to this, the organs of the flower may assert their foliar nature by producing flower-buds in their axils, like stem-leaves. This has been observed in the case of the petals of Celastrus scandens, and also of Clarkia elegans, and occurs sometimes in garden Roses*. These general observations will serve to show the essential homology of all the lateral organs of flowering plants with ordinary leaves, and more especially with the vaginal or leaf-scale portion of the leaves. The laws under which varieties of form &c. are produced within the limits of the flower all substantiate the same general principles. Parts of the Flower. The parts of flowers are : the perianth, consisting of (1) the sepals, forming the calyx, (2) the petals, forming the corolla, and enclosing (3) the stamens, forming the androecium, and (4) the carpels, forming the pistil orgyncecium. That portion of the peduncle from which all these organs spring is called the receptacle or thalamus; it seldom, has the internodes much developed, but is more or less expanded horizontally. It is sometimes convex or conical and elongated, and sometimes concave. AVhen it forms a flattened * A general review of these abnormal or unusual formations, and of the inferences that may be derived from them, is given in Dr. Masters' ' Vegetable Teratology,' published by the Eay Society. THE FLOWEE. 89 Fig. 157. surface above, its centre corresponds, of course, to the apex ; and we may thus say that the above-named organs succeed each other from without inwards, or from below upwards. The accompanying diagram of the floral whorls (fig. 157) illustrates the theoretical con- struction of a perfect and symmetrical flower. Here the internodes are imagined to be deve- loped between the separate circles of the flower an arrangement which does occasionally occur in nature, as in Capparids, Passion-flowers, &c. Anterior and Posterior portions of the Flower. All axillary flowers arise in the angle between a bract or leaf and the stem ; from this is taken the rule as to the relative position of organs in describing flowers. The side of the flower next the stem is the upper or posterior part, that next the bract the anterior or lower ; and in the dia- grams or ground-plans used to represent the construction of flowers, it is impor- tant to mark the places of the axis and the bract, the former being represented behind by a O? the latter in front by an X Or ' . ', as in fig. 160. Where flowers are solitary and terminal there is no proper back and front ; but in plans of these, the position of the last leaf or bract, and specially of the bracteoles, should be shown. If, with a flower of four sepals, there is a pair of bracteoles, the two lowermost sepals are antero-posterior (fig. 167, p. 96) ; but if there are two pairs of bractlets, the two uppermost sepals are antero-posterior. When bracts are suppressed, as in the Cruciferce, the position of the floral organs may be determined by their relation to the parent stem. Arrangement of Parts. The parts of flowers being phyllomes, their arrangement corresponds to that of stem-leaves. [Sometimes they are truly whorled, while at other times, especially in the calyx and corolla, they are arranged in spiral cycles, and are developed successively on the ^ or -f plan, but reduced into apparent whorls by the absence of internodes. Such flowers are called acyclic-, and where some of the parts of the flower are arranged spirally and others in a verticillate manner, the term hemicydic is given. In such a calyx as that of the Kose, the sepals are imbricated on the f plan (figs. 158-160). In the ternary floral envelopes of many Monocotyledons we find illustrations of the type. Sometimes the spiral parated by internodes. 90 MORPHOLOGY, OR COMPARATIVE ANATOMY. arrangement is still more evident, especially where there exist great num- bers of a particular kind of organ, as in the mixed petals and stamens of Nymph&a, and the multiple pistils of Ranunculus, Magnolia, &c. 3n Caly- canthus all the organs follow on in a continuous spiral. In other cases the floral organs are developed simultaneously, when a true whorl is produced. Fig. 158. Fig. 159. Fig. 158. Calyx of the Rose ; the numbers indicate the sequence of the sepals from without inwards, or from below upwards. Fig. 159. Section of the calyx of the Rose; the numbers as in the preceding figure. Number of Parts. According to the number of parts in a cycle or apparent whorl, these are distinguished as dimerous or binary, Fig. 161. Fig. 160. Diagram of the $ spiral arrangement of the parts of the flower with bract and lateral bracteoles; O * ne situation of the axis. Fig. 161. Diagram or ground-plan of the 3-merous flower of the Tulip. THE FLOWER. 91 trimerous or ternary (fig. 161), tetramerous or quaternary, and pen- tamerous or quinary (fig. 162). The ternary arrangement is by far the most common in the Monocotyledons, the quinary in the Dico- tyledons. Most frequently the calyx and corolla have Fig. 162. an equal number of parts; the relative num- ber of organs is prone to increase in the stami- nal circles, and still more frequently to dimin- ish in the carpellary whorl. Alternation or Superposition. In the majority of cases we find the organs of each successive whorl developed alternately with, and not super- or anteposed to, those of the preceding circle. From this the whorls would appear to re- semble the decussating whorls of true leaves, rather than regularly succeeding spiral cycles. We have seen that these decussating whorls are closely related to the spiral cycles (p. 48). Moreover we find in the very numerous cases of flowers with the organs imbricated in the bud, that the spiral arrangement is very evident, and the whorled appearance presents itself only after the expansion of the flower. Now, if the or f cycles succeeded regularly, the organs of successive cycles should be superposed and not alternate, as indeed they sometimes are, e. g. Sabia. A. de Jussieu has supposed that the organs are arranged on the spiral T 5 type in all trimerous and penta- merous flowers with imbricated aestivation. Inspection of the diagrams in a former page (45) will show with how little displacement the organs of such flowers may be arranged on this type ; and there is much proba- bilitv that the alternation of spirally arranged cycles results from some such" cause, while the alternation of organs in flowers with valvate aesti- vation is referable to the same laws as the decussation of whorls of leaves. The exceptional case of opposition of organs will be explained presently. Typical Flower. The typical flower in the diagrams (figs. 157, 162) consists of four circles of organs equal in size and number of parts, and with the parts regularly alternating. A flower thus pre- senting all the whorls is called complete or eucyclic ; the organs in each circle being similar, it is regular and the number of organs in each circle being the same, it is moreover isomerous. Modifications. Almost every kind of deviation and combination of deviations from this type are met with ; but the modifications in the number, arrangement, and form of whorls or parts are refer- able to distinct causes, such as: 1. Alteration of the number of circles, or of the number of organs in the circles ; this may arise either from multiplication, ctiorisis, enation, or interposition, or from suppression or abortion of parts. 2. Union of the organs ; this 92 MOEPHOLOGT, OR COMPAKATIYE ANATOMY. may be merely coalescence of the margins of organs of the same whorls (cohesion), or confluence of normally distinct whorls (ad- hesion). These so-called unions are generally the consequence of arrest of development, owing to which, parts usually separate in the adult condition remain inseparate. 3. Unequal growth or degree of adhesion in the organs of particular whorls, producing irregularity. 4. Irregular growth either of the receptacle, or pro- duction of outgrowths from various organs by enation. 5. (Sub- stitution of one organ by another (metamorphosis). 6. Superposi- tion, where parts usually alternate are placed opposite, or, more correctly, are superposed the one to the other. Dr. A. Gray has furnished an interesting illustration of these laws of modification, from a family (Crassulaceae) in which different kinds of deviation occur together with examples of very symmetrical flowers. In Crassula (fig. 162) is found a symmetrical pentamerous flower, with five sepals, five petals, five stamens, and five pistils, all regularly alternating, and only slightly confluent at the base. In Tillcca some species have four, some only three organs in each whorl, but the flowers are still regular and symmetrical. In iSedum (Stonecrops, &c.) the flowers of some species are pentamerous, those of others tetramerous ; but here the number of sta- mens is doubled by the introduction of an entirely new circle of these organs (multiplication). Rochea has the margins of its petals slightly coherent, while in Grammanthes the petals and sepals are respectively coherent more than halfway up. Cotyledon has coherent envelopes, and a double series (multiplication) of stamens as in Sedum, to which is added an ad- herence of the stamens to the tube of the corolla. In Penthorum the five styles are coherent firmly together below, while in some cases its petals are suppressed. In Sempervivum (Houseleek) the number of sepals, petals, and pistils varies in different species from six to twenty, and the stamens from twelve to forty. Pleiotaxy, or multiplication of the number of whorls, is very common, especially as regards the stamens. In the trimerous flowers of Liliacea3 and AmaryllidacesB there are six stamens stand- ing in two circles of three. In the Poppy family the tetramerous circles are still more multiplied ; and in the Kose, Buttercup, &c. we have further examples. When the number exceeds three or four circles of one kind of organ, the organs are said to be indefinite in number, and the verticillate arrangement becomes very indistinct in the opened flower. In the White Water-lily (Nymphcea) we have multiplication both of petaline and staminal circles ; and in Magnolia, Ranunculus, &c. the pistils are much multiplied, exhibit- ing in these a distinctly spiral arrangement. Multiplication of circles occurs abnormally in the double flowers of gardens, in which we often find far more organs than exist in the normal state, as in Daffodils and other flowers where the organs are naturally few THE 1'LOWEE. 93 in number. The multiplication in this case is often due to transverse chorisis, the parts being superposed to each other. Each part so affected divides in a direction parallel to its surfaces into two or more parts. If the supernumerary part is an outgrowth from an already formed organ it is said to be formed by enation. Pleiomery, or multiplication of the organs in particular whorls, occurs in a number of flowers, and depends on different causes. Sometimes the multiplication is effected by collateral chorisis, or divi- sion at right angles to the surfaces, a pair of stamens, for example, standing in place of one ; in other cases the organ is divided parallel with the surfaces into an inner and outer part or into a fasciculus of organs. The cases of collateral chorisis are explained by the circum- stance that the staminal leaf, in these cases, as in an ordinary lobed or compound stem-leaf, becomes subdivided and forms a lobed or compound stamen. In some flowers (as in many Ericaceae) there are ten stamens in one whorl, while the sepals, petals, and carpels are pentamerous ; in these cases the five additional stamens are formed subsequently to the others. This mode of multiplication of parts is called interposition. Suppression, Abortion. In describing the phenomena of dimi- nution of the number of circles or organs of flowers, it is convenient to distinguish between suppression or total absence, and abortion or partial absence, when the organs are represented by imperfect or rudimentary structures. A complete flower possesses a calyx and a corolla ; the corolla, and even the calyx also, are wanting in some flowers, which are termed incomplete ; when the corolla alone is wanting, the flower is apetalous:, the term naked is occasionally applied to flowers without any floral envelopes. The term dichlamydeous, having calyx and corolla, monochlamydeous, having calyx alone, and achlamydeous, destitute of floral envelopes, are used by some systematic botanists in place of the above. These conditions are not very secure bases for systematic divisions, since it is not uncommon to find apetalous plants in Orders having ordinarily complete flowers, as in the Oaryophyllaceae (Sayina, &c.) : the apetalous condition, however, is constant in a large number of Orders, and familiar examples occur in the Nettle family, the Chenopodiaceae, the Amaranths, &c. Achlamy- deous flowers occur in the "Willows, Cattitriche, &c. Some flowers, then, are incomplete by abortion, in which case they are degenerate conditions of a more perfect type, or they are incomplete by suppression, when they are typically of a relative low degree of organization. When essential organs (stamens and pistils) of both kinds are present, the flower is called hermfiphrodite or bisexual (this condi- tion is indicated by the sign ). It must be remembered, how- 94 MORPHOLOGY, OR COMPARATIVE ANATOMY. ever, that the term hermaphrodite is used in its morphological, not in its physiological significance, for many flowers hermaphrodite in structure are practically unisexual in function. In many plants one of the circles of essential organs is suppressed, so that a given flower has only stamens or only pistils ; such flowers are termed unisexual or diclinous. The unisexual flowers are called respec- tively staminiferous or male ( tf ), and pistilliferous or female ( $ ). When flowers of both kinds occur on the same plant, this is called monoecious (Oak, Birch, Vegetable Marrow, &c.) ; when they are on distinct individuals, the plant is termed dioecious (Hop, Willow, Bryony, &c.) ; when, as in some cases, the imperfection results from a kind of regular abortion rather than total suppression, and the same plant or species exhibits at once staminate, pistillate, and hermaphrodite flowers, it is termed polygamous (Parietaria, many Palms, Maples, &c.). Some plants bear neuter flowers, desti- tute of both stamens and pistils : such is the case naturally with the outer florets of many Composites, and it is constantly seen in the garden Snowball ( Viburnum Opulus) and Hydrangea. The diclinous or unisexual condition is often typical and hereditary in certain families, such as Amentiferae, &c. ; but cases of diclinism occur not unfrequently in exceptional genera of families the majority of whose genera are bisexual, as in Ruscus among the Liliaceae ; or in exceptional species (by abortion), as in Lychnis dioica ; sometimes it occurs by abor- tion in species normally possessed of perfect flowers, as in Asparagus. Arrangement of Parts. The suppression of an entire circle renders a flower unsymmetrical ; for when the corolla is absent, we find the stamens commonly superposed to the segments of the preceding circle, as in Clienopodium ; but this is in accord- ance with the normal type, as the stamens should be superposed to the sepals, the intermediate petals (here suppressed) alter- nating with both. Not unfrequently we find abortive organs, such as sterile filaments or " glands," of various kinds forming circles which restore the symmetry of apparently unsymmetrical flowers. The cases of unsymmetrical conditions arising from the superposition of the organs of succeeding whorls are explained by some entirely by suppres- sion or abortion ; others more correctly refer some of these cases to chorisis. In Geranium we find alternating with the petals five little glands which must be regarded as abortive stamens, since in the succeeding whorl the five stamens alternate with these and stand in front of the petals ; the five innermost and longer stamens, again, are superposed to the glands. In Erodium the outermost row is represented by glands, the second row by sterile filaments, and only five perfect stamens exist. Much the same conditions occur in the Linaceae. On the ground of such facts as these, THE FLOWER. 95 the superposition of the stamens to the petals in Ehamnacese, the Vine, &c. has been explained by supposing a circle of stamens to have been suppressed between the petals and the existing stamens. Several recent writers attribute the stamens of Rhamnacepe to chorisis of the petals with suppression of the true stamens, extending the same explanation to Ityttnenacese and the Vine, where the true stamens are represented by sterile rudiments or glands within the existing stamens. In the Primrose, according to Pfeffer, the petals originate from the backs of the stamens, though in other cases it would seem that the stamen arises from the petal. In Primulaceae the opposition of the stamens to the petals may, however, be a result of suppression j for in Samolus we find five lobes on the throat of the corolla alternating with the petals, while Lysimachia ciliata has five sterile filaments in addition to five perfect stamens. Isomery, Anisomery. Suppression or abortion of part of the organs of one or more circles is, as has been said, a very common cause of want of symmetry. This occurs by far most frequently in the carpellary circles, as might he expected from the organs being crowded on the point of the receptacle (multiplication of carpels occurring, on the other hand, where the receptacle is un- usually developed) ; the stamens exhibit it not unfrequently ; and it is observed also in the petaline whorl, and even in the calyx. Symmetrical flowers may be either dimerous, trimerous, tetramerous, or pentanierous throughout ; and when the organs are equal in all the circles the flowers are isomerous, if not so they are anisomerous : thus we have isomerous dimerous flowers in Circcsa (fig. 163) and Syringa (fig. 164), isomerous pentanierous flowers in Crassula (fig. 162), before Fig. 163. Fig. 164. Fig. 165. Fig. 163. Ground-plan of the 2-merous flower of Circaea: x represents the bract. Fig. 164. Ground-plan of the Lilac, with 2-merous circles : x, the bract ; a, a, bracteoles. Fig. 165. Ground-plan of a labiate flower, with didynamoua stamens; the posterior one (dotted) suppressed. referred to ; but, generally speaking, one or other of the whorls exhibits partial suppression. It is rare to find the sepals partially suppressed : perhaps we may con- sider this to be the case as regards the limb of the sepals in such instances as the nappus of Bidens. The corolla exhibits partial suppression in some Leguminosse, where, although the plan of the flowers of the order is pentanierous, in Amorpha only one petal exists ; a transition towards 96 MORPHOLOGY, OR COMPARATIVE ANATOMY. this occurs in other genera of the order, where, indeed, the four petals here suppressed are generally considerably smaller. In the Larkspurs (Delphinium) one petal is constantly suppressed, while the others are of irregular form ; and in Aconite three out of the five petals are inconstant in their occurrence, being, even when present, mere petaloid scales. The stamens are mostly isomerous, with either one, two, or more whorls, when the floral envelopes are regular, although there are well-known exceptions to this. The suppression or partial abortion of some of the stamens is most common where the flowers are irregular. This sup- pression is well seen in the irregular monopetalous Orders, where we find curiously graduated illustrations of the phenomenon. Thus, in the Scro- phulariacese, belonging to the pentamerous type, there are usually but four stamens, but Verbascwn has the fifth (not always fertile) ; Penfatcmon has four perfect stamens and a sterile filament ; and in Scrophularia the fifth is represented by a scale in the upperside of the corolla. In Veronica three are suppressed, and only two remain. In the Labiatae (fig. 166), again, one stamen is ordinarily suppressed ; not unfrequently two of these appear as sterile filaments ; and in Salvia, Monarda, and other genera only two stamens exist. Either multiplication or suppression is almost the rule in the carpellary circle, the isomerous condition being rather the exception. Six carpels, or a double circle, occur in the 3-merous flowers of Triglochin (fig. 166) ; and we have mentioned the occurrence of five carpels in the pentamerous flowers of Crassula and Sedum ; in the nearly allied Saxifragaceae the carpels are usually reduced to two. In Araliaceae, Aralia has five car- pels, different species of Panax three and two, while in the allied order Fig. 166. Fig. 167. Fig. 166. 3-merous flower of Triplochin maritimum, with six carpels; x represents the bract. Fig. 167. Ground-plan of Epimedium, with 2-merous circles and a solitary carpel ; a, a are the bracteoles of the pedicel. Umbelliferae the number 2 is universal in the carpellary circle, although all the other circles remain pentamerous. In Rosacese we have almost every conceivable condition ; for while multiplication takes place to a great extent in Rosa, Frar/aria, and allied genera, the normal five carpels occur in Spircea and the Pomaceous suborder ; in Ayrimonia the number is reduced to two ; Sanyuisorba has two or one ; while in the Drupaceous suborder, in Primus &c., only one carpel regularly exists, a condition which is the rule throughout the related extensive pentamerous order Leguminosse. In Ranunculaceae the number of carpels varies much. In Berberideae the outer circles are 2-merous and the carpel is solitary (fig. 167). Suppression of a portion of the carpels is almost constantly THE FLOWER. 97 found in the monopetalous Orders, where we seldom have more than two. Suppression of organs becomes exceedingly striking when associated with suppression of entire whorls. Thus in Callitriche the floral enve- lopes are wanting, and while the pistil indicates the tetramerous type, three stamens are suppressed, so that the perfect flowers consist of one stamen and one pistil, and the imperfect flowers often met with are com- posed respectively of a stamen and a pistil. The latter condition occurs also in the greatly reduced flowers of our native species of Euphorbia^ in which the involucre encloses one naked female flower, consisting simply of a pistil, and a number of naked male flowers reduced to the condition of a single stamen (see Euphorbiaceee). A curious kind of regular suppression, not interfering with symmetry, is sometimes met with, where the typical pentamerous condition is re- placed by the tetramerous, either in floVers of the same plant or on different individuals of the same species. Thus, in JRuta, in some species of Sedum, and some Alsinece, the flowers have the organs sometimes in circles of fives and sometimes in circles of fours, without any other accompanying deviations from the character of the species. Congenital Union or Inseparation. Union of the organs of the flower consists either in cohesion of the parts of 'a whorl with their fellows, or in adhesion of organs of one whorl to those of another. Both occur in almost every possible degree. It must be borne in mind, however, that these terms are often applied to cases wherein there has really been no union of previously disunited organs, but a want of separation between parts originally uniform, but which in other cases become in process of growth disjoined. Cohesion occurs in the calyx, producing what is called a gamosepalous or synsepalous calyx ; also in the corolla rather less frequently, forming a ffamopetalom or sympetalous corolla. With these terms are contrasted polysepalous and polypetalous (or dialy-sep-petalous), used to indicate that the sepals and petals are distinct, i.e. not coherent. In the Vine the petals cohere above, while they are distinct below, and the flower opens bv the separation of the corolla from the receptacle ; the sepals of Eschscholtzia are entirely coherent, and fall oft' like a cap. Union is less common among the stamens ; but in some Orders they are coherent by their filaments into one piece (nionadelphoiis), in others into two or more parcels (diadelphous). Such cases are usually due to a branching or lobing of the primary staminal leaves, and not to any real union of previously disconnected parts. Other plants have the anthers coherent (syngenesious) , while the filaments are free ; and in some diclinous flowers the stamens are united into a kind of column. The carpels exhibit every degree of confluence, from a slight coherence at the base to a firm union by their sides, complete confluence of the ovary with the styles free, confluence of ovaries and styles in part or entirely with free stigmas, and complete confluence of ovaries, styles, and stigmas. In Asclepiidaceas we have confluence of the styles, while the ovarian portions of the carpels are only slightly coherent. H MORPHOLOGY, OR COMPARATIVE ANATOMY. The details regarding coherence will be treated of more conveniently in the chapters on the separate organs. Adhesion may exist between the inner and outer circles of the floral envelopes, between petals and stamens, and between stamens and pistils, also between calyx, corolla and stamens with pistil free ; or the calyx, corolla, and stamens may all adhere to the pistil. No case is known of adhesion of the three inner circles with a free calyx. What is commonly termed adhesion is, as before explained, more strictly want of separation between parts which ordinarily become detached one from the other during growth. Insertion. The point of emergence of an organ is inappropri- ately called its insertion ; and when an organ is not adherent to any other circle, but emerges directly from the receptacle, it is said to be free. When the outer organs spring from the receptacle, they are called hypogynous (fig. 168), signifying below the pistil ; if the stamens appear to adhere to the free tube of the .calyx or corolla, they are said to be Fig. 169. Fig. 168. Fig. 168. Hypogynous flower of Ranunculus, in section. Fig. 169. Perigynous flower of Prunus, in section. perigynous (fig. 169) ; while if the tube of the calyx or receptacle is carried up and adherent to the sides of the pistil, the stamens become apparently inserted on the top of the ovary, and are then called epigynous (fig. 170). Some other terms are used in reference to the insertion of the petals and stamens : thus, thalamifloral, or emerging from the receptacle, is synonymous witlh hypogynous (fig. 168) ; calycifloral, indicating emer- gence from the throat of the calyx, may agree with either the perigynous (fig. 169) or epigynous (fig. 170) conditions; while corollifloral, emer- gence from the tube of the corolla, is a form of the perigynous insertion. The terms inferior and superior are occasionally applied to the calyx, according as it is free (fig. 168) or adherent (fig. 170) to the pistil all the way up; occasionally it is half-superior (Saxifraga^ fig. 171). The same terms are also applied to the .pistil in the reversed sense to indicate the THE FLOWER. 99 same conditions : i. e. when the calyx is inferior, the free ovary is supe- rior, and vice versa. The terms perigynous, &c., and calyeifloral, &c. are in constant use and very convenient, but they may convey false notions as to actual structure. In the perigynous flowers of Kosaceae, for example, such as those of Fragaria, Geum, &c., the stamens really rise from an expansion of the receptacle, forming the so-called throat of the calyx, and in Rosa, Pyrus (tig. 172), and other similar forms the carpels are really enclosed in an excavated receptacle or receptacular tube, from the upper edge of which sepals, petals, and stamens arise. In these cases the receptacle instead of lengthening into a conical extremity becomes tubular. Fig. 170. Fig. 171. Fig. 172. Pig. 170. Epigynous flower of an Umbellifer in section; pistil completely inferior. Fig. 171. Flower of Saxifrage in section, with a partially adherent calyx and half-superior pistil. Fig. 172. Flower of Pyrus in section; pistil inferior, calyx superior, corolla superior, stamens perigynous. The adherence of stamens to pistils produces what is called the gynan- drous condition, so remarkable a character of the Orchidaceae and Ascle- piadaceae. Irregular growth. Irregularity of flowers arising from unequal size, different form, or unequal degree of separation of the organs or whorls is extremely common. Different form and size produce irregularity in the floral envelopes and stamens of many plants where these are free ; and this is often associated with irregularity arising from suppression. The irregular union occurs alone, or is superadded to all the rest when the organs are coherent ; this con- dition is oftenest found in the floral envelopes, in the stamens less frequently, and in the pistils perhaps not at all. Irregular polypetalous flowers illustrating this point present themselves in Papilionaceous plants, in Fumariaceae, Violacese, &c. ; irregular poly- sepalous calyces occur in Acomtum, Delphinium, &c. Stamens are gene- H2 100 MORPHOLOGY, OR COMPARATIVE ANATOMY. rally alike in the same circle ; but in didynamous stamens (two long aud two short) there is an exception to this. Irregular gamosepalous calyces and irregular gamopetalous corollas are met with in endless variety of forms, in the majority of which there is a tendency of the component organs of a whorl to associate together in two groups, front and back, so as to produce a bilabiate condition, as in the corollas of most Labiatae and Scrophulariaceas. Unequal degree of union of stamens produces the diadelphous condition of many Leguminosae, and the still more irregular polyadelphous condition in the Orange. These points will be further explained in the next Sections. It may be repeated here, that the deviations from irregularity falling under this head almost universally arise during the development of the bud from its originally regular rudiments. Development of the Thalamus. Most flowers have only very short or contracted internodes developed between the whorls ; that is to say, the receptacle or thalamus is usually not lengthened. Exceptions occur to this, however ; for in the Caper tribe we have long internodes between calyx, corolla, stamen, and pistil. Fig. 174. Fie. 173. Fig. 175. Fig. 173. Section of a flower of S'lene, with an internode between the calyx (which is turned back) and the corolla. Fig. 174. Section of the flower of the Eose; the pistils seated in a hollow receptacle. Fig. 175. Flower of the Maple (Acer'), with the petals removed, showing the stamens arising from an hypogynous " disk " or outgrowth from the receptacle. In Dianthus and SUene (fig. 173") there is a short internode between the calyx and corolla, in Gentiana between the stamens and the pistil. In the Rose (fig. 174) the receptacle is expanded into a cup, from the inner walls of which the carpels arise ; and in Nelumbium the carpels are immersed in a large fleshy receptacle. In many cases what is termed calyx-tube is in reality a tubular prolongation of the receptacle, from the edge of which the calyx, petals, and stamens arise. In the Paeony the receptacle is raised up into a kind of cup or " disk " round the carpels, in THE FLOWEB. 101 P. Moutan enclosing them all but tlie stigmas : the apparently inferior position of the ovary of Victoria depends ou the discoid development of the receptacle where the outer floral circles are inserted. A ring of similar nature, free from the ovary, occurs in Alchemilla. Another con- dition exists in the Mignonette (Reseda), where the cup-like or annular development of the receptacle is inside the floral envelopes, and forms a support to the stamens surrounding the ovary. This form of the " disk," which occurs also in Acer (fig. 175), must not be confounded with those depending on the presence of perfect or imperfect whorls of abortive floral organs. The epigynous disk of Umbelliferse (fig. 170) and allied orders is probably a development of the receptacle, since the so-called adherent tube of the calyx is perhaps an excavated receptacle. In Circcea, and to a greater or less extent in other Onagracese, the epigynous process supporting the floral envelopes and stamens is prolonged into a tube above the inferior ovary, surrounding the long free style. Where organs are multiplied, we often find the thalamus lengthened into a conical or clavate body, to give room for the insertion, as with the pistils of Ranunculus (fig. 168), Magnolia, Fragaria, &c. In Geraniacese the receptacle is prolonged into a column in the centre of the confluent styles ; and the same occurs to less extent in Euphorbia. When a circle of organs is removed from its predecessor by a stalk-like internode, it is called stipitate. The column supporting the carpels of Geranium (p. 143, fig. 276), or those of Umbelliferse, is termed a carpophore ; the stalk of the ovary of Gentiana is a yyno- phore ; a stalk above the corolla, supporting both stamens and pistils, as in Passion-flowers, is &gynandrophore. The form of the flower is dependent in many cases on the obliquity of the receptacle, as in Le- guminosae, Aconitum, Delphinium, and many other irregular flowers. Enation, Substitution, Superposition. The modifications arising from enation have been already alluded to ; while those dependent on the substitution of one organ for another, as in many double flowers where the stamens are replaced by petals, demand only pas- sing notice. Superposition arises from various causes, as from the abortion or suppression of a part that should come between and alternate with the superposed parts, or it may arise from chorisis or enation, or from true superposition of successive cycles, as in tSabia, and possibly by growth in the axil in the same way that a bud is axillary to a leaf. Causes producing modifications, The modifications met with in the construction of flowers may be dependent upon arrest, exaltation, or per- version of growth or of development, either separately or in conjunction. By growth is meant mere increase in bulk, by development the progressive change in the form and structure of organs (metamorphosis) which takes place in the course of their passage from the initial to the adult stage. By the action of the causes above mentioned, the parts of a plant vary in com- position (simple or divided leaves, &c.), number (increased or diminished), 102 MORPHOLOGY, OR COMPARATIVE ANATOMY. arrangement (spiral, opposite, or verticillate, &c.), freedom or union, form (regular or irregular), order of growth (consecutive, simultaneous, inter- calary, definite, indefinite or interrupted, congenital or postcongenital, &c.). These changes may be congenital and hereditary, and then common to all plants that have originated from a common ancestral type j or acquired or adaptive, when they have become manifest in order to fulfil certain special or individual requirements, or to put the plant in harmony with the circumstances under which it has to live. Thus the form, colour, and perfume of flowers are often in direct relation to the habits and structure of the insects which visit them for the sake of the honey, and whilst so engaged effect the fertilization of the flower in ways hereafter to be mentioned. It may thus be said that the form of the plant and its parts is dependent, 1st, on hereditary endowment, and 2nd, on adaptation to the work it has to do, the means it has of doing it, and the circumstances under which it must be accomplished. Sometimes from causes only im- perfectly understood there is a reversion from a more complex or adult to a simpler or embryonic form, as when a petal or a stamen becomes leafy ; and other cases of similar character may sometimes be explained hypo- thetically by assuming them to be reversions to an ancestral form. Diagrams, Floral formulae. For purposes of ready comparison, and to avoid lengthy descriptions, diagrams or plans and floral for- rnulse are made use of. A diagram is intended to show the number, arrangement, and relative po- sition of the parts of the flower. Thus, fig. 162, p. 91, represents the diagram of a complete, regular, isomerous, pentamerous flower. Fig. 161, p. 90, shows a trimerous flower, with the parts in regular alternation. Diagrams of this kind are spoken of as empiric when tney represent the actually existing state of the flower, while they are termed theoretical when the condition shown is that assumed or known to be the typical one, apart from the modi- fications brought about by abortion, chorisis, &c. Thus, fig. 165, p. 95, shows the usual condition in Labiates, where there are four stamens, the situation of the fifth, which is abortive, being shown by the dotted circle. In place of diagrams floral for mulce are sometimes made use of. These are constructed in various ways according to the views of various authors, though it would be convenient if uniformity of practice could prevail in this matter. The following illustrations will exemplify these formula3 j thus a regular pentamerous encyclic flower may be represented thus : S5 P5 A5 G5; the S representing the calyx of five sepals, P the corolla of five petals, A the andrcecium of five stamens, and G the gynsecium or pistil of five carpels, each whorl distinct from each other, and the parts of each indi- vidual whorl also distinct and free from cohesions or adhesions so-called. In the instance given, the parts are assumed to be all in their proper alternate position ; but this might be more clearly shown thus : So A5 P5 G5 or more briefly thus : THE FLORAL ENVELOPES. 103 F 5 = S A P G the F standing for flower. In order to indicate cohesion a line or a bracket over the letters may be used, and a similar line placed vertically by the side of the letter may represent adhesion ; thus the formula r\ r\ F * S G F5 = r ^ | PA may be taken to represent the flower of a Primrose,, in which the five sepals are coherent, the five petals likewise coherent, the five stamens free among themselves, but superposed and adherent to the corolla, and lastly the five carpels coherent one with the other. The spiral or verti- cillate arrangements may also be indicated by similar devices, thus : would indicate a calyx of five sepals arranged spirally on the plan, a corolla of five petals verticillate, an androecium of numerous stamens arranged spirally, and a gynsecium or pistil of five coherent carpels, the sign rv> indicating a spiral arrangement, and the sign oo always indicating an indefinite number of parts or too many to be readily counted *. Sect. 8. THE FLORAL ENVELOPES OR PERIANTH. Calyx and Corolla. The floral envelopes of a typical flower consist of two circles of organs, forming the calyx and corolla. There is no fundamental difference between sepals and petals (the organs which compose these circles) ; and the only general defini- tion that can be given is, that the outer circle (or, if only one circle exists, that circle) is the calyx ; the corolla consists of the second circle (or sometimes of additional circles) of foliar organs intervening between the calyx and the stamens. In some few cases the perianth or floral envelopes are entirely want- ing, as in many Aroids. The above definition of the calyx is liable to exception in rare cases; for in the Malvaceae, the Dipsacese, and some Rosacese the true calyx * For details relating to the morphology of the flower the student should con- sult Eichler's 'Bluthendiagramme,' Sachs's Text-Book, and Masters'? 'Vegetable Teratology.' Reference should also be made to the account of the principal natu- ral orders in the following pages, wherein the general principles of morphology are illustrated by reference to their particular application to different orders. 104 MORPHOLOGY, OR COMPARATIVE ANATOMY. is double, that is, a circle of smaller organs, resembling sepals, or a tubu- lar cup, stands outside the proper calyx, forming what is called an epicalyx (fig. 176). The ambiguity in these cases is removed by the existence of a well-developed coloured corolla inside the calyx. The epicalyx of Malvaceae, like that of Dipsacese, is perhaps to be regarded as an involucre of bracts. That of Potentilla (fig. 176, B) and allied genera is sometimes supposed to represent confluent lateral lobes or stipular appendages of the sepals. Perianth. The terms perianth or periyone are used in a general sense to signify all the floral envelopes, and are specially applied to instances where the distinctions between calyx and corolla are not apparent, e. g. when the sepals and petals are all petaloid, as in the Tulip, &c., and when they are all green and sepaloid, as in the Dock, &c. The words are also applied to the calyx in the Orders where it regularly exists alone, either in a sepaloid or petaloid con- dition, as in Daphne and the Monochlamydeous orders generally. ^Estivation. The arrangement of the floral envelopes in the bud, the aestivation or pr -defloration, is a subject of great importance in systematic botany, as affording very regular characters in the ma- jority of the natural orders. The plans of aestivation given in illustrative works (fig. 177) are taken from horizontal sections of the bud just before it opens; and in cases where the sepals or petals are coherent below, the section is supposed to pass through the free lobes of the limb. The aestivation of flower-buds agrees essentially with the verna- tion of leaf-buds (p. 72), especially as regards the folding of the individual organs ; the sepals and petals may be reclinate, condupli- cate, plicate, convolute, involute (a still further rolling-in rendering this induplicate), revolute (in excess becoming reduplicate} ; circinate as in the petals of Hamamelis, and an additional case is found in Poppies and some other flowers, where the petals are irregularly crumpled-up, or corrugate. [Collectively the arrangement of the organs is either imbricate, valvate, or open. Imbricate. The varieties of this kind are best seen in whorls of five, which furnish four distinct forms of aestivation, each being cleducible from that which precedes it, by shifting the edge of one petal, as follows : 1. Quincuncial, or the -f plan (fig. 177, A). 2. Half-imbricate (B), which only differs from the last in that the 4th part overlaps the 2nd. 3. Imbricate proper (C), in which the 5th part overlaps the 3rd. 4. Convolute (D), in which the 3rd part; overlaps the first. If convolute petals are twisted, they are called contorted (fig. 177, F). In other words, the axis of a median line clown each petal is erect in the simply convolute, but spiral in the con- torted. THE FLOKAL ENVELOPES. 105 Imbricated whorls with four or three parts are usually either imbricate proper or convolute. Whorls with two parts are often equitant (fig. 125), as are the petals of Poppies ; or half-equitant, as the sepals of Poppies, of which each part has one edge overlapping an edge of the other. These two conditions may be regarded as degraded forms of the imbricate proper and convolute respectively. A special form of the half-imbricate is seen in the estivation of papi- lionaceous corollas (tig. 177, E), and is named vexillary, from the posterior petal, which is called the vexillum, or " standard." The order of the petals is as follows : The standard is No. 1 ; either keel-petal is No. 2 ; the wing- petal on the opposite side of the flower to the last is No. 3; the other wing No. 4 ; and the remaining keel-petal is No. 5. Thus No. 4 will be seen to overlap No. 2 (see tigs. 191-193, p. 111). The aestivation of the Snap-dragon (Antirrhinum majus) is called cochlear, but it is really half-imbricate. When the organs are coherent at their margins they may become variously plaited or plicate, the portions sometimes assuming the contorted character, as in the corolla of the Convolvulus (fig. 177, H). Fig. 177. A B D O/^x y^< */*^ OOO Estivation of corollas. A. Quincuncial. B. Half-imbricate. C. Imbricate. D. Convolute. (After Gr. Henslow.) E. Vexillary aestivation of the corolla of a Papilionaceous flower. F. Contorted estivation of the corolla of Malva. Gr. Valvate aestivation of the corolla of Viils. H. Plicate aestivation of the corolla of Convolvulus. Valvate (estivation. This kind of aestivation occurs when the mar- gins meet but do not overlap (fig. 177, Gr). If the margins of the organs are rolled inwards they are involute or induplicate (fig. 127) ; if, on the other hand, they are rolled outwards, they are called revolute or reduplicate, in both of which cases the rolled borders only are in contact, and not the absolute margins. 106 MORPHOLOGY, OR COMPARATIVE ANATOMY. Open. This is also called " straight." The parts of the whorl, usually the calyx, are so rudimentary or arrested in growth, that they do not even meet, as in the Umbelliferoe, Rubiaccce, &c. Hence this aestivation may be said to be indeterminate. Gr. H.] The calyx and corolla may both have the same aestivation, or they may be different ; and their characters may hold good for all the species of a genus, as in Hypencwn. in which the calyx is quincuncial and the corolla contorted, or even for all the genera of an order, as of Malvaceae, in which the calyx is valvate and the corolla convolute or contorted ; but it is very common for a species to have several varieties in different individual flowers, even on the same plant. The direction o the spiral in imbricated aestivations is variable, often in the same plant : occasionally the direction changes in passing from the calyx to the corolla ; at other times it remains the same ; and this character is sometimes constant, in other cases very inconstant. In determining the direction of spirals, right-hand or left-hand, it is usual to suppose one's self standing in the axis of the organ ; but many authors suppose themselves standing in front of it for instance, in the place of the bract of a flower, which gives the exact opposite of the former ; hence great confusion in the ap- plication of the terms dextrorse and sinistrorse. Calyx. The calyx is the outermost circle of the floral envelopes. It is composed of phylJomes or modifications of leaves, called sepals; according as the sepals are distinct or coherent, the calyx is termed polysepalous (or dicdysepalous), or monosepalous (or gamosepalous). The exceptions to the absolutely external position of the calyx have been pointed out. The Sepals generally bear more or less resemblance to bracts, being attached by a broad base, seldom articulated, without any stalk, and of a green foliaceous texture ; not tmfrequently, how- ever, their texture is of the coloured and delicate nature described as petaloid. They are usually entire, but the margins are some- times cut, as in the Rose (fig. 158), and they are occasionally re- duced to scale-like, or even feathery or hair-like processes. They are likewise subject to the production of pouches, spurs, &c., es- pecially at the lower part, both when distinct and when coherent ; and the apex is often more or less prolonged into a point or spine. Their mode of venation is usually like that of the sheath of the leaf. Some confusion is liable to arise in the condition called a superior calyx, where the segments are totally free : if we suppose an adherent tube to exist below, such a calyx would be monosepalous ; but the so-called calyx-tube is usually a cup-like receptacle, and the sepals originate or THE FLOKAL ENVELOPES CALYX. 107 become detached from the point where they appear to be inserted for example, in Rosaceae, Umbelliferee, Cucurbitacese, Composite, &c. Polysepalous Calyx. In the polysepalous calyx, if the sepals are alike and symmetrically arranged, the calyx is regular if some of the sepals are larger than others (Helianthemum, Cheiranthus, fig. 178) it becomes irregular ; and this is still more the case when the sepals differ in form as well as size. Some of the most remarkable irregular forms of polysepalous calyx occur accom- panied by a petaloid condition, as in Aconitum (fig. 179) and Del- phinium. The coloured calyces, both regular (Fuchsia) and irregular, may be easily mistaken for corollas ; but they are known by their exterior posi- tion, and in some cases by the existence of a more or less perfect corolline circle within. Direction. The direction of sepals (whether distinct or partially co- herent) is indicated by technical terms ; thus they may be erect, cvnni- vent (the points turning in), divergent, or even re/icxed. Fig. 179. Fig. 178. Fig. 180. Fig. 178. Irregular polysepalous calyx of Cheiranthus. Two of the four sepals are dilated or "gibbous " at the base. Fig. 179. Irregular polysepalous coloured calyx of Aconitum Napellus, Fig. 180. Kegular gamosepalous calyx of Silene injluta, Parts of a Gamosepalous Calyx. When the sepals are confluent or not separated, the gamosepalous calyx (fig. 180) is usually de- scribed as a whole. The part where the sepals are coherent or are still inseparate is the tube ; the upper boundary of this is the throat (faux) ; and the free or spreading portion constitutes the limb composed of lobes or teeth with intervening sinuses when the upper part of the sepals is more or less distinct ; entire when the sepals are so completely confluent that the compound nature is not indi- cated by any teeth or fissures at the free edge. It is necessary not to confound the receptacular tube with the calyx-tube 108 MORPHOLOGY, OR COMPARATIVE ANATOMY. proper. An investigation of the course of development will show the difference between the two, and, generally speaking, the position of the petals and stamens ; if the latter are perigynous, it is probable that the tube below is receptacular. The venation and internal structure will also serve as guides in this matter, inasmuch as the receptacular tube contains not only its own vascular bundles, but those of two or more verticils of flowers, and which are derived from the primary ones by subdivision. Form, The gamosepalous calyx is subject to the same kinds of modification as that in which the sepals are distinct. It is either regular or irregular. Of the regular kinds we find a large number which present forms ad- mitting of general technical names, such as tubular or cylindrical, cup- shaped, infundibuliform or funnel-shaped, campanulate or bell-shaped, urceolate when the tubular form is expanded below, turbinate or top- shaped when expanded above, inflated when the lateral view is oval or roundish with a narrow mouth (fig. 180), &c. In some species of Cam- panula there are regular appendages at the bottom of the sinuses between the teeth. In Primula and some other genera the tubular calyx is an- gular or plaited. Calyces nearly resembling the above are rendered irregular either by a greater extent of disunion taking place between some of the sepals, the intervening fissures being so much deeper than the others that the teeth become associated in two sets, giving a bilabiate condition (fig. 181) or by irregularities at the base, where a shallow pouch renders the calyx gibbous (fig. 178), a deeper one saccate, and a long narrow pouch forms what is called a spur. In Pelargonium this spur adheres to the peduncle. In some instances a tubular development of the receptacle or fiower- stalk simulates the spur of the calyx. Fte. 184. Fig. 181. Fig. 183. Fig. 181. Bilabiate calyx of Salvia. Fig. 1S2. Floret of Kcabiosa, the limb of the calyx replaced by bristles (pappus). Fig. 183. Fruit of Cichorium, crowned by the persistent calyx represented by a circle of spines (pappus). Fig. 184. Section of the persistent calyx, enclosing the ripe capsule, of Hyoscyamus. The Pappus. The free portion of the calyx of Com posits, Dip- sacese, and Valeriauaceae exhibits a very aberrant condition by appearing in the form of scales, bristles, or feathery or simple THE FLORAL ENVELOPES COROLLA. 109 hairs, constituting what is called the pappus (figs. 182, 183). In Centranthus the limb of the calyx is undeveloped when the flower opens, but expands during the ripening of the fruit into a crown of feathered processes. It is doubtful whether the pappus is not in some cases a series of mere epidermal growths or trichomes. Duration. The duration of the calyx varies much. In the Papave- racefe it is caducous, falling off when the flower opens ; if it falls with the corolla soon after fertilization of the ovules, it is deciduous ; very fre- quently it is persistent during the ripening of the seeds, as in Labiates, some Solanaceae (fig. 184), Composite (fig. 183), &c. ; the upper part sometimes separates by a circular slit, leaving the. base, as in Datura Stramonium ; occasionally it grows during the maturation of the fruit, and is then accrescent , forming in Phy sails and Trifolium fragiferum, for example, a vesicular envelope to the fruit. In the Marvel of Peru and other plants it is marcescent, remaining and growing into a firm envelope of the fruit. Further details respecting the characters of the calyx are given under the head of the Perianth. The Corolla. The corolla is composed of all the leaf-like organs or floral envelopes situated between the calyx and the stamens ; these are individually called petals, and may exist in one or more circles. "Where many circles exist, the inner organs often become stunted or deformed, and more or less resemble barren filaments or abortive stamens (Nymphcea). Each petal, under ordinary circum- stances, intervenes or alternates between two sepals. The petals are either distinct, and then the corolla is called dialypeta- lous or polypetalous ; or they are more or less coherent or inseparate, and the corolla is gamopetalous, sympetalous, or monopetalous. When more than one circle of petals exists, the corolla is multiple or double ; this is normal in certain plants, but is very liable to occur from transformation of stamens, &c., or from actual multiplication of whorls, as in cultivated flowers of the Rose, Camellia, Ranunculus, Anemone, &c. The petals are usually direct outgrowths from the thalamus, but some- times they appear not to be autonomous parts but secondary outgrowths from the stamens, as in some Mallows, Primroses, &c. The Petals. Although petals frequently depart more than or- dinary sepals from the character of true leaves in colour and tex- ture, they present greater resemblance in some respects, since they frequently have a more or less developed petiolar region, which is sometimes of considerable length, at other times a mere thickened point ; and they are commonly articulated to the receptacle. The petiolar portion of the petal is called the claw (unguis), the expanded portion the limb (lamina) (fig. 185). Petals are likewise more frequently cut at the margins, as in the fringed petals of Pinks and the laciniated petals of Lychnis Flos-Cticuli, or they are deeply 110 MORPHOLOGY, OE COMPARATIVE ANATOMY. divided into lobes, as in many Caryophyllacese (fig. 186) and the pinnatifid petals of Schizopttalum, &c. Fig. 185. Fig. 187. Fig. 186. Fig. 185. Petal of Dianthus, fringed and stalked. Fig. 186. Bilobed petal of Alsine media. Fig. 187. Spurred petal of Aquilegia. Forms of Petals. The forms of petals resemble many of those indicated for simple true leaves ; in addition to which others occur presenting curved surfaces : these are called simply concave, navi- cular or boat-shaped, cochleariform or shaped like the bowl of a spoon, &c. ; or they may have basal pouches, and be gibbous, sac- cate, or spurred (fig. 187). Others have peculiar appendages above, such as the crests in Polygala and the strap-Like inflexed points in the petals of the Umbelliferae. The term nectary is vaguely employed to indicate certain struc- tures of varying character intermediate in position between the petals and the stamens, and different in aspect from both. Petals are ordinarily of delicate structure and coloured, whence we derive the term petaloid ; but they vary in texture from a membrana- ceous to a thick and fleshy condition, such as we see in Magnolia, Nym- ph&a, &c. Polypetalous Corollas are regular when the petals are equal and symmetrically arranged; the individual petals may be them- selves either symmetrical or oblique, provided they are all alike. Some of them have received special names, such as : the rosaceous, where there are five spreading petals ; the liliaceous, where six petals spread gradually from a funnel-shaped origin ; caryophyllaceous, where five petals have long erect claws ffbm which the limbs turn off at a sharp angle ; cruciform, where four such long-clawed petals with horizontal limbs stand in the form of a cross, as in the Wallflower, &c. Slight degrees of irregularity arise from some petals growing larger than others, as in the case of the outer petals of the outer flowers of the corymbs of Iberis, those of the umbels of Umbelliferee, &c. ; but more striking irre- gularity results from unlikeness of the petals and disturbance of symme- try in their insertion or point of emergence. The imperfect corolla of THE FLORAL ENVELOPES COROLLA. Ill Aconite (fig. 188) is an example of this ; and a still more important case occurs in the papilionaceous corolla of Leguminosce (figs. 191-193), which is composed of five petals, of which the posterior, the vcxillum (fig. 192, a) or standard, the largest, usually symmetrical in form, is placed trans- versely ; the two lateral (fig. 192, b, 6), mostly oblique in form and small, forming the alee or wings, stand right and left, with the edges fore and aft ; and the two anterior (fig. 192, c, c), also small and oblique, often coherent in front, and forming the carina or keel, also stand with their edges forward. Fig. 188. Fig. 190. Fig. 189. Pig. 188. Flower of Aconitum with the sepals removed, showing the two hammer-headed posterior petals (or nectaries), with lateral and anterior scale-like petals, outside the numerous stamens. Fig. 189. Bilabiate scroll-like petal (or nectary) of Helleborus. Fig. 190. Floret of Composite, with inferior ovary surmounted by scaly pappus and tubular corolla. Examples occur in the large order Leguminosse of almost every modi- fication of the papilionaceous corolla, approaching to regularity in Baptisia for instance, and still more in Cassia. Irregular corollas exist also in the Fumariacese, in Viola, B.ilsaminacese, Pelargonium, Tropceolum, and very manv other plants. Fig. 191. Fig. 191. Papilionaceous corolla of Pea. Fig. 192. The separated petals : a, vexillum ; ft, I, alae ; c, c, carina. Fig. 193. Ground-plan of floral envelopes, showing the coherent sepals and aestivation of the petals. The central line shows that the flower may be symmetrically divided into two equal halves. 112 MOEPHOLOGY, OE COMPAEATIYE ANATOMY. Gamopetalous Corollas have a tube, throat, and limb like the gamosepalous calyx; and similar terms are used to indicate the more common regular forms, such as tubular (fig. 190), campanulate (fig. 194), funnel-shaped or infundibuliform (fig. 195), urceolate (fig. 196), &c., a few others being requisite for the corolla, more especially such as rotate, when the tube is extremely short and the limb spreads at a right angle (Anagallis), hypocrateriform or salver- shaped when a similar limb turns off from a long slender tube (Jasminum, Phlooc) (fig. 197), &c. Irregular gamopetalous corollas often furnish important syste- matic characters ; and several of the forms or classes of forms have special technical names. The ligulate corolla is tubular at the base ; but disunion soon occurring at one sinus, the limb is turned off to one side in the shape of a flat rib- bon or strap, on the margin of which occur more or less distinct teeth Fig. 194. Fig. 195. Fig. 19G. Fig. 194. Campanulate corolla of a G-entian. Fig. 196. Urceolate corolla of a Heath. Fig. 195. Funnel-shaped corolla of Convolvuhts. Fig. 197. Salver-shaped corolla of Phlox. indicating the five component petals (fig-. 19.8) j this is especially found in the r&y florets of Composite : a modification with the tube and limb wider in proportion to the length occurs in LobeliacecB. The labiate or bilabiate corolla of the Labiatae (fig. 199) is formed by the two upper Eetals of the limb, which are scarcely at all separated, and stand apart :om the three lower or anterior petals, which also are only partially separated^ forming a lower lip opposite the upper one and projecting for- ward from the throat of the corolla : sometimes the upper lip is concave, and is then termed galeate, or helmet-like ; in other cases (Ajuga) it is almost abortive. Almost every modification of this form occurs in the Labiatee, ap- proaching to an almost regular tubular corolla in Mentha. This form occurs also in the florets of some Composite and in those of various Dip- sacese, where, however, the upper lip is 3-lobed and the lower 2-lobecl ; in the Honeysuckle the upper lip contains four petals, and the lower is formed by a solitary one. Veronica has an irregular corolla intermediate between bilabiate and rotate (fig. 200). THE FLORAL ENVELOPES COROLLA. 113 The personate or mask-like corolla is rather indefinite in form : the type of it occurs in Antirrhinum (fig. 201), which approaches the labiate form ; but the throat is closed by a gibbous projection (forming the palate), giving the front view the appearance of a mask with a broad-lipped mouth. Fig. 199. Fig. 201. Fig. 200. Fig. 198. Ligulate corolla of Composite, with " inferior " ovary and scaly pappus. Fig. 199. Bilabiate corolla of Salvia, of five united irregular petals. Fig. 200. Corolla of Veronica, bilabiate in structure, but the four segments spreading like a rotate corolla, and with two stamens. Fig. 201. Personate corolla of Antirrhinum. This is accompanied by a similar gibbons condition of the base of the tube in Antirrhinum, and by a spur in the same situation in Linaria. Aberrant forms of this type' occur in Calceolaria (fig. 202), Utricularia Fig. 202. Fig. 205. Fig. 204. Fig. 203. \ Fig. 202. Personate corolla of Calceolaria,. Fig. 203. Personate corolla of Utricularia. Fig. 204. Petals of Lychnis, with scales at junction of stalk and blade. Fig. 205. Section of a flower of a Boraginaceous plant, showing scales in the throat, between the stamens, superposed to the petals. 114 MORPHOLOGY, OR COMPAKATIVE ANATOMY. (fig 1 . 203) ; and it runs into the labiate form by such corollas as those of Melampyrum c., becoming tubular in Digitalis. Forms allied to this occur commonly in Bignoniaceaa, Gesneraceae, Acanthaeere, c. When the throat of a bilabiate or irregularly lobed tubular corolla is widely opened, it is called ringent or gaping. Outgrowths from Petals. Petals when distinct sometimes ex- hibit appendages on the inner face which have been interpreted as stipulary, as in Lychnis (fig. 204) ; in Ranunculus we find a minute scale at the base, and in Parnassia a largish scale, simple or divided, and of glandular character. In gamopetalous corollas we often find a circle of scales in the throat, either free or confluent into \vhat is called a coronet (corona), sometimes developed so far as to produce a long tube projecting from the throat. In other cases there is simply a ring of hairs in the throat (Mentha, &c.). In most cases the scales are in front of the lobes of the corolla (fig. 205), rarely alternate and opposite to the sinuses. Examples of circles of scales in the throat occur especially in the Boraginacese (Myosotis, Symphytum, c.), in Cuscuta, &c. In Narcissus poeticus and other species the corona is a complete ring, while in JV. pseudo-narcissus (the Daffodil) it forms the deep yellow tube projecting from the centre. Some authors attribute these structures to chorisis, others rearard them as representing a circle of regular stamens in an abor- tive condition ; and the alternate scales of Samolus may represent an abortive circle of stamens, as this would restore the symmetry of the flower. Usually, however, they are mere outgrowths from the petals, formed by enation at a late stage of development. These structures, by a confusion of terms, have been called nectaries and nectariferous scales. The terms scale and coronet are more exact and convenient. Fig. 206. Duration. The corolla is caducous, deciduous, or /7I| persistent, like the calyx. Occasionally it falls away it in part by a circular slit, as in Orobanche and Rldnan- ^M thus. In Vitis the caducous corolla separates from the recep- ^Se v1ne We The tacle at the bases of the petals, which cohere above and petals, cohering fall off like a little star when the flower opens (fig. 206). l Srtn *2 The corolla is mostly deciduous j it is persistent in Cam- star - shaped panula. P iece - In withering, the petals are sometimes closed (occlusa'], as in Eclieveria, spreading as in Boussingaultin, reflexed as in Begonia, crisped as in Pavia, pulpy as in Tradescantia, circinate as in Capparis, recircinate as in Mesem- bryanthemum, and conduplicate as in some species of Ornithogalum. The Perianth, in a special sense (see p. 104), consists of the floral envelopes when composed of two circles of similar organs, so that, except in position, there is no difference to be seenbetw r een THE FLORAL ENVELOPES PERIANTH. 115 Fig. 207. calyx and corolla, as in the Tulip ; or of one circle, then always called a calyx whatever its colour, as in Monochlamydeous flowers. A large numher of the Monocotyledonous orders possess a petaloid perianth ; that is, there are two circles of petaloid organs, which, from their resem- blance, or actual coherence, have the appearance of a single hexamerous whorl. This perianth may be re- gular (fig. 207) or irregular, like the normal calyx and corolla ; it may be polyphyllous or gamophyllous ; and the outer circle may differ to some extent from the inner in form, size, and colour, without other ir- regularity. The forms are described by the same Regular e-merous peta- terms as those used for the calyx and corolla E^SfagStg We have a regular polyphyllous perianth in the pogynous stamens and Tulip and Lily ; a regular gamophyllous perianth in a - < Jj[ l jjJ]^k^J^ Hemerocallis, Convallaria, Tarnus, &c. ; a regular poly- phyllous perianth with unlike circles in Iris j and irregular polyphyllous perianths in Zingiberaceae, Orchidacese, &c. Perianth of Orchids. The irregular perianth of Orchidaceae (figs. 208 & 209) requires especial mention, as the Order is very large and the characters of the perianth peculiar. There are three outer organs (a, a, a), more or less alike, and usually smaller than the inner; of the inner, the lateral (b, b) are smaller than the posterior (6 f ), called the lip (or label- lum), which is often excessively developed, and even divided into regions which receive separate names ; in many of our native Orchids it possesses a spur (fig. 208, &*). Fig. 209. Fig. 208. Fig. 210. Fig. 208. Flower of an Orchis, seen in its natural position, where, owing to the twisting of the inferior ovary, the anterior or inferior part is above and the posterior below. , , a, a, represent the outer parts of the perianth or petals ; 6, 6, the lateral petals ; b', the labellum, prolonged behind at the base into a spur, 6*. Fig. 209. Ground-plan of the flower, with the same references. Fig. 210. Flower of Luzula: b, the 6-merous scaly perianth, surrounding six hypogyuoua stamens and a central 3-cornered pistil with a single style and three stigmaa. i2 116 HOEPHOLOGY, OE COMPAEATIYE ANATOMY. Perianth of Palms. The perianth of the Palms, of Juncaceae (fig. 210), and other Monocotyledons is composed of scale-like, fleshy or mem- branous organs, either free or confluent, approaching to the condition found in the Glumiferae. Monochlamydeous Perianth. The perianth of the Mono- chlamydeous Dicotyledons is very varied in form, texture, and colour. It may be gamophyllous or polyphyllous, and then regular (fig. 211) or irregular (fig. 212), and, moreover, petaloid or sepaloid. It is reduced to the lowest state in the Poplar (fig. 213), where it is a mere membranous cup ; and it is absent in the allied genus Salicc, as also in the Ash (fig. 214), which are therefore achlamy- deous. Fig. 212. Fig. 211. Fig. 213. Fig. 211. Eegular perianth of Asarum. , Fig. 212. Irregular perianth of Aristolochia Clematitis. Fig. 213. Flower of the Poplar: *). Within the pale (fig. 219) occur two or in some Grasses three-little hypogynous scales (lodiculce, #, rr), corresponding to petals ; and to them succeed the stamens and pistil. Fig. 217. Fig. 218. Fig. 217. Spikelet of the Oat : a, a, glumes ; 5, 6, the flowering glumes or outer pales of the two florets. Fig. 218. One floret detached and opened: 6, the outer pale (with an awn &*) ; 5', the inner pale. Fig. 219. The same, magnified, with the outer pale removed : b, the inner (double) pale ; x, at, the lodiculce or hypogynous scales representing the petals, within which are the three stamens and the ovary, with its double feathered stigma. The hypogynous scales are three in number in Stipa, restoring the sym- metry. The upper glume is sometimes abortive, as in Lolium, while in Nard-us both are absent. In Alopecurus only one pale is developed. The spikelet often contains one or more imperfect flowers. The perianth of Cyperaceae, where it exists, presents a still simpler 118 MOEPHOLOGT, OR COMPAEAT1YE ANATOMY. condition, analogous to that in the Amentiferous Dicotyledons, and in some cases is abortive. In Scirpus (fig. 220) it consists of a circle of bristles ; in Eriophorum it is a tuft of hairs, which grow out into a " lock " of cotton as the fruit ripens. In Carex (fig. 221) there is an urceolate or Fig. 220. Fig. 221. b Fig. 220. Flower of Scirpus, the essential organs surrounded by a circle of bristles. Fig. 221. Female flower of Carex: a, the perigynium, or perianth, in the axil of a bract; b, the tubular perigynium cut open vertically, to show how it surrounds the pistil. inflated tubular perigynium or ictriculus surrounding the pistil of the fertile or female flower, which stands in the axil of a bract, and which is itself composed of the union of two scales or bracteoles. Cyperus, Cla- dium, &c. have the essential organs naked in the axil of a bract. Sect. 9. THE ESSENTIAL ORGANS OF FLOWERS. The essential organs of flowers consist of an androecium or as- semblage of stamens, and of a gyncecium or pistil consisting of carpels with their contained ovules. The androecium and the gynsecium are both present in perfect flowers, although these latter may be incomplete, from the absence of floral envelopes. In diclinous or unisexual flowers the stamens or pistils exist alone, and the flowers are consequently imperfect. Organs morphologically intermediate between petals and stamens occur, not only normally, as in the flowers of Nymphaa, but such structures are very common in monstrous double flowers, bearing anthers or polliniferous lobes upon the borders of petals. The morphological connexion is also kept up by the existence of sterile filaments or stamen-stalks, w r hich, like the filaments of perfect stamens, may exhibit a petaloid character. In monstrous flowers sometimes imperfect organs present themselves, partaking of the outward characters both of stamens and carpels. The Disk. Abortive organs, referable either to the corolline or the staminal circles or excrescences therefrom, have been already referred to ; but it is desirable to notice more particularly the conditions of those struc- tures which are commonly described under the name of disk (see p. 100). THE ESSENTIAL OKGANS STAMENS. 119 The simplest state is that of one or more glandular papillae upon the recep- tacle, as in the Cruciferse. In the Crassulacese (Sedum, Sempervivum) we find a circle of glandular bodies Fig. 222. outside the carpels and between these and the stamens. In Cobcea, the Vine, and other flowers there is a five-lobed hypogynous disk, the stamens being inserted outside or between the lobes. In Citrus (fig. 222) the disk forms a perfect ring round the ovary. In Gaultheria there is a double circle of scales between the stamens and the ovary. On the other hand, in Tinea there are two glands, alter- nating with the two carpels of the ovary. The 9-tudy of these structures is very interesting in regard to the Fi ower O f curus with the reduction of irregular flowers to regular types. Some petals and stamens re- of the structures are rudimentary petals or stamens ; ^y^and^the 1 alnular and in other cases they are referable to developments disk surrounding the of the receptacle or torus itself (p. 100). ovary, in this case the disk is an outgrowth from the receptacle. The Androecium. The Stamens taken collectively form the Andreecium. The essential character of a stamen is, that it is that organ in which are formed the pollen-grains, the bodies by means of which the fertilization of the ovules is effected. A completely developed stamen (fig. 223) exhibits two principal regions, the filament or stalk (a), corresponding to the petiole of a leaf, or, as Clos thinks, to the midrib of: a petal ; and the anther (6), corresponding to the blade of a leaf. The anther is a hollow case containing pollen, and is therefore the only essential part of the organ : the filament may be wanting or merely rudimentary ; and the anther then remains sessile, like a leaf-blade when the petiole is not developed. The normal position of the stamens is between the petals and the pistil ; each stamen, under ordinary circumstances, intervenes between two petals or is alternate with them, and therefore superposed or opposite to a sepal. In Naias and Typha it is supposed that the stamen is axial and not foliar. The base of the filament, or of the so-called sessile anther, is usually articulated to the receptacle when these organs are free ; but this con- dition is more or less disguised when the stamens are adherent to or inse- parate from the calyx, corolla, or ovary. Staminodes or sterile filaments, i. e. such as are devoid of anthers, occur in many flowers in regular circles ; and not unfre- quently one or more stamens exist in this condition in un- symmetrical flowers. Sometimes these staminodia are reduced to mere scales, as in the odd stamen of Scrophularia (fig. 224), or to glandular papillaB, as in the flowers of many Cruciferse. 120 MORPHOLOGY, OR COMPAEATIVE ANATOMY. Filament. The filament, in its usual condition, is a slender thread-like stalk to the anther, and in this state is termed filiform. Sometimes it is almost hair-like, and incapable of supporting the Fig. 225. Fig. 226. Fig. 223. 1 Fig. 224. Fig. 223. A stamen : a, the filament; b, the anther. Fig. 224. Corolla of Scrophularia laid open, showing the four didynamous stamens and the posterior barren one, or staminode. Fig. 225. Stamen of Allium, with a trifld filament. Fig. 226. Stamen of Paris quadrifotia with prolonged connective. weight of the anther, when it is capillary, as in the Grasses ; while it is still more frequently thick at the base, diminishing gradually upwards, so as to become awl-shaped or subulate. In a few in- stances (Urtica) it is moniliform, or like a row of beads. In other cases it is more or less expanded into a petaloid condition, as in Erodium ; in Campanula it is expanded in this manner at the base. Ornitliogalum has the filament dilated in this way throughout. The dilated filament sometimes exhibits divisions : in Crambe it is forked at the summit, the anther standing on one point ; in Allium (fig. 225), Alyssum calycinum, Orniihoc/alum nutans, &c. the fila- ment terminates in three teeth, the middle one bearing the anther; and in Allium sativum one of the lateral teeth forms a kind of tendril. Branched Stamens. In some plants, as in Mallows, some Myrtacese, Hypericum, &c., the stamens are very numerous and are arranged in fascicles. The study of the development of these fascicles shows that they are originally single organs, which become subsequently divided or branched, so that the fascicle of stamens in such a case may be compared to a divided or compound leaf. Some of the divisions may be petaloid and sterile, others antheri- ferous. Appendages of other kinds are also met with, such as a pair of glandular processes, standing like stipules near the base, in Lau- racea3 (fig. 233), a single spur in Rosemary ; while in Borago the THE ESSENTIAL ORGANS STAMENS. 121 filament appears to arise on the face of a scale-like body, and in Simaba and Larrea it stands at the back of an analogous scale. The scale-like organs situated at the base of filaments, or connected with fascicles of stamens (Tiliacece), are by some regarded as furnishing evidence for the doctrine of chorisisj but they are more probably merely barren lobes of compound stamens. The Anther its parts. The anther has a typical form, which is subject to very great modification in different cases. It corresponds to the microsporangium of some of the higher Cryptogams. A regular anther (fig. 223, 6) is an oblong body, divided perpendicularly into two lobes ; the division is usually marked by a furrow on the face, and a ridge on the back (or dorsum). The central region, which is solid and represents the midrib of a leaf, is called the connective ; the lobes are hollow dilatations of the lamina, and contain the pollen. At each border, usually rather toward the face, is often to be seen a vertical line, called the suture, indicating the place where one class of anthers split open to discharge the pollen. Attachment to the Filament. The anther is attached to the filament in several ways : if the filament runs directly without interruption into the base of the connective, like the stalk of an ordinary leaf, it is said to be innate or basifixed ; if the filament runs up the back of the anther as it were, so that the latter is more or less free at the base, the anther is adnate or dorsifixed ; if the filament is attached by a slender apex to about the middle of the back of the anther, the latter is versatile. In some cases the anther is pendulous from the apex ; it is then sometimes called apwifixed. In the Tulip, the capillary point of the filament runs up into a conical pit in the base of the connective. Modifications. The modifications of the anther result from various causes from development of the connective, from the presence of ap- pendages, from variation of form of the anther-lobes, and from special conditions of the internal cells ; and there are also important differences in the manner of bursting, or dehiscence, for the discharge of the pollen. The Connective. The connective is normally a solid rib, running up the middle of the anther. If the lobes of the anther extend upward or downward beyond it, the summit or base of the anther (or both) becomes emarginate. On the other hand, the summit of the connective is prolonged in a membranous form in Viola, and also in the Composite. In Paris (fig. 226) the apex is lengthened into a point, also in Asarum, Magnolia, &c. ; in Xylopia into a fleshy mass ; in the Oleanders into a feathered process, &c. In two of the stamens of Viola the base of the connective has petaloid spur-like appendages ; and still more remarkable states occur in the Melastomaceae. 122 MORPHOLOGY, OE COMPARATIVE ANATOMY. At other times the connective expands transversely, so that the lobes become more or less separated j in such cases it may be ovate, orbicular, &c. (Melissa, the Lime-tree, &c.). This is especially the case with the lower part ; and examples may be found illustrating this point, forming a series from the state where the bases of the lobes are but slightly separated, to that in which they are inclined together at the summit at an angle of 45 ( Vitex) ; or, further, the bases are carried out and up till they are horizontal, as in Stachys, Prunella, &c. ; while in other instances this goes so far that the connective grows out into two distinct arms from the summit of the filament, bearing the solitary anther-cells at the tips : in Salvia (fig 227) one of the lobes is abortive, and represented by a petaloid plate. Fig. 227. Fig. 228. o. Fig. 229. Pig. 227. Stamen of Salvia qffldnalis, with a half-anther containing pollen and the other half barren, separated by the bifurcation of the connective from the summit of the filament. Fig. 228. Group of stamens with sinuate anthers, of the male flower of a Gourd. Pig. 229. Stamen of Vaccinium uliginosum, with spur-like appendage and porous anthers. Anther-lobes. The lobes of the anther are commonly oblong ; in the Grasses they are linear ; but they vary with the form of the connective, and are sometimes lunate or reniform. In the Cucurbitaceae they are remarkably convoluted (sinuate) into a flat scroll-like form (tig. 228). Not unfrequently they are attenuated upwards into free points, as in Vaccinium (fig. 229) ; in the Me- lastomaceae the two lobes become confluent into a tubular process at the summit ; while appendages are occasionally met with at the base of the lobes, as in Erica (lig. 230), &c. Anther-loculi. The lobes of most anthers exhibit internally four cells (thecce or loculi) in the early stages of development, each lobe being divided into two by the septum extending from the connec- tive to the suture (fig. 231). The septum (the placentoid of Chatin) is more or less destroyed during the maturation of the pollen in THE ESSENTIAL OKGANS STAMENS. 123 most cases, leaving the anther two-celled, or Ulocular (fig. 232). In some cases the internal substance of the connective is likewise absorbed, producing a true unilocular anther, as in Alchemilla and in Malvaceae. In other cases the four cells are retained perfect, Fig. 230. Fi>. 233. Fig. 230. Stamen of Erica cinerea. Fig. 2-31. Section of an anther, its two lobes still divided into two cells by the septa reaching from the connective to the sutures. Fig. 232. Section of a bilocular anther (the septa have been absorbed). Fig. 233. Stamen of Laurus Persea, having a 4-celled anther with opercular dehiscence, and two lobes at the base of the filament representing divisions of a compound stamen. as in the quadrilocular anthers of Butomus, where they are parallel, and of some Lauraceae, where they become oblique so that the summits are all turned towards the face. The dimidiate unilocular anthers of Gomphrena and Salvia are so called from being only halves of anthers in which one lobe is abortive or suppressed. Anomalous one-celled anthers occur in Poly gala. The unilocular lateral anthers of the diadelphous stamens of Funiariaceae are dimidiate. Dehiscence. When the anthers are mature, the cells or loculi open and discharge the pollen. This dehiscence takes place in different ways ; it may be 'sutured, porous, or opercular. Sutural dehiscence is the opening of the walls by splitting down vertically at the sutures, which may be extrorse, introrse, or lateral (see p. 126). A transverse slit is formed in the unilocular anther of Alchemilla, in Lavandula, and in Lemna. Porous dehiscence is where definite orifices are formed at some point of the wall of the loculus, as at or near the summit in Solanum, Ericaceae (figs. 229, 230), &c. Opercular dehiscence results from the partial separation of a portion of the wall of the loculus, in the form of a kind of lid, as in the Berberry, where the front of each cell splits off at the sides and base, and turns back as if hinged at the top. 124 MORPHOLOGY, OR COMPARATIVE ANATOMY. In the Lauracese (fig. 233) we find either two or four little lids of this kind, opening the two or four cells of the anthers. If the anther he considered the equivalent of a leaf with infolded margins, then the groove "between the two lohes would represent the margins of the leaf; but there is reason to suppose that no such infolding really occurs, but that two pollen-sacs are formed on either side of the connective without any involution of the margin. Stamens of Gymnosperms. The stamens of the Gymnospermia present remarkable conditions, which require separate notice. Among the Coniferee (see that order) the stamens of Pinus constitute the entire male flowers, and are conjoined into male cones, each anther forming a scale of the cone ; they are bract-like plates, bearing on the lower face two parallel anther-lobes (bursting longitudinally or irregularly), beyond which the connective extends more or less as a scale-like process. In Cupressus the form of the anther is excentrically peltate, the lobes, three or four in cumber, standing under the overhanging connective ; and it is similar in Juniperus and Tliuja. In Taxus the peltate connective is more symmetrical, and radiately grooved above, having from three to eight vertical anther-lobes beneath : some authors regard this as a group of monadelphous stamens. In the Cycadaceas (for illustration see that order), where the anthers are scattered in large numbers over the lower face of the scales of the male cones, they occur mostly in the form of groups of four simple anther-lobes, with longitudinal dehiscence and arranged in the form of a cross. These are mostly described as parcels of unilocular anthers. Number of the Stamens. The stamens, taken collectively, present a number of characters, which have received technical names. The number of stamens in a flower is indicated by the terms mon-androus, di-androus, &c. ; when more than twelve exist, the term poly-androus is employed. Upon the number of the stamens the Linnean classification was partly founded. When the number of the stamens is equal to, or some multiple of, the number of petals in the corolla &c., the flower is isostemonous ; when the number is different (as in Scrophulariacese &c.) the flower is anisostemonous. "When there is one whorl of stamens in the normal position, the term haplostemonous is employed; diploste- monous is used where there are two whorls, and obdiplostemonous where there are two rows of stamens, the outer superposed to the petals. Relative length. Two cases of inequality of length of the filaments are distinctly named, viz. the didynamous condition (figs. 234 & 235), when there are two pairs of stamens, one pair longer than the other, characteristic of many irregular Monope- talous flowers (Labiatae, Scrophulariaceae, &c.) ; and tetradynamous THE ESSENTIAL ORGANS STAMENS. 125 (fig. 236), when there are four long stamens and two short ones, characteristic of the Cruciferae. When the stamens are of unequal length in the same flower, or in diiferent flowers of the same species (e. g. Primrose), the condition is called dimorphic, and has reference to the mode of fertilization to be hereafter mentioned. The term included is employed to denote that the stamens do not reach beyond the corolla ; exserted, that they are protruded from it ; while declinate means that the exserted stamens are all curved over to one side. Cohesion, etc. The stamens are subject to apparent confluence or cohesion, like the other organs. If the filaments are only Fig. 234. Fig. 235. Fig. 236. Fig. 234. Corolla of Glechoma, laid open to show the didynamous stamens. Fig. 235. Corolla of Digitalis, laid open to show the didynamous stamens. Df the "" Fig. 236. Tetradynamous stamen lopes being removed. ' the Wallflower surrounding the pistil, the floral enve- partially separated so that they form a tube surrounding the Fig. 238. Fig. 237. ^ Fig. 240. Fig. 239. Fig. 237. Monadelphous stamens of Malva. Fig. 238. Diadelphous stamens of Leguminosse. Fig. 239. Ground-plan of a Papilionaceous flower with diadelphous stamens 9 + 1 (the little circles round the solitary carpel). Fig. 240. Triadelphous or polyadelphous stamens of Hypericum ceffyptiaeum. 126 MORPHOLOGY, OR COMPARATIVE ANATOMY. style (or a column in a staminate flower of a diclinous plant) (fig. 228), the stamens are monadelphous (fig. 237), as in Malvaceae, Camellia, &c. In Fumariaceas they are coherent into two equal parcels, while in many Leguminosae, of ten stamens, nine are united together and one free : these states are called diadelphous (figs. 238 & 239). In Hypericaceae we have triadelphous (fig. 240) and pentadelphous states ; but these, as also the state in Aurantiaceae and various Myrtaceae, are generally denominated polyadelphous, and are instances of branched stamens (p. 120). Syngenesious signifies that the filaments are free, but the anthers coherent (fig. 241), as in Compositse and Lobeliaceae. Gynandrous indicates confluence of stamens and pistils, such as occur in Orchidaceae, Asclepiadaceae, Aristolochia, &c. (fig. 242). These terms, together with those descriptive of adhesion (perigynous, epigynous, &c.), have already been explained, as also the meaning of the words monoecious, dioecious, &c. Fig. 241. Fig. 242. Fig. 243. Pig. 241. Syngenesious stamens of Compositse: a, the anthers surrounding the style as a sheath ; b, the anthers removed and spread out, showing the free filaments. Fig. 242. Section of the lower part of the perianth of Aristolochia, springing from the top of the inferior ovary. In the cavity of the perianth is seen the style, with the adherent anthers upon its sides. Fig. 243. Clavate pollen-mass of Orchis, prolonged below into a caudicle, by which it attaches itself to the rostellum of the stigma. Direction of Anthers. Usually what is called the face of the anther is turned inwards towards the ovary, and it is then said to be introrse : but sometimes the reverse state exists, and the face is turned towards the floral envelopes, as in Ranunculus, Colchicum, &c., when the anthers are termed eoctrorse. Frequently the direc- tion changes during the expansion of the flower, as in versatile anthers. (See also under Dehiscence, p. 123.) Pollen. The pollen, discharged from the anthers, consists in almost all cases of a fine powder composed of microscopic grains or cells corresponding to the microspores of the higher Cryptogams; THE ESSENTIAL ORGANS THE PISTIL. 127 the form and appearance of the grains vary much, and will be spoken of hereafter. The pollen of the Asclepiadaceae and Or- chidaceae, however, has a great peculiarity, in remaining perma- nently coherent into masses, often of a waxy character. In Orchidaceae the pollen-masses or pollinia are either single in each loculus of the anther (as they are in Asclepiadaceae), and then often furnished, as in Orchis &c., with a stalk-like process, called the caudicle (fig. 243), terminating in a gland-like base (retina- culum), by which they readily adhere to the stigma or to foreign bodies, such as insects ; or the pollinia are two or four in each loculus, and devoid of a caudicle ; sometimes the pollinia are nume- rous, and form merely a loose granular mass. The external characters of the pollen-graius, their structure, and sub- sequent history will be treated of in the Third Part of this work, as they belong to the microscopic anatomy and the Physiology of Plants. The form of the pollen-grains is generally constant in the same plant ; but great variations are often found within the limits of Natural Orders and sometimes in the same genus, so that, excepting the Orchidacese and Asclepiadaceae, and a few other groups, they are not to be relied on as affording any very useful characters in Systematic Botany. Their size, form, and numbers are apparently in relation to their mode of dispersion by the wind or by insects. Fig. 244. Fig. 245. Fig. 246. The Gyncecium or Pistil. Carpels. The central essential organs of flowers, composing the pistil, consist, like the outer parts, of phyllomes or modified leaves ; these constituent leaves are called carpels. The peculiar character of a carpel is, that it produces ovules, the rudiments of the seeds usually upon the margins, but occasionally on other parts of the internal surface. In the G-ym- nospermia these ovules are deve- loped upon the edges or surface of expanded carpels. In the An- giospermia, comprehending the great majority of Flowering plants, the carpels are folded up, Fig. 244. simple pistil of Prunu*, consisting either singly (fig. 244) or collec- ^.*t&S! a> the ovary '' c> the tively, with the margins turned Fig. 245. The same, 'opened, to show the in so as to place the ovules in the F^^^^SS'of the carpel of interior Of a hollow Case. The Prunus, showing that the ovule arises Case thus formed, enclosin the --enta at the confluent margins 128 MOKPHOLOGY, OK COMPARATIVE ANATOMY. ovules, is called the ovary (figs. 244 & 245, a, a') ; the upper part of the carpel is frequently attenuated into a slender column called the style (c), at the extremity of which is a terminal glandular orifice or stigma (b, 6), the borders of which are often more or less thick- ened or developed into processes of various kinds. Sometimes the stylar prolongation does not exist ; and then the stigma is sessile upon the ovary. The pistils are undoubtedly formed of carpels (carpellary leaves) in most instances. In some cases they appear to be formed by an expansion of the receptacle or axis of the flower, as in Typha and Naias ; while their structure and venation are in some cases neither those of a leaf nor of an axis, but, as it were, intermediate between the two. Phyllody- The foundations of the doctrine that the carpels are metamorphosed leaves rest upon a very wide basis. The following observations include examples of some of the most important classes of proofs : 1 . The carpel ordinarily possesses more of the character of a true leaf, as regards texture and colour, than the stamens or petals approaching to the sepals, which we have seen to pass insensibly through the bracts into ordinary leaves. The resemblance is sometimes heightened during the development of the fruit, as we see in the legumes of some species of Cassia, and still more in the bladder-like pod of Coluteu. 2. Abundant examples exist of the substitution of petals for stamens and pistils in abnormal flowers ; and an almost equally common monstrosity consists in the substitution of isolated stunted green leaves for the carpels. In the Double Cherry, cultivated in shrubberies for the sake of its blossom, the stamens are generally replaced by petals, while the centre of the flower is mostly occupied by a pair of green leaves. (The single, fertile Cherry frequently has two pistils developed instead of one.) In a common monstrosity of the White Clover, the pod is usually replaced by a more or less perfect green leaf 5 the same occurs in garden Roses, where tufts of green leaves replace the pistils ; and, in fact, examples of this kind are very abundant. 3. The more or less stunted green leaves which represent the carpels in the above-mentioned monsters frequently exhibit on their margins structures varying in character from almost perfect rudiments of ovules to cellular papillae and leafy lobules. This is observed in the monstrous Clover, and has been especially remarked also in monstrous flowers of cultivated (forced) Tulips, of various Cruci- ferae, Ranunculacese, Scrophulariaceae, &c. The abnormal conditions in these cases are analogous to the normal condition in Coniferse and Cyca- deae, the Gymnosperms, where the ovules are always naked on open carpels. 4. The production of ovules on the margins of carpels is analo- gous to what is seen in the development of adventitious buds on vegetative leaves, as in Bryophyttum, &c. Such buds, however, occur sometimes on the upper surface of leaves ; and we find some carpels, as in Nyrnphcea, Butomus, &c., with ovules developed more or less extensively over the in- ternal face. 5. The disposition or arrangement of the vascular bundles is usually that of the leaf, not that of the branch. 6. The structure, de- velopment, and mode of growth generally are those of the leaf and not of the branch. Exceptions, however, occur to the last two statements. THE ESSENTIAL OEGANS THE PISTIL. 129 Placenta, Sutures. The region of the carpel whence the ovules arise is called the placenta ; and when in Angiospermous flowers the placentas are clearly and distinctly marginal, they must of course be double, from the meeting of the two edges ; the same is true of the stigmatic surfaces. The line of union of the margins of carpels constitutes the ventral suture : the line corresponding to the midrib of the carpellary leaf is the dorsal suture. An excellent example of a simple typical pistil formed of a single carpel is afforded by the legume of the LeguminosEe ; as, for instance, in the Sweet-pea, where we find the ovary, with a ventral and dorsal suture, narrowed above into a short slender style, terminating in a slightly enlarged stigma. When we open the ovary, in the way it is broken in shelling peas for the table, we find the plaeentary margins separated at the ventral suture, each carrying away half the ovules, demonstrating clearly the double character of the placenta. Modifications. Pistils differ extremely in different plants, from dissimilarity in the number, degree, and mode of union of the car- pels, as well as in the relative degree of development of the different regions of the carpels, and with these may be associated the pecu- liarities arising from adhesion of the outer circles. Numerical relation. The number of carpels is most frequently less than that of the organs in the outer whorls, being very fre- quently reduced to two, and often to one. On the other hand, multiplication of the number is met with in certain Orders, where the receptacle is generally more or less enlarged to make room for them. A large portion of the Gamopetalous Dicotyledons, with a quinary ar- rangement of the calyx and corolla, and often of the stamens, have dicarpel- lary pistils, as Gentianacese, Apocynaceee, Solanacege, &c. Leguminosse with quinary flowers have a solitary carpel. The agreement of the number of carpels with the other organs is almost universal in the ternary flowers of Monocotyledons, as in Liliaceae, Iridacese, Orchidacese, &c. Multiplica- tion of carpels is especially frequent in the Ranunculaceae, Magnoliaceae, and some other Orders. Apocarpous Pistil. In the typical pistil above described, and which really exists in Leguminosae (for instance), the organ, being composed of one carpel only, is simple. A carpel may be solitary in a flower, from suppression of the remainder of the circle ; or there may be in the same flower several distinct, i. e. uncombined, carpels, as in Larkspur, Aconite, Magnolia, Ranunculus, Fragaria, &c. : in these cases the terms multiple pistils is occasionally used, or we may say carpels distinct, three, five, or numerous, as the case may be. The term apocarpous pistil includes both the solitary carpel and the multiple pistils. In the case of multiple pistils, 130 MORPHOLOGY, OR COMPARATIVE ANATOMY. where the receptacle is flat the carpels are in whorls; but if the receptacle is elongated the carpels are arranged spirally, as in Magnolia. Syncarpous Pistil. Where, as very frequently happens, the carpels cohere together, as the stamens do in the condition called monadelphous, a syncarpous or compound pistil is formed ; and as the carpels occupy the apex of the receptacle, they do not form an open organ, like the tube of filaments in Malva for example, but a closed case, appearing externally like a solid body, mostly with ridges and grooves on the outside, indicating its compound nature. The union varies very much in degree ; even in multiple pistils we find the carpels sometimes cohering strongly while young, and separated only as the seeds ripen ; and in true compound pistils the union does not always extend to the summit of the ovarian region, as we observe in the Saxifragaceae, where the apices of the ovaries diverge. More frequently the ovarian regions are firmly coherent ; and then the styles may be wholly free Pink, Silene (fig. 173), Hypericum, &c. ; or united part of the way up, as in some Malvaceae (fig. 247) ; or entirely, but with the stigmas distinct, as in Geranium, &c. ; or the stigmas may also be con- fluent (Primulaceae, Solanacese, &c.). Sometimes, however, the styles or stigmas exhibit the reverse condition, and are split into two parts, as in the styles of Drosera, Euphorbia, &c. Adhesion. The conditions arising from adhesion or want of se- paration have been referred to already, under the names of superior or inferior calyx or ovary. The condition depends on this circum- stance whether the vascular bundles for the carpellary whorl are detached at once from the axis, or whether they are held together by a sheath of cellular tissue for a time before becoming detached. They are always associated with cohesion when more than one carpel exists. The styles, when the ovary is inferior, are either coherent, as in Iridaceae (fig. 260), or distinct, as in the Umbelliferae (fig. 172) and Rubia- ceae. In Saxifraga (fig. 171), and in some other cases, the ovary is half- inferior. When the stamens are consolidated with the pistil, the gynan- drous condition is produced. In Orchidaceae the filaments are inseparable from the style, forming a column surmounting the ovary; in Asclepia- daceae the anthers adhere to the summit of the free compound style ; in AristolochiaceaB the filaments apparently adhere to the base of the com- pound style (fig. 242). (See under Aristolochiacese.) Compound pistils are sometimes smooth and even on the out- side, showing no sign of their compound nature, as in Primula, &c. ; in other cases they exhibit more or less deep furrows at the lines of junction, sometimes dividing them into lobes. But the internal structure of the ovary generally indicates the number of carpels entering into its composition very plainly. THE ESSENTIAL ORGANS THE PISTIL. 131 Multilocular Ovary Placentation. When the carpels are firmly and organically united by the surfaces of contact, we obtain the type of a compound multilocular or many-celled ovary (fig. 248)*. Fig. 247. 8 Fig. 248. Fig. 249. Fig. 250. Fig. 251. Multilocular compound ovaries. Pig. 247. Ovary, styles, and stigmas of Malva. Fig. 249. 3-celled ovary of Lilium. Fig. 248. 2-celled ovary of Scrophulariaceae. Fig. 250. 3-celled ovary of Commelyna. Fig. 251. 4-celled ovary of Fuchsia. In these cases the sides of the constituent carpels are folded in- wards, so as to meet in the centre, and thus form partitions be- tween the chambers or loculi. The placental margins of the infolded carpels are retroflexed, constituting central or axile pla- centas. The partitions are called dissepiments, and are necessarily double, being composed of the conjoined side-walls of contiguous carpels. In such ovaries the dorsal sutures are in the outer wall, while the ventral sutures meet in the centre (fig. 248). Examples of this kind of ovary are furnished by Liliacese (fig. 249) and many other Monocotyledonous orders, by Ericaceae, Solanaceee, Scro- phulariaceae, &c. In some cases the ventral sutures and placentas are not directly confluent, but adhere to a central prolongation of the receptacle running up between them, as in Geraniacese (fig. 276), &c. False or spurious dissepiments occur occasionally both in compound and simple ovaries, consisting of membranes or plates developed from the pla- centa or from the dorsal suture, and subdividing the originally single cavity formed by individual carpels. Thus in Linum the 5-carpellary ovary would have five loculi, were it not that a spurious dissepiment extends inwards from the dorsal suture to the placenta in each loculus, and divides the ovary into ten loculi. In Astragalus (fig. 252) the simple ovary is divided by" the inflexion of the dorsal suture, and in Datura Stramonium a false septum is formed in each of the loculi of the ovary. The transverse false septa found in various Leguminous ovaries, such as Cathartocarpus &c., are likewise outgrowths from the walls of the carpel. Unilocular compound Ovary. If the carpels are not inflexed, but cohere by their contiguous margins, they form a hollow case * The terra cell, though commonly used, is objectionable, as leading to confu- sion with the cells which make up the tissues of the plant. On this account the word loculus is preferable. 132 MORPHOLOGY, OE COMPARATIVE ANATOMY. with only a single cavity ; and as the lines of junction of the car- pels are on the outer wall, the placentas must stand inside those lines ; in this way is formed a unilocular compound ovary with parietal placentas (figs. 253-255). There are no dissepiments : and the ventral sutures, alternating on the outer walls with the dorsal sutures, are, in such cases, like the placentas within, formed of the confluent margins of two different carpels instead of those of the same carpel. We find almost every possible degree of transition between the parietal and the axile placentas, according as the placentiferous margins project more or less into the interior of the ovary. True parietal placentas are found in Violaceae (fig. 254), Gentianacese (fig. 253), Cistaceae (fig. 255), &c. In Papaver we have the margins turned-in so as nearly to reach the Fig. 252. Fig. 253. Fig. 254. Fig. 255. Fig. 252. a, legume of Asfragalus ; 6, cross section, showing a false dissepiment formed by the inflexion of the suture. Unilocular compound ovaries. Fig. 253. Ovary of Gentianaceae. Fig 254. Ovary of Viola. Fig. 255. Ovary of Cistus. centre (as imperfect dissepiments) ; in some Hypericacese (If. araveolens) the originally axile placentas become parietal by separation during the ripening of the fruit, while in Cucurbitacese the originally distinctly parietal, although greatly infiexed, margins ultimately cohere so as to form an axile placenta. In Cruciferse we have an anomalous condition, where there are two double parietal placentas, but from the central line of each projects a plate passing across the cavity and forming 'a kind of spurious septum, called a replum ; so that each cell contains only the two half-placentas formed by its own margins. Free central Placentas. In some Orders, where the walls are as in the unilocular compound ovaries above described, the placentas are found as a free column or expanded mass in the centre of the common cavity. This forms the compound unilocular ovary with a free central placenta. In Primulacese, Santalacea), and some other Orders, where this kind of placentation occurs, the placentas are free from their very earliest state, and are seen to be direct pro- longations of the receptacle or axis within the carpels. THE ESSENTIAL ORGANS THE PISTIL. 133 The appearance of a free central placenta is presented in Caryophyllaceas by the obliteration of the partitions which pass between the outer walls and tne centre of the carpels. By Baillon a peculiar process from the placentas over the ovules is called the obturator ; it is very conspicuous in Euphorbiacese. Various modes of Placentation. The placentas have been spoken of as double, on account of their origin : where only one ovule exists in a cell, it is assumed that one at least is suppressed ; but this other is not unfrequently developed in the Cherry, Almond, &c. (causing the double kernels). In Leguminosse the double pla- cental base is so narrow that the ovules are placed one over another, and form what appears like a single line. In Larkspur, Columbine, &c. there is a distinct double row ; in many cases each placenta has a double row of ovules ; while axile placentas are frequently thick- ened and enlarged, so as to bear a large collection of ovules, closely packed. In Papaver the ovules exist all over the imperfect septa ; in Nymphcea all over the sides of the dissepiments, and not at the margins ; in Butomus all over the inside of the carpels, &c. Where ovules arise from the base of a carpel, either singly or in larger numbers, the placentation is called basilar ; it is in most cases a slight modification of free central. The Style. The styles require no particular notice beyond the statements already made, except in regard to their irregular posi- tion in some cases. The style is really produced from the apex of the carpel ; but in various Rosaceae the ovarian part of the struc- ture grows faster and so disproportionately that it leaves the style on one side (lateral} (Frag aria, tig. 256), and sometimes even grows out and up so much that the style, then called basilar, seems to arise from the base (Alchemilla). In the Boragiuacese and Labiates (fig. 205) a similar condition of the styles exists in a compound pistil ; the styles in these plants are confluent, and arise as a solitary column from a deep depression in the centre of the 4-lobed ovary, com- municating with the cells near the base as in the Rosaceaa referred to. These styles of Labiatae are called yynobasic. A dimorphic condition of the pistil especially affecting the length of the style is met with in some flowers, e. g. Primroses, some of which have short, others long styles, as explained under Fertilization. The Stigma. The stigma is either situated at the end of the style or, where this structure is wanting, it is sessile on the ovary. Instances of sessile stigmas are furnished by the compound pistils of Papaver (fig. 262), iNymphaeaceae, &c., where the stigmas form radiating ridges on the top of the flattened ovaries. The elongated stigmatic surfaces on the inner sides of the beak-like points of the simple pistils of Hanuncuhis and allied plants are almost to be 134 MOBPHOLOGY, OR COMPAEATIVE ANATOMY. called sessile stigmas ; and these form a transition to the long stigmatic ridges which extend down the inner sides of the styles Fig. 257. Fig. 258. Fig. 256. Fig. 256. Lateral style of Fragaria. Fig. 257. Pistil of a Grass, with feathery stigmas. Fig. 258. Pistil of a Grass, with penicillate stigmas. Fig. 259. Stigmas of Crocus. of most Caryophyllaceae. When it is properly terminal it exhibits a great variety of conditions, both as regards composition and structure. Its form is sometimes associated with the method of fertilization by insects or otherwise, as afterwards explained. Fig. 260. Fig. 261. Fig. 262. Fig. 260. Vertical section of flower of Iris, the style terminating in erect petaloid stigmatic lobes. Fig. 261. Female flower of Cucumis sativus, with a short style and lobed stigma. Fig. 262. Ovary of Papaver, with radiate sessile stigmas. It has been stated that the styles of compound ovaries are often distinct ; the stigmas are also often distinct on compound styles, indicating the THE ESSENTIAL ORGANS THE PISTIL. 135 number of constituent carpels. Moreover these distinct stigmas are occa- sionally split down into two arms (stigmata bicruria), corresponding to the two placentas below : the one-celled ovary of Grasses and Composite (fig. 264) bears a two-armed stigma ; and the* stigmas of the compound ovaries of Euphorbia and some Droserce are double the number of the carpels. Sometimes the distinct arms of different carpels cohere, and form stigmas equal in number to the placentas, but alternating with them. Form and Position. Stigmas, simple or compound, when distinct, are either terminal or lateral : in the latter case the stigmatic sur- face is on the ventral side. Their form is generally slender and thread-like, with a glandular stigmatic surface ; but in the Grasses the stigmas are feathery (fig. 257) or penicillate (fig. 258) ; in the Fig. 263. Fig. 264. Fig. 265. Fig. 266. Fig. 267. Fig. 263. Flower of Luzula, with one style and filiform stigmas. " " -" T- " "" " illose surfaces. yules at the base. Fig. 267. Young female blossom of Juniperus, with the front carpel remoyed, showing the naked ovules. Iridaceae they are petaloid (fig. 259) or very much enlarged, as in Iris (fig. 260) ; and in other cases they are capitate (fig. 256), loled (fig. 261), peltate, radiate (fig. 262), filiform (fig. 263), linear (fig. 264), &c. In Leguminosae the stigmatic surface of the simple style is lateral (fig. 265). The orifice of stigmas leading to the canal of the style is more or less filled by the glandular and capillary processes which clothe their sur- faces ; and, indeed, to the naked eye, the canal of the style does not appear permeable. Gymnospermous Pistils. The pistil of Gymnospermous plants consists of scales or open carpels, collected into cone-s, bearing exposed 136 MORPHOLOGY, OE COMPARATIVE ANATOMY. ovules, so that no representative of the stylar or stigmatic regions exists here. Among the Oonifene, Pinus and its allies have scale- like carpels with a pair of ovules on the upper surface, at the base (fig. 266) ; the structure is analogous, although the form of the scale differs, in Thuja ; the Cypress has peltate scales, with nume- rous ovules ; in Juniperus each of the three scales has only one (tig. 267). In Taxus the ovule is a solitary structure, a kind of free ovule, growing out from the apex of a small cone formed of barren scales. In the Cycadacese, Cycas has large leaf -like car- pels, with numerous marginal ovules; Zamia has peltate scales, more like Cupressus, with the ovules pendent from the thickened summit. By some authors what is above described as a naked ovule is thought to be an ovary (see under Gynmosperms). Sect. 10. PRODUCTS OF THE ESSENTIAL ORGANS OF FLOWERS. Ovules. Ovules are the rudiments of seeds, and arise from the placentas situated in the ovaries of Angiospermous plants (figs. 253-255), and on the margins or surface of the open carpels of Grymnospermia (figs. 266, 267). They originate as cellular papillae at an early stage of development of the ovary, and acquire a definite form and structure by the time the flower expands. Ovules are by some observers regarded, in part at least, as a kind of bud ; for not only do they appear in the positions occupied by adventi- tious buds on vegetative leaves, as in BryophyUwn, but abnormal leaf-like carpels often bear bulb-like structures and foliaceous lobes, in place of the ovules, on their free margins. By others they are considered, at least so far as their outer coat is concerned, to be modified leaves or portions of such leaf. In most cases they originate from the margins or surface of a carpellary leaf; but in some cases they originate from the axis (free central placentation), and are then either lateral or terminal, as in Piperaceae, where the end of the axis becomes the nucleus of the ovule. Other illustrations are afforded by Taxus and Polygonum. Number. The number of ovules in the ovary, or in one cell of a compound ovary, varies between wide limits. Thus the ovule is solitary in the simple ovaries of Ranunculus, Prunus (fig. 245), &c., in the compound ovaries of Polygonaceae &c., and in each cell of the bilocular ovaries of the Umbelliferse &c. ; the number is still small and definite in the simple pistils of many Leguminosae, in the cells of the compound ovary of Quercus, &c. ; in a very large pro- portion of compound ovaries, whether unilocular or multilocular, the ovules are very numerous on each placental surface, and they are termed indefinite, as in Primula, Papaver, &c. &c. THE OVULE. 137 Funiculus. A fully developed ovule is usually attached to the placenta by a short stalk, called the funiculus, podosperm, or umbi- lical cord ; where this stalk does not exist, the ovule is sessile ; in' a few cases the funiculus is very much elongated (Plumbaginaceae). Relative Position. Special terms are used to indicate the posi- tion occupied by ovules in the ovary, and more particularly their direction. If the placenta is at the base of the ovary, and the ovule, springing from that situation, points upward, as in Polygo- naceae and Composite, the ovule is called erect ; if it is attached at the summit, and hangs straight down, as in the Birch, Dipsaceae, &c., it is suspended when the placenta is central or parietal, the ovule may turn upwards and be ascending, may point straight out- wards or inwards and be horizontal, or may turn downwards and be pendulous. In Plumbaginaceae the ovule is suspended from the end of a long funiculus, which arises from the base of the ovary as in the erect condition. Where numerous ovules exist on a central placenta, it is very common to find the upper ones ascending, the middle horizontal, and the lower pendulous, so that the direction becomes indefinite. Parts of an Ovule. The ovule arises from the placenta as a conical papilla, which soon becomes elongated into an oval body, the nucleus, raised on the stalk or funiculus. By the time the flower opens, the nucleus (figs. 268270, a) generally becomes covered up by the coats or envelopes, which originate as circular ridges from the point where the funiculus is attached, and gradually grow up over the nucleus. The coats do not completely close in the ovule, but leave an opening at its summit, called the micropyle or foramen (figs. 268-270, ft). The base of the nucleus, where the coats arise, is called the clialaza ; the internal coat (the secundine of Mirbel) is the first formed ; it is denominated the integumentum internum, or the tegmen ; where only one coat exists, it is called the integumentum simplex. The outer coat, which grows up after the inner (the primine of Mirbel), is called the integumentum eocternum, or sometimes the testa. Sometimes, as in Welwitscliia, the primine is prolonged beyond the apex of the .ovule in the form of a tube greatly resembling a style (see under Grnetaceae). The orifice named the micropyle forms a canal passing through both coats down to the point of the nucleus ; and the portions passing through the outer and inner integuments are often called, respectively, the exostome and endostome. The point where the seed afterwards breaks away from the f uuiculus is marked by a scar, which is called the hilum. In the Mistletoe the nucleus is naked, no coats being formed ; in many cases there is only one coat ; most ovules of Monocotyledons have two. 138 MOEPHOLOGY, OE COMPAEATITE ANATOMY. The coats of the ovule are usually regarded as foliar in their nature, the nucleus as axial by others as a " trichoine " or superficial emergence from the foliar coat of the ovule. The nucleus may be regarded as the equivalent of a niacrosporangium among higher Cryptogams. The above is a description of the ovule of what may be called the normal form, such as we find in Polygonum, &c. : where the nucleus is straight and the micropyle is at the end opposite the attachment of the funiculus, and the chalaza next the placenta, such an ovule is called straight, or, more technically, atropous or orthotropous (fig. 268). Inversion and Curvation of the Ovules. Very frequently the funiculus grows in a state of confluence with the outer integu- ment, during the development of the ovule, so as to push up the base of the nucleus until it is completely inverted (fig. 269), and Fig. 269. Fig. 270. c - WVS^t Diagrammatic vertical sections of ovules : a, the nucleus; b, the micropyle; c, chalaza; d, raphe. Fig. 268. An atropous or orthotropous ovule. Pig. 269. An anatropous ovule. Fig. 270. A campylotropous ovule. the micropyle (b) points to the placenta, while the chalaza (c) is at the opposite end, the nucleus being straight as in orthotropous ovules : this is the inverted or anatropous condition ( Composite, Liliaceae, &c.) ; and as the funiculus is confluent with the outer coat, the hilum (the external point of junction of the funiculus with the body of the ovule) is left in its original position, and therefore close beside the inverted micropyle. The adherent portion of the funiculus often forms a kind of ridge extending from the hilum to the chalaza : this is termed the raphe (fig. 269, d). Other ovules become anatropous not by reflexion, but by unequal growth. The inverted ovule is a straight ovule with a long funiculus confluent with the outer coat: in Fumana (Cistacese) the real condition often actually illustrates this ; and in seeds formed from anatropous ovules the raphe sometimes separates {Zygophyllum, Willdenovia). The position of the raphe with reference to the ovule varies in different cases ; sometimes it is ventral, or on the side of the ovule nearest to the placenta, sometimes dorsal, at other times lateral. A curved or campylotropous ovule (fig. 270) is formed by the THE FETJIT. 139 bending over of the nucleus upon itself in the form of the letter U, carrying the micropyle (b) over, but leaving the chalaza in its natural vicinity to the hilum. There is no raphe in such ovules. Another condition more rarely met with is the horizontal or amphitropous ovule, intermediate between straight and inverted, the adherent funiculus pushing up the chalaza at one end, while the micropyle descends in a corresponding degree, until the axis of the ovule becomes horizontal, and parallel with instead of at right angles to the placenta. In the first instance all ovules are straight, but they mostly become curved during the course of their development. The Embryo-sac. At the time when the flower expands, there exists a more or less considerable sac or cavity excavated in the substance of the nucleus, the upper end of which sac is situated just within the apex. This cavity is called the embryo-sac, being really a sac or bag with a proper wall, within which the embryo or rudiment of the future plant is developed after fecundation. It is analogous to the macrospore of Cryptogamous plants. The phenomena of fecundation and of the early development of the embryo, together with the minutiae of the anatomy of ovules, are reserved for the Physiological part of this work. The further morphological peculiarities of the ovular structures will fall best under the head of the seed or completed product, previously to examining which we must follow out the ultimate history of the pistils and associated organs forming the fruit, in which the ripe seeds are found. The Fruit. The fertilization of the ovules usually takes place soon after the opening of the flowers, or sometimes even before their expansion. During the subsequent changes by which the ovules are converted into seeds, the ovary (and occasionally other parts of the flower) undergoes further development, and becomes what is technically called the fruit or seed-vessel. Changes during the ripening of the Fruit. Generally the stamens and corolla, and not unfrequently the calyx also, fall away or wither up after fertilization, and the styles, with the stigmas, mostly disappear ; but the style sometimes persists, and even undergoes enlargement, forming a kind of beak or tail to the fruit, especially in simple fruits formed of one carpel (Ranunculus, Clematis, Geum, fig. 289, &c.). The calyx, when inferior, remains in many cases as a loose cup or envelope surrounding the fruit (as in Labiatse, many Solauacese, fig. 184, &c.) ; or, when superior, its segments, enlarged or withered, form a kind of crown to the fruit (Com- positee, Canipanulacea3, &c., fig. 283), and the tubes of adherent calyces always enter into the composition of the inferior fruits (figs. 298-303). In some cases the calyx and the corolla, in other cases the receptacle, 140 MORPHOLOGY, OB COMPARATIVE ANATOMY. become blended with the ovary or ovaries to form the fruit ; and a still more complex kind of fruit is formed by all the flowers of an inflo- rescence becoming conjoined into a common structure during the ripening of the seed, so as to form a collective fruit, such as occurs in the Pine- apple (fig. 308), Mulberry (fig. 307), Bread-fruit, the Fig (fig. 306), cones of Firs, &c. Considered as developments of the carpels alone, many fruits in their mature condition depart widely in appearance from the ovaries from which they are produced, the morphology of fruits exhibiting perhaps more remarkable cases of actual metamorphosis than any other parts of plants. Hence it is often difficult to judge from a fruit what kind of pistil the flower has possessed, and the structure of fruits can only be understood by a study of their progressive development from the imma- ture to the mature condition. The most important source of change is the suppression of chambers or loculi of the ovary, together with the abortion of ovules. Thus the flower of the Birch has a two-celled ovary with one ovule in each cell ; but one cell with its ovule is constantly abortive and almost entirely disappears in Fig. 271. Fig. 272. Fig. 271. Female flower of the Oak: a, vertical section; b, cross section. Fig. 272. Fruit of the Lime (Tilia) : a, entire ; b, cross section. the fruit. In the female flower of the Oak and hazel-nut there are three cells, each with two ovules (tig. 271) ; but only one cell is found in the ripe fruit, and this is filled by one solitary remaining seed, as we find in the Acorn or nut. In the Lime there are several cells in the ovary, but gene- rally all but one are obliterated in the fruit (fig. 272) ; and similar cases are by no means uncommon. In these cases the dissepiments, called in the fruit septa, are not broken down, but pushed to one side and obliterated by the pressure exercised by the developed seed. On the other hand spurious partitions are sometimes formed, as in Datura Stramonium, which has a four-celled fruit derived from a two- celled ovary : and in the pods of Legumiiiosae cross partitions are often produced between the seeds. The original conditions are frequently still further concealed by the alterations in the texture of the coverings of the fruit, next to be de- scribed. The Pericarp. The " wall " of the fruit is the substance formed from the carpels, or (when present) from the other component THE PEUIT. 141 structures. It constitutes the case enclosing the ripe seed or seeds, and is called the pericarp. The pericarp is of very different structure in different fruits. When the fruit is mature, it may be dry, membranous, leathery (coriaceous), ivoody, or succulent ; or it may be succulent externally and woody within, or succulent in- ternally and woody or leathery outside. The ripe pods of common Peas afford examples of a dry membranous pericarp ; the Flags (Iris) have a leathery pericarp ; the common Hazel- nut &c. have a woody pericarp. The pericarps of the Grape and the Gooseberry are succulent or baccate. The Plum, Cherry, &c. are succu- lent, externally and woody within (drupaceous) ; the Orange, the Pome- granate, the Pumpkin, &c. are succulent within and leathery or horny outside. When the pericarp is uniformly membranous or woody, without dis- tinction of layers, no subdivisional terms are applied to it. The same holds good in respect to the simple succulent pericarp of such fruits as the Grape and Gooseberry. When there is a distinction into layers, formed by a gradual alteration of the texture of the inner and outer parts during maturation, we distinguish between an epicarp and an endocarp orpyrene as, for example, in the Plum, Cherry, Walnut, &c., where there is a suc- culent epicarp, and a woody endocarp forming the " stone ; " the l( core " of the Apple is a membranous endocarp. When a fruit, such as the Orange, Pomegranate, Litchi, &c., is firm externally, with a leathery or woody epicarp and a succulent endocarp, the latter is generally derived from development from the placental regions. In common " stone-fruits " the two regions are often distinguished by the names sarcocarp (or pulp) and putamen orpyrene. In the Date-Palm (fig. 280) the " stone " consists of the albuminous seed, which is invested by a succulent pericarp. In other Palms, such as Areca, the pericarp is fibrous. In hard-rinded suc- culent fruits we have an internal sarcocarp enclosed by a cortex or rind. Many authors, following De Candolle, divide the pericarp into epicarp, mesocarp, and endocarp. It may be observed here that the distinction between endocarp and epicarp, in the common stone-fruits, arises entirely during the ripening of the fruit ; the two regions are originally alike and undistinguishable ; it is well known that the easy separation of the pulp from the stone is a sign of ripeness. Dehiscence of Fruit. Some fruits, more particularly the succu- lent kinds, but also many dry fruits, do not burst to discharge their seed or seeds when ripe ; these are called indeJiiscent fruits. The pericarp rots away, or is broken irregularly or perforated when the seed germinates. Most dry fruits, more particularly those formed of more than one carpel, burst open or separate into pieces in a regular manner when mature, and are consequently dehiscent. Dehiscence takes place generally (1) by the separation or splitting of the sutures of the carpels in a vertical direction, or (2) by the disso- ciation of coherent carpels, or (3) by both together. The parts which 142 MOEPHOLOGT, OR COMPARATIVE ANATOMY. separate in the first way are called valves ; and this mode of burst- ing is termed sutured or valvular dehiscence. The separated carpels in the second mode are called cocci if they do not open as explained in a subsequent paragraph. Sometimes the valves only separate for a certain distance from the summit, forming teeth (fig. 273). In a few cases the dehiscence is porous ; in others the upper end of the fruit falls off like a lid, by transverse or circumscissile dehis- cence (fig. 274). Fig. 273. Fig. 274. Fig. 275. F''g. 273. Burst capsule of Cerastium. Fig. 274 Capsule of Anagallis (sometimes called a pyxis), opening by circumscissile dehis- cence. Pig. 275. Burst fruit of Illieium (Star Anise). Valvular Dehiscence. When the dehiscence is valvular the fruit is named bi-, tri-, multivalvular according to the number of valves or pieces into which it splits. This mode of dehiscence is subject to several modifications, according as the splitting takes place through the dorsal or through the ventral suture, or through both at the same time. It is still further complicated by the cir- cumstance that the placentas sometimes remain attached to the valves, while at other times they break away from, the valves, as in the condition called septifragal. A few examples may be here given of the various modes in which valvular dehiscence is effected; and the student will find the subject far more readily intelligible if he refer to some collection of seed-vessels where the fruits are correctly named. In the case of simple or of apocarpous fruits, there is no partition or dissepiment, the cavity being simple ; in such cases valvular dehiscence takes place : a, through the ventral suture, as in the Columbine (Aquilecjia}, the Star Anise (Illieium, fig. 275) ; or, /3, through the dorsal suture, as in Magnolia ; or, y, through both sutures at the same time, as in the pod of the Pea and other Leguminous plants (fig. 286). In this latter case there are two valves, but only a single carpel. In unilocular syncarpous fruits, where the compound carpels cohere by their edges which are not infolded, dehiscence takes place : a, through the ventral sutures, when the placentas are found on the margins of the valves, as in Gentians (fig. 253), each valve in this case representing a carpel ; /3, THE FEUIT. 143 through the dorsal sutures, when the placentas will be found in the middle of the valves, as in the Violet (fig. 254). In such fruits each valve consists of two half-carpels combined. In the Orchidacere the capsules dehisce in the manner last described, with this further peculiarity that the valves, bearing the placentas in the middle, separate from the midribs or dorsal sutures, leaving these latter attached together at the top, and thus forming an open framework supporting the remains of the perianth. In multilocular syncarpous fruits, where the sides and margins of the component carpels are infolded, so as to form partitions or dissepiments, the dehiscence is likewise through the dorsal, or ventral, or through both sutures ; thus dehiscence takes place : a, locuUcidaUy, through the dorsal sutures, so as to open the loculus or cavity of the carpel from behind ; each valve in this case represents two half-carpels (figs. 277, 278) ; or, /3, septicidally , through the septa, so as to isolate the previously combined carpels (fig. 276). Each segment in this case represents an entire carpel. Fig. 276. Fig. 277. Fig. 278. Fig. 27fi. Eipe fruit of Geranium, the tailed cocci separating elastically from the carpophore. Fig. 277. Burst capsule of Iri*, with loculicidal dehiscence. Fig. 278. The same in cross section. Septicidal and loculicidal dehiscence may occur in the same fruit, as in the Foxglove (Digitalis), the capsule of which first divides into its constituent carpels septicidally, and afterwards each carpel splits loculi- cidally into two valves ; the four valves so produced represent each a half-carpel. Both the loculicidal and septicidal modes of dehiscence are sometimes associated with wlmt is termed septifrayal dehiscence. This occurs when the septa or partitions bearing the placentas are broken across ; the effect of this is that the valves break away from the placentas, leaving part or the whole of the latter standing in the centre of the fruit on a kind of column, as in Andromeda, Convolvuhis, Rhododendron, &c. Septifragal dehiscence takes place by itself in the siliques or pods of Crucifera3, where the valves separate from the parietal placentas, leaving them in the centra supporting the ovules (figs. 295 & 296). Schizocarps, In some instances, as in Galium, the carpels separate one from the other without opening. In such a case the term schizocarp is employed to designate the whole fruit, while its component carpels are 144 MOEPHOLOGY, OE COMPAEATITE ANATOMY. called coed, or where there are two, as in Umbellifers, mericarps (fig. 300). More frequently the carpels not only separate septicidally but each one bursts, through the dorsal suture, as in Geranium (tig. 276) ; or through the ventral suture, as in Cokhicum. Dehiscence by teeth only differs from that by valves in the smaller degree of separation. The fruits or seed-vessels of Caryophyllaceee dehisce by teeth. Sometimes the teeth are equal in number to the carpels, as when the dehiscence is through the ventral sutures only (Lychnis} ; sometimes double the number of the carpels, when the splitting takes place through both sutures (Diantlius) (fig. 273). Porous Dehiscence arises from the formation of orifices in the walls of a dry capsule, allowing the seeds to escape. In the Poppy (Pa/paver) a circle of pores is formed round the upper edge of the fruit, just beneath the stigma ; in Antirrhinum and Linaria there are two or three orifices near the summit of the capsule ; in some Campanulas a pore is formed at the base of each cell. In all these cases the orifices are formed from thin spots in the walls, which tear open, their edges curling back in more or less regular teeth : the dehiscence of Antirrhinum is connected by that of Scrophularia, Diqi- talis, &c. with the dehiscence into a crown of teeth as in Primula a'nd Caryophyllaceae. Transverse or Circumscissile Dehiscence, observed in the mem- branous capsules of Hyoscyamus (fig. 294), Anagallis (fig. 274), Plantago, &c., and in the woody fruits of Leeythis, arises from a transverse fissure running round the wall and splitting off the upper part of the fruit like a lid. A dehiscence analogous to this occurs in the lomenta of various LeguininosaB, which break across in several places between the seeds. In these cases a kind of articulation is produced, by the tissue of the pericarp remaining more delicate in the fine of dehiscence, so that it becomes torn by the hygrometric contraction or expansion of the firmer parts above and below, after the fruit has become mature. Period of Dehiscence. Dehiscence does not usually take place until the seeds are ripe ; but in Mignonette (Reseda} the ovary opens before ; in Leontice thalictroides the ovary bursts very early, and tlie seed ripens in a naked condition. In Impatiens and some other plants dehiscence takes place suddenly with considerable force, the valves separating and rapidly curling up. In Elaterium the peduncle separates in a similar sudden way from the ripe fruit, and the seeds are forcibly ejected. Fruit of Gymnosperms. In Gymnosperms there is of course no proper dehiscence ; but in most cases the carpellary scales of the female cones, which are separate to some extent during fertiliza- tion, frequently close up together so as to form an apparently solid body while the seeds are ripening, as in Pinus, Cupressus, Thuja, &c. (fig. 309). The scales open again when the seeds are ripe, CLASSIFICATION OF FRUITS. 145 but in some cases not for many years, and in other cases they separate from the axis. In Juniperus the scales become succulent. In Taxus the solitary ovule is naked ; but during the ripening of the seed a succulent cup-like envelope grows up round it. Forms of Fruit. The forms of perfect fruit are distinguished by technical names, and in denning them it is desirable to classify them in some way. The classification which conveys the greatest amount of information is that founded primarily on the con- struction of fruits. Fruits may be divided first into free or monothalamic fruits, formed from single flowers, and confluent fruits, formed of the blended flowers of an inflorescence. The term polythalamic has been conveniently applied to fruits of this latter kind. Free fruits may be divided into : 1. Apocarpous fruits, where the constituent carpels are solitary, or, if more than one, separate ; 2. Syncarpous fruits, formed of compound ovaries, and consisting of (a) superior fruits when the calyx is free, and (b) inferior fruits when the tube of the receptacle or of the calyx is adherent. Confluent fruits require no corresponding subdivision. The following are the terms most usually employed, and very many more might be enumerated ; but botanists now content themselves with a few well-defined types, and for the rest use such terms as capsular, baccate, &c., to indicate the general nature of the fruit, as more rigidly applied terms are not only cumbersome, but often fail in practice. Apocarpous Fruits. Achaenium. The Achcenium is a small, dry, indehiscent, one- seeded pericarp, tipped with the remains of the style, and with the seed free in the interior, except at the point of attachment. This fruit is rarely found solitary, as in Alchemilla ; it usually forms Fig. 280. Fig. 279. Fig. 281. Fig. 282. Fig. 279. Achaenium of Ranunculus cut vertically to show the seed. Fig. 280. Section of the fruit of the Date (Phoenix dactylifera) : c, the pericarp; x, the embryo imbedded in the horny albumen. Fig. 281. Circles of follicles of Semper vivum. Fig. 282. Persistent calyx of a Boraginaceous plant, opened to show the carcerulus formed of four indehiscent carpels, separating from each other. 146 MORPHOLOGY, OR COMPARATIVE ANATOMY. part of a multiple fruit, as in Ranunculus, Geum (fig. 289), c., where they occur on a dry receptacle or thalamus, or as in the Strawberry, where they occur imbedded in a succulent receptacle. Achaenia are popularly mistaken for seeds, from which they may be known by the stylar beak and by the seed lying loose inside. The term achaenium is often loosely applied to the halves of Umbel- liferous fruits (fig. 300), the cocci of Mallows, the nucules or nuts of Boraginacese, Labiatse, &c. (the carcerule of some authors) (fig. 282), and to the cypsela of Composite (figs. 283-285). Fig. 283. Fig. 285. Fig. 284. Fig. 283. Cypsela of Scorzonera. Fig, 284. Cypsela of Bidens. Fig. 285. Cypsela sliced vertically, to show the seed within. Drupe. The Drupe is a one-celled fleshy fruit, represented by stone-fruits formed from a single pistil, such as the Cherry or Plum, where the stone is formed by the inner part of the pericarp, and the pulp by the outer part. In common stone-fruits the drupe is solitary ; but minute drupes formed on the same plan are assembled together on the receptacle of the Easp- berry and Blackberry (fig. 290). The term drupe is often improperly applied to the compound stone-fruits, like the Cocoa-nut, &c., or to the Date, where the stone is formed by the seed alone, and the pulp by the pericarp (fig. 280). Fruits of this general kind are called drupaceous. Follicle. The Follicle is a simple pod, splitting down the ven- tral suture only, and bearing the numerous ovules on its margins. This rarely occurs solitary, but mostly combined with others in a circle, as in Aquilegia, Sempervwum (fig. 281), &c. j and they are then often coherent at the base. Legume. The Legume is a one- or many-seeded simple fruit, usually splitting down both sutures, with the placentas on the margins of the ventral suture. In most cases the legume is elongated and pod-like (fig. 286), as in the Pea, &c. ; but sometimes it is curved or even spirally coiled like a snail's shell, as in Medicago (fig. 287), or lobed and knotted, as in Acacia (fig. 288). In Astragalus a spurious sutural septum is formed by projection inward of one of the sutures (fig. 252). CLASSIFICATION OF FRUITS. 147 The Lomentum is a modification of the legume, either wholly inde- hiscent, or constricted into joints between the seeds and sometimes falling Fig. 286. Fig. 287. Fig. 288. Fig. 286. Legume of Pea, burst. Fig. 287. a, Curled legume of Medicago sativa; b, of Medicago orbicularis. Fig. 288. Legume of an Acacia. to pieces in these situations, as in Ornithopus, Desmodium, &c. In the lonientum of Cassia (e. g. Cassia Fistula) there are many false cross septa. Fig. 289. Fig. 290. Fig. 289. Multiple fruit of Geum, cut vertically (a) to show the attachment of the component achsenia (6) on a dry receptacle. Fig. 290. Multiple fruit of Blackberry (Eubus), cut vertically, showing the spongy receptacle covered with little drupes. Syncarpous Fruits Superior. Caryopsis. The Caryopsis is the one-seeded fruit of the Grasses, composed of two or, rarely, three carpels, which form a dry pericarp inseparable from the seed. In practice it is hardly recognizable from the achene, except in the last-mentioned charac- teristic. L2 148 MOEPHOLOGY, OE COMPAEATIYE ANATOMY. Samara. The Samara is a two- or more-celled, few-seeded, dry, indehiscent fruit, which has a membranous wing or wings Fig. 292. Fig. 291. /^^\ F & m Fig. 291. Double samara of the Maple (Acer). Fig. 292. Samara of the Elm (Ulmus campestris). Fig. 293. Samaroid fruit of the Birch (Eetula alba). developed from the pericarp as in Acer (fig. 291), Ulmus (fig. 292), and the little fruits of the catkin of the Birch (fig. 293). Practi- cally this may be regarded as one or more achenes with winged pericarps. Pyxis. The Pyxis is a one- or more-celled, many-seeded fruit, the upper part of which falls off like a lid by circumscissile dehiscence, as in Anagallis (fig. 274), Hyoscyamus (fig. 294), Lecy- this, &c. It differs from the capsule merely in its transverse de- hiscence. Siliq.ua. This is a two-valved linear pod, the valves of which separate septifragally from a kind of frame, with a more or less perfect false septum (rcplwn) stretched across it, the parietal placentas being attached to the frame, as in Sinapis (fig. 295), Cheiranthus, &c. It is the characteristic fruit of Crucifers. The Silicula (diminutive of the last) is merely a short and broad giliqua, often most exparided in the direction at ri^ht angles to the replum, the valves sometimes winged Thlaspi (fig. 296), Capsella, &c. When the replum is imperfect, it is said to ~be fmestrate ; or it may be destroyed altogether. Some siliquas and siliculas do not burst by valves Orambe, Raphanus, Isatis (fig. 297), &c. Capsule. The Capsule includes all the remaining kinds of dry fruits, membranous or woody, formed of one-celled or many- celled compound ovaries, which dehisce more or less completely by regular valves, equal in number to or double that of the carpels (Iris, Colchicum, Caryophyllacese, Digitalis, Primula, &c.), or by pores (Antirrhinum, Palaver). Its mode of dehiscence may be septicidal, CLASSIFICATION OF FEUITS. 149 loculicidal, or septifragal. Fruits of this general character are called capsular. Fig. 294. Fig. 296. Fig. 295. Fig. 297. Fig. 294. Pyxig of Jlyoscyamus, enclosed in the dry calyx. Fig. 295. Burst siliqua of Sinapis, the valves separating from the sutures supporting the replum. Fig. 296. Burst silicic of Thlaspi. Fig. 297. Indehiscent fruit of Isatis : a, entire; 6, a cross section. Syncarpous Fruits Inferior. Grlans. The Glans is a hard, dry, indehiscent fruit, spuri- ously one-celled from suppression, usually one-seeded, seated in a persistent involucre forming a cupule. In the Acorn and Hazel- nut there is a single gland in each cupule or cup, while in the Beech and Chestnut there are several. The ovary of the Oak is 3-ceTled, with two ovules in each cell ; but two cells with their ovules, together with one ovule of the fertile cell, are suppressed, and the wall of the ovary (fig. 271) is converted into a bony shell, completely filled by the remaining seed. The ovary of the Birch is also 3-celled, that of the Hazel 2-celled, that of the Chestnut 3-8-celled ; and similar suppression takes place. The inferior character of the fruit is marked, especially in the Chestnut, by the remains of the teeth of the calyx on the summit (fig. 216, p. 117). In the Acorn the gland is naked above, seated in a cup ; in the Hazel the leafy cupule envelopes it ; and in the Chestnut and Beech the spiny cupule encloses several fruits. Cremocarp. The Gremocarp is a schizocarpous or splitting fruit, consisting of two inferior achenes formed from a two- or 150 MOEPHOLOGY, OK COMPARATIVE ANATOMY. several-celled compound inferior ovary, the cells of which separate when ripe as indehiscent cocci. The separate halves of the two- celled fruit of Umbelliferae are frequently called mericarps (figs. 298-300) (Galium and many other Rubiacese, &c.). Fig. 298. Fig. 300. Fig. 299. Fig. 298. Frnit of GEftontttf, the halres not separated. Fig. 299. Cross section of the fruit of the Carrot. Fig. 300. Fruit of Umbelliferae, the mericarps separated and hanging from the carpophore. Bacca, or Berry. The Bacca, or true berry, is an inferior succulent fruit, crowned by the withered teeth of the calyx ; it is uniformly pulpy, with a thin skin, the numerous seeds being im- bedded in the pulp Gooseberry, Currant, Cornel (fig. 302), &c. The term " baccate " is now generally applied to all succulent fruits, whether superior or inferior, which have not a distinct stone like a drupe, as fig. 301. Fig. 303. Fig. 304. Fig. 301 . Nuculanium, uva, or superior berry of Solanum, cut across. Fig. 302. Berry of Cornel (Cornus mas). Fig. 303. Vertical section of the pome of Mespilus (Medlar). Fig. 304. Cross section of the pepo of Cucumber. CLASSIFICATION OF FKUITS. 151 Pome. The Pomum (fig. 305) is a compound, many-celled sue- Fig. 305. culent fruit, in which the epicarp is fleshy, while the endocarp forms either cartilaginous linings and partitions to the cells (a "core"), or bony shells around the more or less separated cells Apple, Quince, Medlar (fig. 303), Haw- thorn, &c. The fleshy portion of the pome consists of a dilata- tion of the upper end of the flower-stalk, in which the true Pome of Apple, carpels are imbedded. Pepo. The G-ourd is a succulent inferior one-celled fruit, with the seeds on three parietal placentas, imbedded in pulp, which often fills up the cavity; the epicarp is more or less leathery (Cucumber, fig. 304), or thickened and indurated (Gourd). Infrutescences or Confluent Fruits. Syconus. The Syconus is a succulent fruit, formed of an en- larged fleshy excavated or concave flowering axis, in which are im- bedded numerous separate fruits with dry pericarps. In the Fig the seed-like pericarps are seated on the walls of the internal cavity (fig. 306) ; in Dorstenia they are imbedded in the concave- topped common receptacle. Fig. 308. Fig. 306. i. 307. Fig. 306. Vertical section of the Fig (Fieus Carica). Fig. 307. Fruit of Mulberry (Morus nigra). Fig. 308. Fruit of Pine-apple (Ananasta sativa). 152 MOEPHOLOGY, OE COMPAEATIYE ANATOMY. Fig. 309. Sorosis. The Sorosis differs from the foregoing by the substance of the constituent pericarps, formed of the ovaries and floral envelopes of the flowers, becoming pulpy and confluent with each other (Morus, fig. 307), and sometimes with the succulent axis of the inflorescence (Pine-apple, fig. 308, Bread-fruit). Strobilus. The Strobilus, or Cone, is the cha- racteristic fruit of the Gymnosperms, consisting mostly of a conical or ovate mass of imbricated scales, with seeds in their axils (or on their bor- ders, Cycas), each scale being the development of a single carpel, representing a female flower (Finns, fig. 309). The Galbulus is a kind of cone with few scales, which have their heads thickened and forming the periphery of a somewhat globular mass, dry (Cupressus), or some- times succulent (Juniperus, fig. 267). The Seed. Formation of the Seed. The consequence of the fecunda- tion of the ovule is the development of an embryo in the embryo- sac (p. 139) ; and during the maturation of the fruit the ovules are perfected into seeds, the essential character of which is, that they are independent reproductive bodies, containing an embryo or rudi- mentary plant at the time when they are cast off by the parent (fig. 311 B, e). Fig. 310. a - Fig. 310. Section of an Umbelliferous flower, showing the two seeds in situ, each containing an embryo at the upper end, imbedded in albumen. Fig 311. Seed of Castor-oil plant (Ricinus) : A, external view : S, vertical section: a, hilum ; b, micropyte, with an arillode around it ; c, raphe, leading to (d) the chalaza ; e, embryo, with foliaceous cotyledons, and radicle pointing to the micropyle; f, peri- sperm or albumen. THE SEED. 153 The seed remains attached to the placenta of the fruit, until mature, by the funiculus, from which it ultimately separates by an articulation, so that a scar is left, called the hilum. The direction and position of the seeds in the cells of the fruit, as well as the modes of curvature, indicated externally by the relative posi- tions of the hilum (fig. 811, a), micropyle (b), chalaza (d), and raphe (c), are the same as in the case of the ovule ; and the same terms are made use of in describing their peculiarities. The face of a seed is the side or edge turned towards the placenta from which it arises. The direction of seeds may differ from that of the ovules, by alteration in the shape of the ovary, abortion of ovules, &c. It may be noted that anatropous ovules normally have the raphe next the placenta if ascending or suspended, so that the raphe indicates the face. Parts of the Seed. The seed consists of the proper body of the seed and its integuments, to which in some cases are added appen- dages of various kinds. The outer coat of the seed, called the testa, completely encloses it, marked, however, by the microscopic orifice of the micropyle, and by the hilum, or scar of the funiculus. The testa presents the greatest possible variety of conditions of texture, from membra- nous, horny, woody, or bony hardness, on the one hand, to a leathery or soft, pulpy condition on the other. The dry forms frequently exhibit beautifully regular markings, such as minute ridges, reticulations (Poppy, Silene, &c.), spines (Stel- laria, &c.) ; or the margins are produced into sharp edges or broad wings (Bignonia, Finns, fig. 312) ; or it bears a crown of hairs, or coma, at one end, as in Epi- lobium, Asclepias, &c. ; or it is completely covered with long hairs, as in the Cotton plant : while in various Polemoniacea?, Labiatae, &c.(Collomia &c.) it is clothed with microscopic hairs, which expand elastically and dissolve into a kind of mucilage when wetted. Some- times the testa is loose, and forms a kind of sac around winged seed the body of the seed, as in Orchidacese, Pyrola, &c. Pme * The inner integument, the tegmen or endopleura, is not generally distinguishable ; when it is, it is usually whitish and delicate. The reference of the integuments of the seed to their elements in the ovule is a subject of great complexity, since there appear to be no rules as to what regions of the ovule, from the nucleus outward, shall remain distinguishable or enter into the composition of the coats. The testa is commonly formed of the primine and secundine (p. 137) of the ovule con- joined. The tegmen seems to originate sometimes from the secundine, sometimes from the substance of the nucleus, &c. Small indehiscent fruits, such as the achaenia of Ranunculus (h'g. 313) or of Borages (tig. 282, p. 145), 154 MOEPHOLOGY, OE COMPAEATIYE ANATOMY. are liable to be mistaken for seeds when detached ; they are known by the remains of the style, and by the complete seed with" its proper coat being distinguishable on opening the pericarp (tig. 313). Fig. 313. Fig. 314. Fig. 315. Fig. 316. "Pig. 313. Vertical section of an achaenium of Ranunculus, showing the seed within the peri- carp and with a minute embryo in the albumen. Fig. 314. Section of the seed of Typha, showing the straight embryo in the axis of the peri- sperm or albumen. Fig. 315. Section of the caryopsis of Wheat, showing the abundant perisperm, a, with the embryo, b, at the base, outside. Fig. 316. Section of the seed of Iris, with the embryo enclosed in the perisperm. Enations from the Seed. A. considerable number of seeds possess a coat or appendage distinct from the proper integument, and produced entirely during the development of the seed from the ovule that is to say, after the fertilization of the latter. These additional structures are frequently fleshy when mature, as in the Spindle-tree, Euonymus, Podophyllum, &c. The older authors called all the forms by the same term, arillus ; recent authors distinguish the true arillus, which grows up over the seed from the funiculus, like the primine and secundine, as in Nymplicea, Passion-flowers, &c., from the arillode, which originates at or near the micropyle, and grows down more or less over the testa, as in Euonymus (where it forms a pulpy coat), in Euphorbia, Ricinus (fig. 311), Polygala, Ac. The mace of the nutmeg is an arillus, adhering both to the hilum and micropyle. The appendages which grow from the raphe, in Chelidonium, Asanim, Viola, &c v are sometimes called strophioles. The body of the seed is composed either of the embryo alone, or of the embryo imbedded in a mass of tissue, called the perisperm, or albumen (figs. 313-320). Seeds wherein the embryo is immedi- ately invested by the integuments are commonly called eocalbu- minous or aperispermic (figs. 321 & 323). Where perisperm exists, they are called albuminous (figs. 313 &c.). The term albumen, founded upon the functional analogy with the albu- men or white of an egg, is very inconvenient, as it has a distinct chemical sense, in which it is frequently used in the chemical questions of vegetable THE SEED. 155 physiology ; and therefore the word perisperm is preferable. All seeds in their rudimentary condition contain perisperm j but as the embryo grows it is often absorbed, so that in the ripe seed it is no longer perceptible. It is considered to be analogous with the prothallus of the higher Crypto- gams. The Perisperm varies very much in both quantity and in texture in proportion to the relative magnitude attained by the embryo (figs. 313 & 320), and in consequence of the different mode of Fig. 319. Fig. 317. Fig. 318. Fig. 317. Section of the seed of Lychnis, with a peripherically curved embryo, 6, surrounding the perisperm, a. Fig. 318. Section of the seed of Piper, showing the embryo in a separate sac at the apex of the perisperm, which latter is hollow in the middle. Fig. 319. Section of the fruit of the Cocoa-nut Palm, showing the fibrous epicarp, the woody endocarp (ar) enclosing the hollow perisperm, in which lies the minute embryo. development of the cellular tissue and its contents in different cases. The texture or consistence of the perisperm is termed mealy or farinaceous when it may be readily broken down into a starchy Fig. 322. Fig. 321. A -e Fig. 320. Vertical section of the seed of JRicinus : a, hilum ; 6, micropyle ; c, raphe ; d, chalaza e, embryo ; f, perisperm. Fig. 321. Aperispennie dicotyledonous seed of a Bean, with the coats removed: a, radicle; b', b", cotyledons (separated to show the plumule, c). Fig. 322. Monocotyledonous embryos removed from the perisperm, vertically sliced: A, of Calla palustris ; B,Avena(O&t): a, radicle; b, cotyledon; c, plumule. powder (as in Corn-grains &c.); oily when it is composed of soft 156 MORPHOLOGY, OB COMPARATIVE ANATOMY. tissue loaded with fixed oil (as in the Poppy and Cocoa-nut); muci- laginous or fleshy when it is tougher and swells up readily when wetted (as in the Mallow) ; horny when hard and more or less elastic (as in Coffee, Galium, Iris, &c.). The perisperm is usually a uniform mass ; but in Nympheea, Piperacese (fig. 318), Canna, and some other plants the embryo is contained in an inner central compartment or sac (sometimes called the amniotic sac) so that the perisperm is here double. The enclosed portion is some- times called the endosperm ; the development of this will be describee in the Physiological part of this work. The uniformity of the perisperm is also destroyed in some seeds by a peculiar tabulated condition of the outer portion, the sinuosities being rilled up and enclosed in an inseparable layer of different-coloured tissue giving a marbled appearance ; this, which 'is seen in the Nutmeg, is calle( a ruminated perisperm or albumen. In the Cocoa-nut the perisperm hollow when mature, containing the so-called milk (fig. 319). The Embryo. The embryo, or rudimentary plant contained in the seed, ordinarily possesses, when the seed is mature, all tht essential organs of vegetation, namely root, stem, and leaves, al- though in a few cases the leaves are undistinguishable ; while in others the embryo is a mere cellular nodule in the ripe seed, as in Orchidacego and Orobanchaceae. The embryo is the result of the fertilization of the germinal vesicle or oospJiere contained in the embryo-sac (p. 139). Parts of the Embryo. The end of the embryo usually pointing to the micropyle is the radicle (figs. 320-323, a) or rudimentary root, continuous with the lower end of the axis which termiuates at the other end in the plumule (figs. 321-323, c) or rudimentary terminal bud. The axis itself is sometimes very short, being a mere " collar" between the base of the seed-leaves and the radicle ; but, in some cases, it is developed into a well-marked hypocotyledonary axis or tigellum, distinguishable from the radicle by its cylindrical form (or, if conical, the point of the cone is upwards). The rudimentary leaves, called cotyledons (figs. 321-323, 6", &', //), differ in number in the two great classes of ADgiospermous Flowering plants, since in the Dicotyledons there are two placed face to face at the upper end of the axis, with the plumule between them (fig. 321); and in Monocotyledons only one exists (or the rudiment of another on a different level), and this is more or less completely rolled round the plumule, like the sheath of the leaf in Grasses (fig. 323). The embryos of the Gymnosperms are either dicotyledonous, as in Cycas, Taxus, Juniperus, &c., or really or apparently polycotyledonous, as in Pinus (fig. 324), where it is said that the seeming whorl is formed of two deeply divided cotyledons. Direction of the Embryo. The embryo, whether covered only by THE SEED. 157 the coats or imbedded in perisperm, exhibits many varieties in the relative position of its parts : thus it may be straight (fig. 314), curved, arcuate, or hooked (fig. 325), spirally coiled (fig. 326), or folded; in Fig. 323. Fig. 324. Fig. 325. Fig. 326. Fie. 323. Aperispermic Monocotyledonous seed of Potamoyeton, with the coat removed: a, radicle ; 6, cotyledon; c, plumu 1 *?. Pig. 324. Embryo of Pinus, extracted from the perisperm, and the cotyledonary lobes separated . Fie 325. Vertical section of the seed of Atropa Belladonna. Fig 326.' Vertical section of the seed of the Hop (Humulus). the last case the radicle may be folded against the back of one of the cotyledons (incumbent, fig. 327) or against their edges (accumbenf). The cotyledons, which are usually of fleshy texture, and vary much in form, degree of expansion, and solidity in different cases, are occasionally rolled or folded up like leaves in leaf -buds (figs. 328 & 329) ; and these are described by the terms defined above under the vernation of leaves (p. 73). They are sometimes folia- ceous, as in Convolvulus or Ricinus (fig. 320), &c. The fleshy kinds occasionally cohere very firmly in Dicotyledons in the mature state ; and they are sometimes of unequal size, as in Trapa natans. Fig. 328. Fig. 329. Fig. 327. Vertical section of the seed of Eryximum: a.funiculus. Fig. 328! Dicotyledonous embryo extracted from a Turnip-seed. Fig. 329. Dicotyledonous embryo extracted from the seed of the Maple (Acer). Generally the cotyledons form the greater part of the embryo, as in the Bean (tig. 321) ; but sometimes they are very small or undistinguishable. They usually die away, but in Welwitschia they remain to form the only leaves the plant has. Eelative Position of the Embryo. The embryo may be in the very centre of the perisperm (Polyyomim), excentric ; completely external (Grasses, fig. 315) ; curved round the outside .peripherical (Lychnis, fig. 317). The radicle generally points to the hilum (homoblastic), rarely away from it (enantioblastic). 158 SYSTEMATIC BOTANY. PART II, SYSTEMATIC BOTANY, CHAPTER I. PRINCIPLES OF CLASSIFICATION. Sect. 1. SPECIES AND GTENEKA. Systems of Classification. In throwing plants together into groups, two methods may be adopted, constituting respectively an artificial or a natural system of classification. In the former, the only object is to arrange or place objects in such order that we may find them readily by some prominent mark, in the same manner as words are arranged alphabetically in a dictionary. In a Natural Classification, the object is so to combine our materials that the things brought closest together shall have the greatest possible agreement; from which it results that a knowledge of ail the peculiarities of one carries with it the knowledge of most of those of its neighbours, and enables us, from the observation of a portion of the characters of a given kind, to foresee the rest. According to the derivative theory a group is natural in proportion to the accuracy with which it expresses the degree of relationship of the members of the group to each other, and of one group to its fel- lows. If there is no real kinship the resemblance is only super- ficial, and the classification therefore artificial. Species. Systematic Botany is founded upon the real or assumed existence of distinct kinds or species of plants a notion which of course belongs not to science exclusively, but is a part of the common experience of the world. But there is a great difference, practically, between the kinds of things accepted in the ordinary affairs of life and the kinds admitted in science, more especially in the Biological sciences. PEINCIPLES OE CLASSIFICATION. 159 There is another fact of daily experience which is of primary im- portance in reference to this point ; that is, the circumstance that plants produced from seeds most commonly resemble in all impor- tant respects the parent plant from which the seeds were derived, and this through an indefinite number of generations ; from which it follows that kinds or species of plants are regularly reproduced by their seeds. The definition of a species can only be considered as arbitrary ; but for practical purposes it may be said that a species consists of those individual plants which agree in all their important and con- stant characters, in the same way as do individuals of analogous structure, which we know to have descended through a number of generations from a common stock, and which therefore may be assumed to have been produced through seed from an original individual, or pair of individuals, of a distinct kind. To these may be added the assertions that individuals of the same species may be cross-fertilized, to the improvement rather than the detri- ment of the fertility of their seeds, and that they are affected in a generally similar manner by external agencies. Diversity of opinion still exists amongst naturalists as to the origin and fixity of species. On the one hand it is assumed that every distinct species originated in a distinct creation of that form, which has been perpetuated, with its essential characters unchanged, through succeeding generations. It is usually added by the same school that, as regards plants, every species originated from a single prototype, or a pair of parents where the plant is dioecious. On the other hand, it is contended by most modern naturalists that species were not necessarily created as we now see them, but that existing species are the lineal descendants of those that have gone before, and more or less modified in course of time by varying circumstances, such as inherent tendency to vary, the effect of external agencies, and the com- petition of other forms. This notion involves the conclusion that species are not absolutely invariable. Varieties. Species are distinguished by those characters which under present circumstances are constant so long as the conditions under which they exist remain unchanged ; but individuals may possess other additional characters of less importance, which are inconstant. Even as in the human species we find every individual possessing cer- tain peculiarities, so even in almost to the lowest of created beings do we find what is called an idiosyncrasy, and individual character, chiefly depending, in the vegetable kingdom, upon the conditions under which they have grown up. We often find seeds from the same parent producing individual plants differing in the colour, size, and number of their flowers and of their vegetative organs, according to the conditions of climate and soil to which we submit them. Very often, moreover, we find these differences displaying themselves under what appear to us identical conditions, as is particularly the case with many of the favourite " florist's flowers " such as the Pelargonium, Fuchsia, Pinks, Asters, &c., 160 SYSTEMATIC BOTANY. which " sport " out into numberless varieties when raised from seed under highly artificial conditions. The occurrence of such variations is less common and, when it occurs, generally less marked in wild plants, as might naturally be expected, from the likelihood of wild plants maintaining their footing best in a position where the conditions are most natural to them ; but we do find remarkable cases of variation in many wild species, as of colour in the common Milkwort and the Columbine (Aquileijia) ; but most of those kinds which exhibit the tendency now and then in a wild state, become extremely variable under culture. Some of the variations are dependent simply upon modifications of the cell- contents of certain tissues, as in the commonest of all variations, those of colour, and in the not uncommon appearance of white patches and streaks (" variegation ") on the leaves. Other variations are teratological, and result from the over-stimulation of the vegetative system, causing the reproductive organs to degenerate (of which the ordinary " doubling " of flowers by the degradation of their stamens into petals is an example) or, vice versa, the application of stimuli at particular epochs, producing remarkable development of flower or fruit. All these A r ariations, more especially those involving serious teratological changes, tend to disappear. Common variations, of slight importance, mostly die out at once in the descendants through seed, especially if the conditions are varied ; serious departures from the typical structure (teratological variations) lead to barrenness and incapability of continuing either the variety or the species by seed. It is important to note here a fact which will be more minutely examined in another place, namely, that although the peculiar characters of varieties are commonly lost in seeds, the peculiar form is capable of indefinite propagation by vegetative multiplication through cuttings &c., the special idiosyncracy being possessed in common throughout all the leaf -buds, both while forming part of the parent and after they have been detached from it to form new plants, grafts, &c. A certain number of species which vary more or less in a wild state exhibit a remarkable peculiarity under systematic cultivation. By strictly maintaining a certain set of conditions, varieties originating accidentally or through^intentional treatment are made to manifest their additional peculiarities so strongly, that they transmit the tendency to present similar peculiarities to their seeds ; and such transmission goes on for an indefinite number of generations, provided the requisite external conditions are kept up. In this way arise what are called Races, series of individuals connected by common characters and by inheritance, like species ; but, unlike them, liable to lose, in one or a few generations, under change of conditions, part or all of the essential characters by which they are distin- guished. We have examples of such races in most of our esculent vege- tables, especially in the many varieties of form, more or less permanent, derived from the wild Cabbage (Brassica okracea}. These, together with Hybrids, or the produce of cross-fertilization between individuals of distinct species, will be referred to again among the phenomena of the Physiology of Reproduction. The determination of the limits of species is greatly obstructed in many cases by the frequent occurrence of varieties, and more particularly of races to which hybrids add another complication, probably of less importance than many modern authors suppose. It appears probable that the number of real species is SPECIES AND GENEKA. 161 far smaller than is usually supposed, and that many races, and a large number of frequently recurring varieties, hold a place in our existing lists of species. The varieties and races above mentioned are considered under the development hypothesis as the initial stages in the formation of new species. If these variations are of such a nature as to enable the plant ta adapt itself better to the conditions under which it lives, or to sustain itself in the battle of life with other organisms, then they will be perpetuated become more constant, and ultimately attain such a degree of relative constancy or invariability as to be classed as species. Genera. Whenever we examine a large assemblage of distinct species, we shall find that certain of these agree with certain others more closely than with the rest ; so that we may parcel them out into groups, in each of which we shall find an agreement in a number of common characters, by which it is also distinguishable from the other groups. Generally speaking, we shall find that we can place together a number of species agreeing closely in the essential plan of construction of their floral organs, while they differ in the forms and duration of their vegetative organs, &c. Groups of this kind are called genera ; and the notion of a genus, like that of a species, is not only common to all departments of human knowledge, but is also existent in the language of common life in its special natural-history sense, only requiring for scientific purposes to be more strictly defined. In every language we find generic names applied to plants, such as Willow, Rose, Violet, and a hundred others, each of which terms is indicative of a group of kinds or species, more or less extensive in different cases, corre- sponding exactly in its logical value to the genus of the botanist. Some of these groups are characterized by very striking peculiarities, so that even the genera of vulgar language correspond very nearly with those of the botanist j but in the generality of cases the popular collective names are applied on superficial grounds of resemblance, and include widely diverse species. For example, the term Violet is made to bind together not merely the common scented and other true Violets, but the Dame's Violet (Hesperis\ a plant of the Cabbage family, the Calathian Violet (Gentiana Pneumonanthe), a true and characteristic Gentian, the Dog's-tooth Violet (Erythronium Dens-Cams), a plant of the Lily family, &c. ; while the term Rose is extended from true Koses to Cisti, or Rock- roses, Rhododendrons, Alpine Roses, &c. It is obvious here that there can be no near " blood relationship," if we may so term it, between these so-called Roses, &c. The classification of all these forms having only superficial resemblance to each other is a purely artificial classification. Still some genera are characterized in a sufficiently marked way for most of their constituent species to be recognized as such pretty readily, after a very small amount of attentive examination, as, for example, true Roses, Willows, Lilies, &c. ; and we call such genera, including species of a very marked similarity, " natural genera," thus indicating the closeness of the band that ties them together. On the other hand, the principle of combination which accords with the intuitive classification in those M 162 SYSTEMATIC BOTANY. natural genera leads to the establishment of other genera wherein the species seem at first sight to differ widely, of which we could not have a better example than in the genus Euphorbia, where our native species are inconspicuous herbs, while the tropics afford species with large spiny Cactus-like trunks, &c. Moreover the carrying out of the same principle leads in certain cases to the generic separation of species which present close agreement in their general characters, but are distributable into a number of groups characterized by very decided morphological diversities in important parts of their floral organs. Thus, in the Umbelliferse, the Compositse, the Grasses, and some other families, we separate generically species which have a great resemblance in the maj ority of their characters. This happens especially in what are called very natural families of plants, large assem- blages of genera so evidently connected with each other by the presence of some very marked peculiarity, such as the Umbelliferous inflorescence, the Papilionaceous corolla of the Leguminosas, the Capitulous inflores- cence of the Composite, the peculiar spikelets in the Grasses, &c., that no doubt can be entertained as to their lineage. On the other hand, the " natural genera " occur mostly where the character of the natural family is more lax and flexible, as in the Ranunculaceae, Rosaceae, &c. In the present state of knowledge it must be admitted that a very large portion of our generic distinctions are arbitrary, and that the species included in some genera agree together much more closely than those combined under other generic heads. At the same time it cannot be doubted that some genera are really far more extensively represented by species than others ; so that the mere number of kinds included in a genus is to be totally neglected in a natural classification ; and many recent authors have done disservice to science in general by splitting up large natural genera on slight characters for the convenience of systematists. It is far more instructive to keep together the members of large natural genera, like Ficus, Erica, Begonia, &c., than to subdivide them under names which disguise their relations ; and the convenience of systematists may always be sufficiently regarded by the establishment of sections in extensive descriptive works. Genera are groups of species associated on account of agreement in the essential characters of their floral organs ; but here, as else- where in nature, variations from our abstract types must be ad- mitted. Some undoubtedly natural genera include species with their floral organs varying in certain particulars more than is usual in groups associated under a common type, somewhat as certain species admit of a wider range of variation than others. Here, again, physiological characters become of value ; and as in species we regard the fertility of the seeds produced by unlimited cross- breeding between the varieties as a proof of these being individuals of the same species, so with regard to genera it is commonly held that a generic connexion between diverse species is indicated by the capability of producing hybrids by cross-breeding. These true hybrids produced between distinct species of the same genus are often barren, or only breed with individuals of one of the parent SPECIES AND GENEEA. 163 species, which soon eliminates the cross, and leads to a complete reversion to that species. The physiological test is consonant with morphological evidence. In- dividuals of the same species are capable of indiscriminate fertilization because they are exactly alike in all essentials of structure. In hybrids produced between two species of a genus, the parents agree sufficiently in structure to allow of their producing a few fertile seeds ; but the plants raised from these seeds contain two contradictory impulses, which so far prevent the perfection of their organization that they either remain barren or a dissociation of the mixed characteristics occurs with, it may be, their ultimate entire extinction. Origin of Species Selection. Supposing species to have originated from a few primordial forms, from which all existing species have been derived, just as individuals may be traced back to a common parent stock, the question then arises as to what causes have produced the modifica- tions. Where, on this hypothesis, there were originally a few, or perhaps a single primordial form, to which all then existing individuals might have been referred, there is now an infinite number of forms both in the animal and vegetable kingdoms. How have these arisen ? To this question the answer given by various naturalists has been different. By some the variations have been attributed to the influence of external conditions; by Darwin to an innate tendency, producing variations of structure, some of which, under given circumstances, would be favour- able to the progress and development of the individual, and others not so. In the battle of life, the struggle constantly going on in animated nature, those variations most advantageous to the organism in its compe- tition with others would be preserved by " natural selection," while other variations of less advantageous character would be obliterated or not perpetuated. Hence the victory would be to the strongest ; the weakest would go to the wall, and the result would be, in Mr. Spencer's language, " the survival of the fittest." It will thus be seen that on this hypothesis species are not considered immutable, and variations, especially such as are advantageous to the organisms, are regarded as the starting- points of new species. With reference to these points the student will do well to bear in mind that these and kindred speculations are not to be treated as dogmas or creeds, but as means to an end, and that end the more perfect knowledge of the origin and relation of existing forms. Any hypothesis or theory which will serve to correlate and bind together a number of otherwise isolated facts and explain their interdependence, is valuable not only for what it effects at the time, but as a focus around which other facts may in future be gathered. That hypothesis is best which serves to give a rational explanation of the largest number of ob- served phenomena of the greatest importance. Tried by this test, the Darwinian hypothesis, or, rather, the theory of evolution, has great ad- vantages, and presents on the whole fewer difficulties and less inconsis- tencies than the older hypothesis of separate creation of each species. Particularly does this seem true in the case of the subject now before us the classification of plants. The admission of the principle of filiation and genealogical descent gives the natural system of classification a clearer claim to its title of " natural " than it had before, supplies the explanation M2 164 SYSTEMATIC BOTAXY. of a vast number of phenomena otherwise inexplicable, and offers plau- sible and valid reasons for the existence of facts and processes that were previously considered either unintelligible or purposeless modifications of an assumed structural type. The portion of Mr. Darwin's hypothesis which has perhaps received the least amount of assent has been that relating to natural selection. The idea was based on that artificial pro- cess of selection by means of which man has been enabled progressively to improve and perpetuate the different forms of domestic animals and cultivated plants. In the latter case the horticulturist is ever on the look-out for variations. If he sees one that suits his purpose, such, for instance, as a plant producing larger flowers than ordinary, he does all that he can to perpetuate that variety by carefully selecting seed from it, at the same time that he destroys or neglects other less desirable varia- tions. In this manner, after a time, the selected variety becomes " fixed," and a " race " is formed. On the Darwinian hypothesis a selective process is supposed to occur naturally, similar to that employed by the gardener or agriculturist as just explained, such selection or elimination resulting, as before said, in the survival of the fittest. Sect. 2. NOMENCLATURE. Names of Plants. The Terminology of Botany establishes rules for naming the parts or organs of plants, and the different charac- teristics which those organs present. Nomenclature deals with the naming of plants themselves as members or parts of the Vegetable Kingdom ; and it furnishes the rules for naming the kinds of plants, and the various groups or assemblages in which they are associated in our systematic classifications of kinds. The primary rule in botanical (and zoological) nomenclature as laid down by Linnaeus is, that every species shall have a particular name, compounded of a substantive and an adjective (or substantive used adjectively), luhereof the former indicates the genus, and the latter the species. This rule of naming may be compared with the common usage of sur- names and Christian names the former indicating the family to which a man belongs, while the latter admits of his being spoken or written ^about without the necessity of adverting, except for special purposes, to his per- sonal peculiarities or his relationship to the other members of his family. These scientific names of plants were originally established in Latin, because Latin was the general language of science at the time they were introduced; and they will be retained with advantage so long as diversity of language exists, since they ensure to all plants and animals names which have universal acceptation, and which, like the Arabic numerals 1, 2, 3, &c., are equally comprehensible to the educated of all nations, and, moreover, they are more definite and precise in their signification than ordinary vernacular appel- lations. NOMENCLATURE. 165 Generic Names. The substantive names of genera have been and are still formed very arbitrarily, and without any generally recognized principle. All those which have been identified as known to the ancients are called by their classic names, such as Prunus, Myrtus, Quercus, Thymus, &c., the etymology of which is more or less obscure in various cases. A very large proportion of modern generic names are founded upon com- binations of Latin and, more particularly, Greek words indicating some obvious external peculiarity, or some property possessed, or supposed to be possessed, by the plants ; but the application of this principle has often been carried out without accurate knowledge and without happiness in selection, so that many such names are but little characteristic, and would often apply more correctly to other genera. Those, on the contrary, which are well chosen afford a certain assistance to the memory ; exam- ples of such names, founded on structure, occur in : Lithospermum, so called from its stony fruit (or supposed seed) ; Campanula, from its bell- shaped corolla ; Sayittaria, from its arrow-shaped leaves, &c. : on quali- ties, in Glycyrrhiza (Liquorice), from its sweet rhizome ; Rubia (Madder), from yielding a red dye; Lactuca (Lettuce), from its milky juice, &c. : or on accustomed station, as Arenaria, Eptdendrwn, &c. : others have derived their names from supposed medicinal powers, such as Pulmonaria, Scropkularia, &c. Another large class of generic names is founded on proper names either of mythological or real personages, more especially distinguished botanists, to whom the genera are dedicated. Linnreus drew largely upon classical mythology and legendary history as a ready source of diverse names for the many newly defined genera he had to deal with ; and the names Iris, Artemisia, Amaryllis, Narcissus, &c. stand out strongly in their euphony from most of those founded on modern names; such names, however, as Linncea, Lobelia, Dioscorea, Magnolia go far to rescue the principle of naming genera after botanists and their patrons from the opprobrium brought upon it by such as Schumacheria, Schweyckherta, Razoumowskia, Eschscholtzia, and the like, and will pro- bably be preferred by most persons even to such " characteristic " names as Pleuroschismatypm, Oxystvphyllum, Pachypterygium, Glischrocaryon, &c. In face of these last, the pseudo-Latin barbarisms Thea, Coffcea, Bam- busa, which preserve the original native names of plants, become no longer uncouth. Specific names are always either adjectives, or substantives used adjectively. When they are adjectives, they must of course be made to agree with the substantive; and it may be recalled to recollection that in Latin all names of trees are feminine, whatever may be the termination. In the majority of cases, the specific names are selected on similar grounds to the generic. Attempts are very commonly made to render the name characteristic, a proceeding which in many cases affords a certain advantage j but when, on the contrary, it is carried out in im- 166 SYSTEMATIC BOTANY. perfect acquaintance with the species of large genera, it leads to con- fusion. Sometimes these names indicate the character of the leaves, as in Tilia grandifolia and parvifolia, or the existence of a definite number, as in Platanthera bifolia, Paris quadrifolia, &c. ; or the character of the inflorescence, as Butomus umbellatus, Bromus racemosus, &c. Or the "habit "of a species is indicated by such adjectives as major, minor, scandens, &c. ; or its duration, as by annua, perennis, &c. ; and in some cases comparisons with other plants are marked, as in Ranunculus aconi- tifolius, Acer platanoides, &c. Generally speaking, the colour of flowers is too variable for specific distinctions ; but nevertheless many species are named from their usual or constant colour, as Gentiana lutea, Lamium album and purpureum, Digitalis purpurea, &c. Station, i. e. kind of soil or place inhabited by a plant, is another source of names, as arvensis (common on ploughed land), agrestis, hortensis (on cultivated ground generally), pratensis (in meadows), sylvestris or sylva- ticus (in woods), palustris (in swamps), aquaticus (in or about water), and satimiSj a term commonly applied to kinds regularly cultivated from seed. Most of these terms are applied vaguely, and a similar want of accuracy in the implied idea affects many of the names founded on the places where plants have been first observed, such as Silene gallica, Stachys t/er- manica, Genista anglica, &c., none of which are peculiar to the countries named, though they may, in the first instance, have been considered to be so. Such names as odorata, suaveolens, foetida, &c., expressing marked qualities, were formerly much used; and the adjective qfficinalis is found applied to a host of plants formerly valued by the herbalists for some supposed medicinal or economical property. Substantive names used adjectively are mostly names of abolished genera, retained in association with the new generic term, as Ranunculus Flammula, Pyrus Malus, Matricaria Chamotnilla, Primus Cerasus, &c., these old generic terms being in a few cases double, as Adiantum " Capillus- Veneris" Lychnis " Flos-cucidi" &c. Or substantive proper names are used in the genitive case, as Limnocharis Humboldtii, Viola NuttaUii, Galium Vaillantii. The dedication to distinguished persons may, however, be effected by adjectival terms, as Salix Doniana, &c., the use of the genitive noun being more strictly appropriate when it is the name of the discoverer or first describer of a species, the termination ana conveying a mere compliment and not necessarily implying that the person to whose name it is affixed had any thing to do with the particular plant in question. Authorities for Names, If the rules of scientific nomenclature were strictly enforced under the direction of a single authority, each plant would have but one name (composed of the generic and specific appella- tions), and this name would be indissolubly and unequivocally connected with the idea of the peculiar species. But it happens practically that such is not the fact, and this for reasons necessarily affecting various cases. Not unfrequently it happens that a plant possesses more than one specific name, which may arise from an author naming it a second time, through entire ignorance of its having been previously observed, or from his erroneously supposing a particular form to be distinct from the already known and named species. Almost as frequently in the present day do NOMENCLATURE. 167 we find a distinctly recognized species denominated by more than one generic name, while the specific appellation remains the same, this ambi- guity arising from difference of opinion as to the limits of genera, and con- sequently as to the group to which particular species are to be referred. To ensure accuracy, therefore, it becomes necessary, whenever the name of a plant is mentioned in a scientific work, that the authority for the name (that is, the author who originated it, or whose peculiar application of it we adopt) should be indicated. This is done by subjoining an ab- breviation of his name. Thus, Bellis perennis, Linn., or L. ; Inula Conyza, DC. ; Pulicaria vulgaris, Gaertn., signify that we mean the species which were defined under these names by Linnseus, De Candolle, and Gaertner, respectively. In like manner it is requisite, in the majority of cases, where the name of a genus is mentioned, to indicate the authority, since many of the older genera of Linnaeus and others have been broken up into a number of groups, and the original name restricted to one of these more limited assemblages. Synonyms. The superfluous or incorrect names which exist in many cases cannot be neglected where they have once acquired a certain currency, because a certain amount of existing knowledge is connected with these names in the works of the writers who have used them. Hence arises the necessity of enumerating the synonyms of plants. The citation of synonyms is of course un- necessary in general cases, where the names of plants are incident- ally mentioned, so long as the authority for the name is given ; but in Systematic works, such as descriptions of the plants of a country or province, or monographs upon particular groups of plants, it is part of an author's duty to ascertain and indicate .all the names which have been applied to the particular forms, and the exact senses in which different names have been employed. The synonyms subjoined to a specific name may indicate : 1, that the same species has received different names from different authors ; 2, that a selected specific name includes the several sup- posed or real species enumerated under it ; 3, that the species has been removed from a genus to which it was formerly referred ; 4, that a particular view is taken both of the generic and spe- cific value pf a plant concerning which opinions have varied in both particulars. The following examples may serve to illustrate this : 1. The name Galium verum, L., has simple priority and therefore pre- ference over G. luteum, Lamarck, indicating the same species, which was accidentally or erroneously named by the latter author after Linnaeus had given it an appellation. 2. Agrostis alba, L., includes A. compressa, Willd., A, gigantea, Koth, A. stolonifera, L. (in part), &c. ; these latter have been mistakenly sepa- rated from it, or subsequently named without knowledge of the identity. 3. Castanea vvlyaris, Lam., is now substituted for Fagus Castanea, L., as the genus Castanea is now regarded as distinct from Fagus. In many 168 SYSTEMATIC BOTANY. cases we find a distinct generic name given as a synonym where it is really more recent, but is rejected in favour of the older on the ground that the more recent generic separation is not approved of; for instance, Apargia autumnalis, Willd. (Oporinia autumnatis, Don). 4. Catabrosa aquatica, Beauv., is named in diverse works Aira aqua- tica, L., Molinia aquatica, Wibel., Poa airoides, Koel., Glyceria aquatica, Presl, &c. The multitudinous synonyms which fall under the last category are attributable to the excessive tendency of modern writers to multiply genera on slight grounds. Such minor subdivisions are far better restricted to extensive systematic works, on the plan adopted in De Can- dolle's f Prodomus,' providing them with sectional names for the exclu- sive use of systematists, and preserving the more general name for common purposes. Nomenclature of Varieties. The varieties of species are no- ticed in descriptive works when of frequent occurrence, and then are either simply indicated by the letters of the Greek alphabet, or have an additional adjective name like the species, which plan is especially followed in lists of garden varieties. In such cases either the ordinarily occurring form is taken as the type, and the series of occasional varieties is begun with /3, as Sambucus nigra, L. , var. (3. leaflets laciniated (Hooker & Arnott). or, Sambucus nigra, L. j3. virescens (fruit green). y. leucocarpa (fruit white). . lacmiata (leaflets laci- niated). e. variegata (leaves with white streaks), Koch. Or if the species is variable and no one form is considered typical, the series begins with a, thus : Fedia dentata (Hooker & Arnott). a (Valerianella Mon- sonii, DC.). /3 (Fedia mixta, Yahl). y (Fedia eriocarpa, Eo3m. & Sch.). The nomenclature of cultivated plants is fruitful in examples of named varieties in large numbers belonging to particular species, such as Clarkia pnlchella alba, C. pulchella rosea, &c. &c. ; but these names are often ap- plied without scientific exactitude. Hybrids are named according to certain rules when they occur frequently wild or, if obtained artificially, when they are propa- gated by cuttings, bulbs, &c. The names of the two parent species are combined, thus : Verbascum niyro-Lychnitis, a hybrid between V. nigrum and V. Lyclinitis. With regard to artificially produced hybrids, it is possible to indicate the parentage with more accu- racy, and the name of the seeding plant stands before that which yields the pollen, as Amaryllis vittato-regince, the form produced when the ovules of A. vittata are fertilized by the pollen of A. NOMENCLATURE. 169 regincv, and vice versa. Where a plant is known to be of hybrid origin, it is a good plan to indicate the fact by prefixing x to the name. The nomenclature of the groups above genera is of less import- ance than that of genera and species, and is dealt with more independently by individual writers. Artificial groups are gene- rally named from the character on which they are founded, as in the case of the Linnean classes and orders. The same is the case with the artificial divisions which are used in most Natural Ar- rangements for conveniently subdividing large assemblages of Families or Orders, such as Tkalamiflorce &c. of De Candolle, Poly- petalce &c. of Jussieu. But as the essence of the Natural Ar- rangement of plants lies in the combination of forms according to the majority and importance of points of likeness or general character, we are not necessarily restricted by any definite character in the selection of the name ; and in regard to the Natural Orders, great diversity of principle has prevailed in the application of the names, and even considerable latitude in the form given to them. There exists, however, one rule applied in all Latin naming of what are termed Natural Orders : the word plantce is understood, and an adjective name agreeing with this represents the group. In exist- ing systems we find these adjective names founded sometimes on a prevalent character in the family, as (plantse) Leguminosae, Coniferae, UinbelliferaB, &c. ; sometimes on the names of typical genera, as Eosaceaa, Solanaceaa, Convobulaceae ; sometimes on an existing general name derived from common language, as Granii- naceae and Palmaceae. A difference of termination exists even in regard to the same word in different authors : thus, one author writes Cistineae, another Cistacese, with the same meaning ; while others use the word Aroideae in preference to Araceae. or Palmae in preference to Palmaceae. Attempts have been made to reduce all these names to a system, and to preserve the same form of termination for groups of the same value. Thus it is proposed to make the names of all Orders end in aceee, like Ranunculaceae, Ericaceae, &c., the only objection to which is the necessity of discarding many familiar and well-established names, and replacing them by strange ones, as Apiaceae for Umhelliferae, Fabacese for Legumi- nosae, &c. " Classes " or fl Alliances " again are made alike by using the terminal form -ales : as Glumales, instead of Glumaceae or Glumiferse, for the group composed of the Orders with a glurnaceous perianth, &c. A fixed rule does exist among all modern writers in the denomi- nation of suborders or tribes into which Orders are divided ; for these are founded on typical genera, the names of which are made to furnish adjectives by the substitution of ece for the last vowel and whatever may follow it : for example, in the Order of the 170 SYSTEMATIC BOTANY. Ranunculaceee, we have the tribes Anemonece from Anemone, Ran- unculece from Ranunculus, Hellebores from Helleborus, &c. ; and in botanical works these names of tribes are commonly printed in italics like those of genera and species, while the names of families and all above them are printed in roman letters. The names applied to the larger divisions of the Vegetable Kingdom in Natural Arrangements are generally made as characteristic as possible ; but, as will be shown in the Section on Natural Arrangements, none of the single characters of such groups are absolute, and therefore no name founded on one character can be universally descriptive. Thus the name Monocotyledoues is applied to a most natural group, in which are, however, included one or more orders, as the Orchidacese, in which the embryo has no cotyledons. And it may be said that to an advanced student it is far more beneficial to regard all names as abstract signs, used rather to indicate certain plants or groups of plants with which he is acquainted, than as expressive of the characters of the plants to which they are applied. These observations on the nomenclature of the Orders and higher groups of plants are placed here for the sake of connexion with the remainder of the subject; but they will be better appreciated after acquaintance is made with the illustrations of them in succeeding Sections. Sect. 3. DESCRIPTION OF PLANTS. It is the business of every botanist who distinguishes and names a new species of plant to furnish an exact statement of the charac- ters by which it may be recognized by others. The most complete fulfilment of this requisition is supplied in what is termed a description of a plant, in which is given a detailed account of the external form, the arrangement and relations of all its organs, according to a fixed plan and in a fixed language, furnished by the terminology made use of in Morphology. In order to impress upon the mind of the student the principal points to be looked to in describing a plant, and thus to ensure completeness and accuracy of observation, we subjoin a list of the more salient characteristics which it is desirable to notice in writing a full description of a plant. Some of these are of much greater importance than others, inasmuch as they afford the means of grouping plants into genera and orders, not only phy- siologically but morphologically, &c., and furnish what are called dia- gnostic characters. From their great importance, much stress is deservedly laid on them ; hence, after enumerating the principal "characters " neces- sary to be ascertained in drawing up a full description, we shall insert illustrations of the "schedules'' introduced with so much success for teaching-purposes by the late Professor Henslow, and in which attention is drawn solely to those points of special importance. It must also be borne in mind that the terms used are such as are in general use, and are to be taken in their conventional sense, and not as DESCRIPTION OF PLANTS. 171 necessarily expressing the exact truth : thus, as has already been explained under the head of Morphology, when we say that one organ is inserted into another, it would be more correct to say that the one emerged from the other ; in the same way many cases of so-called cohesion and adhesion are shown, by the study of the progressive development of the flower, to be rather cases of arrested separation than of union of originally distinct organs. In describing a plant fully, a commencement is made with the root, from which we proceed to the stem, leaves, inflorescence, flowers, and, finally, the ripe fruit and seeds. In the case of the root the principal points to be looked to are : first its nature, whether true or adventitious; then, in succession, its form, direc- tion, size, degree and mode of ramification, duration, consistence, surface, colour, &c. Similar remarks apply to the stem and its modifications. Leaves require first to be noted as to their position, radical, cauline, &c. ; insertion, stalked or sessile ; possession or deficiency of stipules ; arrange- ment, alternate, opposite, &c. ; composition, simple or compound ; direction, duration, texture, colour, and surface. The blade of the leaf mast then be described as to its general form, outline, base, apex, margins, mode of vena- tion, size (especially in relation to the stalk, if present). The subdivisions of a compound leaf must be treated in the same manner as simple leaves. The petiole or leaf-stalk has to be noted as to its form, surface, relative size, fec. Stipules, as far as practicable, should be described in a similar manner to the leaves, as also should, mutatis mutandis, the leaf-buds. In their case, as also in the case of Jlower-buds, the mode of vernation or of (estivation, as the case may be, should be ascertained and recorded. As regards the inflorescence, the principal things to be considered are its position, direction, relative size as compared with the leaf, nature (definite or indefinite), ramification, form, number of flowers, duration, &c. The flower-stalks follow the same rule as the leaf-stalks ; but particular attention should be paid to the top of the flower-stalk (the thalamus) to see whether it be flat, convex, or concave. The bracts are described in the same manner as the leaves. In the case of the calyx and corolla, attention should be directed to their construction (cohesion), relative posi- tion (adhesion), form, direction, colour, venation, surface, size, absolute and relative, duration, odour, &c. Individual sepals or petals should be described in the same way as the leaves. Stamens should be described with reference to their insertion (adhesion), cohesion (free or united), number, position, arrange?nent,size (with reference to one another and to the other parts of the flower). Filaments present similar characters to those offered by the leaf- stalks, and are described accordingly. Anthers require attention as to their form, mode of attach- ment to the filament, shape and number of their lobes, their mode of dehis- cence, colour, surface, the form and peculiarities of the connective and of any appendages that may be present. The form, colour, and distinctness or cohesion of the pollen-grains should, if possible, be stated. This is not always practicable unless recourse be had to the compound microscope, when other peculiarities, then visible, should be noted, as will be further explained in the section on Physiology. After the stamens, the characteristics of the disk, if present, should be 172 SYSTEMATIC BOTANY. noted, and then those of the pistil as follows number of the constituent carpels, their isolation or cohesion and arrangement, their adhesion and rela- tive position, form, cavities, partitions, and mode of placentation. The styles require to be noted with reference to their position, number, size (relative and absolute), form, surface, colour, &c. Similar remarks apply to the stigma. The ovules differ in their position, mode of attachment, number, form, &c. The fruit follows the same rules as the pistil ; but, in addition, the texture, mode of dehiscence, and number of seeds must be noted. Seeds are described much in the same way as ovules, taking- care not to overlook any of the peculiarities presented by the coverings of the seed in the way of hairs, scales, arils, and the like : the interior of the seed also requires special attention, to see whether or not it be albuminous or exalbu- minous ; if the former, the nature and quantity of the albumen should be noted ; and in any case, where possible, the form, position, direction, size of the embryo and its parts, the nature and number of the cotyledons, &c. should be accurately ascertained. The student is recommended to take any plant he meets with, and endeavour to draw up a description of it with reference to the foregoing scheme. By comparing- the description of one plant with that of another he will familiarize himself with the main points of difference between one plant or one organ and another, and will learn to apply the appropriate term to each modification. The subjoined description of the common white Dead-Nettie (Lamium album) is given as an illustration of a tolerably complete description of the external peculiarities of a plant ; it may serve as a model to the student in drawing up similar descriptions. It is, however, advisable that he do not attempt too much at once. A bad or careless description is almost worse than none at all ; hence the beginner is recommended to make himself pretty thoroughly acquainted with the peculiarities of such organs as are most easily studied before passing on to organs such as ovules, &c., which require some considerable practice before their structure and characteristic features can be ascertained. Lamium album. A rather coarse hairy perenmal,with a shortly creeping stock, from the joints of which, especially on the lower surface, proceed at intervals numerous slender, fibrous, brownish roots. Stems 1-2 feet high, herbaceous, decumbent or ascending, fistular, four-sided. Leaves exsti- pulate, opposite, stalked, the upper ones nearly sessile, hairy, membra- nous, ovate-acute or acuminate, cordate, coarsely and irregularly toothed, unicostate, arch- veined, 2-3 inches long, 1-2 inches broad. Petiole less than half the length of the blade, channelled on the upper surface, rounded beneath. Flowers pure white, sessile, in axillary cymose whorls (verti- cillasters) of 6-10 or more. Calyx campanulate, of o sepals, united below into a tube traversed by 10 ribs ; limb divided above into five nearly equal, spreading, linear, ciliated segments, of which the uppermost stands slightly apart from the others. Corolla white, tubular, bilabiate, twice the length of the calyx ; tube curved, ventricose, as long as or longer than the calyx, scabrous inside, with a ring of hairs near the base ; upper lip erect, concave, notched, hairy on the outer surface ; lower lip spreading, 3-lobed, the middle lobe broad and 2-lobed, the two lateral ones small and pointed. Stamens 4, didynamous, epipetalous ; filaments downy, springing from the upper part of the tube of the corolla, partially concealed within the upper DESCRIPTION OF PLANTS. J 73 lip. Anthers innate, 2-lobed ; lobes superposed, oblong, blackish, introrse, dehiscing longitudinally; connective covered with white hairs. Pollen yellowish white. Ovary small, truncate, 4-lobed, 4-celled, encircled at the base by a pale green, cup-like disk. Ovules solitary in each cell, aua- tropal. Style single, basilar, thread-like, as long as the corolla, termi- nating in a 2-lobed stigma ; lobes of the stigma short, oblong, pointed. Fruit of four (or fewer by abortion), 1-celled, 1-seeded, indehiscent, blackish shining lobes or achenes. Seeds solitary, erect, inverted, exalbuminous. Embryo straight ; cotyledons large, plano-convex ; radicle short, inferior. Such descriptions are now usually given in a modern language when occurring in works descriptive of the plants of particular countries and intended for general use, &c. In general systematic works, or in isolated notices, published in periodicals or Transactions, addressed more particularly to proficients, the Latin language is usually preferred, as it is understood by botanists of all nations and is less vague in its application. Detailed descriptions are commonly given only where new spe- cies are established, or when an uncertain nomenclature is to be made clear and definite, in a monographic or a general systematic work. The classification of plants into genera, families, &c., in the Natural System, renders the repetition of the peculiar marks of these groups unnecessary in the characterization of the subordinate groups or forms. For this reason, characters and diagnoses com- monly replace the complete descriptions of species in ordinary descriptive botanical works, since, as the character of the genus includes those peculiarities of the floral organs which are common to all its species, and which constitute the bases of the genus, it is only requisite to connect with each species the character by which that species is distinguished from others. The following condensed description of the white Dead-Nettie, from Bentham's l Handbook of the British Flora,' will show how, when the cha- racters of the order and genus are known, a faithful portrait of the species, and one comprising the most conspicuous features only, may be drawn up: " A rather coarse hairy perennial, with a shortly creeping stock, and decum- bent or ascending branching stems, seldom above a foot high. Leaves stalked, coarsely crenate. Flowers pure white, in close axillary whorls of 6-10 or more. "Calyx-teeth fine, long, and spreading. Tube of the corolla curved upwards, and longer than the calyx, with an oblique contraction near the base, corresponding with a ring of hairs inside; the upper lip long and arched ; the lateral lobes of the lower one slightly prominent, with a long fine tooth." Then follows an account of the station in which the plant is found, and of its geographical distribution throughout this country and the continent. Value of Characters. Having gained a general idea of what points are to be looked to in drawing up a description of a plant, and having ac- quired a familiarity with the meaning and application of terms, it is par- ticularly desirable that the student should be able to form an estimate of the relative value and importance of characters for practical purposes ; for 174 SYSTEMATIC BOTANY. instance, those characters which serve to identify and distinguish large groups of plants are of more consequence than such peculiarities as pertain merely to small groups or to individual plants. With a view to fix the attention on the more important or cardinal characters, those which are of most use in drawing up a diagnosis of a plant or of a group of plants, a form of schedule is given ; and the pupil is recommended to make similar ones for himself, and by their aid to draw up an account of the more im- portant characters of any flowers he meets with, checking them and com- paring them with the descriptions given in books, or with the instructions of his tutor. These schedules should be kept for comparison with others relating to other plants ; and by this method a practical insight into plant-construction, and the relationships of one plant to another, may be more speedily and thoroughly obtained than by any other means. 'The schedules here inserted by way of illustration are filled up from a Common Buttercup (Ranunculus} and from a Dead-Nettie (Lamiuni). The cha- racters therein given are sufficient to enable the student to determine the orders to which the plants belong, which is the first and most important consideration j but they are not sufficient to indicate the genus, still less the particular species. To discriminate these minor groups, recourse must be had to the other peculiarities presented by the plants in question, as before detailed. DESCRIPTION OF PLANTS. 175 a SH , . ' Lri P n 1 UH - . "~^ i ) : S 1 : be E 3 t st d o 1 j : c . .2 ; ; i , 03 9 : M o o o : o ' c p* B 1 1 i | t g 'S 03 fl s 0) 3 J2 ' : g : ^j 03 *T3 : S i G a> B QJ ! - S S j . c : : s L. o 1 o O "*5 "t i t O i 3 C cx a ^5 ' >r w T J r c w 1 i 4 p c i J.J ^ST C c J. -.1 K i W-? 2 > , 1 g LI>O LlO U'l? 1 1 '= j ji i > c 1 r 1 > 1 Stamens Filame Ant.hfir IK S 1 J r ^ 1 3 | E ! \ n.f i | j i f! 3 S rr fc ( n t. T 1 | J d s o Q 55 1 * J >n T3 "5^ 8 d 2 i : - o TI C -i- 'I j ^ C , - OP 1 \ ) \ 1 ) 1 1 ^ ^ o rl z Insertion Emergen c e j JE 2 H % ! c B > t > ^ > s > 1 E 1 j B ! ; ji i a 1 1 T t I 8 1 E LI In "*l P P> c c i flj -s "S c a .1 .'2 1 c ~ iC ^^ J EP 5 oj 5 S ^^ ^ 3 o 1 g a ^ |g^ 02 j5 6 02 OQ 176 SYSTEMATIC BOTANY. Generic Character. The generic character is perhaps the most important element in Systematic Botany. It should contain a short description of the peculiarities of the group, so as at once to cha- racterize this as it exists in itself, and to furnish the means by which it may be distinguished from all other genera belonging to the same division of the Vegetable Kingdom. The following ex- ample of the character of the genus Campanula, Linn., as given in Endlicher's ' Grenera Plantarum,' will illustrate this : "Campanula, Linn. Calyx with an ovoid or suhspherical tube adherent to the ovary, the limb superior, five-toothed ; the teeth either flat at their margins or decurrent into lobes overlying the sinuses. Corolla inserted at the summit of the tube of the calyx, more or less campanulate, five- lobed or five-toothed at the apex. Stamens five, inserted with the corolla ; filaments broadly membranaceous at the base, and, with the anthers, free. Ovary inferior, three- or five-celled ; cells superposed to the lobes of the calyx. Ovules numerous, on pla,centas projecting from the central angles of the cell, anatropous. Style covered with quickly deciduous hairs ; stigmas 3-5, filiform. Capsule ovate or turbinate, 3-5-celled ; cells burst- ing near the top or bottom by a parietal valve turning upward. Seeds numerous, mostly ovate, flattened, more rarely ovoid and very small. Embryo orthotropous, in the axis of fleshy albumen ; cotyledons very short ; radicle next the hilurn, centripetal. " Perennial or annual herbs, sometimes low and tufted, sometimes erect, tall, many-flowered, diffused through all the temperate and cool regions of the northern hemisphere, forming a great ornament to meadows and groves ; radical leaves very often larger and more obtuse, with longer stalks; stem-leaves alternate, varying ; flowers mostly stalked, racemose, rarely spiked or in clusters, very often rather large, blue, or sometimes white in the same species." The first paragraph here contains the essential character of the genus ; the second paragraph is a description of the general cha- racters of the species belonging to it, which is usually appended to such complete generic characters. It will be observed that this generic character not only enables us to distinguish plants belonging to this group, but describes the genus so fully that we become acquainted with all its important peculiarities, while, being drawn up irrespectively of any Order, alliance, or class, it is equally available as material for any 'Natural or Artificial classification of Flower- ing plants founded on the floral organs, since it contains the information requisite for ascertaining its relations. Diagnosis. The diagnosis of a genus is -more limited in its nature and purpose. It is used, when genera are described under fixed systematic heads simply for distinctive purposes; and it is therefore confined to denoting what is absolutely necessary for this purpose. Thus, in Babington's ' Manual of British Botany,' the genus Campanula occurs under the head of the Order Campanulacea?, the character of which includes much of what is given in the generic DESCRIPTION OF PLANTS. 177 character of Campanula, above cited ; so that it suffices for the distinction of Campanula from its allied genera to give the following brief abstract, or diagnosis : " Campanula : Calyx 5-parted. Cor. mostly bell-shaped, with 5 broad and shallow segments. Anthers free ; filaments dilated at the base. Stigma 3-5-fid. Capsule not elongated, 3-5-celled, opening by lateral pores outside the segments of the calyx." It is seen at once that this diagnosis fails to furnish the complete notion of the genus which is obtained from the descriptive character, and that it does not suffice to indicate the position of the genus, either in a Natural or Artificial classification. On the other hand, for its own especial purpose (that is, of indicating the distinctions between allied genera), it may be even still more reduced, as is often done in works describing the plants of a limited district, where only a few genera occur in the natural order ; for example, we might give diagnoses of the British genera of Campanulacese in this way A. Corolla rotate, segments linear ; anthers cohering at the base. 1. Jasione. Corolla rotate, with linear segments j anthers free. 2. Phyteuma. B. Corolla mostly bell-shaped, with broad and shallow segments ; an- thers free. Capsule not elongated, opening by lateral pores outside the seg- ments of the calyx 3. Campanula. Capsule linear-oblong, prismatic, opening by lateral pores be- tween the segments of the calyx 4. Specularia. Capsule half-superior, opening by 3-5 valves within the seg- ments of the calyx 5. Wahlenbergia. Specific Character. The specific character of a plant should mention all the constant distinctive peculiarities of a species. On the one hand, it should exclude the generic characters which ally it to other species of the same genus ; on the other, it should exclude the inconstant characters which distinguish its own varieties. But the character of its ordinary varieties, if such exist, may be given in a supplementary paragraph, like that appended to the full generic character. The distinctive characters of species are usually found in the organs of vegetation, as the root, stem, leaves, bracts, and inflorescence, or in the habit or duration of the plant. The floral organs mostly only give specific characters in their less im- portant peculiarities as in the shape and relative magnitude of the petals, the external characters of the fruits and seeds, &c. the more remarkable peculiarities being of generic value. The supplementary notices appended to the strict character of the spe- cies generally relate to the ordinary dimensions of the plant, the " colour, taste, smell, &c. of its organs ; these are the marks by which the varieties are usually characterized, as will be seen by referring to any catalogue of varieties of the ordinary cultivated vegetables. 178 SYSTEMATIC BOTANY. The specific character will necessarily vary in length according to the richness of a genus in species, some containing many hundreds, while others comprise but a single one. When the genus contains but a single species, as the Hop (Humulus Lupulus), the generic character alone suffices for distinguishing it ; but a specific character is even then given with advantage, indicating points which are not included in the strict generic character. Where a large number of species exist, the genus is generally broken up into artificial sections, characterized by some mark occurring regularly in a certain number, w r hich are thus placed under one head : this saves the necessity of repeating that character for each species. It is also common in modern works to combine a diagnosis with the specific character, by marking in italics the especial distinctive marks of each species occurring in a particular group. The following examples will make this more clear : Of Syringa, L., only six species are described in De Candolle's ' Pro- dromus,' being all that were known in 1844. The specific character of the common Lilac, Syringa vulgaris, could thus be given in a few words : " S. vulgaris, L. Leaves cordate or ovato-cordate, quite smooth and of even colour ; limb of the corolla subconcave." Four varieties are characterized, chiefly distinguished by the colours of the blossoms. Turning to the genus Campanula in the same work, we find no less than 182 species. Being a very natural genus, the species are kept toge- ther under one generic name, but, for convenience, they are arranged in sections and subsections. Thus fifty-eight of them are characterized by the presence of appendages on the sinuses of the calyx, such as we find in the garden Canterbury Bell (Campanula Medium), while the remainder are without these. The second section, of 124 species (among which are included all our native kinds), is further divided into subsections, cha- racterized principaUy by the peculiarities of the capsule, and these, again, into groups according to the kind of inflorescence, &c. ; so that when we come to the specific character itself none of these points have to be re- peated, and the definitions are restricted within very narrow limits, as for instance : " C. rotundifolia, L. Radical leaves stalked, cordate, rounded, crenato- dentate ; stem-leaves linear or lanceolate ; teeth of the calyx awl-shaped, erect, one-third the length of the bell-shaped corolla." In a work devoted to a limited flora, as that of Britain, where there exist only eight species of Campanula, we may adopt the sectional divisions, and limit the specific character as above, or give a longer character, in- cluding the marks of the sections; the latter plan is the better, where space is not an object, since it makes the character itself more instructive. Thus, in the ' British Flora/ we find " C. rotundifolia, L. Glabrous ; root-leaves subrotundo-cordate, cre- nate (very soon withering), lower cauline ones lanceolate, upper linear entire ; flowers solitary or racemose, drooping ; calyx-segments subulate ; capsule drooping, with the clefts at the base." In Babington's ' Manual,' on the contrary, where the subsections founded on the capsule are adopted, this mark is omitted in the essential character : " C. rotundifolia, L. Radical leaves cordate or reniform, shorter than their stalks ; stem-leaves linear, the lower ones lanceolate ; flowers one or DESCRIPTION OF PLANTS. 179 more, racemose ; corolla turbinate-campanulate. Stem 6-12 inches high. Radical leaves soon vanishing j corolla blue ; calyx-segments linear- subulate." This example further illustrates the method of giving a diagnosis at the same time, by italicizing the characters by which the species is distin- guished from its nearest allies ; it also shows the manner in which expla- natory or descriptive notices are added in a supplementary paragraph to the essential specific character. Lastly, if we have to deal with a limited number of species, such as the British Bell-flowers, to which we have just referred, we may, for simple purposes of distinction, construct a diagnostic table, like that above given for the genera of Campanulacese. Flowers sessile, in terminal or axillary clusters ; cap- sule sessile, erect, with the pores at the base . . C. glomerata. Flowers in racemes or panicles ; capsule stalked. Capsule nodding, with the pores at the base. Flowers in a unilateral raceme, segments of calyx ultimately reflexed C. rapunculoides. Flowers racemose, segments of calyx always erect. Peduncles 1-flowered C. latifolia. Peduncles 2-3-flowered C. Trachelium. Flowers on long slender stalks, solitary, or in a lax few-flowered corymbose raceme . . C. rotundifolia. Capsule erect, with the pores just below the segments of the calyx. Segments of the calyx entire. Segments of the calyx lanceolate; raceme few-flowered, or flower solitary . . C. persicifolia. Segments of the calyx awl-shaped ; flowers in an erect racemose panicle .... (7. Rapunculus. Segments of the calyx toothed at the base j flowers panicled, erect, on long stalks . C. patula. A few of the general rules observed in writing descriptions of plants may be mentioned here, as explanatory of certain techni- calities which will be met with in systematic works. The generic name is always commenced with a capital letter, while that of the species is usually written small : but we find in most books a capital letter to the specific name, 1, where this name is the appellation of another existing or suppressed genus used ad- jectively, as Agrimonia Eupatorium, Mentha Palegium, &c. ; 2, where the specific name is formed from a proper name, either as the genitive case of a substantive or in the adjective form, as in Scirpus Savii and Carex Davalliana. Specific names derived from coun- tries are now usually written small, as /Silene anglica. When a generic character is written in Latin, the descriptions of the organs are all put in the nominative case ; in a specific cha- racter they are put in the ablative. w 2 180 SYSTEMATIC BOTANY. When describing a species, it is usual to subjoin its habitation (Habitat) that is, the nature of the places in which it is usually found, such as " Woods," Dry hilly places," " Elvers," &c. In general systematic works the native country or province is stated ; in works relating to limited districts, special localities are given for rare plants. The following marks and abbreviations are commonly in use to indicate certain other points : or A =an annual plant. or 13 = a biennial. or P =a perennial. Sh=a shrub. T =a tree. c?, a male flower. 5 , a female flower. ^ , an hermaphrodite flower. $ 5 ) a monoecious plant. c? - $ ? a dioecious plant. The time of flowering is indicated by numbers, referring to the months, as 6-8 or vi-viii= June to August, &c. (See also p. 103.) Many other signs are met with in Systematic works, but they are very often used in different senses by different authors, so that no general ex- planation of them can be given moreover the sense in which they are used is generally explained by the author. CHAPTER II. SYSTEMS OF CLASSIFICATION. Sect. 1. ARTIFICIAL CLASSIFICATION OF PLANTS. An arrangement of all known species of plants in a series of classes, constituted upon certain fixed principles, forms what is termed a System of Vegetables. The classification of plants by generalization, the Synthetic or Natural Method, is adopted in all cases in forming the groups of the lowest rank, namely Genera. These are established by the combination of a number of allied species under one name, on account of their affinities ; and, as we have already mentioned, the same genera are used in all Classifications. From this point Systems diverge. The Natural Method is pur- sued further on the same principles of generalization, where the object is to systematize acquired knowledge, mark the agree- ments and determine if possible the lineage of plants. Where, on ARTIFICIAL CLASSIFICATION. 181 the other hand, it is chiefly desired to mark out the differences of plants, in order simply to their easy recognition, Artificial Methods are resorted to, which are carried out by a principle of analysis, whereby the whole mass of known forms is taken and gradually parcelled out into Classes, Orders, &c., according to their agree- ment or difference in certain fixed characters. Most of the older systems were more or less Artificial, the earliest commencing with the division of plants into Trees, Shrubs, and Herbs, Land -plants and Water-plants, and the like. As advances were made, organs of more and more importance were chosen to furnish characters ; and we find plants subsequently classed by their corollas, by their fruits, &c. ; but in none of the systems pro- posed before the time of Linnaeus do we find one given principle carried out through the whole. The Linnsean System. "When Linnaeus entered upon his labours, there lay before him a mass of information in a very unmanageable condition. His reforming genius introduced order, in the first instance, by the substitution of short fixed names for species, on the binomial plan, by the definition and secure establishment of im- perfectly characterized genera and species, and then advanced to the necessary task of arranging the genera so as to render them recognizable. The artificial methods founded on the floral enve- lopes &c. had proved insufficient ; and therefore he turned to the essential organs of flowers, the physiological importance of which he himself contributed greatly to establish. The selection of these organs resulted in the formation of an Artificial System in which a fixed principle is regularly carried out, and which, from the phy- siological importance of the characters employed, approaches in certain of its coordinations to a natural arrangement. Species and Genera form the foundation of all Systems. The object of the Linnsean System was to arrange genera in groups characterized by simple striking marks, so that the existing description of a given plant might be readily found, or the de- scription of a new plant might be placed where it would be easily referred to. Such marks Linnaeus obtained in the essential or sexual organs of plants (in flowers, the stamens and pistils}, whence his System is sometimes called the Sexual System. The highest or most general groups, which he called Classes, are founded on the conditions of the stamens. These Classes are subdivided into Orders, founded either on the conditions of the pistils or upon secondary characters of the stamens. The orders include the Genera (in large Orders grouped into sections according to various artificial characters). The Linnaean Classes are twenty-four in number, of which the first twenty-three include all Flowering Plants : the 182 SYSTEMATIC BOTANY. twenty-fourth, Cryptogamia, including all Flowerless Plants, was a chaos when first established, and its subdivisions were not then definable by single characters. As the Linnaean system is no longer in use, further mention of it is not needed. Sect. 2. NATURAL CLASSIFICATION or PLANTS. In this method of classifying we pursue the same path by which we arrived at the genera, and combine these into more general groups, not according to arbitrarily chosen or isolated characters, but according to their natural affinities that is, the agreement in their total organization, and consequently their presumed degree of kinship. (Jenera are thus gathered together into Families or Orders, these into Cohorts and Classes, and finally the entire Vegetable Kingdom becomes marshalled into a few Provinces or Subkingdoms. It is evident from this, that a Natural System founded on a perfect knowledge of all existing plants would present to us a kind of abstract picture of the Vegetable Kino'dom, in which all its essential characters would be represented in their real proportions, places, and connexion. Not only, however, are we far from being acquainted with all exist- ing plants (not to mention the numerous kinds now extinct), but the essential peculiarities of a vast number of the known plants have been as yet but imperfectly studied. Hence we have at present various plans for* the Natural Arrangement of plants, presenting peculiarities depen- dent upon the amount of knowledge, or the peculiar views, of their re- spective authors ; which plans or Systems must be regarded as so many rough draughts or sketches, to serve as material for the elaboration of the true and complete Natural System. As the principles of classification are fully recognized, and as the amount of plants thoroughly known is already very large, there is a close agreement in the general features of the dif- ferent "Natural Systems," and especially in the manner in which the Orders of plants are defined. The chief diversities of opinion arise out of the different estimations of affinities and differences of the families. Value of Characters. To characterize the Natural Method more distinctly, it must be added that especial attention is paid to the relative importance of the characters presented by each plant, a determinate scale being formed, in which the organs are ranked according to their "congenital" or "acquired" origin, their phy- siological importance, the complexity of their construction, and their comparative invariability. Congenital characters are common to the largest number, and are the most constant, hence the most important. Thus, while species of the same genus, distinguished generally by the external characters of their vegetative organs, are combined by likeness in their flowers, genera (in which difference of the floral envelopes, or of the external character of the fruit, or some such character exists) are NATURAL CLASSIFICATION. 183 combined into an Order on account of the agreement in the structure of the ovary and its relations to the floral envelopes. The characters of seeds, and more particularly of the embryos, give a still higher divisional cha- racter. These characters of successively higher groups are marked in organs of progressively higher physiological and morphological impor- tance, affinities between such organs being proportionately more valuable. But they possess this value not merely on their own account ; for if that were the case, the method would be still to a great extent artificial : they indicate the coexistence of proportionate agreement in the total organi- zation, which renders them exponents not merely of the affinities of the plants in respect to the particular structure to which they belong, but of all their affinities, and of the rank which a given plant holds in the Vegetable Kingdom. As a general rule, it is found that the agreement of the total organization of plants is generally proportionate to the phy- siological value of any given organs in which they agree ; or, in other words, agreement in the structure of any given organ indicates general agreement in all the organs of less importance than itself. The agreement here referred to is of course a general structural agreement, a relation to a common type not a resemblance excluding the multifold minor diver- sities which present themselves within the limits of almost every type. Practically, moreover, we have another principle to keep in view, which indeed, while it affords as it were the verification of the in- ductions of the above principle, is our sole guide in dealing with the subdivisions of the more comprehensive types. This is the rule that the closest affinities are marked by the agreement in the majo- rity of characters of eqtlal importance ; or if the characters, as is more commonly the case, are of unequal importance, the principle of decision by the majority is carried out by ascertaining the pro- portionate values of the organs in which agreements and differences exist, and striking a balance as with equal factors. Many of the older botanists had attempted to construct a Natural Sys- tem ; and Linnaeus left a sketch or fragment of one, in the form of a list of names of families without definitions, regarding its realization as the ultimate aim of Botany. Many of the families in these older Systems are grounded almost exclusively on " habit," or general external character. The two Jussieus, Bernard and Antoine-Laurent, have the merit of the discovery of the only principles upon which a really Natural System can be founded. And so accurately did A.-L. de Jussieu carry out these prin- ciples in his arrangement of the then existing genera, that the families which he established are still almost all received into our present Systems, where some of them are indeed broken up into smaller groups, but where the greatest increase in the number of families arises from subsequent discoveries. The characters of the natural Families established in this way will be found to be far less exact and definite than those of the Linnsean classes and orders, and by no means so rigid even as those of natural genera. The cha- racter of a family is founded on the totality of its essential characters, and includes the essential characters of agreement of all its genera. The genera contained in most of the families exhibit a considerable range of differences j 184 SYSTEMATIC BOTANY. allowance must be made for these ; and this gives a laxity to the family character which is puzzling- to the beginner. For example, the family Ranunculaceae is very natural ; but we find in its character a certain range of difference allowed for in the sepals, petals, pistils, and fruit ; the insertion of all these, however, and that of the stamens, is fixed, and so is the cha- racter of the seed. Similar conditions occur in most other families. The decision as to what family a genus is to be referred to is made according to the principle of majorities : whichever it agrees with in most of its cha- racters (say, even three out of five), to that family it belongs. Great diffi- culty, however, exists in certain cases from a vast series of genera running into one another by almost imperceptible gradations, and this in different directions. A considerable number of these agreeing closely are associated into a family ; another similar group forms another family, and so on ; and then, in the course of time, sundry intermediate genera present themselves, which connect the established families, and which it is difficult to place by the usual choice in either one or the other, the characters being balanced. Thus the Natural family Loganiaceae is connected by " aberrant " genera with Rubiaceae, Gentianaceae, Scrophulariaceae, and other families which are truly natural, but which in this way come to be separated by somewhat indefinite boundary-lines. The fact is, that the Vegetable Kingdom is a whole, the families having seldom, a distinct isolated existence, except in the minds of botanists. It may be presumed that they are all variations from one or a few original stocks, and thus have numerous intermediate or connecting links ; and we must regard them as analogous to countries on the globe, which are parcelled out under distinct names, but most often adjoin and run into one another, being only separated by an arbitrary boundary-line. Some, indeed, lie off from the rest, like islands, the inter- vening links being extinct ; but these are the exceptions. Such excep- tions are found among the families which were established by the older botanists, in which the essential agreements are accompanied by a striking character of external habit, as in the Grasses, the Umbelliferae, the Com- positae, the Leguminosae, the Coniferae, the Palms, &c. Such remarkable peculiarities as these families possess mostly prevent them being broken up Into smaller groups, as has occurred to many of the earlier orders of large extent ; and most botanists prefer to distribute these genera into suborders rather than discard the characteristic general name. Examples of these are found especially in the Leguniinosae, RosaceaB, and Compositae. The Families or Orders are for the most part the same, in all essential respects, in all existing "Natural Systems." A conside- rable diversity presents itself in the modes in which different authors have grouped these into Classes or Alliances. These, how- ever, are still Natural groups, as are also those of still higher gene- rality indicated in the chapter on General Morphology. But all writers on Systematic Botany have found it requisite to group the Orders or Classes of Flowering Plants into sections of somewhat less generality than Dicotyledons and Monocotyledons, as these respectively include series of families so extensive as to be incon- venient in practice if left undivided. The members of these series, however, are so intimately connected together by their natural THE JUSSIEUAN SYSTEM. 185 affinities, that it has been found indispensable to have recourse to certain arbitrary or artificial characters for the foundation of the sections characters derived chiefly from the conditions of the petals and stamens. The nature of these Sections will be best un- derstood from the examples which follow. The Jussieuan System. Jussieu established his primary divi- sions of the Vegetable Kingdom on characters which, although not unexceptionable, define really natural groups, which are found under different titles in all Natural Systems. The characters were the absence or presence of the embryo, and its structure when present, in the seed. On these characters stood the three divisions Acotyledons (plants without an embryo), Monocotyledons, and Dico- tyledons. The first of these names is bad, as founded upon a nega- tive character ; but the plants which it included were imperfectly understood in the time oi: Jussieu ; the Acotyledons correspond to the Cryptogamia of Linnaeus, which are now by more complete analysis distributed into two sections, divided by even more im- portant characters than the Monocotyledons and Dicotyledons. The other two divisions are still retained, with very slight modifi- cations, in all Systems, but are subordinated under divisions founded on more important characters. The following Table exhibits Jussieu's arrangement : Class Acotyledons ............................................ 1. Stamens hypogynous ........ II. perigynous ........ III. epigynous '. ......... IV. Stamens epigynous .......... V. perigynous ........ VI. hypogynous ..... '. . . VII. ( Corolla hypogyuous ........ VIII. perigynous .......... IX. MONOPETALOUS ( Anthers I Monocotyledons f APETALOUS Dicotyledons .] I epigynous ( distinct ( {Stamens epigynous .......... XII. hypogynous ........ XIII. perigynous ........ XIV. I DICLINOUS, irregular ........................ XV. The three primary divisions here are natural ; the Classes must be re- garded as artificial ; the Families, however, into which the latter are divided, are natural groups, and to a great extent are retained in more modern systems. The families of Jussieu were more carefully defined, corrected, and extended by liooert Brown, whose researches contributed most essentially to the establishment of the Natural System ; but he did not attempt to establish any general plan for their coordination in Classes. 186 SYSTEMATIC BOTANY. De Candolle's System. Aug. Pyrame De Candolle endeavoured to classify the Vegetable Kingdom on principles more in harmony with the knowledge of the structure of plants accumulated since the promulgation of Jussieu's System. De Candolle's System has become very generally used, on account of its having been adopted in the great Descriptive work which he commenced, the ' Prodromus Systematis Naturalis K-egni Vegetabilis/ a description of all known species of plants. His subdivisions of the Exogens (or more pro- perly Dicotyledons) are retained in many works. They are artificial, like the "Classes" of Jussieu, but are, like them, convenient for the distribution of the families into groups of manageable dimensions. They are four in number, and founded on characters of the floral envelopes, viz.: 1. THALAMIELOE^E, in which the petals are distinct and (like the stamens) inserted on the receptacle (hypogynous) ; 2. CALYCIFLOR^E, with the petals distinct or coherent and (with the stamens) inserted on the calyx (perigynous) ; 3. COROLLIFLOILE, with the petals coherent, and inserted on the receptacle (the stamens being inserted on the corolla) ; and, 4. MONOCHLAMYDEJE, or plants with a perianth or a single circle of envelopes. In De Candolle's enumeration of the families, which had greatly increased in number from Jussieu's list, the reverse order of sequence is followed, the higher plants standing first. As regards this point, however, it is a misconception to place the Thalamiflorce first among the Dicotyledons, since they are manifestly inferior to the Calyciflorce, and even to the Corolliflorce. During the last forty years a great many attempts have been made to distribute the Orders more satisfactorily into Classes and primary Divisions. Endlicher, Bartling, Meisner, Brongniart, Lindley, and many other authors have published Systems of their own. Endlicher's System. That of Endlicher has been extensively used, and, moreover, is the basis of arrangement in his great * Genera Plantar um.' Begion 1. Thallophyta. Sect. I. PEOTOPHYTA; II. HYSTEEO- PHYTA. Region 2. Cormophyta. Sect. III. ACEOBRYA. Cohort I. Acrobrya anophyta; 2. Acrobrya pro:ophyta ; 3. Acrobrya hysterophyta. Sect. IV. AMPHIBEYA. V. ACEAMPHIBEYA. Cohort 1. G-ym- nospermese ; 2. Apetalae ; 3. G-amopetalee ; 4. Dialype- talae. The cohorts are subdivided into classes, and these again into orders. PROPOSED ARRANGEMENTS. 187 Brongniart's System. The arrangement of Brongniart is much followed in Prance. Its general character may be understood from the following table : Division I. Cryptogamae. Branch 1. AMPHIGENJE (Thallogens) ; Branch 2. ACROGEN^S. Division II. Phanerogamae. Branch 3. MONOCOTYLEDONES. Series 1. Albuminosse ; 2. Ex- albumiiiosse. Branch 4. DICOTYLEDONES. Subbranch 1. Angiospermce. Series 1. Gamopetalae : i. Perigynae ; ii. Hypogynae. Series 2. Dialy- petalae : i. Hypogynae ; ii. Perigynae. Subbranch 2. Gymnospermce. Lindley's System is the one proposed by its distinguished author in his ' Vegetable Kingdom.' Although the system itself was never generally adopted, the book itself is an admirable encyclopaedia on all points relating to Systematic Botany and the uses of plants up to the date of publication. Lindley's main groups were : I. THALLOGENS ; II. ACROGENS ; III. BHIZOGENS ; IV. ENDOGENS ; V. DICTYOGENS ; VI. GYMNOGENS ; VII. EXOGENS ; the latter being subdivided into Diclinous, Hypogynous, Perigynous, and Epigynous subclasses. The subclasses w r ere again divided into alliances, and these into orders. The special peculiarity of this system is the formation of a group for certain root-parasites, destitute of true leaves ; and of Dictyogens a class of plants with the netted venation of Exogens and the ternary flowers of Endogens. Bentham and Hooker's System. Since the publication of the * Vegetable Kingdom ' a very important work on Systematic Botany has been commenced by Mr. Bentham and Sir Joseph Hooker, entitled Genera Plantarum.' This work, so far as at present published, comprises a description, in Latin, of all the known genera of Polypetalous and Gamopetalous Exogens, together with analy- tical tables admitting of the ready determination of any particular genus, notes of aberrant or exceptional forms, &c. Their scheme is more fully explained in the English translation of Le Maout and Decaisne's ' General System of Botany/ edited by Sir Joseph Hooker. Its main features are given in the following table. The arrangement of the Monocotyledons, however, is taken from Mr. Bentham's paper on the classification of Monocotyledons, in the ' Journal of the Linnean Society ' for November 1876. 188 SYSTEMATIC BOTANY. Subkingdom I. PHANEROGAMIA. Class I. Dicotyledones. Subclass I. ANGIOSPERMEJE. Divi- sion 1. Polypetalce. Series 1. Thalamiflorse; 2. Disciflorae; 3. Calyciflorae. Division II. Monopetake. Series 1. Epi- gynae ; 2. Hypogynae v. Perigynae. Division III. Apetalce. Series 1. Hypogynae; 2. Epigynae v. Perigynse. Subclass II. GrYMNOSPERHEJE. Class II. Monocotyledones. Series 1. Epigynae; 2. Coronariae; 3. JXudiflorae ; 4. Grlurnales. Subkingdom II. CRYPTOGAMIA. Class III. Acrogens. Class IV. Thallogens. Subordinate to the " series " are f( cohorts/' or groups of orders of equal value, though with different limitations, to the " alliances " in Lindley's 1 System.' The only point which requires explanation here is the series Disciflorce, which includes those polypetalous hypogynous orders in which there is a conspicuous hypogynous disk or series of glands, into or be- tween which the stamens are inserted. Braun's System. In Germany the classification of A. Braun is now much followed. The following are bis main groups of Phane- garns as modified by Hanstein, Sachs, and others : DICOTYLEDONES. Mono- JulifloraB. chlamydeae. Aphanocyclae. Tetracyclae. Perigynae. Piperinea3. Serpentariese. Hydropeltidinea3. Gamopetahe. Calyci- UrticinesB. Khizantheaa. PolycarpaB. Anisocarpae. flora?. Amentifene. Cruciflora3. Isocarpae. Corolli- flora3. (B. EleutJiero- petnlce. Eucyclae. Centrospermse. Discophorae. Juliflorse correspond nearly to Amentales, and are characterized by spicate or amentaceous inflorescence, diclinous flowers, and mono- or achlamydeous flowers. Monochlamydeae have a well-marked perianth of one row ; Aphanocyclse have calyx and corolla, the parts of the flower (except in some cases the carpels) being arranged in spiral cycles. In Tetracycla3 the parts of the flower are in whorls. This group comprises CLASSIFICATION OF CEYPTOGAMS. ] 89 the Thalamifloral, Calycifloral, and Corollifloral divisions of De Candolle. Perigynre : perianth tubular below, bearing the stamens, and free from or adherent to the carpels, In this group the Calycifloraa have a single perianth, the Corolliflorae a calyx and corolla. Classification of Cryptogams. This is in a transitional state. The following is the latest arrangement, adopted by Sachs. It will be seen that the orders are arranged in two parallel series, according to the presence or absence of chlorophyll. Group I. Thallophyta. Class 1. Protophyta. With chlorophyll. Without chlorophyll. CyaiiophycefB. Schizomycetes. Chroococcacea3. Sphrerobacteria. Oscillatoriese. ]\1 icrobacteria. Scytonemeae. Desmobacteiia. Nostocaceae. Spirobacteria. Rivulariaceae. Talmellacece. - Euglenea. Saccharomyces. Class 2. Zygosporeae. A. Conjugating cells motile. Volvocinefp, Myxomycetes. \_Hyd rodictyea. ] Confervacece. Ulvacece. B. Conjugating cells stationary. Conjuf/at(p. Zyyomycetes. Desmidieae. Mucorini. Diatomaceae. Piptocephalidae. Mesocarpea3. ZygneuiesB, Class 3. Oosporese. Spli(crop 7 ea. CccloUastce. Fucacece. \ L Ph(cosporecB.'] 190 SYSTEMATIC BOTANY. Class 4. Carposporeae. With chlorophyll. Without chlorophyll. Cohoch&tce. Ascomycetes. Gymnoascus. Floridecs. Discomycetes. Nemalieae. Erysiplieae. Ceramieaa. Tu'beracese. Dudresnaya. Pyrenomycetes. Lichenes ? Characece. JEcidiomycetes. Basidiomycetes. Exobasidium. Tremellini. Hymenomycetes. Gasteromycetes. Group II. Cormophyta. Series I. BEYOPHYTA. Class 1. Musci. Class 2. Hepaticse. Series II. PTEKIDOPHYTA. Class 1. Eilicales. i. Stipulate. Ophioglossese. Marattiaceae. ii. Filices. iii. jRhizocarpece. Class 2. Equisetacese. Class 3. Dichotornae. i. Lycopodiacece. Lycopodieae. Psiloteas. Phylloglosseas. ii. Liyulatce. Selaginelleaa. Isoeteee. Caruel's System. Quite recently an arrangement has been pro- posed by Professor Caruel, based on the circumstance that there are in the same individual plants sexual forms or stages, male or female as the case may be, and an asexual or neutral form ; thus in Phane- rogams the asexual form is the embryo developing indefinitely and becoming ultimately an adult plant, which latter produces a male form, the pollen, and a female form, the ovule, which becomes a seed with definite evolution, containing " oospheres " or germinal vesicles in a closed " oogoniurn " or embryo-sac. The following are the outlines of the scheme, which we give in this place, though CARTJEL'S ARRANGEMENT. 191 it cannot be understood by the pupil until after lie has made himself acquainted with the morphology and physiology of Cryp- togams and Phanerogams and the details of the reproductive pro- cess in the several orders. Caruel's primary groups are : I. PHANEROGAMS. Plants trimorphic, one form neutral, pro- ducing agamically two sexual forms, male and female respectively ; neutral form originating from a fertilized oosphere and developing into a pro-embryo, like the embryo originating longitudinally ; evolution indefinite. Male form represented by the pollen in the anther. Female by the ovule, ultimately the seed : evolution defi- nite, containing the oospheres in a closed oogonium. II. SCHISTOGAM^:. Plants trimorphic. Neutral form origina- ting from a fertilized oosphere, developing, like the embryo, trans- versely : evolution indefinite. Male form a vermiform phytozoon (spiral spermatozoid) formed within an antherocyst. Female form an oogemma, then a seminulum, with definite evolution, containing an oosphere in an open oogonium. (Characeae.) III. PROTHALLOGAMJE. Plants trimorphic. Neutral form pro- duced from a fertilized oosphere, developing, like the embryo, trans- versely : evolution indefinite. Male form a vermiform phytozoon formed within an antheridium. Female form a spore, developing into a prothallus : evolution definite, containing a naked oosphere within an archegonium. , (Vascular Cryptogams.) IV. BRTOGAMJB. Plants trimorphic. Neutral form originating from a fertilized oosphere, developing, like the embryo, longitu- dinally : evolution definite. Male form a vermiform phytozoon from an antheridium. Female form a spore developing into a thallus or " cormus :" evolution indefinite, and containing a naked oosphere in an archegonium. (Muscineae.) V. GTMNOGAMS. Plants di-, trimorphic. In the trimorphic form the neutral form is an oospore arising directly from a fertilized oosphere : evolution indefinite. Male form a zoosporiform phyto- zoon from an antheridium. Female form a spore developing into a thallus : evolution indefinite, containing an oosphere in a naked open oogonium. In the dimorphic plants, two sexual forms only, the male a phytozoon or pollinidium. In the monomorphic plants a single form without sexual distinction : evolution definite or in- definite. (Cellular Cryptogams.) In the following pages the arrangement adopted is, for Dicoty- ledons mainly that of De Candolle, for Monocotyledons that of Bentham. 192 SYSTEMATIC BOTANY, VEGETABLE KINGDOM. Subkingdom I. PHANEROGAMIA. (Flowering Plants.) Class I. DICOTYLEDONES. (Exogens.) Subclass i. ANGIOSPEEMIA. Division 1. Polypetalae. Series 1. THALAMIELORJS. 2. CALYCIFLOBjE. Division 2. GamopetalaB or Corolliflorae. Series 1. INTERNE or EPIGYN^;. 2. STJPEILE. 3. DICARPI^E. Division 3. ApetalaB or Incomplete. Series 1. SUPERS. 2. INTERS or EPIGYTO:. Subclass ii. GYMNOSPEEMIA. Class II. MONOCOTYLEDONS. (Endogens.) Division 1. Petaloideae. Series 1. EPIGYNJE. 2. CORONABIE^E. A. Syncarpiae. B. Apocarpiae. Division 2. Spadiciflorse. 3. Glumiflorae. Subkingdom II. CRYPTOGAMIA. (Flowerless Plants.) Class I. CORMOPHYTA. (Acrogens.) Division 1. Vascularia. Series 1. ISOSPOEIA. 2. HETEEOSPOEIA. Division 2. Muscineae. Class II. THALLOPHYTA. (Thallogens.) Division 1. Algae. 2. Fungi. In the following systematic description of the Natural Orders, the characters of the most important are given at length, with the necessary particulars respecting their affinities, geographical distribution, and the qualities of the more important plants they contain. To most is prefixed a short diagnosis ; and a similar diagnosis, or a few explanatory remarks, DICOTTLEDONES. 193 printed in smaller type, are accorded to those Orders which either are not marked by very decided characters, or which do not demand so much attention from the beginner. In most cases the views of other botanists as to the position and limitation of the groups are briefly mentioned. Tinder each Order are placed the names' of one or more genera which furnish good illustrations and which are generally accessible for practical examination. CHAPTER III. SYSTEMATIC DESCRIPTION OF THE NATURAL ORDERS. THE VEGETABLE KINGDOM. SUBKINGDOM I. PHANEROGAMIA, or FLOWERING PLANTS. Plaiits producing stamens and pistils in association or separately, and forming seeds containing an embryo. CLASS I. DICOTYLEDONES. Flowering Plants, with stems (when woody) having pith and bark separated by a compact layer of wood, which, in perennial plants, receives annual additions on the outside, beneath the bark ; leaves with the ribs mostly distributed in a netted pattern and generally diminishing in size as they branch ; parts of the floral circles mostly 5 or 4, or some multiple of those numbers, rarely 3 ; embryo with a pair of cotyledons and a radicle, which is developed into a tap-root in germination. The typically complete floral formula, supposing the parts to be uncomplicated by adhesions, irregular growth, multiplication, &c., is S5 P5 A 5 G5, in regular alternation. SUBCLASS I. ANGIOSPEEMIA. Flowering Plants, with the ovules formed in closed ovaries. Endosperm formed after fertilization. Pollen-cells not dividing prior to the emission of pollen- tubes (see under " Reproduction "). Division I. Polypetalae. Petals distinct, rarely absent or united. Exceiaf ions. Hooker notes the following exceptions. Apetalous flowers occur in some species of Menispermaceee, Caryophyllaceas, Malvaceae, feterculiaceee, Tiliaceae, Rutaceae, Simarubaceae, Burseraceae, Olacacese, Celastraceae, Saxifragaceae, Crassulaceae, Myrtaceae, Passifloraceae. Ape- talous flowers also may be met with in some Ranunculaceae, Maguoliaceae, Berberidaceae, Sarraceniaceae, Papaveraceae, Cruciferae, Canellaceae, o SYSTEMATIC BOTANY. Fig. 332. Fig. 331, Fig. 333. Fig. 330. Netted-veined leaf of a Dicotyledon. Fi|. 331. Quinary plan of the flower, the parts regularly alternating. Figs. 332 & 333. Dicotyledonous embryos. Fig. 335. Fig. 334. Figs. 334-338 are illustrative of the Subclasses of Dicotyledons. Fig. 334. Thalamiflora (Ranunculus}. Fig. 336. Calyciflorse, epigynous (Fceniculum). Fig. 335. Calyciflorae, perigynous (Prunus\ Fig. 337. Corolliflorse (t-ymphytum). Fig. 338. Incomplete (Monochlamydese) ( Ulmus). THALAMIFLOR^J. 195 Bixacese, Violaceae, Zygophyllaceae, Geraniaceae, Rhamnaceae, Sapindaceae, Terebinthacese, Kosacea3, Hamamelidaceae, Balsaniinorae, Haloragaceae, Gunneraceae, Callitrichaceoe, Rhizophoraceae, Combretaceae, Lythraceae, Onagraceae, Samydaceae, Loasaceae, Daliscaceae, Ficoideae, Tetragoniaceae, Cornaceae, and Garryaceae. Plants with connate petals occur in the following usually polypetalous orders : Anonaceae, Pittosporaceae, Polygalaceaa, Portulacaceae, Tamaris- caceae, Termstroemiaceae, Dipterocarpaceae, Humiriaceae, Diosmeae, Bal- saminaceae, Meliaceas, Stackhousiaceae, Droseraceae, Bruniaceae, Napo- leoneae, Melastomaceae, Turneraceae, Cucurbitaceae, Cactaceae, etc. Series I. THALAMIFLOE^E. Calyx, corolla, and stamens usually free and springing directly from the thalamus, or from the outside of an hypogynous disk. Exceptions. The following are noted by Hooker. Connate sepals occur in a few orders. The calyx is adnate to the ovary, or to a fleshy thalamus in Pceonia (Ranunculaceae), Calycanthaceee, some Anonaceas, Nymphae- aceae, Portulacaceae, Capparidaceae, Bixaceae, Polygalaceae, Ternstroe- nriaceae, Vochysiaceae, Tiliaceaa, and Dipterocarpaceae. The stamens are perigynous in some Dilleniaceae, Papaveraceae, Capparidaceae, Morin- gaceae, Resedaceae, Violaceae, Caryophyllaceae, Portulacaceae, Malvaceae, and Sterculiacese. ORDER RANUN CUL ACE^. THE CROWFOOT ORDER. Cohort. Ranales, Sentli. et Hook. Diagnosis. Herbs, or climbing shrubs, with a colourless acrid juice ; leaves alternate, rarely opposite, simple or deeply divided ; leaf- stalks often sheathing at the base ; flowers regular or irregular, Fig. 340. Fig. 341. 'Fig. 339. Fig. 339. Achene of Ranunculus, cut vertically to show the seed, with an embryo at the base of perisperm. Fig. 340. Flower of Aconite, side view, showing the irregular petaloid calyx. Fig. 341. The same, with the sepals removed, showing the singularly iormed petals and the numerous hypogynous stamens. polypetalous or occasionally apetalous, with the calyx petaloid ; the sepals, petals, and numerous stamens all distinct and hypogynous; 196 SYSTEMATIC BOTANY. carpels many or few (rarely solitary), all distinct; seed peri- spermic ; embryo small. Character. Thalamus convex or flat, often elongated, very rarely concave. Calyx green or petaloid, regular or irregular (tig. 340) ; sepals 3-6, hypogynous, deciduous, occasionally persistent, usually im- bricated in aestivation, sometimes valvate or induplicate. Corolla : petals 13-15, distinct, hypogynous, in one or more rows, some- times deformed (fig. 341) or wanting. Stamens indefinite, or very rarely definite, hypogynous ; anthers adnate, bursting longi- tudinally. Ovaries several or few, simple, 1-celled, distinct, or very rarely coherent below to form a compound many-celled ovary ; styles simple ; cells 1- or many-seeded ; placentas at the ventral sutures ; ovules anatropous. Fruit : a collection of dry achenes, a 1- or few-seeded berry, or a circle of follicles more or less coherent below, bursting at the ventral suture ; seeds soli- tary, erect or pendulous, or rarely horizontal in two rows ; embryo straight, minute, in the base or within the apex of horny perisperm (fig. 339). ILLUSTRATIVE GENERA. Tribe 1. CLEMATIDF^E. Mostly climbing plants with opposite leaves. Calyx valvate or i >i duplicate ; fruit of achenes, usually surmounted by the persistent and plumose style. Clematis, L. Tribe 2. ANEMONES. Calyx usu- ally coloured, imbricated; achenes sometimes tailed ; seed inverted. Thalictrum, Tournef. Anemone, Holler. Adonis, DC. Tribe 3. RANUNCULEJE. Calyx imbricated ; achenes not tailed ; seed erect. Ranunculus, L. Tribe 4. HELLEBORES. Calyx imbricated ; petals irregular or none ; fruit of many-seeded follicles, more or less coherent, rarely baccate. Caltha, L. Helleborus, Adam. Tsigella, Tournef. Aquilegia, Tournef. Delphinium, Tournef. Aconitum, Tournef. Act ae a, L. Tribe 5. PSONIE^:. Calyx im- bricated ; petals Jlat or none ; carpels forming dehiscent pods, surrounded at the base by a disk. Pseonia, Tournef. Affinities and Morphological Structure. The typical floral formula isS5P 5 fX; AGO oj G oo , the >), the radicle similarly folded, but the incumbent cotyledons longitudinally folded (induplicate) so as partly to surround it; 4. Spirolobece (o||||), the cotyledons linear, incumbent, and folded or rolled over on themselves and against the radicle; 5. Diplocolobece (o|| || ||), the cotyledons linear incumbent, and twice or thrice transversely folded. Some writers have established Suborders on the characters of the fruit, using those of the embryo for subdivision, thus : 1. Sili- quosce, with a silique opening by valves ; 2. Siliculoscn latiseptce, with a silicule opening by valves, the replum in the broader diame- ter ; 3. Siliculosce angustiseptce, a valved silicule with the replum in the narrower diameter ; 4. Nucumentacece, with an indehiscent silicule, often 1-celled without a replum ; 5. Septulatce, with the valves bearing transverse septa in the inside : 6. Lomentacece, with a pod breaking across into 1-seeded pieces, sometimes with a 1-2-, seeded beak above the abortive true pod. Bentham and Hooker's arrangement closely corresponds with this : but the Suborders are all more or less artificial. THALAMIFLOE.E. 211 ILLUSTRATIVE GENERA : Cheiranthus, R. Br. ; Arabis, L. ; Alyssum, L. ; JErophila, DC. ; Cochleariq, L. ; Iberis, L. ; Cakile, Tournef. ; Ery- simum, L. ; Capsella, Vent. ; Lepidium, R. Br. ; Brassica, L. ; Crambe, Tournef. ; Raphanus, Tournef. ; Subularia, Adans. ; Sehtzopetafon, Hook. Affinities, &c. The relationships of this Order to Papaveracese and Fu- mariaceae, and thence with the apocarpous Orders standing near, have been dwelt on already. With the Capparidacese the agreement is still closer, in the general character of the flower and in the seeds ; but when that Order has so few as six stamens they are not tetradynamous an almost universal condition in Cruciterae. The true nature of the plan of the anomalous flower of this Order is a subject of considerable con- troversy. The numerical arrangement isS2+2P4A2 +4 G 2, disposed thus: S.. + ; P ; : A., -f- ; : G.. . The two lateral sepals are attached higher up than the other two, the four petals are in a single whorl. Lindley and many others regard the six stamens as belonging to two circles of four, the outer of which has always two stamens abortive, while the inner pairs should normalty stand singly before the four petals. If the glands in the receptacle are to be regarded as abortive stamens, which is plausible, this structure really does exist in JErysimum Perojfskianiim, where the two glands stand opposite two sepals and form a circle with the two short stamens ; but there appears to be as many as six glands in some Crucifers, which involves the existence of three staminal circles : as a polyandrous form (Megacarpcea polyandra) has been met with, we may even admit this. De Candolle, Moquin-Tandon, and Webb regarded the stamens as normally four, the pairs being formed by chorisis. As to the ovary, it is explained as being composed of two carpels with a spurious dissepiment: the stigmas opposite the placentas, like those of Papaver, being double and composed of a half from each carpel, just as the placentas are. The fact that four carpels are sometimes found in monstrosities, and are constant in the genus Tetracellion, merely indi- cates a return to a symmetrical condition, ordinarily interfered with by suppression of two carpels. The most recent views as to the structure of the flower are those of Eichler, who affirms the existence of chorisis in the long stamens. His notion is that the flowers of Crucifers consist of two antero-posterior sepals, two lateral ones, four petals crossing the lateral sepals diagonally, two lateral short stamens, two antero-posterior long stamens split into two, and two lateral carpels ; S 2+2 P 4 A 2-f- 2 G 2. These views are adopted after an examination of the development of the flower, in which there are first to be seen two tubercles for the fore and aft sepals, then two for the lateral sepals ; the four petals originate simul- taneously ; the two short stamens arise opposite the lateral sepals, the two other staminal tubercles are subsequently developed at a higher level than the preceding and decussate with them j these two after a time be- come notched, the notch gradually deepens and ultimately forms two distinct stamens. The position of the carpels is sometimes antero- posterior (;) sometimes literal ( ..). The glands of the disk also vary in number and position, and may, as suggested by Mr. Worthington Smith, be the representatives of abortive stamens or pistils, which would, if fully developed, render the flower symmetrical and isomerous. Van Tieghem considers the gynaecium to consist of four carpels, two of which are ovuliferous and terminate in stigmas, while the other two are sterile. P 2 212 SYSTEMATIC BOTANY. Rev. G. Henslow suggests that the original type was not binary or quaternary as generally considered, but quinary, the fifth member of each quincuncially arranged whorl being suppressed. As a rule Crucifers have in the adult condition bractless flowers ; a few species have bracts normally ; and they sometimes occur as abnormalities, and are then placed at the base of the peduncles, or emerge from the side of them, owing to imperfect detachment of bract and pedicel, and consequent uplifting or displacement in course of growth. Subularia has perigynous stamens springing from a cup-shaped receptacle. The fruits of Morisia and Geo- coccus ripen under ground. The long stamens of Atelanthera have 1-celled anthers. In Streptanthus, and some species of Ve.Ua, the long stamens are connate in pairs. Distribution. This large Order is very natural, and, as usually hap- pens in such cases, the genera are very difficult to deh'ne. The species are most abundant in temperate and cold climates, and seldom found otherwise than on mountains in the tropics. Qualities and Uses. The general character is antiscorbutic, the watery juice being often pungent and occasionally acrid. The seeds yield oil, which is contained in their cotyledons. By cultivation the acrid juices become milder, and the structures are easily made very succulent, from abnormal development of parenchyma. Under these conditions they become valuable esculents, either in their roots, as the Turnip (Brassica Jtapa), their stem and leaf-stalks, as Sea-kale (Crambe maritima), their stem, leaves, or undeveloped inflorescence, as Kohl-rabi, Cabbages, Greens, Kales, &c. in all their varieties, and Cauliflower and Broccoli, all apparently derived from Brassica oleracea by cultivation. Brassica Napus, Rape or Colza, is most valuable on account of the oil in its seeds, and its oil-cake as food for cattle. The Swede Turnip is supposed to be a hybrid between B. campestris and B. Rapa or Napus. Radishes (JRa- phanus sativus), Horse-radish (Armoracia rusticana), are cultivated on account of their pungency, as are also the herb and, still more, the seeds of the Mustards, Sinapis alba . and nigra, the latter of which yields the proper table-mustard seed. Water-cress (Nasturtium officinale) and Gar- den-cress (Lepidium sativuni) are pungent salad-plants. Isatis tinctoria and a Chinese species, /. indigotica, yield a blue dye from their silicles. Many of the Cruciferae are remarkable for containing sulphur compounds, both in the seeds and in the herbage, whence the disagreeable smell of water in which they have been boiled, or even of the bruised fresh plant of some, as En/simum Alliaria. Oil of Mustard, obtained by macerating the seeds of Black Mustard in water and distilling, is violently acrid. Many of the genera cited in the list above are represented by common wild plants in this country, the rest are found in most gardens ; Matthiola is the Stock, Cheiranthus Cheiri the Wallflower, &c. CAPPARIDACE^E are herbs, shrubs, or rarely trees, with alternate simple or lobed exstipulate leaves ; cruciform flowers ; stamens numerous, or, if 6, not tetradynamous, on a disk, or with an internode separating them from the corolla, and a 1-celled pod or berry with 2 or more parietal placentas ; seeds reniform. aperispermic. Illustrative Genera : Tribe 1. CLEOMEJE. Fruit capsular : Cleome, DC. ; Polanisia, Raf. Tribe 2. CAPPARE^B. Fruit baccate : Cadaba, Forsk. ; Cajjparis, L. THALAMIFLOE^l. 213 Affinities, &c. This Order is closely related to the Cruciferse, both in structure and properties, being distinguished chiefly by the stamens, which are mostly indefinite, or which, when only six in number, are very rarely tetradynamous, and by the stipitate ovary. The parietal placentas and the disk ally them to the Resedacese, which likewise have kidney- shaped aperispermic seeds ; there is a more distant affinity to the Bixacese, which have perispermic seeds. The development of the internodes between the circles of floral organs is a striking character in various Cappari- daceae : in Cleome and Capparis the thalamus has rather a discoid deve- lopment below the stamens, the ovary being stalked ; in Gynandropsis and Cadaba there is a stalk-like prolongation of the thalamus between the corolla and stamens and between the stamens and the ovary. This struc- ture connects the plants in some degree with Passifloraceae. In some species of Mcerua, moreover, there is a " corona " like that of Passion- flowers. In other genera the receptacle is developed into a more or less fleshy or glandular disk. In Physostemon the stamens are curious, the two or four posterior ones having the filaments inflated or swollen below the anthers. Eichler describes the development of the andrcecium as show- ing that there are two whorls of stamens, each primarily consisting of two, first two lateral, then two antero-posterior tubercles, which subse- quently subdivide into numerous filaments. Distribution. The species are somewhat numerous in the tropical subtropical regions of the world, especially in Africa. Qualities and Uses. There is great agreement with the Cruciferae ; but in some cases the pungent principles are dangerous. The Capers used as pickles are the flower-buds of various species of Capparis (C. spinosa, Fontanesi, rupestris, and ceyyptiaca). The root of Crateeva yynandra, the Garlic Pear, is said to be very acrid and to blister like Cantharides. C. excelsa is a large tree in Madagascar. The Polanisia icosandra of the United States is used as a vermifuge j and the root of Cadaba indica is said to be aperient and anthelmintic. Many species have been introduced into our gardens : a few bear the open air in sheltered places. RESEDACE^E are herbs or undershrubs with unsymmetrical 4-8- merous small flowers, commonly with a fleshy one-sided hypogynous disk between the petals and the (3-40) stamens, which it supports. Pistil poly- carpellary and 1-celled, or of several more or less distinct carpels. Pod 3- or _6-lobed, 3- or 6-horned, 1-celled with 3 or 6 parietal placentas, sometimes opening at the top before the aperispermic reniform seeds are ripe. Embryo curved. Illustrative Genera : Reseda, Oliyomeris. Affinities, &c. These plants agree in many respects with the Cappari- dacese, as in the presence of a disk supporting the stamens and the reni- form seeds. By Miiller they are placed between Capparids and Crucifers. There is a more distant relation to the Papaveraceae, from which, however, they are always distinguished by their aperispermic seeds. Moringaceae have many points in common, but differ in habit, foliage, straight embryo, and monadelphous stamens. The one-sided disk is an outgrowth from the thalamus. The petals of the Mignonette have a broad claw and a deeply divided or fringed limb. The pollen-grains are ellipsoid. The opening of the ovary before the seeds are ripe is worthy of note as an uncommon phenomenon ; it is well seen in the Garden Mignonette (Reseda odorata}. 214 SYSTEMATIC BOTANY. Olic/omcris is remarkable for the reduction of the parts of the flower, having but 2 petals and 3 stamens, and the disk is likewise absent. Astrocarpus has separate carpels. A small order. Most of the kinds are European ; but a few occur in India, South Africa, and in California. The best known plant of the Order is Reseda odorata, so much Tallied for its perfume and hardy character. Reseda luteola, a native weed, com- monly called Weld, yields a yellow dye. Some of the species are acrid. BIX ACE M are shrubs or small trees with alternate, usually exsti- pulate, entire, leathery, often dotted leaves ; regular hermaphrodite or unisexual flowers ; sepals 2-7, slightly coherent below, imbricate ; petals as many and distinct, or absent, sometimes very numerous; stamens hypogynous, generally indefinite; ovary sessile, or slightly stalked, 1- or rarely more-celled, with two or more parietal placentas; ovules curved; seeds numerous, with a straight or slightly curved embryo in the axis of fleshy perisperm ; cotyledons broad ; radicle next the hilum. Illustra- tive Genera: Bixa, L. j Oncoba, Forsk. ; Flacourtia, Commers.j.E'n/^Arosper- mum. Lam. Affinities, &c. Related to the Samydaceee, but distinguished by their hypogynous stamens, and to the Passifloraceae, but destitute of a coronet. From Capparids they differ in their perispermic seeds ; from Cistacese in their straight embryo. Benthain and Hooker refer the small group Pangiacese here, while Baillon includes Papayacese, Lacistemaceae, and Turneracese. The species are not very numerous, and are mostly natives of the hottest regions of the globe; some of the plants are bitter and astrin- gent; the pulpy fruits of Oncoba, of Flacourtia Ramontchia, sapida, and sepiaria are edible. Bixa Orellana yields the substance called Annatto, used for colouring cheeses and as a dye j it is derived from a pulp sur- rounding the seeds. CISTACESE are low shrubs or herbs with regular hermaphrodite flowers, persistent imbricate calyx, caducous crumpled petals, distinct hypogynous, mostly indefinite stamens ; pod 1-celled, 3-o-valved, with as many parietal placentas ; ovules straight ; seeds perispermic : embryo curved or spiral, with the radicle remote from the hilum. Illustrative Genera : Cistus, Helianthemum. Affinities, &c. Nearly related to Violaceae, Bixaceae, and Droseraceae, but distinguished by the form and direction of the embryo ; from the Hypericaceae by the structure of the fruit and the absence of dots on the leaves, and from Linacese by the fruit ; they also approach Papaveraceaa by Dendromecon : and Lindley considers that there is some connexion with Capparidaceae and Cruciferae ; but the 4-merous plan and aperisper- mic seeds of these Orders remove them widely. Some of the Heliantliema have dimorphic flowers. The pollen is ellipsoid. Lechea has stamens fewer than the petals. The Cistaceae are most abundant in South Europe and North Africa, but occur in other parts of the globe. The gum-resin called Ladanum is obtained from Cistus creticus, ladaniferus, Ledon, and others ; and the plants generally are regarded as resinous and balsamic. Many species are cultivated for their beautiful but fugacious flowers. Helianthemmn rulyare, a native plant, is remarkable for the irritability of the stamens in the newly opened flowers. THALAMIFLOR/E. 215 DROSERACE/E are bog-herbs, mostly glandular-haired, with regular hermaphrodite 5-merous flowers and marcescent calyx and corolla ; sta- mens as many as the petals, or indefinite, hypogynous or perigynous ; the anthers fixed by the middle, extrorse j ovary free, 1-celled; ovules numerous, inverted ; styles as many as the placentas or connate ; pod 1-celled, placentas parietal or basilar ; the embryo minute, at the base of fleshy perisperm. Illustrative Genera : Drosera, L. ; Aldrovanda, Monti ; DioiKEct, Ellis. Affinities, &c. The interesting but not very numerous plants of this Order are remarkable for the circinate curvature of their flower-stalk?, which, together with the absence of stipules, the extrorse anthers, divided styles, &c., separates them from the Violacese, which they approach ; they are connected with Hypericacese by Parnassia, and have some affinity to Oistaceae and Turneraceae. Bentham and Hooker place them near the Saxifrages. These plants are found in bogs or marshes in most parts of the globe, excepting the Arctic regions. Their most interesting charac- ters reside in the leaves, which in Drosera (Sun-dews) are covered with beautiful glandular hairs, which have a spiral vessel running up their stalks and secrete a digestive fluid. They are also endowed with the power of motion when touched, so that an insect alighting on the leaf is unable to make its escape owing to the viscid fluid exuded from the glands. The hairs then bend over the insect, which becomes dissolved by the acid fluid, and ultimately absorbed. Aldrovanda vesiculosa, a native of South Europe, has curious whorled, cellular, spoon-shaped leaves. Dioncea muci- pula, the Veuus's Fly-trap of the North-American bogs (occasionally cultivated in stoves here), is well known for the remarkable irritability and digestive properties of the lamina of the leaf, the two lobes of which close upon any object touching the upper face. The Droseracese are said to be acrid. VIOLACE^E. THE VIOLET OEDEB. Coh. Parietales, Benth. et Hook. Diagnosis. Herbs or shrubs : leaves alternate, usually stipulate ; flowers regular or irregular, hermaphrodite, with a somewhat irregular, generally 1-spurred corolla of 5 petals : stamens 5, hypogynous, with adnate introrse anthers connivent over the pistil, connective of the anther usually prolonged ; style and stigma single ; pod 1-celled ; 3-valved, with 3 parietal placentas in the middle of the valves ; seeds perispermic ; embryo straight. Character. Thalamus flat or slightly rounded. Calyx : sepals 5, persis- tent, usually elongated at the back, imbricated in aestiva- tion. Corolla: petals 5, hypogynous, equal or unequal, one usually spurred, withering-persistent ; obliquely convolute in aestivation. Stamens 5, alternate with the petals, or occasionally opposite, inserted on an hypogynous disk, often unequal; anthers 2-celled, introrse, separate or cohering, and 216 SYSTEMATIC BOTANY. lying upon the pistil ; the filament or connective prolonged be- yond the lobes of the anthers, in the irregular flowers two of the filaments are spurred at the base. Ovary compound, 1-celled, Fig. 353. A. Flower of Violet. B. Section of same. C. Andrcecium. D. Plan of flower, with bract and two bractlets, &c. E. Capsule open, to show parietal placenta tion. F Seed with aril, much enlarged. Gr. Seed with straight embryo in perisperm. with numerous ovules on 3 parietal placentas opposite the 3 outer- most sepals, or rarely 1-ovuled ; ovules anatropous ; style single, mostly declinate ; stigma capitate, oblique, hooded. Fruit : a capsule bursting into three valves, with the placentas up the middle ; seeds mostly numerous, often arillate ; embryo straight in the axis of fleshy perisperm. Illustrative Genera : Viola, L. ; Papayrola, Aubl. ; Alsodeia, Thouars. Affinities, &c. The typical formula is S5 P5 A 5 G tt. By the irregula r flowers and appendaged anthers we readily distinguish most of the Violaceae from the Droseraceae, Cistacese, and Sauvagesiaceae ; and in Alsodeia and other genera, where the calyx and corolla are regular, the simple style and capitate stigma are still available ; and several other important differences exist, such as : the definite num- ber of stamens and straight embryo, unlike that of the Cistaceaa ; different vernation and stipulate condition of the leaves, unlike Dro- seracese ; while Sauvagesiacese, besides having the anthers unappen- daged, have either numerous stamens, or, if five, they are opposite to the THALAMIFLOK^!. 217 petals and alternate with five scales ; moreover the capsule bursts septici- dally, so that the placentas are at the edges of the valves. Violacese are related more distantly to Passifloraceae. In the native species of the genus Viola, it is not uncommon so find apetalous flowers, especially in the autumn. The pollen-grains are ellipsoid or prismatic. Distribution. An Order consisting of a few genera, some, such as Viola and Alsodeia, rich in species, the greater number with but few. The irregular Violaceae belong chiefly to Europe, North Asia, and North America, where they are generally small herbs, and to South America, where they are mostly shrubby ; the regular genera, Alsodeia &c., belong to South America, Africa, and Malacca. Qualities and Uses. The Order is characterized in general by emetic properties, which are especially developed in the South- American lonidia ; /. parviflorum, I. Poaya, I. Ituba, are used there instead of Ipecacuanha, and the last was formerly supposed to be the true Ipecacuanha-plant. Viola canma, the common Dog-violet of our hedges, is said to be bene- ficial in skin diseases ; and the same properties are attributed to Anchietia salutaris in Brazil, where it is also used as a purgative. The roots of the Sweet Violet, V. odorata, are emetic and purgative ; its seeds are also purgative. V. tricolor is the Pansy or Heart's-ease ; its leaves have been supposed to contain hydrocyanic acid, since they smell like peach-blossom when bruised. The SAUVAGESIACEJE form a small group sometimes separated from Violaceae on account of the characters mentioned above. They are related to the Hypericacese through Parnassia. FRANKENIACE^E constitute a small and unimportant Order bearing very close affinity to the tribe Silenese of the Order Caryophyllaceae in the floral envelopes and stamens ; but the placentas are parietal, and the embryo is straight, which causes them to approach Violaceee, and espe- cially Sauvagesiaceae, from which, however, they differ in their united sepals and extrorse anthers. Most of the plants are found in South Europe and North Africa ; but a few species are scattered in other parts of the world. They are said to be mucilaginous and aromatic. Illustra- tive Genus : Frankenia, L. TAMARIOACE^E are shrubs or herbs of fastigiate growth, with alternate scale-like leaves, usually pitted ; flowers in close spikes or racemes ; calyx 4-5-parted, persistent ; petals distinct, springing from an hypogynous disk, equalling the petals or twice as many, distinct or co- herent ; ovary superior, ovules numerous, ascending ; capsule 3-valved, 1-celled, with 3 placentas either at the base or 1 in the middle of each valve ; seeds comose or winged, without perisperm ; embryo straight ; radicle inferior. Illustrative Genus : Tamarix, L. Affinities, &c. Endlicher looked upon this Order as intermediate between Hypericaceee (through Reaumuriaceae) and Lythracese, while Lindley thought it stood rather between Violaceae and Orassulaceae, antl De Candolle placed it near Portulacacea3, as also do Bentham and Hooker, who include in it Reaumuriece and Fouqueria. Frorn^all the above, how- ever, it differs in the nature of the seeds. 218 SYSTEMATIC BOTANY. Distribution. A group consisting of two genera, one with several, the other with very few species. The plants are natives of the northern hemisphere of the Old World, growing chiefly by the sea-shore, or on the margins of rivers or lakes. Qualities and Uses. The bark is bitter and astringent; and those kinds growing near the sea yield abundance of soda when burnt. Tamarix mannifera yields the Manna of Mount Sinai, a kind of mucilaginous sugar, said to be exuded in consequence of the attacks of a Coccus-insect. Several species are attacked by gall-insects ; and the galls of T. indica, dioica, Furas, and orientalis are used in medicine and for dyeing. Tamarix gallica flourishes well near the sea on our coasts, and is an ornamental shrub. Myricaria germanica is a handsome shrub in our gardens. CAEYOPHYLLACE^E. THE PETC ORDER. Coli. Caryophyllinae, Benth. et Hook. Diagnosis. Herbs with opposite entire leaves ; stems swollen at the joints ; flowers symmetrical, 4-5-merous, with or without petals ; stamens distinct, not more than twice as many as the sepals, hypogynous or perigynous ; styles 2-5 ; seeds attached to the base or to the central placenta of the 1 -celled (rarely 3-5-celled) cap- sule; embryo curved round the mealy perisperni.' Character. Calyx : sepals 4 or 5, persistent, distinct or co- Thalamus flat. herent into a tube. Corolla : petals 4 or 5, clawed, often deeply Fig. 356. Fig. 354. Fig. 357. Fig. 854. Capful ft of Cerastium, burst. Fig. 355. Section of seed of Lychnis: a, endosperm; b, embryo. Fig. 356. Dichasial cyme of Cerastium. Fig. 357. Section of a flower of Silene, with an iuternode between the calyx and corolla. THALAMIFLOB^E. 219 bifid, sometimes wanting, mostly separated by a short internocle from the calyx. Stamens twice as many as the petals, or equal to and opposite to the sepals, sometimes fewer, inserted with the petals ; filaments awl-shaped, sometimes coherent; anthers innate. Ovary sessile, or raised with the corolla and stamens on a short stalk above the calyx, 1-celled, with a central placenta or with 2-5 dissepiments extending to the centre ; ovules few or nume- rous ; stiymas 2-5, filiform, resembling the styles, but papillose down the inner side. Fruit capsular, 1-celled, with a central placenta, 2-5-valved, or splitting into 4-10 teeth above (fig. 354), or 2-5-celled, loculicidally dehiscent, with the placentas adhering to the septa ; seeds mostly indefinite ; the embryo mostly curved round the perisperm (fig. 355), rarely straight or spiral, with little perisperm ; radicle next the hilum. ILLUSTRATIVE GENERA. Tribe 1. ALSINE^E. Sepals distinct. Sagina, L. ALsine, Wahlenb. Arenaria, L. Stellaria, L. Cerastium, L. Tribe 2. SILENRX. Sepals cohering into a tube. Dianthus, L. Saponaria, L. Silene, L. Lychnis, L. Affinities, &c. The typical floral formula is S 5 P 5 A 5-f 5 G 5. The op- posite entire leaves springing from thickened nodes, definite stamens, and the character of the placenta and seeds serve to distinguish the great ma- jority of tin's well-marked Order. The nearest relations of the Caryo- phyllaceoa, as here defined, are unquestionably the Illecebraceae and Por- tulacacese, which we separate more for the sake of convenience of distinc- tion than on account of natural diversity, since in both those Orders there is a variation between the hypogynous and perigynous conditions. The Illecebraceae may be distinguished by their scarious stipules and utricular fruit, and the Portulacacese by the 2-leaved calyx and by the stamens when equal to the sepals being alternate, or opposite to the petals, since it seems more convenient to keep the Mollugineee with Portulaeacese if they are divided. The apetalous forms, and the alliance with the Orders just named, connect this Order with the Amarantaceae and Chenopodiaceas and several other families, all characterized by a curved embryo surround- ing a floury perisperm. The placentation of the Caryophyllaceae is regarded by some authors as forming one of the exceptions to the marginal type, the free central column in mature ovaries being regarded as a product of the receptacle, independent of the carpels. But the dissepiments exist in the early stages of development, and are torn away during the expansion of the ovary : hence there is no necessity to assume the independent origin of the pla- centas. Monstrous blossoms of plants of this Order do not decide the question, since these have been found with really independent growth of the ovules from the base of the ovary, and with ovules developed upon the margins of the carpels. Lychnis and some other genera have petals with a scale-like outgrowth. Several species are dioecious. 220 SYSTEMATIC BOTANY. Distribution. An Order consisting of several genera and a large number of species, for the most part natives of temperate and cold climates, extend- ing to the Arctic regions and to almost the extreme limit attained by flowering plants on mountains. Qualities and Uses. The plants of this Order are generally devoid of active properties some of them containing more or less of a deleterious principle, called saponine^ as Saponaria, Af/rostemma, Silene, &c. ; and Gypsophila Struthium, the Egyptian Soap-root, derives its name from its saponaceous properties ; this substance is generally most abundant in the roots. The genus Dianthus, or Pink, is remarkable for the beauty of its flowers ; D. barbatus is the Sweet William ; J}. plumarius is the parent of the varieties of Garden Pink ; D. Caryophyllus (the Clove-Pink) of the Carnation and its varieties. Lychnis and Silene also aftbrd handsome garden plants. A large proportion of the Plants of this Order are insig- nificant weeds. MALVACEAE. THE MALLOW ORDER. CoJi. Malvales, Benth. et Hook. Diciynosis. Herbs or shrubs with alternate stipulate leaves often covered with soft down and regular flowers ; calyx valvate, and Fig. 358. Fig. 358 a, flower of Mallow, longitudinal section; b, andrcecium; c, calyx and fruit; ings) lateral, usually petaloid. Corolla : petals usually 3, 1 anterior and large (keel) and 2 posterior, between the wings and posterior sepal of the calyx, and of ten coherent with the keel ; sometimes 5, the additional 2 small, and placed between the wings and the anterior sepals on each side ; the keel entire and with a fringe or crest, or 3-lobed and without a crest. Stamens hypogynous, 8, coherent in a tube, unequal and ascending ; the tube split opposite the back sepal ; or 4, distinct ; anthers clavate, 1-celled, and opening by a terminal pore, or 2-celled. Ovary compound, 2-3-celled, one cell always suppressed in some cases ; ovules suspended, solitary or twin ; style and stigma simple, some- times hooded. Fruit various, dry or succulent, sometimes winged ; seeds pendulous, naked or with a hairy coat, a caruncle next the hilum ; embryo straight or nearly so, in abundant perisperm. Illustrative Genera: Sdlomonia, Lour. ; Polygala, L. ; Mundtia, Kunth ; Monnina, Huiz & Pav. ; Securidaca, L. ; Xanthophyllum, Hoxb. ; Krameria, Lceffl. (?). Affinities, &c. The relations of the Polygalaceee have been a subject of much discussion among botanists. The irregular calyx and corolla, some- what papilionaceous in Polygala, has led to a comparison to Leguminosae, from which, however, they differ widely; moreover the odd petal is anterior in Polygalads, not next the axis as in Leguminosse. The irregu- lar petals, together with the hooded stigma, have suggested a relationship to Violaceae ; Brown pointed out their relation to Tremandracese, of which they may be considered irregular forms ; Krameria lias been re- ferred by some writers to the Qsesalpineous division of the Leguminosge. Most authors, however, are agreed that the nearest affinity is to Sapinda- ceae. Krameria is raised to the rank of a distinct Order by a few writers, on account of the different corolla, composed of 5 petals', 4 (often free) stamens, and 1-celled ovary. Moutabea has sepals, petals, and stamens connate into a tube. Xanthophyllum has free stamens, 2-celled anthers, and a 1-celled fruit. Perisperm is sometimes wanting. The pollen in Polygala is elliptical, with numerous bands. Distribution. A large Order, nearly half the species of which are comprised in the genus Poli/f/nla and are very generally distributed ; the others are mostly confined to particular quarters of the globe. Qualities and Uses. The plants of this Order are mostly bitter, and aciid or astringent, with a milky juice in the root. The common Milk- wort, P. vulgaris, and especially' the form called P. amara, possesses bitter properties, but in less degree than P. rubella of North America. THALAMIFLOB^E. 233 Soulamea amara (Molucca) is said to be intensely bitter. The more active species of Polygala have emetic, purgative, and diuretic properties: P. Senega, the American Snake-root, with P. sanguined and purpiirea, the Cape P. Serpentaria, the European P. chameebuxus, and the P. crotala- rioides of the Himalayas &c., all show this property ; and they are like- wise all reputed antidotes ag-ainst the poison of snakes. P. venenosa (Java) is regarded as a poison, the properties being excessively concentrated. P. tinctoria (North America) is used in dyeing. The bark of the root of a species of Mundtia contains a saponaceous substance, and is used for washing. Krameria triandra and other species, called Rhatany, are remarkable for the powerful astringent quality of the roots, which gives a deep red colour to an infusion, lihatany-root is used in medicine, and is employed also to adulterate Port wine. TREMANDRACE^E are a small Order of plants related to Polygalaceae, but with a regular, symmetrical flower, valvate calyx, free stamens, and seeds hooked at the chalazal end. They may be regarded as regular- flowered Polygalas. De Candolle placed them between Polygalaceae and Pittosporacese. They are slight, heathy shrubs, growing in Australia : 16 species are known, belonging to the genera Tremandra, Tetratheca, and Platytheca. They derive their name from the porous dehiscence of the anthers, and are of no known use. MALPIGKEIACE^. Series Disciflorae ; Cohort Geraniales, Benth. et Hook. Diagnosis. Trees or shrubs, often climbers, with usually opposite or whorled, rarely alternate leaves ; stipules generally short and deciduous, occasionally large and opposite the leaves ; flowers perfect, or polygamous ; calyx and corolla o-merous, calyx with glands at the base of 1 or of all the segments ; petals clawed ; stamens mostly 10, often mouadelphous with a thickened produced connective ; caipels 3, or very rarely 2 or 4, wholly or partly coherent, often keeled ; ovules solitary in the cells, pendulous from long funiculi ; seeds aperispermic ; embryo with mostly convolute thick or leafy cotyledons. Illustrative Genera : Malpighia, Plum, j Hircea j Gaudlchaudia ; Banisteria, L. Affinities, &c. The closest relations of this Order are Sapindacese and Aceraceas, from which they are distinguished by their symmetrical flowers, and generally by the glands in the calyx, the long stalks to the petals, the small disk, and solitary ovule. Many of the species have dimorphic flowers. Some of the climbing kinds have stems of anomalous structure with several woody axes, without annual rings, enclosed in a common bark, or ultimately* more or less separated from one another. Nitraria, a genus of saline plants, is sometimes separated as a distinct Order. Two or more embryos in the same seed occur in some species. The Order is a large one, comprising many genera and species, which latter are mostly Tropical-American. Their properties are generally unimportant ; many of them have been introduced into our stoves on account of their showy flowers. The fruits of Malpighia r/labra and punicifolia are eaten in the West Indies, under the name of Barbadoes Cherries. Munby supposes the 234 SYSTEMATIC BOTANY. sedative or semi-intoxicating drupe of Nitraria tridentata (North Africa) to have been the Lotus of the ancients. The bark of most kinds is as- tringent ; the hairs of some Malpighias sting powerfully. ERYTHROXYLACEJE are by some authors separated from the Malpighi- aceae on account of the calyx having no glands, while the petals present two membranous plates, on account of their capitate stigmas, and the absence of a long funiculus to the anatropous ovule. They are closely allied to Linacece, with which, indeed, they are associated by Bentham and Hooker, but differ in the presence of scales to the petals, their drupaceous fruit, and woody stem. They are shrubs, mostly (belonging to one genus, Ery- throxylon, and found most abundantly in Brazil ; but a few are scattered all over the globe. They receive their name from the red colour of the wood of some kinds, such as Erytliroxylon hypericifolium (Mauritius). The most remarkable plant of the Order is E. Coca, the leaves of which, under the name of Coca or Ipadu, are largely consumed in Peru and in Equatorial America, to produce a kind of intoxication ; " Coca " is said to enable the natives to go two or three days without food ; it is mixed with powdered chalk and chewed. Its properties are due to a principle like Iheine, which arrests the sense of fatigue and hunger. Several species of Erytliroxylon are recorded, and two or three belonging to other Genera. MELIACELE. Series Disciflorse ; Coh. Geraniales, ficnth. et Hook. Diagnosis. Trees or shrubs with alternate or somewhat opposite, simple or pinnate leaves, without stipules : flowers sometimes diclinous by abortion ; calyx and corolla S-, 4-, or o-merous ; stamens twice as many, coherent in a long tube or free ; anthers sessile in the orifice of the tube ; hypogynous disk sometimes cup-like ; ovary free, compound, few- or many-celled ; style 1 ; ovules 1-12, rarely 4 in a cell ; fruit succulent or capsular, often 1 -celled by abortion ; seeds not winged ; perisperm fleshy or absent. Illustrative Genera : Melia, L. ; Trichilia, L. ; Stvietenia, L. j Cedrela, L. Affinities, &c. Nearly related to Eutnceae. It differs in the leaves, which are generally not dotted, and in the staminal tube ; from Sapinda- cesB in the ascending ovules, with ventral raphe. The species are nume- rous, and are found in the hotter parts of the globe generally j they possess bitter and astringent properties: some are powerfully purgative and emetic, such as Guarea Aubletii and trichilioides, Trichilia emetica, &c. Melia Azedarach, the Neem-tree, or Margosa, of the East Indies, is sup- posed to have febrifugal properties ; its succulent pericarp yields an oil; and a kind of toddy is obtained by tapping it. Carapa guineensis yields a purgative oil, which is used also for lamps. Lamium, a genus of the East- Indian archipelago, yields an edible fruit called Langsat or Lanseh and Ayer-Ayer. The Cedreleae are distinguished from other Meliaceee chiefly by the free stamens and the numerous winged seeds. Chloroxylon and Flinder- sia have dotted leaves. The plants are most common' in the tropics of America and India. They have fragrant, aromatic, and tonic properties, and their timber is valuable. Stvietema Mahuyani is the Mahogany- THALAMIFLOR^. 235 tree ; its bark, and that of Cedrela Toona, febrifuya, and other species, are used as substitutes for Cinchona. Chloroxylon Swietenia furnishes East-Indian Satin-wood j and an oil called Wood-oil is obtained from it. Oxleya xanthoxyla is the Yellow- wood of Australia. AUBANTIACE^. THE ORANGE ORDER. Series Discifloras ; Tribe of Kutaceae, Benth. et Hook. Diagnosis. Trees or shrubs with smooth, glandular alternate leaves, the blade jointed to the petiole; flowers regular, hermaphrodite, 3-5- merous ; petals and stamens inserted on an hypogynous disk ; stamens with flat filaments, distinct or coherent into one or several parcels ; ovary many-celled, style single, terminal ; fruit pulpy, often with a glandular leathery rind ; seeds without perisperm ; embryo with thick fleshy cotyle- dons and a short radicle next the hilum. Illustrative Genera : Triphasia, Lour. ; Beryera, Keen, j Cookia, Sonner. ; Feronia, Corr. j JEgle, Corr. ; Citrus, L. Affinities, &c. The plants of this Order are by Bentham and Hooker classed as a tribe of Rutaccce, and are nearly related to the Meliaceae in the structure of the flowers, and still more closely to Amyridacese. In general they are distinguishable by the dotted leaves, with the blade (simple or compound) articulated to the petiole, the deciduous imbricated petals, and the succulent fruit. The relation to Eutaceae is rendered clearer by occasional monstrosities of the fruit, from which some of the carpels grow out like horns. Sometimes a second circle of carpels is produced, forming, as it were, a double concentric fruit, comparable in some measure to the conditions in the Pomegranate, where, however, the whole fruit is en- closed in the excavated receptacle. The pulp of the Orange consists of cellular hairs produced from the wall of the fruit. The seeds of Oranges often contain two embryos; and they are remarkable for the develop- ment of ramified collections of spiral vessels at the chalazal end, within the testa, also for a peculiar coloration of the inner coat of the seed in this situation. Distribution. Chiefly East-Indian plants, but diffused by cultivation throughout the tropics, and even in the warmer temperate regions. Qualities and Uses. The most remarkable parts of these plants are their fruits ; those of the genus Citrus being among the most valuable and best-known of imported fruits. The species of Citrus are not clearly de- fined, much difference of opinion existing as to the specific distinctness of certain forms, which, as in most cultivated plants, are much confused. C. Aurantium is the common Sweet Orange ; C. Biyaradia or C. vulgwify the bitter or Seville Orange, seems to be known only in cultivation, and is supposed by some to be a variety of the preceding. C. Beryamia is the Mellarosa or Bergamot Orange, which is also regarded as a variety ol C. Limetta, the cultivated Sweet Lime ; C. acida is the East-Indian Lime ; , C. Limonwn is the ordinary Lemon ; C. Lwnia is the Sweet Lemon, cul- tivated in the South of Europe; C. medica is the Citron; C. decumana is the Shaddock ; C. Paradisi the Forbidden-fruit ; C. Pompeimos the Pom- pelmoose ; and C. japonica the Kumquat. All these fruits have an abundant pulp, which varies chiefly in the degree of acidity and the 236 SYSTEMATIC BOTANY. peculiar aroma ; that of C. Biyaradia is also bitter. The rind of all is fragrant, from the presence of imbedded glands containing- essential oil of aromatic and bitter character ; the flowers partake of the aromatic quality. The oil of Neroli is obtained from the flower of C. Biyaradia ; but the oil of the rind is also used for making Orange-flower water. Oil of Berga- mot is from the flower and rind of the fruit of C. Beryarnia ; liuile de Ce- drat from C. medica ; the essential oil of the Lemon-rind is also largely used. The rinds are also valued for their bitter and aromatic properties when dried or preserved with sugar. The dry rinds of Orange, Lemon, &c. are used as stomachics in medicine, in infusions and tinctures; and are also employed in the preparation of liqueurs and cordials, such as Curacoa &c. ; the fruit, rind, and pulp, when preserved with sugar, form " marmalade," the best being made from the Seville Orange. The acidity of the Lime and Lemon depends chiefly on the presence of citric acid, and renders them very valuable as antiscorbutic agents. sEyle Marmelos, the Bael-fruit, sometimes used in cases of dysentery, has a delicious fruit, which, however, is laxative ; the rind is used as a vermifuge. Cookia punctata yields the Wampee, highly valued in China and the East-In- dian Archipelago ; and the fruits of other plants of the Order are eaten. The wood of all the trees is hard and compact; the foliage shares the fragrant character of the fruits, containing abundance of glands filled with aromatic, bitter essential oils. The Orange, Lemon, and their varieties are largely cultivated in the South of Europe in the open air ; and in our conservatories they are everywhere prized, on account of their striking appearance when in fruit and the delicious perfume of the flowers. Orange- and Lemon-trees are wonderfully prolific of fruit ; and the plants retain their vitality with great obstinacy when taken from the ground and transported to a distance, and when they are multiplied by cuttings. LINAGES. THE FLAX ORDER. Series Disciflorae ; Coh. Geraniales, Benth. et Hook. Diagnosis. Herbs, or sometimes shrubs, without stipules ; with re- gular symmetrical hermaphrodite flowers, 4-5-merous throughout ; calyx imbricated ; petals convolute in aestivation ; stamens usually 5, coherent at the base, often with intervening sterile stamens ; ovary compound, of about as many carpels as there are sepals ; styles distinct ; capsule many- celled, each cell divided more or less perfectly into two by a false septum from the dorsal suture, each compartment with one seed, having a straight oily embryo and with, or rarely without, perisperm. Illustrative Genera : Litmm, L. ; Radiola, Dillen. Affinities, &c. Most nearly related to Oxalidaceae, but likewise con- nected with Caryophyllacete, Malvaceae, and Geraniaceae by the general structure of the flowers, the coherent stamens, &c. ; but the simple entire leaves and the peculiar structure of the capsules are very distinctive marks. From Malpighiaceae they differ in their giandless calyx. Distribution. A small Order, generally diffused, but most abundantly so in Europe and North Africa. Qualities and Uses. Linum cdtharticum, a native weed, has active purgative properties ; but the most important plant of the Order is L. iisitatisswmm, the liber-fibres of which constitute Flax, while the seeds, THALAMIFLOR^. 237 known as Linseed, yield a most valuable drying-oil, and their cake forms an excellent material for fattening cattle. r !The flowers of many species of Linum are very snowy (blue, yellow, pink, &c.), but are mostly fugacious. The flowers of some are dimorphic. OXALIDACE^E. WOOD-SORRELS. Series Disciflorse ; Tribe of Geraniaceae, Bentli. et Hook. Diaf/nosis. Herbs, or rarely shrubs or trees, with an acid juice; mostly compound alternate leaves ; regular, symmetrical, hermaphrodite, 5-merous flowers ; calyx imbricated, and petals convolute in aestivation ; stamens 10, somewhat monadelphous ; styles 5, separate ; capsule 5- celled, several-seeded ; seeds perispermic : embryo straight or curved. Radicle superior. Illustrative Genera : Oxalis, L. ; Averrhoa, L. Affinities, &c. Nearly related to Geraniacese, with which Bentham and Hooker unite them. From Linacese they may generally be distinguished by their compound leaves ; but the septa in the capsules of that Order afford the most constant distinction. The seeds of Oxalis have an elastic fleshy coat, which opens with elasticity and expels the seed when ripe. Some regard this as an aril, others as a development of the testa. The leaves of many kinds are sensitive, especially Oxalis sensitiva and Aver- rhoa Bilimbi ; but others possess the quality in lower degree. O. bupleu- rifolia and some other species have phyl lodes. Distribution. A rather large Order, the members of which are gene- rally diffused in temperate and hot climates ; most abundant in America and at the Cape of Good Hope. The shrubby kinds belong to hot climates. Qualities and Uses. The most marked property of Oxalis is the acid juice, depending on the presence of oxalic acid. O. Acetosella, Wood- sorrel, abounds in our woods. Averrhoa Bilimbi, the Blimbing, A. Ca- rambola, the Carambole of the East Indies, have acid fruits, which are eaten by the natives, but used chiefly as pickles by Europeans. Some species of Oxalis have tubers furnishing wholesome food. O. crenata (Arracacha) is used like potatoes in Columbia ; O. Deppei has roots as large as small parsueps. The tubers of O. anthelmintica, the Mitcha- mitcho of Abyssinia, are said to be valuable as an anthelmintic. Many kinds are cultivated on account of the beauty of their flowers. GERANIACEAE. CRANE'S-BILLS. Series Disciflorae ; Co h, Geraniales, Benth. et. Hook. Diagnosis. Herbs or shrubs, with articulated swollen stem -joints ; op- posite or alternate leaves, and membranous stipules ; regular or irregular, symmetrical, hermaphrodite, 5-merous flowers; sepals imbricated and petals contorted in aestivation ; stamens mostly 10, coherent at the base, the alternate ones shorter and sometimes barren ; carpels 5, adherent to a central prolonged axis (carpophore), from which they separate when ripe by the elastic curling-back of the segments of the style, carrying away the 1-seeded dehiscent cocci (h'g. 361). Illustrative Genera : Erodium, Herit. ; Geranium, Herit. ; Monsonia, L. ; Pelargonium, Herit. 238 SYSTEMATIC BOTANY. Affinities, &c. Many points of affinity exist with Oxalidaceae, Linaceas, and Balsaminaceae, likewise with Tropaeolaceee, and, less important ones, with Zygophyllaceae. The arrangement Fig. 361. of the carpels round a column, the palmate leaves of some kinds, the monadelphous stamens, and the convo- luted embryo cause a good deal of resemblance to some of the Malvaceae. The peculiar fruit, the stipules, the swollen joints of the stem, and the convoluted embryo separate this Order from the nearest allies. From Malva- ceae it may be distinguished at once by the imbricated aestivation of the calyx. Pelargonium is remarkable for a spur or pouch extending from the base of the calyx and adherent to the peduncle. Most of the plants have aromatic oil contained in glandular hairs, giving a rnusky or other strong odour. Distribution. The species are numerous. Geranium and Erodium belong chiefly to the temperate parts of Fruit of Geranium, the Northern Hemisphere. Pelargonium abounds at the w i th th carpo- Cape of Good Hope^ and occurs in Australia. One ph species is found in Asia Minor. Qualities and Uses, Astringent and aromatic properties are general. The common weed G. Robertianum had a reputation formerly, and the G. maculafAim, or Alum-root of North America, is a powerful astringent, containing a large amount of tannin. The species of Erodium which emit a musky odour are said to have similar properties. Some have tuberous roots ; that of Pelargonium triste is eaten at the Cape of Good Hope. The species of Pelargonium are remarkable for the beauty of their flowers, which are more or less irregular and spurred, and have great sus- ceptibility of improvement by culture, and a tendency to run into varieties, rendering them established "florist's flowers." Many of them have zones or belts of colour in the leaves. The species of Geranium proper have regular flowers without spurs j others are very fragrant. EALSAMINACE^E. BALSAMS. Series Disciflorse ; Tribe of Geraniacese, Benth. et Hook. Diagnosis. Annual plants with succulent stems, full of bland watery sap ; flowers hermaphrodite, very irregular; stamens 5, somewhat united ; the fruit mostly bursting elastically when ripe. Embryo straight, apeii- spermic. Radicle superior. Illustrative Genera : Impatiens, L. j Hydro- cera, Blum. Affinities, &c. This Order is nearly related to Geraniaceae, and is included in that family by Bentham and Hooker, but may be distinguished by the want of the peculiar carpophore of that Family, and by the much greater irregularity of the flower; the irregular flower also separates it from Oxalidaceae and other allied Orders. This irregular flower does not really depart widely from a symmetrical condition : it is completely 6-merous, except 'in the suppression in Impatiens of the petal opposite the bract THALAMIFLOK^. 239 (which is developed in Hydrocerd) ; the two small lateral sepals, the spur, and the double segment on the opposite side to the spur form an imbri- cated calyx of five parts ; the odd petal opposite the two confluent sepals is suppressed, and the others are generally combined into two 2-lobed bodies, but are sometimes free ; in single flowers the stamens alternate with these ; in double cultivated flowers a second corolline circle of five petals sometimes appears in the place of the stamens, and the stamens alternate again with these. The structure of the ovary and its mode of dehiscence are also deserving of notice. The name of the genus Impatiens is derived from the elasticity with which the capsule bursts when touched after the seeds are ripe. The species are rather numerous. A few are scattered over the globe; but the majority are East-Indian. Their properties are unimportant. I. Balsamina is a valued tender annual plant ; I. Noli-me- tanyere grows in the north of England ; and /. fulva (North America) is naturalized in some places in Southern England. VIVIANACEJE are a small Order of South-American herbs or half- shrubby plants, related to Gerauiaceae, but having a valvate calyx and perispermic seeds. Properties unknown. :. GABDEN-NASTTTBTITTMS. Series Disciflorae ; Tribe Pelargonieae of Geraniaceae, Benth. et Hook. Diagnosis. Smooth trailing or climbing herbs with a pungent juice ; leaves alternate, exstipulate j flowers axillary, irregular, perfect ; sepals 3-5, the upper or posterior one spurred ; petals 1-5 ; stamens 6-10, peri- gynous, distinct ; ovary superior, of 3 or 5 cartels ; style single ; stigmas 3-5 ; ovules pendulous, 1 in each carpel ; fruit dry ; carpels separating as indehiscent achenes from a central axis ; seeds large, aperispermic. Illustrative Genera : Tropceolum, L. ; Chymocarpus, Don. Affinities, &c. A small Order of plants, natives of the temperate parts of South America, related to Limnanthaceae, Malvaceae, and Geraniaceae, and included in the latter family by Bentham and Hooker. The genus Tropceolum contains the garden Nasturtiums, or Indian Cresses, notable for their pungent juice, somewhat like that of Cruciferae. Various species have a tuberous root : that of T. tuberosum is eaten in Peru. The spur of the calyx of Tropceolum is curious, resembling that of Pelargonium, but is free from the peduncle. In some cases it would seem to be a tubular process from the receptacle. The flowers are mostly showy and of great variety of colour. The Canary Creeper, T. pereyrinum or adun- cum, may be noticed for the power of the full-grown plant to obtain its nourishment apparently almost entirely from the atmosphere, and for its climbing by twining its petioles, like Clematis. LIMNANTHACEAE, a small Order of North- American plants, are chiefly distinguished from Tropaeolacese, with which they are associated in the family Geraniacece by Bentham and Hooker, by their regular flowers, erect ovules, and the adherence of the stamens to the calyx. Their properties are analogous. Limnanthes (California) has showy flowers. Flwkia (United States) is a mere weed. 240 SYSTEMATIC BOTANY. ZYGOPHTLLACE.E. BEAN-CAPERS. Series Disciflorae ; CoJi. Geraniales, Hook, et Benth. Diagnosis. Herbs, shrubs, or trees with opposite stipulate, mostly imparipinnate, not dotted leaves ; calyx and corolla 4-5-merous, imbri- cated in aestivation ; stamens twice as many, hypogynous, each often at the back of a scale ; ovary surrounded by glands or a toothed disk, more or less deeply 4-5-lobed, 4-5-celled ; fruit capsular ; dehiscence valvular or into cocci ; few-seeded ; perisperm sparing or none. Illustrative Genera: Tribuhis, Tournef. ; Pef/aunm, L, ; Fagonia, Tournef. ; Zygophyllum, L. ; Larrea, Cav. ; Guaiacum, Plum. ; Melianthus, L. (?). Affinities, &c. This order is very closely allied to Rutaceae (but differs in habit, the scaly stamens, and dotless leaves) through Peganum, which is placed here chiefly on account of its stipulate, not dotted, opposite leaves. With SimarubacesB it agrees in the attachment of the stamens at the back of a scale, but differs in the short styles. Melianthus is an anomalous genus, which by some authors is taken as the type of a distinct Order supposed to have its nearest relations in Geraniaceae and Sapindaceae. Zygophyllese are closely related to Malpighiacea3, but differ in their glandless calyces, scaly stamens, &c. Distribution. The species are not very numerous, and are chiefly found in the warm temperate regions of the globe. Zygophyttum and Tribulus are especially characteristic of dry regions of Egypt, Arabia, and Scinde. Qualities and Uses. The so-called gum-resin, Guaiacum, is derived from Gnaiacum officinale, the bark and wood of which are also employed as diaphoretic and sudorific agents ; G. sanctum has similar properties. The leaves of these and of Porliera are used in place of soap for scouring in the West Indies. The remarkably hard wood called Lignum Vitae is derived from Guaiacum officinale or some other species ; all the arborescent plants of this Order have extremely hard wood. The flowers of Zygo- phyllum Fabago are used in the East for pickles, under the name of Bean- capers. The seeds of Peganum Harmala are used as spice in Turkey, and also in the production of the celebrated Turkey-red dye for cotton. Larrca mexicana is known by the name of the Creasote-plant. Zygophyllum simplex has a very bad odour. RUTACEJL THE RITE ORDER. Series Disciflorae ; Coh. Geraniales, Benth. et Hook. Diagnosis. Herbs, shrubs, or trees with simple or compound exstipu- late leaves, dotted with transparent glands containing aromatic or acrid oil ; flowers regular, 3-5-merous ; the stamens equal to or twice as many as the sepals ; the 2-5 pistils separate or combined into a compound ovary with as many cells, sessile or raised on a prolongation of the recep- tacle (gynophore) or glandular disk; style simple, or divided below; fruit with the carpels either coherent or separating and bursting by one or both sutures ; seeds in pairs or solitary ; perisperm present or absent, radicle superior. Illustrative Genera : Galipea, Aubl. ; Ticorea, Aubl. ; THALAMIFLOlLa:. 241 Boronia, Smith ; Eriostemon, Smith ; Correct, Smith ; Diosma, L. ; Ba- rosma, Willd. ; Dictamnus, L. ; Ruta, Tournef. Affinities, &c. This large Order is sometimes divided into two, Rutaceas and Diosmeie, the latter including the greater part of the genera ; but the distinctions seem insufficient the Boroniece, which have the separable endocarp supposed to be characteristic of Diosmece, having perispermic seeds like Rutece. Bentham and Hooker make the order a very compre- hensive one by including the following as tribes : 1. Cusparieae/2. Ruteae, 3. Diosmeae, 4. Boronieae, 5. Xanthoxyleae, 6. Toddalieae, 7. Aurantieae (see ante, p. 235). Most of these are separately treated in the present work, as being more readily understood bv beginners. The Order is connected with Zygophyllaceae by Peyanum ; it is related also to Xanthoxylaceae, which are perhaps merely polygamous Rutaceae. There is also an affinity with Aurantiaceas (which differ, however, in the fruit), and with Ana- cardiaceae. Correct, with its monopetalous corolla, seems to approach Ericaceae, to which the Boroniece have much resemblance in habit. From Simarubaceae and Terebinthaceae Rutals differ in their glandular leaves and in the nature of the fruit. Distribution. Ruta and its allies are found chiefly in Europe and North Asia; Diosma, Barosma, &c, at the Cape of Good Hope ; Boronia, Eriostemon, &c. in Australia ; and Galipea, Esenbeckia, and their related genera in Equinoctial America. Qualities and Uses. Generally remarkable for a strong aromatic or foetid odour, and possessing antispasmodic and tonic properties. Angostura bavk is derived from Galipea officinalis, and apparently from G. Cmparia (Bonplandia trifoliata) ; Melambo bark probably from some allied plant. The bark of Escribe ckia fcbrifuga is used in place of Cinchona in Brazil; and that of Ticorea febrifuya is another of the " Quinas" of Brazil. The Bucku plants of South Africa are species of Barosma, Diosma, and their allies; their foliage, which is extremely glandular, has a very strong odour ; and I), crenata, serratifolia, and others are used as antispasmodic and diuretic agents. The leaves and unripe fruits of Rue (Ruta graveo- lens) are antispasmodic, and are also said to be emmenagogue and anthel- ruintic : R. montana is acrid ; and its juice is described as vesicating the skin, and even producing erysipelas and ulceration. The leaves of Correct alba aud other species are used by the settlers in Australia for Tea. Many of the Rutaceae are favourite greenhouse plants, such as Boronia, Eriostemon, c. Dictamnus Fraxinella, a South-European plant, common in our gar- dens, is very glandular, and it is said that the volatile oil renders the atmo- sphere about the plant inflammable in very hot weather. This account requires confirmation. These glandular plants are of course very inflam- mable in themselves. The root of Toddalia aculeata is used in India as an aromatic. XANTHOXYLACE^E are trees or shrubs with alternate or opposite, exstipulate, simple or compound, dotted leaves, and flowers resembling those of Rutaceae in almost every respect, except that they are constantly polygamous, and sometimes have succulent fruit; seeds perispermic.-- Illustrative Genera : Xanthoxylon, Kunth ; Ptelea, L. Affinities, &c. The Xanthoxylacese are united by some authors with tho Rutaceae ; their more remote relations are with Aurantiaceae and Ana- 242 SYSTEMATIC BOTANY. cardiacese, which, however, not only differ in their fruits, but their seeds have no perisperm. There is a considerable affinity to the Euphorbiaceae and to Fraxinus among the Oleacese, Ptelea having- even a samaroid fruit. Distribution. The species are not very numerous, and are generally distributed, but are most abundant in America. Qualities and Uses. Pungent and aromatic. Xanthoxylon, a genus re- presented in North and South America, as well as in India, China, &c. ; eminently possesses these characters, its species being commonly called Peppers in their native countries. X. Clara and fraxineum (North Ame- rica) a,re powerful diaphoretics and sudorifics ; X. nitidum (China) has a similar reputation; X. hyemale (Brazil), X. piperitum (China), &c. are analogous. The unripe capsules of X. Rhetsa are aromatic, resembling orange-peel. The fruit of Ptelea has a strong aromatic bitter taste, and has been used as a substitute for hops. SIMARUBACE^E are trees or shrubs with alternate exstipulate leaves, without dots, usually compound ; flowers diclinous or polygamous j calyx and corolla 4-5-merous ; stamens 8-10, emerging from an hypogynous disk, filaments usually with a scale at the back ; anthers bursting longitudi- nally j ovary stipitate, 4-5-lobed ; fruit of 4-5 indehiscent drupes round a common receptacle, or capsular or samaroid, with 1 pendulous aperi- spermic seed in each compartment. Illustrative Genera : Quassia, L. ; Simaruba, Aubl. ; Ailanthus, Desf. Affinities, &c. Belonging to the Rutaceous group, these plants are most closely allied to the Zygophyllacese by the stamens and dotless leaves, to the Ochnaceae by the deeply lobed ovary, differing from the former in the structure of the fruit and the number of seeds in a cell, from the latter by the absence of a large disk and the dehiscence of the stamens. Distribution. A small Order, the members of which inhabit South America, Africa, the East Indies, and the Malay archipelago. Cneorum occurs in the Mediterranean district. Qualities and Uses. The most striking property is gTeat bitterness, whence they are used as tonics. Quassia or Bitterwood, used as a tonic, as a fly-poison, and as a substitute for hops in beer, is derived from this family. Quassia amara (Surinam) is stated to be the true plant ; but Picrasma or Picrana excelsa yields the wood usually imported. The bark of the root of Simaruba amara is used in the same manner. Jjrvcca antidysenterica has similar qualities, and was formerly mistakenly supposed to be the source of false Angostura bark. Simaba Cedron has a reputation for curing snake-bites ; but recent experiments throw doubt on this. Ai- lanthus glandulosa, the " tree of heaven," is commonly grown for ornament in this country ; its leaves afford nutriment to a species of silkworm. OCHNACEAE are scarcely separable from Simarubaceae ; but the ovary is composed of carpels seated on a large fleshy disk instead of upon a stipe, the elongated anthers often open by pores, and the simple leaves are without stipules. The thick gynophore of this Order affords a close connexion between Rutaceae and Geraniaceae. The properties are similar to those of Simarubaceae. is the name applied to a small group of plants belonging to one genus, Coriaria, of obscure affinities, placed in this neighbourhood THALAMIFLOE^J. 243 by Lindley, but differing from most of the Rutales in their pendulous ovules with dorsal raphe. In some respects they approach PhytolaccfB and Tropceolete. These plants have dangerous properties. Of C. myrtifolia the leaves, which are sometimes used to adulterate Senna, are said to pro- duce tetanus ; the berries are poisonous. The fruits of other species are said to be edible, but the seeds poisonous. C. myrtifolia and ruscifolia are used in dyeing, infusion of the leaves giving a dark blue with sulphate of iron. PITTOSPO RACEME are trees or shrubs, often climbing plants, with alternate exstipulate leaves ; flowers regular j calyx and corolla 4-5-merous, imbricated, deciduous j stamens 5, hypogynous, alternate with the petals, opening longitudinally or by apical pores ; ovary free, 2-celled and some- times with 2-3 imperfect cells ; style single, stigmas equal to the pla- centas ; ovules horizontal or ascending, anatropous ; seeds numerous ; embryo minute, in fleshy perisperm. Illustrative Genera : Pittosporum, Soland. ; Sollya, Lindl. ; Euiarmera, Smith. Affinities, &c. A small Order, placed by DeCandolle between Polyga- lacese and Frankeniacere, by A. Richard near Rutacese, by Endlicher in the neighbourhood of Rhamnacese. Lindley regards them as near Vitaceae. From Tremandracese and Olacacese they differ in their imbricate sepals and petals and their numerous ovules. In other points they resemble Celastrineae, but they have no disk and no aril. Decaisne points out an affinity with some Ericads, as Ledum. The plants are chiefly from Aus- tralia ; the berries of Billardiera are eaten, having a pleasant acid flavour ; but a resinous quality pervades the whole Order. Some of the species are cultivated on account of their flowers and coloured berries, as Sollya, Billardiera, &c. VITACEAE. VINES. Series Disciflorse ; Coh. Celastrales, Benth. et Hook. Diagnosis. Shrubs with a watery juice, usually climbing by tendrils, placed opposite the leaves, with small regular flowers, a minute truncated calyx with the limb mostly obsolete ; stamens as many as the valvate petals, and superposed to them, springing from a disk surrounding the ovary. Fruit succulent ; seeds bony j perisperm hard. Illustrative Genera : Vitis, L. j Pterisanthes, Blum. Affinities, &c. The relations of this Order, sometimes called Ampelidese, are somewhat complex ; a portion of the plants are related to Meliacese, CelastrineaB, and Rhamnacese ; but the nearest connexion would appear to be to the epigynous Order Araliaceae, especially through the Ivy, Hedera. The characters of the group, however, are very distinct, in the hypogynous stamens superposed to the petals, and the climbing habit. The superposition of the stamens to the petals is due to the abortion of five antisepalous stamens, which are sometimes represented by five glands of the disk. The tendrils by which the stems climb are flower-branches, often exhibiting a few nodules representing abortive flowers. They are extraaxillary, and are considered by some to be terminal buds deflexed, by others as formed by a partition of the growing point, one division 244 SYSTEMATIC BOTANY. forming the tendril, the other the shoot. In Ampelopsis Dutailly thinks the tendril is an axillary bud which remains attached to the stem, elon- gates with it, and ultimately separates from it some distance above the axil in which it originates. In some cultivated Vines the seeds are con- stantly suppressed, while the fruit is perfected, as in the varieties yielding the Sultana raisins and the Zante grape or " Currant." Pterisanthes, a Javan plant, has a very extraordinary structure : its numerous barren and fertile dowers are developed on a very large foliaceous peduncle having the form of a number of divergent plates set edgewise at the end of a long- slender stalk ; the fertile flowers and berries are sessile on both surfaces of the laminae, the edges being fringed with stalked barren flowers. The separation of the petals at their bases, remaining coherent above so as to form little 5-rayed stars, is worthy of notice in this Order. The species of Ampelopsis, known as u Virginia Creepers," exhibit some interesting phenomena, viz. the assumption of a crimson colour by the foliage in autumn, and the adaptation of their tendrils to form organs of attachment to walls : the points of the tendrils are negatively heliotrophic, and in- sinuate themselves into little holes and cracks, especially in brickwork, and then expand inside the cavities so as to fix themselves as the stone masons fix their u lewis," or key, into large blocks of stone. Distribution. The genus Vitis, including Ampelopsis and Cissus, con- tains a large number of species, natives for the most part of tropical and subtropical regions. The remaining genera have only a very few repre- sentatives. The Vine (Vitis vinifera) is supposed to* be a native of the shores of the Caspian ; but it has run wild in South Europe, and is culti- vated all over the world where the temperature is not too low or too high : in the last case it runs away to leaf and does not produce fruit. The stems and roots of some of the Cissi in the East Indies are infested by the parasitical Ilafflesiacea3 and Balanophoracete. In a fossil state they have been found in Miocene as well as in more recent deposits. Qualities and Uses. The properties of the Vine (Vitis vmifera}, with its innumerable varieties, are universally known ; the Fox-grapes ( Vitis vulpina and Labrusca) of North America have similar properties when cultivated, but are inferior. The berries of the Cissi are acrid ; some yield a colouring-matter. The sap of the stems and leaves generally of the Order is sour, containing tartaric acid. Series 2. CALYCIFLOB^;. Flowers usually with a calyx and corolla ; the petals distinct, springing from the calyx or from a perigynous disk ; the stamens perigynous or epigynous. Exceptions, &c. The character of this Subclass, founded on the insertion of the petals and stamens upon the calyx, is very artificial, and is liable to exception in certain genera of Orders referable here. On the other hand, it is met with exceptionally in Thalamifloral Orders ; and many cases occur where the conditions are difficult to ascertain. Moreover it causes the se- paration of very natural groups of Orders, such as the removal of Anacar- diacese, which has both hypogynous and perigynous genera, from the Sub- CALYCIFLOE^:. 245 class which includes the Rutaceae, in accordance with the structure of the majority. Bentham and Hooker, apparently with a view to remove some of these anomalies, have proposed a subclass or series which they call Disciflorse, the most important character of which consists in the presence of a large disk or expansion of the receptacle attached to the calyx or to the ovary, and from which the petals and stamens spring ; it thus includes some Thalamifloral and some Calycifloral Orders (including the Orders comprised in the cohorts Geraniales, Olacales, Celastrales, and Sapindales). The separation of the Perigynous from the Epigynous Orders is rendered impracticable by the occurrence of the two conditions in one Order, as in Rosaceae. United petals occur in some exceptional cases, as in Cucurbi- taceae. CELASTRACE^E. THE SPINDLE-TEEE OEDEE. Series Disciflorae j Coh. Celastrales, Benth. et Hook. Diagnosis. Shrubs with simple, mostly alternate leaves, and with small deciduous stipules ; small regular flowers, the 4-5 sepals and petals im- bricated in aestivation ; stamens as many as the petals and alternate with them, inserted on a disk tilling up the bottom of the calyx ; seeds mostly arillate, perispermic. Illustrative Genera : Euonymus, Tournef. ; Celastrus, Kunth ; Catha, Forsk. ; Elceodendron, Jacq. Affinities, &c. Related to Rhamnaceae, differing in the imbricated calyx and the stamens alternating with the petals. Aquifoliaceae, a sympe- talous Order, is very nearly allied ; but the Celastraceae appear to have closer relations with some Thalamifloral Orders, such as Malpighiaeefe through Hippocrateaceee. The fleshy coat of the seed of Euonymus is described by Planchon as an arillode or false arillus, arising from the margin of the micropyle. Distribution. A large Order, the species of which are generally diffused, but more abundant outside the tropics. Qualities and Uses. More or less acrid, with oily seeds. Euonymus europaius, the common Spindle-tree of our hedges, is used for gunpowder- charcoal. The inner bark of E. tingens is usod in dyeing ; the seeds of E. europaius are said to be purgative and emetic. The bark of Celastrus scandens has the same properties. Catha edulis has stimulant properties, and the leaves are largely used by the Arabs under the name of Kat. The drupaceous fruits of Elac,odendron Kubu are eaten at the Cape of Good Hope. STACKHOUSIACE^E constitute a small Order of Australian plants inter- mediate between Celastraceae and Euphorbiaceae ; their corolla is sym- petalous. HIPPOCRATEACE^:, which have hypogynous petals and more or less epigynous stamens, are most nearly related to Celastraceae (with which, indeed, they are combined by Bentham and Hooker), connecting them with Malpighiaceae, Aceraceae, and through Staphylea with Sapindaceas, &c. They are chiefly South-American trees or climbing shrubs, some with edible fruit. 246 SYSTEMATIC BOTANY. CHAILLETIACEJE is another small Order, usually placed in this neigh- bourhood, but with obscure affinities. Chailletia toxicaria has a poisonous fruit, called Kat's-bane at Sierra Leone. RHAMNACE^. THE BUCKTHORN OEDEE. Series Disciflorae ; Coh. Celastrales, JBenth. et Hook. Diagnosis. Shrubs or small trees with simple, alternate, stipulate, or exstipulate leaves ; small and regular flowers (sometimes apetalous) ; the 4-5 perigynous stamens as many as the valvate sepals, and alternate with them (superposed to the petals when these are present) ; disk fleshy ; ovary free or inferior ; berry or pod with one seed in each cell, perispermic, without an aril. Illustrative Genera : Ventilac/o ; Paliwus, Tournef. ; Rhamnus, Juss. ; Hovenia, Thunb. ; Colletia ; Gouania. Affinities, &c. The Rhamnacese are clearly distinguished from the Celas- traceae bj the position of the stamens before the petals. The calycifloral condition of their stamens, the fleshy disk, and the separate petals indicate great difference from the corollifloral Order Aquifoliacese, also formerly associated with them. Brongniart thinks their nearest relations are to the hypogynous Byttneriaceae and to Euphorbiacese. Some of the genera have free, others adherent ovaries. Distribution. A rather large Order, the species of which are generally diffused. Qualities and Uses. Some acrid and purgative, some with bitter tonic properties, others with edible fruits. Rhamnus includes R. catharticus, the Buckthorn, from the berries of which a purgative syrup is made, also the colour termed Sap-green. The dyeing material called French berries consists of the unripe berries of JR. infectorius, saxatilis, and amyydalinus. Zizyphus has edible fruit, called Jujubes (Z. wlga/ris, Z. Jttjuba, &c.). The charcoal made from the wood of jR. Frangula is used for gunpowder- making under the name Dog-wood. Z. Lotus is supposed by some to be the Lotus of the ancients, although others think this was Nitraria. The peduncles of Hovenia dulcis enlarge into a succulent fruit, eaten in China ; other genera also furnish edible berries. The leaves of Ceanothus ameri- canus are consumed as New-Jersey Tea, and those of Sageretia theezans are used for Tea by the poorer Chinese. ANACAEDIACEJE OR TEEEBINTHACE^E. THE SUMACH OEDEE. Series Disciflorae ; Coh. Sapindales, JBenth. et Hook. Diagnosis. Trees or shrubs with a resinous or milky acrid juice ; dot- less alternate leaves, and small, often polygamous, regular flowers ; calyx small, usually with 5, sometimes 3-4 or 7 lobes, persistent; petals equal in number to the lobes of the calyx, or wanting; stamens the same num- ber or double or more, inserted on an annular fleshy disk, or coherent and perigynous. Ovary single, or rarely of 5 or 6 carpels, superior (rarely CALYCIFLOim 247 inferior), 1 -celled ; style 1, or 8 or 4, sometimes none ; stigmas twice as many ; ovules solitary, on a long funiculus. Fruit indehiscent, commonly drupaceous ; seed without perisperm. Illustrative Genera : Tribe 1. ANA- CARDIEJE. Ovary 1-celled. Rhus, L. ; Melanorrhea, Wall. ; Schinus, L.; Semecarpus,~L. "Tribe 2. SPONDIEJE. Ovary 2 5-celled. Spondias^. Affinities, &c. The prominent differential characters of this order reside in the solitary ovule, with ventral raplie and inferior micropyle, or dorsal raphe if the micropyle be superior. This Order is related to the Xantho- xylaceae in many respects, but differs in the structure of the ovary and seed. From the Burseracew also it is divided by the same characters, although Spondias connects them as regards the fruit ; while the same peculiarities relate it on the other hand to certain Connaracese, Rosaceee, and Leguminosae. Distribution. A large Order, the species of which are chiefly tropical, diminishing rapidly beyond the tropics. Qualities and Uses. The resinous juice of these plants is acrid, or violently irritating and poisonous 5 it often becomes black in drying. Some kinds, however, yield edible, and even valuable fruits. Anacardium occidentals, the Cashew-nut, is remarkable for the curious fleshy enlarge- ment of the peduncle supporting the nut ; this peduncle is edible, as is also the seed when roasted ; but the pericarp contains acrid volatile oil. A gum-resinous juice exudes from the wood, called Gomme d' Acajou, which is used when fresh as a varnish. Semecarpus Anacardium, the Marking-nut, Melanorrhea usitatissima, Staff maria verniciflua, Rhus vernix, &c. are among the plants furnishing varnishes used in the East Indies, China, and Japan for lacquered ware ; their juices are white at first, and become black after exposure to the air. Mastic is obtained from Pistacia atlantica and P. Lentiscus, Scio turpentine from P. Terebinthus ; the fruit of Pistacia vera is the Pistachio-nut, highly valued in Eastern cookery. Mangifera indica, with numerous varieties, yields the well-known tropical drupe called the Mango. The Sumachs, species of Rhus, are acrid and poisonous, affecting some constitutions more than others, and sometimes producing violent erysipelas when applied to the skin. R. Toxicodendron is the Poison-Oak of North America; R. venenata, the Poison-Elder or Poison-Sumach. R. typhina, ylabra, and Coriaria have acid fruit and astringent bark, used in tanning ; JR. Cotinus (which is sometimes grown in our shrubberies under the name of the Wig- plant, from the hair-like nature of the sterile flower-stalks) yields the dye-wood called Young Fustic ; R. Metopium, the Hog-gum of Jamaica, a powerful purgative and emetic. Spondias purpurea and S. Mombin yield succulent fruits eaten in Brazil and the W. Indies under the name of Hog-plums ; S. Cytherea or didcis affords a delicious fruit in the Society Islands. SABIACEJE are a small Order of East-Indian plants, removed by recent authors from Anacardiaceae, where they were formerly placed as ano- malous forms. They are remarkable for the superposition of the parts of the flower. CONNARACE^E form, an Order of tropical trees and shrubs, usually placed near Anacardiaceae, but destitute of resinous juice, and with ortho- tropous ovules ; the fruits are apocarpous and follicular. They are also allied to the Xanthoxylacese. The seeds sometimes have an aril ; those 248 SYSTEMATIC BOTANY. of some species of OmphaloUwn are edible. The Zebra-wood, used in cabinet-making, is stated by Schomburgk to be the produce of a Guiana species of this genus, O. Lamberli, of great size. BURSERACE^E. The Balsam Order consists of trees or shrubs abounding in balsam or resin, with alternate or opposite compound leaves, sometimes stipulate and dotted ; flowers perfect, or sometimes diclinous by abortion ; calyx persistent, with 25 divisions ; petals and stamens perigynous, outside a perigynous disk ; ovary 1-5-celled, superior, sessile in or upon the disk ; ovules in pairs ; micropyle superior ; raphe ventral ; fruit dry, 1-5-celled, often splitting into valves ; seeds aperispermic ; cotyledons plicate, rarely flat. Illustrative Genera : Boswellia, Roxb. ; Balsamodendron, Kunth 5 Canarium, L. ; Amyris, L. Affinities, &c. The Burseracese (or, as they are sometimes called, Amy- ridaceae), excepting the genus Amyris itself, have a many-celled fruit, which forms a link between Anacardiaceae and Aurantiaceas ; but the shell of the fruit is hard here, and opens by valves. Amyris has dotted leaves. The ovules in pairs separate them from Anacardiaceee. The want of scales to the stamens separates them from Simarubeae. From Rutals they differ in their aperispermic embryo. From Aurantiads they differ in the fruit. Distribution. The Order consists of about 150 species, distributed throughout the tropics of Asia, Africa, and America. Qualities and Uses. Fragrant resinous j uices are the chief character- istics of this Order. Boswettia thurifera,Jloribunda, and glabra yield the East-Indian Olibanum or Frankincense ; B. papyrifcra (Abyssinia) yields a similar Olibanum, and has a remarkable inner bark, capable of separa- tion into sheets, which are used as paper. Balsamodendron Myrrha yields Gum Myrrh ; Balm of Mecca is produced by B. Opobalsamum and B. f/ifeadense. B. Mnkul yields Googal, or Bdellium ; B. piibescens another balsam, almost soluble in water. Amyris hexandra and A. Plumieri yield Elemi ; the wood of A. balsamifera is known as Lignum Rhodium ; the balsam of A. toxifera is poisonous. Idea Icicariba yields Brazilian Elemi, I. Carana American Balm of Gilead ; and other species afford similar pro- ducts. Elaphrium iomentosum supplies one of the kinds of Tacamahaca, E. elcmiferum Mexican Elemi ; and Canarimn commune furnishes East- Indian or Manilla Elemi. Bursera paniculata (Mauritius) is called Bois de Colophane, giA T ing out freely when wounded an oily juice smelling like turpentine ; B. yummifera yields Chibou resin, B. acuminata Resin of Oarana ; Hefhuigia balsdmifera, Beaume a cochon, used as a substitute for Copaiba. The wood of Idea altissima is used for canoes in British Guiana, under the name of Cedar-wood. LEGUMINOS^. THE PULSE ORDER. Series Calyciflorae ; Coh. Resales, Benth. et Hook. Diagnosis. Herbs, shrubs, or trees, with irregular, often papilio- naceous or regular flowers ; stamens 10 or rarely 5, or sometimes indefinite, diadelphous, monadelphous, or distinct ; pistil simple, CALYCIFLOR,E. 249 free, becoming a legume or lomentum ; seeds usually aperispermic ; leaves mostly alternate, stipulate, usually compound. Character. Thalamus usually flat or convex. Calyx more or less deeply 5-fid, the odd lobe in front or next the bract ; lobes often unequal and variously combined. Corolla : petals 5, or 40 by suppression, springing from the bottom of the calyx, papilionaceous or re- gular : the odd petal, when present, posterior (figs. 363, 366). Stamens definite or indefinite, springing from the calyx, rarely hypogynous, distinct or coherent in one or two bundles (9 + 1, fig. 367), or rarely in three ; anthers opening by chinks or by pores. Ovary usually solitary, simple, of one carpel (very rarely 2 or 5), 1 -celled, 1-, 2-, or many-seeded ; style and stigma simple (fig. 368). Fruit : a legume, lomentum, or rarely a drupe ; seeds attached to the upper (ventral) suture, 1 or many, sometimes with an arillus ; embryo without, rarely with perisperm, straight, or with the radicle folded on the cotvledons. Fig. 362. Fig. 363. Fig. 362. Compound leaves, terminating in a short tendril, and stipules of B^an (Yicia) Fig. 363. Papilionaceous corolla of Pea. Fig. 364. The separated petals : a, verillum ; b, 1, alee ; c, e, carina. 250 SYSTEMATIC BOTANY. Fig. 365. Fig. 367. Fig. 366. o Fig. 368. Fig. 365. Inflorescence, calyx, corolla, &c., of Bean. Fig. 366. Ground-plan of a Papilionaceous flower the bracket represents the position of the bract, the O that of the axis. Fig. 367. Diadelphous stamens of Leguminosae. Fig. 368. Stipitate ovary, style, and stigma of Colutea. This large Order is divided into three Suborders, which are dis- tinguished by the following characters : 1. PAPILIOKACE^E. Corolla papilionaceous, imbricated in the bud, with the upper, odd petal, called the standard or " vexillum," exterior. 2. C^SALPINIE^E. Corolla imbricated in aestivation, the odd petal with its edges inside the lateral ones. 3. MIMOSE^E. Corolla valvate in aestivation. The typical floral formula is |8 5, P5, A 5 + 5, Grl, but much variation from it occurs. This vast Order is further subdivided into several tribes, the subdivisions being founded on the degree of cohesion of the sta- mens, the nature of the pod and cotyledons, the leaves, habit, &c. Chorozema, Labill. Lupinus, L. Lotus, L. Trifolium, L. ILLUSTBATIVE GENERA. 1. PAPILIONACEJE. Astralagus, L. Pisum, L. Arachis, L. Ornithopus, L. Phaseolus, L. Dalbergia, L. Sophora, L. Swartzia, Willd. CALTCIFLOR^;. 251 Csesalpinia, L. Cassia, L. Parkia, L. Adenanthera, L. 2. Tamarindus, L. Copaifera, L. 3. MlMOSEJE. Mimosa, L. Acacia, Willd. Ceratonia, L. Sclerolobiuin. Inga, Wittd. Prosopis, L. Affinities, &c. This immense Order presents very considerable variety of structure within its wide limits j and but one character is absolutely constant, the position of the sepals * * The irregularity of the corolla disappears altogether in the Mimosece, and the legume is exchanged for a drupe in Detarium and Dipteryx : this causes a near approach to the Rosacese ; but it may be noticed that when the flower is regular the fruit is leguminous, and vice versa ; and the anterior position of the odd sepal of the calyx is an unexceptional character of this Order. The Casalpimea have the papilionaceous exchanged for a spreading irregular form, or the petals are suppressed. In Mimosece the stamens are hypogynous. The last fact brings the Order closely into relation with the Anacardiacea3, from which it is not easy to distinguish some of the apetalous Ccesalpiniea at first sight. The single carpel in the ovary of this Order is almost a universal cha- racter j two carpels, however, appear to be normally present in Diphaca Fig. 369. Fig. 370. Fig. 369. Legume of Pisum. Pig. 271. Legumes of Medicago. Fig. 370. Lomentum of A coda. Fig. 372. Legume of Astragalus : a, entire ; 6, cut across, to show the false partition. and C&salpinia diyyna ; a double ovary sometimes occurs as a monstrosity in Wistaria sinensis, in Gleditschia, and in the French bean (Phaseolm) j and a Mimosa with 5 carpels (thus a symmetrical flower) is said to have 252 SYSTEMATIC BOTANY. been seen by St.-Hilaire. The simple legume presents a great variety of conditions, both of form, consistence; and dehiscence. Its normal form is such as we see in the garden Pea (fig. 389) ; in Colutea (the Bladder-Senna) it is inflated and membranous ; in Astragalus the dorsal suture turns in and forms a false septum (fig. 372) ; in Phaca it is spongy or fleshy ; in many cases it is woody ; it may be straight or curved, or even spirally curled (Medicayo, fig. 371) ; in the lomentaceous form it is constricted at intervals, often breaking into 1-seeded joints (fig. 370) ; in Cathartocarpus it is cylindrical ; in Detarium and Dipteryx the 1-seeded ovary develops a bony endocarp and fleshy epicarp, and becomes a drupe, like JTJ O . 373. the Almond. The dehiscence is equally varied : normally both sutures open and the valves separate ; in Hcematoxylon the valves adhere at the sutures and split in the middle. In Carmichaelia the valves separate from the suture ; in Orni- thopuSj &c. the lomentum breaks up, and the pieces either open or remain indehiscent; in Entada the lomentaceous pod is opened by the valve? separating in pieces. In Catharto- carpus, Arachis y Tamarindus, and other cases no dehiscence occurs at all ; and in Cathartocarpus and Tamarindus a pulp is formed inside the legume. The irritability of the leaves of many Leguminous plants is a striking characteristic : it is most remarkable in the Hedi/sarece, as in Smithia, Desmodium, &c., and in Mimosece ; but it exists in a lower degree very commonly, even in the Locust-tree (Robinia Pseudo-acacia}. The Acacias are no- ea ticeaBle for the phyllodial petioles, which often wholly re- of flowers, of place the leaves (fig. 373). Acacia. Distribution. The Order comprises nearly 7000 species. The Papilio- nacece are universally distributed, but are most abundant in warm climates ; some genera are widely diffused, others almost confined to particular parts of the globe, as Australia, North or South America, Cape of Good Hope, &c. The CcemlpmiecB and Mimosece are chiefly tropical ; but the latter abound beyond this limit in Australia. Traces of Leguminous plants have been observed in the Lower Eocene and more recent formations. Qualities and Uses. This Order contains a vast number of plants ; and among them there is an exceeding diversity of properties. Those with mild juices are frequently exceedingly nutritious; when the juices are more concentrated, they become either purgative or astringent, and some of them poisonous ; the poisonous properties occur in all parts, but chiefly in the seeds and bark. In other respects they furnish most valuable timber, fibres, gums, dyes, &c. In enumerating some of the most im- portant plants, it will be best to take them under the heads of the Sub- orders. 1. Papilionacea. A large proportion of the common fodder-plants,sucli as Clover (Trifolium), Lucern and Medic (Medicayo], Melilotus, Sain- foin (Onobrychis*), &c., belong to this Suborder ; and various other similar plants are in use in foreign countries, such as species of Astragalus, Cro- talariajuncfia, Desmodium diffusum, Indigofera cnneaphylla, &c. The seeds of many species are eaten, constituting the various kinds of pulse ; such as Broad Beans (Faba), Haricots and Scarlet-Runner Beans (Phaseolus), CALYCIFLORjE. 253 Peas (Pisum, Dolichos\ Lentils, (Ervum, Vicid), Chick-peas (deer), Pigeon-peas (Cajanus), Lupines, &c. The roots of some of these are said to be poisonous, as those of Phaseolus; but, as is well known, the pericarps or pods are eaten boiled in the young state. Saccharine matter exists in the roots of Liquorice ( Glycyrrhiza glabra, with G. echinata and gkmdulifera) ; a kind of Manna is obtained from the Camel-thorn (Alhagi Maurorum) ; Astragalus glycypliyllus has a sweet juice. The tuberous roots of Dolichos tuberosus and lulbosus, Apios, Pueraria, and Lathyrus tuberosus are eaten in the same way as potatoes. Among the purgative species are Bladder-Senna ( Colutea arborescens'), the leaflets of which are often used to adulterate true Senna, and Coronilla JSnunuvBiA C. varia: the last is reputed to be poisonous; various species of Genista, Cytisus (Broom), Robinia, &c. are diuretic and cathartic. The well-known astringent substance Kino is obtained in Africa from Pterocarpus erinaceus, in the East Indies from P. Marsupium, Gum Dragon from P. Draco, and Red Sandal-wood from P. santalinus. A somewhat similar substance to Kino is obtained in the East Indies from the Dakh trees (_Butea frondosa and superba). Erythrina monosperma yields Gum Lac. A few plants of this Suborder yield gum, such as Tragacanth, from, Astragalus verus, creticus, cristatus, gummifer, and strobiUferus. Dyes are obtained from many, as Indigo from Indigofera tinctoria ^ ccerulea, argentea, and probably others, and from Tephrosia Apollinea and other species ; Baptisia tinctoria gives an inferior kind. The flowers of the Butece give a brilliant orange-yellow colour; Sophora japonica furnishes yellow from the pulp of its pods ; Dyer's broom ( Genista tinctoria} gives a good yellow colour, and forms a green with Isatis. Oil is furnished by the seeds of the Ground-nut (Arachis hypogcea) and others. Ornamental and useful timber is afforded by some, as Rose-wood (Palis- sandre of the French) from various Brazilian species of Triptolomea, Itaka- wood of Guiana (Machcerium Schomburyki), Laburnum-wood (Cytisus Laburnum), Locust (Robinia Pseudo-acacia) ; Dalbergia Sissoo and other species, and Pterocarpus dalbergioides, are highly valued in the East Indies. Others furnish fibrous substances, such as Crotalariajuncea, yielding Bengal Hemp. Dipteryx odorata (Tonka-bean) and D. oleifera (Eboe-nut) are used in perfumery. The hairs from the pods of Cowhage (Mucuna pruriens) were formerly used as an anthelmintic. The seeds of As'ragalus bceticus are usv'd as a substitute for arid adulteration of coffee in Germany. The distinctly poisonous plants of this Suborder are numerous. The roots of the Scarlet-runner bean (Phaseolus midtiflorus) and other species are narcotic poisons ; also the seeds of Laburnum ( Cytisus Laburnun , alpinus, &c.), those of Lathyrus Aphaca, and, it is said (but denied by others), those of Abrus precatorius (the scarlet seeds with a black patch, often used as beads), Anagyris foetida, Erciim Ervilia, &c. Indigo is a violent poison ; the shoots of various kinds of Tephrosia, especially T. toxi- fera, are used to poison fish, as is the bark of Piscidia Erythrina, a powerful narcotic. Species of Geoff roya, as G. vermifuga and spinulosa, and Andira inermis and retusa, having drastic purgative and emetic barks, are acrid- narcotic poisons in large doses. Gompholobium, an Australian genus, is said to poison sheep. Physostigma venenosum furnishes the poisonous Calabar bean used as an ordeal by the natives, and in medicine for its use in contracting the pupil of the eye. It acts as a powerful nervous sedative. 254 SYSTEMATIC BOTANY. 2. Ccemlpiniece. This Suborder does not appear to have any decidedly poisonous properties ; "but a purgative quality is very common, as in Senna, Cassia obovata, Senna acutifolia, and lanceolata ; C. marilandica and other North -American species have similar properties. Cassia or Cathartocarpus Fistula has a purgative fruit ; and the pulp of the Tamarind (Tamarindus indica) shares this quality. Besides the Tamarind, other fruits, less acid, are eaten, as the Tamarind Plum (Dialtum indicum) and the Tamarinds of Sierra Leone, which are species of Codarium. Carobs or Algarobs, the legumes of CeratoniaSiliqua (also called St. John's, or the Locust-tree), are used for feeding horses in Spain, and have recently been imported for feeding stock in this country. Gleditschia triacanthos bears a similar fruit, called in North America the Honey-locust ; the fruit of the West-Indian Locust, Hymencea Courbaril, is somewhat similar, but is said to purge when fresh gathered ; a kind of beer is made from it by decoction and fer- mentation. Many Ccesalpiniece have bitter and astringent properties, and are sometimes used in medicine, several of them in tanning and dye- ing, as Divi di vi, the pods of C&salpinia Coriaria, one of the most powerful of known astringents ; the bark of some species of Bauhinia and Cassia are used in similar ways. The dye-woods are important, namely Log- wood (H&matoxylon campechianuni) , Brazil-wood or Pernambuco-wood (Ccesalpinia echinata, brasiliensis, and other species), Cam-wood or Bar- wood (Baphia nitida), &c. The West-Indian Locust-tree (Hymencea Courbaril}) the Purple-heart of Guiana (Copoiferapubiflora and bracteata\ Mclanoxylon Brauena, Eperua falcata, &c. yield very hard and durable timber. The size of some of the Caesalpineous trees of the South-Ame- rican forests is said to be enormous, as much as 84 feet in circumference at the base, where large projecting buttresses occur, and 60 feet at the commencement of the clear run of the trunk. The bark of Bauhinia racemosa and parviflora is used for cordage in the East Indies. Gum is yielded by several, as by Bauhinia retusa and B. emar- gitmta in the East Indies, and Pithecolobitim gummiferum in Brazil. Anime resin ie obtained from Hymencea Courbaril ; Mexican Copal probably from an allied plant : Brazilian Copal from various species of this genus, and from Trachylobium Martianum ; Madagascar Copal, and perhaps that of the East Indies in general, from Hymencea verrucosa. Balsam of Copaiba is derived from various West-Indian and Brazilian species of Copaifera ; Balsam of Peru from Myro.rylon Pereirce : Balsam of Tolu from M. tolui- ferum. Aloexylum Af/aHochum yields one kind of Eagle- or Aloes-wood, the other coming from an Aquilaria. 3. Mimosece. Mucilaginous juices concreting into gum and astringent properties of the bark are the most striking qualities of this Suborder. Gum Acacia and its varieties are yielded by several species of Acacia : A. Verek and Adansonii (Gum Senegal) in West Africa, A. nilotica and Seyal (Gum Arabic) in Nubia, A. arabica, spinosa, and ( Vachellid) Farne- siana in the East Indies, A. decurrens, mollissima, and affinis in Australia. The bark of most species of Acacia is very astringent, and many kinds are used for tanning in India; the pods of A. nilotica are used for the same purpose ; and the astringent substance called Catechu is obtained by extraction with water from the heart-wood of Acacia Catechu. Various species of Inya, Prosopis, &c. are very astringent. Some East-Indian Acacias yield valuable timber ; the legumes of A. concinna and the large CALYCIFLOR^:. 255 seeds of Entada Piirscetha contain a saponifying substance. Some kinds of Mimosa and Prosopis are said to have poisonous properties. Acacia varians, of Australia, has been called the Poison-tree. It is hardly neces- sary to add that a great number of plants from all these Suborders are cultivated for the sake of their beautiful flowers. form a very anomalous group of 3 or 4 species only, marked by the following characters : Trees with 2-3-pinnate leaves and thin deciduous stipules ; flowers irregular, 5-merous ; sepals and petals petaloid; stamens 8-10 on a disk in the tube of the calyx, the outer circle sometimes sterile ; anthers 1-celled ; ovary superior, stalked, 1-celled with 3 parietal many-ovuled placentas ; fruit a long 3-valved pod with the seeds in the middle of the valves ; seeds without perisperm. The species are natives of Arabia and the East Indies, and have generally been referred to the vicinity of the Leguminosse, principally on account of their perigynous irregular flowers, pinnate leaves, and pod-like fruits. The structure of the ovary removes them widely from LeguuiinosaB, on account of the parietal placentation, since, judging from Rosaceae, the occurrence of additional carpels in Leguminosae would be accompanied by an apo- carpous condition, or at least by axile placentas. Uiphaca and Ccesalpinia diyyna (Legiiminosaa) are in fact described as having 2 legumes ; but the monstrous forms of Gleditschia referred to by De Candolle are said to have 2 coalescent carpels. Hence Lindley places this Order in the neighbour- hood of Violaceae, and conceives that it approaches Polygalacese. Others place it between Capparids and Resedacese, to the" former of which orders it is certainly closely allied. The root of Moringa plerygosperma is pungent and aromatic, resembling Horse-radish. A gum like Traga- canth exudes from the bark. The seeds are the Ben-nuts ; and the oil of Ben was formerly highly esteemed for perfumery, and for lubricating watchwork, on account of its comparative freedom from easily-solidifying fatty ingredients. ROSACES. THE ROSE ORDER. Coli. Rosales, Benth. et Hook. Diagnosis. Herbs, shrubs, or trees usually with alternate, stipu- late leaves, regular bisexual or unisexual flowers ; numerous (rarely few) distinct stamens springing from the calyx ; carpels 1 or many, either quite distinct or coherent, and enclosed in the tube of the receptacle ; seeds (anatropous) 1 or few in each ovary, aperi- spermic ; embryo straight, with large and thick cotyledons ; leaves alternate, stipulate. Character. Thalamus convex, elongated, or concave, forming a tube (calyx- tube, receptacular tube). Calyx synsepalous, with 4-5 lobes, the odd lobe posterior, i. e. next the axis, when 5 ; sometimes with an epicalyx. Corolla : petals 5, distinct, emerging from the calyx, rarely absent. Stamens definite or indefinite, given off 256 SYSTEMATIC BOTJLNY. with the petals. Ovaries apocarpous, 1-2, or 5 or numerous, 1 -celled, sometimes combined together in the excavated receptacle (fig. 374) or tube of the calyx ; ovules 1 or few ; styles lateral (fig. 377) or terminal. Fruit : a drupe, an achene, or a dry or succulent etserio (figs. 375, 376), or a cynarrhodon or a pome (fig. 378) ; seeds 1 or more, aperispermic ; embryo straight. Fig. 375. Fig. 374. -v f* * ^ . 378< Pig. 374. Section of the flower of Rosa, showing the flower- tube enclosing the carpels. Fig. 375. Dry etaerio of Geum, with separate carpel in section. Fig. 376. Section of succulent etaerio of Rubus. Fig. 377. Ovary of Fragaria with lateral style. Fig. 378. Section of the pome of Mespilut. Fig. 379. Calyx of the Eo-e ; the numbers indicate the sequence of the sepals from without inwards, or from below upwards. Fig. 380. Transverse section of pome of Apple, showing the five carpels imbedded in the fleshy flower-tube. CALTCIFLOR.E. 257 This Order is commonly broken up into several smaller Orders, which we shall characterize here as Suborders. 1. CHEYSOBALANE^;. Trees or shrubs with free stipules ; car- pel 1, adherent more or less to one side of the calyx-tube ; ovules 2 ; style basilar ; fruit drupaceous ; seed erect ; radicle inferior. 2. DRTJPACE.E. Trees or shrubs with free stipules ; carpel 1, free ; style terminal ; fruit a drupe, not enclosed in the tube of the flower, which is deciduous ; seeds suspended. 3. POME^E. Trees or shrubs with free stipules ; carpels 1-5, more or less united together and with the sides of the flower-tube ; styles terminal ; fruit a pome, 1-5-celled or spuriously 10-celled, with a crustaceous core or bony stones (fig. 375) ; seeds ascending. 4. ROSE m. Shrubs or herbs with adnate stipules ; carpels free from the flower-tube, 1 or many, 1-celled, sometimes cohering; styles lateral; fruit usually formed of an assemblage of dry achenes, small drupes, or dehiscent several-seeded follicles ; sead suspended, rarely ascending ; radicle superior. 5. SANGUISOBB^. Herbs or undershrubs, apetalous, often diclinous ; carpel 1, enclosed in the flower-tube; style from the summit or base ; fruit an achene, surrounded by the persistent tube of the flower; seed 1, suspended or ascending. ILLUSTRATIVE GENERA. I. CHRYSOBALANEJE. Chrywbalanus, L. II. AMYGDALEJE, or DRU- PACEJE. Primus, L. III. POMEJE. Pyrus, Lindl. IV. ROSEJE. 1. Ro- SIDJE. Flower-tube fleshy, enclosing the achenes : .Rosa, Tournef. 2. POTENTILLIDJE. Flower-tube herbaceous ; fruit an etaerio : Rubus, L. ; Frngaria, L. ; Poten+illa, L. 3. SPIR^ELD^E. Flower-tube herbaceous; fruit a ring of follicles ; seeds not winged : Spircea, L. 4. QUILLAIJE. Flower-tube herbaceous; fruit capsular; seed winged: Quillaia, Mol. 5. NEURADEJE. Flower-tube adhering to a ring of 10 carpels ; seed pen- dulous : Neurada, L. V. SANGUISORBE^E. Alchemilla, Tournef. ; Po- terinm, L. Affinities, &c. Typical formula |S 6 P 5 Aoo G l-oo . Closely allied to Legumiiiosae ; and, indeed, the only constant point of difference consists in the position of the odd sepal posterior in Rosaceae, anterior in Legumi- nosaa. The Chri/sobalanea may be regarded as forming a link between the Leguminosae and the Drupacece, touching that Order especially in its drupaceous genera and those with a laterally adherent calyx. _ The J)ru- pacece have some affinity also to Anacardiaceae ; Pomece again connects the Order with the epigynous families, especially Myrtacese. through Punica. Rosece resemble Pomece in many respects, but their affinities go out in other directions; Calycanthacese should, perhaps, scarcely be sepa- rated from them. The Spirceidcc very much resemble some Saxifragaceae (distinguishable by their perispermic seeds) ; and the Potentillidce remind us of the Ranunculaceae in the fruit and the adnate stipules, which some- times closely approach the dilated base of the petiole of Ranunculus, &c. ; but Ranunculaceae have perisperm and usually hypogynous stamens, though the difference in some genera between hypogynous and perigynous po&i- 8 258 SYSTEMATIC BOTANY. tion of the stamens is almost imperceptible. Sanc/uisorbefS are merely a degraded form of Rosece, where the petals and one or other set of essential organs are abortive in each flower. Distribution. There are about a thousand species. The Chrysobalancce are chiefly found in tropical America and Africa, more rarely in Asia : the Drupaccce are mostly natives of the temperate parts of the Northern Hemisphere, but are widely spread in cultivation ; the Pomece also belong to the Northern Hemisphere ; most of the Rosece and Sanyuisorbece belong to temperate and cold climates, but a few are tropical. Qualities and Uses. The succulent fruits of many of the plants form the most striking feature of this Order. Various parts of the structure, but especially the seeds, yield much hydrocyanic acid in the Suborders Dru- pacece and Pomece. (The bark and root of almost all are bitter and astrin- gent, owing to the presence of tannin. Drupacece commonly contain a gum (resembling Gum Arabic) in the sap. This gum is the result of a pathological change in the tissues. Most of the Chrysobalanece have stone-fruits ; that of C. Icaco (West Indies) is eaten under the name of Cocoa-plum. Among the Drupacece we have the fruits : Almond (Amyydalus com- munis) ; the Peach and Nectarine (A.persica) ; the Plum in all its varieties, such as Greengages, Bullaces, Damsons, &c. (Prunus domestica, spinosa, and varieties) ; the Apricot (Primus armeniaca) j the Cherry (Cerasus avium, &c.). Cerasus Lauro-cerasus is the common " Laurel " or Cherry- laurel of our shrubberies, C. lusitanica the Portugal Laurel. Many of these plants contain a considerable quantity of amygdaline, causing the formation of prussic acid when they are bruised. This gives to the seeds of the Bitter variety of Almond, and to all other seeds in this Suborder, a poisonous property, which exists also to a great extent in the leaves and shoots of the Cherry-laurel, the flowers of the Almond, Peach, &c. The seeds also contain a fixed oil, which may be obtained by expression ; and that of the Sweet variety of the Almond is devoid o'f amyc/daline, and thus harmless. The bark of Prunus serotina is used medicinally in inter- mittent fevers. Pomece have succulent fruits, such as the Apple, Pear (Pyrus Mains and communis), Quince (Cydonia vttlgaris), Medlar (Mes- pilus ffermanica), &c., which have been brought into the edible condition by cultivation ; when wild, they are mostly austere, like those of the Hawthorn (Cratceyus), of the Mountain Ash (Pyrus Aucuparia), &c. The seeds contain amygdaliue, and therefore yield prussic acid ; as do also the flowers, bark, and root of the Mountain Ash. Quince-seeds are valuable for the mucilage they contain. The Rosece yield edible fruits, such as the Raspberry and Blackberry (Rubus idceus and fruticosus) and the Strawberry (Fray aria elatior, vesta, &c.). The petals of Roses yield the essential oil called Otto or Attar of Roses. Kousso (Bray era cinthelmintica) is used as a vermifuge. Most of the Rosece have astringent bark and roots ; some are unwholesome. San- yuisorbece have astringent properties similar to Rosece. Quittaice contain 'in their bark a saponaceous principle, which renders them useful for cleaning silk fabrics. CALYCANTHACE^ form a small Order, consisting of shrubs with opposite entire leaves, without stipules ; sepals and petals similar and indefinite ; CALYCIFLOR^. 259 anthers adnate and extrorse ; cotyledons convolute ; otherwise like Ro- saceae. The species are natives of North America and Japan, and are chieliy remarkable for the peculiarity of their floral envelopes, the coloured bracts of the peduncle passing insensibly or undistinguishably into the calyx, and this into the corolla ; the segments of both spring from a fleshy tube supporting the stamens and surrounding the car- pels ; convoluted cotyledons are only found in one Rosaceous plant, Chamesmeles (Pomece), but are characteristic of Combretaceae. Calycanths stand between the Rosaceae and the Myrtaceae, and have, perhaps, a distant resemblance to Magnoliaceas, like that of Rosaceae to Ranun- culaceae. Bailloii places them with Monimiads. Their wood is curious, the stem having four false woody axes around the real axis, giving the stem a quadrangular character. The chief property is fragrance of the blossom. Clmnonanthus produces yellow fragrant flowers upon the leaf- less branches during the winter. Calycanthus floridm has an aromatic bark. MYRTACE^E. THE MYRTLE ORDER. Coh. Myrtales, Benth. et Hook. Diagnosis. Trees or shrubs with leaves opposite or alternate, entire, usually dotted, and with a submarginal vein; flowers usually axillary, regular, polypetalous or apetalous ; calyx ad- herent, 4-5-clefb, valvate or imbricate, sometimes falling off like a cap ; petals 4-5, imbricated ; stamens 8-10 or numerous, rarely 4-5, distinct or polyadelphous ; ovary 1-, 2-, 4-, 5-, or 6-celled; style and stigma simple; placentas axile ; seeds usually indefinite, aperispermic ; fruit dry or succulent, dehiscent or indehiscent. Illustrative Genera: Tribe 1. LEPTOSPERME.E. Fruit capsular. Melateuca, L. ; Eucalyptus, Herit. ; Metrosideros, R. Br. ; Hceckia, L. Tribe 2. MYRTE.E. .Fruit baccate. Panica, L. ; Psidium, L. ; Myrtus, Tournef . ; Eugenia, Michel. Affinities, & vertical sec- tion, showing the erect seed.) ILLUSTRATIVE GENERA. By Benth ( am the Composites are divided into thirteeen tribes : I. Vernoniese. II. Eupatoriese. III. Asteroideae. IV. Inuloidese. V. Ileliantlioideas. VI. Helenioidese. VII. Anthemideae. VIII. Senecio- nideae. IX. Calenduleaa. X. Arctotidese. XI. Cynaroidea?. XII. Mutisiacere. XIII. Cichoracese. These tribes are founded upon the imi- or bisexual character of the florets in each head, the form of the florets (tubular, ligulate, &c.), the form of the anthers and of the projections from their base and apex respectively, the form of the style and stigmas, the nature of the pappus, &c. The fol- lowing- genera may be taken as representatives of the above tribes : I. Vernonia. II. Eupatorium. III. Aster. IV. Inula. V. Helian- thus. VI. Tac/etes. VII. Anthemis. VIII. Scnecio. IX. Calendula. X. Arctotis. XL Carduus. XII. Mutisia. XIII. Taraxacum. Affinities, &c. This Order, which is the most numerous, and, by some authors, regarded as the most perfect in the Vegetable Kingdom, is like- wise very natural, its distinguishing features being very evident in almost every genus. From its nearest allies, Dipsaceae and Calyceraceae, it may be distinguished by the condition of the anthers and the ovule. The syngenesious condition, and, in some measure, the general structure of the florets, ligulate and tubular, indicate a near relation also to Lobeliacese and Campanulaceae, wherein, however, the flowers are not only large and scattered, but the ovaries have more than one cell, with many seeds in each cell. ^_^ _ ^_^ The floraHormula is | S5? P5 A 5 G2, but the nature of the calyx and pappus is undetermined. Two different views are held as to the nature of the pappus. Some (as Lund, Treub, Bucheuau) look on it as truly a modified calyx : Warming considers it in the light of trichomes or hairs having no definite position or order. Hofmeister regards the pappus of Composites, Valerianacese, and Dipsaceee as a whorl of leafy u2 292 SYSTEMATIC BOTANY. formations, and considers it probable that eacli hair is the representative of a leaf. In the development, however, the corolla precedes the calyx, which is often represented by a mere rim, so as to render it doubtful whether a true calyx-limb really exists. The subdivisions of this Order are differently given by different authors. The most recent revision is that of Bentham above cited. The Orders of the Linnean Class Syngenesia correspond to Compositee. Tubuliflorae, as above given, include the Corymbiferae of some authors, in which the style of the perfect flowers is not swollen below the stigma, and the Cynareae, where the outer florets are often neuter and the style is swollen below the stigmas. The tribes of the Compositse established by De Can- dolle depend on the condition of the style and its stigmatic lobes. The characters of the genera are chiefly derived from the conditions of the involucre, the cypselous fruit, and the pappus. Distribution. The species are more numerous than those of any other family, more than ten thousand being known, and are universally distri- buted, forming one eighth of the Phanerogamia of Central Europe ; the Tubuliflorce are most abundant in hot climates, the Cichoracece in cold. The Labiatiflorce belong almost entirely to extratropical South America. In the northern hemisphere the Compositse are all herbaceous ; in South America and some other parts of the southern hemisphere they are some- times shrubby. Fossil Composites are first found in the Upper Miocene beds (Saporta). Qualities and Uses. The plants of this Order are not generally charac- terized by any very powerful properties: bitterness is the prevailing- quality, accompanied by aromatic secretions in the Corymbiferce, and by a special lactescent juice in the Cichoracece, which often contains a more or less active narcotic principle. Among Corymbiferce may be noticed a number of genera possessing considerable importance. The Artemisice, or Wormwoods, are numerous ; A. Absinthium and pontica are Wormwoods proper, and with some other species are used not only as anthelmintics, as their name indicates, but for preparing the bitter liqueurs called Absinthe or Vermuth ; A. Dracuncvlus is the Tarragon, the leaves of which are used in salads and pickles ; A. Abrotanum is Garden Southernwood, used also for its bitter flavour. Most of the other species have similar properties; the flower-heads of A. Contra, Sieberi, pauciflora, Vahliana, &c. are known on the Continent, under the name of Semen Cinse or Semen Contra, as powerful vermifuges. A. chinensis furnishes Moxa. Anthemis nobilis, the Camomile, Matricaria Chamomilla, and Pyrethrum Parthenmm are valued for aromatic bitter and tonic properties ; the species of Achillea are astringent, or in some cases pungent, which is still more the case with Anacyclus Pyrethrum, called Pellitory of Spain, and A. qfficinarum, the dried roots of which provoke an active flow of saliva, and are used as a remedy for toothache : in a fresh state these roots are acrid ; and this is still more the case with Maruta fastida. Arnica montana, a plant of the mountains of Central Europe, is narcotic-acrid and poisonous, except in small doses ; its tincture has a powerful influence in exciting the circulation beneath the skin with- out producing vesication. Dorom'cum Pardalianches is said to have similar properties, as also some species of Inula ; Inula Helenium, however, is merely aromatic and tonic ; it is known under the name of Elecampane. COKOLLIFLOB.-*;. 293 Some species of Eupatorium, including our native E. cannabiniim, are emetic and purgative ; E. Ayapana (Brazil) has a reputation as a local and internal application for snake-bites. Matico is said to be obtained from E. f/lutinosum, though most of it is the produce of Artantlie donyata, a Piperaceous plant ; its leaves are used as a styptic. The seeds of some of the Corymbifercs contain much fixed oil. The seeds of the Sunflower (Helianthus annuus) are well known on this account; and Madia sativa (Chili) has become an object of cultivation in France and Germany for the sake of the oil expressed from its seeds, its " oil-cake " being also valuable for cattle. The esculent tubers called Jerusalem or Girasole Artichokes are furnished by Helianthm tuberosus ; the analogous tubers of the Dahlia (Dahlia variabilis) are not available in this way on account of a strong and unpleasant flavour which exists in them. Tussilago Farfara, or Coltsfoot, which is mucilaginous and bitter, was formerly in repute for affections of the chest. The Cynarea, or thistle-like Composite, are equally varied in the concentration of their qualities. The root of Carlina acaulis is said to be a violent purgative, and that of C. gummifera is known as an anthelmintic. The Burdock (Arctium Lappa), the Marigold (Calendula officinalis}, Ori- taurea Calcitrapa, and other allied plants were formerly esteemed as febri- fuges, diuretics, and "alteratives, but have gone out of use. The Costus, celebrated by the ancients for its virtues, is supposed to be the root of Aucklandia costus (Cashmere). Carthamus tinctorius, Safflower, is used in dyeing and in the manufacture of true rouge; the flowers of Calendula officinalis are used to adulterate Saffron. Serratula tinctoria is also used in dyeing yellow and green. The Globe Artichoke is the fleshy receptacle, with its bracts, of Cynara Scolymus ; Cardoons are the blanched stems and petioles of Cynara Cardunculus. The Labiatiflora are sometimes aromatic, bitter, or mucilaginous. The leaves of Printzia aromatica are used as a Tea at the Cape of Good Hope ; those of Anandria discoidea are used by the Chinese as the Coltsfoot is in Europe. The Cichoracea include several plants of note : the different kinds of Lettuce, Lactuca virosa, Scariola, sativa (the Garden Lettuce), contain a milky juice which has narcotic properties ; when evaporated to dryness it forms a kind of gum, called by druggists Lactucarium, which is occasion- ally used as a sedative. The Garden Lettuce loses much of its bitterness, and, at the same time, of its narcotic properties, in cultivation. The Dandelion, Leontodon Taraxacum (or Taraxacum Dens Leonis)^ has also a milky juice, which is valued for its medicinal properties as a diuretic and alterative, with some sedative qualities ; its roots, and still more those of Chicory. or Succory (Cichorium Intybus), are used, roasted, to adulterate coffee. Besides the Lettuce we have other esculent vegetables in this Suborder : Cichorium Endivium furnishes the Salad Endive (blanched by exclusion of light) ; Scorzonera is the root of Scorzonera hispanica, other species of which are used in like manner in different countries ; Salsafy is the root of Trayopoyon parvifolius, or Goafs-beard. The Compositae include a vast number of cultivated plants. The Dahlia (D. variabilis}, the Chrysanthemum (Pyrethrum sinense, indicum), the Cinerarias (Senecio cruenta, Tussilaginis, Heritieri), the China Aster ( Callistemma hortense) are florist's flowers remarkable for the number and beauty of their varieties. The Everlasting flowers, or Immortelles, are 294 SYSTEMATIC BOTANY. mostly species of GnapJialium, together with Helichrysum, Aphelexis, &c. Our native Thistles are species of Carduus, Onopordum, &c. LOBELIACE^E are herbs or shrubs with a milky juice, alternate leaves, and scattered flowers ; corolla irregular, epigynous, sympetalous', split down to the base on one side ; the 5 stamens free from the corolla and united into a tube, often by their filaments, and always by their anthers; ovary inferior, 1-3-celle'd; style 1 ; stigma 2-lipped, surrounded by a fringe of hairs ; seeds numerous, perispermic. Illustrative Genera : Lobelia, L. ; Siphocampylus, Pohl. Affinities, &c. The relations of this Order to Composite are close, as is seen when we compare the flowers with ligulate florets of the Cichoracea : the structure of the ovary, however, as well as of the inflorescence, divides them. With Cainpanulaceae, under which order they are included as a tribe by Bentham and Hooker, they are connected through the tubular florets of Compositae, which resemble the flowers of Campanulaceae, except in the structure of the ovary, which brings the Campanulacese still nearer to Lobeliaceae. The fringe round the stigma is analogous to the hairs of the style of Campanulaceae, and perhaps also to the indusium of Goode- niacese. Some Lobeliaceae have their petals distinct, and Monopsis has the flower nearly regular. Distribution. A rather large Order, the members of which are chiefly distributed throughout tropical and subtropical regions. Qualities and Uses. The milky juice is aero-narcotic; the species of Lobelia are more or less poisonous, producing effects analogous to those of Tobacco. Lobelia inflata is used in small doses for spasmodic asthma ; it acts sometimes as an emetic, but produces great depression of the pulse, perspiration, and, in large doses, death. Most of the species are acrid when fresh ; Z. urens produces vesication of the skin. Tupa Feuillei (Chili) yields a violent poison. Isotoma lonyiflora is vesicatory, and, taken in- ternally. produces death from violent and uncontrollable purging. The milky juices contain Caoutchouc. Many species of Lobelia and Siphocam- pylus are cultivated for their showy flowers. GOODENIACE^E consitute an Order of plants allied to the Lobeliaceae, the Stylidiaceae, and the Campanulaceae ; but especially distinguished by the remarkable structure of the upper part of the style, which is expanded into a kind of cup or purse, concealing within it the stigmatic surface, and closing over the pollen after fertilization. Most of the Goodeniaceae are Australian and Polynesian ; a Sccevola occurs in North-western India and in Africa ; another genus, Selliera, is South-American. Their properties are unimportant. Leschenaultia formosa, C(8t*ulea, and other species are cultivated on account of the beauty of their flowers. BRUNONIACE^, consisting of two species ofBnmonia, Australian plants, agree with Goodeniaceae in the structure of the style, but are sometimes separated from them on account of the superior position of the ovary. Their capitulous inflorescence approaches that of Conipositae. They have no known properties. constitute a small Order of plants related to the Goode- niaceae and the Campanulaceae, but are distinguished by and remarkable COEOLLIFLOK^:. 295 for the gynandrous structure of the flowers, the filaments being 1 adherent to the style into a column surmounted by the anthers which overlie the stigma. * This column exhibits the irritability met with here and there in Flowering Plants : in Stylidium it hangs over on one side of the flower ; but when touched it rises tip and springs over to the opposite side, at the same time opening its anthers and scattering the pollen. The Stylidia are chiefly from Australia; a few others are scattered in the East Indies; the Forsierce belong to New Zealand and the Straits of Magellan. They have no known properties. CAMPANULACEJE. BELL-FLOWEBS. Coh. Campanules, Benlh. et Hook. Diagnosis. Herbs with a milky juice, alternate leaves, and mostly scattered flowers ; calyx adherent to the ovary ; corolla regular, epigynous, bell-shaped, valvate in aestivation ; stamens 5, free from the corolla, mostly distinct or coherent just below the base of the distinct anthers ; ovary 2-5 -celled ; style 1, hairy ; stigma simple or lobed ; capsule many-seeded, dehiscent by lateral orifices or valves at the top ; seeds with fleshy perisperm. Illus- trative Grenera : Jasione, L. ; Campanula, L. Affinities, &c. The Campanulaceae are divided by Bentham and Hooker into three tribes : 1. Lobeliees, here treated as a distinct Order, and having irregular flowers and syngeuesious anthers; 2. Cyphiece, with irregular flowers and free anthers ; and 3. Campanulece, with regular flowers and usually free anthers. They have many points of agreement with the Compositse, the flowers resembling the tubular florets of that Order in the corolla, inferior position of the ovary, and number and position of the stamens ; but the anthers are distinct or only united at the base, and the ovary is more than 1 -celled and contains many seeds ; in Jasione and Phyteuma the flowers are in capitula, almost like those of Composite. They are only separated from Lobeliaceae by the regularity of their flowers, the globular (not elliptical) pollen-grains, and the peculiar hairs of the style ; which points of structure likewise separate them from Goo- deniacese and Stylidiaceae. On the other hand they approach Vacciniece, from which they differ in the number of the stamens and their porous dehiscence, the style, and the habit. In Cyclocodon the tube of the corolla is adherent' to 'the ovary (superior), while the calyx is inferior! Distribution. A large Order, the members of which belong mostly to the temperate parts of the Northern hemisphere. Qualities and Uses. The milky juice has properties analogous to that of the Compositae, and is sometimes rather acrid; but the young roots and shoots, especially when cultivated, are often edible ; Kampions are the roots of Campanula Rapunculus ; Specularia Speculum and other species have been used in salads. The Campanulas, commonly known as Canter- bury Bells, Hair-bells, &c., are numerous in cultivation; and other genera have also handsome flowers. 296 SYSTEMATIC BOTANY. Series 2. Su PEEVE. Ovary usually superior (inferior in Vacciniece). EKICACEJE. THE HEATH OEDEE. Coh. Ericales, Benth. et Hook. Diagnosis. Shrubs or sometimes herbs, with regular or nearly regular flowers ; corolla gamo- or poly- petalous, hypogynous or epigynous ( Vac- Fig. 404. Fig. 405. ciniece) stamens as many or twice as many as the petals of the 4-5-lobed or 4-5-petalous corolla, free from the corolla, hypogynous or epigynous ; anthers 2- celled, commonly with appendages, and opening bv terminal chinks or pores (tigs. 404, "405) ; style 1 ; ovary 3-10- celled ; seeds small, anatropous ; embryo small or minute, in fleshy perisperm. Fig. 403. Fig. 403. Flower of Erica. Fig. 404. Stamen of Erica. Fig. 405. Stamen of Vaccinium. The Ericaceae are divisible into four very distinct Suborders, which are some- times ranked as Orders : 1. VACCINIECE. Shrubby, or more or less woody herbs, with an adherent calyx, sympetalous epigynous corolla, epigynous stamens, 2-parted anthers opening by pores, containing 4-nate pollen-grains ; the inferior ovary becoming a berry surmounted by the teeth of the calyx. 2. EEICINE^E. Shrubs or small trees, with a free calyx ; a sympetalous or polypetalous corolla springing with the stamens from the receptacle ; anthers opening by pores. 3. PYEOLE^E. Woody herbs with evergreen foliage ; calyx free ; corolla of 5 distinct hypogynous petals ; stamens hypogynous ; anthers porous ; seeds with a loose cellular testa and minute nucleus. 4. MONO- TEOPE^E. Fleshy herbs with scale-like leaves, destitute of green colour ; calyx free ; corolla syrn- or dialypetalous ; stamens hypo- gynous ; pollen simple. ILLUSTRATIVE GENERA. Suborder I. VACCINIECE. Oxycoccus, Tournef. } Vaccinium, L. Suborder II. ERICINE^E. Tribe 1. ARBUTEJE. Corolla deciduous. Fruit succulent. Evergreen shrubs. Arbutus, Tourn. Tribe 2. ANDROMEDE^. Corolla deciduous. Capsule loculicidal. Shrubs with persistent leaves. Buds usually scaly. Andromeda, L. Tribe 3. ERICE^:. Corolla persistent, often 4-merous. Fruit not cap- sular. Buds not scaly. Erica, L. COKOLLIFLOB^. 297 Tribe 4. HHODORE^. Corolla deciduous. Fruit capsular, sepiicidal. Buds scaly, cone-like. Azalea, L. ; Rhododendron, L. ; Ledum, L. Suborder III. PYBOLEJS. Chimaphila, Pursh ; Pyrola, Tourncf. Suborder IV. MONOTBOPEJE. Monotropa, Nutt. ; Schweinitzia, Ell. j Pterospora, Nutt. Affinities, &c. The general floral formula is S5 P5 A 5 + 5 G5, but in Vocciniefe it is | S~5 P~5 A 5+6 G 5. The Suborders are connected by the general plan of structure; but the details are subject to wide variation, not only including sympetalous and dialypetalous conditions, but even hypogynous and epigynous. By many authors these subdivisions are ranked as distinct Orders. The Vacciniece, with their inferior ovary, stand, if separated, among the epigynous Orders, near Campanulaceae or Cinchonaceas ; consequently they form a connecting link between the Oalyciflorals and Corollifiorals, indicating the artificiality of this division; they even appear related to the perigynous Calyciflorals by Escallonieee in Saxifragacese. The JEricinece differ from the Vacciniece principally in the superior ovary and hypogynous corolla ; and the stamens are here nearly if not quite hypogyuous, which, with the many-celled ovary, divid'es them from Gentianacese and allied Orders. The Ericineas are nearly allied to the Epacridacese ; but the latter have 1 -celled anthers. The Pyrolece have the sepals and petals more or less distinct, are more herbaceous in habit than the foregoing, and their seeds are remarkably different ; P. aphylla, a plant devoid of green colour, and with leaf-scales in place of leaves, connects this Suborder with Monotropece, which, how- ever, differ in the dehiscence of the anthers, and in having the minute embryo at the apex instead of at the base of the fleshy perisperm. Some doubt exists whether the last Suborder are really parasitical plants : they grow among the fibrils of the roots of trees, and have all the appearance of parasites, but may live on decaying vegetable matter. In habit they resemble Orobanchaceae ; but this is not a sign of affinity. Distribution. A large Order, the members of which are generally diffused in temperate climates over heathy and boggy tracts, in subalpine and alpine localities, all over the world the Rhododendra especially in India, the Befarice in South America, and the Heaths at the Cape. Qualities and Uses. The general character is astringency. The fruits of various Vacciniece and Ericece are edible as those ofOxucoccuspalustris&nd. O. macrocarpa (the European and North- American Cranberries), Vacci- nium Myrtittus (the Bilberry), V. Vitis-Idaa (the Red Whortleberry), and V.uliginosum (the Black Whortleberry \Gaultheria procumbens,G. hispida (Tasmania) , &c. But others are dangerous or even narcotic poisons ; and this extends to the foliage of such kinds, especially species of Rhodo- dendron, Azalea, Andromeda, Kalmia, &c. Uva-Ursi leaves (Arctostaphy- los Uva- Ursi) are mixed with Tobacco by the North- American Indians, and are esteemed as astringents ; those of some Pyrolece, as Cliirnaphila umbellata, American Wintergreen, are used as diuretics. Oil of Winter- green, known as an antispasmodic agent, and used in perfumery, is obtained from the fruit of Gaidtheria procumbens. A vast number of species of Erica, Rhododendron, Azalea, &c. ; with numerous varieties and 298 SYSTEMATIC BOTANY. hybrids, are objects of cultivation on account of the peculiarity and beauty of their flowers. They especially constitute what are called " American Plants" by gardeners, the American Rhododendra, Azalece, and Kalmife, &c. being those which first strongly occupied the attention of florists. Some of the East-Indian Rhododendrons are epiphytes. EPACKIDAOE^E are closely related to Ericaceae, but are distinguished by the one-celled anthers opening by a chink ; the filaments are also commonly adherent to the corolla. The Order is commonly divided into two Tribes : 1. Styphelieae, with one ovule in each cell of the ovary, and fleshy fruits ; and 2. Epacreee, with numerous ovules in each cell of the ovary, and capsular fruit. They are peculiar to Australia, the Indian archipelago, and the South-Sea Islands, occurring in great abundance, in the same way as the Ericece do at the Cape of Good Hope. They do not appear to possess any active properties : many of them bear succulent berries ; and some of them are eaten, as those of Lissanthe sapida, Astro- loma humifusum, the Tasmaniau Cranberry, &c. Many of the Epacri- daceae are in cultivation on account of the beauty of their flowers. PLANTAGINACE^E are chiefly herbs with undeveloped stems and tufts of leaves spreading more or less on the ground ; flowers spiked, regular, 4-merous, the 4 stamens attached to the tube of the hypogynous dry and membranous sympetalous corolla, alternating with its lobes ; the filaments long and slender, and the anthers versatile ; ovary simple, but spuriously 2- or 4- celled by temporary adherence of the angles of the free central placenta to the walls ; ovules 1, 2, or numerous, peltate ; style and stigma simple, the latter rarely cleft ; capsule membranous, dehiscence circumscissile ; seeds 1, 2, or many, perispermic ; the testa mucilaginous. Illustrative Genera : LfttoreHa, L. ; Plantago, L. Affinities, &o. This Order appears to find its nearest relatives in Pluin- baginaceee and Primulaceas, from which, however, the position of the stamens, alternating with the lobes of the corolla, distinguishes it, in addition to other characters noticed under those Orders. The affinity to Amaranthaceae and Chenopodiaceae does not appear well made out. Baron von Mueller suggests an affinity with Loganiads. In Lit- toretta there is a tendency to abortion in one or other set of essential organs. Distribution. A not very extensive group, the species of which are generally diffused, but most abundant in temperate climates. Qualities and Uses. The foliage is slightly bitter and astringent. The seeds of many species ofPlantago, such as P. Psyllium^arenaria^ Cynops,fcc., were much used formerly on the Continent, under the name of Semen Psyllii and S. Pulicariae, or Flea-seed, for making mucilaginous drinks like those prepared from linseed. The seeds called Ispaghulse are the product of Plantayo decumbens j the spikes of the fruit of P. major are much gathered in the green state under the name of Plantain, for feeding caged birds. P. major, minor, and lanceolata, called Plantains or Road-weeds, are among the commonest of our weeds on road-sides, in meadows, and all undisturbed ground where the soil is not very light. They are sometimes grown for sheep food. COBOLLIFLOB^E. 299 PLUMB A GIN AC EJE (THE THRIFT OBDEB) consists of maritime or mountain herbs or under-shrubs, often with undeveloped stems and clustered leaves j flowers regular, 5-merous, with a plaited calyx j the 5 stamens superposed to the separate petals or the lobes of the sym- petalous corolla ; the free ovary 1-celled, with a solitary ovule hanging trom a long funiculus which arises from the base of the cell ; styles 5, rarely 3 or 4 ; fruit either utricular or dehiscent by valves above ; seed with a simple testa and little pensperm. Illustrative Genera : Statice, L. ; Plumbago, Tournef. Affinities, &c. This Order is strongly characterized by the peculiar at- tachment of its ovule : this, with the numerous styles, separates it from the Priinulocese, which it approaches in the position of the stamens and some other points ; the same characters, with the position of the stamens, distin- guish it from Plantaginacese ; and these marks, with the plaited calyx, isolate it from all the other Corollitioral Orders, among which it claims a place in spite of the occasionally dialypetalous or even apetalous con- dition. Distribution. A rather large group ; some kinds are found all over the world on the sea-shore ; others are more local in similar habitats, in salt-marshes and in saline steppes, while others, again, belong to alpine regions. Qualities and Uses. The properties are either bitter and astringent, or acrid and caustic. The roots of Statice caruliniana are powerfully astrin- gent ; those of Plumbago europcea, zeylanica, scandens, and others are very active blistering-agents when fresh ; that of P. europcea is used dried as a remedy for toothache. P. toxicaria is said to furnish a poison in Mozambique. The Garden Thrift (Armeria vulgaris), commonly used for edging, like Box, is said to be an active diuretic : the dried flowers are used for this purpose. Small doses of the root of Plumbago europcea are said to act as an emetic. The flowers of many of the Plumbaginaceae, especially species of Statice, are very handsome, and many are cultivated on this account. PEIMULACE^. THE PEIMEOSE OEDEE. Coh. Priinulales, Benth. et Hook. Diagnosis. Herbs with opposite or alternate simple leaves and regular, perfect flowers ; the stamens as many as the lobes of the sympetalous (rarely dialypetalous) hypogynous corolla, and super- posed to them in the tube ; ovary 1-celled, with a free central placenta bearing numerous perispermic seeds, a simple style, and a capitate stigma. Character. Thalamus flat or slightly convex. Calyx 5- or rarely 4-cleft, free or half-adherent, regular, persistent. Corolla hypogynous, sym- petalous, and the limb regularly 5-, or rarely 4-clei't ; or more 300 SYSTEMATIC BOTANY. rarely composed of separate petals, or absent. Stamens equal in number to the petals or lobes of the corolla and adherent to them ; or in apetalous flowers hypogynous and alternating with the teeth of the calyx. Ovary 1-celled, with a free central pla- centa bearing many ovules ; style single ; stigma capitate. Fruit : a capsule opening by valves, more rarely circumscissile (fig. 406), many-seeded ; seeds peltate ; the embryo in fleshy perisperm. Fig. 407. Fig. 406. Capsule of Anagallis opening by circumscissile dehiscence. a 6 Polyanthus : a, stamens exserted, style included; 5. style exserted, stamens included. (Seen in section.) ILLUSTRATIVE GENERA. Tribe 1. PRIMULE^EJ. Ovary free ; capsule valvular; hilum ventral. Primula, L. Tribe 2. ANAGALLTDEJE. Ovary free ; capsule opening transversely ; hilum ventral. Anagallis, Tournefort. Tribe 3. HOTTONIE^E. Ovary free ; capsule valvular ; hilum basilar. Aquatics. Hottonia. Tribe 4. SAMOLEJE. Ovary semi-inferior; capsule valvular; hilum basilar. Samolus, L. Affinities, &c. This is an Order which strongly attracts the attention of Structural Botanists on account of the peculiarities and anomalies which it presents. It is one of those in which the free central placenta is most distinctly seen, forming an exception to the very general rule of the placentas arising from the margins of the carpels. It seems to be truly axial in most cases, but in some monstrosities an appearance is presented as though the placentiferous lines were detached from the edges and surfaces of the carpels and reunited into a central column. Tn the next place the position of its stamens opposite or superposed to the petals is an exception to the rule of alternation of the organs of successive floral whorls, explained by supposing an intermediate whorl of stamens to be suppressed (in favour of which may be cited the condition of Samolus, Lysimachia ciliata, and others, where five teeth, which may be abortive stamens, alternate with the lobes of the corolla), or by the hypothesis COEOLLIFLOE^:. 301 of chorisis, according to which the stamens are outgrowths from the petals. On the other hand, it has been urged that the petals are out- growths from the stamens and are not autonomous organs. In Samolus we have the calyx partially adherent to the ovary. In some foreign genera the petals are either nearly or quite distinct. In Trientalis europce.a the lobes of the calyx, corolla, and the number of stamens vaiy from 5 to 9. In Glaux the corolla is absent, and the calyx coloured. The ordinary floral formula would be S ^ G5 , that of Samolus | S5P~5 A5 + 5G5. The relations to Plumbaginaceas are very close, both in the structure and the habit of many kinds, as between Androsace and some Primula) and Ar- meria, &c. ; but the solitary ovule of that family is a distinctive character. The Primulacese are still nearer to the exotic Order Myrsinaceae as regards the structure of the flowers ; but those are trees or shrubs with berrv-like fruits, and have minor characters of distinction noticed under that Order. They approach Solanaceae in habit, but not in structure. Distribution. A considerable family, the species of which are chiefly found in temperate and cold parts of the Northern hemisphere, in alpine regions or on the sea-shore when in lower latitudes. Qualities and Uses. The Cowslip (Primula veris) and other species appear to possess sedative properties. The Soldanellce are slightly purga- tive. The Cyclamens have a fleshy tuber which is more or less acrid ; and Cyclamen, europceum is said to be a drastic purgative. The most re- markable quality is perhaps the beauty of the flowers, for which a great number are cultivated, especially species of Primula, which includes the Cowslip, the Primrose proper (P. vulgaris], the Polyanthus, a garden variety of this, the Oxlip (P. elatior), the Auricula (P. Auricula, from the Alps), the Chinese Primrose (P. prcenitens], the Japan Primrose (P. faponica), &c. Many dwarf species of Primula and Androsace are "alpine plants," as is also Soldanella. Glaux and Samolus belong to salt-marshes; Hottonia to freshwater brooks, having feathery submerged leaves; the Lysimachice mostly grow in wet places. Many of the genera are repre- sented in our native flora ; while Androsace, Dodecatheon, and Soldanella, which are mostly alpine plants, are commonly cultivated. MYRSINACEJE are so closely related to Primulaceae in the structure of the flowers that no absolute character of distinction can be drawn there- from, since the imbedding of the ovules in the placenta, general here, occurs in several Primulaceous genera, for example in Anagallis. But the Myrsinaceae are of shrubby or tree-like habit, and their fruit is fleshy. They belong chiefly to the islands of the Southern hemisphere ; and some of them are cultivated in this country as evergreen shrubs requiring pro- tection in winter. The seeds of some species of Theophrasta and Myrsine are nutritious ; and the berries of some plants of the Order are edible, although others are said to be cathartic. include a genus of plants growing on sea-shores in the tropics, and rooting from the seed-vessels like Rhizophoraceae, and con- sidered to form a distinct Order by some writers. JEyiceras differs from 302 SYSTEMATIC BOTANY. Myrsinaceae chiefly in having aperispermic seeds, a follicular fruit, and transverse dehiscence of the anthers. SAPOTACEvE are trees or shrubs, mostly with a milky juice ; leaves alternate, simple and entire (leathery and often rusty-downy beneath) : flowers small, regular and perfect, usually in axillary clusters ; calyx free and persistent ; the fertile stamens commonly as many as the lobes of the short hypogynous corolla, and opposite to *hem, attached to the tube along with one or more rows of appendages and scales or sterile stamens ; anthers extrorse ; ovary 4-12-celled, with a single anatropous ovule in each cell ; seeds large, usually perispermic. Illustrative Genera : Chryso- phyllum, L. ; Isonandra, Wight ; Bassia, Kon. Affinities, &c. Allied to Myrsinacepe, but distinguished by the placen- tation, anatropal ovules, and other important characters, also to the Ebenaceae, which they resemble in habit; but they have a milky juice, and wood generally of a soft character ; other differences also exist in the perfect flowers, such as erect ovules, simple styles, &c. Distribution. A considerable group. Chiefly tropical: Asia, Africa, and America. Qualities and Uses. The plants of this Order are valuable for succu- lent fruits, febrifuge bark, oleaginous secretions, and peculiar gum-resins in the milky juices. Of the fruits, the Sapodilla Plum (Achrat Sapota), the Marmalade (A. mammosa}, the Star-apple (Chrysophylhtm Cainito}, and the Surinam Medlar (Mimusops Elengi) are the most noted. The bark of various species of Achras has been used as a substitute for Cin- chona. The fruits of Bassia butyracea and B. lonyifolia yield a butter- like oil largely used in India ; another species in Africa is said to yield the Shea or Galam butter mentioned by travellers. Isonandra Gutta is the tree from which Gutta Perch a is obtained, by evaporating the milky juice. The seeds of Argania Sideroxylon contain a valuable oil. EBE"NTACE J3 are trees or shrubs with alternate entire leaves, without milky juice; flowers regular, polygamous, with the calyx free from the 3-12-celled ovary ; the stamens twice or four times as many as the lobes of the corolla, often in pairs before them ; anthers intror.*e ; fruit a several- celled berry ; ovules 1 or 2, suspended from the summit of each cell ; seeds large, perispermic ; radicle superior. Illustrative Genera : Royena, L. ; Diospyros, L. Affinities, &c. The Ebenaceae are distinguished from the Sapotacere by several important characters noted under that Order ; on the other hand, they approach the Aquifoliaceae in many points, but are separated by their strongly coherent floral envelopes, usually numerous stamens, and twin ovules, &c. To the Oleaceae they are allied by the placentation and other points ; but the alternate leaves, more numerous stamens, and com- monly diclinous flowers afford very marked distinctions. The Styra- cacese are also very near to this Order, but frequently have an adherent calyx, petals less coherent, and a simple style with a capitate stigma. Distribution. A considerable group, the members of which are dis- tributed mostly in tropical India, but a few are scattered elsewhere. COEOLLIFLOE.il. 303 Qualities and Uses. The principal property which has been noted in these plants is astringency ; but they are better known and far more important on account of their hard and dark-coloured wood, the heart- wood of many species of Diospyros constituting Ebony : D. Ebenus yields it in Mauritius : D. Melanoxylon on the Coromandel coast ; D. Ebenaster is the bastard Ebony of Ceylon ; and D. hirsuta has a variegated wood called Calamander. Other species are also used. D. virginiana, a North- American species, bears the fruit called Persimmon or Date-plum, which, is astringent when ripe, but is eaten after it has been affected by frost. Diospyros Lotos (Europe) and D. Kaki (China) have also edible fruit. AQUIFOLIACKE on ILICACE^E (THE HOLLY OBDER) comprise trees or shrubs, with small axillary 4-6-merous flowers, sometimes dicli- nous by abortion ; a minute corolla free from the 4-6-celled ovary and the 4-6-seeded berry ; the stamens as many as the divisions of the almost or quite divided 4-6-petalous imbricate corolla, alternate with them, attached to the very base ; ovary 2-6-celled ; cells with 1 ovule ; stigma almost sessile, lobed ; fruit succulent, with 2-6 stones ; seeds suspended, with copious fleshy perisperm ; radicle superior. Illustrative Genera : Ilex, L. ; PrinoSj L. Affinities, &c. The affinities of Aquifoliaceas to Ebenaceae and Sapotaceae have been noticed under those Orders. Some authors consider them re- lated to Rhamnaceae or Celastraceae; but their sympetalous corolla, want of disk, straight embryo, and their relations to Ebenaceae, as well as the difference in the ovary and seeds, remove them from the immediate neighbourhood of those Orders. On the other hand, they exhibit some approach to Loganiaceae and Apocynaceae. Distribution. A small Order, widely scattered, but sparingly. Ilex Aquifoliumj the Holly, is the only European species. Qualities and Uses. The bark is ordinarily astringent and tonic, and that of the Common Holly is esteemed a febrifuge ; its berries produce emetic and purgative action ; its leaves and still more those of Ilex para- yuayensis, called Mate or Paraguay Tea, resemble Tea in property, as is the case also with Prinos glabra, a North-American shrub. Other species of Ilex are also used for this purpose in South America. The viscid substance called Bird-lime is made from the bark of the Holly ; and its close white wood is valued by cabinet-makers. STYRACACEJE are remarkable among the Orders here placed near it for the inconstancy of the character dependent on the adhesion of the calyx ; Miers divides it into two, Symplocaceae and Styracaceae, separated by this mark, by the aestivation of the corolla, and other points. It is com- monly regarded as related to Ebenaceae among the Corollifl orals, and also to Aurantiaceae and Ternstroemiaceae among the Thalamiflorals ; while Lindley connects it with Celastraceae through Sapotaceae : others point out a resemblance to Philadelphaceae. Distribution. Scattered sparingly in the warm regions of Asia and America. Qualities and Uses. Bitter and aromatic, sometimes containing a pun- gent resin. Gum Benzoin is obtained from Styrax Benzoin in the Malay 304 SYSTEMATIC BOTANY. archipelago ; Storax from St. officinale in Syria j other species yield similar resins. ISymplocos furnishes dyes or mordants ; the leaves of S. tinctoria (Sweet-leaf, or Horse-sugar, North America) are sweet, and are eaten by cattle. Halesia tetraptera, another North-American plant, is called the Snowdrop tree on account of its numerous white bell-shaped blossoms. The following Orders, sometimes placed in this subdivision, are of doubtful position, or rather their affinities are very various : OLACACE^E constitute an Order of tropical trees and shrubs, often climbers, apparently nearly related to Santalaceae, but having distinct, rarely united, petals and a free ovary. The stamens are frequently superposed to the petals. ICACINACE^E, separated from the preceding by Miers and Eichler, have the stamens alternate with the petals. In both the aestivation of the petals is valvate ; while CYRILLACE^E, a group of American shrubs, have imbricate petals and a disk surrounding the ovary ; they are placed next Aquifoliaceee by Bentham and Hooker. HUMIRIACE^E are tropical Ame- rican trees or shrubs with balsamic juice, free petals, and monadelphous stamens, each having an enlarged fleshy connective ; they appear to be related to the Olacacese and Linaceae, having also affinities to the Styra- caceae and Aurantiacese. The systematic position and, in some cases, the exact limitations of these groups is unsettled ; as is also that of CANEL- LACE^E, a little group of plants connected with Clusiaceae by some authors, by others with Olacaceee and their allies, placed by Bentham and Hooker near Bixacese and Violaceas, but more nearly allied in structure and bitter aromatic properties to Magnoliaceee. Series 3. DICAEPI^E. Ovary usually superior. Stamens alternate and isoinerous with the lobes of the corolla or fewer. Carpels 2, rarely 1-3. The typical formula isS5|P5A5G-2. OLEACEvE. THE OLIVE AND ASH OEDEE. Coh. Jasrninales, jBenth. et Hook. Diagnosis. Trees or shrubs with opposite and pinnate or simple leaves j flowers with a 4-cleft (or sometimes obsolete) calyx; a regular 4-cleft or nearly or quite 4-divided, hypogynous corolla, the lobes of which are valvate in the bud, or sometimes apetalous ; stamens 2-4, mostly 2, and fewer than the lobes of the corolla (figs. 408, 409) j ovary 2-celled, with 2 suspended ovules in each cell : fruit fleshy or capsular, often 1-seeded by abortion ; seeds with abundant fleshy nerisperm ; radicle su- perior. Illustrative Genera : Tribe 1. OLE^. Fruit fleshy. Olea, Ttiurnef. Tribe 2. FEAXINE^. Fruit dry, some- times samaroid. Fraxinus, Tournef. Fig. 408. Fig. 409. Fig. 408. Diagram of flower of Lilac (Syringa) : x, bract ; a, a, bracteoles. Fig. 409. Achlamydeous flower of Fraxi- nus. COROLLlFLORjE. 305 Affinities, &c. The relations of this Order are rather obscure. Some authors connect them with the Jasniinaceae ; but although some of the genera approach that Order in structure, they appear to be distinct in their valvate corolla, adnate (dorsilixed) anthers, pendulous ovules, and the nature of the perisperni. They are also related to Apocynaceas and Rubiaceae. The Salvadoraceae are also to be regarded as a neighbouring family. Lindley thought the Order allied to Solanaceae. Distribution. A small Order, the members of which are chiefly found in temperate climates. Qualities and Uses. The most important plant of the Order is the Olive (Oka europcea), so largely cultivated for the bland oil expressed from the fleshy pericarp. Ornus europcea, O. rotundifolia, and Fraxinus excelsior have a sweet juice which hardens into the substance called Manna. Fraxinus excelsior is the common Ash-tree, so valuable for its tough wood ; it only produces Manna in a warmer climate than Britain ; its bark, as well as that of the Olive and Garden Lilac (Syringa wdgaris), has decided febrifuge qualities. The leaves of the Ash act like senna. The flowers of Oleafrayrans were formerly used in China to flavour Tea. This Order contains several of the commonest flowering shrubs of our gardens, the Lilac (Syringa), Privet (Ligustrum), Phillyrea, Chionanthus, &c. JASMINACEyE. The Jasmine Order consists of shrubs, often with twining stems ; leaves opposite or alternate, mostly compound ; calyx and corolla hypogynous, 5-8-parted, corolla imbricated in the bud ; stamens 2, projecting from the tube of the corolla; ovary superior, 2-lobed, 2-celled, with 1-4 erect ovules in each cell ; fruit a berry or capsule ; seeds with little or no perisperni, radicle inferior. Illustrative Genera : Jasminum, L. ; Nyctanthes, Juss. Affinities, &c. This Order is distinguished from the Oleaceae by the im- bricated aestivation of the corolla, the erect ovules, and the small quan- tities of perisperm in the seeds, besides the number of the organs in the floral envelopes, which is seldom a multiple of the stamens : most authors place it near Oleaceae, others near Apocynaceae and Ebenaceae ; but Lindley thinks it has little connexion with them, and really approaches more closely to Verbenaceae. Distribution. The Order is not very extensive ; the major part of the plants are East-Indian ; a few occur scattered, two even in South Europe. Qualities and Uses. The leaves and roots appear to possess a certain acridity ; but the most remarkable quality is the fragrance of the flowers of many kinds, from the presence of a volatile oil. Jasminum officinale, J. rjrandiflorum, and J. Sambac especially yield this. Nyctanthes Arbor- tristis is also exceedingly fragrant, but in the night-time only ; its corollas yield an orange dye. SALVADORACE^E are a small Order of shrubs or small trees with opposite leathery leaves, panicled small flowers ; calyx, corolla, and stamens 4-merous, hypogynous; ovary superior, 1 -2-celled ; stigma sessile; ovule 1-2, erect; fruit fleshy, 1-seeded, and the seed without perisperm. It is related by its 4-nary structure to Oleaceae and to Plan- taginaceae, having a membranous corolla like the last ; also resembling x 306 SYSTEMATIC BOTANY. Plumbaginaceae in habit. Baillon points out an affinity to Celastraceaa. The species are found in India, Asia Minor, and North Africa. The most important is Salvadora persica, supposed to be the Mustard-tree of the Bible, its fleshy fruit having an aromatic odour and tasting like garden- cress. The bark of its root is used in India as a vesicatory. The leaves of S. indica are purgative. LOGAJNTACE.E. Coh. Gentianales, Benth. et Hook. Diagnosis. Trees, shrubs, or herbs with opposite leaves and interposed stipules sometimes reduced to an elevated line or a ridge ; calyx 4-5- cleft; corolla hypogynous, gamopetalous, regular, 4-, 5-, or 10- cleft, val- vate or contorted or imbricated in aestivation ; stamens springing from the corolla ; ovary superior, usually 2-celled ; style divided above into as many lobes as the cells of the ovary ; ovules numerous or solitary ; fruit capsular, 2-celled, with the placentas finally detached, drupaceous, with 1- or 2-seeded stones, or baccate with the seeds immersed in pulp ; seeds with a straight embryo in fleshy or cartilaginous perisperm, sometimes winged, mostly peltate ; embryo straight, radicle inferior. ILLUSTRATIVE GENERA. Tribe 1. GELSENIE-ZE. Corolla-lobes imbricate ; style bifid; stigmas lateral ; fruit capsular. Gelsenium, Juss. Tribe 2. EU-LOGANIE^;. Style simple; stigma terminal ; ovules numerous in each cell of the ovary. Spigelia, L. ; Buddleia, L. $ Desfontainea, Ruiz et P. ; Usteria, Wittd. ; Strychnos, L. Tribe 3. GJERTNEREJE. Style bifid; cells of ovary I-ovulate; corolla-lobes valvate. Geertnera, L. Affinities, &c. This Order was formerly associated with Apocynaceas and the neighbouring Orders ; but, as remarked by Bentham, it consists, on the whole, of Rubiaceae with a free ovary, at the same time approaching, by ceitain of its diverse forms, some of the genera of several of the Corollifloral Orders even more nearly than the general mass approach Rubiaceae. To Apocynaceae, which are very near in general structure, some genera, such as Geniostoma, which has contorted aestivation of the corolla, and Mitrasacme, where the carpels are partially distinct below and united above, approach very closely ; Mitrasacme and Mitreola were formerly arranged as doubtful Gentianaceee, and Fagrcea and Potalia approach still more nearly, the former greatly resembling Lisianthus in character, while Buddleia and its allies have been referred to Scrophulariaceae until lately, but are brought into this Order by Bentham, since they cannot be separated from Logania. The main difference from Apocynaceas lies in the stipules ; but these are sometimes reduced to a mere line connecting the leaves : the peculiar stigma of that Order affords another means of separating them ; and the Apocynacpfe often have hypogynous glands, which the Loganiaceae have not. Fr( m Gentianaceae the distinction lies generally in the stipules and the axile placentation ; occasionally the succulent condition of the fruit is required as a decisive mark. From the Scrophulariacese the stipules, COEOLLIFLOB^;. 307 the regular corolla, the agreement of the number of stamens and lobes of the corolla, and quincuncial aestivation divide Loganiaceae in most cases ; and although the aestivation and the regular corolla occur sometimes in the former Order, there are then usually alternate leaves and no stipules. As observed by Bentham, this is hardly so much a Natural Order as a receptacle for anomalous forms of several really natural groups, Rubiaceae, Apocynaceae, Gentianaceae, &c. Distribution. A rather large group, the species of which are chiefly tropical, but some are found in North America and Australia. Qualities and Uses. The plants belonging to this Order have mostly powerful poisonous properties, in particular the genus Strychnos. S. Nux-vomica bears the seeds known by its name, so noted for the presence of Strychnia. S. toxifera is said to furnish the active ingredient of the celebrated Woorali poison of Guiana. S. cogens is likewise used to poison arrows in Central America. S. Tieute (the bark of the root) yields the Java poison called Upas Tieute. Many seem to be free from strychnia as regards the bark ; for that of S. Pseudoquina is used as a substitute for Cinchona in Brazil, that of 8. Nux-vomica also,and the wood of S. ligustrina, called Lignum colubrinum. S. potatorum, an East-Indian species, is called the Clearing-nut ; and it is said that, when its seeds are rubbed round in a vessel containing muddy water, it causes the impurities to settle. The seeds from the Philippines, known as St. Ignatius's Beans, have been described as the seeds of a plant called Ignatia amara ; but are probably those of an unknown Strychnos, perhaps multiflora, which grows on those islands. The species of Spigelia are aero-narcotic ; S. marilandica, the Carolina Pink-root, and 8. Anthelmia are used as vermifuges, but are somewhat dangerous, sometimes producing spasms and even convulsions. Potalia amara is bitter, acrid, and emetic. GENTIAN ACE^E. THE GENTIAN OBDEB. Coh. Gentianales, Senth. et Hook. Diagnosis. Smooth herbs, with a bitter juice, opposite and sessile, mostly simple, entire, and strongly ribbed leaves, without stipules ; flowers regular, with a persistent calyx, with stamens as many as the lobes of the usually withering-persistent corolla, and which are convolute (rarely imbricated, and sometimes valvate) in the bud ; ovary 1-celled, with two parietal placentas, projecting more or less toward the centre ; the fruit mostly a 2-valved, septi- cidal, many-seeded capsule, sometimes with a fleshy pericarp; seeds small ; embryo minute in the axis of fleshy perisperm. ILLUSTRATIVE GENERA. Tribe 1. EXACEJE. Corolla-lobes contorted dextrorse; ovary ^-celled. Exacum, L. Tribe 2. CHIRONIEJS. Corolla-lobes dextrorse ; ovary 1-celled. Chironia, L. Tribe 3. SWERTIEJE. Corolla-lobes auntorted or imbricate; ovary 1-celled; style short. Gentiana, L. 308 SYSTEMATIC BOTANY. Tribe 4. MENYANTHEJE. Leaves radical or alternate ; corolla-lobes mdu- plicate-valvate ; ovary I- celled. Menyanthes, L. ; Villarsia, Vent. Affinities, &c. This Order stands very near Apocynacese, from which it differs in its placentation and completely coherent carpels, habit, want of milky juice, and other points. The parietal placentas distinguish it from the Scrophulariacea? and allied Orders, which sometimes show an approach to the regular structure of Gentianaceaa. Gesneraceae differ in their irregular flowers, axile embryo, and other characters. An affinity exists to Oroban- chacese, especially through Obolaria, a N.-American plant formerly re- ferred to that Order, Voyra, a parasitic leafless genus, and some allied forms lately discovered in South America, while Crawfurdia, a twining genus, seems to connect the Gentianacese with Convolvulacese. Distribution. A large Order, generally diffused the large genus Gen- tiana especially inhabiting the mountains of temperate and hot climates, but not in polar regions. Qualities and Uses. Bitter, tonic properties are general; a few are emetic or narcotic, especially when fresh. Among the bitter kinds medi- cinally employed are the Gentians, G. lutea (officinal), punctata, jwrpurea, pannonica, all European, G. Catesbcei (U.S), G. Kurroo (Himalaya), -Frascra Watteri (\J.S)^AffatJiotes Chirayita, a native of the Himalayas. Erythrcea Centaurium, Menyanthes trifoliata, Chlora perfoliata, Gentiana campestris and Amarella, all British Kerbs, have been used in the same way. The plants of this Order mostly have beautiful flowers, brilliant blue predomi- nating, but red, white, and purple, and more rarely yellow occurring. The Gentianella of our gardens is G. acaulis ; and the smaller Gentians are among the most beautiful of Alpine plants. Villarsia nympliaoides is an elegant water-plant occurring in Britain. Limnanthemum, an exotic genus, is also aquatic. APOCTNACE^E. DOG-BANES. Coh. Gentian ales, Bcnth. et Hook. Diagnosis. Plants with milky acrid juice, entire (mostly oppo- site) leaves, without stipules ; flowers regular, 5-merous and. 5- androus ; the 5 lobes of the corolla convolute and twisted in the bud; the filaments distinct, springing from the corolla, and the pollen granular ; ovary 2- or more rarely 1-celled, composed of 2 carpels more or less coherent in the ovarian and stylar region and quite blended in the drum-shaped or dumb-bell-shaped stigma ; ovules numerous ; fruit 1 or 2 follicles, a capsule, drupe, or berry ; seeds mostly with fleshy or cartilaginous perisperm, often with a tuft of hairs at the top. ILLUSTRATIVE GENERA. Tribe 1. CARISSE^. Anthers free ; ovary entire. Allamanda, L. Tribe 2. PLUMIERLEJE. Anthers, free, ivithout appendages; ovaries free; styles united. Vinca, L. Tribe 3. ECHITIDE^,. Anther-cells with appendages at the base ; ovaries free ; styles united. Keriuni, L. COROLLIFLOE2E. 309 Affinities, &c. Related closely to some Loganiaceae and to Gentianacese, ' as noticed under those Orders also to Asclepiadaceae, from which they are chiefly distinguished by the freedom of the stamens from the stigma and by the granular pollen. The thickened stigma, however, and appendaged anthers found here indicate a close relationship. Alyxia has ruminate perisperm. Distribution. A large group, the species of which are chiefly tropical, a few scattered in temperate climates. Vinca occurs in Britain. Qualities and Uses. Often violent poisons, acting as drastic purgatives and emetics, sometimes with a narcotic influence. Not a few, however, have delicious edible fruits ; and the bark of some is tonic and febrifuge. The milky juice contains Caoutchouc, in some cases sufficient to become commercially valuable. The poisonous principles appear to occur chiefly in the seeds and in the milky juice. The seeds of Tanghinia venenifera, the Madagascar Poison-nut, are very deadly, as are also the seeds of Cerbera, Thevetia, Cameraria latifolia (the Bastard Manchineel), the stem, root, leaves, and flowers of Nerium (the Oleander), Echites, Plumiera, &c. Where somewhat milder, as in Apocynum and Allamanda, the plants are occasionally available medicinally, but only in small doses. Wriyhtia antidysenterica, some species of Carissa, Hancornia pubescens, and others are simply bitter and febrifuge, like Gentians. The succulent fruits of Hancornia speciosa (Brazil), Carissa Carandas and edulis (East Indies), Roupellia grata (Sierra Leone), are not only harmless,' but very delicious. Caoutchouc is obtained from Urceola elastica, Willuyhbeia edulis (East indies), Valiea yummifera (Madagascar), Cottophora utilised Cameraria latifolia (South America), also from species of Landolpkia and Hancornia. The milky juice of Taberncemontana utHis, the Cow-tree of Demerara, is innocuous and nutritious. Wriyhtia tinctoria furnishes a kind of indigo ; and the wood of species of Wriyhtia (East Indies), Aspidosperma (Guiana), &c. is valuable as timber. The bark of Alstonia scholaris is recommended as a tonic and antiperiodic. This Order furnishes some of our most beautiful stove-plants Eckites, Allamanda, Dipladenia, Nerium, Plumiera, &c. forming striking ornaments in every extensive horticultural collection. ASCLEPIADACE^:. Coh. Gentianales, Benth. et Hook. Diagnosis. Shrubs or herbs, often twining, with milky juice, opposite or whorled (rarely scattered) entire leaves without stipules : floxvers regular, 5-merous, 5-androus, the lobes of the corolla mostly valvate ; filaments springing from the corolla-tube, united into a tube, and often prolonged beyond and behind the anther into horn- like processes constitutiug the corona; carpels 2, distinct, or coherent below ; stigmas coherent into a 5-angled fleshy head, to which the anthers are adherent (fig. 410) ; pollen coherent into wax-like or granular masses ; ovaries with numerous ovules on the 310 SYSTEMATIC BOTANY. sutures ; fruit a pair of follicles, or by abortion 1 ; seeds mostly with a crown of hairs at the hilum, with thin perisperin. ILLUSTRATIVE GENERA. Suborder 1. PERIPLOCE^:. Pollen granular ; anthers acuminate. Peri- ploca, L. Suborder 2. ASCLEPIADEJE. Filaments united into a tube , pollen in waxy coherent pollinia. Asdepias, L. ; Hoya, R. Br. j Stapelia, L. Fig. 410. ct \Jf o, Flower of Asclepias purpurascens; b, a vertical section, with the petals removed; c, side view of a stamen ; d, inside view of an anther (p, pollen-sac); e, two pollen-masses ; /, cross section of the ovary. Affinities, &c. The genera are further grouped into tribes and subtribes, according to the nature of the anthers and pollinia. The curious organiza- tion of the stigma and pollen is the great distinguishing feature of this Order, which in other respects is closely allied to Apocynaceae. When the pollen is mature, it escapes in " pollen-masses " from the anthers (fig. 410, e), and adheres to gelatinous processes developed on the sides of the stigma, which retain it, so that it can push its pollen-tubes into the lateral and inferior stigmatic surfaces ; after fertilization, the stigma with the ad- herent anthers and filaments separate from the style and leave a pair of distinct carpels, which ripen (one or both) into free follicles. Distribution. A large Order, mostly tropical, in Asia, Africa, and America; one or two species occur in Europe, and a few in North America. Qualities and Uses. Generally resembling the Apocynaceae j but the active properties are not so much developed, and the succulent fruits do not appear here. Species of Asclepias, Cynanchum, Calotropis (Mudar), Tylophora, and Periploca are more or less emetic or purgative ; the leaves of Solenostemma Argliel and Gomphocarpus fruticosus are frequent adulte- rations in Alexandrian Senna, and are said to cause griping. The roots COEOLLIFLOBxE. 311 of Hemidesmus indicus are used as a substitute for Sarsaparilla. The milky juice of Cynanchum ovalifolium yields Caoutchouc at Penang. Marsdenia tenacissima and Orthanthera viminea, East-Indian plants, afford very tenacious fibre ; Marsdenia tinctoria a kind of Indigo. The Stapelice and Ceropeyice are remarkable for their succulent habit ; some of them form curious tubers, as Brachystelma. Hoya partakes of the succulent habit, but has wax-like leaves and blossoms, sometimes very handsome. Dischidia is remarkable for its pitcher-leaves. Gymnema lactifera is the Cow-plant of Ceylon, which yields a milky juice, harmless and nutritious, and which is used by the natives as food. HYDROPHYLLACEAE form a small Order, allied in some respects to Boraginacese, but differing in their one-celled many-seeded ovary with parietal placentation, which also separates them from Polemoniaceae, with which they have many points of agreement. They are chiefly natives of the north and extreme south of America. Their properties are unimportant ; but species of some of the genera, as Nemophila, Eutoca, &c., are interesting and showy garden plants, grown with us as tender annuals. Hydroleads are sometimes separated from this Order by reason of their distinct styles and anatropous ovules. DIAPENSIACE^J consist of two genera, Diapensia and Pyxidanthera, each having one species. They are connected with Convolvulaceae by some authors, but appear to stand between Hydrophyllaceae and Pole- moniaceee, having a 3-celled ovary like the latter, and a filiform embryo with very short cotyledons, approaching that of the former. They are very closely allied to Ericaceae, but the anthers do not open by pores. POLEMONIACE^E (THE PHLOX ORDER) consists of herbs with alternate or opposite leaves, regular o-merous and 5-androus flowers, the lobes of the corolla mostly convolute (sometimes imbricated) in aestiva- tion ; ovary 3-celled, style 3-lobed ; the capsule 3-celled, 3-valved, few- or many-seeded ; valves usually breaking away from a triangular central colunieila ; seeds perispermic ; embryo straight ; cotyledons elliptical, foliaceous. Illustrative Genera : Phlox, L. ; Polemonium, Tournef. ; Cav. Affinities, &c. One of the smaller Orders ; it is remarkable for its 3-celled ovary. It is nearly related to Convolvulaceae, Cobcea agreeing even in the climbing habit; the ovary equally distinguishes it from these, the Hydrophyllaceae, and the Gentianaceae, to all of which it has close affinity. From Diapensiacese it differs in the regular calyx and insertion of the stamens, as well as in the embryo. The seeds are remarkable in many cases for hairs upon the testa containing a spiral fibre ; in Collomia these expand elastically when wetted j in Cobcea they are short, broad, and firm. The Polemoniaceae occur most abundantly in the temperate regions of North and South America. Polemonium ceeruleum, Greek Valerian or Jacob's Ladder, grows in the north of England, and is common in gardens. The other genera furnish some of the favourite tender peren- nial and annual herbaceous plants of our gardens. They have no im- portant properties. 312 SYSTEMATIC BOTANY. CONVOLVULACE.E. THE BINDWEED OEDEE. Coh. Convorvulales, Benth. et Hook. Diagnosis. Chiefly twining or trailing herbs, sometimes leafless and parasitic, or shrubby and erect, often with some milky juice ; with alternate leaves (or scales) ; -p. ,-,, flowers regular, 5-androus ; calyx of 5 imbricated sepals, the 5-plaited or ^P^C|l8i^ Fi 419 5-lobed corolla convolute or twisted in l ' the bud; ovary 2-celled (rarely 3- celled), or with 2 separate pistils, with 2 erect ovules in each cell, the cell sometimes doubled by a false partition between the seeds, thus falsely 4-celled ; embryo lirge, curved or coiled in mu- cilagii ous perisperm, with foliaceous cotyledons, or (Cuscutece) filiform and F % l 1 L5 nel ~ 8haped C r Ua ** coiled with the cotyledons scarcely per- FIR. 412. Plicate aestivation of the ceptible ; radicle inferior. Illustrative Genera : Convolvulus, L. ; Cuscuta, Tournef . Affinities, &c. This Order approaches the regular sympetalous Boragi- nacese, Polemoniaceee, and allied Orders; the structure of the ovary separates it from the first, the curved embryo and the fruits from the second. Cordias also differ in their aperispermic seeds and superior radicle. Some of the Convolvulacese are of shrubby habit, and depart widely from the appearance with which we are most familiar. Cuscuta is sometimes made the type of a distinct Order ; but the parasitical habit is not a sufficient character. Distribution. A large Order, of which a few species occur in temperate climates, but the majority belong to the tropics. Qualities and Uses. A purgative property generally characterizes these plants, among which are several yielding important medicinal substances. True Jalap is the root of Exoyonium Purya, Scammony of Convolvulus Scammonia ; Pharbitis cathartica and Ipomosa tuberosa yield a similar substance. The white hedge-Convolvulus (Ccdystegia sepiuni) has a similar action, as also various Ipomcea and Convol'vuli, the active matter being a kind of resin existing in the milky juice. The seeds of Pharbitis Nil (semen Kaladanse) and P. c&rulea are also used as purgatives. On the other hand, Ipomosa edulis forms a large fleshy tuber, which is widely cultivated and eaten under the name of the Sweet Potato, and Ipomcea macrorhiza has edible farinaceous roots. The twining and trailing plants of this Order are mostly remarkable for the beauty of their flowers, and many of them are cultivated; the garden Major Convolvulus is Pharbitis purpurea, the blue Minor Convolvulus is Convolvulus tricolor. Convolvulus arvensiSj Bindweed, grows everywhere, on the ground, rooting- at the nodes ; C. SoldaneUa grows in like manner on the sea-shore ; Catystegia COKOLLIFLOKJE. 313 sepium, the White Convolvulus, is one of our most beautiful and at the same time commonest hedge-plants. The Cuseuteee or u Dodders " are remarkable for their leafless and parasitic habit ; they germinate in the ground, and then coil themselves round the stems of plants and send roots in through their rind, by which they are then entirely nourished. They have wire-like stems with minute scales at the nodes, and tufts of small Convolvulaceous flowers. They are great pests in clover- and flax-fields, destroying the plants they infest. SOLANACEJE. NIGHTSHADES. Coh. Polemoniales, Benth. et Hook. Diagnosis. Herbs, rarely shrubs or trees, with colourless juice and alternate leaves; flowers regular, or slightly irregular, often extra-axillary, 5-merous and 5-androus, on bract-less pedicels ; corolla hypogynous, plaited-i rubricate, plaited-convolute, or invo- lutive-valvate in aestivation ; stamens epipetalous ; ovary 2-celled, cells antero-posterior ; fruit a 2-celJed (rarely 3-5-celled) many- seeded capsule or a succulent berry. Seeds perisperinic ; embryo curved. Fig. 413. Deadly Nightshade (Atropa Belladonna). 314 SYSTEMATIC BOTANY. Character. Thalamus flat. Calyx free, or rarely 4- or 6-cleft, persistent, or the upper part separating by transverse dehiscence, mostly growing somewhat during the ripening of the fruit (accrescent). Corolla gamopetalous, 5- or rarely 4- or 6-parted or toothed, rotate, campanulate, funnel- or salver-shaped, sometimes ob- liquely irregular, plaited-imbricate, plaited-convolute, or involu- tive-valvate in the bud. Stamens springing from the tube of the corolla, equal in number to its lobes and alternate with them ; filaments sometimes rather unequal ; anthers 2-celled, with the Fig. 414. a, Corolla of Atropa Belladonna, showing the attachment of the stamens; 6, cross section of the oyary. cells sometimes connate above, dehiscing longitudinally or by terminal pores. Ovary usually 2-celled, the carpels antero- posterior ; placentas axile, sometimes enlarged into spurious dissepiments, rendering the ovary 4-celled ; ovary rarely 3-5- celled by increased number of carpels ; ovules numerous ; style simple ; stigma simple or lobed. Fruit capsular, with septicidal or transverse dehiscence (fig. 294), or a succulent or dryish in- dehiscent berry (fig. 301) ; seeds numerous, the embryo mostly slender and curved, sometimes straight, with foliaceous coty- ledons in fleshy perisperm. Petunia, Juss. Nicotiana. Tournef. Datura, L. ILLUSTRATIVE GENERA. Hyoscyamus, Tournef. Physalis, L. Capsicum, Tournef. Solanum, L. Atropa, L. Mandragora, Tournef. Affinities, &c. A considerable range of variation in the condition of most of the organs upon which a character is founded renders it difficult to circumscribe this Order strictly; in fact it passes by almost insensible gradations into the Scrophulariaceee. Generally speaking, the Solanacese COROLLIFLOBJE. 315 are distinguished by the plaited aestivation of the corolla, equality of the number of stamens 'with the lobes of the corolla, and a curved embryo from the Scrophulariacese, which have imbricated aestivation, stamens fewer than the lobes of the corolla, and a straight embryo ; but none of Fig. 415. Henbane (Hyoscyamus niqer). these characters are constant in the former Order ; yet the nearly regular corolla and five perfect stamens will in almost all cases distinguish the Solanacese. Miers has proposed, in extension of a suggestion of R. Brown, to establish a new Order, Atropaceae, to include the aberrant forms of Solanacese and Scrophulariaceae, and leave these better defined the brief diagnoses of these Orders being : 1. SOLANACEJE. Stamens equal in number to the lobes of the corolla (or petals), whose aestivation is valvate or induplicate-valvate. 2. ATRO- PACE^E. Stamens equal in number to the lobes of the corolla (or 316 SYSTEMATIC BOTANY. petals), one sometimes sterile; aestivation of the corolla imbricated, or some modification of imbricated. 3. SCROPHULARIACEJE. Stamens less in number than the lobes of the corolla (or petals), 4 or 2 j aesti- vation of the corolla imbricated. This arrangement is, however, not adopted by Bentham and Hooker, who make five tribes of this order, viz. : Solaneae, Atropeae, Hyoscy- amete, Cestrineae, and Salpiglossideae. The removal of the Buddleiea to LoganiaceaB, as proposed by Bentham, however, is favourable to this arrangement, as it removes the 4-androus genera with regular 4-lobed corollas, which would render the above diagnosis of Scrophulariaceae faulty. The Solanaceaa, as a whole, have, however, closer relations with some of the regular gamopetalous Orders, particularly with Hydrophyllaceae and Convolvulacese ; they are connected with Boraginaceae by Graboivskia, a Brazilian genus, formerly regarded as a Lycium, which has the habit of the latter with the ovary of Boraginaceae : it is nearly related to Nolana. According to Lindley, Cestrum connects the Solanaceae with theOleaceae, through Syringa ; but although it has a straight embryo with foliaceous cotyledons, the radicle is inferior, not superior, and the resemblance appears to exist chiefly in habit. Polemoniaceae differ in their 3-celled ovary and straight embryo. ^ Distribution. A very large Order, the members of which are generally distributed, and most abundantly in the tropics. Qualities and Uses. The genera referable to Atropaceae, as indicated above, are mostly characterized by narcotic poisonous properties. The Solanaceae are apparently less powerful, and certain kinds furnish whole- some and some important articles of food ; but many of them possess nar- cotic properties. Some have an acrid quality ; some have diuretic action ; and others are accounted tonics. Among the poisonous kinds the most important are : the Atropa Belladonna (Deadly Nightshade, which has the curious property of relaxing the iris, and thus causing dilation of the pupil, as also does Anthocercis viscosa) ; Datura Stramonium (the Thorn- apple), and D. Metel, Tatula, ferox, alba, &c. ; Hyoscyamus niger (Hen- bane), and other species ; Nicotiana Tabacwn, persica, and rustica (the American, Persian, and Syrian Tobacco-plants) ; Mandragora officinalis (the Mandrake), Acanthera venenata, a Cape shrub, said to be more deadly than any of them. The foliage of some species of Solanum is said to have active properties of the same kind, especially S.nigrum (Black Nightshade), 8. Dulcamara (Bitter-sweet or Woody Nightshade), and even the leaves and stems of 8. tuberosum (the common Potato) and Physalis somnifera. Solanum Pseudo-quina is employed in Brazil as a substitute for Cinchona. Some species of Cestrum, as laurifolia and Pseudo-quina, are said to have similar properties. Other Cestra, as C. euanthes, Icevigatum, &c., many species of Physalis, Solanum, &c., are accounted diuretic. The natives of central Australia chew the leaves of Pitury, Duboisia Hopivoodii, as a stimulant. It has similar properties to Coca (p. 234), and dilates the pupil. The species of Capsicum are remarkable for the pungent quality of the fruits, the common Capsicum being the produce of C. annuum, and Cayenne pepper consisting of the powdered seeds of various species, such as C. frutescens. While some of the plants are such active poisons in all parts, COEOLLIFLOK.I:. 317 others are only partially or not at all so. The berries as well as the foliage of Atropa, for example, and the seeds and capsules as well as the foliage of Hyoscyamus, are very deadly ; but the succulent fruits of many species of Solatium are wholesome, as the Egg- Apple or Aubergine (8. Melongend), those of 8. ladniatum, eaten in Australia under the name of Kangaroo Apples, &c., and, it is said (but this wants confirmation), those of the S. nigrum. Dulcamara, and others. Lycopersicum esculentum, the Tomato, is another example. Still more striking appears the instance of the Potato, at first sight ; but it must be remembered that the edible tuber is an artificial product, and consists chiefly of cellular tissue and starch deve- loped under circumstances that oppose the formation of the noxious secre- tion ; and what is present may be dissipated by heat. It is said that the poisonous element of Solanaceous fruits exists in a pulpy covering of the seeds, not in the pericarp. It is desirable that this point should be ascer- tained. COKDIACEJE constitute an Order, chiefly consisting of tropical plants, combined with Boraginaceae by Bentham and Hooker, from which, how- ever, they differ in the twisted aestivation of the corolla and the plaited cotyledons. From Convolvulacese they differ in their superior radicle and the absence of perisperm. The Order is remarkable for the plaited cotyle- dons of the embryo. The fruits of Cordia Myxa and latifolia are called Sebestens or Sebesten plums, and, with those of other species, are edible. NOLANACE^E are a small group of South-American plants, referred by Bentham and Hooker to Convolvulaceae, by others to Boraginaceae, some- times erected into a distinct Order on account of the valvate calyx, plaited regular corolla, the ovary of 5-20 carpels, either distinct, or when nume- rous combined into several sets, seated on a fleshy disk, with a single style and stigma ; the embryo curved, in little perisperm. The chief distinction from Boraginacese lies in the 5-merous ovary and the absence of the scroll- like inflorescence ; they may be regarded as aberrant forms of that Order. Some species of Nolana are cultivated in gardens for their showy flowers, somewhat resembling blue Convolvuli. Their properties are unknown. Genera : Nolana, L. ; Alona, Lindl. BOEAGINACE^E. THE BUGLOSS ORDER. Coh. Polemoniales, Benth. et Hook. Diagnosis. Chiefly roughly hairy herbs (not aromatic), with alternate entire leaves, a scorpioid inflorescence ^. .. usually without bracts, and symmetrical flowers with a 5-parted calyx, an hypogynous, regular (rarely slightly irregular) 5-1 obed corolla, 5 stamens springing from the corolla-tube ; ovary of two carpels, each deeply 4-lobed, the lobes surround- ing the base of the single gvnobasic style, and ,, P b . . . & . & -, , . ' , Persistent calyx of a forming when ripe 4 mdehiscent 1- seeded Boraginaceoua plant, achenesin the bottom of the persistent calyx; fSlormecfT four stigina simple or bifid ; seeds separable from indehiscent carpels. the pericarp, aperispermic ; radicle superior. 3E ting from each 318 SYSTEMATIC BOTANY. Echium, L. Borago, Tournef. ILLUSTRATIVE GENERA. Symphytum, L. An ch usa, Z. Lithospermum, L. Myosotis, L. Affinities, &c. The floral formula isS5|P5A5G2. The 4-lobed o\ary and fruit of this Order agree exactly with those of the Labiatae, in which the ir- regular corolla, didynamous stamens, opposite leaves, and square stems differ widely. This character of the ovary does not occur in any other regular o-androus gamopetalous Order. The Nolanaceae and Ehretiaceae depart from the general type of this Order. Ehretiaceae seem to bear the same relation to the proper Bora- ginaceaB as the Verbenaceae to Labiatas, having confluent carpels, terminal styles, and a shrubby or arborescent habit. The corolla mostly pre- sents a coronet of scales in the throat, which some incline to regard as abortive stamens. The bractless inflorescence of some of the genera is remarkable. The inflorescence, whether with or without bracts, is probably a unipa- rous scorpioid cyme, though it has been con- sidered to be an inflorescence of " parti- tion." Fig. 417. Bcorpioid cyme of Myosotis palustris. Distribution. A large Order, the species of which are mostly natives of temperate climates in the northern hemisphere. Qualities and Uses. The plants of this Order, remarkable for their rough foliage, have a reputation as mucilaginous and cooling herbs. Their chief importance lies in the dye furnished by the roots of Ancliusa linctoria (Alkanet) and various species of Echmm, Onosma, c., and the beauty of their flowers, whence the genera above cited include many common garden plants. The Forget-me-not is a native species of the genus Myo- sotis. Many Boraginaceaa occur wild with us. EHRETIACEJG consist of a group of plants included in Boraginaceaa by Bentham and Hooker, but separated by some authors on account of the coherence of the carpels and the terminal style (which is gynobasic in true BoraginaceaB) and a drupaceous fruit. Some genera have peri- sperm, others not. They seem to be as distinct here as Verbenaceae from the Labiatse ; but the agreement is very close at some points in both cases. They are also nearly related to the Cordiacea? ; but the latter have twisted aestivation and plaited cotyledons. Most of them are tropical trees or shrubs. None are of much importance : the drupes of some Ehretia are eaten ; the Heliotrope (Heliotr opium peruvianutri) is universally known for its delicious odour. Genera : Ehretia, L. ; Tournefortia, R. Br. j Heliotropium, L., &c. COROLLIFLOR^E. 319 LABIATE. Coh. Lamiales, Benth. et Hook. Diac/nosis. Chiefly herbs, with square stems and opposite aro- matic leaves ; flowers with a more or less 2-lipped, hypogynous corolla, clidynamous or diandrous stamens ; deeply 4-lobed ovary, the lobes surrounding the base of the single gynobasic style, and forming, when ripe, 4 indehiscent 1-seeded achenes in the bottom of the persistent calyx ; stigma bifid; seeds erect, with little or no perisperm. Character. Thalamus flat or slightly elongated, often prolonged into a hypo- gynous disk or series of glands. Calyx inferior, persistent, tu- bular, 5-merous, with the odd sepal posterior; the limb regu- larly 5- or 10-toothed, or irregular and bilabiate (fig. 418), 3- to Fig. 420. Fig. 419. Fig. 418. Fig. 418. Calyx of Salvia. Tig. 419. Corolla of Salvia. Fig. 420. Corolla of Glechoma opened, showing the didynamous stamens. 10-toothed. Corolla hypogynous, gamopetalous, bilabiate ; the upper lip entire or divided, arched or almost suppressed; the lower lip usually larger and 3-lobed (fig. 419). Stamens springing from the corolla, 4, didynamous (fig. 420), or some- times 2 ; anthers 2-celled or apparently 1-celled from the ap- position of the cells at the apex, or with the filament or con- nective bifurcate and bearing either 2 single cells or 1 perfect cell and a sterile process. Ovary deeply 4-lobed, on a fleshy disk, 4-celled, each cell with 1 erect ovule ; style simple, arising from the bottom of the carpels ; stigma forked. Fruit composed of 4, or, by abortion, 3, 2, or 1, dry, separable, 1-seeded por- tions, surrounded by the persistent calyx ; seeds with little or no perisperm ; cotyledons flat ; radicle inferior. 320 SYSTEMATIC BOTAKY. Lavandula, L. Mentha, L. Salvia, L. Rosmarinus, L. Origanum, L. ILLUSTRATIVE GENERA. Thymus, L. Hyssopus, L. Prunella, L. Lamium, L. Stachys, Benth. Marrubium, L. Ballota, L. Phlomis, L. Teucrium, L. Ajuga, L. Affinities, &c. A large and well-marked order, divided by Benth am into eight tribes, according to the number, position, and direction of the fertile stamens. The genera are founded on variations in the calyx and corolla, &c. As regards the structure of its ovary, this Order agrees exactly with Boraginacese, from which, however, almost all its other characters distinguish it. The ordinary structure is S 5 | P5 A~4 G~2, as for all Orders with didynamous stamens. Among the didynamous un- symmetrical monopetalous Orders, no other group approaches this struc- ture but Verbenaceae, which are distinguished by the greater degree of co- herence of the carpels and the terminal style, as the Ehretiaceae are from Boraginaceae ; but the separation of these Orders is sometimes difficult. Disregarding the ovary, the character of the corolla and stamens connects Labiate with Scrophulariaceae and its allies, especially when they have opposite leaves and square stems. The morphology of the corolla and stamens is very interesting in this Order, as it is in the Scrophulariacese ; the didynamous structure arises from the want of the posterior stamen, and in the diandrous genera it is the anterior pair that remains. Payer says there are originally five stamens in Labiates, two anterior first deve- loped, then two lateral, while the fifth or posterior is the last to appear, and indeed is often suppressed or present in the shape of a gland. The anterior first-born stamens are the longest and their anthers open first. The foliage of the majority of plants in this Order is studded with micro- scopic glandular hairs, containing the essential oils to which they owe their remarkable fragrance. Various species of Salvia have hairs upon the testa of the seed, containing a spiral fibre, somewhat as in Polemo- niacese. Distribution. A very large Order, the species of which are principally natives of temperate climates ; but the more fragrant kinds occur mos't abundantly in the warm temperate and drier regions. Qualities and Uses. The most striking qualities of this Order depend upon the presence of aromatic or fragrant essential oils, which render some of them valuable stimulants and antispasmodics, others favourite flavour- ing herbs for culinary purposes, others important ingredients in perfumes, &c. Some are also regarded as tonics. The fleshy subterraneous rhizomes of Stachys palustris are sometimes cultivated as a table vegetable j and the tubers of an Odmum are said to be eaten in Madagascar. Of the car- minative arovnatics, the Mints, Spearmint (Mentha viridis), Peppermint (M. Piperita), Penny-royal (M. Pulegiuni} are among the best known. Other species of Mentha have similar properties ; Hedeoma pulef/ioides, the Penny-royal of the United States ; Lavender, Lavandula vera ; to- gether with the inferior French Lavender, L. Sjrica, the oil of which, however, is chiefly used in the arts (oil of Spike), and others : many allied COKOLLIFLOKJ2. 321 species are used in different countries in the same way. The essential oils of some kinds commonly used as flavouring herbs are also used in vete- rinary medicine. Among the best-known of these, besides Mint, are Thyme (Thymus Serpyllum and other species), Marjoram {Origanum, vari- ous species), Basil (Ocimum sp.), Savory (Satureia sp.), Sage (Salvia officinalis and grandiflora), &c. As perfumes, Lavender, Patchouli (Pogos- temon Patchouli), Mentlia citrata, Rosemary (Rosmarinus officinalis), and others are largely used. Ilorehound (Marrubium vulgare) is an old- fashioned remedy for coughs; Ground-ivy (Nepeta Glechoma), Balm (Melissa officinalis) , and others are used by the country-people for the same complaints. Monarda fistulosa (a North- American shrub) and Origanum Dictamnus (or Dittany of Crete) are reputed febrifuges. Stachys Betonica has been regarded as a sternutatory, but perhaps acts mechani- cally : its root is said to be purgative and emetic ; but this seems unlikely to be true. Many plants of this Order decorate our gardens, and many species are wild in Britain. VERBENACE^ (THE VERVAIN ORDER) consists of herbs, shrubs, or trees, with opposite or alternate leaves ; flowers with an hypogynous more or less 2-lipped or irregular corolla and didynamous stamens ; style ter- minal ; the 2-4-celled fruit dry or drupaceous, usually splitting when ripe into as many 1-seeded, indehiscent nucules ; seeds erect or pendulous, with little or no perisperm. Illustrative Genera : Verbena, L. ; Tectona, L. ; Clerodendron, L. ; Vitex, L. ; Phryma, L. j Stilbe, Berg, j Myoporum, Bks. & Sol. ; Avicennia, L. ; JEgipliila, Jacq. Affinities, &c. Principally distinguished from Labiatae by the terminal st} r le and more coherent carpels. The Myoporcce, kept separate by Ben- tham and Hooker, can hardly be separated from the Verbenece except by the presence of two seeds in each cell of the ovary, and by the superior radicle; and perhaps Selaginaceae should be appended as an aberrant form. The structure of the fruit separates this Order from Scrophulariacese and its allies. Distribution. A large Order, chiefly tropical j the Verbenece common in temperate South America, and a few scattered in all regions. The Avicennics grow, like Mangroves ; in tropical salt marshes. Qualities and Uses. Those of the Verbenece are much the same as in Labiatas : Aloysia citriodora, the cultivated " Lemon-plant," or " Ver- bena," is an instance of fragrant properties ; many species of Lantana are fragrant or foetid ; some are used as substitutes for Tea. Vitex Agnus- castus, V. Negundo, and others have acrid fruits. Tectona grandis is the East-Indian Teak-tree, celebrated for its hard heavy wood (African Teak is from a Euphorbiaceous tree). The bark of Avicennia tomentosa, the White Mangrove of Brazil, is used for tanning. Olerodendrons are hand- some stove-shrubs. The brilliant Verbenas of our gardens are mostly varieties of Verbena chamcedrifolia and allied species. \ SELAGINACEAE form a small group differing from Verbenacese principally in having 1-celled anthers ; in Globularia the carpels are reduced to one. T 322 SYSTEMATIC BOTAXY. Hence there appears a connexion between them and Salvadoracese, which approach Verbenaceee and JShretiece among the Boraginaceae in other points. Some of the plants are European ; most of them belong to the Cape. Globularies have purgative and emetic properties. Genera: Selayo, L. ; Globularia, L. ACANTHACE^l. Coll. Personales, Benth. et Hook. Herbs or shrubs with opposite or whorled simple exstipulate leaves ; flowers irregular, bracteated, with an imbricated hypogynous more or less 2-]ipped corolla, didyuamous or diandrous stamens attached to the tube of the corolla ; fruit a 2-celled, 4-12-seeded capsule ; seeds anatropous, aperi- spermic, usually flat, supported by hooked or cup-shaped projections of the placentas; radicle inferior. Illustrative Genera: Thwioerffia, L. j Ruellia, L.; Barleria, L.; Acanthus, L. j Adhatoda, Nees; Justicia, L. Affinities, &c. This Order is closely related to Scrophulariacese and Big- noniacese, differing from the former in the aperispermic seeds, from the latter chiefly, so far as written characters can be given, in the structure of the placenta and in the seeds not being winged. Generally speaking, the large bracts of the inflorescence, and the imbricated calyx of unequal sepals, give a peculiar and characteristic appearance to these plants. The seeds of Acanthodium, Ruellia, and other species have a testa clothed with curious compound hairs containing spiral fibres. By Bentham and Hooker, following Anderson, the Order is divided into five tribes, viz. Thunberyiece, Nelsoniece, Huelliecs. Acanthece, and Justiciecs. The distinctions are founded upon the nature of the calyx, the aestivation of the corolla, the characters afforded by the seeds, &c. Distribution. A large Order, chiefly tropical. Qualities and Uses. Mostly without active properties. The most strik- ing peculiarity lies in the beauty of the flowers of many kinds, which renders them great favourites in our stoves. Acanthus mollis is interest- ing from its leaves having, it is said, furnished the model of the Corinthian capital. Andrographis paniculata is used as a bitter tonic. BIGNONIACE./E (THE TRUMPET-FLOWER OB DEE,) consists of woody, or rarely herbaceous plants, often twining or climbing, with exstipulate leaves, hypogynous sympetalous corollas, didynamous or diandrous sta- mens : the ovary commonly 2-celled, by the meeting of the 2 placentas or of projections from them, surrounded at the base by a disk ; many-seeded j the seeds large, winged, with a flat embryo, and no perisperm. Illustrative Genera : Biynonia, L. ; Tecoma. Juss. : Catalpa, Scop. : Eccremocarpus, K. &P. By Bentham and Hooker the order is divided into four tribes, Biyno- tiiea>, Tecomcce, Jacamndeee, and Crescentiece ; the latter often treated as a separate Order. The points of distinction are the number of cavities in the ovary, the nature of the fruit, the erect or climbing habit, &c. COROLLIFLOE^:. 323 Affinities, &c. The aperispermic character of the seeds separates this Order from Scrophulariaceee. From Acanthaceae there is less marked dis- tinction j but the winged and sessile seeds, together with the general habit of the inflorescence, mark the difference. Eccremocarpus approaches closely to Gesneraceae ; and these, with Pedaliaceae and Crescentiaceae. are chiefly separated by the want of coherence of the placentas in the axis (the exceptional case here in Eccremocarpus) and the absence of a wing to the seeds. Many Bignoniaceaa are remarkable for the structure of their woody stems, which have the wood divided into segments by broad wedged-shaped processes of the bark; the segments are 4 in young stems, forming a cross in the transverse section ; 8, and even 16 lobes ap- pear in the woody layers of subsequent years. The broad paper-like wing of the seeds of Biynonice has a very elegant microscopic structure. Distribution. A considerable family of mostly tropical plants ; the Trunipet-flowered climbers form striking features of American forests. Qualities and Uses. Many of the plants of this Order are used in Brazil for various purposes, such as dyes, medicines of varied action, timber, &c. ; but none are of very great importance. Their beautiful flowers, often large and brightly coloured, render them very attractive. Tecoma radicans, Eccremocarpus scaber, &c. are common garden climbers ; Catalpa syrinycefolia is a handsome tree with showy blossoms, hardy in this country. PEDALIACE^ are chiefly distinguished from Bignoniaceae by their generally wingless seeds, and by their different habit. Sesamum may be re- garded as intermediate between the Orders just named, while Martynia establishes a transition to Gesneraceae, of which Order Pedaliaceae, or, as they are sometimes called, Sesameae, are considered by some to form a tribe. They are chiefly tropical ; the most important member of the group is Sesamum orientate, which is an object of cultivation in the East for its seeds, from which oil resembling Olive-oil is obtained. Some of the species are in cultivation, among them one or two species of Martynia remarkable for the two long horns to the fruit. CRESCENTIACE^ are also very near to the Gesneraceae, and chiefly dis- tinguished by the arborescent habit and large amygdaloid seeds; the calyx also is free, and its limb splits irregularly. From Pedaliaceae the fruits and the amygdaloid seeds divide them. The indehiscent fruit and wingless seeds separate them from Bignoniaceae and Acanthaceae, and this, together with the want of perisperm, from Scrophulariaceae, Solanaceae, andLenti- bulariaceae. This Order is tropical, most developed in the Mauritius and Madagascar. Crescentia C^fjete, the Calabash-tree, has a fruit like a gourd, with a hard shell applicable to many useful purposes, holding liquids, forming floats for ratts, &c. The subacid pulp is eaten. Parmentiera ccrifera (Panama) has a long slender fruit, and is called, from the shape of this, the Candle-tree ; it is a favourite food of cattle. 324 SYSTEMATIC BOTANY. GESNERACE.E. CoJi. Personales, JSenth. et Hook. Diagnosis. Soft woody shrubs or herbs, somewhat succulent, with opposite or whorled wrinkled leaves, without stipules : flowers irregular ; corolla perigynous or hypogynous, sympetalous ; stamens diandrous or didynamous with a rudimentary 5th :" ovary half-superior, with a ring- of glands or a disk, 1-celled, with two 2-lobed parietal placentas; fruit capsular or succulent ; seeds numerous, with or without perisperni ; cotyle- dons much shorter than the radicle. ILLUSTRATIVE GENERA. Suborder 1. GESNEREJE. Seeds witli a little perisperm ; calyx partly "adherent " to the capsular fruit. Gesnera, Mart. Achimenes, P. Br. Gloxinia, Herit. Suborder 2. CYRTANDREJE. Seeds without perisperm fruit free, capsu- lar, twisted, or baccate. yEschynanthus, Jack. Streptocarptis, Lindl. Cyrtandra, Forst. Affinities, &c. The Gesneraceae have much the aspect of Scrophu- lariaceas ; and the flowers very much resemble those of Bignoniacese, but their placentas are decidedly parietal ; and although Eccremocarpus con- nects them with Bignoniaceee, its winged seeds and large cotyledons still mark the difference from Gesneracese. The parietal placentas resemble those of Orobanchaceas, which connect the Order further with Scrophu- lariaceae ; but in the Gesnerece, where the seeds are perispermic, the calyx is more or less adherent to the ovary. In Streptocarpus it sometimes hap- pens that one of the two cotyledons becomes persistent and enlarged, forming the only leaf formed b*y the plant. They are tropical plants, the Gesnerece American; the Cyrtandrece more diffused, but chiefly Eastern. They are of no great importance as regards their properties; some Gesnerece have edible fruits : the most interesting point about them is the beauty of the flowers. Most of the genera above cited are found in collections of stove-plants j in their native habitations they are often epiphytic. COLUMELLIACEvE consist of a few species of Mexican or Peruvian plants, which have been supposed to approach Jasminacese, or still more closely to Gesneraceae and Rubiaceae ; but their structure is not well made out. In many respects they are nearly allied to Escalloniece in Saxifra- gacese. They have an adherent calyx, epigynous corolla, two stamens with sinuous anthers, and an inferior 2-celled oVary with numerous ovules. Seeds perispermic j embryo minute. OROBANCHACE^E (BROOM-RAPES) are fleshy herbs destitute of green foliage (root-parasites) j corolla sympetalous ; stamens irregular, hypogynous, didynamous ; the ovary 1-celled, with 2-4 parietal placentas : capsule with very numerous seeds, which are minute, perispermic, with a very small rudimentary embryo. Illustrative Genera : Orolanche, L. ; Laihrea, L. COEOLLIFLOR^:. 325 Affinities, &c. This Order is especially remarkable for the parasitic habit, the fleshy texture, scale-like leaves, and the absence of chlorophyl, in which particulars the plants resemble Monotropaceae ; but these are not characters of ordinal value, and we see them running into the nearest allies of this group, as Kuehnera and ^trie/a in Scrophulariacese, not to mention the partially parasitic condition of Melampyrece. The Order is chieliy separated from Scrophulariacete by its parietal placentas. From Gentianaceae it differs in the carpels being placed back and front, + , as in O Scrophulariaceae and the allied Orders, while in Gentianaceae they are right and left of the axis, o+O- From Gesneraceae there is little except the habit to separate them. These plants are parasitic on the roots of many herbs and shrubs of very various orders j they attach themselves immediately after germination, and become organically grafted ; some in- crease by tuberous buds from the base of the annual stems. The Oro- banchaceae are bitter and astringent, and are said to be escharotic ; these qualities probably depend on a resinous fluid secreted in the abundant epidermal hairs. They are comparatively numerous in Europe, North America, North Asia, and the Cape j some in India. SCKOPHULAEIACE.E. Coh. Personales, Benth. et Hook. Diagnosis. Chiefly herbs ; flowers with hypogynous, sympeta- lous, irregular corollas, the lobes of which are imbricate in aestiva- tion; didynamous, diandrous (or very rarely 5 perfect) stamens springing from the tube of the corolla ; ovary 2-ceJled, cells antero- posterior ; fruit a 2-eelled, mostly many-seeded capsule with axile placentas ; seeds anatropous ; embryo small, in copious perisperm. Character. Thalamus flat, oblique, or provided with annular disk or gland. Calyx persistent, more or less deeply 3-5-toothed, more or less irregular. Corolla sympetalous, irregular ; the tube long or short ; the limb more or less deeply 5-lobed, or 4-lobed by the coherence of the 2 posterior petals, personate (fig. 422), bilabiate, rotate (fig. 421), sometimes spurred. Stamens 2, 4, and didyna- mous (fig. 425), or with the 5th (posterior) perfect, sterile, or represented by a petaloid tooth (fig. 423), attached to the corolla ; anthers 2-celled, or 1-celled by confluence or by suppression. Ovary 2-celled, with axile placentas bearing usually numerous ovules ; style and stigma simple, or bifid at the apex. Fruit capsular, rarely baccate, 2-celled, dehiscing by 2 or 4 valves, or by pores, or inclehiscent ; seeds mostly numerous, peri- spermic. 326 Fig. 421. SYSTEMATIC BOTANY. Fig. 423. Fig. 425. Fig. 422. Fig. 424. Fig. 421. Corolla and stamens of Veronica. Fig. 422. Calyx and corolla of Antirrhinum. Fig. 423. Corolla, laid open, with didynamous stamens and staminode, of Scrophularia. Fig. 424. Diagram of flower of Scrophularia. Fig. 425. Didynamous stamens of Digitalis, ILLUSTRATIVE GENERA. This large Order exhibits considerable variety of conditions, whence its affinities become somewhat complex. It is by Bentham and Hooker divided into three Suborders or Series, thus : 1. PSEUDOSOLANE^. Leaves alternate ; inflorescence centripetal, two pos- terior lobes of corolla outside. Verbascum, L. 2. ANTIRRHINEJE. Leaves sometimes opposite ; irflorcscence centripetal. Corolla bilabiate, imbricate in (estivation, the posterior lobe outside the anterior one. Calceolaria, Feuill. ; Linaria, L. ; Antirrhinum, L. ; Scrophularia, L. ; Gratiola, L. 3. RHINANTHEJS. ^Estivation imbricate, the two lateral lobes or one of them placed outside. Digitalis, L. ; Euphrasia, L. Affinity, &c. The near connexion with Solanacese, shown in the close relationship between Salpialossis and Petunia, is mentioned also under that Order, where a reference is made to the proposed transfer of the Salpiglossida to the Order Atropacese of Miers. Mr. Bentham defines the present Order by referring to Solanaceae the genera which have at once 5 stamens and a corolla plaited in aestivation ; Petunia has a plaited corolla and 5 stamens, which, however, are unequal and declinate, and thus approach to Salpinlossis, where the corolla is very similar, but the stamens truly didynamous. Verbascum. having 5 stamens, is sometimes referred to Solanaceae ; but one at least of the stamens is commonly sterile, and its corolla is imbricated. In another direction, Scrophularia cese approach some of the forms of the very heterogeneous Loganiaceae ; and Beutham regards it as advisable to refer Budctteia and its allies, generally COEOLLIELOKJi. 327 counted among Scrophulariacese, to that Order, as the only means of setting a definite boundary between the Orders, these genera having a transverse ridge connecting their opposite leaves an indication of the characteristic interpetiolar stipules of Loganiaceae. With Orobanchacese, again, the connexion is close, especially through the root-parasitism of many genera, all of which approach closely in the general structure of the flower to Orobanche ; for the carpels are really anterior and posterior in that Order as they are here, and the main distinction is, that the margins are not folded-in to form a dissepiment, so that Orobanchaceee have pa- rietal instead of axile placentation, to which is added their minute rudi- mentary embryo. A general resemblance exists between the present Order and the other didynamous gamop^etalous Orders ; but Gesneracese, Pedaliaceae, and Crescentiaceae have parietal placentas ; Bignoniaceae and Acanthac'eae have aperisperniic seeds, and Lentibulacese a free central placenta. The morphology of the corolla in this Order is well deserving of atten- tion : curious monstrosities not unfrequently occur in cultivation, in which the normal irregularity is obliterated by a repetition of the pouches, spurs, or similar developments in each constituent petal, as in Linaria^ where a 5-spurred corolla occurs with a symmetrical limb (Pelorian variety) in this instance the regularity is due to the increased number of the usually irregular parts ; in other cases the flower becomes perfectly regular -by the complete absence of pouches and spurs. Calceolaria sometimes occurs with a somewhat campanulate, regular corolla, c. Many of the Scro- phulariacese are parasitic upon the roots of other plants, as, for example, Melampyrum, Rhinanthus, and their allies, which, however, appear to be only partly nourished in this way, having distinct roots ; they are remarkable for turning black when dried ; Btriga, an exotic genus, is still more distinctly parasitical ; and Buchnera hydrabadensis has scale- like leaves similar to those of Orobanche. In some of the genera (Mimtdus &c.), where the style is divided at the apex, it is developed into two flat laminae, which exhibit irritability. Chatin says that the stamens appear simultaneously, and that it is only after birth that the irregularity in number and form becomes manifest ; but that does not accord with our observations. The probability is that the development varies in different genera. Pentstemon heterandrum has the fifth stamen antheriferous. Distribution. A very large group, the species of which are universally diffused and very abundant. Qualities and Uses. More or less acrid, or bitter ; mostly unwhole- some ; sometimes deadly poisons. Digitalis purpurea, our native Fox- glove, the officinal plant, is an extremely powerful sedative poison, both in the foliage and the seeds ; the allied species D. lutea, ochroleuca, Iceviyata, &c. are equally active. The species of Verbascum have a share of this property, especially in the seeds. The Scrophvlarue, Linarice, and Veronica are all more or less bitter and acrid, and suspicious ; Gratiola is violently purgative and emetic. This Order is remarkable for the number of beautiful flowering herbs it contains. The Snap-dragon, or Dragon's-mouth (Antirrhinum maju*), the species of Veronica, Mimulus (of which the Musk-plant, M. moschatus, is remarkable, among plants of this order, for its fragrance), Linaria, Pent- stemon, Calceolaria, Maurandya, &c. are in eveiy garden ; and of their 328 SYSTEMATIC BOTANY. numerous exotic allies a long list will be found in all horticultural col- lections. A large number of showy-flowered native weeds belong to this Order, such as the Toad-flax (Linaria vulgaris) and several other species of Linaria, the Speedwells (Veronica), the Red Rattle (Pedicularu) and the Yellow Rattle (Rhinanthus) (so called from the ripe seeds rattling in the dried inflated membranous capsules), the Foxglove, Mulleins ( Ver- bascum), &c. LENTIBULARIACE^E (BUTTEB-WORTS) are small herbs growing in water or wet places ; flowers with a 2-lipped calyx and a 2-lipped personate spurred corolla ; stamens 2, with (confluent) 1-celled anthers ; ovary 1-celled, with a free central placenta bearing several anatropous seeds, with a thick straight embryo and no perisperm ; stigma bilabiate. Illustrative Genera : Utricularia, L. ; Pinguicula, Tournef. Affinities, &c. This Order is interesting both from the habit and appear- ance of the plants and from its affinities : on the one hand with the irre- gular, didynamous gamopetalous Orders, through Scrophulariaceae, Fig. 426. Fig. 427. with which it agrees in the calyx, corolla, and stamens, and on the other hand with the regular Sympetalse, through Primulacese, with which it is connected by the free central pla- centa. Dickson says the thalamus in development begins to show irre- gular growth before there is any Fi g . 425. Flower of Utricularia. appearance of the parts of the flower, Fig. 427. Air-sac of the leaf of Utricularia. and that the pistil is 5-carpous ; the embryo is sometimes mono- ID other species dicotyledonous. The structure of the leaves of the Utricularice, especially that of their pouches or air-floats (fig. 427), is very curious. Pringsheim considers these pouches to be dilatations of a branch. The plants are found in all parts of the globe ; the Utricularia are aquatic, one curious Brazilian species ( U. nelumbifolia] growing in the water retained in the axils of the sheath- ing leaves of a Tillandsia. In Utricularia the radicle aborts and the adult plant is rootless ; the submerged capillary branches have often been mis- taken for leaves or roots. The pitchers of Utricularia and the leaves of Pinguicula have alike the property of dissolving and absorbing animal matter, such as insects, &c. PingmculfZ are bog-plants ; and P. vulgaris is said to have the property of coagulating milk. Division III. Apetalae or Incomplete. Dicotyledonous plants with a green or coloured calyx and no petals, or with a calyx-like perianth of more than one whorl, or with the floral envelopes reduced to one or more bract-like pieces, or altogether absent. Flowers often unisexual. Exceptions, &c. The above characters are more or less artificial, and INCOMPLETE. 329 bind together a rather heterogeneous series of orders. Many of them are merely degraded forms of Thalamifloral or Calycifloral types. The group is sometimes divided into two subdivisions, called Monochlamydeae and Achlamydeae, according as there is or is not a true calyx or perianth sur- rounding the stamens and pistil. A double floral envelope occurs in some Euphorbiaceas, Loranthaceae, &c. Many of the plants in this group have unisexual flowers grouped in cones or catkins. Series 1. SUPERS. Ovary superior ; perianth usually distiuct. POLYGONACE.E. THE SORREL ORDER. Coh. Chenopodiales, Benth. et Hook. Diagnosis. Herbs with alternate leaves, mostly furnished with stipules in the form of sheaths (ocrece) above the swollen joints of the stem ; the flowers mostly perfect, with a more or less persistent perianth ; stamens hypogynous, or rarely perigynous ; a 1-celled ovary bearing 2-3 styles or stigmas, and a single erect orthotropous ovule ; fruit a triangular nut enclosing 1 erect seed, usually with farinaceous perispermaudan inverted embryo. Illustrative Genera : Eriogonum, L. C. Hich ; Rheum, L. ; Polygonum, L. ; Coccoloba, Jacq. ; Rumew, L. Affinities, &c. The commoner plants of this Order may be distinguished by the peculiar ocreaceous stipules (tig. 65), which, however, are wanting in Erioc/onum and some other genera ; the most distinctive character- istic is the solitary erect seed with its embryo having the radicle turned upward ; this separates it from its near allies, the Chenopodiaceae and Amarantaceae, from which also the perianth and the ocreae remove it; also from the Nyctaginaceae, to which the involucrate flowers and abortive stipules of Eriogonece approach. There is a further relation to Caryo- phyllaceae through the Paronychiaceae. The Order is divided into tribes according to the bi- or unisexual flowers, the presence or absence of an involucre, the number of the parts of the flower, the presence of an ocrea, &c. Distribution. A large Order, the members of which are universally diffused ; especially abundant in temperate climates. Qualities and Uses. The foliage of these plants is frequently charac- terized by the presence of an acid juice, depending on the presence of oxalic and malic acids, or by an acrid, pungent juice ; some are strongly astringent, while the roots are generally more or less powerfully purgative ; the starchy perisperm of the seeds is sufficiently abundant in some species to furnish a valuable substitute for corn. Among the useful acidulous kinds are the garden Rhubarb, Rheum wndtdatum, R. palmatum, &c. ; the Sorrels (JRumex scutatus, R. Acetosa, and R. Acetosella) are familiar plants. Rheum Ribes is used for flavouring sherbet in the East ; and some other exotic plants have like properties. Polygonum Hydropiper, a common native 330 SYSTEMATIC BOTANY. weed, is very acrid, even vesicant when fresh. P. Bistorta was formerly in use as an astringent ; and Coccoloba uvifera, the sea-side Grape of the West Indies, furnishes a very astringent extract. The Rhubarb of medi- cine consists of the roots of Rheum officinale, and perhaps also of palma- tum, undulatum, rhaponticum, Einodi^ Webbianum, and other species ; the roots of Rumex alpinus were formerly used as a purgative under the name of Monk's Rhubarb. Fagopyrum escukntum, common Buck-wheat, F. tataricum, and other species are largely cultivated for food in the northern parts of Asia and of Eastern Europe. The common Docks are species of Rumex. NYCTAGINACE^E (THE MARVEL-OF-PERU ORDER) consists of herbs, shrubs, or trees, mostly with opposite and entire leaves ; stems tumid at the joints ; flowers surrounded by an involucre, with a delicate, tubular or funnel-shaped petaloid perianth ; upper part deciduous, lower part persistent, constricted above the 1-celled, 1-seeded ovary, and indu- rated to form the pericarp (diclesium) ; stamens 1 or several, slender, hypogynous ; the embryo coiled round the outside of the mealy perisperm, with broad foliaceous cotyledons and an inferior radicle. Illustrative Genera : Boerhaavia, L. j Mirabilis, L. ; Pisonia, Plum. Affinities, &c. The nearest relatives of these plants are probably the Polygonaceae, especially the tribe of Eriogone-ce ; but the inferior radicle and the peculiar fruit enclosed in the indurated base of the perianth are evident distinctions. The stems of these plants, especially of the Pisonice, have a curious arrangement of their fibro-vascular bundles. The nature of the involucre serves to divide the Order into tribes. Distribution. Natives of warm climates, chiefly in the S. hemisphere. Qualities and Uses. The roots of the Nyctaginaceae are generally pur- gative ; and Mirabilis Jalapa was formerly supposed to be the source of medicinal Jalap. Mirabilis dichotoma, the Marvel of Peru of our gardens, is remarkable for opening its flowers in the afternoon, whence it is termed the Four-o'clock Plant ; both this and M. lonyiflora, another cultivated species, are violent purgatives. Bougainvillea is remarkable for its brightly- coloured bracts. AMARANTACEJE (AMARANTHS) are weedy herbs, with opposite or alternate exstipulate leaves, and spiked or capitate, bracteated inflores- cence ; the flowers mostly with an imbricated perianth of dry and scarious persistent bracts, often coloured, 3-5 in number ; occasionally unisexual ; stamens 5-merous, hypogynous ; anthers sometimes 1-celled ; the one- celled ovary usually 1-ovuled, in one tribe (Celosiese) many-ovuled ; style 1 or ; stigma simple or compound ; fruit a utricle, a caryopsis, or a berry ; seed pendulous, with the embryo curved round the circumference of farinaceous perisperm ; the radicle near the hilum. Illustrative Genera : Celosia, L. ; Amarantus, L. ; Achyranthes, L. ; Gomphrena, L. Affinities, &c. No absolute character can be given to separate this Order from the Chenopodiaceae ; but the habit, especially the crowded bracteated inflorescence and the membranous perianth, renders them very different in appearance. Their more distant relations are the same as those of that Order. The division into tribes depends upon the 1- or 2-celled anthers and the number of ovules in the ovary. INCOMPLETE. 331 Distribution. A large Order, the species of which are most abundant within the tropics, in dry, barren situations. Qualities and Uses. C4enera]ly with somewhat mucilaginous juice, seldom with active properties. The species of Amarantus, such as A. cau- datws, Love-lies-bleeding, and A. hypochondriacus, Prince 's-Feathers, are well known in gardens for their bright-coloured and persistent blossoms as are also the more tender Globe Amaranthus (Gomphrena) and the Cock's-comb (Celosia cristata), the latter remarkable for its fasciated flowering-stem. CHENOPODIACE^E. THE SPINACH OBDEE. Coh. Chenopodiales, Benth. et Hook. Diagnosis. Chiefly herbs, of weedy aspect," more or less succu- lent ; leaves mostly alternate ; without stipules or scarious bracts ; flowers perfect, polygamous or diclinous, minute, greenish, the free perianth imbricated in the bud ; stamens as many as the perianth-lobes, or rarely fewer, and inserted in front of them or on their bases ; ovary 1-celled, becoming a 1-seeded thin utricle or an actinium ; embryo coiled into a ring (around the perisperm when present) or spiral. Illustrative Genera : Salicornia, Tournef. : Atriplex, L. ; Blitum, L. : Beta, Tournef. ; Chenopodium, L. ; Sal- sola, L. Affinities, &c. Closely related to Amarantaceae, but differing in habit and in the sum of the characters. From the Phytolaccacese they differ in the simple ovary and the stamens equal in number and opposite to the segments of the perianth ; from Scleranthece they are separated by the simple ovary, the usually alternate leaves, and the distinctly hypogynous condition of the stamens : from the Paronychiece particularly by the ab- sence of stipules ; through the Paronychiaceae they are nearly related to Caryophyllacese. The order is divided into two groups according as the embryo is annular or spirally coiled. Distribution. A large Order, generally diffused in waste places or in salt marshes ; most abundant outside the tropics. Qualities and Uses. Generally bland and innocuous, the foliage often rendering them valuable as pot herbs, and their roots furnishing food for cattle ; sometimes with anthelmintic and antispasmodic properties. The maritime kinds were formerly of great value from the quantity of soda obtained from their ashes. Spinach (Spinacia oleracea), Orach (Atriplex hortensis), and English Mercury ( Chenopodium Bonus Henricus) belong to this Order ; also the Beet and Mangold Wurtzel (Beta mdyaris and Cycla). From the juice of the Beet, sugar is extracted in considerable quantities. Chenopodium anthelminticum yields an essential oil, used as an anthelmintic under the name of Worm-see'd Oil ; C. ambrosioides and Botrys also have an aromatic, antispasmodic essential oil; Chenopodium Quinoa forms tubers like potatoes, which are eaten in Peru. Salsola Soda^ Salicornia herbacea, and other species (Glass-wort), with species of Atriplex, Schoberia, &c., 332 SYSTEMATIC BOTANY. abound in salt marshes, and were formerly much used in the preparation of barilla. Several species of Chenopodium and Atriplex abound in waste places, forming 1 , with various kinds of Dock (It/urnex), Polyyonum, and Urtica (Nettle), the most conspicuous weeds of neglected cultivated ground. BASELLACEJE are a small Order of plants closely related to Chenopo- diaceae, chiefly distinguished by the presence of a double, coloured perianth and perigj'nous stamens : they are tropical climbing herbs or shrubs. Some species of Basella are used as Spinach ; Ulluciis tttberosus has a tuberous root, used in Peru like the Potato. PHYTOLACCACEJE proper are nearly connected with Polygonaceae and Chenopodiaceae, differing from both in the frequent presence of petals and of a number of carpels, from the former also in the absence of stipules, from the latter in the stamens exceeding the lobes of the perianth. Phy- tolaccefs pass into Petiveriece by the occurrence of 5 separate carpels in Giesekia, while Rivinia has little perisperni ; the Petiveriece would then connect this Order with the Sapindaceae and their allies, while the columella of the Gyrostemonece would mark a distant affinity with the Malvaceae. A small Order, scattered in all parts of the world, with properties more or less acrid, purgative, or emetic. PABONYCHIACEJE, sometimes placed in this group, are treated of pre- viously near Oarophyllaceae. PETIVEBTEJE, separated by some authors, have stipulate leaves, single ovary, aperispermie seeds, and a straight embryo with convolute coty- ledons; and GYROSTEMONE^E have exstipulate leaves, unisexual flowers, the carpels arranged round a columella, twin suspended ovules, peri- spermic seeds, with a hooked embryo having linear cotyledons, and an inferior radicle. The last two orders are included under Phytolaccaceae by Le Maout and Decaisne. LAURACE^E. THE LAUREL OKDEE. Coh. Laurales, Benth. et Hook. Fig.^428. Diagnosis. Aromatic trees or shrubs, with alternate simple exstipulate leaves, sometimes marked with pellucid dots, and flowers with a con- cave thalamus, regular perianth of 4-6 coloured sepals, which are barely united at the base, im- bricated in 2 circles in the bud, free from the 1-celled ovary containing 1 or 2 pendulous ovules, and mostly fewer than the stamens ; anthers open- ing by 2 or 4 lid-like valves (fig. 42S) ; fruit a berry or a drupe ; seed without perisperm ; radicle Superior. Stamen"rflaar.. INCOMPLETE. 333 ILLUSTRATIVE GENERA: Cinnamomum, Burm. ; Cfomphora, Nees; Nec- tandra, Rottl. ; Sassafras, Nees ; Tetranthera, Jacq. ; Laurus, Tournef. ; Cassytha, L. Affinities, &c. The peculiar operculate dehiscence of the anthers distin- guishes this Order from most of the allied Monochlamydeous groups: from Atherospermaceae, which share this character, Lauraceas are distinguished by their solitary carpel and pendulous ovules. The Lauracete have also affinities with Myristicacese in the qualities of their products ; hut the structure differs widely. Cassyfha is a remarkable form, having a twining parasitic leafless stem like Cuscuta, bearing true Lauraceous flowers. The inner perianth is developed after the manner of a corolla simultane- ously, the outer successively like a calyx (Payer). In some Laurels, e. g. Oreodaplme, the outer anthers are introrse, the inner ones extrorse. The fruit of some genera is curious, as that of Dehaasia, which is borne upon a thickened peduncle, somewhat like that of Anacardium. The pollen is generally spherical, without pores or bands. The solitary carpel is some- times divided into several compartments by false partitions. The sub- divisions of the Order depend on the habit, position of fruit, number of parts to the flower, unisexuality or polygamism, &c. Distribution. A large Order, principally found in cool situations in the tropics ; one (Lavrvs nobilis) is a native of Europe, and a few of North America. Traces of them in a fossil condition are first met with in Eocene formations. Qualities and Uses. The most marked properties of these plants depend on the presence of aromatic oils and Camphor ; but the bark of some has valuable tonic and febrifuge qualities, the timber of many kinds is valu- able, and the Order affords a number of edible fruits. True Cinnamon is the bark of Cinnamomum zeylanicum ; Cassia-bark is derived from C. Cassia and other species ; many other trees of the Order are noted for the possession of an aromatic bark of similar character, and furnish false Cin namons in South America and other countries. Camphor is produced in the wood, branches, and leaves of Camphora officinarum. and is obtained by dry distillation ; some species of Cinnamomum contain a considerable quantity of this substance. The aromatic fruits of some of the Lauraceae furnish false Nutmegs, the Clove-nutmegs of Madagascar being the seeds of AcjathophyUum aromaticum, the Brazilian Nutmegs those of Crypto- carya moschata, c. The bark of Nectandra Rodi&i, the Bibiri of Guiana (from which Warburg's Fever-drops are made), is said to be a valu- able febrifuge ; the bark of the root of Sassafras officinale is highly esteemed in North America for its diaphoretic powers; Benzoin odo- riferum has similar properties, and the oil of its aromatic berries is stimulant. The fruit of Persea aratissima is the highly praised West- Indian Avocado Pear ; it contains much fixed oil. The' timber of Nec- tandra Rod\(Bi is the Green-heart wood of Guiana, remarkable for its hardness and solidity ; Persea indica furnishes a kind of coarse mahogany in the Canaries. Camphor-wood is sometimes used by cabinet-makers on account of its odour. Lauras nobilis, the Bay-tree or classic or true Laurel, is a native of the South of Europe, and is hardy in the south of England ; its aromatic leaves are used for flavouring confectionary. These must not be confounded with those of the Cherry -laurel, a Prunus, and not a 334 SYSTEMATIC BOTANY. true laurel, and which contain much hydrocyanic acid. A Concrete green oil, called Oil of Bays, is obtained from the true Laurel leaves. The ATHEROSPERMACE^E are trees like Monimiaceae, but with the flowers sometimes perfect, the anthers opening- by lid-like valves, and the perispermic seeds erect ; the nuts are enclosed in the tube of the perianth, and the persistent styles grow out into feathery awns, whence the plants are called Plume-nutmegs. They are chiefly distinguished from Moni- iniaceae by their anthers, which resemble those of Lauraceae, from which they are distinguished by the apocarpous ovaries, the diclinous flowers, and erect perispermic seeds, and are allied to Myristicacese by the dicli- nous flowers and aromatic perispermic seeds. The valvate anthers here, as observed by Dr. Hooker, indicate affinity to Berberaceae rather than to Lauraceae. Two of the genera, Laurelia and Atherosperma, are natives of Australia ; Doryphora is Chilian ; they have fragrant properties, and a decoction of the bark of A. moschata is sometimes used as a substitute for Tea. are sometimes placed in this neighbourhood, but have been treated of formerly (see p. 200). MYRISTICACESE (THE NUTMEG ORDER) are tropical trees with alternate, entire, leathery, exstipulate dotted leaves ; flowers diclinous, apetalous, clustered or racemose ; perianth 3- or rarely 4-fid, leathery, valvate ; stamens of the barren flower distinct or monadelphous ; anthers 3-12, perfect, extrorse ; perianth of the fertile flower deciduous ; carpels solitary or numerous, rarely 2, and distinct ; ovules 1 in each cell ; fruit succulent, containing a seed surrounded by a lobed arillus, and having a small embryo in copious oily-fleshy ruminated perisperm. Illustrative Genera : Myristica, L ; Hyalostemma^ Wall. ; Virola, Aubl. Affinities, &c. The nearest relations of this Order are with the apocar- pous Thalamiflorous Orders, more particularly Anonaceae, with which they agree in the dotted leaves, valvate aestivation, extrorse anthers, apocarpous ovaries and ruminated perisperm ; but the flowers are usually perfect in that Order. The structure of the seeds connects Monimiaceae and Atherosperniaceae with this Order ; but they have opposite leaves, besides other peculiarities. The aril originates both from the hilum and the micropyle. In many points they resemble Magnoliaceae, but differ in the valvate calyx, absence of corolla, monadelphous stamens, solitary carpel and ovule. The resemblance to Sterculiaceae seems to have been overlooked ; nevertheless there are many points of contact between the present family and the tribe Sterculieae, in the apetalous unisexual flowers, the valvate calyx, the monadelphous stamens, the arillate seeds. In their active qualities and habit they somewhat resemble Lauraceae. Distribution. Tropical India and America; most numerous in the former. Qualities and Uses. Aromatic and acrid. The common Nutmeg is the seed of Myristica moschata (Moluccas), Mace being the laciniated arillus surrounding this. Coarse, interior Nutmegs are obtained from M. Otoba in Brazil, M. sjniria in the Indian islands, and others of the INCOMPLETE. 335 numerous American and East-Indian species. TJie bark and the rind of the fruit are acrid. NEPEXTHACEJE are herbs or half-shrubby plants with alternate leaves which, when perfect, have a long stalk terminating in a pitcher with an articulated lid. Morphologically the pitcher is considered to be a dilata- tion of a gland at the top of the midrib of the young leaf. The flowers are dioscious, with a 4-merous perianth ; stamens coherent in a solid column (as in Cytisus} ; anthers about 16, extrorse ; ovary free, 4-angled, 4-celled ; seeds very numerous, attached to the sides of the dissepiments. Embryo in fleshy perisperm. The relations of this Order are at present obscure. Most authors connect them with Aristolochiacese. They are natives of the tropical region of Asia, and one is found in Madagascar, another in the Seychelles. They are cultivated in our stoves on account of their curious and often beautiful pitchers. These latter entrap, dis- solve, and digest insects and other animal matter, their glands containing a digestive ferment capable of acting in the presence of an acid. GYROCARPEJE are usually stationed in this vicinity, but have been already treated of under Combretacege, ante p. 262. THYMELACEvE. THE LACE-BAKK ORDER. Coh. Daphnales, Benth. et Hook. Diagnosis. Shrubs or trees with an acrid and very tough (not aromatic) bark, entire leaves, and perfect flowers, with a regular and simple, usually coloured perianth, bearing ordinarily twice as many stamens as its lobes, free from the 1-celled, 1-ovuled ovary; seed suspended; perisperm none or sparing ; radicle superior. -Illustrative Genera : Daphne, L. ; Pimelea, Banks & Sol. ; Layetta, Juss. ; Hernandia, Plum. Affinities, &c. Among the Monochlamydeous Orders this may be dis- tinguished from Santalaceae by its free ovary ; from Elaeagnaceae by its perfect or polygamous flowers and pendulous seed ; from Lauracese by the longitudinal dehiscence of the anthers ; from Proteacese by its pendulous seeds and imbricated perianth. The flowers are mostly perfect, but poly- gamous in the tribe Hernandiece. The flower-tube is probably of recep- tacular origin. The liber is developed in numerous separable layers in the bark of these plants. The Order is divided into tribes according to the presence or absence of petaloid scales or glands. Hemandiece are by some constituted as a distinct Order, differing from Thymelads in habit, struc- ture of bark, position of styles, and 2-seriate perianth. Distribution. A rather large Order, most abundant at the Cape of Good Hope and in Australia, but found sparingly in all other parts of the world.- Qualities and Uses. The bark is usually acrid, and that of Mezereon (Daphne Mczereum) and other plants is used as a local irritant ; taken internally it is an irritant poison. Daphne Laureola, the Spurge Laurel, another native species, has similar qualities as also D. Gnidium and D. pontica, favourite garden shrubs, and other species. The liber of Layetta lintearia (West Indies) is separable into lace-like laminae, whence it is 336 SYSTEMATIC BOTANY. called the Lace-bark tree, and the liber of some Daphnes furnishes useful fibres, and in other cases is manufactured into paper. The berries of Daphne are poisonous ; but the seeds of Inocarpm edulis are eaten roasted like chestnuts. Daphne, Pimelea, and some other genera include many handsome cultivated plants, the perianth being petaloid. AQTJILARIACEJE are a small group of plants, of tropical Asia, included by some in Thymelaceae, but having a 2-celled ovary, or, if 1-celled, then with 2-3 1-ovuled parietal placentas, and sometimes a 2-valved dehiscent capsule ; one ovule is sometimes abortive ; and the fruit in some cases is an indehiscent succulent berry. The heart-wood of Aquilaria ovata and A. Af/allochum is known as Eagle-wood or Aloes-wood, and contains a resinous matter of stimulant quality. Genera : Aquilaria, Lam. ; Gyri- nopsis, Grertn. EL M AGNACE^E are shrubs or small trees with silvery-scurfy leaves and dioecious or polygamous flowers ; perianth free from the ovary, its tube becoming hard or pulpy, and berry-like in the fruit ; stamens as numerous Its the lobes of the perianth, and alternate with them, or twice as many ; ovary 1-celled, 1-seeded, seed ascending ; embryo straight, with thin perisperm and an inferior radicle. The species are generally diffused in the northern hemisphere, separated from the Thyrnelacese by the ordinarily dioecious structure and the ascending ovule ; Elceaynus, which has perfect or polygamous flowers, forms the link. From Prote- aceae they are separated by the valvate calyx and the indehiscent fruit. The pollen is triangular or ovoid (Mohl). The scurfy scales upon the leaves are elegant microscopic objects. The berries of Hippophae rham- noides, Sea Buckthorn, common on our sea-coast, are sometimes used in fish-sauces, but are said to have narcotic properties. Those of Elceagnm orient alls are eaten in Persia, and those of other species in India. The flowers of some species are very fragrant. Traces of plants of this Order have been seen in Miocene and more recent deposits. PEOTEACE^. Coh. Laurales, Benth. et Hook. Diagnosis. Shrubs or small trees usually with umbellate branches ; leaves hard, dry, opposite or alternate, exstipulate ; flowers usually bisexual, apetalous ; perianth 4-cleft, valvate : stamens 4, superposed to the segments, sometimes partially barren ; anthers opening longitudinally ; ovary single, simple, free, with 1 ovule, or 2 or more ovules in 2 rows, ascending or descending ; seeds without perisperm ; embryo straight ; radicle generally in- ferior. Illustrative Genera : Protect, L. ; Grevillea, B. Br. ; Hakea, Schrad. ; Banksia, L. fil. Affinities, &c. The Order is divided into two tribes according as the fruit is dehiscent or indehisceut. In Bellendena the stamens are free. In INCOMPLETE. 337 Simsia and some other genera the anthers are syngenesious. The ar- rangement of the stigmas and stamens to favour cross fertilization is often very singular. The pollen-brains are usually triangular, sometimes elliptic. The development of the lobes of the perianth is successive, not simultane- ous, hence the perianth may be considered as calycine. The remarkable habit of these plants is a striking characteristic ; and, besides the rigid foliage, we have the valvate perianth with the stamens opposite the lobes, and the radicle pointing to the base of the ovary, to distinguish this Order from the Thymelaceae and nearest Monochlamydeous Orders. The struc- ture of the stomata of the coriaceous leaves is very curious, and presents many modifications. Distribution. A large Order, the species of which are found chiefly at the Cape and in Australia. Fossil Proteads have been found in Eocene beds, and these Dicotyledons are among the first of which traces remain to us. Qualities and Uses. The wood is perhaps the most valuable product of these plants, being^ largely used for firewood where they abound ; some- times it is used for joinery when hard wood is required. The striking character of their evergreen foliage, and the brilliant colours of the heads of flowers, render them great favourites in cultivation, and the genera above cited will be found in most large collections of greenhouse shrubs. Macadamia ternifolia furnishes an edible seed. EUPHOBBIACEJE. THE SPUEGE OEDEE. Coh. Euphorbiales, Benth. et Hook. Diagnosis. Herbs, shrubs, or trees, mostly with a milky acrid juice, and leaves usually alternate and stipulate ; monoecious or dioecious flowers ; perianth various or none ; the fruit of 1-3 or several 1-2-seeded carpels, united round a central column, se- parating when ripe ; embryo straight in perisperm. Character. TTialamus flat or concave, or prolonged. Floivers diclinous, axillary or terminal, sometimes enclosed in a cup-shaped involucre. Calyx inferior, with internal glandular or scaly appendages, sometimes wanting. Corolla, of petals or scales as many as the sepals, or wanting. Stamens definite or indefinite, distinct or monadelphous ; anthers 2-eelled, sometimes opening by pores. Ovary free, sessile or stalked, 1-, 2-, 3-, or many-celled ; styles as many as the cells, distinct or combined, or wanting ; stigmas combined or separate and bifid ; ovules 1 or 2, suspended from the inner angle of each cell beneath a prominent "obturator " or placental outgrowth. Fruit dry, the carpels splitting and separating elastically from the axis, or succulent and indehi- z 338 SYSTEMATIC BOTAXY. scent ; seeds suspended, 1 or 2 in each cell, often with an arillus ; embryo m fleshy perisperm ; radicle superior. This Order is divided by Miiller into two main divisions, according to the^size and breadth of the cotyledons, the number of the ovules the aestivation of the calyx, &c. Baillon divides them according to the num- ber of the ovules in the first instance, the presence or absence of perisperm, the presence of an " obturator " or process of the placenta, the sexual con- dition of the flowers, &c. ILLUSTRATIVE GENERA. Hura, L. Hippomane, Z. Ccelebogyne, J, Sm. Mercurialis, L. Acalypha, L. Affinities, &c As the more familiar forms of this Order are either apetalous, or even destitute of a calyx, it is usuallv arranged among the Monocnlamydew in elementary works ; but a large proportion of the exotic genera have the corolla represented either by scales or petals. -V le common & P ur o es (Euphorbia}, the principal native representatives of the Urder, have a very remarkable inflorescence, or " cyathium," by some considered as a, simWl flniiroT- . +iirugged stump of an old tree, covered by a kind of false bark, which is tes- sellated with large compound angular facets ; its internal substance is eaten by the Hottentots. OECHIDACEJE. ORCHIDS. Coh. Orchidales, Hook. Diagnosis. Herbs, distinguished by their irregular flowers, 6-merous perianth in separate at the base from the ovary ; stamen (1, or very rarely 2) gynandrous, pollen cohering in waxy or mealy masses ; ovary inferior, placentas parietal. Character. Perianth mostly petaloid, adherent, in two circles ; the outer circle of three pieces (sepals), distinct or more or less coherent below, 370 SYSTEMATIC BOTANY. two lateral and one anterior (or posterior when the ovary is twisted); the inner circle of three pieces (petals), or rarely one, alternate with the sepals, two lateral, and one (the labellum) pos- terior (or, by the twisting of the ovary, anterior) (figs. 458, 459 bl, & 462), usually longer and larger than the others, variously Fig. 459. Fig. 458. Fig. 460. Fig. 458. Flower of Orchis, and Fig. 4.59. Diagram of ditto : a, a, a, sepals : b, b, petals ; 6', labellum ; b", spur. Fig. 460. Clavate pollen-mass and caudicle of Orchis. formed, with or without appendages, sometimes divided into 3 regions by contractions, forming Tiypoctiilium (at the base), meso- chilium, and epichilium ; free, or more or less adherent to the column. Stamens gynandrous, the filaments confluent with the style into a column (fig. 463), bearing mostly 1 perfect anther on the side turned away from the labellum, with two lateral processes (abortive anthers), or, rarely, 2 perfect lateral anthers with an abortive process next the odd sepal (Cypripedium) ; pollen pulve- rulent, or in grains, more or less coherent, or in waxy masses which are free or provided with a pedicel or caudicle (fig. 460), which adheres to a gland or glands at the apex or rostellum of the stigma. Ovary inferior, often twisted, 1 -celled, with 3 double parietal placentas bearing numerous anatropous ovules ; style 1, confluent with the filaments into the column, which is sur- mounted by a 3-merous, mucous, discoid stigma facing the la- bellum, its lobes alternating with the lines of placentation ; the lateral lobes usually abortive, but sometimes forming divergent processes, the odd lobe more or less developed into a beak (ros- tellum) bearing 1 or 2 glands. Fruit mottly a capsule bursting by 3 valves, bearing the placentas in the middle, separating from the midribs of the carpels, which remain as an open framework ; PETALOIDE/E. 371 rarely a fleshy indehiscent pod ; seeds very numerous and ex- tremely small, consisting of a cellular nucleus without distinct radicle or plumule, enclosed in a loose membranous or rarely crustaceous testa. The Order has been divided by Lindley, its greatest exponent, into several tribes, according to the number and position of the anthers, the number and nature of the pollen-masses, &c. 1. Anther solitary. A. Pollen-masses waxy. a. No caudicle or separate stigmatic gland . . Tribe MALAXEJE. b. A distinct caudicle, but no separate stigmatic gland EPIDENDREJE. c. A distinct caudicle and stigmatic gland .... YANDEX. B. Pollen powdery, granular, or sectile. a. Anther terminal, erect OPHRYE^E. b. Anther terminal, opercular ABETHUSE^E. c. Anther dorsal NEOTTEJE. 2. Anthers two CYPRIPEDIE.E. Affinities, &c. In the greater part of the genera the Monocotyledo- nous type is departed from in several particulars, as : in a more or less considerable irregularity of the perianth, especially in the condition of the labellum ; in the circumstance that the filaments are confounded with the style into a central organ, prolonged from the inferior ovary, called the column, and that generally 2 out of 6 (at least 3) anthers, are abortive, while the pollen is frequently less developed than usual, the process of subdivision into distinct cells or granules being arrested, so that it remains in compound masses of various degrees of magnitude and of more or less firm and even waxy consistence. In some cases, however, as in Thelymitra, the perianth is almost regular, so as to resemble that of some of the genera of Iridacese ; and in Cypripedi&m we find 2 anthers developed and the rest abortive. Among the other remarkable peculiarities of the structure are processes of various kinds occurring upon the column and labellum, which there is reason to regard as indications of abortions of staminal organs. These have given rise to the opinion that the ele- ments of 2 circles of stamens exist in this Order, of which 5 are usually suppressed, the perfect one belonging to an external circle of 3, while in Cypripedium the 2 which are developed are members of the inner circle of 3, one of which, with the entire outer circle, is abortive. The position of the organs may be thus shown : In the typical flower the arrange- ment would be S . . P . A .-. + . U . ' . In most Orchids the ar- rangement is | S.'.P'.'A * 4- G . . , the dots representing those organs that are present and their relative position, the circles those organs that are suppressed. In Cypripedium the formula is S . . P . A -f- ' (Jf . . These views are supported by numerous exceptional in- stances, in which some or all of the ordinarily suppressed stamens are present, and by the anatomical construction, which reveals the existence of as many bundles of vascular tissue in the column and ovary as there are stamens and carpels. Thelasis has normally three stamens. The suppression of 2 out of 3 stamens connects this Order with Marantaceae and Zingiberaceae, where the same phenomenon exists in a different modi- 2 B2 372 SYSTEMATIC BOTANY. fication, as mentioned under those Orders; the Apostasiaceas have 2 stamens only, with their filaments adhering to the lower part of the style. The ovary is apparently formed of 3 carpels, with the stigmas simple. Since they alternate with the placentas, Lindley supposes the ovary to be formed of 6 carpels, 3 fertile and 3 barren ; but this seems contrary to analogy and without sufficient independent support. In Apostasiacete, Marantacese, and Zingiberaceae the ovary is 3-celled, or sometimes imper- fectly so in the last, from the margins not meeting in the centre. Seleni- pedimn has a 3-celled ovary. The seeds, which are very minute, are of simple organization : the ovules, at the time of fertilization, consist solely of an embryo-sac with 2 integuments ; and the ripe seed presents an embryo devoid of distinct organs (cotyledon and radicle), enclosed in a loose testa in this respect exhibiting a relationship to Burmamriaceae. Fig. 461. Fig. 461. Orchid flower, showing the parts of the perianth and column. Pig. 462. Flower of Drakea : the parts of the perianth are turned back to show the column and the lip, which is jointed in the middle, and endowed with hinge-like motion when irritated ; so that an insect alighting on it is entrapped, and in its struggles to escape removes the pollen-massses. The labeUum sometimes exhibits irritability, moving spontaneously or when touched (Megaclinium^ Bolbophyllum, Drakea, &c.) (fig. 462) : its forms are most varied and strange, often causing the entire flower to re- semble an insect or some other living object. The rostellum and stalk of the pollen-masses are also endowed with contractile properties. In Catasetum these are so powerful as to cause the sudden forcible ejection of the pollen- masses from the anther-cells, when the rostellum or other sensitive organ is touched, as by the proboscis of an insect. Insects visiting the flowers of our common English Orchis, for the sake of the honey, come into contact PETALOIDE^E. 373 with the rostellum, and thus liberate the pollen-masses. These latter adhere firmly to the insect's back by means of a gland at the end of the stalk, so that the pollen-mass is conveyed to another flower. It must, how- ever, be remarked that if the pollen-mass retained the nearly vertical direction it had on its exit from the anther, it would, when introduced by the insect into another flower, strike against the anther, and not against the stiguia. In order to place the pollen in such a position that it shall impinge on the stigma, the caudicle or stalk of the pollen-mass contracts so as to give the pol- len-mass the requisite horizontal direction. This movement can readily be seen by thrusting the point of a pencil into a flower against the rostellum, when the pollen- masses will adhere to the pencil, and may be withdrawn from the anther-case, and, if watched, will be seen to bend down- wards, in the manner just described, im- mediately after their 'removal from the anther (fig. 464). These movements will be again alluded to in the physiological portion of this work. Fig. 464. Fig. 463. Column of Vanilla from the front and from the side, the parts of the perianth cut away : o, the anther ; r, the rostellum; the 2 points to the stigma. Orchis pyramidalis ; a, pollen-mass just removed from the anther, vertical ; b, pollen-masses divergent and horizontal. Two distinct forms of the perianth sometimes present themselves on the same flower-spike, so that the same species has received two specific titles, and even three distinct generic names : e. g., Monachanthus, Myanthus, and Catasetum, now all included in the last named genus, and Cycnoches ventricosum and JEyertonianum, now known to be forms of one and the same species. This was considered a most anomalous circum- stance till it was shown by Darwin that the different forms represented different sexes, the male flowers being different from the female. The OrchidacesB are terrestrial in temperate climates, forming subter- raneous tubers or tuberously enlarged fibrous roots, from which the flowering-stern shoots up afresh every season. In warm and moist climates they are very frequently epiphytic, hanging on the branches of trees, or even attaching themselves to rocks and other foreign objects. These kinds generally form some kind of stem-tuber, either from the lower interncdes of the axis which has just flowered, or of a new axis, sometimes from the 374 SYSTEMATIC BOTANY. whole of the interncdes of a long jointed leafy axis, &c. The roots which hang down from them are soft and delicate at the apex ; and the epithelial cells exhibit spiral-fihrous thickening of a peculiar kind. Angrcecum funale has neither true roots nor leaves. Neottia nidus avis has buds on the ex- tremity of the roots (Van Tieghem). Epipocjon Gmelini and Corattorhiza innata are also rootless. The embryo is a mere cellular globule borne on a suspensor. Distribution. Orchids are very numerous, and occur in almost all parts of the globe, except the very coldest or in very dry regions. In tem- perate climates they occur chiefly in shady woods, damp pastures, or open calcareous downs ; but they are most abundant in. damp situations in the tropics. Qualities and Uses. The properties of these plants are generally un- important. The subterranean tubers of some form nutritious food, from the presence of a gummy substance : that of a native species, Orchis mas- culttj was f ormerly coUected and sold for the preparation of Salep ; and other kinds are eaten in India. Some of the South- American yield a kind of vegetable glue ; Aplecti'um hyemale, the North-American Putty-root, is used for making a cement for china. The most important plants, perhaps, are Vanilla planifolia and other species, and a species of Sobralia, the dried pulpy pods of which furnish the Vanilla used for flavouring chocolate and confectionary. A few others are described as having medicinal properties of various kinds. APOSTASIACE^E is a small Order of perennial herbs nearly related to Orchidaceae, bearing a regular perianth and 2 or 3 stamens which are con- fluent by their filaments with the lower part of the style (the anthers free), forming a kind of column, prolonged above into a filiform process with a 3-lobed stigma ; ovary 3-celled, with axile many-seeded placentas ; seeds apparently as in Orchidaceae. These plants differ from Orchids chiefly in the free condition of the upper part of the style and the 3-celled ovary ; but as the latter character is inconstant in some Monocotyledonous Orders, probably this Order should be united with Orchidaceas ; they are near to Burmanniaceae also ; but that Order has free stamens. Lindley regards this Order as connecting Orchidaceae with Amarylhdaceae through Hypox- idaceae. They are natives of damp woods in tropical India, and are with- out known properties. Genera : Apostasia, BL, &c. BURMANNIACEJE are small annual herbs, often with minute and scale- like leaves, or those near the root grass-like ; the flowers perfect, with a 6-cleft petaloid perianth, the tube of which adheres to the 1-celled or 3- celled ovary ; stamens 3, distinct, introrse, and superposed to the inner seg- ments of the perianth, or 6 and extrorse ; stigmas 3 ; capsule many-seeded ; the seeds very minute, with a homogeneous nucleus in a loose membran- ous testa. Natives of the tropics of America, Africa, and Asia. Some are probably parasitical. The affinities of these plants are rather obscure ; they apparently agree with Iridaceae in the character of the flowers, but differ in the position and number of the stamens ; while, by the seeds resembling those of Orchidaceae, they form a connecting link between these two Orders. They are also related through Taccacese to Aristolo- chiacese. They are said to be bitter and astringent, but are unimportant in these respects. Genera : Burmannia, L. ; Thismia, Griff., &c. 375 ZINGIBERACE^E (THE GINGER ORDER) consist of herbaceous perennials with a creeping rhizome ; leaves broad, with a sheathing petiole, and numerous parallel veins diverging from a midrib ; flowers spiked or racemose, with spathaceous membranous bracts; perianth adherent, irregular, in three circles each of three parts, one petal being larger in each of the two inner circles ; stamens 3, distinct, 2 abortive, and the fertile one posterior, opposite the labollum or large segment of the inner- most perianthial whorl ; anther 2-oeliod ; ovary 3-celled, or with the dis- sepiments imperfect ; seeds numerous, often arillate, with the embryo in a sac (vitettus) within the perisperm. Illustrative Genera : Zingiber, Gasrtn.; Amomum, L. ; Hedychium, Kcenig ; Alpinia, L. ; Costus, L. Fig. 465. Hedychium : A, B, loculicidal capsule ; C, seed with arillus ; D, section of seed. Affinities, &c. This Order is nearly related to Marantaceae, Orchidaceae, and the allied Orders, but may always be distinguished by the only fertile stamen being situated next the axis (posterior), not next the bract (an- terior) as it is in Orchidaceae (before the ovary becomes twisted), or lateral as it is in Marantaceae ; the ovary is usually 3-celled, like that of Maran- taceas, but the embryo is contained in a special sac or vitellus, which is not present in the seeds of either Marants or Orchids. Distribution. A large Order, consisting mostly of tropical plants ; the greater part East-Indian, but a few occurring in America, in Africa, and in Japan. Qualities and Uses. Remarkable for the pleasant aromatic and stimu- lant qualities of the rhizomes and the seeds of many kinds ; some are 376 SYSTEMATIC BOTANY. astringent, many yield starch, and some colouring-matters. Ginger is the rhizome of Zingiber offidnale : preserved ginger is made from the younger parts of the rhizomes. Cardamom seeds are obtained from Amomum Cardamomum (Round Cardamoms), A. angustifolium (Madagascar Car- damoms), A. maximum, A. aromaticum, Elettaria major (Ceylon), and E. Cardamomum (Malabar). Turmeric consists of the yellow-coloured rhi- zomes of Curcuma lonf/a ; the starchy rhizomes of some East-Indian species of Curcuma furnish Arrow-root. Galangale-root, which has pro- perties resembling those of Ginger, consists of the rhizomes of Aljnnia Galanga and racemosa ; Zedoary, of those of Curcuma Zedoaria and Zerumhet. Amomum Grana Paradisi yields the Grains of Paradise, used as stimulants, and also for giving pungency to spirits and beer. Many of the species have very beautiful blossoms, and are cultivated in stoves on that account. The bright colouring is found sometimes in the bracts, sometimes in the perianth, as in Hedychium coronarium. MAKANTACE^E. THE ARROWROOT ORDER. Coh. Amomales, Benth. et Hook. Diagnosis. Herbaceous plants with creeping rhizomes, resembling ZingiberaceEe in habit, but with the perianth more irregular, and the inner segments often abortive ; of the 6 stamens 5 are petaloid, and 1 lateral fertile 2-lpbed, with a 1- (2 ?)-celled anther on one of its lobes; ovary inferior, 1-3-celled, with numerous perispermic seeds; embryo not enclosed in any special sac. Illustrative Genera : Maranta, Plum. ; Canna, L. Affinities, &c. The affinities of this Order, often called Cannaceae, are those of Zingiberaceae, from which this Order is separated by the place of its fertile stamen (lateral) and by the absence of a vitellus or special sac Diagrams of the flowers of Marantaceae (M), Zingiberacese (Z), and Orchidacefe (0). The small open circles are fertile stamens ; the black dots abortive stamens ; the black dots with the broad line scored through are petaloid stamens. The X indicates the position of the axis, the bract being exactly opposite. round the embyro. If we assume the Orchidaceaa, as mentioned under that Order, to have the rudiments of a double series of stamens, the rela- tions of Orchidaceas, Zingiberaceaa, and Marantaeeaa are very close, and yet their distinctions very clear (fig. 4(36). PETALOIDE^E. 377 Orcliidaccce, with a double perianth and two circles of stamens, have the anterior stamen (belonging to the outer circle) developed, the rest abortive, or present in the form of horns, .ridges, &c. (O) ; or, in Cypri- pedium, they have the two lateral stamens of the inner circle developed, the anterior and all those of the outer circle abortive. Zingiberacefs, with a double perianth, have the outer circle of stamens petaloid, forming a third perianthial circle, the odd (posterior) stamen of the inner circle developed, the 2 lateral abortive (Z). Marantacese, with a double perianth, have the outer circle of stamens more or less developed in a petaloid form, as a third perianthial circle, and one lateral stamen of the inner circle fertile the other lateral stamen, with the posterior one, being abortive (M). Dr. Dickie has lately shown that the anther of Canna is in reality 2-celled. Eichler gives a different explanation of the flowers of these plants. According to him the flower of Canna consists of 5 ternary verticils alterna- ting one with another, the two outer constituting the perianth, the two fol- lowing ones the androecium, and the last the pistil. The perianth and pistil are complete, but the outer whorl of the androecium is completely sup- pressed, as is also one stamen of the inner whorl. Of the two remaining stamens of this inner whorl, one has half an anther only, the other is entirely petalodic. This second whorl of the andrcecium also furnishes accessory appendages of different shapes in various genera. In Zingi- beraceee the outer whorl of stamens is suppressed, but the inner whorl is complete, though there is only one perfect stamen, and this has two anther- lobes. In Musaceae the inner row of the androecium is complete, and only one member of the outer one is deficient. In Cypripedium there is one member of the outer row present as a staminode and two of the inner. In Xyridese, Burrnanniaceae and some Eriocaulons, the inner whorl is complete and perfect. In Irids, Grasses, and most Orchids the inner whorl Distribution. The species are numerous, and natives chiefly of tropical America, Africa, and India. Qualities and Uses. The abundance of pure starch furnished by the rhizomes of many species constitutes the principal feature of the Maran- taceae considered from an economical point of view. True Arrowroot is obtained from Maranta arundinacea, Allouyia, and nobilis (West Indies), and M. ramosissima (East Indies). Tous-les-Mois is derived from species of Canna, probably C. coccinea, Achiras, edulis, &c. Canna indica is called " Indian shot," from its beautifully spherical seeds. Some of the species are cultivated in our stoves. Many of the species of Calathea and Maranta have beautifully coloured foliage. MUSACEJE (BANANAS) are large herbaceous plants with long sheath- ing petioles forming a spurious stem ; leaves large, with a strong midrib and parallel lateral veins ; flowers enclosed in a spathe, hermaphrodite ; perianth more or less irregular, adherent, petaloid, in two 3-merous rows ; stamens 6, on the segments of the perianth, some always abortive ; anthers 2-celled ; ovary 3-celled, many-seeded, or rarely 3-seeded ; fruit a capsule or succulent and indehiscent ; embryo at the end of perisperm. Illustrative Genera : Jleliconia, L. ; Musa, Tournef . ; Strelitzia, Banks ; Mavenala, Adans. 378 SYSTEMATIC BOTANY. Affinities, &c. With certain well-marked differences, these plants ap- proach in some degree to the Marantaceee and Zingiberaceae in habit, espe- cially in the character of the foliage, but the Musaceae have 5 or 6 more or less perfect stamens and no staminodes ; from the Amaryllidaceae, which they resemble in the epigynous hexandrous structure, they differ in the irregular flowers, the general habit, and the character of the bracts or spathes. Distribution. A small Order, the species of which are generally dif- fused, wild or in culture, in the plains of the tropics and subtropical regions of the globe. Qualities and Uses. These plants are most valuable as sources of food and fibrous materials. Musa paradisiaca, the Plantain, and Musa sapientum, the Banana, are plants bearing gigantic leaves on long petioles, the im- bricated sheaths of which form a pseudo-stem many feet high. They produce large clusters of pulpy fruit containing much sugar and starch, which form a very important article of food in the tropics. Several other species of Musa yield similar fruits. The leaves are used for thatching huts, or split up for plaited work of all kinds. The fibre of the petioles is a valuable material, especially that of Musa textilis, which is known as Manilla Hemp. The young shoots are also eaten boiled. Ravenala speciosa has an edible seed ; a quantity of watery juice exudes from its petioles when cut, whence it has been called Arbre du voyageur. Stre- litzia is a genus with very handsome flowers, several species of which, as also of Musa, are often cultivated in stoves. AMAETLLIDACE^E. AMAEYLLIDS. Coh. Narcissales, Hook. Diagnosis. Chiefly bulbous and scape-bearing herbs, not scurfy or woolly, with linear flat root-leaves, and perfect, regular (or nearly so), 6-androus flowers ; perianth petaloid, 6-parted, its tube inseparate from the 3-celled ovary ; the segments of the limb imbricated or valvate in aestivation ; anthers introrse ; fruit a 3-valved, loculicidal capsule or a 1-3-seeded berry ; seeds with fleshy or horny perisperm ; radicle turned to the hilum. Illustrative Genera : Tribe 1. AMARYLLEJE. Bulbous plants, without a coronet. Galanthus, L. ; Amaryllis, L. Tribe 2. NARCISSE^E. Bulbous plants, with a coronet in the perianth. Pan- cratium, L. ; Narcissus, L. Tribe 3. ALSTR (EMERIES. Fibrous-rooted; no coronet. Alstrcemeria, L. Tribe 4. AGAVES. Fibrous-rooted ; sepals and petals alike, valvate in aestivation ; no coronet. Agave, L. ; Fourcroya, Vent. Affinities, &c. The floral formula may be represented as follows : | P3_j_3 A 3+3 G 3. This epigynous Order contrasts with the hypo- gynous Liliacese ; among its epigynous allies, Iridaceae are distinguished by their 3 stamens and extrorse anthers : its nearest allies are Haeniodo- raceaa and Hypoxidaceae, the characters of which are given elsewhere. The coronet of the Narcissece is sometimes regarded as a circle of abortive stamens, but is more probably an outgrowth from the tube of the perianth. PETALOIDE^E. 379 Distribution. A large Order, the species of which are generally diffused, but which, like Iridaceae, have their maximum at the Cape of Good Hope. The Narcissea are common in Europe, while the genera unprovided with a coronet are very rare in Europe and North America, but abound in South Africa. Qualities and Uses. The Amaryllidaceae are commonly characterized by active properties, the Amaryllece and the Narcissece especially being- emetic and purgative, and even poisonous; the juice of the bulb of JLcemantlius toxicarius is used by the Hottentots to poison arrows. The Snowdrop (Galanthus nivalis), Snowflake (Leucojum vernum), the Daffodil (Narcissus Pseudo-Narcissus}, with the other cultivated Narcissi, Pancratium maritimum, &c. ; act as emetics. Others are astringent ; but starch is washed from the roots of some species of Aktroemeria. The Agaves are exceedingly valuable plants, having abundant innocuous sac- charine sap, and large leaves containing excellent fibre. Ayave americana, called by mistake the American Aloe, is the Hundred-years plant ; but the statement that it lives 100 years before flowering is fabulous : it is a native of America, but is naturalized in some parts of S. Europe, and is planted, on account of its large spiny leaves, to form fences. From this and other species is obtained Pira thread, a valuable fibre ; Pulque (a fermented liquor) and a brandy distilled from this are made by cutting the buds out of ^aye-plants and collecting the sap, which exudes in great abundance when this operation is performed just before the flowering stem is pushed out ; these plants are also called Maguey-plants. This Order affords a number of beautiful flowers, more permanent than Irida- cese, and often attaining a very large size. Most of them are annual flowerers ; but the Ayavece, having remarkable foliage, like that of the Aloes in Liliacea3, produce flowering stems (sometimes many feet in height) after vegetating for a number of years, whence the story of the Hundred-years Aloe. Sternberyia lutea is supposed to be the Lily of the fields referred to by Christ. HYPOXIDACE^E are a small Order of epigynous Monocotyledons, nearly related to Amaryllidacese, but differing in their habit, having hairy foliage and no bulbs, and in their usually strophiolate seeds having the radicle distant from the hilum. The 6 stamens, the imbricated, distinctly petaloid perianth, and the habit of the foliage separate them from Iridaceae. They occur scattered in the warmer parts of the globe, and are apparently more or less bitter and aromatic. The tubers of some are eaten. Genera : Curculiyo, Geertn. ; Forbesia, Eckl. ; Hypoxis y L. j Sauridia, Harv. HJEMODORACE^: are herbs with fibrous roots, usually equitant leaves, and perfect 3-6-androus regular flowers, which are woolly or scurfy outside ; the tube of the 6-parted perianth adherent to the whole surface, or merely to the lower part of the 3-celled ovary ; anthers introrse ; sta- mens superposed to the petals when 3 j seeds with cartilaginous perisperni ; radicle remote from the hilum. The structure of the genera included in this Order is rather irregular: from Amaryllidaceee they are usually distinguished by the woolly tubular perianth, the equitant leaves, and, in some cases, by the 3 stamens ; but none of these characters are without 380 SYSTEMATIC BOTANY. exception ; from Iridaceae the triaiidrous genera differ in the stamens being introrse and superposed to the petals, which last character also separates them from Hypoxidaceae. The radicle is said to be remote from the hilum, as in Hypoxids ; while it is next it in Amaryllids and Irids. The VellozicB and Barbacenia are more or less arborescent, and in some degree branched, especially the former, which have a very remarkable aspect ; in many respects they approach Bromeliads. The plants are natives of America, the Cape, and Australia, and have sometimes bitter and astrin- gent properties, as Aletris farinosa. The roots often contain a red matter available as a dye, whence the name of Blood-roots ; Lachnanthes tinctoria is used in America for dyeing. The roots of several species of Hfsmodorum are eaten, roasted, by the natives of Australia. Genera : Hcemodoruin^ Sm. ; Aletris j L. ; Vellozia, Mart. ; ^Barbacenia, Vandelli. IRIDACE^l. THE FLAG OEDEE. Coli. Narcissales, Benth. et Hook. Diagnosis. Herbs with bulbs, corms, or rhizomes, equitant, 2-ranked leaves, and perfect, regular or irregular flowers ; the seg- ments of the 6-parted petaloid perianth (fig. 467) convolute in Fig. 467. Fig. 468. Fig. 469. Fig. 471. Fig. 467. Vertical section of the flower of Iris : a, inferior ovary. Fig. 468. Stigmas of Crocus. Fig. 469. Loculicidal capsule of Iris burst. Fig. 470. Plan of ditto. Fig. 471. Section of seed of Iris. the bud in 2 circles ; the tube inseparate from the 3-celled ovary ; stamens 3, superposed to the outer segments of the perianth, di- stinct or monadelphous ; anthers extrorse ; style 1 ; stigmas 3 (fig. 468), often petaloid (Iris) ; capsule 3-valved, loculicidal (figs. PETALOIDE^;. 381 469 & 470) ; seeds with horny or hard fleshy perisperm (fig. 471). Illustrative Genera : Iris, L. ; Tiyridia, Juss. ; Gladiolus, Tournef . ; Isria, L. ; Crocus, Tournef . Affinities, &c. The tribes of this Order (!XIEJE, IRIDE^E, and GLADIO- LE^E) are distinguished hy the regular or irregular perianth, the free or in- separate stamens, the filaments equal or unequal in length, the form of the stigma, &c. The floral formula is | P 8+3 A 8 G '6. Among the epigy- nous petaloid Monocotyledons, the Iridaceae approach, by genera like Crocus, the Amaryllidacete, which, however, have 6 introrse stamens. The same character separates the epigynous Bromeliaceae, which have some affinity with this family ; one plant of this Order, Eleutherine anomala, has, however, been described as having six stamens, probably as an accidental occurrence. OrchidaceEe differ in the gynandrous structure; Marantacese and Zingiberaceas in their monandrous state, as also in the character of their foliage. The little Order Burmanniaceae resembles Iridacese in many particulars, but differs in some essential points men- tioned under that order; and this is the case also with Xyridacere. Gladiolus has slightly irregular flowers ; Crocus has quite a regular perianth ; Ins has also regular flowers, the seeming irregularity being dependent on the reflexed petals and the large petaloid styles which conceal the stamens. Distribution. A large Order, diffused throughout temperate and warm climates, but especially abundant at the Cape of Good Hope. Qualities and Uses. The sap of many of these plants is more or less acrid, purgative, or emetic, as that of the Flags (Iris) generally, Ferraria, Sisyrinchium, &c. Saffron consists of the stigmas of the Saffron Crocus (C. sativus) and of C. odorus (Sicily). Orris-root, used in perfumery, is the rhizome of Iris florentina. The genera of this Order contribute a large share to our collections of garden-bulbs, as will be recognized from the plants already named ; they are more remarkable for their beautiful but transient flowers than for any useful quality ; the corms and rhizomes of some are said to be eaten, on accoimt of the starch they contain, by the Hottentots and other races. BBOMELIACEJE. THE PINEAPPLE ORDEE. Coh. Amomales, Hook. Diagnosis. Herbs (or scarcely woody plants), nearly all tropical, the greater part epiphytes, with persistent dry or fleshy and channelled crowded leaves, sheathing at the bases, usually covered or banded with scurfy scales ; perianth free or adherent, in two circles, the outer (sepals) often coherent, and differently coloured from the inner (petals), which are distinct and imbricated; stamens G; ovary 3-celled, with numerous ovules on axile placentas ; style single ; stigma 3-lobed or entire, often twisted ; seeds numerous, with a minute embryo in the base of mealy perisperm ; the radicle next the hilum. Illustrative Genera : Ananassa, Lindl. ; Bromelia, L. ; Mclimm, R. & P. ; Billbergia, Thunb. ; Pitcairnia, Herit. ; Tillandsia, L. 382 SYSTEMATIC BOTANY. Affinities, &c. Among the Bromeliaceae are found "both epigynous and hypogynous genera, as well as forms with a partially adherent perianth ; on the whole, the tendency is to the former condition, whence the Order must be regarded as an ally of Amaryllidacete, from which it differs in habit and in the mealy perisperm ; from Iridaceae it differs in these parti- culars and in the 6-androus stamens, while the style and stigma are somewhat similar. The character of the habit, and the often distinctly characterized calyx and corolla, offer a resemblance to Hydrocharidacese, which, however, have aperispermic seeds. The fruit varies much in this Order, being commonly capsular ; but in Ananassa the entire spike of inflorescence, together with the stem, becomes blended into a succulent sorosis, forming the fruit of the well-known Pine-apple. The scurfy epi- dermis of the leaves displays a very interesting microscopic structure. Distribution A considerable group, the members of which are, for the most part, natives of tropical America ; but some are now naturalized in West Africa and the East Indies. Qualities and Uses. Chiefly important for the fruit of Ananassa, fibres, colouring-matters, and other economic products. JBromelia Pinguin is used as a vermifuge in the West Indies. Many of these plants grow upon the branches of trees (epiphytic), and they appear to be capable of obtaining the greater part of their nourishment from the atmosphere ; their rigid, tough epidermis enables their succulent leaves to withstand the influence of a hot and dry atmosphere. Tillandsia usneoides, called Old-Man's Beard, is a common plant, forming a dense mass of dark-co- loured fibres, which hang down from the boughs of the trees of the forests of tropical America, as Lichens do in colder climates. Most of the genera have brilliantly coloured flowers, sometimes in tall racemes and panicles, whence they are much esteemed as ornamental stove-plants. HYDROCHABJDACE.ZE are aquatic herbs, with diclinous or polyga- mous regular flowers issuing from a spathe on the end of scape-like pe- duncles ; floral envelopes in a single or double circle, in the fertile flowers united into a tube and inseparate from the 1-9-celled ovary; placenta parietal ; seeds without perisperm. Illustrative Genera : Udora, Nutt. ; Vallisneria, Mich. ; Stratiotes, L. ; Hydrocharis, L. Affinities, &c. The sum or combination of the characters of this interest- ing Order keeps it apart from all other Monocotyledons, while the characters taken separately connect it with many. The inferior ovary and, in the case of Stratiotes, the habit connect them with Bromeliaceas ; the 3-merous petaloid flower and aperispermic seeds with Alismacese ; the 3-merous petaloid flower and 3-carpellary ovary with the Oommelynaceae, which, however, with a superior ovary, like the Alismacese, have perispermic seeds. The inferior ovary, numerous seeds, and general characters remove them from Naiadacese, with which they are often associated by habit, and the Aracese, with which some would connect them ; their spathe is scarcely more Araceous than that of AmaryUidaceae. Vallisneria and Elodea (Anacharis) are plants well known "to microscopists for the favourable opportunities they offer of examining the rotation of the protoplasm of the cells. Hydrocharis, a plant somewhat like a miniature Water-lily, is common in fresh-water ditches ; and its sepals and rootlets are equally PETALOIDEJE. 383 adapted for the microscopic investigation of living tissues. Ekdea cana- densis is the American Water-weed, which has increased so rapidly in our canals and ditches since its introduction from America some years since. Distribution. The species are not numerous ; they are found in fresh water in Europe, N. America, E. Indies, and New Holland. Qnaiities nnd Uses. They appear to have no very active properties. Hydrocharis is said to be astringent. Series 2. Flower-tube free from the ovary. A. SYNCARPIJE. Carpels united ; seed usually perispermic. PHILESTACE^E are climbing or erect shrubs with coriaceous, netted- ribbed leaves and large and showy perfect flowers with a C-merous peri- anth in two circles, equal, or the calyx much shorter ; stamens 6, adherent to the perianth at the base ; ovary 1-celled, with 3 parietal placentas ; ovules semianatropous (not orthotropous, as is commonly stated). These plants, consisting of Lcmageria rosea, a climbing shrub with beautiful crimson flowers and basifixed anthers, and Phiksia buxifolia, the flowers of which differ chiefly in the marked difference of calycine and corolline circles and the mode of union of the bases of the filaments and versatile anthers, differ from Liliaceae chiefly in the parietal position of the pla- centas ; in habit Lapayeria is related to Smilax, and is in some measure intermediate between Smilaceae and Liliaceae. They are Chilian plants, now in cultivation with us. Lapageria bears sweet edible berries. ROXBUKGHIACEyE consist of 4 species of Roxlurrjfiia, twining shrubs with broad leathery leaves and tuberous roots, from the hotter parts of the East Indies. Their habit connects them with Smilaceae ; but their perianth is composed of 4 petaloid pieces, and they have 4 stamens with enlarged connectives (each set of organs, according to Griffith, in 2 dimerous circles), and the 1-celled ovary (formed of 1 carpel, according to Griffith) has numerous anatropous ovules arising from the base of the cavity ; the sessile stigma is penicillate. The fruit is 2-valved, with 2 clusters of seeds attached on long cords; embryo in the axis of fleshy perisperm. The affinities of these plants are not clear ; but the resem- blance is perhaps greater to Paris than to any other genus that can be named. SMILACE^E (THE SARSAPARILLA ORDER) consists of herbs or climb- ing shrubby plants with stalked netted-veined leaves, regular perfect or dioecious flowers, with the 6-10-parted perianth of the fertile flowers free from the 3-5- (rarely 1-2-) celled ovary ; stamens 6-10, introrse ; anthers adnate, basifixed ; styles or sessile stigmas as many as the cells of the ovary, and distinct ; fruit baccate, with few or several seeds ; ovules ortho- 384 SYSTEMATIC EOTA1ST. tropous ; embryo minute, in hard fleshy perisperm. Illustrative Genera : Smilax, L. ; Paris, L. ; Trillium, Mill. ; Medeola, Gronov. Affinities, &c. The plants are not separated by any good characters from the Asparageous tribe of the Liliaceee on the one hand, while they pass into Dioscoreaceae on the other, from which they differ chiefly in having a superior ovary. Smilax represents Smilaceae proper ; Paris, Trillium, &c. have the calyx unlike the corolla, and are sometimes made a separate Order, called ^Trilliacese. Distribution. A considerable Order in point of numbers. Temperate parts of Europe, Asia, and America. Many species of Smilax in tropical America and Asia. Qualities and Uses. Smilax has diuretic and demulcent properties, for which the creeping rhizomes of many species are used, iinder the name of Sarsaparilla, as Sm. medica (Vera Cruz), S. Purhampuy (Peru), & syphi- litica (Brazilian), S. officinalis (Jamaica), 8. ylycyphylla (Australia) ; Smilax aspera and excelsa, natives of S. Europe, have similar properties. Smilax China has a fleshy root, said to possess similar properties. S. Pseudo- China is largely used in domestic medicine in the United States. Paris, Trillium, and Medeola are more allied to the active Liliacese in their properties. Paris quadrifolia, a curious herb growing in groves in this country, is said to be a narcotic and poison ; Medeola virginica is emetic and diuretic. The species of Trillium are violent emetics. Rnscus has curiously flattened branches, from the surface of which the flowers proceed. LILIACE^l. LILIES. Coli. Liliales, JBenth. et Hook. Diagnosis. Herbs with parallel-veined, sessile or sheathing leaves, regular perfect 6- (rarely 4-)androus flowers, with the petnloid 6- merous perianth free from the 2-3-celled ovary ; anthers introrse, attached by a point ; style single ; perisperm fleshy. Character. Perianth free, of 6 pieces in 2 circles (fig. 472), distinct or united, mostly of similar colour, and regular. Stamens 6, introrse, springing from the segments of the pe- Fig. 472. rianth. Ovary free, 3-celled; with numerous anatropous or amphitropoas ovules on axile pla- centas ; styles simple ; stigma 3-lobed or un- divided, sometimes sessile. Fruit dry and capsular, loculicidally valvate, or succulent and indehiscent; seeds with the embryo mostly in the axis of fleshy perisperm. Flower of Stiiia. ILLUSTRATIVE GENERA. Tribe 1. LTLIEJE. Anthers introrse; styles united; fruit capsular^ loculi- cidal. Tulipa, L. -, Lilium, L. ; Hyacinthus, L. ; Scilla, L. PETALOIDE^:. 385 Tribe 2. COLCHICEJE. Anthers extrorse ; styles separate ; fruit capsular, septicidal. Melanthium, L. ; Colchioum, L. ; Veratrum, L. Tribe 3. ASPAEAGE^. Fruit baccate. Dracaena, Vand. ; Convallaria, L. ; Aspidistra, R. Br. ; Asparagus, Ker ; Ruscus, Tournef. Affinities, &c. The floral formula is P 3-J-3 A 3+3 G~3. The position of the parts may be thus represented: P .+.. A . + .. G v, the typical Monocotyledonous arrangement, but subject to variation according to the position of the bracteoles and other circumstances. The great Order of Liliaceae has, by Mr. Baker, been divided into three tribes as above. Smilaceae closely resemble the Asparageae, but all Liliaceae have anatropous ovules, and other marks of distinction are cited under that Order. As aberrant forms of Liliaceae may be mentioned Liriopeae or Ophiopogoneae, Conanthereae, connecting Liliacese proper and Amaryllidaceae, Gilliesieae (see p. 388), Stemoneae or Roxburghiaceae (see p. 383), and Scoliopeae. Looking only at the more familiar forms of the Liliaceae, the characters of the flowers are very definite, although the habit of the plants brought together in this Order varies extremely ; but there exist certain genera of petaloid Monocotyledons, whose relations appear closest to Liliaceae, which form links of chains leading off in very varied directions, through the Orders of this Subclass. Tulipa and the allied genera, with usually distinct lobes to the perianth and versatile anthers, are bulbous herbs ; Funkia, Hemerocallis, and other genera have a more or less tubular perianth, and often tuberous roots instead of bulbs ; Aloe has thick succulent leaves on a perennial stem ; Yucca has a Palm- like stem and rigid leaves. Scilla, Allium, and their allies are bulbous herbs, differing chiefly from the group to which Tulipa belongs in the firmly fixed anthers, and a membranous spathe enclosing the inflorescence when young. Anthericum and others resemble the last, but have tuberous or fibrous roots ; Aphyllanthes is a plant with the habit of Juncaceae and the flower of Liliaceae ; Xanthorrhcea, a genus belonging to the same group, forms a woody trunk like Yucca, or a small Palm. Asparagus and its allies, including Convallaria, Smilacina, Ruscus^ &c., together with the arborescent Draccencs and Cordylines, are Liliaceae with succulent fruits, and scarcely separable from Smilaceee. Conanthera and its allies, with the general structure of Liliacese, have the perianth more or less adherent, thus approaching Amaryllidaceae. Wachendorfia, Lopholia, and others have the free ovary of Liliaceee, but triandrous flowers and the foliage of Haemodoraceae. Aspidistra bears some resemblance in its foliage to Zingiberaceae, while the character of the flowers approaches that of the complete Aracese. Ophiopoyon and PeliosantJies are likewise doubtfully placed here ; but their structure is not satisfactorily made out. We see, therefore, that the Liliaceae have widely spreading relations, although the typical forms are at once distinguishable. The superior ovary separates them from Amaryllidaceae. Their very near connexion with Smilaceae is noticed above ; they have a more distant affinity to the Palms and to the Juncaceae in the general structure of the flowers, differ- ing from both in habit, fruits, and seeds. Gilliesiaceae and Pontederaceae are scarcely more than aberrant Liliaceae with irregular flowers. The structure of the arborescent stems of Draccena, Cordyline, Xan- thorrhcea, Yucca, &c. has attracted considerable attention, since, contrary to the usual habit of Monocotyledons, their trunks sometimes increase 386 SYSTEMATIC BOTANY. more or less in thickness with age. However, the central axis corresponds essentially to that of the Palms ; only a peculiar rind or false bark exists, capable of increase by layers, somewhat in the same way as the liber of Dicotyledons. Distribution. A large Order, the members of which are very variously and widely distributed ; the bulbous kinds common in temperate climates, the fibrous-rooted with them and in warmer localities : the succulent- leaved Aloes chiefly S.-Af rican ; the arborescent forms mostly subtropical. Qualities and Uses. Many of the Liliaceee have active properties, and the juices, the fibres, or the fruits afford products of value in the arts. The juice of the succulent-leaved Aloes dries into a kind of resin, medi- cinal Aloes, one of the most valuable of purgatives; the species from which it is usually obtained are Aloe spicata, mdgaris, socotrina, &e. The bulb of Urginea maritima is the Medicinal Squill, valuable as an expec- torant and diuretic, but emetic and purgative in large doses. Pancratium (often cultivated for its flowers) has similar properties. The leaves and roots of Erythronium (Dog's-tooth), of the Hyacinths (Hyacinthus orien- taliSj Insitanicus, Scilla nutans), and the genera Muscari, Ornithogalum, Gagea, all have emetic qualities ; the tuberous fibrous roots of Asparagus and of the Lily of the Valley (Convallaria majalis) are said to be purgative : those of Solomon's Seal (Convallaria Polygonatuni) are acrid. The bulbs of the Crown-imperial (Fritillaria imperialis) and other species, and of Glo- riosa superba, are said to be very poisonous. The bulbs of the genus Allium have milder properties, and at the same time possess a pungent quality, on account of whicn they are extensively grown for food, tne large and milder cultivated kinds being esculent vegetables ; the smaller and more pungent are valued for imparting flavour. Allium Cepa is the Onion; A. Porrum, the Leek ; A. sativum, Garlic ; A. Schomoprasum, the Chive ; A. ascalonicum, the Shallot ; A. Scorodoprasum, the Rocambole : " Spanish Onions," coming from Spain, Portugal, and Egypt, are mild varieties of the common Onion, the bulb growing to a larger size, and forming less of the pungent secretion. The bulbs of I/Mum pomponium constitute an important article of food in Kamtschatka ; the tubers of Camassia esculenta are eaten by the North - American Indians. The woody roots of Draccena terminalis (Cordyline Ti) are eaten, roasted, by the Sandwich-Islanders ; sugar and fermented liquor are likewise prepared from its juice ; its leaves furnish fodder for cattle, as do those of the Grass-tree (Xanthorrhcea} in Australia ; the bases of the young leaves and the heart of the buds of the latter are sometimes used as esculent vegetables. The table Asparagus consists of the very young annual shoots (turiones) of Asparagus officinalis, rendered succulent by cultivation. Astringent resins are obtained from some kinds : Dracana Draco, the Dragon-tree of Teneriffe, yields the true Dragon's Blood, for- merly much used in medicine, but "now seldom met with, the resin of Pterocarpus (Leguminosse) being substituted. Xartthorrhcca arborea yields Botany-Bay Gum, which is yellow, pungent, and smells like Benzoin when burnt. Phormium tenax is the New-Zealand Flax plant ; the fibre of the leaves is very tenacious, as is that of various species of Sanseviera, known as African Hemp and Bowstring Hemp in Africa and the East Indies. Active properties and uses are attributed to many other less-known species. A great number of Liliacefe, hardy and tender, ornament our gardens and stoves, as will be recognized from the list given above. Polianthes PETALOIDE^:. 387 tuberosa is the Tuberose, celebrated for its fragrance. The Butcher's Broom (lluscus aculeatus) is remarkable for its ioliaceous peduncles and really almost leafless stems ; and the fully developed flowering-stem of Asparagus has only needle-shaped branches simulating leaves. More or less poisonous qualities pervade the Colchicum tribe (Melan- thacese of some authors), with acrid, purgative, emetic, and sometimes narcotic action ; several of the more active species yield valuable medi- cines. Of Colchicum autumnale, called Meadow Saffron or Autumn Cro- cus, both the corms and seeds are very active ; Veratrum album, White Hellebore, V. nigrum, V. Sabaditta, V. viride (N. America), Asagrcea officindis (Sabadilla or Csvadilla of Mexico), all share the acrid narcotic qualities, poisonous or medicinal, according to the dose. Most of the other genera are suspicious or dangerous, except perhaps the Uvalariece (N. America), which are said to be merely astringent. XYRIDACEJE are sedge-like herbs with equitant leaves sheathing the base of a naked scape, which is terminated by a head of perfect 3-androus flowers, with a glumaceous calyx, a regular corolla, and extrorse anthers ; the 3-valved, mostly 1-celled capsule containing several or many ortho- tropous seeds, with a minute embryo at the apex of fleshy perisperm. In habit these plants approach Cyperaceae ; but the flowers are petaloid as regards the inner circle of organs, or corolla, nearly approaching Comme- lynaceoe, from which they diner in having epipetalous extrorse stamens, in the scaly calyx, and general habit. They are natives of the tropics or adjoining regions. Various species of Xyiis are used as remedies for cuta- neous aflections both in India and America. COMMELYNAOE^E (SPIDER-WORTS) are herbs with fibrous, some- times thickened roots, jointed and often branching leafy stems, and chiefly perfect and 6-androus, often irregular flowers, with the perianth free from the 2-3-celled ovary, and having a distinct green calyx and a coloured corolla, each of 3 parts, the calyx persistent ; stamens 6, all fertile or some abortive, often very peculiar in form ; capsule 2-3-eelled ; seeds few (2) in a cell, attached by a linear hilum ; embryo pulley-shaped, remote from the hilum, in dense fleshy perisperm. Illustrative Genera : Commelyna, Dill., Tradescanfia, L. Affinities, &c. This Order, to which belongs the garden Spider-wort ( Trade scantia virginica),m.a,y be regarded as one of the groups intermediate between the Orders with 6-merous glumoid perianth, like the Juncaceae, and the petaloid forms like Liliaceae. The jointed solid stems of Tra- descantia are interesting in regard to the comparative structure of Mono- cotyledonous stems ; they emit roots freely from the nodes like Grasses. The hairs of the filaments of the stamens of T. virginica are classic ob- jects to the botanist, from the discovery in them of the rotation of the cell-sap in non-aquatic plants. The rhizomes of Commelyna coelestis, tube- rasa, and others contain starch and mucilage, and are used as food in India. Some of the species are said to have medicinal properties. They are natives of India, Australia, Africa, and the West Indies a few of North America. Tradescant\a virginica is hardy in our gardens. PONTEDERACE^E are a small Order of aquatic herbs with perfect more or less irregular flowers in a spathe ; the petaloid, 6-merous 388 SYSTEMATIC BOTANY. perianth free from the 3-celled ovary; the 3 or 6 mostly unequal or dissimilar stamens inserted in its throat. They are separated from Liliacese chiefly by the irregular flowers, the persistent perianth rolling inwards after flowering, and by the mealy perisperm of their seeds. They are natives of North and South America, India, and Africa, and do not appear to have any important properties- Some of the Pontede.rice are usually grown in stoves where there is a tank, on account of their blue flowers. consist of four species of Mayaca, little Moss-like plants occurring in America, from Brazil to Virginia, separated from Comme- lynacese on account of their habit, 1-celled anthers, 1-celled ovary with parietal placentas, and the carpels opposite the inner lobes (petals) of the perianth. They have no useful properties. GILLIESIACEJE are a small Order of plants of somewhat anomalous structure, related to Liliacese (see p. 385) ; they are bulbous herbs with spikes of flowers which have a double circle of petaloid envelopes, 6 or 8 subulate processes, then a cup-like or labelloid organ bearing 3 or 6 anthers on its inner surface, and a 3-celled ovary. Lindley regards the petaloid envelopes and subulate processes all as bracts, and the structure on which the anthers are borne as the perianth. Other authors are opposed to this view. Gilliesia, Lindl., and Miersia, Lindl., are both Chilian genera. PHILYDRACEJE are herbs with fibrous roots, ensiform leaves with equitant bases ; flowers within a persistent spathaceous bract, with a 3- parted petaloid perianth ; 2 upper segments coherent into one ; 3 coherent stamens, of which the 2 lateral are barren and petaloid, and the middle has a two-celled anther, the whole adherent to the anterior lobe of the perianth ; the pollen-cells are coherent in masses of four ; the ovary supe- rior, 3-celled, the odd cell anterior, with axile placentas; seeds numerous, with an embryo in the axis of fleshy perisperm. This Order consists of two plants, Philydrum lanuginosum (Australia) and Hetceria pygmaa (China), exhibiting, with a superior ovary, appearances analogous to those in the epigynous group of Orchidaceae and their allies. Lindley regards them as related to Commelynaceaa and Xyridacese ; but they would appear to be rather a kind of peiigynous ZingiberaceaB. They have no known uses. B. APOCAEPI^:. Carpels usually distinct ; seed aperispermie. ALISMACEJ^. Coh. Potamales, Hook. Fig. 473. Diagnosis. Marsh-herbs, mostly with broad petiolate leaves and scape-like flowering stems ; flowers perfect or monoecious, with a double perianth, consisting either of a green calyx and a coloured deciduous corolla, or of 2 circles of green scales, each of three pieces (fig. 473) ; ovaries 3, 6, or numerous, more or less distinct, and separating into as many nuts ; seeds campy lotropous or anatropous ; embryo doubled, hook-shaped, or straight, p]an of flower of without perisperm. Triglochin: x, bract. PETALOIDE^, 389 ILLUSTRATIVE GENERA. Actinocarpus, JK. Br. Sagittaria, L. Subord. 3. BUTOMEJE. Internal circle of perianth coloured : ovules numerous all over the inner surface of the carpels ; embryo curved. Butomus , Tournef. Limnocharis, H. fy B. Subord. 1. JUNCAGINE^E. Peri- anth scaly ; anthers always extrorse ; ovule inverted; embryo straight. Triglochin, L. Scheuchzeria, L. Subord. 2. ALISMEJE. Internal circle, of the perianth coloured; ovules solitary or twin ; ovule and embryo curved. Alisma, Juss. Affinities, &c. The Alismece bear considerable resemblance to the Dico- tyledonous Order Ranunculaceae, while Butomece have been compared with the Nymphaeaceae on account of the curious placentation ; but there is hardly any real relationship in this latter case. On the other hand, the Alismece have some similarity to the Commelynacese, from which they are separated by the aperispermic seed. This structure of the seed agrees with that of Naiadaceae, with which this Order is connected by the Jun- cayinece. Scheuchzeria in this last division approaches Juncaceae. Distribution. A small group, the members of which inhabit marshy localities in all parts of the world ; most abundant, perhaps, in temperate climates. Qualities and Uses. An acrid property is common in the foh'age and in the rhizomes, but the latter are sometimes fleshy and farinaceous, and then may be eaten after the acridity is removed by cooking. Sagittaria sinensis is cultivated for food in China. Many are very handsome aquatic plants, and are cultivated for the sake of their flowers. NAIAD ACE^E. THE POND-WEED 'ORDER. Coh. Potamales, HooTt. Diagnosis. Immersed aquatic plants, with jointed sheathing stipules within the petioles, or with sheathing bases to the leaves ; inconspicuous, monoecious, dioecious, or perfect flowers, which are naked or have a free, scale-like perianth ; the ovaries solitary or 2-4 and distinct, 1-celled, 1- ovuled; seed aperispermic; embryo straight or curved (fig. 474), with a thin membranous testa. Illustrative Genera : Naias, Willd. ; Zostera, L. ; Ruppia, L. ; Zannichellia, Michel. ; Potamogeton, L. ; Aponogeton, Thunb. stems and Fig. 474. geton, with the testa removed : a, radicle ; 6, cotyledon ; c, plu- mule. Affinities, &c. This Order agrees with Hydrocharidaceae and Alismaceas the structure of its seeds, but differs in the simpler organization of the 390 SYSTEMATIC BOTANY. inflorescence, which, as also its perianth, is like that of Spadiciflorae, which, however, is connected with that of Alismacese in Scheuchzeria. Decaisne and Maout, following A. de Jussieu, keep distinct the Juncagineae, Apono- geteae, Potameae, and Naiadeae, all of which, with the exception of the first, are here included under Naiadaceae. The groups established or main- tained by the authors just cited are collectively characterized by the absence of a perianth or at least of a petaloid perianth, while they are separated one from the other by the form and direction of the embryo, which is straight and slender and with the radicle next the hilum in Juncagineee, swollen and with the radicle away from the hilum in Zostera, swollen and with the embryo so curved that both its extremities are near the hilum in Potameee, swollen and with the radicle directed to the hilum in Naiadeae. The form of the stigmas, whether entire and truncate or linear and divided, is also relied oil to distinguish the several groups. Some authors consider the in- florescence really spadiciflorous, and regard the scaly perianth, when present, as consisting of bracts surrounding imperfect unisexual flowers ; and this idea is supported by the spathe-like bract which occurs in some genera (Zostera, c.). From this point of view they are related to Lem- naceae ; but the character of the seeds is diverse. The structure of these plants is generally very simple, consisting chiefly of cellular tissue of very delicate organization ; in Ouvirandra the lamina of the full-grown leaf becomes a delicate lattice-like plate, the interspaces between the ribs being destroyed during expansion. Zostera is remarkable for its pollen-grains being tubular and destitute of an external coat. Distribution. The species are numerous, and are met with in still, fresh and brackish water, and in the sea (Zostera*), in all parts of the world. Qualities and Uses. Apparently destitute of active properties. The leaves of Zostera marina are collected and dried on the sea-coast as a material for packing, filling mattresses, &c. Division II. Spadiciflorae. Monocotyledons with flowers usually on more or less fleshy, simple or branched spikes (spadices), with or rarely without spathes. Perianth biseriate ; segments uniform, herbaceous or none. Exceptions, &c. This group is one readily recognizable, though not easily defined in words. It is subject to many exceptional and transitional forms. In Palms the structure of the perianth is like that of some Liliaceae or Jun- caceae, but the segments are more fleshy ; the Lemnaceae, usually considered the lowest representatives of the Aroid type, have so few flowers that the spadiciform peduncle does not represent this structure very clearly, but it is surrounded by a spathe. Taccaceae resemble Araceae in habit, but their flowers are more complete. The inflorescence is of the same general cha- racter throughout, but with many modifications. SPADICIFLOK^:. 391 PALMACILE. PALMS. Coh. Palmales, Benth. et Hook. Diagnosis. Trees or shrubs, mostly with a simple unbranched trunk (fig. 478), occasionally slightly ramified, -p- 475 with large terminal clusters of mostly compound, or deeply divided stalked leaves, the stalks sheathing at the base ; flowers unisexual or per- fect, with a double 3-merous herbaceous perianth, on a mostly branched scaly spadix enclosed by spathe (fig. 475) ; stamens 6, hypogynous or perigynous ; ovary of 1-3 free or coherent car- pels ; ovules solitary, rarely two ; fruit baccate ; seeds with a minute embryo imbedded super- ficially in horny, fleshy, or bony perisperm. Illustrative Genera : Chamcedorea, Willd.; Areca, L. ; Ceroxylon, H. & B. ; Caryota, L. ; Calamus, L. ; Sac/us, Grsertn. ; Borassus, L. ; Lodoicea, La- bill. ; Sabal, Adans. ; Chamcerops, L. ; Rhapis, L. fil. ; Phoenix, L. ; Attalea, H. B. K. ; Elais, Jacq. ; Gocos, L. Affinities, &c. The Palms form a very natural Order, including a great number of plants varying to a considerable extent among themselves, but sepa- , , , . . . P ,, . .** Snathe and branched rated by very distinct characters from the rest of the 8 padix of Astrowryum Monocotyledons. They as a rule, assume an arbores- vulgare. cent character, the stem being formed on the same fundamental plan as those occasionally occurring in other Orders of Monocotyledons : the stem of the Calamoid Palms bears much resemblance to that of the Bamboo among the Grasses ; the forms with scarcely developed internodes, marked externally by the scars of the fallen leaves, agree essentially with those of Yucca, Xanthorrhcea, &c., except that the fibrous cortical region is little de- veloped and does not exhibit growth by successive layers as in those plants ; the Hyphcenes, which have a branched stern, seem to ramify in the same way as the Vellosiae, by a bifurcation resulting from the occasional develop- ment of an axillary bud, which manifests a power of growth equal, or nearly so, to that of the terminal bud. The ramification of the trunks above ground is a rare phenomenon ; but it is very common for suckers to he sent out from the bases of the stems below the soil, imitating on a large scale the appearance of the young bulbs around the parent in the herbaceous Monocotyledons. The parenchymatous substance of the stem, in which the fibrous structures are imbedded, varies much in consistence : sometimes it becomes lignified, and gives a solid character to the trunk, as in the Cocoa-nut Palm ; sometimes it is soft and spongy internally, as in the Sago-palms, becoming filled at certain seasons with starch. " The spadiciform inflorescence, unfolding from within a large foliaceous spathe, connects the Palms with the Aracese, a relationship further indicated by 392 SYSTEMATIC BOTANY. the low type of structure of the floral envelopes ; but there is a general tendency to union of the sexes here, and a difference in the position of Fig. 478. Fig. 477. Fig. 476. A Date, with half the pericarp removed (c) to show the seed and embryo (a:). Fig. 477. Section of the fruit of the Cocoa-nut Palm: x, the shell of the nut. Fig. 478. Trunk and foliage of a species of Areca. the embryo within the perisperm not to dwell upon the wide diversity of general structure and habit. The regular ternary arrangement of the flowers, the 6 stamens, and the 3-carpellary superior ovary approximate this family to the Liliacese, in which, however, the habit differs in almost every respect, besides the great diversity of the fruits and seeds. The floral formula of a perfect Palm flower is thus that of a typical Monocotyle- don, but variations occur from suppression of parts and in accordance with the relative position of the bracteoles, &c. The inflorescence of the Palms is in some cases axillary, allowing of indefinite growth of the trunk by the terminal bud ; in other cases it is terminal, and the flowering of the plant then puts a period to the term of growth (sometimes as much as 20 years), the trunk dying after the ripening of the fruit (like the main stem of the Agave}, but occasionally perpetuating itself by subterranean axillary suckers. Sometimes the axillary inflorescence breaks out from above the cicatrix of a long-fallen leaf, on the bare part of the stem. The flowers are generally very numerous ; it is said that the male inflorescence of the Date may bear 12,000 flowers, and that a bunch of some of the South- American Palms will bear 3000 fruits. In Alfonsia amygdalina 207,000 flowers have been computed on a single spadix, or 600,000 on one plant ! There is very considerable apparent variety of form and structure SPADICIFLOKjE. 393 of the ripe fruit in this Order, easily reducible, however, to a single type. As a rule, there are 3 carpels, either distinct or united into a 3-celled ovary, each carpel commonly producing 1 ovule ; in Cocos, however, 2 out of the 3 cells are rudimentary, and thus only one ovule is developed even at first; in Areca and others, 3 distinct cells and ovules originally exist ; in Chamcerops and Phwnix the 3 carpels form separate 1-ovuled pistils ; in Borassiis, a 3-celled, 3-ovuled ovary exists, and the same in Lodoicea. In the course of the maturation of the fruit, the pericarp be- comes variously developed, and more or less of the ovules or of the distinct simple ovaries are aborted. In Cocos the pericarp is developed around the one perfect cell, externally as fibrous husk, internally as the woody shell of the nut ; the fleshv part of the nut (hollow) constitutes the albumen of the seed surrounded by a brown testa ; and the embryo is lodged in a cavity in the substance o*f the perisperm, at one side, near the base (fig. 477). In Areca, 2 out of the 3 cells and ovules are abortive ; the pericarp ripens into a fibrous husk round a solid seed, chiefly composed of horny ruminated perisperm (the Areca-nut). In Chamcerops and Phoenix, 1 out of the 3 simple ovaries ripens into a berry; the pericarp, becoming the pulp (Date), contains a " stone " or seed, which is a solid mass of horny perisperm with the embryo imbedded in a small cavity a little be- neath the surface (fig. 476), its place being indicated by a papilla on the surface. In Borassus, all the ovules become developed, and form 3 fibrous " stones " in the fruit. In Lodoicea it often happens that 2 or even 3 ovules coalesce during ripening, forming large, hollow, double or triple nuts, of the same character as the Cocoa-nut, enclosed in a large fibrous husk (these are the " Double Cocoa-nuts " of the Seychelles Islands). In Sagus and other genera the ovary is clothed with imbricated scales pointing to the base, which ripen into woody structures, forming a peculiar hard-scaled covering to the fruit. These scales, according to Spruce, are rudimentary leaf-blades [scales ?] reflected. The subdivisions of the Order depend upon the habit, foliage, nature of the fruit, attachment of the seed, position of the embryo, &c. Distribution. A large Order, consisting of about a thousand species, chiefly tropical ; scarce as regards species in Africa ; a few advancing into temperate latitudes in North America, Europe and Asia, and New Zealand. Remains of Palms have been found in the Upper Cretaceous and more recent rocks. Qualities and Uses. Having (apparently) no noxious properties, the very varied products of this noble Order of plants render them of an importance to man second, perhaps, only to that of the Cereal Grasses. Their juices and secretions furnish sugar, starch, oil, wax, and resins; fer- mentation of the juices of many produces spirituous liquids. Some have edible fruits of great importance ; the succulent buds of others are used as esculent vegetables ; their leaves are applicable to countless uses, from thatching huts to plaiting mats and hats ; the fibrous substance of the sheathing petioles furnishes materials for cordage, or, when more solid, supplies a valuable substitute for bristles and whalebone ; the fibrous husks of the fruits afford textile materials ; the trunks of some kinds become valuable timber ; and the hard perisperm of the seeds of several kinds is very largely used for turners' work connected with cabinet-making &c. Saccharine juice, furnishing sugar or fermented liquid, according to the 394 SYSTEMATIC BOTANY. use made of it, is obtained abundantly by cutting the unopened spatlies of Caryota wens, Cocos nucifera, Borassusjlabelliformis, Rhapis vinifera, Sayuerus (Arenyd) saccharifer, Phoenix sylvestris, Mauritia mnifera, Elais yuineensis, and others ; starch is obtained abundantly from the central parenchyma of the trunk of Sayus Humphii, Metroxylon Iceve, Sayuerus saccharifer, Phoenix farinif era, &c. Oil is obtained especially from the African Oil-Palms (Elais yuineensis and E. melanococca) , the fruits being crushed and the oil extracted from the perisperm by boiling in water ; Cocoa-nut oil is obtained from the perisperm of the seed ; wax is excreted on the lower surface of the leaves of Copernicia cerifera, on the trunk and between the leaves of Ceroxylon andicola. Calamus Draco, Hyphcene, and others have a resinous matter in their juices. The most important fruits are those of the Date (Phoenix dactylifera) and the Cocoa-nut (Cocos nucifera) ; the fruit of Hyphcene thebaica, the Egyptian Doum-palm, is also eaten ; and the seeds of Arecha Catechu (Betel-nuts) are very largely used, in the East Indies, for chewing with the leaves of the Betel Pepper. The fruits of some of the Palms are acrid (Caryota, Sayuerus) ; the acridity, however, is removed by soaking in lime-water, and they are eaten preserved with sugar. The Indian Cabbage-palm, of which the buds are eaten boiled like cabbages, is Areca okracea ; Euterpe montana is used in the same way. Fibrous substance is derived from the husk of the fruit of the Cocoa-nut (Coir), Astrocaryum vulyare, Attalea funif&ra, and others; the bristle-like Piassaba fibres, used for brooms, are from Leopoldina Piassaba. The wood of the Cocoa-nut Palms is hard, durable, and handsome (Porcupine-wood) ; JSorassus Jlabelliformis yields what is called Palmyra-wood. Nuts suitable for turning are afforded by the seeds of Attalea funifera (Coquilla nuts) and Phytelephas macrocarpa (Vegetable Ivory). The resin known as Dragon's blood is yielded by Calamus Draco. Common canes are the stems of Calamus Scipionum, Zalcicca ruden- tmn, &c. Partridge canes, used for walking-sticks, &c., are stems of an unknown Palm. The petioles of Chamcerops humilis are used for walk- ing-canes in Italy j and the fibre of the leaves of this plant is now coming extensively into use as a substitute for horse-hair. The foregoing is only a brief summary of some of the best-known uses of these plants ; similar products and applications are connected with a great number of other species besides those here mentioned. Several species are cultivated, for the grandeur of their foliage, in our stoves ; and some, such as Jubcea spectabilis and Chamcerops excelsa, are sufficiently hardy to be grown out of doors in the south of England. PANDANACE^E (ScREW-PiNEs)are trees or shrubs of Palm-like habit, but often dichotomously branched, with the leaves sheathing at the base, imbricated in 3 spiral ranks ; flowers numerous, naked or scaly, male and female or polygamous, arranged densely on a simple or generally branched spadix furnished with numerous spathaceous bracts ; anthers stalked, 2-4-celled j ovaries mostly grouped, 1-celled, with solitary or numerous ovules on parietal placentas ; fruits with a fibrous husk, 1-seeded, arranged in groups, or many-celled beriies with many-seeded cells ; embryo minute, imbedded at the side near the base of the fleshy perisperm. Illustrative Genera : Suborder 1. PANDANEJS. Flowers naked ; leaves simple. Pan- SPADICIFLOE^E. 395 danus, L. fil. ; Freycinetia, Gaud. Suborder 2. CYCLANTHE^;. Flowers mostly with a perianth ; leaves fan-shaped or pinnate. Carludovica, R. & P. ; Nipa, Ruinph. ; Cyclanthus, Poit. Affinities, &c. This Order is related on the one hand to the Typhacese by the inflorescence, which resembles that of Sparganium ; on the other to the Palmaceae, which the Cyclanfhece approach in habit and foliage. The branching stem and the large aerial roots of Pandanus (fig. 10, p. 19) are exceedingly curious. Distribution. Tropical: the Pandanece chiefly in the East-Indian Islands, Mauritius, &c. ; the Cydanthece American. Fossil Pandanads have been observed in the Upper Chalk. Nipa is common in the Eocene deposits of the mouth of the Thames. Qualities and Uses. The seeds are edible; saccharine fermentable j uice flows from the cut spadices of Nipa and other species ; the leaves and fibres are used for cordage, plaiting hats, &c. TYPHACE^E are marsh-herbs, with nerved and linear sessile leaves and monoecious flowers, on a spadix or in heads, destitute of a proper perianth, which is replaced by 3 or more scales or a tuft of hairs ; stamens 1-6, distinct or monadelphous ; anthers innate; ovary solitary, 1 -celled ; ovule solitary, pendulous ; em- bryo in the axis of mealy perisperm (fig. 479) ; radicle next the hilum. The habit and general appearance of these plants resemble those of CyperaceaB, and the hairs of the flowers of Typha are analogous to those of Eriophorum ; but they belong to the Araceous type, and the structure of their inflorescence approaches closely, in Sparganium especially, to that of Pandanacese, which, however, ha.ve the ripe "fruits more or less blended into a mass. There Section of seed is ^ilso some resemblance in the inflorescence and in the of Typha. flowers to Platanacese. The plants grow in ditches and marshes in most parts of the world. The rhizomes of Typha contain a certain amount of starch, and the young shoots of Bulrushes ( T. latifolia and T. angusti- folia} are sometimes used as esculent vegetables, like those of Asparagus. The abundant pollen is also nutritious, and is made into a kind of bread in Scinde, in New Zealand, and elsewhere. AEOIDACE^l. Coli. Arales, Benth. et Hook. Diagnosis. Plants with acrid or pungent juice, simple or com- pound, often prominently-veined leaves, and monoacious or perfect flowers crowded on a spadix, which is usually surrounded by a large bract or spathe (fig. 480); perianth wanting, or of 4-6 scales ; fruit usually a berry ; seed with the embryo in the axis of mealy or fleshy perisperm, or occasionally aperisperrnic. 396 SYSTEMATIC BOTANY. Fig. 480. Fig. 480. Calla: spathe and spadix. Fig. 481. Amorphophallits : corm, spathe, and spadix. ILLUSTRATIVE GENERA. Subord. 1. ARACEJE. Flowers imperfect ; spadix surrounded by a Arum, L. Colocasia, Ray. Caladium, Vent. Dieffenbachia, Schott. Bichardia, Kunth. Subord. 2. OROXTIACE^:. Flowers perfect, mostly witJt, a perianth ; spa- dix surrounded by a spathe or naked. Tribe 1. With a spathe. Calla, L. Pothos, L. Tribe 2. Without a spathe. Orontium, L. Acorus, L. By Engler this large group has been recently subdivided into ten sub- orders and numerous subsidiary tribes and subtribes. The suborders are Pothoideaa, Monsteroideae, Lasioidese, Philodendroidese, Aglaonemoideae, Colocasioideae, Staurostigmoidese, Aroideae, Pistioideae, and Lemnoideae. The principal characters relied on to distinguish these groups are the presence or absence of laticiferous vessels, the presence or absence of H or H shaped intercellular hairs, the arrangement of the leaves and shoots, the venation of the leaves, the bi- or unisexual flowers, the presence or absence of a perianth, the direction of the ovules, &c. &c. The floral formula for Acorus is P '. + .'. A .'+" Gv, the ordinary Monocotyledonous form. In other genera great modifications arise from suppression of parts, &c. Affinities, &c. The peculiar thickened fleshy flowering stem densely covered with flowers of rudimentary structure, forming the spadix of this SPADICIFLOR^l. 397 Order, together with the spathe met with in most cases, give the group a character of habit which is generally very distinct ; some genera, however, such as Acorus, depart from this form, and approach the Typhacese or Cyperacese in aspect, with which the spadiciflorous structure at the same time unites them ; they have further relations with the Pandanacese, and also with the Palmaceae, in w^hich the inflorescence shares the spadici- liorous characters ; and although the perianth is much more definite and highly developed there, its presence in Acorus and Orontium of this Order forms a connecting link. Lemnaceae are closely related here, and perhaps should be regarded as the simplest form of Aroids; but the conditions are so simple there that it is more convenient to separate them. From Naiadaceae, in which the inflorescence is moreover hardly spadi- ciflorous, the Aroids are easily distinguished by the character of their seeds. The Araceae are either herbs, sometimes with very large leaves and spathes, or their stem becomes more or less developed and branched, so as to give them a shrubby character ; while others are epiphytic and climbing plants, producing aerial roots like the Orchids. The leaves are of the most varied character in this Order. Distribution. A large Order, not numerous in temperate climates, but represented there by Arum, Calla, and Acorus. Most abundant in the tropics, especially in forests and the lower regions of mountains. Qualities and Uses. The juices of the Aroids are generally acrid and dangerous, some very poisonous ; but heat seems to dissipate the noxious principles. The acridity is replaced by agreeable aromatic pungency in Acorus Calamus. The corms and rhizomes often contain much starch, which is extracted, and purified by washing, from Arum maculatum (Portland Arrowroot) ; while the corms of Arum indicum, Amorpho- phollus campanulatus, Caladium bicolor, Colocasia esculenta ("Cocoes'' and "Eddoes," West Indies), C. macrorhiza ("Tara," South-Sea Islands), and C. himalayensis are eaten, roasted or boiled. The rhizomes of Calla palus- tris are also eaten after thorough washing. Diefferibachia seyuina, the u Dumb-cane " of the West Indies, is so called from the inflammation of the tongue and fauces produced by chewing it; Dracontium pertusum (remarkable for its perforated leaves) has blistering properties. Symplo- carpus fcttidus, the " Skunk-cabbage " of North America, is very foetid, as is also *the newly opened inflorescence of Arum Dracuncidus, A. italicum, and others, which produce sickness and serious indisposition in some constitutions. Richardia africana is the white spathed " Trumpet-Lily " of our conservatories. The species of Philodendron are very handsome stove-plants. Anthurium Scherzerianum is particularly noticeable for its brilliant scarlet spathes and its twisted spadix. LEMNACEAE are minute stemless plants, floating free on the water, either destitute of distinct stem and foliage, as in Lemna, or consisting of tufts of leaves connected by filiform runners (Pistia) ; producing few monoecious flowers, surrounded by a spathe, from a chink at the edge or upper surface of the frond, or in the axils of the leaves ; stamens definite, sometimes monadelphous ; ovary 1-celled, with 1 or more erect ovules, from the base of the cell; fruit a 1- or more-seeded utricle; embryo straight, in the axis of fleshy perisperm. Lemna, the genus to which the common Duckweeds belong,' is one of the simplest representatives of the 398 SYSTEMATIC BOTANY. Phanerogams, composed of a stem consisting of 2 or 3 small leaf-like lobes producing little filiform roots below, and ultimately displaying a scale-like spathe at the margin, enclosing the inflorescence, reduced to two naked and unisexual flowers ; the male flower consisting of one or two stamens, the female of a simple pistil. Wolffia is still more simple, inasmuch as it consists of a flat green plate homologous with the thallus of Cryptogams, on which is placed one male flower consisting* of a single stamen and one female flower consisting of a single carpel. From the under surface near the edge protrudes a small bud, by which the plant is reproduced vegetatively. It may be thus represented Al Gl, the = in- dicating the thallold stem. Pistia, also represented by little floating water- plants, has distinct tufted leaves, and the tufts are connected by flagelliform branches like the runners of a Strawberry. The spathes are here axillary, and they enclose separate male and female flowers seated on distinct parts of the central line of the spathe, which would appear therefore to be a branch, like the leafy peduncle of Rmcus, or else it has the spadix or peduncle adherent to its inner face. By some these genera, with Am- brosinia, is included under true Arads. The Lemnacene are the lowest forms of the Aroid type of Monocotyledons, and are related by habit to the Naiadacese. The Lemnce occur chiefly in cool climates ; Pistia princi- pally in the tropics. Pistia appears to possess acrid properties ; but the plants are of little importance, except, perhaps, as tending to purify the stagnant pools and ditches in which they abound. Genera : Lemna, L. ; Pistia^ L. ; Amfoosinia, L. Division III. Glumiflorae. Monocotyledons with the flowers collected into close spikelets or heads or in loose cymes ; perianth glnmaceous, biseriate, or none. Leaves sheathing. Seed perispermic. Exceptions, &c. The perianth in this group when present is either dry and scaly or bristly not fleshy or herbaceous. In Juncacese, &c., it is quite regular and encyclic ; in Sedges it is often wanting ; in Grasses it is scaly and surrounded" by glumes. The term " glume " is often used vaguely to signify either a bract or a perianth-segment. It is therefore preferable to use the adjective term glumaceous. The habit is often characteristic ; thus we speak of a sedge-like or rush-like habit, implying a rhizome with erect generally unbranched stems, clothed at the base with scaly leaves. Grasses vary much in habit, as described under that Order. Naiads have a glumaceous perianth, but differ in most other particulars from the Orders here associated. Xyrids differ technically in the possession of a true corolla. JUNCACESE. EUSHES. Coh. Liliales, Benth. et Hook. Diagnosis. Grass-like or sedgy herbs, with fibrous roots, or a subterraneous rhizome, with jointed sterns, often capitate inflores- 399 cence, and a regular persistent perianth of 6 similar scale-like pieces; stamens 6, or rarely 3, with introrse anthers ; ovary 1-3-celled, producing a 3-valved, 3- or many-seeded, or sometimes a 1 -celled and, by suppression, 1-seeded capsule : embryo minute, in fleshy horny perisperni ; radicle inferior. Illustrative Genera : Luzula, DC. ; Juncus, DC. ; Nartliedum, Mcehr. Affinities, &c. With Juncaceae are included by Lindley a number of genera which are regarded as doubtful, or established as separate Orders by some writers, such as Astelieae, a group of woolly- leaved epiphytic plants of the southern hemi- sphere, and Kingiese, plants with a stem like Xanthorrhcea and a 1-seeded fruit, and some Ternary flower of others. The genus Juncus (Rush) connects the Luzula. Order to Liliacese, from which the chief difference lies in the habit, the small embryo, and the glumaceous character of the segments of both circle^ of the perianth ; Narthecium connects them ; from Xyridaceae the latter character divides them. Xerotes approaches the Palms in the character of the flowers ; and this is associated with Kinqia, which has an arborescent habit. The scaly perianth connects them with Cyperacese, Restiacere standing between and differing from Juncaceoa in trifling points, which will be noted under that Order. Distribution. A considerable group, the members of which are natives chiefly of cold or temperate regions ; some occur in tropical Australia. Qualities and Uses. Without important properties in most cases. The leaves of Rushes (species of Juncus} are largely used for making mats, chair-bottoms, &c. ; and the parenchyma or " pith " of the cylin- drical leaves and stems was much used until recently for making the wicks of rushlights ; this substance has a beautiful microscopic structure, being formed of regular steiliform cells. DESVAUXIACE^: are little, sedge-like herbs, with glumaceous flowers in a terminal spathe ; glumes 1 or 2 ; palese 0, or represented by scales parallel with the glumes; ovaries usually several, sometimes consoli- dated, each with a pendulous ovule; stamens 1, or rarely 2; anthers 1-celled ; seeds perispermic ; embryo terminal. These little plants, chiefly natives of Australia, are of small importance, except as representing one of the types of the Glumaceous condition of Monocotyledons. They differ from Cyperaceae in having several 1-celled ovaries more or less coherent, or, if a solitary ovary, it is 1-carpellary ; the anthers also are 1-celled, and the embryo terminal, as in Restiacene ; but they have only one stamen, a 1-celled ovary, and a utricular fruit bursting longitudinally. Genera : Centrolepis, Labill. ; Gmmardia, Gaudich. ERIOCAULACE^E are aquatic or marsh-herbs, stemless or short- stemmed, with a tuft of fibrous roots, and a cluster of linear, often loosely cellular, grass-like leaves, and naked scapes sheathed at the base, bearing 400 SYSTEMATIC BOTANY. dense heads of monoecious or rarely dioecious, small, 2-3-merous flowers, each in the axil of a scarious bract ; the perianth double or rarely simple, scarious ; the anthers 2-celled, introrse ; the fruit a 2-3-celled, 2-3-seeded capsule ; seeds pendulous, winged or hairy, with a lenticular embryo at the end of the perisperm remote from the hiluru. The membranous tube surrounding the ovary represents the corolla, and thus places this Order intermediate between the Glumaceous Orders and the Xyridacese, which lead on through Commelynaceas to the Liliaceaa and their allies. The plants are mostly natives of America and Australia. Eriocaulon septanyu- lare occurs in the Western Islands of Scotland (Skye). RESTIACEvE are herbs or under-shrubs, generally without perfect leaves; stems usually with slit-convolute leaf-sheaths; with spiked or ag- gregated glumaceous, mostly unisexual flowers ; perianth-segments gluma- ceous, 2-6, or seldom ; stamens 2-3, adherent to the inner perianth-seg- ments ; anthers usually 1 -celled, rarely 2-celled ; ovary superior, 1-3-celled, odd cell anterior, v ; ovule solitary in each cell, pendulous ; seeds peri- spermic, embryo terminal. Principally distinguished from Cyperaceas by the pendulous seed and terminal lenticular embryo, further also by the leaf- sheaths being slit; from the Juncacese by the same characters, by the stamens, when 3, being opposite the inner glumes, and by the usually 1-celled anthers. They "are without the membranous perianth between the glumes and the ovary which occurs in Eriocaulaceae ; while Xyridaceae, among the Petaloidese, have the floral envelopes in 2 circles, of which the inner is petaloid. From Desvauxiaceae they differ in having 2 or 3 sta- mens, and if with a 1-celled ovary usually 2 styles, and the distinct perianth. In Lepyrodia hermaphrodita the flower has six stamens, and the arrangement is typically Monocotyledonous, the odd cell of the ovary anterior. The species occur chiefly in Australia and South Africa; one occurs in Chili. The tough wiry stems have economic uses, for basket- making, thatching, &c. Genera : Restio, L.; Thamnochortns,lB&Tg.; Lam- procaulos, Mast. ;, Willdenovia, L. CTPEEACE^E. SEDGES. Coh. Glumales, Benth. et Hook. Diagnosis. Grass-like or rush-like herbs, with fibrous roots and solid stems, closed tubular leaf-sheaths, without ligules, and spiked perfect or unisexual flowers, one in the axil of each of the gluma- ceous imbricated bracts, destitute of any envelopes or with a tubular bract (figs. 484 & 485), or with hypogynous bristles or scales in its place (fig. 483) ; stamens definite, hypogynous, 1-7 or 10 or 12 ; anthers 2-celled ; the 1-celled ovary with a single erect anatropous ovule forming in fruit a utriculus containing a seed with a lenticular embryo enclosed in the base of perisperm. ILLUSTRATIVE GENERA. Carex, Mich. Kobresia, Willd. Schoenus, L. Cladiura, R. Br. Isolepis, R. Br. Scirpus, L. Eleocharis, R. Br Eriophorum, L. Cyperus, L. Papyrus, Willd. GLUMIFLOK^E. 401 Fig. 483. Fig.484. ^>VX Fig.48.5. Fig. 483. Flower of Eriaphorum. Fig. 484. Female flower of Carex. Fig. 485. Section of the same, showing the ovary. Affinities, &c. This large Order of Glumaceous plants resembles in many respects the Grasses, but has several marked distinctive characters, viz. the tubular leaf-sheaths, the usually angular and solid stems, the general reduction of the floral envelopes to a single bract or glume (2 additional glumes exist in Carex and some other genera, and hypogynous bristles or setae in Scirpus, JSriophorum, c.), and the fact of the embryo being enclosed centrally in the base of the perisperm of the seed. From Resti- aceae, some of which resemble Sedges in habit, they are distinguished by the erect seeds, by the 1-celled ovary being formed of 2 or 3 carpels, and by the leaf -sheaths not being slit. The floral formula for the male flower of Carex is Av, for the female flower G .., the brackets indicating the bracts. ^r-> ^r-> Cladium has a succulent fruit. The subdivisions of the Order depend on the distichous or imbricated bracts (glumes), general or partial fertility, open or closed utricle, degree of development of perianth after flowering, presence or absence of staminodes, form of base of style, nature of fruit, &c. The tubular bract of Carex, sometimes called the " utricle " (an objectionable term as it may be confused with the form of fruit so named), is, according to McNab and Dyer, a foliar organ, single, or perhaps of two congenitally united, in whose axil the flower is produced. Distribution. Universally diffused, especially in marshes and about running streams. Carex and Scirpus belong chiefly to cool climates, Cyperus, Mariscus, and others to warmer, while some appear ubiquitous. Scirpus triqueter is found in Europe, South America, and Australia. In a fossil state they are first recognized in the Lower Miocene. Qualities and Uses. The plants of this Order are generally devoid of active properties, and are less nutritious than the Grasses ; but some have bitter and astringent properties, while others are regarded as diaphoretics. Several of them have some economic value. The rhizomes of Cyperus low/us are astringent, those of C. rotundus contain an aromatic oil ; the creeping stems of Carex hirta, arenaria, and other species have been used as substitutes for Sarsaparilla. The rhizomes of Cyperus esculentus, C. bulbosus, and some other plants of this Order, being tuberous and devoid of noxious properties, are used locally as articles of food. Papyrus anti- quorum, a tall Sedge, with a spongy pith, is celebrated as having furnished 2D 402 SYSTEMATIC BOTANY. the ancients with a kind of paper, made by cutting the pitli into laminae, which were laid one upon another and pressed, thereby becoming glued together by their own sap. Its stem was, and is still, used for basket- making, mats, &c., like various Scirpi &c. The species of Eriophorum, the Cotton-grasses of our moorlands, produce a flock of cottony hairs around the fruit, sometimes used for stuffing cushions, &c. Carex arenaria (fig. 25, p. 31) and C. incurva, growing on sandy sea-shores, are very effi- cient in binding the shifting sand. GBAMINACEJE. GRASSES. Coh. Glumales, Benth. et Hook. Diagnosis. Monocotyledons (mostly herbaceous, rarely woody and arborescent), usually with hollow stems, with solid joints at the nodes ; leaves alternate, distichous, with tubular sheaths slit down on the side opposite the blade, and a ligule (p. 52, figs. 59, 60) at the base of the blade ; the fruit grooved on one side, embryo outside the perisperm. Fig. 487. Fig. 486. Fig. 488. Fig. 486. SpikeletofAvena: a, a, glumes; 6, 5, flowering glumes or outer pale* of florets. Fig. 487. Compound spike, with spikelets, of Lolium. Fig. 488. Floret of Aoena: b, flowering glume ; 6*. awn; 6',palea. Character. Inflorescence spicate, the flowers arranged in spikelets or locusta, which are again aggregated in spikes, racemes, or panicles ; per- fect, or sometimes monoecious or polygamous. Spilcelets mostly with two alternate and unequal dry scaly bracts, called glumes, GLUMIFLOKJE. 403 forming a common involucre enclosing the florets (fig. 486) the outer glume sometimes absent. Flowers 2 or many, or rarely solitary with abortive rudiments of others, alternate on the rachis within the glumes, more or less overlapping from below, and each enclosed within the axil of a flowering glume (or outer palea, fig. 486, b), which is a bract often provided with an awn, and the palea (inner palea, fig. 488, b') which is two-nerved ; the perianth is represented by 2 or 3 hypogynous scales (lodiculce, fig. 489, x, #) sometimes wanting ; if *2 in number, collateral, if Fig. 490. Fig. 489. Floret of Avena with flowering glume removed: 6, palea; x, x, lodicule. Fig. 490. Section of caryopsis of Triticum : a, endosperm ; 6, embryo. Fig. 491. Pistil of a Grass, with feathery stigmas. Fig. 492. Section of embryo of Avena, the endosperm removed : a, radicle ; 6, cotyledon ; c, plumule. 3, the odd one posterior, distinct or united. Stamens hypogy- nous, 1-4, or 6 or more (usually 3, the odd one anterior), 1 oppo- site the flowering glume (alternate with the 2 scales) ; filaments capillary ; anthers versatile. Ovary superior, 1 -celled, with one ascending ovule ; styles 2 or 3, rarely confluent ; stigmas feathery or hairy (fig. 491). Fruit a caryopsis, with an inseparable peri- carp ; embryo lying on one side, at the base of farinaceous perisperm (figs. 490, 492). ILLUSTRATIVE GENERA. Tribe 1. PANICE^E. Spikelets ar- ticulated closely below the lowest glume, 2-, very rarely Showered; upper glume always containing the most perfect and only fertile Jlower ; axis of spikelet never produced be- yond the flowering glume ; Iodides never morn than 2. Panicum, L. Setaria, L. Sorghum, Pers. Andropogon, L. Coix, L. Tribe 2. PHALARIDE^:. Spike* lets articulated, sometimes as in Pa- niceae, and sometimes at the base of the pedicels near the main axis, 3- or apparently 1-Jlowered ; outer empty glumes laterally compressed, often united at the base, longer than the rest ; floivering glume terminal, hairy, with 2 rudimentary glumes below it ; otherwise as in Panicese. Phalaris, L. 404 SYSTEMATIC BOTANY. Tribe 3. POACE^E. Spikekts visually articulated above the lowest glume, 1- or many -flowered ; lowest flower usually perfect, terminal flower very rarely more perfect than those below it ; axis of the spikelet almost invariably terminated by an imper- fect glume, which is frequently re- duced to a small point or bristle ; Iodides generally 2, sometimes 3 ; stamens 1-3, rarely 6 ; fruit al- ways shorter than the flowering glume. Agrostis, L. Stipa, L. Oryza, L. A vena, L. Festuca, L. Bromus, L. Bambusa, L. Hordeum, L. Triticimi, L. Affinities, &c. The tribes above mentioned are those adopted by General Monro, the leading authority on this immense and difficult family. The description of the Grass-inflorescence above given is in accordance with the most modern views of botanists. According to this interpretation, the outer and inner glumes are involucral bracts common to all the flowers of the spikelet, the outer palea or flowering glume is a bract in the axil of which the short axis bearing the flower springs. This short axis bears the inner palea or " Vorblatt, 1 ' consisting perhaps of two bracteoles united together. The perianth consists of two Iodides placed collaterally, . . ; the androecium is made up of 3 stamens, the odd one anterior, v ; the gynaecium of two carpels. The entire flower, omitting the bracts and bracteoles, may therefore be thus represented, P . . Av G . To harmonize this arrangement with that typical of Monocotyledons, viz. P *.+.'. Av + .*. G v, it must be assumed that three outer parts of the perianth, one (posterior) part of the inner perianthial row, three stamens of the inner row, and one (anterior) carpel are suppressed. Now in Streptochwta spi- cata, according to Doll, the ordinarily missing parts are present, and the Monocotyledonous symmetry is restored, its floral formula being identical with that just given. In Bamboos and in Stipa the third lodicle (pos- terior) is present. In diandrous Grasses (Anthoxanthuni) the outer stamen is wanting ; in most Grasses the inner petal (lodicula) is absent. The inner (double) pale is absent in Alopecurus, Panicum, &c. ; in Lolium and Lepturus the outer glume is absent ; in addition to which the few-flowered spikelets of very many genera contain abortive, unisexual, or neutral florets, consisting of rudimentary pales. The comparison of the typical floral structure of Monocotyledons, P3-f3 A 3+3 G~3, with that of Grasses in general may be indicated by placing the numbers referring to the suppressed organs in italics, thus : P +^ +A 3+3 G~3. By Robert Brown and many others, the flowering glume and the inner palea were looked on as constituting three sepals of a calyx ; but the outer palea or flowering glume belongs to a different axis, is inserted lower down, and encircles the floral axis at the base, and the inner palea is a bracteole. Link looked upon the lodiculce as analogous to the scales in the throat of Narcissus, therefore apparently as representing the ligules of metamor- phosed Grass-leaves. The remarkable awn which is produced on the flowering glume of many Grasses, more or less free from its lamina, is regarded by some authors as a barren development of the axis of the spikelet, which would make the inner pale the subtending bract of the GLUMIFLOE^:. 405 flower. And it lias been considered that the occasional appearance of a flower on the upper part of the outer pale of monstrous flowers of the Nepal Barley (Hordeum coeleste) also indicates this glume to be a bract with an abortive floral axis adherent to it. The outer pale of viviparous Grasses (i. e. plants with the spikelets developing tufts of leaves) often appears as a rudimentary leaf with ligular processes at the junction of the vagina] and laminar regions, and thus as a simple leaf. The ligule has been considered an adnate stipule or pair of connate stipules ; it seems more simple to regard it as an excrescence from the upper part of the sheathing petiole. The cotyledon of Grasses is usually rather thick and applied to the perisperm. Many other explanations have been given, but this is the simplest and most in accordance with struc- ture and analogy. In Coix and some other Grasses, some portions of the spikelet or of the flower assume a bony character ; at other times, as in some of the Bamboos, the parts of the flowers become succulent and berry-like. In Streptocliceta spicata and in Anomochloa marantoidea the flower is solitary and terminal. In Anomochloa the Iodides are replaced by a row of flbrillsB (Doll). * The stems of Bambusa have the habit even of some Palmacese, while the structure of the seed approaches that of Aracese. But the nearest allies, in both habit and structure, are of course the Cyperaceae : one distinctive mark between them, the hollow stem, suffers exception in Saccharum and various Grasses of hot climates; the creeping rhizomes of ordinary Grasses are also commonly solid. The supposed diversity of structure of the stem of Grasses from that of other Monocotyledons is imaginary ; their culms are simply fistular states of the structure existing in Tradescantia viryinica, which,' like Grass- stems, roots freely at the nodes. The habit of the Grasses familiar to us in Britain is uniformly herbaceous j but Saccharum and some southern forms, such as Arundo Donax, Panicum spectabile, Festticaflabellata, &c., attain the dimensions at least of shrubs ; and Banibusa is arborescent, having a woody stem 50 or 00 feet or more in height. Distribution. Constituting one of the largest natural Orders, the Grasses are universally distributed, and in temperate climates appear in vast numbers of individuals, forming the principal mass of the verdure covering the surface of all but utterly barren soil. The great extent of their cul- tivation is also remarkable, and still more the absence of information as to the native countries of the Grain-grasses, which have been objects of artificial culture from before the memory of man. Rye, Barley, and Oats are the hardier grains ; Wheat is the chief grain of temperate and warm temperate climates, being associated in the latter with Maize and Rice, which form the chief grains of the tropics, Maize more particularly in America, Rice in Asia, and both, locally, in Africa, Rice-growing being dependent upon the possibility of irrigation. Various Millets (Sorghum^ Panicum, &c.) are largely grown in Africa and Asia, and to some extent in South Europe. The Grasses of warmer climates are more tufted and less gregarious in growth, acquire greater stature, are sometimes arbores- cent, and very frequently present the monoecious or polygamous condition of the flowers. Grasses in a fossil state have been found in the Upper Eocene and subsequent formations. Qualities and Uses. The main value of this Order rests upon the seeds 406 SYSTEMATIC BOTANY. or more properly the fruits, especially of what are called the " Cereal Grains," just referred to, and which in their abundant farinaceous peri- sperm, capable of great improvement in quantity and quality under cultiva- tion, furnish the principal material for bread in most countries, except where the severe cold forbids their growth, or the fertile soil and favourable climate supply sufficient food with a less laborious agriculture, as in the case of the Plantain, Bread-fruit, and other tropical esculents. The Sugar-Cane is another grass of scarcely less value : and the fodder-Grasses are of immense importance as furnishing food for domestic animals. A few of the Grasses have somewhat active properties. The principal Corn-plants are : Wheat, Triticum vulyare and many varieties (Spring Wheat is called T. astivum* Autumn Wheat T. hibei'- nurri) ; T. Spelta, Spelt ; T. compositum, the Mummy or Egyptian Wheat, has compound spikes; Barley, Hordeum distichum, with its varieties Hordeum vulyare (Bere or Big) and H. hexastichum ; Oats, Avena sativa and A. orientalis (Tartarian Oats) ; Rye, Secale cereale ; Maize or Indian Corn, Zea Mays ; and Rice, Oryzn saliva. Among those less generally known are: several Millets, such as Setaria germanica (German Millet) ; Setaria italica ("Kora Kang," East Indies); Panicum frumentaceum (" Shamoola," Deccan) ; Andropoyon Sorghum (" Burra") and A. saccharatum (" Shaloo," East Indies) ; Panicum mili- aceum (" Warree," East Indies) ; Penicillaria spicata (" Bajree," East T i \ T> _7 ?_ fit T^ 3 ** 1J TTT A. AT..* \ . T> ~lv /.*",,. i^~A canariensis, Canary seed, &c. &c. Among the most valuable fodder-Grasses of temperate climates are : the Rye-grasses, Lolium perenne, italicum, &c. ; Phleum pratense, Festuca pratensis, Cynosurus cristatus, Anthoxanthum odoratum, &c. Panicum spectabile, a hay-grass of Brazil, grows or 7 feet high ; Anthistiria australis is the " Kangaroo " Grass of Australia ; Anthistiria ciliata and Cynodon Dactylon are esteemed Indian fodder-grasses ; Tripsacum dac- tyloides, Gama-grass, in Mexico ; Gynerium argenteum is the Pampas- grass ; and Festuca jlabettaides, the Tussac-grass of the Falkland Islands, is said to be very nutritious. Saccharum ojficinarum is the Sugar-Cane; Sorghum saccharatum and Gynerium saccharoides (Brazil) likewise contain much sugar, as does also Maize, before the grain is ripened. Many Grasses are fragrant ; the Sweet Vernal-grass of our meadows, Anthoxanthum odoratum, is an example, the scent being most powerful in dried grass; Hierochloe borealis is some East- and A. Vetivert"), of which the roots are largely used. This last Grass has^ stimulating properties; and another species, A. Nardus, is called "Ginger-grass,' from its pungency. Many others were formerly, or are still locally, esteemed as medicinal, such as: Coix lachrytna^ the hard grains of which are known by the name of " Job's Tears " ; the common Reeds, Phraymites arundinacea, Calamayrostis, Arundo Donax, Triticum repens, (Couch Grass or Quitch of farmers), &c. The supposed poisonous pro- perty of Darnel {Lolium temulerdum) is not satisfactorily ascertained. GLUMIFLOR^E. 407 Among the Grasses useful in manufactures are the Bamboo (Eambusa (irundinacea), the Reed (Arundo Phraymites, A. Donax, &c.). Coarse paper has long been made from the Bamboo in India, and recently from various straws in this country. Lyyeum spartum is the Esparto Grass, much used as a coarse fibrous material, and also in the manufacture of paper. The Sand-grasses, Elymns arenarius, Anmdo arenaria, and similar creeping species, are valuable binding-weeds on shifting sandy shores. Grasses are remarkable for the quantity of silex existing in the epidermis ; and in the Bamboo a solid siliceous substance, called Tabasheer, collects in the hollow joints above the nodes. Many species are cultivated for the elegance of their flowers or their foliage, such as Arundo Donax, various species of Bambusse, Gynerium (the Pampas Grass), &c. 408 SYSTEMATIC BOTANY. SUBKINGDOM H. CRYPTOGAMIA, or FLOWERLESS PLANTS*. GENERAL MORPHOLOGY. Introductory Remarks. The division of the Vegetable Kingdom into Phanerogamia and Cryptogamia is based on the mode of re- production. It has been seen that in the Phanerogamia the plant accomplishes this by the formation of a seed of which the essential part is the embryo. In the Cryptogams, though the processes by which it is arrived at differ widely among themselves, it will yet be found that reproduction is bound up invariably with the formation of spores destitute of an embryo, and often consisting of simple cells. At the same time there exists throughout the whole Vegetable Kingdom, in Phanerogams and Cryptogams alike, another mode of reproduction called vegetative, which is entirely independent of sexuality, and which usually consists in the mere separation of a part of the mother plant. The Cryptogamia are divided into two great groups characterized by difference in the structure of their vegetative organs. The higher group, called Cormophyto, composed of the .Ferns and their allies with the Mosses and their allies, resemble the Phanero- gams in the possession of an axis or stem bearing leaves. The lower group, or Tliallopliyta, comprising the Algae, Fungi, and Lichens, presents in its vegetative structure no clearly marked distinction between root, stem, and leaf ; the plant is composed of a tliallus, formed by simple cellular tissue, sometimes in its shape resembling a leaf, sometimes a stem, and sometimes a root. The simplest plants of this class consist of single cells. Although in general the distinction between Cormophyte and Thallophyte is easily recognized, certain families on both sides possess so close an affinity to each other, that no sharp line of demarcation can be drawn between them. A similar difficulty is experienced on the lower frontier the much disputed borderland between the Animal and Vegetable Kingdoms. Cormophyta, or Cormophytal Cryptogams. The Cormophyta, as already mentioned, consist of the .Ferns and their allies, [* The sections relating to the Cryptogamia have been revised and in part rewritten by Mr. George Murray, of the Botanical Department, British Museum. Although, for uniformity's sake, the account of the Cryptogams is given in this place, yet the student will be unable to understand the anatomy and physiology of these plants without having previously mastered the contents of the subsequent sections relating to Anatomy and Physiology. ED.] CRYPTOGAMIA. 409 with the Mosses and their allies. These two groups are distin- guished from each other by the structure of their tissues. The Ferns and their allies possess a well-developed vascular system, and under the name of Vascular Cryptogams are arranged the Equisetacece, Filices, Lycopodiacece, Selaginellacece, and Rhizocarpece. The Mosses and their allies the Hepaticce (forming the class called the Muscinece) possess no true vascular system, though the tissues in the stems of Mosses have the character of vascular bundles of the most rudimentary kind. In neither Mosses nor Hepatics do true roots, in a morphological sense, occur, though they possess organs (root-hairs) which discharge similar functions. In spite of these defects in structure, the Mosses must still be looked upon as standing higher in the scale, from an anatomical point of view, than such Phanerogams as the Lemnacece^ which have neither true stem nor true root. Sexual and Asexual Stages. In their life-history Vascular Cryptogams pass through two morphologically and physiologically distinct generations a sexual and an asexual ; and this holds true of all Cormophytal Cryptogams. The spore is borne in various ways in different families ; in the familiar case of Ferns it is borne in capsules or sporangia usually on the back of the frond. When it germinates, it produces a thalloid layer of cells called the pro- tliallium, and it is on this that the sexual organs are formed. The prothallium contains much chlorophyll, and forms numerous root- hairs. It is soon in a position to nourish itself, and by-and-by produces the male (antheridia} and female organs (archegonia) (see fig. 493). The antheridia give rise to spermatozoids, which fertilize the archegonia. This is the sexual generation. Out of the archegonium springs the asexual, leaf-bearing gene- ration, which, in common language, is usually called a Fern, a Horsetail (Equisetuni), &c. It bears the spores, as described, and these in their turn again produce the sexual generation (prothal- lium), and thus the life-history proceeds in alternate sexual and asexual generations. The asexual plants possess a true vascular system, differing in details from that of Phanerogams ; and a more special description of their structure will be found under the head- ings to which they are referred. Their apical growth usually pro- ceeds from a single terminal cell. A remarkable exception to the rule of alternation of generations is found in the reproduction of Pteris cretica. Mr. Farlow * discovered that no female organs are formed on the prothallium of this Fern, though the male organs attain full development and produce spermatozoids. The leaf- bearing generation springs from the prothallium in a purely vege- * " Ueber ungeschlechtliche Keirapflauzeu an Farn-Prothallien," Botanische Zeitung, 1874. 410 SYSTEMATIC BOTANY. tative manner. This important discovery, however, cannot alter our views on the alternation of generation in Vascular Cryptogams, Reproduction of Ferns: , spore germinating; 6, more advanced (magn. 50 diam.); c, full- grown prothallium, with archegonia (lower surface) ; d, vertical section of the central region of a prothallium, passing through an archegonium and two antheridia; e, two antheridia (side view) ; f, antheridia seen from above ; g, antheridium burst (side view) ; k, sperm-cell from antheridium; i, spermatozoid escaping from sperm-cell (magn. 300 diam.); k, front view of a spermatozoid; I, vertical section of a young archegonium; w, more advanced ; n, still older, with the canal open and an embryonal corpuscle in the sac (magn. 100 diam.); o, view of the mouth of an archegonium, from above; p, vertical section of an archegonium with the embryo in course of development in the sac; q, the same, more advanced (less magnified); r, vertical section of young plant, more advanced, with a fragment of the prothallium (magn. 50 diam.); s, t, young plants of Pteris serrulata, with their first and second leaves and adventitious roots still connected with their prothallia. for such an exception cannot, from its abortive nature, destroy the rule. In the Muscinece the alternation of generations is similar to that in Vascular Cryptogams. Out of the germinating spore (in all Mosses and in some Hepaticce) comes a Protonema of a thread-like structure, on which the sexual organs are formed, or (as in most Hepaticce) the sexual generation is directly developed. It is worthy of notice that recently Drs. Pringsheim and Stahl have succeeded in bringing about an artificial production of the Proto- CKIPTOGAMIA. 411 nemia, which they caused to spring from certain parts of the asexual plant. This discovery stands in much the same relation to the alternation of generations in the Muscinece as the discovery of Mr. Farlow does to that of Vascular Cryptogams. There are, besides, different modes of vegetative reproduction in Mosses, the principal of which are by gemmae and by stolons. Thallophyta. We now come to the lower Cryptogams called Tlmllopliyta, under which name are comprehended the Algse, Fungi, and Lichens. The vegetative structure is in the greater number of cases a simple one, since the plant usually consists of a thallus in which no distinction between root, stem, or leaf exists. The class includes organisms, however, of widely different degrees of development. The lowest forms are composed of one cell, and often bear so strong a resemblance to the minute animals called Infusoria, that it is only in recent times that a satisfactory division has been established. By almost imperceptible gradations we rise to the highest representatives, in which indications of those forms called leaf and stem appear and an undoubted differentiation of tissues exists. The functions of a root, when such are necessary, are performed by root-hairs, and by a kind of sucker called a Jiaustorium in those plants which live by parasitism. The class, from its comprehensive nature, includes an extraordinary number of forms, which can, however, usually be distinguished into a com- paratively small number of groups. In their life-history Thallo- phyta cannot be brought under one general rule, as in the case of the Cormophyta. In many cases a simple alternation of genera- tions is the rule, while in others several generations form a life- cycle, links of which may, under circumstances, be omitted ; but this is the exception. In the Uredinece, for instance, three generations form the life-cycle of the plant. FUNGI. In the Fungi the vegetative body consists, with the exception of several doubtful cases, of filiform, more or less branched hyplice or threads. In many instances the thread is one long, densely ramifying, bladder-like cell; but in most cases it consists of a series of cells placed on end wdth dichotomous or lateral branches. Of such cells the large bodies of our familiar Fungi, as well as those of the minute species, are composed. The cohesion of the hyplice is usually effected by their being densely interwoven in various ways in the different plants. It must, how- ever, be mentioned that exceptions to this very general condition of things exist. There is found in the stalks of the Phalloidece, in the pileus of 2iussula, Lactarius, in Sclerotia, and in the peridia of the Lycoperdacece a kind of tissue bearing a resem- blance to the parenchyme of the higher plants ; but this resemblance 412 SYSTEMATIC BOTANY. is slight, and it has been found necessary to adopt for it the term pseudo-parenchyme. The structure and growth of the fungal cell agree in essential points with those of the vegetable cell as it occurs elsewhere. In the numerous Fungi which develop rapidly and have a short existence in the adult state, the cell-wall is thin, tender, and structureless. The possession of a thick cell-wall of a homogeneous, unstratified nature is not uncommon. Cases also occur (in the Polyporei, Thelephora, Bovista, Geaster, Tulostoma, &c.) in which, by the aid of sulphuric acid, solution of potash, or of Schultz's mixture, a cell-wall of two or more coats is found, but in certain instances simple immersion in water is sufficient to show a beautiful stratification. From the differences in chemical reaction the cell-membrane of Eungi cannot be called true cellulose, and it has therefore received the special name of fungal cellulose. The protoplasm differs from that of the higher plants in the constant absence of chlorophyll and of a nucleus. l)rops of oil and other bodies have occasionally been taken for nuclei, by Schacht, for ex- ample, who also described nuclei of such infinite minuteness that they could not be accepted. In the formation of vacuoles and the possession of fatty oils, both forms of protoplasm agree. JStarch and chlorophyll are always absent, but pigments of various colours occur plentifully. Crystals of calcium oxalate are to be met with in the intercellular spaces of many Eungi, but in only two cases have they been found in the interior of the cell (Russula adusta and Phallus caninus). Cell-division takes place in the same way as in the other plants. The reproduction of Eungi is effected by both sexual and asexual means, and the organs by which this is accomplished are in both cases simple cells. No one species is known to possess more than one method of sexual reproduction, though various asexual methods are known to occur in the same species. The organs are called by different names in the different groups, and a description of them will be found under those divisions to which they are peculiar. Spores. The term spore is used to signify a reproductive body in a general sense, and for the mother cells from which the spores are developed the word sporangium is employed. It must be men- tioned that, from the very varied modes of reproduction which are met with, a great number of special terms have been proposed in the use of which a certain amount of confusion for some time existed. The spore may be enclosed by one or more coats of dif- ferent degrees of thickness and density. When it germinates, a tube called a germ-tube is emitted, which conducts itself in different ways according to its species. The spore in some instances bursts and produces a number of ciliated spores called swarm-spores or zoospores, which also behave in different ways. The germination of CEYPTOGAMIA. 413 the spore is sometimes introduced by division of the spore by septa. The body immediately resulting from germination is called the mycelium, and usually ramifies very densely. To it belong the functions of gathering and storing nutriment. Prom the myce- lium there springs the receptaculum, on which the reproductive organs are situated. The receptaculum is, e.g. in the case of the common Mushroom, that part vulgarly considered the whole body, and it is subject to many variations in shape. The lowest forms of Fungoid life are to be found in the Myxo- mycetes. In many characters, such as the formation of spores, they agree with the Fungi ; but in others they are so far removed that the tendency is to ally them with such animal bodies as Amoeba. The plasmodium (which corresponds to the thallus of the true Fungi) is of a slimy or creamy appearance, and viewed with the microscope it reveals a number of anastomosing, net-like channels which may be compared in function to arteries and veins, and along which there courses an ever-streaming current of protoplasmic matter, bearing such foreign bodies as spores of fungi, starch gra- nules, particles of colouring-matter of different natures, &c. These channels are not confined by a definite membrane, so that a constant changing of position and direction is permitted, and this to such an extent that the plasmodia of different species have been seen to unite. By-and-by a state of rest is attained, and a capsule or sporangium containing spores is formed, which reproduce the or- ganism in a truly fungal manner. Their nourishment takes place in much the same manner as in the case of the animal Amoeba. To Professor de Bary belongs the honour of having worked out their wonderful life-history. LICHENS. Until very recently the Lichens were thought to oc- cupy a position in the Vegetable Kingdom equal in importance to that held by the Fungi and AlgaB ; but from the more intimate knowledge of their structure and life-history, obtained through the researches of Schwendener, De Bary, Stahl, Bornet, and others, it is necessary now to regard them as only an order of the great group of Fungi called Ascomycetes. The thallus and fructification are without doubt identical with those of the Ascomycetes but there enters into the composition of the Lichen another important factor in the form of minute algse on which the fungal hyphse lead a life of parasitism. The case may be shortly stated thus : The green parts of the Lichen, called gonidia, are minute algae, which gather nourishment in a perfectly normal manner. The hyphae of the fungal parasite extract this nourishment for their own use, and the balance of supply and demand is so preserved that both para- site and host continue to consort through life in a harmonious 414 SYSTEMATIC BOTANY. manner. The gonidia (algae) must be looked upon as independent organisms, imprisoned and forced to serve the double purpose of providing for themselves and their parasites. At the same time they reproduce their own species. Their specific identity with members of the genera Pleurococcus, Nostoc, &c. is well established. The parasites, on the other hand, are true ascomycetous Fungi, reproducing themselves in a strictly ascomycetous manner, and, instead of living on tissues which sooner or later succumb to their demands, have selected hosts offering the greater advantage of persistent life. Of the two components the Fungus is the superior both in bulk and nature, and it is for this reason that the Lichens must be classed as Ascomycetes. ALGLX. By excluding Lichens, as a Family, the division of the Thallophyta is reduced to that of Fungi and Algae. The Algae may be said to form a parallel Family to the Fungi. The same gradation from members which consist of a single cell to higher forms, the thallus of which possesses a structure of a more com- plicated nature, exists, and the morphological characters rising with equal step present strong marks of similarity with the parallel Family. It has been said that Algae are Thallophytes containing chlorophyll, and Fungi are Thallophytes in which it is absent ; but this classification is arbitrary and otherwise objectionable as based on subjective characters. The thallus of the higher Algae resembles that of the higher Fungi. Its histological peculiarities are not markedly different from those of the Fungi. It consists usually of pseudo-parenchyme ; and in some instances a seeming differentiation of tissue into epi- dermis and fundamental tissue is exhibited, though the so-called epidermis must be regarded as only analogous to true epidermis. The cell-walls consist of an unlignified cellulose, which shows a blue colour on the application of iodine and sulphuric acid. Many Algae are enveloped in a gelatinous substance, which is produced by a process of degradation of the cell- wall. Others again, owing to the deposition of calcium carbonate in the cell- wall or its excre- tion into the intercellular spaces, attain a calcareous structure, as in Corallina. The gelatinous substance serves as a means of fixing the plant to its station, and the calcareous or silicate coats form a valuable protection. It has been stated that the cells possess a nucleus ; but this is not well established. Starch occurs frequently, and chlorophyll, sometimes covered by pigments of various colours (which can easily be removed by cold distilled water), is constantly present. The algal cell, from 'the possession of these substances, stands individually much nearer the ideal perfect vegetable cell than the fungal cell ; and the reason is apparent ; for, whereas the CRYPTOGAMIA. 415 algal cell obtains, as a rule, its nourishment in a legitimate, indepen- dent way, the fungal cell extracts it after a more or less parasitic manner. A parasitic life, however, is not uncommon among the Algae. The large Algae (such as Focus] often attain colossal di- mensions and a tree-like form, while the filamentous plants form wavy masses sometimes of considerable length. Those Algae which consist of single cells sometimes possess the power of motion by fine cilice (as in the animal Infusoria), while sometimes they form colonies cohering by the gelatinous substance just mentioned. The reproduction of Algae is effected by both sexual and asexual means ; and these processes bear often a striking resemblance to those which occur in the Fungi. The asexual means consists usually in the separation of some merely vegetative part from the mother plant and in the detachment of gemmce. In the sexual reproduc- tion a variety of processes obtain which will be described when the families in which they occur are treated of. The Order CHABACEJS forms a link of connexion between the Algae and the Cormophyta, while on the lower frontier such organisms as Bacteria unite the lowest plants with the lowest animals. SUBKI^GDOM II. CRYPTOGAMIA, or FLOWERLESS PLANTS. Plants reproduced by spores destitute of an embryo. CLASS I. COEMOPHYTA. Cryptogamous plants usually provided with stems, leaves, and roots, or their morphological equivalents. Under this head is associated a number of vegetable forms which are closely allied to the Phanerogams in the details of their vegetative struc- ture, but which are separated from them in the processes of their sexual reproduction. Even in their reproduction there is to be observed a degree of similarity with the Gymnosperms (a group of Phanerogams), though this is of so remote a character and so different in the steps by which the point of similarity is reached that near affinity cannot be asserted of them. On the other hand, the vegetative organs are morphologically and physiologically of similar value in Cormophytal Cryptogams and Phane- rogams. Just as we have in Phanerogams a scale of degrees in the deve- lopment of the vegetative body, extending from the morphologically perfect down to the cellular plant, in which leaves, stems, and root are repre- sented by aflat thalloid formation (Lemnacece}, so we have in the Cormo- phytal Cryptogams a similar scale, in which the degrees are perhaps more strongly marked. In the Cormophytal Cryptogams the Filices re- present the highest degree in the scale, with stem, root, and leaf perhaps 416 SYSTEMATIC BOTANY. more highly developed than in any other member of the Vegetable King- dom. Passing over the less sharply marked degrees in the scale, repre- sented by other Vascular Cryptogams, we come to the Mosses, in which, though stems and leaves are present, we lose sight of the true root, the place of which, however, is supplied by organs of corresponding physiolo- gical value. In the stems and leaves, too, we no longer find the relations so perfect, since there is no perfectly organized vascular tissue, but only an indication of it. The anatomical structure of the Hepaticce is com- paratively still lower in the scale, and approaches that of the Thallo- phytes more nearly than any other Cormophyte. The life-history of Cormophytal Cryptogams consists of two distinct generations a sexual alternating with an asexual one. Division I. Vascnlaria. Cormophytal Cryptogams possessing vascular tissue. The Vascular Cryptogams consist of the Equisetacece, the Filices, the Lycopodiacece, the Selaginellacece, and the Rhizocarpece. Their life-history is composed of two alternating generations an asexual and a sexual. The asexual generation is that in which the plants are commonly seen and known, and during which they attain the highest point of development in their vegetative structure. They possess in this stage both cellular and vascular tissues, organized in some cases (the Filices) on perhaps the most perfect system possessed by any known vegetable. Shortly stated, their life-history begins with the germination of an asexually produced spore, which gives rise to a prothallium (usually a mere layer of simple cells so organized as to sustain an independent life), on which are borne antheridia (male organs) or archeyoma (female organs). The antheridia produce antherozoids or spermatozoids, as they are differently named, which fertilize the archegonia out of which the asexual spore-bearing generation springs (see fig. 493, p. 410). The Vascular Cryptogams are divided into five Orders as follows: Equisetacese. ) Fiiices. > Spores of one kind. Lycopodiaceae. ) Series 1. ISOSPOEIA. Vascular Cryptogams producing spores of one kind only. Pro- thallium growing free from the spore and producing antheridia and archegonia. EQUISETACEvE. THE HOESE-TAIL OKDEE. Diagnosis. Asexual Generation : Herbaceous plants with jointed, subterraneous rhizomes, sending up at intervals fistular-jointed TASCTTLARIA. 417 stems, bearing whorls of scale-like leaves at the joints, where they are sometimes verticillately branched. Spores borne on metamor- phosed leaf-bearing stems, terminating in a clavate joint covered with dehiscent sporanges. Spores triple-coated, of one kind, with two elastic filaments called elaters, formed by the spiral fission of the outer coat of the spore. Stem, rhizome, and root grow longi- tudinally by means of a single apical cell, giving off three series of segments. Fibro- vascular bundles arranged in a circle. No peri- cambium in the root. Sexual Generation : arising from the spores, consisting of independently subsisting, usually dioecious prothallia, the male prothallia being smaller than the female. Illustrative Grenus : Equisetum, L. Structure and Life-history. The ' Equisetacece at present existing con- sist of a single genus, Equisetum, a small group of herbaceous plants, growing chiefly in wet places, with a creeping-, subterraneous, jointed but solid rhizome (fig. 494, #), from which arise erect shoots or stems. The stems are striated lon- gitudinally, jointed at intervals, with circles of small and narrow, membra- nous, scale-like leaves at the nodes, and they are fistular like the stems of Grasses. They are also traversed by several air-canals, varying in number and disposition according to the species. The stems are sometimes simple, some- times compound, bearing whorls of branches at the nodes, which branches resemble the main stem in character, and frequently branch again in a similar manner at their nodes. The erect stems are either fertile or barren (meta- morphosed or true) ; in some species the fertile stems are short and simple, while the barren stems are tall and provided with numerous whorls of spreading co mpound branches ( E. fluviatile) . The fertile stems terminate in a kind of club or spike (fig. 494, &), composed of a short axis closely covered with spo- ranges (c) ; these are small peltate or mushroom-shaped bodies (d) attached by their stalks to the central axis, and bearing under the overhanging head a circle of vertical, tooth-like pouches (d), resembling the anther-cells of Thuja among Conifers, which burst by a vertical slit on the inside to emit the spores when ripe. The spores 2E Organization of Equisetaceas: a, fer- tile stem oiEquisetum aryense, arising from the rhizome ; b, fruit-spike (nat. size); c, transverse section of do., showing how the sporanges are at- tached to the axis ; d, a group of sporanges seen from beneath ; e, a spore ;/, the same, with its " elaters " uncoiled ; g, fragment of the branched stem of E. palustre. 418 SYSTEMATIC BOTANY. are furnished with filiform processes, called elaters (fig. 494, /), consisting of two short threads attached at one side, coiled spirally round the spore before it is mature, and unwinding with elasticity when the spore is discharged from the sporange. The erect stems die down annually, while the rhizome persists. The asexually produced spore of the Equisetaceae contains a nucleus and chlorophyll granules, and it is, perhaps, owing to this high state of internal organization that its powers of germination are retained for only a few days at the most. The first sign of germination is an enlargement of the spore and the assumption of a pear-like form, during which it divides into two cells; the smaller, possessing almost colourless con- tents, grows out in the form of a long root-hair, and the other, contain- ing the chlorophyll of the spore, by repeated cell-division ultimately pro- duces the prothallium. The prothallia of the Equisetacea3 are small, flat, thalloid (as their name implies), chlorophyll-containing bodies consisting, in some parts, of several layers of cells, and supplied with irregular arm- like lobes. On the prothallia, which are usually dioecious, are to be found the sexual organs antheridia or archegonia as the case may be. The male prothallia are usually a few millimetres long, and the female often as much as half an inch ; but, although individual in the minor details of form r different species are distinguished by differences in breadth, length, and the nature of their branching, The antheridia, or male organs, are produced at the end of the large and between two smaller secondary lobes of the male prothallia. They contain upwards of 100 large spermatozoids (the largest produced by any Cryptogam), which on being set free swim about in the water, without the presence of which they cannot be emitted. The archegonia, or female organs, arise at the base of the lobes of the female prothallia, and consist each of a few cells so arranged as to form a canal leading to an embryonic cell in the centre of the other cells of the archegonium. The central embryonic cell is fertilized by a spermatozoid through the conductive agency of the canal. Immediately after fertiliza- tion the canal cells close, and the embryonic cell begins to increase in size, and the cells of the neighbouring tissue undergo a corresponding increase in number. By-and-by the embryonic cell also divides; and'after the division has been often repeated, we begin to see differentiation in the cells, which is the result of this process. The growth proceeds by an apical cell, and a leaf-bearing shoot with a rhizome and root is soon to be seen and recognized as a young Equisetum as it is commonly to be found. When the Equisetum has attained maturity, the asexual spores (from which we started) are again borne on the erect metamorphosed stem, and so the life-history proceeds in the alternating sexual and asexual gene- rations. Affinities, &c. The well-known fossil Calamites resemble in a very striking degree the existing representative of Equisetum, not only in the tissues of the vegetative body, but even in the possession of elaters in the fructifi- cation. The plants of this Order at present existing belong all to a single genus, which is very unlike any other form of Cryptcgamous plants. In external appearance the stems have no little resemblance to those of Ephedra and Casuarina ; but their internal organization is totally different. They resemble the Grasses in having a deposit of silex in the epidermal tissues of fistular erect stems, in E.hyemale so abundant that the ashes of VASCULARIA. 419 the stem form a good polishing-powder, like fine tripoli. In their life- history these plants agree essentially with the Ferns. Distribution. The Equisetace86 are found in wet places in most parts of the globe. Calamites and other plants referable to this group occur in the Carboniferous and other rocks. FILICES. Diagnosis. Asexual Generation : Herbs with a subterraneous rhizome, or trees with an unbranched caudex, with well-developed, generally more or less divided or compound leaves, circinate in vernation, and all or part bearing clusters of sporanges (sori) upon the lower surface (fig. 495, a, b, d) or at the margins (/>), of Radulacom- mately free. These (the Sperm- planata (vert, section), magn. 100 diam. complcmata, with young (axillary) antheridia and (terminal) archegonia, magn. 50 diam. ; b, vertical MTJSCINE/E. 429 either with the archegonia, or in Fig. 498. cells) escape by the rupture of the sac of the antlieridium, and each of them emits a 2-ciliated spiral spermatozoid (fig. 497, d). In the Mosses the antheridia are larger and more elongated and cylin- drical sacs, not stalked (fig. 498, b) ; they are found in the axils of leaves, sometimes scattered, but more frequently collected in axillary or terminal bud-like structures (inflorescence), a monoecious or dioecious condi- tion. The antheridial sacs are filled with a tissue which is ultimately resolved into sperm- cells, which are discharged by the bursting of the sac (tig. 498, 6); and when these escape (tig. 498, c) they in their turn emit an active, spirally twisted, 2-ciliated spermatozoid (d). The antheridia and spermato- zoids of Mosses may be readily observed in Polytrichum com- mune, the male plants of which form their "flowers" (stellulce masculines) abundantly on every heath in. spring. The archegonia are very much alike in Hepaticae and Musci, being " " rl r>allnlE>r naaA witVi a Antheridium, archegonium, &c. of Mosses : a, ver- d cellular cases, with a tical gection of arc ^ egonium with g erm - ce ii from' Phaseum cuppidatum, magn. 100 diam. ; 6, anthe- ridium of Polytrichum commune, bursting to dis- charge spermatozoids, magn. 25 diam. ; c, sperm- cell and spermatozoid of the same, magn. 200 diam. ; d, spermatozoids of the same, magn. 400 diam. ; e, immature fruit of Phaseum bry aides (vertical section), c, calyptra, v, vaginule, magn. 40 diam. When long neck (tig. 497, a, b ; fig. 498, a), found generally several to- gether, commonly at the ends of shoots, surrounded by modified leaves, which receive special names (pp. 431, 433), forming a kind of perianth. In Anthoceros the archegonium is formed in the substance of the thalloid stem, mature the archegonia exhibit in their basal cavity a germ-corpuscle (fig. 497, b ; fig. 498, d), which is fertilized by the passage of spermatozoids down the canal of the neck of the flask-shaped body. In any case this corpuscle is converted into a cell in one of the archegonia of a flower, the rest remaining barren (fig. 497, p p}. When the germinal cell is fertilized, it begins to grow by cell-division, and forms a cellular body which causes the expansion of the original wall of the archegonium (fig. 497, e). After a time, this wall gives way, in the Mosses by a circumscissile dehiscence, so that the upper part is carried upwards (fig. 498, e, c), afterwards becoming the calyptra of the sporo- gonium (fig. 500), while the lower part (tig. 498, v) remains as the vaginule (fig. 500, c). In the Hepaticae the sac of the archegonium is usually ruptured in the upper part, and there is no cup-shaped calyptra formed, the sac becoming ultimately the envelope, corresponding to the vaginule of Mosses, here often called the epigone (p. 433, fig. 501 B, a). The central cellular body (tig. 497, e) undergoes very remarkable changes : by degrees it exhibits different strata and regions, and in the 430 SYSTEMATIC BOTANY. most perfect forms of this Class ultimately rises out on a stalk-like process from the vaginule (fig. 500, r), and becomes a sporoyonium filled with spores (pp. 431, 433). Fig. 499. Germination of the spores of a Moss (Funaria hygromefrica) : c, spore sprouting ; d, more advanced, and the first cell divided ; a and b, nascent leaf-buds on the confervoid proto- nema. Magn. 200 diam. The mode of development of the spores, which are simple cells with a double coat, or a proper cell-membrane covered by a distinct cuticular layer, is briefly as follows : In the cellular rudiment of the capsule con- centric layers of the parenchyma become differently metamorphosed : the outer layers from the walls of the capsule and the sporangial membrane below, continuous with the peristome (p. 431) above j the central mass (in Mosses) is developed into the columella; the intermediate layers, which produce the spores, after multiplying to a certain extent, form free cells from the whole contents of each cell ; the walls of the original or parent cells dissolve, and a cavity is formed, in which the free cells (parent cells of the spores) lie loose. These cells become divided into four chambers by septa ; and each of these chambers (special parent cells of the spores) produces a single free cell from its whole contents. The last-formed cells, set free by the solution of their mother cells, are the spore-cells, which when ripe are found coated with a cuticular layer, often more or less marked with points or reticulations, like polleu- grains. In the subsequent history, another kind of propagation takes place. When the spores germinate, they produce a confervoid structure (pro- tonema, fig. 499), from different cells of which are produced a number of MUSCINEJG. 431 buds (a, 6), each of which grows up into a new leafy stem, forming a tufted group of plants, which after a time fructify again by anthendia and archef/onia. MTJSCI. MOSSES. Fig. 500. Diagnosis. Sexual Generation: Plants of a diffused or creep- ing habit, terrestrial or aquatic, with imbricated leaves arranged in from two to four rows, and branching in a monopodial manner. The stems are slender and con- tain no true vascular tissue. A true root is absent, but its functions are performed by root-hairs. The sexual genera- tion arises as a lateral shoot from a protonema produced by the asexual spore on germina- tion. It bears the antheridia and archegouia the former stalked and the latter sessile on a narrow base. The Asexual Generation or sporogonium arises from the embryonic cell of the archegonium after fer- tilization by an antherozoid. Its first stage of development OrganizationofMo83es: _ A ;^^ is passed in the calyptra, which, on being ruptured at the vaginula, is carried up on the apex, where the capsule which produces the spores is formed (figs. 497, 498, 500). Within the capsule is a sterile mass of tissue called the columella. The epidermis of the capsule splits to permit the escape of the spores. Illustrative Suborders : Brya- cece, Sphagnacece, Andrceacece. In the BBYACEJE the leaves are small and scale-like and usually spirally arranged. The plants are of a csespitose or diffused creeping habit. The antheridia and archegonia are produced either in terminal buds or in the axils of leaves. From the archegonium, the outer part of which is a flask- shaped sac, arises the sporogonium, w r hich in its growth tears away the wall of the archegonium, leaving the base as a kind of collar (vaamula^ fig. 500, c), and carrying away the upper part, which becomes more deve- loped as a cap or hood (calyptra, d) this more or less encloses the urn- shaped capsule (6) until it is mature (fig. 500, A) ; the stalk of the sporo- gonium is called the seta. When the calyptra falls off it exposes the capsule, which in most cases has a deciduous lid (operculwn,f) ; when natural size ; b, its capsule, with operculum in situ,, and calyptra (d) detached ; c, the base of the seta, with the vaginule; e, capsule, with peristome, and, e', a section of the same, show- ing the columella;/, the operculum of e; h, teeth of the peristome, from the mouth of e; i, spores, on the same scale of amplification as h. 432 SYSTEMATIC BOTANY. the lid falls off, the border of the mouth of the capsule is found either naked or furnished with a single or double fringe of teeth (peristome, e, h) ; and a circular piece, called the annulus, sometimes separates from the end of the columella in this place. The number of teeth in the peristome is either four or some multiple of that number. In the capsule of Mosses is to be found a colurnella or stalk-like mass of tissue running up the centre (e r ). In the Phasceee an operculum is absent, and the spores escape on the decay of the capsule. It differs slightly in its general structure from othe*r Bryacece. Illustrative Genera : Phascum, L. j Grimmia, Ehr. ; Tetraphis, Hedw. 5 Splachnum, L. ; Dicranum, Hedw. ; Trichostomum, Hedw. ; En- calypta, Hedw. ; Bryum, L. ; Bartramia, Hedw. ; Funaria, Hedw. ; Poly- tj'ichum, L. ; Hypnum, L. ; Foidinalis, L. SPHAGNACEJE consist of the species of one genus, Sphagnum. The plants are aquatic, and are commonly known as "Bog-mosses." They are of a pecu- liar yellowish-green aspect, with imbricate (o-rowed) leaves and fasciculate branches, the lower of which are long and denexed. This genus differs very much from the Bryacece in habit and in the structure of its leaves. The chlorophyll-containing cells of the leaves are slender and elongated ; in the interstices are large empty cells, the walls of which are strengthened by a spiral fibre. This structure causes the whitish or yellowish-green colour peculiar to them and to a few similarly organized Mosses. The antheridia are globose stalked bodies and resemble those of Hepaticce more than those of Mosses. The sporogonium possesses a short turbinate seta, and a capsule which dehisces by an operculum, and is destitute of a peristome ; the columella is short and does not reach the apex. A pecu- liarity of the asexual generation is the existence of sporogonia bearing spores of a smaller size than the ordinary large spores. This Order is remarkable for the share it takes in covering bogs and gradually furnishing material for peat, the lower parts of the stems gradually dying away below while the summit ascends ; the descending lower branches of the fascicles bind the whole into a compact mass. They abound in cold and temperate climates in boggy places, furnishing an article of food to animals, and even to man in northern regions. ANDRJEACEJE are csespitose Mosses with erect stems and imbricate leaves, and are natives of mountains and polar latitudes. The sporogonium has constantly a terminal position on the stems of the sexual plants and is destitute of a seta. The capsule is sessile on the receptacle where the vagimda arises and bursts vertically into four valves, which remain con- nected at the apex. A columella is present. In Acrodiisma, a genus from the Antarctic regions, the valves separate only halfway down, as in the Phascece (Bryacece), in which Archidium, like ^Andrcea, does not ele- vate the capsule on a seta, but carries up the calyptra simply by the ex- pansion of the capsule. In the 4-valved dehiscence it agrees with the Jungcrmanniacece (Hepaticce). Illustrative Genera : Andrcea, Ehr., and Acrochisma, Hook. til. 433 Fig. 501. HEPATIC^. The Scale-mosses are minute creeping plants with small, green, cel- lular (scale-like) leaves, imbricately arranged along the axis in two rows, often with a row of imperfect leaves (ampldyastria, fig. 501, d) on the underside ; or with the stem thalloid, i. e. forming a lobed leaf- like mass. The sporangia have oval capsules breaking through the summit of the calyptra, raised on a thread-like seta, and splitting ver- tically when ripe into 4 valves, which separate more or less widely into the form of a cross (tig. 501, B) ; scattering spores mixed with elaters, destitute of a columella. The Jungermanniese (or foliaceous Hepaticae) have slender ramified creeping stems like those of branched Mosses, being more delicate, with leaves imbricated in a distichous manner, so as to give a flattened character to the branches (fig. 501, B, d). The antherldia and archeyo- w'aare produced on these stems ; and from the latter are developed the spo- royonia, which are surrounded at the base by modified parichcetial and periyonial leaves and by a vayinule (fig. 501, B, ), which differ* from tli at of the Mosses in being the en- tire sac of the archegonium, no hooded calyptra being carried up in the Jungermanniere. The vayinule is sometimes called calyptra, and sometimes epigone \ the circle of leaves, often confluent, surrounding it form the periffone, perianth, or involucel ; and these are surrounded by the pericJustial leaves, pericha- tium, or involucre. The capsules are generally elevated on thread-like stalks (seta), and when mature split nearly or quite to the base into four teeth (fig. 501, 6), which spread out more'or less, and set free the spores and elaters (c). There is no columella. The genera of this Order, formed out of the old genus Junyermannia, present a considerable variety of conditions, both as regards their vege- tative structure, which is either frondose or foliaceous, and the minute details of the organization of the calyptra (epigone), with the involucel (perianth or periyone) and the involucre (perichcetium) which surround it. We have here a higher condition of the vegetative organs, nearer that of Mosses. The Jungermanniese are found in shady woods and moist situations throughout all regions of the globe, and are most abundant in damp tropical woods. They have no important qualities. The ANTHOCEROTE^: are distinguished from the frondose forms of Jun- germanniese by the absence of an involucel (periyone). The anther idia Organization of Jungermanniaae : B. Hadula. complnnata with an unopened and a burst capsule : a, the vaginule ; b, the burst capsule, magnified; c, spores and elaters ; d, fragment of the leafy stem of Jungermannia, umbrosa, showing the distichous arrangement of the leaves, and the amphignstria (e). 434 SYSTEMATIC BOTANY. Tig. 502. and archegonia are produced in cavities excavated in the thalloid stem ; and from the archegonium springs a thread-like or pod-like capsule, which splits down longitudinally into two valves when ripe, and displays a central columetta, and has both spores and imperfect elaters. Illustrative Genera : Metzgeria, Radd ; Blasia, Mich. ; Frullania, Nees ; Trichocolea, Nees ; Geocalyx, Nees ; and Jungermannia, Dill. The MARCHANTIEJE, or Liverworts, are minute green plants, with a stem in the form of a lobed, leaf-like, cellular expansion, rooting by capillary filaments below, with an indistinct midrib ; the sporogonia de- pending from the underside of a capitate or radiate receptacle supported on a stalk arising from the apex, on the under surface, of the lobes of the frond ; the capsules bursting by teeth or by irregular fissures, containing elaters mixed with the spores, but no columella. The Thalloid Hepaticte have a broad, more or less succulent, lobed, leaf-like expansion in place of stem and leaf (fig. 502) ; this is to be regarded as a foliaceously developed stem analo- gous to that of Lemna among the Phanerogamia. The sporogonia borne by the tlialloid forms are very varied: the Pelliece, or frondose Jungerman- nieae, bear capsules like those just described, but arising from the midribs of the thalloid stem ; the Anthoceroteae, Riccieae, and Marchantieae are very different. The thalloid expansion of the Marchantiese sends up stalk-like processes from its marginal sinuses (fig. 502, A), terminating in simple or divided cap-shaped bodies (receptacles), on the underside of which are found the archegonia ; the antheridia are in distinct heads ; the archegonia develop into the capsules of the sporogonia (6), which usually burst at the apex (c) into four teeth, sometimes into eight ; in certain genera a lid sepa- Organization of Marchan- rates by transverse dehiscence, and in others the : ~ A ' Marchantm v~ capsule bursts irregularly ; the capsule has no colu- mella, and its spores are mixed with elaters (d). The Marchantieae produce cellular bulbils or gemmae. These are especially remarkable in some of the thalloid forms, as in Marchantia, where they are developed in groups in special cup-like receptacles. The Marchantieae grow in damp shady situations in all climates. Illus- trative Genera : Fegatella, Radd ; Plagiochasma, Lehni. j and Marchantia March. The RICCIACE^; are inconspicuous Marchantia-liliQ Liverworts, o-rowiuo- in mud or floating on water, having a delicate cellular leaf-like "frond,* with the sporogonia, without an involucel or involucre, immersed in or sessile on the frond, bursting irregularly, and containing no elaters. The antheridia and archegonia are also imbedded in the substance of the tacle of fruit ; b, vertical section of the receptacle, showing the sporanges on its under surface ; c, spo- range bursting, with its vaginule and perigone laid open ; d, spores and elater, highly magnified. ALG.E. 435 thalloid stem. From Anthoceroteae they differ in the absence of a columella and of rudimentary elaters. They are interesting as exhibiting the lowest type of organization in the Class to which they belong. They are generally diffused, comprising 8 genera, with about 28 species. Genera : Eiccia, Mich, ; Duricea, B. and Mont, j Sphcerocwyws, Mich. CLASS II. THALLOPHYTA. Definition. Cryptoganious plants producing in vegetation a thallus, presenting no opposition of ascending and descending axis, nor contrast of stem and leaf ; antherozoids never spiral ; repro- duced by spores which are produced in parent cells, either forming part of the vegetating thallus or growing upon the surface of defi- nite regions of the thallus devoted to reproduction. Spores not producing a prothallium, but reproducing the plant immediately. These plants correspond to the Thallogens of most authors ; their prin- cipal points of distinction from Cormophytal Cryptogams are above given. The vegetative structures of the plants of this group, which form their principal bond of connexion one with another, and their most striking cha- racter of distinction from the higher plants, present a great variety of conditions within their own limits. The thallus is a purely cellular ex- pansion, presenting no contrast of parts analogous to that between the axis (stem) and the appendages (leaves and their modifications), which exists in the higher plants ; hence they are necessarily devoid of true buds. A special regularity, however, and a determinate direction of growth are manifested more or less clearly in all cases, giving definite and character- istic forms to the thallus. This is the case even when the thallus is reduced to the condition of microscopic filaments, which elongate and spread in determinate directions. The thallus is exclusively composed of cellular tissue ; and its more minute differences in the various classes and families of this division of the Vegetable Kingdom require microscopic inves- tigation ; but certain broad distinctions may be laid down, sufficient for the general discrimination of the classes in the more perfect forms. The lower forms of the two classes of Thallophyta approach very closely in their characters, on account of their great simplicity of organization, which excludes the possibility of many differential characters. Division I. Algae. Gymnosporous Cryptogams living in water or in damp places exposed to the light, extremely variable in size, form, colour, and texture, free or attached by root-like organs, sometimes uni- cellular, at other times having a branched pseudo-stem and leaf -like appendages, sometimes of large size, but exclusively cellular in structure and destitute of stomata. Plants multiplied by subdivi- 2x2 436 SYSTEMATIC BOTANY. sion of cells or by the formation of " zoospores." Keprocluction or formation of spores effected by the antherozoids emitted from the antheridia, either on the same plant (monoecious) or on different ones (dioecious). Spores motionless, solitary, or in groups of four in a single sporange. General Remarks. The most familiar examples of this Class are the Seaweeds ; but it also includes a great number of plants found in fresh water and in damp situations, many of which are altogether of micro- scopic dimensions, and invisible, except in quantity, to the naked eye. Fig. 503. Algffi. A. Oscillatoria autumnalis : a, filament escaped from the sheath, b (magn. 300 dia- meters). B. Desmidiece : a, Pediastrum Boryanum; b, Cosmarium margariiiferum (200 diam.) ; c, Closterium Lunula (30 diam.) ; d, Closterium acerosum in conjugation, with the resulting spore (200 diam.). C. Diatomacece: a, Diatoma vulgare; b, end view of a cell (200 diam.). D. Volvocinea: Pandorina Morum (100 diam.). E. Botrydium granulatum (15 diam.). The lowest forms, the Palmellece, consist of simple cells, of most varied shapes, usually found connected together in definite or indefinite masses by gelatinous excretion or products of the decomposition of the older cells (figs. 504, 512, E, a). The individual cells, each often representing a distinct plant, are characterized by a wonderful diversity and, in certain families, beauty of form, as in the Desmidees and Diatomacece (fig. 503, B, C) ; sometimes, a& in the Volvocineae, they are provided w r ith vibratile cilia, and exhibit an active spontaneous motion (fig. 50o, D). As a rule ALGrJE. 437 their colour is green, an important exception to this being formed by the Diatumacece, which have another special peculiarity in the existence of a siliceous deposit in their walls, which remains as an indestructible skeleton after the decay of the organic matter of the plants. Some of these lower Algaa are found of red colour ; but in many cases, at least, this colour is only characteristic of certain stages of growth of kinds which are green when vegetating actively. It is very probable that most of these so-called unicellular or pseudo-unicellular Algae are really not independent organ- isms, but stages of growth of some other plant, perhaps of much higher structure. Thus there is reason to think that these unicellular bodies may not only be stages in the development of Lichens, but even of Mosses. One remarkable point in their history is the length of time they persist unchanged. A step forward in complexity of organization is made in the filamentous Algae, composed of cylindrical cells attached end to end, and thus forming long jointed tubes, either simple or more or less branched (fig. 512, C, p. 451) : the Confervoideae and their allies, the " silk-weeds of fresh- Fig. 504. Palmetto, cruenta: a, mass of jelly with" single cells, some dividing into two ; ft, detached cells and granules; c, cells treated with sulphuric acid and iodine, showing the cellular and granular contents. water pools, afford familiar examples of this structure ; these grow at the extremity of the filaments, or interstitially by all the joints elongating simultaneously. The Ulvece have a thallus where growth in breadth is added to that in length ; some of them also acquire a certain thickness : in this way they become leaf-like expansions, of membranous texture. They grow by ad- ditions all round the margins of the anterior part, often lobed or divided, but of homogeneous tissue throughout : the form and dimensions of the thallus become more or less definite here ; the colour is mostly green, as in the Oonfervoide. The Red Seaweeds or Rhodospermeae exhibit almost every possible form between that of the branched filamentous thallus and that of a highly compound or dissected leaf (fig. 510, p. 447) or a shrub-like collection of firm branches ; and, moreover, the texture of the thallus varies from a simply membranous to a cartilaginous or even horny substance, caused by greater development of the cellular tissue, which in the higher kinds exhibits a distinction between the cortical or epidermal layer and the internal spongy parenchyma. The Corallines, which belong to this group, acquire a stony character from the deposition of carbonate of lime in their cellular tissue. 438 SYSTEMATIC BOTANY. The colours vary in this Order; they are red, purple, brown, olive, &c., but never pure green, like the Confervoids. The Olive-coloured Seaweeds, including the Fucaceae (of which the " Bladder-wrack " is the commonest example), and others of very different organization, the Phaeosporeae and Dictyotaceae, exhibit a similar grada- tion of form in the thallus. The lower forms of Phaeosporeae present tufts of branched filaments ; the higher forms of these, and the Fucaceae, have thick leaf -like or stem-like fronds of firm texture and sometimes enormous dimensions ; many of them have a shrubby habit of growth, and attach themselves to stones &c. by discoid or branched expansions from the base, resembling superficially the roots of the higher plants, but having no similar function or anatomical character. The thallus of the larger forms is highly developed as to its tissues, having a distinct cortical layer ; but the structure is strictly cellular, without a trace of woody fibre or vascular elements. The colour is here usually olive, brown, or some dull tint of green-brown ; never bright green, as in the Confervoids. Vegetative reproduction assumes a very important place in the multi- plication of all Thallophyta. Throughout the Algae it is a constant phe- nomenon, and one illustrating very beautifully the physiological homoge- neity of the thallus. The lowest forms multiply by dividing into a number of cells or segments which grow up to the dimensions of the parent ; this occurs as the ordinary mode of growth, here confounded with reproduction, in the Palmdlece (figs. 504, 512, B, , 6), Desmidiea, Diatomacea (fig. 503), &c. But another still more remarkable form of vegetative reproduction extends from these up to the highest Algae, namely the reproduction by zoospores. This consists in the conversion of the semifluid contents of in- dividual cells (the endochrome) into distinct corpuscles, and the expulsion of these from the thallus by the bursting of the parent cell-membrane (fig. 506, 509, 512, 0, d) ; these corpuscles are filled with green or olive- coloured matter, except at one end, which is provided with cilia and is sometimes spoken of as the " rostrum." The cilia are excessively minute, and vary in number in different genera ; sometimes the whole surface of the zoospore is covered by them. These zoospores are usually emitted at a fixed hour in the morning, as the result of an endosmotic action which causes the cell-wall to burst and set free the zoospores. Sometimes before their liberation they are seen to congregate in one portion of the cell, and, as it were, to strike against the cell-wall and cause its rupture. Their activity seems to be directly dependent on the influence of light. After moving spontaneously for some time, the zoospores lose their cilia, become encysted, and grow up into new thalli. In Botrydium and Acetabularia conjugation of the zoospores has been recently observed. In some Algae, moreover, there are two sorts of zoospores large ones, called macrozoo- spores, and smaller ones, called microzoospores. Pringsheim even describes a form of zoospore which has the faculty of remaining dormant for long periods, and even of resisting desiccation for several months, at the expira- tion of which time, if circumstances be favourable, it germinates and forms a new plant. To such zoospores the name of chronizoospore has been given. The formation of zoospores may take place in any or all of the cells of the thallus of the filamentous and foliaceous Confervoids ; it occurs in certain definite parts of the thallus of the Phaeosporeae, where there is a difference in the constituent tissues. It has not been observed in the Red Seaweeds or the Dictyotaceae where, however, a distinct kind of organ is found, ALG.E. 439 called a tetraspore (fig. 510, c), which appears to be the representative of gernmiparous reproduction, nor in Fucaceae, where the only known kind of reproduction is by sexual organs. Sexual reproduction has been made out clearly in Algae belonging to the Confervoid and Fucaceous groups, and in the Rhodospermeae. The Phaeosporeae at present are only known to produce zoospores. The essential phenomenon throughout is the emission from an antheridium of antherozoids which are endowed with a power of locomotion, and ultimately come into contact with a cell, which, in consequence, develops into a spore, which may be one of the ordinary cells of the thallus set apart for this purpose, or may be contained in a special fruit. In the Confervoideae, where the spores are developed from ordinary cells, there are no special reproductive organs ; the spores formed in the impregnated cells acquire thick coats (fig. 512, d), usually assume a red or brown colour, and are set free by the decay of the parent cell. In the Fucaceae the fructification is limited to definite parts of the thallus. In Fucus or Halidnjs (fig. 51]), which may be taken as ex- amples, the reproductive structures are formed at the ends of the lobes of the thallus. Externally the lobe (called the receptacle) presents a thickened appearance, marked with numerous distinct orifices (fig. 511) ; these orifices lead to chambers imbedded in the thickness of the thallus (called conceptacles, b), bearing on their walls cellular sacs of two kinds one, the larger (spore-sacs, e), containing the spore-germs, the smaller (antheridia, c) containing spermatozoids (d) or impregnating corpuscles ; both kinds of sacs burst and discharge their contents when ripe, and the spores are fertilized and encysted while swimming freely in the water. The Rhodosperrneae and Dictyotaceae, besides tetraspores, have spore- sacs and antheridia, mostly collected in " fruits " of definite form, some- times in patches or lines (sori) on the surface of the thallus, like the sori of Ferns, sometimes imbedded in definite groups in its substance (called favellce), sometimes projecting more or less from the surface or margins of the thallus (fig. 510, D, d, E), when they are naked or surrounded by a gelatinous or cup-like involucre (favellidia, coccidia, ceramidia). The antheridia are usually found arranged in groups in similar situations (tig. 510, F, ) ; and the tetraspores are either scattered or collected in fruits analogous to those containing the spores and antheridia (fig. 510, 13, c). The antherozoids are immobile, and fertilize the sporange by means of a special tube projecting from the latter and called the tricho- f/yne. Transformed branches containing imbedded tetraspores are called stichidia. The sexual organs are often found on distinct plants, which are thus dioecious. The Oscillatoriaceae are at present only known to increase by division that is, vegetatively ; the Phasosporeae, again, are only known to propagate by 'liberation of zoospores from special cells of the thallus. The Dictyotaceae and the Rhodospermeae produce a peculiar kind of vegetative offset called a tetraspore, a body formed mostly in special loca- lities or in groups, and consisting of a parent cell divided' into four cham- bers, the contents of which, when set free from the parent plant, grow up at once into a new thallus. Besides the tetraspores, they have spores and antheridia. The antheridia produce minute, ultimately free vesicles, spermatozoids or antherozoids, according to Thuret devoid of cilia and 440 SYSTEMATIC BOTANY. motionless ; Derbes, however, asserts that he has observed them moving like undoubted spermatozoids. The antlieridia are generally found in distinct plants from the spores, and the tetraspores in a third series of forms of the same species. Where the sexuality of the Algse has been ascertained, we meet with the process of fecundation under three different forms, and these forms in subordinate modifications. The three forms of the process are : Conju- gation, or complete union of a sperm-cell and a germ-cell, originally undistinguishable from each other by visible structure, occurring in Dia- tomacese and some Confervoidese ; Fecundation of naked germ-corpuscles by ciliated spennatozoids, which in the Confervoideae occurs within the parent cell of the spore, and in Fucaceai after both the germ-corpuscle and the spermatozoids have been cast off by the parent ; and Fecundation of naked germ-cells by motionless ovoid or globular spennatozoids through the medium of a special tube or trichogyne, as in Rhodospermese. The importance of these phenomena to the whole theory of reproduction in plants renders it necessary to give a particular account of the processes as occurring in certain well-ascertained cases. Conjugation. In Diatomaceee (including the Diatomece and Desmidiece], the ordinary mode of multiplication of the plants is vegetative propaga- tion, by division, resulting either in the formation of connected " families " of cells (fig. 503, C) or of an increased number of separate cells, or by the extrusion of zoospores,^ which are developed into new cells or cell-families (fig. 503, B, a). This kind of propagation goes on actively for a time under favourable circumstances ; and the mere " division," at least, may be compared to the vegetative development of more complex plants. But at certain epochs this mode of increase is exchanged for another kind, in which we have cooperation of two originally distinct cells to produce the new one, indicating that it is a phenomenon of sexual repro- duction, while at the same time there is no external evidence of difference in the concurrent cells. The genus Closterium (fig. 503, B, c) is multi- plied vegetatively by division, Qvfissiparous propagation ; at certain stages of existence, however, the cells which appear as if about to divide approach in pairs, and, a fracture of the external cell-membrane having taken place at the usual line of division, the contents of each cell, bounded by a pri- mordial utricle, escape, come into contact with each other, and become con- fluent into a mass which assumes a rounded form (fig. 503, B, d). This round body becomes coated by a cellulose coat, and ultimately by a second, more internal. Its contents change from a green to a brown or yellowish colour ; and the globular cell remains after the two empty parent cells have decayed. This globular body, which passes through a stage of rest before germinating, is sometimes called a sporange, not a simple spore, since its contents appear to become segmented and divide into a num- ber of independent germs when the structure recommences active deve- lopment. An analogous conjugation of two cells takes place throughout the Desmidiece, and it has also been observed in many Diatomece ; in all cases the product is a resting sporangial cell or frustule, i. e. a cell possessing more than one firm coat, which produces two or more germs when about to throw off these coats to develop into a new plant of the form of the parent. Conjugation exhibits many minor variations in the groups of ALG^E. 441 Dcsmidiece and Diatomea ; and among unicellular Algaa it has been ob- served in the zoospores of Botrydium. In Spirogyra (tig. 512, A, a}, Zygnema, and Fiff. 505. one or two other genera of filamentous Confer- voids, ordinary growth by cell-di\ ision is ex- changed for a process of conjugation at certain epochs. Two filaments, lying side by side (tig. 512, A, J), exhibit papillary elevations of the cell-walls on the sides next their neighbours: these processes elongate until they come into contact; they then adhere, and the septum formed at the plane of union becomes absorbed, so that the two cells become connected by a tubular process, a kind of isthmus. The contents of the cells meanwhile retract themselves from the wall, lose their spiral appearance, and be- come condensed into a mass ; then, in some cases, the whole contents of one cell travel through the isthmus into the opposite cell (c) j in others, the contents of both pass into the isthmus, which expands into a globular cavity in the middle. In either case the contents of the two cells be- come combined, and they form a globular or oval spore, which produces two or three firm coats, enters a stage of rest, and remains after the pa- rent filaments have decayed away (fig. 512, A, d). After a time, usually in the spring succeeding the formation of the spore, this germinates, bursting its coats and sprouting out into a new filament like the parent (tig. 512, A, e). This conjugation of Spirogyra and its allies has long been known, and was without a parallel for many years ; but, as stated above, an analogous process occurs in Diatomece and jDesmidiea and other plants, and it is essentially related to the processes of fecunda- tion by spermatozoids next to be described. Fecundation by Spermatozoids. The history of the fertilization in CEdoyonium is one of the most curious points in the whole range of vege- table physiology, especially so as regards the male organs, which undergo a complex course of development as follows. On the same plant that produces the female spore, or in some species on another individual, are formed special cells called " microgonidia " or " androspores." The office of these cells is to produce ultimately an- theridia, in which latter spermatozoids are formed. The androspores are formed in the ordinary cells of the plant, and escape from them by rupture of the walls of the parent cell as an oidinary zoospore would do, and like it they swim about in the water for (Edogonium ciliatum : A, ordi- nary cells, in each of which a zoospore (E) is formed; C, C, sporangia; B, B, an- drospores, one bearing at a an antheridium, the lid of which is detached; D, ex- tremity of the plant. 442 SYSTEMATIC BOTANY. a time ; but while an ordinary zoospore after a time germinates and forms a new thallus, the androspores attach themselves to the sides of the female spore or sporangium. In this situation they grow into a sort of prothallus ; the lower part becomes dilated or pear-shaped, while the upper extremity develops one or two small cells one over the other. These are the antheridia ; and in each of them is formed a spermatozoid, the fecundating body. These latter, when mature, are ciliated and butt against the top of the anthe- ridium, and at length cause its detachment in the shape of a little lid. In this manner they escape from the antheridium, move about for a time in the water by means of their cilia, and ultimately pass into the female spore through an opening previously specially prepared for its passage in the summit of the female spore. Here the spermatozoid comes into con- tact with a quantity of colourless granular mucilage formed in that situa- tion prior to fecundation, the distention consequent on which seems to account for the formation of the aperture through which the fecundating body passes. The spermatozoid touches the mucilage, or even penetrates it to some extent, and becomes blended with it, and thus fertilizes the spore, which subsequently becomes invested by a cell-wall in the ordinary way. Vaucheria is a genus of filamentous Confer void Algae, in which the long branched filament consists of a single enormously developed cell. This Fip;. 506. VaucJieria: A, A, spermatozoids ; B, C, horn-like antheridium ; D, D', sporanges; E, spore. plant is commonly propagated by a peculiar kind of zoospore discharged from the thickened end of the filament or of its branches. But at certain epochs lateral structures are developed at the sides of the filaments, as branch cells, which become shut off from the main tube by septa ; some of these processes expand into ovate and beaked or bird's-head-shaped bodies, others into short curled filaments or " horns." The former are sporanges, the latter antheridia (fig. 506). When ripe, the antheridia or "horns" discharge their cell-contents in the form of numerous spindle- shaped corpuscles, moving actively by the help of a pair of cilia. Mean- while an orifice is formed in the "beak of the sporange, and some of the spermatozoids make their way in, so as to come into direct contact with the cell-contents. This phenomenon is followed by the closing-up of the sporange by a membrane, and the conversion of its contents into a fertile restinc/-spore. Spliceroplea is another genus of filamentous Confervoids, composed of two rows of cylindrical cells, in which fertilization of the resting-spores by spermatozoids has been directly observed (Cohn). In some of its cells ALGJE. 443 the contents are converted into a number of globular bodies, in others the contents are developed into numerous spermatozoids. When mature, orifices are formed in walls of the cells of both kinds ; the spermatozoids escape from their parent cell, and make their way in through the orifices of the parent cells of the spores ; the latter when fertilized produce their cellulose coat and ripen to resting-spores, which are set free by the decay of. the parent filaments. Analogous phenomena have been recently observed in various other filamentous Confervoids, as in CEdoyonium, Bulbochcete ; and Cohn has described a similar process in Volvox. The mode of fertilization in the Florideas, or Red Seaweeds, has been well made out by MM. Thuret and Bornet, who thus describe the process in Helminthora. A small cell, originating on the side of one of the dichotomous filaments of which the frond is composed, elongates, divides transversely, and becomes a short branchlet made up of four superposed cells, of which the uppermost alone continues to develop. Shortly there may be seen projecting from the summit of this uppermost division a little protuberance, which gradually lengthens into a long hyaline hair, often dilated at the extremity. This is the trichogyne or essential organ of fertilization. When the spermatozoids (here globular and motionless) come into contact with the upper part of this hair they adhere to it. Then the cell which forms the base of the trichogyne swells and divides into segments, and is soon transformed into a small cellular mass, which gradually forms the young " cystocarp " or mass of spores. The trichogyne gradually disappears. In Callitkam- nion the aggregations of spores called Fig. 507. favellce are formed from the side, not at the base, of the trichogyne, in consequence of fecundation by the antherozoid. Here, then, we have motionless antherozoids formed in the antheridium of One plant, escap- ing and coming into contact with the free end or style-like process of another plant; and, as a result of this contact, the cell at the base divides and subdivides into a mass of spores. The observations made by Thuret on Fucaceoe are very decisive. In this Order the conceptacles produce in their interior bodies of two kinds, antheridia (fig. 511, c) and spore- sacs (fig. 511, e), either together Or in Development and fertilization of spores of separate conceptacles (monoecious), or in separate plants. The anthe- ridia discharge 2-ciliated spermato- Z'nds (fig. 511, d), which are poured out through the pores of the recep- tacles (fig. 511, a) into the surrounding water. At the same time the spore-sac (fig. 511, e) bursts and emits an inner sac (fig. 507, a), in which may be observed 2, 4, or 8 (a) spherical corpuscles, destitute of a cellulose membrane ; this inner sac breaking loose, bursts and discharges its cor- fucus vesiculosus : a, inner spore-sac burst- ing from the outer sac and about to liberate the spores ; 6, a free spore (devoid of cellu- lose coat) surrounded by spermatozoids ; c, impregnated spore with a cellulose coat ; d, the same germinating. Magn. 160 diameters. 444 SYSTEMATIC BOTANY. puscles, which, like the spermatozoids, pass through the pores of the receptacle into the water. Here they become surrounded by a cloud of spermatozoids (fig. 507, b), which attach themselves to the surface, and by their ciliary movement cause the spheres to revolve. In the course of a few minutes, usually, a cellulose membrane is formed upon the surface of the globular corpuscle (by secretion from its primordial utricle ?), and it becomes a cell (fig. 507, c), which subsequently ger- minates, growing by cell-division (fi^. 507, d) into a new frond. These observations upon the fertilization of the germinal corpuscles of the Algae are of extreme interest, both as offering examples of the process of sexual conjunction, and as affording, like the development of zoospores, beautiful illustrations of the theory of free-cell formation by the produc- tion of a cellulose coat around a naked primordial utricle after it has been completely separated from the parent, a phenomenon rarely met with in the higher plants, where this kind of cell-formation can only be observed in the interior of the parent structures, as in the embryo-sac of the Phanerogamia. In the conjugating Algae we observe the new cell to be produced by the complete union of the entire contents of the sperm-cell and germ-cell, which are undistinguishable from each other. In the other kinds cited, the contents of the germ-cell become converted into one or more globular corpuscles, rudimentary spores ; while the contents of the sperm-cells are developed into numerous minute corpuscles, usually of a spindle shape (not spiral), moving actively by cilia. The corpuscles of the germ-cells acquire a cellulose coat and become cells j the spermatic corpuscles dis- appear after they come into contact with the nascent spores, either dis- solving or becoming absorbed into the substance of the latter. CHABACE^E. Class Algae, Endl AIL Algales, Lindl. Diagnosis. Water plants having verticillately branched stems, rooting more or less at the joints ; the stems either simple tubes, or with the central tube clothed by a cortical stratum of smaller tubes which grow over the internodes from the top and bottom and meet so as to envelope it. Reproductive organs of two kinds, found on the whorls of branches : (1) axillary oval sporangia (nucules), consisting chiefly of a central cell with a cortex of spirally wound tubes ending in a crown of teeth above ; and (2) little globular anthericlia (globules), sessile on the branches, bursting when mature into 8 triangular valves, the centre of each valve bearing a stalk whence arise microscopic, jointed, confervoid fila- ments, each joint of which gives birth to a 2-ciliated filamentous spermatozoid. The nucules fall off, germinate, and produce new plants. Illustrative Genera : Nitella, Ag. ; Tolypella, A. Br. ; Lychnothamnus, E,upr. ; Char a, L. Structure and Life-history. The reproductive organs of this Family are very distinctly characterized, and borne in a conspicuous external 445 position. The two kinds, male and female, called respectively the globule and the nucule, occur either together on the same branch of the plant, on distinct branches, or on separate plants. Pi. 508. B Ohara fraqilis. A. Portion of branch : a, adult globule ; S, nucule, c, its crown of teeth; /3 |3", sterile branchlets : X 50. B : a, globule in course of formation; s k, young nucule; w, nodal cell ; u, basal cell between the base of the globule and of the nodal cell ; br, cells of branchlet covered with cortex: X 350. (From Sachs.) The globule, or aniheridium (fig. 508), is a spherical case composed of eight* triangular segmental pieces, each of which is formed of a number of cells radiating from a central one ; all these have red or orange con- tents, imparting a colour to the globule as seen in its natural condition. From the central cell of each valve projects inward an oblong cell, the manubrium (fig. 509). These eight cells meet in the centre together with the apex of a flask-shaped cell which enters the globule at its base, forming the pedicle by which it is attached to the branch. Where these nine cells meet in the centre is found a little cellular mass, from which arise a number of slender jointed filaments. When the globule is mature, its valves separate, and each carries away its central cell, bearing a tuft of the jointed filaments. The cells forming the joints of these filaments are then seen each to contain a minute spirally coiled thread (fig. 509), which makes its way out and appears as a 2-ciliated actively moving spermatozoid, resembling those of the Mosses. The nucule (fig. 508, S} consists essentially of a large oval cell surrounded by a double coat and, outside this, by rive spirally coiled and intimately 446 SYSTEMATIC BOTANY. connected cortical filaments. The five spiral cells terminate at the summit in five (or ten) teeth ; and it appears that these teeth separate from each other at a certain epoch, leaving a free passage down the centre to the wall of the central celt. In this state we may compare the structure to Fig. 509. "Nilella flexiKs. A, manubrium of segment of globule, with numerous filaments in which the antherozoids are developed; B, portion of filament, very highly magnified; C, anthe- rozoids. an archegonium, or to an ovule of Phanerogamia. The spermatozoids from the globule pass into the canal between the crown of teeth of the nucule, and cause it to become fertile. The product, however, of the fertilized central cell is not a free embryo or a spore, but it becomes itself the first cell of the new plant, like a spore. After fertilization the nucule drops off from the parent, passes through a stage of rest, and in the following season germinates like a seed or spore and grows up at once into a new plant. Pringsheim, however, states that the spore develops a true prothallus like that of the Mosses.' Distribution, &c. The Characese grow in stagnant water, and many of them acquire a dull aspect and brittle texture by becoming encrusted with carbonate of lime, apparently precipitated from calcareous matter in the water, since it is often deficient in cultivated specimens. The un- encrusted kinds, the simple tubes of Niiella, and the young shoots generally are well known as objects displaying in a beautiful manner the rotation of the cell-sap, which takes place throughout these plants. The abundant protoplasmic cell-contents cause these plants to give off a very offensive odour when decaying. The species occur all over the world, most commonly in temperate climates. They have no known uses, and are regarded as noxious from their smell when undergoing decomposition. EHODOSPERME^E on FLOEIDE^E. BED SEAWEEDS. Class Algae, Endl. Att. Algales, Lindl. Diagnosis (Fig. 510.) Marine Algae, mostly of a reel-purple, rarely olive or brownish colour, with a thallus either foliaceous or of branched filaments, sometimes encrusted with carbonate of lime. ALG.E. 447 Keproduced by spores (E) formed in special sporangia, which are either superficial or plunged in the frond, and contained within special cavities or " conceptacles " (D) of varied form. The sporange is provided with a special tube, or " toieihogyne" by means of which Fkr. 510. Oiganiz&tion of Khodospermeae : A. Pait of a thallus or frond of Laurencia pinnatifida. B. A magnified fragment of a lobule with stichidia containing tetraspores like c, a more magnified figure. 1). Lobule of the frond bearing ceramidia or spore-conceptacles : d, the spores. E. Spores from the same, more magnified. F. Lobule of a frond bearing anthe- ridia, a. it is fertilized by the antherozoid ; accompanied by antheridia (P), containing a single motionless antherozoid without cilia, and by tetraspores (B, c), collections of 4 cells formed in special parent cells in similar situations to those of the spores. Illustrative Suborders: Subord. 1. KHODOMELE.E : Mhodomela, Agh. ; Polysi- phonia, Grev. Subord. 2. LAUEENCIE^ : Laurencia, Lamx. ; Ghy- lodadia, Grev. Subord. 3. COEALLINE^E : Corallina, Tournef . Melobtsia, Lamx. Subord. 4. DELESSERIEJE : Delesseria, Lamx. Plocamium, Grev. Subord. 5. SPH^EOCOCCEJE : Plocaria, Nees Splicer 'ococcus, Grev. Subord. 6. CRTPTOIVEMIE^ : PkyUopor*, Grev. ; Chondrus, Grev. Subord. 7. CEEAMIEJE : Callithamnion, Lyngb. ; Griffithsia, Agh. ; Ceramiwn, Adans. Subord. 8. POE- Porpliyra, Agh. Structure and Life-history. In spite of the varieties of form presented in this Order, there is so close an essential agreement in their organization that they distinctly appear as members of one natural group, with characters whose value is only equivalent to that of some of the subdivisions of the 448 SYSTEMATIC BOTANY. groups Fucoideae and Confervoideae of Harvey and others, with which they are usually placed parallel. The character of the spores seems to be the same throughout, although the fruits in which they are contained offer several successive degrees of complexity : the favdlce of Ceramiece, and ihefavel- lidia ofCryptonemie.ee, immersed or superficial groups of spores surrounded by a hyaline coat the coccidia of Delesseriece, hollow cases with thick membranous walls, containing a dense tuft of spores arising from a central peduncle and the ceramidia of Pohfsiphonia &c., ovate or urn- shaped cases with thin and membranous walls, having a tuft of spores at the base all these are but slight modifications of one (the conceptacular) kind of fruit, which produces the true spares. The various modes of arrangement of the tetraspores (which appear from Pringsheim's observa- tions to be gonidia, or gemmulary bodies, since they grow up at once into a new thallus, while the other spores do not) the scattered arrangement, the sori or definite groups, and the stichidia or metamorphosed branches enclosing tetraspores, have a like relation ; and an analogous relation runs through the modes of arrangement of the antheridia, which, it may be mentioned, are rarely found in the same individuals of the species as the spores. The antheridia discharge minute spherical corpuscles, to which the best observers deny the power of spontaneous motion, as is the case in regard to the spermatia of Lichens and Fungi ; but they are generally supposed to have a fertiliring function. The simpler forms of thallus occurring in this Order relate it to Ulvece and Confer voidece, while the existence of tetraspores, globular spores, and antheridia in the Dictyotaceae makes that Order form a direct transition to the Fucacese. The mode of fertilization, by means of the antherozoids and the trichogyne, is de- scribed under the head of Reproduction, p. 439. Distribution. The Red Seaweeds are generally diffused, but diminish from warm temperate latitudes both to the equator and the poles. They occur in deeper water than the Olive Seaweeds, and below tide-marks, flourishing best in quiet bays. Qualities and Uses. The abundant gelatinous or horny substance of the thallus of many kinds, composed of a modification of cellulose related to gum and starch, renders them nutritious : Chondrus crispus is the " Carrageen " or Irish Moss ; Rhod.ymenia palmata, Iridcea edulis, and other plants of the Order yield a similar excellent jelly when boiled. Plocaria tenax is largely used by the Chinese for making glue. Some have pungent qualities, as Laurencia pinnatifida, called " Pepper-dulse." Plocaria Helminthochorton, Corsican Moss, has the reputation of being anthelmintic. The Corallinece, including common Corallines (Corallina officinalis) and " Nullipores " (Melobesici) , long supposed to be of animal nature, are very curious on account of their complete interpenetration by carbonate of lime, giving them a brittle and sometimes stony character. DICTYOTACE^B are olive-coloured Seaweeds with a continuous thallus, bearing the reproductive organs in definite groups or lines (sori} upon the surface the spores, tetraspores, and antheridia being all developed in an analogous manner from the cortical layer, bursting through its cuticular pellicle. This small Order is included by Decaisne in the Section Laminariece of the Tribe Aplospor^fe, but has been shown^ by Thuret to be quite distinct from the other Olive-coloured Seaweeds ; it is ALG.E. 449 very interesting as presenting, in a special condition, exactly similar spores, tetraspores, and antheridia to those of the Rhodospermeae, which they thus connect with the Fucaceae, with which they agree in habit and with which they were formerly combined. They belong rather to warmer localities, and are more delicate than the Fucaceae, sometimes, as in Padina, exhibiting attractive colours. They are of no known use. Genera : Dictyota, Lamx. ; Dictyopteris, Lamx. ; Taonia, J. Agh. ; Padina, Adans. FUCACFLE. SEA-WRACKS. Class Algae, Endl. All Algales, Lindl Fig. 611. Diagnosis. (Fig. 511.) Olive-coloured Seaweeds of gelatinous, cartilaginous, or horny texture, with a foliaceous or shrub-like or cord- like thallus, attaching itself to rocks by a simple or lobed and ramified discoid base; fructification in recep- tacles formed out of lobes of the fronds (a), the external surface of which is pierced with orifices leading to chambers (conceptacles, b) lined with filaments intermixed with spore- sacs (e) or filamentous antheridia (c), or both of these ; the olive-coloured spores 4 or 8 in a spore-sac, from which they escape when mature, and are fertilized by the active 2-ciliated corpuscular spermatozoids (d) after they are detached from the parent. Illustrative Genera : Sargassum, Eumph. ; Cystoseira, Agh.; Hdlidrys, Lyngb. ; Himanihalia, Lyngb. ; Pyc- nopkycus, Kiitz. ; Facus, L. Structure and Life-history. Some of the filaments lining the conceptacles be- come, after a time, swollen and filled with brownish matter; this brown matter is de- Organization of Fucacese : A. Halidrys Veloped into 2, 4, or 8 Spores, which escape nttquota, half the nat. size : a, pods or from a small orifice at the apex of the con- ceptacle, through which also subsequently pass the tufts of sterile hairs which do not undergo metamorphosis into spores. Sometimes the antheridia are present in the same conceptacles as the sporanges ;. or they are borne on a separate plant (dioecious). The anthe- ridia consist of ovoid cells, some on branched threads and containing a whitish mass, interspersed throughout which are a number of red granules. The antheridia are ejected through the orifice of the concep- tacle, the cavity of which is lined by (e 8 F ermato - 450 SYSTEMATIC BOTANY. tacle, and themselves give exit to numerous antherozoids, each provided with a couple of extremely fine cilia and containing a red granule. According to our present knowledge the Fucaceae are strikingly separated from the other Olive Seaweeds from the Dictyotaceae by the absence of tetraspores and by the character of their anthei-idia, and*from the Phreo- sporese by the absence of the reproductive zoospores and by other points of organization. They appear to be allied to the Confervoid forms, through Phseosporeae, more closely than to Rhodospermese ; but their reproductive organs are formed on a higher type. Distribution. Universal ; especially found on rocks between tide-marks, or, if growing in deeper water, buoyed up to the surface by vesicular floats ; very large in the Southern Ocean. Qualities and Uses. The gelatinous substance of which the thallus is composed renders some of these plants available as food for man or ani- mals where better productions are scarce ; but their chief value is as a source of iodine, extracted from the " kelp " or ashes, which were for- merly an important source of soda also. The Fuci are also largely used for manure in maritime localities. Saryassum bacciferum forms the celebrated masses of " Gulf-weed " in the Atlantic Ocean. Fncus vesi- culosus, the common Bladder-wrack, grows everywhere on our coast between tide-marks. PH^EOSPOBEJE. OLIVE SEAWEEDS. Class Algse, Endl. All. Algales, Lindl. Diagnosis. Olive-coloured or brown Seaweeds with a foliaceous, shrubby, or branched filamentous thallus ; reproduced by zoospores, having two cilia, one directed forwards, the other backwards, formed in clavate cells or multicellular filaments, collected in more or less definite groups on the cortical layer of the thallus of the larger kinds, in lateral tufts or terminal on the branched filamentous kinds. Illustrative Genera : Chorda, Stackh. ; Laminaria, Lamx. ; Dictyosiphon, Grev. ; Punctaria, Grev. ; Desmarestia, Lamx. ; My- riotrichia, Harv. ; Ectocarpm, Lyngb. ; Myrionema, Grev.. ; Leatliesia, Gray. Structure and Life-history. This group corresponds to the tribe Lami- narieae of tjhe group Aplosporese of Decaisne. The genera included in this Order with highly developed thallus approximate to the Fucaceae, with which they are sometimes associated ; but it has been discovered by Thuret that the so-called " spores " are sacs producing zoospores, which germinate and produce new plants like those of Confervoids ; they are distinguished, however, from the zoospores of that group by the arrangement of the cilia, which are here two in number, unequal in size, and take reverse directions as they leave the body of the zoospore, resembling, in fact, the form exhibited in the spermatozoids of Fucus. The size and number of the zoospores are not constantly the same in the same plant ; and in dif- ferent cases the organs producing the zoospores are large clavate sacs or chambered filaments, the number of zoospores in a cell being either de- ALGJE. 451 finite or indefinitely great, on account of more advanced segmentation of the contents. The mode of reproduction and the forms of the thallus in such genera as JSctocarpus &c. bring this Order very near to the Con- fervoidese. Much obscurity still prevails here, since antheridia coexist with reproduction by zoospores in Cutleria, and appear to exist in Spha- celaria and Cladostephus, which also reproduce by zoospores. Distribution, Qualities, &c. Much the same as in Fucaceae. Laminaria digitaia and saccharina are eaten (under the name of Tangle) on the coasts of the north of Europe, as also is Alaria esculenta. CONFERVOIDE^. SILK-WEEDS. Class Algge, Endl. All Algales, Lindl. Diagnosis. (Fig. 512.) Plants with a filamentous, membranous, gelatinous, or pulverulent thallus, growing in fresh or salt water, or on moist substances, of a bright green or, more rarely (often Fig. 512. Organization of Confervoid Algae : A. Filaments of Spirogyraquinina: a, in natural condition ( magnified 50 diameters) ; 6, two filaments conjugating ; c, a spore formed in one cell from the mixed contents ; d, a free spore ; e, the same germinating. B. Protococcus viridis (magn. 200 diameters): a, a group of cells cohering by jelly-like matter; b, four cells formed by division of a cell of a, and two zoospores escaped from one of the cells, sub- sequently settling down as resting-cells, c. C. Cladophora fflomerata : a, filaments, of natural size ; 6, the top of a branched filament, magnified; c, cells about to form zoo- spores ; d, the same, with the zoospores escaping from the uppermost cell ; e, zoospores germinating into new filaments. 452 SYSTEMATIC BOTANY. temporarily), red colour, -reproduced by zoospores discharged from the ordinary cells of the thallus (A, d\ or by spores formed in these cells after impregnation by combination of the contents of two cells, either by conjugation (C, e), or by the transference of spermatozoids into the parent cell of the spore, the spores (C, d} passing through a stage of rest before germination. Illustrative Genera : Codium, Stackh. ; Bryopsis, Lamx. ; Vaucheria, DC. ; Botrydium, Wallr. ; Drapamaldia, Bory ; (Edoyonmm, Link ; Spirogyra, Link ; Sphccroplea, Agh. ; Coleochcete, Breb. ; Hydro- dictyon, Roth. ; Ulva, Agh. ; Tetraspora, Dec. ; Nostoc, Yauch. ; Botrydina, Breb. ; Clathrocystis, Henf . ; Palmetta, Agh. ; (Achlya, Nees) ; (Chytridium, Al. Br.). Structure and Life-history. The specialities of the very multiform group represented by the above list of genera can scarcely be dealt with in a work like the present ; and, in fact, our knowledge of the essential characters of the plants is at the present time undergoing a thoroup-h revision. In the definition of the group of Confervoids here, the Oscillatoriaceae and the other permanently active forms are excluded. The Oscillatoriaceae are organized in a very different way from the true Confervoids. The Confervoids proper are mostly very simple cellular organisms, with chlo- rophyll and starch in the cells while they are actively vegetating ; the majority discharge the cell-contents in the shape of one or many active zoospores, with 2 or more cilia at a beak-like extremity ( Vaucheria, fig. 506, p. 442), or with cilia all over the surface ; besides which process, sexual reproduction has been observed in Zyynema by conjugation, in (Edogo- nium, Sph&roplea, Vaucheria, Bulboclicete, &c. by spermatozoids derived from one cell entering the cavity of the parent cell of the spore ; and in all probability this will be found general. The mode of fertilization will be found described at p. 441. The spores formed after fertilization become encysted in a firm coat, thrown off in germination, which commonly ensues only after a long interval. The Palmellece are forms not yet well explained, composed of solitary cells imbedded in a common mucus ; they appear to stand at the lowest point of organization in the Vegetable Kingdom, if they be not stages of growth of higher forms (fig. 504, p. 437). The genera above grouped by Professor Henfrey under the head of Confervoidese are more naturally grouped by Decaisne under several distinct sections of varying degrees of importance as follows : 1. Conferva, comprising plants consisting of tubes or cells containing ovoid spores provided with 2-4 vibratile cilia. 2. Unicellular es. Plants consisting of a single cell producing numerous ciliated spores, which in Botrydium unite by conjugation (fig. 503, E). 3. CEdoyomecs. Filamentous Algae, producing spores either by the ag- gregation of the green colouring-matter of the cell into a spheroidal mass, w r hich escapes from the parent cell by a special aperture in its wall, and is then seen to be provided with a crown of vibratile cilia, or as the result of sexual agency. The antheridia consist of filaments, each cell of which contains 1 or 2 spermatozoids, w r hich escape by the lifting of a lid -like valve of the cell- wall and fertilize the spore as above stated (see p. 441 ALG.E. 453 4. VaucheriecB. Unicellular Algae, producing two Hods of reproductive organs the one resulting from the concentration of the green matter at the extremity of the filaments into an oval active spore covered with cilia, the other formed as a result of sexual agency. The antheridia appear in Fig. 513. Fig. 514. Fig. 513. Protococcus viridis, Henfr. : a, group of cells, the upper with eight in a linear series, those to the left dividing; 6, zoospores set free by the solution of the cell -wall; c, cell dividing into two zoospores ; d, resting- cells ; e, zoospore with the cilia cast off; f, zoospore. Fig. 514. Palmella nivalis. the form of small horns placed in the proximity of ovoid sporangia. These antheridia contain numerous extremely minute spermatozoids, which es- caping fertilize the sporangium and determine the formation of a spore, which does not germinate immediately, but only after the lapse of some time (p. 442, fig. 506). 5. Synsporece or Conjugates. Filamentous or unicellular Algae, repro- duced by the process ot conj ugation. This group comprises the Desinidieae, of which further notice will be found hereafter. 6. Diatomacece. These are also alluded to in the following pages. Distribution, Qualities, &c. Met with universally in fresh and brackish. water, some genera also on sea-coasts, growing on rocks, large Algae, &c. Some of them occasionally appear suddenly in vast quantity, colouring- lakes green ; or, as in the case of Palmella nivalis (fig. 514), giving rise to the phenomenon called u Red Snow." Palmella cruenta (fig. 504) often forms large patches of substance like half-coagulated blood on damp stones and rocks. The green slimy matter of stagnant pools is mostly composed of interwoven masses of filamentous Confervoids, which present most beautiful and varied forms under the microscope. Ulva (marine) produces large membranous fronds, which are sometimes eaten under the name or Green Laver. OSCILLATORIACE^ (fig. 503, A). Microscopic filamentous structures, usually collected into patches of definite or indefinite form, extending by peripheral growth, composed of continuous tubular sheaths enclosing a green or brown gelatinous matter marked by transverse striae, where the substance is divided into longer or shorter pieces, often escaping from the 454 SYSTEMATIC BOTANY. tube, ultimately resolved into discoid fragments, which, when free, be- come globular. The gelatinous " core," the vital part of the structure, is capable of a peculiar movement, which causes the free portions or ex- tremities of the filaments to vibrate like a pendulum, or with a slightly vermiform oscillation, whence the name of the Order. Reproduction by spores unknown. Our knowledge of the essential characters of this Order is imperfect ; and the only mode of reproduction known is by simple division of the central substance of the filaments, the portions slitting out of the ends of the sheaths and secreting a new coat of their own. Their peculiar oscillating motion is one of the marvels of Vegetable Physiology ; they appear to be totally destitute of cilia. Their movements, and the nature of their central substance (apparently devoid of starch, and coloured by different matters besides chlorophyll), seem to indicate a relation between Oscillatoriacese and Diatomaceaa, which would connect the latter with Confervoids. They occur in water, fresh and salt, and on damp earth everywhere. Genera : Oscillator ia, Bosc ; Microcoleiis, Desmaz. j Calo- thrix, Agh. ; Rivularia, Roth. DIATOMACE^E. Class Algae, Endl. All Algales, Lindl Diagnosis. (Fig. 503, B, C, page 436.) Microscopic unicellular plants, occurring isolated or in groups of definite form, usually surrounded by a gelatinous investment, the cells exhibiting more or less regular geometrical outlines, and enclosed by a membrane striated or granular, either simply tough and continuous, or im- pregnated with silex and separable into valves. Reproduction by spores formed after conjugation of the cells (cT), by zoospores formed from the cell- contents, and by division. ILLUSTRATIVE SUBORDERS. Subord. 1. DESMIDIE^] (fig. 503, B). Cell-membrane without silica, con- taining chlorophyll and starch. Closterium, Nitzsch; Oosmarium, Menegh. ; Euastrum, JShr. ; Pediastrum, Meyen ; Desmidium, Agh. Subord. 2. PIATOME.E (fig. 503, C). Cell-membrane impregnated with silex, valmdar, containing a brown colour ing -matter. Eunotia, Ehr. ; Diatoma, DC. ; Navicula, Sory, Isthinia, Agh. ; Melosira, Agh. Affinities, &c. These organisms were formerly included among Infu- sorial Animalcules j but the vegetable character is very strongly marked in Desmidieae ; and the reproduction by conjugation, characteristic of certain tribes of Confervoids, occurs not only in Desmidiece, but in Dia- tomece, which in respect to general organization cannot well be separated from the Desmidiece, although the nature of the cell-contents has more of the character of what we are accustomed to regard as animal substance The Diatomece are also remarkable for the way in which they divide by segmentation into a number of distinct frustules, each of which grows into a perfect plant. FUNGI. 455 Distribution. Desmidiece occur in all quiet pools of pure water, at the bottom or adhering to other plants. Diatomece are universally dif- fused, not only in fresh water, but in the sea and on moist ground, in all of which situations their siliceous cell- walls cause their remains to accu- mulate, if left undisturbed, until they form actual mineral strata. VOLVOCINE^E are microscopic bodies swimming in fresh water by the aid of cilia arranged in pairs upon the surface of a common semigelatinous envelope, the pairs of cilia each belonging to a green corpuscle resembling the zoospore of a Confervoid, imbedded in the periphery of the common envelope. .Reproduction by the development of each corpuscle into a new colony, the whole being set free by the solution of the parent envelope, or by conversion of the corpuscles into encysted resting-spores like those of (Jonfervoids. These curious and beautiful objects, found in similar situations with the Confervoids, appear more closely related to that group of organic beings than to any form distinctly recognizable as mem- bers of the Animal Kingdom, the persistence of the power of motion throughout the period of vegetative life being the only animal (?) character. Genera : Votvox, Lam. ; Pandorina, Ehreub. (tig. 508, Dj j Stephano- , Cohn ; (fonium, Lam. Division II. Fungi. Cryptogamous plants consisting of long thread-like, tubular, gene- rally branching hyphse, or of branching series of cells interwoven into a mass which is in some cases microscopic in dimensions and in others of great extent, nourished on organic substances as para- sites or as saprophytes, and entirely destitute of chlorophyll or similar pigments. .Reproduction effected by both sexual and asexual means. PHYCOMTCETES. Diagnosis. Fungi consisting of a mycelium of long, densely ramifying tubes, and bearing both sexual and asexual organs of reproduction. The asexual organs of reproduction (zoosporanyia, coiiidia, and sporangia) are functionally of equal value with those produced by sexual agency (oospores and zygospores) that is, the oospores or zygospores (as the case may be) produce either zoospo- raiigia or conidia or sporangia, and on the same plant, but a little later, either oospores or zygospores again ; the nrst or asexual class of these also reproduce both themselves and the second or sexual class a little later. This Order may be divided into three Suborders, in which the habits of life and growth vary. Suborder 1. SAPROLEGNIE^E. Fungi growing for the most part in water, and chiefly on the dead bodies of insects, and consisting 456 SYSTEMATIC BOTANY. of a mycelium of long, densely interwoven hyphoe, which bears both sexual organs antheridia (male organs) and ooyonia (female organs) and asexual zoosporangia. The contents of the oogonia, when fertilized by the antheridia, are called oospores, and on germinating produce a mycelium which bears first zoosporangia and later the sexual organs. The zoosporangia on bursting produce zoospores which, after a short motile state, come to rest, germinate, and form a mycelium which produces again zoosporangia, and later the sexual organs. The zoospore, therefore, which has an asexual origin is, functionally, of equal value with the sexually produced oospore. Oospores Zoosporangia Oospores Zoosporangia, Oospores. Zoosporangia, Oospores. ILLUSTRATIVE GENERA : Pythium, Nees j Saprolegnia, Nees ; Aphano- myces, De Bary ; Achlya, Nees. Structure and Life-history. In the forms which Pringsheim calls mon- oecious the antheridia and oogonia are produced beside each other on the same plant ; hut in the others, first antheridia and then oogonia. The oogonia are usually situated at the end of short branches of the mycelial hyphae, and are very rarely interstitial. In the monoecious forms they are globular cells, rich in protoplasm, which is at first equally distributed. In Saprolegnia monoica the cell-membrane is resorbed at numerous places, and has a perforated appearance. At the same time the protoplasm gra- dually separates into several portions, which become rounded off and float together in a watery fluid within the oogonium, each bounded by a smooth superficies which does not consist of cellulose. In Pythium t Aphanomyces, and several species of Saprolegnia the whole of the proto- plasm within the oogonium contracts into one of these globes, which, floating in the watery fluid, takes up its position in the middle of the oogonium. During the formation of the oogonium, the antheridia or antheridium, as the case may be, grow out from the same branch of the mycelium or from neighbouring hyphae in the form of thin, cylindrical crooked twigs, often wound round the stalk of the oogonium. The upper ends adhere to the wall of the oogonium, swell slightly, and become bounded at the base by a septum. At the time of the formation of the globular bodies within the oogonium, each antheridium pushes through the wall one or more tubes, which open at the points and discharge their contents. These contents are minute motile corpuscles, scarcely j^ ff millim. in size, and are the fertilizing spermatozoids. The globular bodies after being fertilized are provided with a cellulose membrane, and receive the name of oospores. In the dioecious forms (e. g. Saprolegnia dioica and Achtya dioicd) the oogonia and their globular contents are formed as in the monoecious species. The antheridia, on the other hand, are formed in thick bladder-like protuberances which arise at fixed times on the mycelium, and are divided 457 by transverse walls into a series of cylindrical cells, each of which repre- sents an antheridiuin. In baprolegma dioica the whole of the protoplasm, of the antheridium separates into numerous minute spermatozoids, which are discharged in a motile state from an opening in a narrow protuberance of the wall of the antheridium. In Ac/ilya dioica the contents of the cylindrical antheridium are divided into a number of portions (of about the size of the zoospores of the species). These in their turn break up into small spermatozoids, which emerge first from their special mother cells and then from the antheridium, in the same way as in Saprolegnia dioica. The spermatozoids of both species move by means of a long ciliurn. It is to be assumed, from the analogy of closely related Algce, that the spermato- zoids enter through the holes in the walls of the oogonia and fertilize the globular bodies by union with them; but there is not enough direct evi- dence to warrant more than an assumption. The ripe oospores of Sap'oleynia (so far as they are yet known) possess a membrane consisting of two coats, and produce germ-tubes after a period of rest. They have also been known, but exceptionally, to produce zoo- spores after a short period of rest. Suborder 2. PERONOSPOREJE. Fungi parasitic on living Phane- rogams, and consisting of a mycelium of densely ramifying hyphae, which bears both sexual organs autheridia (male organs) and oogonia (female organs) and asexual conidia. They resemble strongly the preceding family, SSaproley niece. The mycelium which rauiihes within the host-plant nrst bears the conidia either singly on branching tree-like (Peronovpora), or in a vertical series on club- shaped (Cy stop us) conidiophores, which appear upon the surface of the affected part of the host-plant. According to the species the conidia are either simple spores, which reproduce the mycelium by emitting germ- tubes directly, or zoosporaugia (as in certain species of Perouospora, Phytophthora infestans, and Cystopus}, the germi- nating zoospores of which give rise to a new mycelium. This new mycelium in both cases produces conidia again, and later the sexual organs. The germinating oospores also produce a mycelium, which bears both conidia and, afterwards, the sexual organs. The asexu- ally-produced conidia here (like the zoosporangia in the Saproley- niece) are functionally of equal value with the sexually-produced oospores. Oospores Conidia Oospores Conidia, Oospores. Conidia, Oospores. ILLUSTRATIVE GENERA : Peronospora, Cord. ; Phytophthora, De Bary ; Cystoptts, Lev. Structure and Life-history. The reproduction of the Peronosporce so strongly resembles that of the monoecious forms of tlie Saproleynie<* that 458 SYSTEMATIC BOTANY. a comparative description only will be necessary. The oogonia arise at the end of short branches of the mycelium in the intercellular spaces of living Phanerogams, and resemble those of the monoecious Saproiegniea both in form and in being rarely interstitially situated on the mycelium. The antheridium grows either on the same branch or a neighbouring one, and is also similar in form to those of the monoecious forms of the pre- ceding Order. The process of fertilization is carried out as in it too, only that the protoplasm within the oogonium constantly contracts into one globular mass. Professor de Bary records that he never found developed oogonia without an antheridium, and extremely seldom such as had two. The oospores germinate after a long period of rest, usually lasting through- out the winter. Two forms of germination have been observed. In Cystopus cand'idus the oospores burst and produce the same number of zoospores as the asexual conidia (zoosporangia). In Peronospora Vale.- rianeilce the oospores produce each a germ-tube which, by repeated rami- fication, forms a new mycelium. The conidia also, as already stated, either produce germ-tubes or zoospores according to the species. The mycelium of Cystopus is provided with numerous organs called haustoria, which, in the shape of small bladders, penetrate the cell-walls of the host- plant and extract the nourishment for the use of the fungus. The well-known potato-disease is caused by a fungus belonging to this family. It was, until lately, known as Peronospora infestans ; but, in a recent work on the subject, Prof, de Bary considered it to have separate generic characters, and it now bears the name of Phytopkthora infestans. Suborder 3. MTJCOBINI (fig. 1 D, p. 8). Fungi growing on organic solutions, and consisting of a densely branching mycelium, with no transverse septa up to the time of fructification, and bearing both sexual organs and asexual sporangia. The result of the union of the conjugating sexual bodies is called a zyyospore. The asexual spo- rangia are here (like the similar organs in the two preceding orders) functionally of equal value with the sexually produced zygospores. Zygospore Sporangia Zygospores Sporangia, Zygospores. Sporangia, Zygospores. ILLUSTRATIVE GENERA : Mucor, Mich, j Syzygites, Ehrb. j Rkizopus, Ehrb. j Pilobolus, Tod. Structure and Life-history. The sporangia are similar in function and in some degree in structure to the zoosporangia and conidia of the Sapro- leynieae and Peronosporece. They appear at the end of sporangia- bearers, which, up to the time of fructification, are, like the mycelium, without septa. The spores contained by the sporangia germinate by means of germ-tubes and form a mycelium by repeated ramification. This was for long the only form of reproduction known in the Mucorini, and it is only in recent times that the researches of Professor de Bary and others have FUJS T GI. 459 brought to light another and a sexual means of reproduction, which is described in tne cases of llhizopus nigricans, Ehrb., and Syzygites megalo- carpus, Ehrb. These cases are, with the exception of unimportant details, similar, and it will be sufficient to describe the process as it occurs in the former. The conjugating cells of Ithizopus nigricans are elongated, stout, irregularly brancning and interwoven tubes. Where two meet each pusnes against the other a protuberance, at tirst cylindrical and of equal thickness with itself. They remain closely attached and soon grow to a considerable size, in thickness chiefly. At the end of each a separate cell is formed by the growth of a partition. These two cells are usually of unequal size one as long as it is broad, and the other only half as long as its breadth. The original membrane which separated them now be- comes perforated in the middle, and soon vanishes altogether; the two conjugating cells then unite and form a zygospore, which increases rapidly in size, and usually attains a diameter ol over one fifth millini. It is, as a rule, drum-shaped ; the ends smooth, and the free surface clothed with wart-like protuberances. The contents are of coarsely granular proto- plasm, often accompanied by large drops of oil. The germination of the /ygospore, as observed in Syzygites, is by means of a germ-tube, which by repeated dichotonaous branching, at the expense of the stored-up matter in the zygospore, soon forms a new mycelium bearing asexual sporangia. .Professor Strasburger has very recently proposed the name of gametes fur the conjugating cells, and zygote for the zygospore. Professor de J3ary has further suggested that when the gametes are stationary, as in this Order, they should be called aplanogametes, to distinguish them from motile conjugating bodies found in Algce, which he would call plano- yametes. The substitution of zygote for zygospore is on the ground that the organ in question is not the equivalent of a spore, but of a fertilized ovum. This nomenclature, if accepted (and it is time that some such rational system were introduced), will necessitate the substitution of other words for the terms oospore, &c., in other Orders. The Mucorini are usually to be found growing on horse-dung and de- caying substances. HYPODEEMII. Diagnosis. Fungi parasitic on living plants, and consisting of a mycelium of interwoven hyphse bearing asexual organs of repro- duction (spores) either in definite or irregular receptacles. This Order is divided into two Suborders as follows : Suborder 1. UBEDI]OLE. Fungi parasitic on living plants, and consisting of hyphse woven into dehnite fructiferous receptacula, at tirst situated beneath the surface of the affected part, but at length bursting out. The reproductive organs are of an asexual character, no sexual organs being as yet known, and take three consecutive forms, arranged so as to form a cycle of generations on two different host-plants. 460 SYSTEMATIC BOTANY. Teleutospores. ^Ecidium-spores accompanied by sperrnogonia. Uredospores, and later on the same mycelium teleutospores again. ILLUSTRATIVE GENERA : Puccinia, Lk. ; jEridium, Lk. ; Uromyces, Lev. Structure and Life-history. The life-cycle of these parasites begins with the germination of the teleutospores thick-walled spores situated at the end of filiform basidia, either singly or in pairs, according to the genus to which they belong. The germination takes place in spring, and consists in the emission of a germ-tube, which rapidly forms a promycelium bearing three or four sporidia. These sporidia also soon push out germ- tubes, which, if on a suitable host-plant, penetrate the epidermis-cells and form a myce- lium within the parenchyme. After a few days this mycelium begins to form a new fructification under the epidermis of the host-plant, which even- tually breaks out under the forms of the ^Ecidia and their constant com- panions the spermogonia. The latter appear first. Round them, or irregularly among them, are the ^Ecidia. The spermogonia are in shape small narrow-necked sacs of the same colour as the ^Ecidia. They were formerly believed to be different species of Fungi from the ^Ecidia, but Tulasne has shown that they belong to the same. In them are found minute bodies, called snermatia, which Tulasne believed to be male organs (spermatozoids), since he found them incapable of germination ; but no female organs have as yet been found. It was also suggested that they stood in a sexual relation to the ./Ecidia, near which they are con- stantly found ; but Professor de Bary has cultivated true ^Ecidia, the spores of which germinated, on a plant on which was found no trace of spermogonia or spermatia. The subject is at present wrapt in mystery. The ^Ecidia consist of at first round or oval, and after bursting* basin- shaped receptacula, the walls of which are composed of pseudo-paren- chyme (short, polyhedral, closely fitting mycelium-cells). At the base of this body is the hymenium a circular layer of short, cylindrical, club- shaped upright basidia, on each of which rests a series of spores in regular order, one above the other. The spores are of a round polyhedral form, and filled with protoplasm coloured red or yellow by oil. On the burst- ing of the enclosing peridium of pseudo-parenchyme the spores are libe- rated in a state capable of germination, which takes place in the form of short crooked germ-tubes that penetrate through the stomata of the next host-plant, and form rapidly a new mycelium in the intercellular spaces. Again, after a few days, this mycelium forms a new fructification the Uredo. The Uredo is at first of "the shape of a flat circular cushion lying immediately under the epidermis of the affected part. On it arise filiform basidia, each of which bears a round or oval spore the Uredospores, which during their formation break through the epidermis. The Uredospores germinate rapidly and reproduce themselves constantly, and to this quality is the rapid and extensive spreading of this disease to be attributed. The same mycelium which begets the Uredo, afterwards forms the teleuto- spores from which we started. The teleutospores hibernate and germinate again in spring, as we have seen, and so every year the disease passes through the same cycle of generations. FUNGI. 461 The host-plants affected by the same species are usually of two very different kinds. The teleutospores and Uredospores afiect chiefly the Graminece., and prove very destructive to that useful order of plants. The ^Ecidium spores are not so much confined to one order of plants, but affect usually the Composites, Ranunculacea, Leguminosce, and Labiatce, to which they are by no means so destructive as the teleutospores and uredosporea are to the Graminece. Until recently the different generations of these Fungi were taken to represent different genera, and even now they are, we need not say erro- neously, so described by many mycologists on the plea of convenience. The ^Ecidiumspores represent the genus u jSZcicKttm" the Uredospores " Uredo" and the teleutospures " Puccinia" and " T7romyces." Each generation of each species has its peculiar host-plant, and of a not incon- siderable number there is only known one or two generations the JEd- dium only in some cases, and the Uredo and Puccinia only in others. To M. Tulasne and Professor de Bary belong chiefly the honour of having worked out this remarkable life-history. Suborder 2. USTILAGUSTE^. Fungi parasitic on living plants, and consisting of interwoven hyphae, which bear asexual spores irregularly. Spores sooty-coloured, either solitary, in series, or in masses, at first enclosed, but at length bursting out and escaping easily, from the slender nature of the threads which bear them. The whole life-cycle, so far as yet known, consists in the forma- tion by the germinating spores of sporidia, which, on suitable host- plants, germinate and form a mycelium on which the spores are again directly formed. Illustrative Genera : Ustilago, FT. ; Til- letia, Tul. Structure and Life-history. The habit of life of this order is similar to that of the preceding one. In it the life-history, so far as it goes, is also of the same nature. When the spores, which correspond to the teleuto- spores of Uredinea, germinate, a promycelium is formed as in that Order, bearing sporidia, in some cases sessile and in others slightly stalked. It appears also that successive sporidia may be formed at the same place. These sporidia germinate in the usual manner and form a new mycelium in the tissues of a suitable host-plant, which mycelium directly produces again the spores from which we started. The Ustilaginece are very in- jurious, especially to the Graminece. Kuhn and Hoffmann observed that the sporidia attack the axis of the germinating plants, in which they de- velop a mycelium, which is carried up with the growing plant, and ultimately produces spores in the fruits and causes their destruction. The power of producing successive sporidia tends largely to cause the plentiful distribution of the Order. BASIDIOMYCETES. Diagnosis. Fungi growing on dead organic matter and stumps of trees, and consisting of hyphse interwoven, so as to form a fleshy, gelatinous or woody thallus (vulgarly considered the plant), but 462 SYSTEMATIC BOTAXY. which is the receptacle of the hymenium. Hymenium bearing usually quaternately asexual spores at the apex of erect basidia. Spores reproducing the plant directly without the intervention of any intermediate generation. Mycelium comparatively small and floccose. The Order may be divided into the following Sub- orders : Suborder 1. TREMELLHSTI. Fungi growing on stumps of trees and on the ground, of a gelatinous consistency, with sometimes a denser nucleus, immarginate or cup-shaped. Hymenium bearing two distinct kinds of basidia in different genera. Spores reniform, in some cases divided, and in others not. Illustrative Genera: Tremella, Dill. ; Dacrymyces, Nees. Structure and Life-history. In the genus Tremella the basidia are at first subglobose or quite spherical, and divided from top to bottom into four equal parts. These segments either remain united or become divergent from each other, while they grow out to the margin of the fungus in the form of long- hyphse, and produce there generally undivided and kidney-shaped spores. In Dacrymyces and Guepinia the basidia are at first claviform, but subsequently grow out in the form of two thick diverging arms, on each of which is produced one reniform spore. There are usually present in these plants in great abundance very mi- nute spherical or ovoid spermatia, produced in regular sperm at ophorous apparatus. Their function is unknown. The ordinary spores reproduce the plant directly. The consistence of these plants is very gelatinous and collapses on drying. If, however, they be placed in water, they very soon absorb it, and become again distended to their former extent ; and this pro- perty is found to be of great use in examining old specimens. Suborder 2. HYMEISTOMYCETES. Mycelium floccose, giving rise to a superficial hymenium on which are produced clavate basidia bearing at the apex usually quaternately, slightly stalked or sessile spores. The substance of the plants varies from gelatinous to woody. Illustrative Genera : Agaricus, L. ; Boletus, Fr. ; Poly- porus, Fr. ; Hydnum, L. ; Corticium, Er. ; Clavaria, L. Structure and Life-history. This group is the best known of all the Fungi, and includes the common Mushroom, to which all its members bear more or less resemblance in organization and reproduction. The common form is that of a pileus raised upon a stalk or stem, and bearing on the under surface lamellae or gills (Agaricini),ipQTes (Polyporei), or teeth (Hyd- nacei), on the surfaces of which are situated the basidia, which bear the spores (fig. 515). The spores are the only reproductive organs and, so far as is yet known, are asexual in their .origin. On germinating, they give rise directly to a new mycelium, which bears again the spore-producing plant. Attempts have been made at different times to discover the exist- ence of a sexual agency in the production of these spores, but as yet un- successfully. Among the basidia are seen other cells of similar shape and usually larger size, called cystidia; and it was at one time contended that they were male organs but no special function seems to belong to them. They are probably only barren basidia. The mycelium is entirely, or FUNGI. 463 nparly so, underground, and that part which is commonly called the fungus is the receptacle. The Agaridni are distinguished from the other Hymenomycetes by the hvmenium being always interior, and spread over the surface of gills which radiate from the stem. The gills may be either simple or branched, and attached to or distinct Fig. 515. The Mushroom (Agarious campestris) : A. Fruit, showing the expansion from the volva, and the veil tearing away and leaving the annulua. B. flection of " gills," magnified 50 diameters. C. Basidia and spores from ditto, magn. 400 diam. or from the stem. The spores vary in colour ; but one colour is constant as a rule to a genus, unless in the case of the large genus Agaricus, where the colour of the spores is used as the basis in forming groups of the different subgenera. The stem is sometimes cartilagi- nous, and sometimes fleshy, and also varies in colour, but according to the species and even to its age. There is to be found on the stem in some genera and subgenera a ring or annulus, which is all that remains of a veil or covering (velum partiale) which united that part of the stem with the outer edge of the cap or pileus, but was ruptured on the expansion of the latter. In certain subgenera of Agaricus (e. g. Volvaria, Amanitd) the whole fungus is enclosed at first in a volva (velum universal*), which on bursting falls away and is independent of the cuticle on the upper suiv face of the pileus, but remains attached to the base of the stem. Some- times, as in Amanita, both forms of veil are found together. The s+em. is not always central, but is also found to be eccentric and even lateral, as in Pleurotus, in which it is usually very much suppressed. There are more esculent species of Agaridni than of any other group of Fungi. The species are usually terrestrial in habit. In the Polyporei the hymenium is spread over the cavity of tubes or pores, and is in some cases inferior and in others superior. The texture of the plants is, as a rule, more cartilaginous and woody than that of the Agaridni. The genus Boletus has the habit of an Agaric, and usually its central stem and texture. The hymenium is distinct from the hymeno- phore, from which the tubes are easily separated. The genus Polyporm is, on the other hand, different from the Agaridni in habit the stem when present being usually lateral, and the texture of the whole often very woody. The hymenophore is not easily separated from the pores. In the resupinate forms the pores open upwards, and the habit of the fungus is crust-like. The species of this genus grow, as a rule, on stumps of trees and other woody substances. The hymenium of the Hydnacei is inferior or amphigeous, and spread over teeth or spines, which are soft, usually of the shape of an awl, and distinct at the base. Some of the species are in the form of a stalked pileus with the teeth on the under surface, while others resemble the 464 SYSTEMATIC BOTANY. resupinate forms of Polyporei. Several of the species are fleshy and edible, but others are of a corky texture. In the Auricularini the hymeuium is confluent with the hvmenophore, which is even and very rarely veined. The habit is generally the same as in the Pofyoorei. The hymenium of the Clavarinei is scarcely distinct from the hymeno- phore, and is amphigeous, and reaches to the apex of the plant, which is sometimes club-shaped, and sometimes in the form of spines usually growing together at the base. The surface is at first smooth, but becomes wrinkled afterwards. The plants are never incrusting nor leathery, but are usually at first gelatinous and afterwards horny. It is said that several species are esculent. Suborder 3. GASTEEOMYCETES. Fungi forming roundish angio- carpous receptacles consisting of an outer layer or peridium enclosing masses of tissue on which are borne the bvmenia. The spores are borne at the points of basiclia, one basidium often producing as many as eight spores. The spores are liberated either by the simple bursting of the peridium, or by the development of particular masses of tissue. Illustrative Genera : Phallus, L. ; Ly coper don, Tournef. ; Hymenogaster Vitt. ; Nidularia, Fr. Structure and Life-history. In Phallus the peri di urn resembles the universal volva of some Agarics in the wav in which it envelopes the internal part of the receptacle, and also in its manner of bursting. Within the volva is a gelatinous stratum, and within that again the hymenium, which is very deliquescent and covered by an inner peridium. On the bursting of the peridium (or volva) the hymenium is elevated in a sort of pileus by a stalk, as in the volvate Atjaricini. In Clathrus, an allied genus, the receptacle forms a globose network. In Batarrea there is also present a universal volva, and the hvmenium is similarly elevated ; but in Lycoperdon, Hymennyaster, Nidularia, &c., the bursting of the peridium sets free the spores without any such elevation, the hymeninm remaining in the interior. The spores reproduce the mycelium, on which the same plant prows ajniin without any intermediate stage as far as is known. The Puff-balls (Lycoperdori) and Stink-horns (Phallus) are typical of this Order. ASCOMYCETES. Diagnosis. Fungi growing chiefly on the dead parts or remains of plants, more rarely on living plants or organic solutions. The spores of this Order are formed in asci by free cell-formation, and are distinguished by the name of ascnspores. From the germi- nating ascospore there proceeds a mycelium consisting of denselv branching hyphae, which develops either within the host or spreads on its surface, and is sometimes short-lived, and sometimes per- sists for years. In most cases it is in a position to produce asexual reproductive organs co-nidia, stylospores, and xpermatia. The conidia are borne on conidiophores or special branches of the FUNGI. 465 mycelium, and the stylospores and spermatia are formed in special conceptacles (pycnidia and spermogonia respectively). The myce- liuin is extensively reproduced by these asexual organs, and in many species they are the only reproductive organs known. In all cases, however, in which the com'plete life-history has been followed the same mycelium has been found ultimately to produce sexual organs, and, as a result of the .fertilization of these, a fructification, in the asci of which are formed the ascospores. This completes the cycle of generations. This group is divided into the following Suborders : Suborder 1. DISCOMTCETES. Fungi living on dead organic bodies, and forming on the branches of the mycelium sexual organs the carpogonium (female) and the pollinodium (male). From the fertilized carpogonium, or, as it is then called, ascogonium, there arise the asci in which the ascospores are formed. The ascospores germinate and reproduce the mycelium. The hymenium is super- ficial, and on it are always the asci, and usually paraphyses, con- sidered by some authors to be abortive asci. Illustrative Genera : Helvella, L. ; Morchella^ Dill. ; Peziza, Dill. ; Dermatia, Fr. ; Pa- tellaria, Fr. ; Phacidium, Fr. ; Stictis, Pers. Structure and Life-history. The life-history of Ascobolns, as detailed by Janczewsky, is typical as regards Discomycetes generally. In it the pollinodium aud the carpogonium consist each of a series of short crooked cells arising on neighbouring branches of the mycelium. The thin crooked cells of the pollinodium embrace the more remote end of the sausage-shaped carpogonium, and in this way the fertilization takes place. In consequence of fertilization, one of the cells in the middle of the carpo- gonium grows larger than the others, and becomes globular in shape ; it is distinguished by the name of ascogouiuui. The ascogonium then sends out numerous hyphae on which are borne the flask-shaped asci, and in them the ascospores, 8 in number. The hyphse of the mycelium on which the sexual organs are borne produce by repeated cell-division a dense mass of pseudo-parenchyme, which surrounds the carpogonium and forms the sterile part of the fructification. The paraphyses which are borne on the same hyphse with the asci are situated between the latter, and may serve, according to Boudier, to assist in some way the dehiscence of the asci ; they are generally regarded, however, as abortive asci. The whole fructification is cup-shaped. The sexuality was first discovered in the Ascomycetes by Professor de Bary in the case of Peziza conftuens. The process of fertilization, &c., though differing in this case from that described above as occurring in Ascobolus, agrees in all essential details with it. There are certain species of Peziza the mycelium of which forms conidia, and the unripe fruit is represented by a resting sclerotium. This has been observed by Prof, de Bary in Peziza Fuckeliana. In it the conidia are formed on the mycelium prior to the sclerotia, and reproduce the my- celium extensively. No sexual process has been observed in connexion 466 SYSTEMATIC BOTAKT. with the formation of the sclerotia, which consist of a dense mass ot hyphse enclosed by a black rind. If the sclerotia germinate shortly after their formation, the result is a mycelium which bears conidia again ; but if germination is delayed for a month or two, a basin-shaped hymeniuiu is formed, on which asci containing ascospores arise. This form of fructi- fication is that commonly known as Peziza Fuckeliana. The spermatia borne in the spermogonia have, until lately, been believed to be incapable of germination ; but M. Cornu states that he has caused them to germinate and produce a mycelium like the conidia. In Peziza and the allied genera the whole fructification is basin-shaped, with the hymenium on the inner surface of the basin ; but in other cases, e. g. Morchella, Helvetia, Spathularia, Geoglossum, &c., it takes the form of clubs or stalked caps of considerable size with the hymenium on the outer surface. Our present knowledge of the processes of fertilization, &c., in the Discomycetes is the result of the labours chiefly of Tulasne, De Bary, and Janczewsky. The species of Morchella and Helvetia are, as a rule, esculent, but none of the other forms of Discomycetes have attained any reputation for this quality. The genus Gymnoascus is an assemblage of small and very simple Ascomycetous Fungi growing on dung. Its mycelium begets numerous sexual organs, which, up to the time of fertilization, are (male and female) exactly alike. After fertilization the carpogonium divides into a series of cells, from which there grow out short, branched cells, on which the asci containing 8 spores are borne in abundance. The fructification is quite destitute of a covering. Though not agreeing with the general characteristics of the Discomycetes, it is yet more nearly akin to them than to any other forms of the Ascomycetes. Suborder 2. ERTSIPHE^E (fig. 1 B, p. 8.). Fungi growing on living plants and dead organic bodies, and consisting of a mycelium which spreads on the surface of the host and sends into it numerous liaustoria ; forming small globular fruits with thin coverings, which enclose one or several asci springing from a carpogonium. Illus- trative Genera : Erysiplie, DC. ; Eurotium, Lk. Structure and Life-history. The species of Erysiphe grow on the leaves and green stalks of Dicotyledons more rarely on Monocotyledons. The mycelium ramifies densely on the surface of the host-plants, through the epidermis of which it sends down numerous haustoria, and is repro- duced by conidia produced in series at the end of unbranched conidio- phores. As in many Ascomycetous and other Fungi, the conidia are the only forms of reproductive organs known in certain species, and this has, in the case of Erysiphe, as in the others, been productive of confusion of genera. For example, Erysiphe Tuckeri, a vine disease, was long de- scribed as a species of Oidium. On the other hand, in many other species of Erysiphe, the sexually produced fructification is easily to be found either adhering to the mycelium threads or free. Both conidia and the sexually produced fruits are borne on the same mycelium. The car- 467 pogonium is surrounded by numerous pollinodia, and fertilization takes place in the same way as in the Discomycetes. In some species the fertilized carpogonium contains only one ascus of an ovoid shape, which encloses eight ascospores. In other species the carpogonium contains several asci. The species of Enrotium, e. g. E. repens and E. (Aspergillus) glaueu-s, agree in the essential details of their life-history with those of Erysiphe. The mycelium is floccose, and may be found on the surface of the most varied dead organic bodies. First are formed conidia in great abun- dance in clusters at the apex of the conidiophores, and these reproduce the mycelium so plentifully, that this fact, when coupled with the easily satisfied requirements of the fungus in the matter of hosts, accounts for its exceedingly wide distribution. On the same mycelium there arise afterwards the sexual organs. The carpogonium is the end of a mycelial hypha closely wound up in the form of a corkscrew, and provided with several transverse septa one to each turn of the screw. From the lowest turn there arise two tubes which grow up on the outside of the carpo- gonium ; one grows more rapidly than the other, and reaches the top of the carpogonium, with which it conjugates. This is the pollinodmm. Other cells then grow out from the bottom of both organs and envelop them. After fertilization the carpogonium divides into several cells, on the branches which proceed out of which the asci, containing 8 spores, arise. These ascospores germinate as in the other Erysiphece, and produce a mycelium which bears first conidia, and again the sexually produced fructifications perithecia. Suborder 3. TUBEEACE^E (fig. 1 C, p. 8). Eungi forming usually- large subterraneous tuberous fruits, possessing a thick wall (peri- dium) of pseudo-parenchyme, enclosing a dense mass of hypha), among which the ascogenous threads form many asci imbedded in the sterile threads. The mycelium is usually very small in com- parison with the fructification, and conidia are known only in the case of Penicillium glaucum. Illustrative Grenera : Tuber, Mich. ; Penicillium, Link. Structure and Life-history. The mycelium of Penicillium glaucum grows on almost all organic substances, and produces long chains of con- idia on erect conidiophores in such abundance as to account for their general presence in the air, and the appearance of the fungus on nearly every suitable and accessible host. It is only, however, in darkness that, like the other Tuberaceae, the fruits are formed. It is well known that the conidia are not developed in darkness, and this formation of sexually produced fruits in that condition (recently discovered by Brefeld) is a further mark of the capacity of this fungus for distribution. The sexual organs resemble those of JEurotium (above described) so closely that a description is unnecessary ; but the development of the fructification after the fertilization of the ascogonium is different from that of any other Ascomycete. Shortly stated, the ascogonium after it has begun to ger- minate is so hindered by the growth of the enveloping threads, that it is compelled to rest for some time in asclerotioid state. When germination is induced, however, by artificial means, the ascogenous threads are seen 2 H 2 468 SYSTEMATIC BOTANY. to force their way out and form asci, in each of which there are 8 aso.o- spores. These spores germinate and produce a mycelium, which again bears conidia. The sclerotia also when kept so long that the ascogenous threads have lost the power of forming asci, germinate and form the usual conidia. The sclerotia are in structure so similar to the well- known fruits of the Tuberacece (Truffles), that, however, strong the resemblance of the sexual organs may be to those of Eurotium, they must be classed with the former. In no other species of Tuberacece have conidia been observed. Suborder 4. PYRENOMYCETES. Fungi growing usually on dead organic bodies and on living plants, and forming round or flask- shaped conceptacles (perithecia) with walls of pseudo-parenchyme, and containing long club-shaped asci, each of which produces (as a rule) 8 spores. The perithecium is in some cases open at first, but in others an opening is ultimately formed in the neck of the flask, through which the spores are emitted. (It is not yet clear whether this fructification be generally the result of sexuality or not.) When the ascospores germinate, they produce a mycelium on which are formed conidia, stylospores (in pycnidia), and sperm- atia (in spermogonia). In many species one or more of these organs are wanting, and in many others one or more of these are present and the perithecia wanting. Illustrative Genera : Clavi- ceps, Tul. ; Nectria, Tod. ; Spliceria, Hall ; Xylaria, Hill ; Dichcena, Fr. ; Venturia, Er. ; Stiymatea, M. Structure, &c. In a number of species (e. g. the Sph&ria siniplices) the perithecia arise on a very fine mycelium, singly or in groups, and in such cases it seems to be probable (from Woronin's observations) that they are the result of a sexual act. In other cases, however (as in Xylaria), the perithecia are formed on large club- or basin-shaped stromata, consisting of dense masses of tissue. It is uncertain whether the stroma be merely a receptacle, or whether there takes place in it a sexual act which gives rise to the perithecia. The conidia are formed not only on the mycelium, but also on the stroma or even (as was seen to be the case in PeniciUiian) on the wall of the perithecium. Sometimes conidia and slylospores of two different forms occur in the same species. It has been suggested that the spermogonia and pycnidia are merely parasitic on the Pyrenomycetes j but this view has, in the case of the pycnidia, been recently disproved by the researches of Dr. Bauke, and in the case of the spermogonia by M, Cornu, who was the first to cause the spermatia to germinate and repro- duce the mycelium. This Suborder, like the Discomycetes, includes a great number of forms, many of which seem to be only stages in the life- history of other plants, and which have received the names of distinct genera and species. Suborder 5. LICHENES (figs. 516 & 517). Fungi consisting of a thallus of densely interwoven hyphae, sometimes forming pseudo- parenchyme, deriving their nourishment from minute Algae FUNGI. 469 (formerly called gonidia) imbedded in the thallus (such as Palmella, Nostoc, &c.), and forming regular organs of fructifica- tion (apothecia) containing asci, in some cases known to be the re- sult of a sexual process. There are formed also on the thallus spermo- gonia containing spermatia (the male organs, which have been proved in cer- tain cases to fertilize a female organ called a trichogyne) and occasionally pycnidia. - Illustrative Genera : Opegrapha, Pers. ; Umbilicaria, Hoffm. ; Verrucaria, Pers. ; Endo- carpon, Hedw. ; Sphcerophoron, Pers. ; Gladonia, Hoffm. ; Lecidia, Ach. ; Stereocaulon, Schreb. ; Parmelia, Fr. ; Stieta, Schreb. ; Getraria, Ach. ; Roccella, DC. ; Ramalina, Ach. ; Collema, Ach. Structure and Life-history. The para- sitism of the fungal portion of the Lichen thallus is not of such a nature as to cause the death of the host alga, but the relations seem to be so equally balanced as to allow of the protracted mutual existence of both. To illustrate this and the life-history of the Lichenes two instances will perhaps be sufficient, Fig.^516. both of which are from the recent re- searches of Dr. Stahl. Sexuality is not known to exist gene- rally in the Lichenes ; but since it has been established in the Collemacece (an important subdivision) we may fairly conclude that the matter only wants investigation to bring more instances to light. In this subdivision the minute male cells or spermatia are formed within closed receptacles called spermogonia, and, unendowed with the power of motion, reach the female organs by the conduction of water (rain, &c.). The female organs or trichogynes may be said to be composed of three parts according to their function : (1) a unicellular organ of conception, (2) a conductive canal, (3) an ascogonium in the form of coils, also composed of several cells which, when fertilized, give rise to the spores. The point of the trichogyne is protruded through the surface of the thallus, in which the rest of the organ is imbedded, and the spermatia coming in contact with it, the contents become amalgamated witb the result of fertilization. The first result of the fertilization is seen in the increasing size of the cells of the ascogonium, and also an increase in their number by the formation of transverse septa. The paraphyses A. Fertile branch of the thallus of Sphcerophoron coralloides, with a, a perithecium, and 8, sper- mogonia B. Thcae and para- physes from the perithecium. C. Spermatia from the spermo- gonium. Fig. 517. A. Branch of Ramalina fraxinea. B. A fragment with apothecia. C. A section of a fragment magnified, showing, a, apothscium, and , spermogonia. 470 SYSTEMATIC BOTANY. then spring from the primitive coil of the ascogonium and increase in number with the formation of the hymenium, on which ultimately the asci arise from the ascogenous threads. The production of spores by the asci terminates the generation. As to the relations between the parasite and host, the following instance will prove illustrative. The Algae embedded in the host received the name of gonidia before their nature was truly understood, and it was generally supposed that they were special organs. A smaller form of gonidia, called the hymenial gonidia, was found to occur also in the empty spaces of the apothecia of many Lichens. They are the offspring of the true gonidia by division, and are earned up in the hymenium by the growth of the hyphse. They are cast out of the apothecia along with the spores, and the spores on germinating envelope with their germ-tubes the hymenial gonidia, which increase in size and become the thallus-gonidia of the new lichen. This has been observed in Dermatocarpon Schaereri and Polyblastia rugu- losa by Dr. Stahl. Beside the Dermatocarpon there grows a species of Thclidium the gonidia of which are the same species of alga (of the genus Pkurococcus} as those of the genus Dermatocarpon. If the spores only of the TJielidium be brought together with no other organisms than the hymenial gonidia of the Dermatocarpon, the thallus of the Thelidium with the characteristic fructification may be obtained on a suitable sub- stratum, thus proving that the same species of gonidia can nourish two Fungi of even different genera. It must not be assumed that the above history of the gonidia is true of all Lichens under all circumstances, since no doubt the great majority of Lichens find their hosts in a more acci- dental fashion. The gonidia reproduce themselves exactly like the free individual Algse of the same species or genus. Distribution. Lichens grow mostly in exposed situations, such as on rocks, walls, trees, &c. in all parts of "the globe. They form a very large proportion of the entire vegetation in the higher regions of mountains and in polar latitudes. The thallus has usually a dry, dead-looking aspect (though sometimes soft and pulpy), and is of a foliaceous or scaly and crustaceous form. It varies much in size. Qualities and Uses. Many Lichens are very nutritious ; a number of them yield valuable dyes ; some are medicinal, others aromatic. Among the more important nutritious kinds are : Cladonia rangiferina, " Reindeer Moss ; " Cetraria islandica, Iceland Moss, and C. nivalis ; Umbilicaria (various species), constituting " Tripe-de-roche" of the North- American hunters ; Lecanora esculenta (Tartary) and L. affinis, Sticta pulmonaria, c. From Lecanora tartarea, the purple dye called Cudbear is obtained ; Parmelia parietina, common on walls and roofs, gives a yellow colour ; Roccella tinctoria (Mediterranean and Cape-Verd Islands, &c.), R. fu- ciformis (Madeira, Angola, Madagascar, S. America), and R. hypomecha are Orchil-weeds, from which the dyeing material Orchil or Orchel is ob- tained litmus being obtained from* thes^ and other species of Roccella. Some species contain a considerable quantity of oxalate of lime in the form of crystals. FUNGI. 471 MYXOMYCETES. When young, naked, mobile, in consequence of which the masses of plasmodium have a changing form. These masses, at the time of fructification, sometimes dividing themselves into single parts, are transformed into motionless fruits. Eruit either irregular in form (plasmodiocarp) or regular (sporangium). Sporangia, through fusion and union, produce now and then compound fruits (dEtha- lium) usually of considerable dimensions, of regular or irregular form, naked, or covered with a common coat (cortex). Spores produced within the fruit through free cell-formation, or on the surface through division. The contents of the spores at the time of germination give rise to either at first a naked zoospore, provided with a nucleus, a cramped vacuole, and long cilia, or to an amoeboid. These zoospores or amoebae, flowing together in masses, give rise to mobile plasmodia. (Rostafinski.} Illustrative G-enera : Physarum, Pers. ; jDidymium, Schrad. ; Spumaria, Pers. ; fStemonitisj Grled. ; Amaurochcete, H. ; Dictyostelium, Bref . ; Cri- braria, Pers. ; lleticularia, Bull. ; Trichia, Hall ; Lycogala, Mich. Structure and Life-history. The Myxomycetes present in the course of their life phenomena so entirely different from those occurring in other Thallophytes, that it has, with much reason, been proposed to separate tliem from this great group, and to place them among animal organisms, to which at least one stage of their existence shows the greatest simi- larity. The mobile or plasmodium stage resembles very strongly the mobile amoeba, of the animal qualities of which no doubt has been entertained ; but the fructification is so little like the " encysting " of these animals, or any other process in animal life, and moreover is so fungal in its nature, that this proposition has not been generally accepted. Not only the habit of life, but even the processes of nutrition of the plasmodiam stage are animal. These organisms are to be found in damp situations, on rotting wood, leaves, &c. The whole of this subject is so large and many-sided (and its relative importance here is so small), that for details of the life-history of these organisms the student, must be referred to De Bary's 'Mycetozoa,' and for their systematic disposition to Rostafinski's Monograph of the Order. Incidental reference will be found to them under the head of Physiology. SCHIZOMYCETES. The Schizomycetes, which are the lowest forms of life known, inhabit fluids which contain organic matter. The majority consist of extremely minute cells which neither in their membranes nor contents exhibit any marked characteristics. They are usually present in great abundance wherever putrifying organic matter is found. Among them are included such forms as Bacteria, Sarcince, Vibriones, Spirilla, some of which show a slightly higher organiza- 472 SYSTEMATIC BOTANY. tion than others in the possession of cilia by which motion is effected. They usually multiply by simple segmentation; but in such cases as Bacillus an apparent reproduction by means of sporules has been observed. It is probable that some of these organisms are stages Fig. 518. Fig. 519. Fig. 518. Various species of Bacterium. Fig. 519. Bacterium termo, magn. 2400. of some more perfect plant. The small Schizomycetes called Bacteria are often found growing on the mucous surfaces of living bodies and on wounds, &c. ; and on this subject there has arisen an extensive literature, which is of more medical than botanical interest ; and there is no doubt that, in a great multitude of cases, the observers have mistaken the products of the decomposition of organic bodies and crystalline precipitations of an inorganic nature for Bacteria. Whether the Bacteria are the real causes of fermen- tation and of various diseases, or whether they are merely concomitants of those processes, is a debated point upon which it is impossible to enter here. Allied to the Schizomycetes, though of a higher organization, is the genus Saccliaromyces (or Torula}, to which the Yeast-plant belongs. The Yeast-plant consists of single, roundish minute cells of greater size than those occurring in the Schizomycetes. It inhabits fluids which contain sugar, in which it excites alcoholic fermentation. The cells contain true protoplasm, which can easily be recognized as such, and in which vacuoles are usually to be found. They multiply by simple exogenous or endogenous segmentation (fig.'l A, p. 8, fig. 587, p. 552). The life-history of the Yeast-plant is further treated of under the head of Nutrition in Cellular Plants, to which the student is referred (see p. 552.) PART III, PHYSIOLOGY, CHAPTER I. PHYSIOLOGICAL ANATOMY OF PLANTS. Sect. 1. THE STEUCTUEE or PLANTS. The Physiology of Plants is that department of Botany which treats of the phenomena of the Life of Plants, as manifested in a series of changes taking place in the diverse organs of which each plant is composed. These organs, as we have already seen (MOEPHOLOGY, Chap. I.), are not simply fragments, combining to increase the bulk of the object (their size alone having no definite relation to that of the entire plant), but they are instruments, variously occupied in performing the different functions, the continuous operation of which indicates the existence of what we call Life. For morpho- logical purposes it is best to use the word " part " or " member " without reference to physiological function, which may be different in parts of the same morphological nature. For physiological purposes the term organ is now employed. The external characters of the parts of plants, generally, have been described in the First Part of this work, and an indication of their func- tions has been conveyed by their classification under the heads of Vege- tative and Reproductive Organs. But the object of the Morphological chapters was to point out the conditions and relations of Form, as pro- duced by the external shapes of the individual organs and their modes of combination. Here we have to examine the phenomena of Vitality, as displayed in the changes they present in the course of the Development, Growth, and Multiplication of Plants. The physiological Organs of plants are themselves composed of a number of parts, which again exhibit a kind of completeness of their own, and a relation to the organs analogous to the relation 474 PHYSIOLOGY. o the latter to the entire plant. These ultimate parts of organic bodies, arrived at long before we reach the limits of the possible mechanical divisibility of the objects, constitute the " atoms," physiologically speaking, of plants, and are called the Elementary Organs. Under certain limitations, we may compare a plant, or an organ of a plant, to a crystal. Each has its definite character by which it is possible to distinguish it from any other object. But we might pulverize the crystal, and yet any one fragment of sufficient size for operation would display to the analyst all the chemical qualities of the entire crystal ; and if we dissolved such a fragment and crystallized it upon a slip of glass, we should perceive by means of the microscope that it solidified into a miniature representation of the original crystal ; moreover, if we then collected all the fragments and dissolved them, we might by careful evaporation reproduce a crystal exactly like that from which we started. In Vegetables (as in Animals) the' case is entirely different. When we cut a plant in pieces, the parts differ not only in form but in structure, and bear no longer any recognizable relation to each other ; we cannot reproduce the plant from them, and even the chemical ex- amination of different fragments may give most diverse results ultimate analysis alone, by which they are resolved into their mineral elements, arriving at the detection of a common bond among them, that of being formed of compounds which we only meet with in organic matters. Above all, in the act of subdivision, although this may be carried to a high de- gree in plants without destroying life (even sometimes within the limit of single organs), beyond a certain point it results in the annihilation of the especial force, the organizing or vital principle, by which the organs were made to combine their activity to produce the distinctive character as an independent individual object. The diversities of form and consistence of the Elementary Organs give rise to all the differences of physical condition in the organs of vegetation and reproduction; and all those changes which col- lectively constitute the life of plants depend on the combination of a multitude of minor operations which have their seat in the elementary organs, singly or as combined into tissues. The study of the Elementary Anatomy is therefore the only secure foundation upon which to build the Physiology of Plants. Cells, Protoplasm. The elementary organs of plants are all re- ferable to one primary type, which is not only recognizable through a comparison of the fully developed modifications, but is found to be the form in which all originate. This fundamental organ of vegetable structure is called a Cell, and may be denned as a closed sac composed of solid membrane, called the cell-wall, and filled with fluid, cell-sap, and semifluid matter, called protoplasm. It must not, however, be overlooked that living plants and living parts of plants can exist, at least for a time, without any bounding cell-membrane. The perfect cell is taken, in a morphological sense, STRUCTURE OF PLANTS. 475 as the fundamental unit for convenience' sake, and because it presents a definite form ; it is not, however, to be regarded as the ultimate structural unit, because detached fragments of it are capable of in- dependent existence under certain circumstances, and the proto- plasm, in which in all cases the whole vital activity centres, is capable of living and moving without a cell-wall. Cell-contents. The cell is the elementary organ of vegetable structure ; but it is not the smallest or most simple definite form in which organic matter may exist in plants. In the contents of cells we find granules of various kinds &c., and also fibres ; the former, however, are not direct constituents of tissues, but occur only among the contents of cells, as more or less transitory conditions of assimilated matter; while the latter merely form parts of the structure of the cell-membrane. Uni- and Multicellular Plants. Plants of the lowest organiza- tion consist of the ultimate or elementary organs in their simplest forms, and may even be so simple as to consist of a single ele- mentary organ or cell (figs. 503 E, 513). A step higher, we find plants composed of a few cells connected together into a definitely arranged group in their earlier period of existence, and subse- quently separating entirely into the constituent cells, each of which lays the foundation of a new colony. Tissues. By far the greater part of the species of plants are composed of an indefinite number of cells permanently combined together and forming what are termed the tissues. If the cells entering into the composition of a tissue are essentially alike, they form a simple tissue ; if cells which have undergone modifications which give them an essentially diverse character are combined in an ana- tomically well-defined tissue, this is called a compound tissue. In the Algae, especially the simpler membranous or filamentous forms, we may readily see the uniformity of the character of the cells throughout the thallus (p. 435) ; the same uniformity prevails through the cells of such tissues as the pith of Dicotyledonous stems, &c. But if we examine the wood surrounding this pith, or even the ribs running into the leaves, we find a variety of conditions of the elementary organs within the well- defined limits of these portions of woody tissue. Cellular tissue. The simple tissues of plants are divisible again into two primary groups, according to the mode of union of the constituent cells. In proper Cellular Tissues the cells, however firmly coherent, are only in contact by their walls, which form a persistent boundary between them. In a series of tissues most extensively developed in plants of high organization, the cells enter into closer relation, becoming confluent by the absorption of their contiguous surfaces, and thus converted into more or less extensive 476 PHYSIOLOGY. tubular bodies, which, in their various conditions, form what are called the ducts and vessels of plants. These constitute the Vascu- lar Tissues. Vascular tissues. What are called the vessels of plants are really compound elementary organs ; but it is not requisite to enter into more minute distinctions here, since the phenomena of fusion of cells into such compound organs are not very varied in plants, and in all cases the composition of the structure from a number of distinct cells is very evident. The tissues, simple and compound, enter into the composition of the Organs of Vegetation and Eeproduction of Plants upon a certain general plan for any particular kind of organ, but under specially modified arrangements, referable to a progressive series of types, in the several large Classes of the Vegetable Kingdom. Sect. 2. THE CELL. Form. The shape and sizes of the cells of plants are determined by causes of two kinds, namely : their own laws of growth, which are inborn and hereditary ; and the favourable or obstructive influ- ences which bear upon their development in each particular case. As a general statement, it may be said that the primary form of the Vegetable Cell is that of a sphere, and that deviations from that type are more or less attributable to secondary influences, arising from the connexion of cells in coherent groups. The spherical form is usually found in cells developed freely, i. e . not arising from mere subdivision of a preexisting cell. Thus we find em- bryonary cells and endosperm-cells in the embryo-sac of Phanerogamia, the spores of some Cryptogamia, together with many of the lower plants com- posed of one or few cells only, such as those of 'growing Yeast (fig. 587, p. 552), &c., presenting the spherical as the original form. But by far the most frequently occurring spherical cells, such as many poll en-grains, spores, those in the pith of young shoots of Dicotyledons, of the pulp of fruit, &c., assume this form subsequently to the earliest stage of development, being placed in circumstances which allow them to expand freely according to their natural tendency. The above general statement is subject to certain important exceptions, in which deviation from the typical form exists without any interference with the development of the cell according to its own laws ; these are met with principally in the lower cellular plants^ especially the Unicel- lular Algse, in which we find single free cells assuming the most varied but specifically determinate forms. Examples of this are offered not only by the Desmidiete, but by the more unequivocally vegetable Vaucheriee, Botrydium (fig. 503, E), and others. The interfering influences above referred to are of two principal kinds, namely : special directions assumed in the development, in obedience to THE CELL. 477 laws regulating the structure of the organism, or of the tissue, of which the cell forms part, e. g. unequal growth in particular portions ; and ob- struction to the possibility of expansion in certain directions, from the pressure of surrounding cells. These influences are very fruitful in producing variety of form. The first kind is the most important, and determines the general form of the cell ; the second in most cases affects merely the shape of its external Fig. 520. Fig. 521. Fig. 522. Fig. 520. Merenchymatous cells of the rind of Euphorbia canariensis. Magn. 100 diam. Fig. 521. Liber-cells of Cocos botryophora. Magn. 50 diara. Fig. 522. Parenchymatous cells from the leaf ot Orchis muscula. Magn. 200 diam. surface. The form of the cells of fully developed tissues is usually the result of both kinds of influence combined. In cells existing in combination we find three principal classes of forms, referable purely to the influence of the law of development : (1) the spheroidal, obedient to the fundamental type ; (2) the cylindrical, in which there is a more or less considerable tendency to elongate in the direction. 478 PHYSIOLOGY. of a vertical axis ; and (3) the tabular, in which there is an excess of deve- lopment in the direction of the two transverse axes. The spheroidalforra. presents every possible transition from the sphere (Pro- tococcus, figs. 513, 514, pollen of Passiftora, Hibiscus, cells of cortical paren- chyma, fig. 520, &c. ), through the ellipsoidal (usual in longer or shorter forms in the subepidermal parenchyma of leaves), to the fusiform or spindle-shape (most abundant in the cells of wood and fibrous structure, fig. 521), and the truly cylindrical, either of moderate length (cells of Confer vre, fig. 512, &c.), or drawn out so as to become what is termed filiform (cotton Fig. 523. Fig. 523. Section of a septum of an air-canal in the petiole of Saqittaria. Fig. 524. Stellate cellular tissue rrom the petiole of Kush. Magn. 300 diam. Fig. 525. Stellate hair from the petiole of Nymphcea advena. Magn. 300 diam. rn. Magn. 200 diam. and other cellular hairs). The spheroidal form also passes gradually, especially in epidermal tissues, into the tabular form. Modifications. Secondary modifications of these forms arise chiefly either from partial cohesion in lax tissues, from irregular growth, or from pressure in densely packed tissues. Thus the spheroidal form becomes, in lax tissues, an irregular spheroid in endless varieties (commonest of all in the parenchyma of leaves and rind of succulent stems), running out by degrees into lobed" and finally THE CELL. 479 stellate forms, by exclusive development of the free surfaces while the contiguous cells remain attached at a few points, e. g. in cells of the paren- chyma of leaves and leaf-stalks of many Monocotyledons (fig. 522), Musa, Sagittaria (fig. 523), &c., and above all in the cellular tissue of Rushes (fig. 524) and the steins of various aquatic plants. In the tissues of Welwitschia, as also in Araucaria and other Conifers, very large irregu- larly branching cells, covered with small crystals, may be seen : these are sometimes called spicular cells. The mutual pressure of cells, commonly exerted in stems, in seeds, hard parts of fruits, &c., converts the spheroidal into polygonal forms, of Fig. 526. Cells of the pith of Acanthus mollis, seen in a vertical section. Magn. 200 diam. which the more or less regular dodecahedron or tetradecahedron, giving an hexagonal section, and arising from equal pressure in all directions, is perhaps the commonest (pith of fully developed shoots of Dicotyledons, such as Elder, &c.), or cubic, found in woodv fruits, &c. The cylindrical becomes under the same circumstances prismatic, either six-sided with flat ends, or with three rhombic faces at top and bottom, the common form of the cellular tissue of the stems of herbaceous stems (fig. 526), or 4-sided 480 PHYSIOLOGY. with flat ends, as in the medullary rays of Dicotyledons, or with conical or oblique ends, the common form of wood-cells. Less frequent are the forms of spores and pollen-grains, sometimes only temporary, sometimes permanent, arising from the development of four cells by segmentation of a spherical parent cell ; these sometimes appear of the form of quarters of an orange, sometimes as tetrahedra, the curved surface forming the base of the pyramid. In the tabular forms of the cell, the mutual pressure gene- rally confirms an originally rectangular figure, the tabular cells of epi- dermis and cortical structure being usually of quadrangular or polyangular Fig. 527. Fig. 528. Fig. 527. Young prothallium developed from the spore of a Fern (Pteris serrulata). Magn. 200 diam. Fig. 528. Epidermis of the lower surface of the leaf of Helleborusfoetidus, with stomata (a). Magn. 200 diam. figure, flat above and below ; but in these we have sometimes complica- tion from expansion, under pressure, principally in certain directions, cells of the epidermis of many plants exhibiting side walls thrown into sinuosities following a particular pattern (fig. 528). By far the great majority of cells in the higher plants originate in forms analogous to those produced by pressure, since they mul- tiply by division, and the septa dividing two newly formed cells have ordinarily plane surfaces (fig. 527) : a spherical cell forms two hemispherical cells, &c. ; a prismatic cell dividing perpendicularly, two half-prisms, or, if horizontally, two superposed shorter prisms, &c. As a general rule these cells have a tendency to assume the spherical (or cylindrical) form in their earlier stages of growth, while the whole mass of tissue is lax ; and if they are set free, as THE CELL- WALL. 481 in the case of spores, pollen, &c., they often become quite spherical. But if they form part of a permanent tissue, the expansion of the organ of which they form part stops at a certain point, before they cease to swell, and thus the mutual pressure comes to bear upon them and causes the production of plane surfaces. We may trace this by making sections of a pith of a shoot of Elder from the growing point, or pxnctum vegrtationis, downwards : at the paint the nascent cells are squarish ; lower down they have swollen into sphe- rical, while when full-grown they are dodecahedral. The similar change from cylindrical to prismatic takes place in the cambium-cells of annual stem and shoots ; but in succeeding years the cambium-cells formed by division of preexisting cells exhibit a rectangular outline first and last, only increasing in diameter, chiefly in a radial direction. Dimensions. The magnitude of cells is very varied. About T J- F of an inch may be taken as an average of the diameter of paren- chyma-cells ; the cylindrical cells are especially remarkable for the great length they often acquire as contrasted with their transverse diameters, and with the transverse and perpendicular diameters of other forms. The larger cells of the pith of the Elder are about -^-^ of an inch in diameter, but ^ is to be regarded as a large diameter in parenchyma. On the other hand, the spores of Fungi affjrd examples of extremely minute dimensions, such as ? Vo to -g-^g TT f an i ncn - The cylindrical cells of wood are not uncommonly ^ of an inch in length ; liber-cells sometimes from -fa to or of an inch (Flax). Hairs composed of one or more cylindrical cells, and the cylindrical cells of some of the Confervre, especially VaucTieria y Srycpsis, &c., and Chara, also attain longitudinal dimensions to be measured in inches, while their diameter is estimated in hundredths of an inch. The Cell-wall. In all young cells the wall is of membranous nature, and in many cases it always retains this character. \V T hile young this membrane is freely permeable by water, elastic and flexible. As the cell-\vall grows older it becomes altered in con- sistence and firmer, opposing a greater obstacle to the entrance of water into its substance, independently of any great increase of thickness, as we see in cork-cells : when it increases in thickness it may remain soft and flexible, or become very dense ; but in such cases it generally remains tolerably freely permeable by water, even when most dense, while the softer kinds absorb water so readily that they swell up considerably when wetted. Membrane of living cells always appears to contain water as an essential part, almost like the water of crystallization in hydrated salts. When dried, cells contract more or less ; and many phenomena of bursting of fruits, sporanges, &c. are the result of the tearing down of weak regions of cellular tissue by the contraction of firmer tissues in drying. Cellular 482 PHYSIOLOGY. tissues with soft thick membrane, like those of the Algae &c., contract in drying so as to cause the shrivelling of the structure. All such tissues absorb water when wetted, and swell up again, but do not in all cases reassume their original flexibility. Cells of wood, liber, &c. also expand when wetted ; but the expansion takes place in a direction transverse to their axes, and they usually contract in the longitudinal dimension as they swell laterally. Hence, although wood and fibrous structures swell in water, it is only in the direction across the grain, and cordage simul- taneously contracts in the direction of the fibres. Diluted sulphuric acid and alkaline solutions cause a swelling of the membrane of most cells, of which advantage is sometimes taken in w r oven fabrics to render the stuff' closer in texture. By soaking in an alkaline solution, the single fibres are made to swell so as to come more completely into contact and fill up the interstices. Primary, unaltered cell-membrane is colourless ; subsequently it becomes coloured, usually of a tint of brown, apparently by infil- tration of substances formed in the contents, since by boiling the membrane of old, deep-brown tissues with nitric acid, or with solution of potash, the colouring-matter may be extracted. The original membrane of a newly formed cell is, as far as we have the means of perceiving it, a homogeneous layer of substance, the porous nature of which is, in most cases, only to be concluded from the fact of its permeability, no visible pores, except in excep- tional cases, being revealed by the most perfect microscopes we possess. It is important to note this homogeneity of the primary cell-wall, as .the membrane almost always becomes marked with dots and spiral lines, indicating inequality of thickness, as it becomes thicker. This primary membrane is apparently a secretion from the pro- toplasm, though by some it is looked on simply as a chemical pre- cipitate. It appears to have the property of growing by what is called intussusception of molecules, since it expands to accom- modate the increasing contents of the cell in cell-growth, with- out any indication of structure necessarily accompanying the expansion. No better example of this can be mentioned than the growth of the pollen-tube of Phanerogamia, which sometimes acquires a length of 2 or more inches (Cactus] without ever departing from the homogeneous pellicular structure. Cell-membrane, however, may increase in size by ex- pansion, as we see in the cell-division of GEdor/oniitm, in which a thickened ring of accumulated cellulose is stretched out by the elongating cell and becomes a thin membranous coat to the latter. Molecular structure. The molecular structure of cell-membrane has been studied by Nageli, who, from his researches on the constitution of the membrane of the starch-grain by means of polarized light, comes to THE CELL- WALL. 483 the conclusion that all organic substances are composed of crystalline molecules grouped in a definite manner. When dry the molecules are without interspaces ; when moist, each molecule is surrounded by a thin film of water. Nageli further supposes that each molecule is made up of a number of atoms, similar to or identical with the atoms of the chemist. The molecules are of different sizes ; those portions of the structure richest in water have the smallest molecules. The molecules themselves are of the nature of crystals with two optic axes. It is possible that the ex- tremely minute "dots and striae above mentioned may have some relations to this molecular structure. Secondary Growths. The walls of almost all cells soon exhibit a departure from the original simple condition, arising from the formation of new lamellae, more or less resembling the primary membrane, all over, or over particular parts of, the inside of the primary membrane. These are distinguished as secondary layers (figs. 529, 530). They are of different densities, and they are usually separated one from the other by thin films of watery cell- sap. The consistence of these layers, and the mode in which they are disposed, produce the most important diversities of character of the walls of fully developed cells. Fig. 530. Fig. 529. Transverse section of liber-cells of Cocos botryopkora. Magn. 2CO diam. Fig. 530. Transverse section of a thick-walled cell from the pith of Roya carnosa. Magn. 500 diam. The laminated condition of cell-membrane may be well observed in simple cellular structures by treating fragments of Cladophora glomerata, or other Large Confervoid, with diluted sulphuric acid. The laminae are very visible in cross sections of the cells of wood and liber after these have been boiled for a short time in nitric acid. These so-called layers are not successive depositions, but are formed like the cell-wall itself, of which, indeed, they are intrinsic portions, by intussusception of new particles alternately more or less dense. The term layer is therefore a misnomer, descriptive of an apparent and not of a real condition. 2i2 484 PHYSIOLOGY. Gelatinous Layers, Besides the primary membrane and the secondary formations, we find in certain cases a kind of envelope which has been variously explained by different authors. The fila- ments of some Confer voids (Spirogyra, fig. 512, A), of Desm-idium, &c., the families of cells of Palmellece (figs. 504, 513) and Nostoch- inece, are surrounded by a coat of gelatinous consistence outside the proper cell-membrane. This appears to be produced by the softening and swelling up of the parent cells (of many generations) of the cells which are surrounded by such envelopes. Cuticular Layers. Another layer is characteristic of many cell- membranes which are destined to protect the subjacent tissues, or their own contents, from, the action of the atmosphere, namely those of epidermal cells and of pollen-grains and spores. These exhibit a superficial pellicle, of varied character as to thickness, texture, and marking, which pellicle appears subsequently to the first formation of the cell. This, like the gelatinous coat just described, is a structure altogether of secondary character, but is distinguished from the ordinary secondary layers of thickening by its position on the outside of the cell-wall. It is still a moot question whether these pellicles are secreted by the primary membrane on the outside, or are formed by transformation of the outer laminre of the primary membrane itself, whose place is then taken by some of the outer secondary layers. This subject will be more dwelt upon under the head of the cuticle. Thickening Structure. The secondary formations on the inside of the cell-membrane may (1) correspond in character to the primary wall, in which case the cell-wall is simply thickened by new lamellae ; or (2) the new layers applying themselves over the surface of the wall, leave certain parts bare, which appear as dots or pits of various forms when viewed from the inside (figs. 531, A, B) ; or (3) they are applied only over parts which form peculiar patterns upon the primary wall, and appear, when of sufficient thickness, like^&m adhering to it, spiral, annular, or connected into a kind of network. Those secondary layers which resemble the primary wall, although evenly deposited, present in certain cases an appearance as though their molecules were arranged in a spiral order, since fine spiral streaks may sometimes be detected, after treating them with acids and by other means/ and many of them are apt to tear in a spiral direction. The excessively delicate spiral marking here referred -to (seen in liber-cells of Vinca, fig. 53.3, and most Apocynacese and AsclepiadaceaB, in wood- cells of Pimis, in the cell-membrane of Hydrodictyon, &c.) must not be confounded with a deceptive appearance, resembling a much coarser spiral striation, produced by treating the membranes of Confeme, the paren- THE CELL-WALL. 485 chyma-cells of Orchis, CucurUta, &c. with sulphuric acid, where the appearance often results from the irregular convolutions of the swollen lamellaa of the cell- wall. Fig. 531 B. Fig. 531 A. Pig. 531 A. Section of cells of the endosperm of a Sago- Palm. Magn. 200 diam. Fig. 531 B. Laminated cell- walls of the cells in A. Magn. 500 diam. The uniform kind of secondary layers are sometimes accumulated at one side (fig. 534), or in the angles of cells (fig. 535) : thus they are much thicker on the side of epidermal cells next the air ; and they fill up the angles of the cells of the fleshy endosperm of many seeds, the cells of the collenchyma found beneath the rind of Chenopodiacese, and the cells of the leaves of Nymplicea, of some Jungermanniacese, &c. There is reason to believe that, in some instances, the cell-wall thickens at certain seasons and becomes thinner at others ; but this appearance may arise from an alter- nately swollen and contracted state, and not from absorption and redeposition. The subject will be alluded to again under the heads of epidermis and intercellular substance. Pitted Cells. The deposits which leave spots of the primary membrane bare form what are called pitted, or, less properly, porous cells. They occur on the walls of most cells of the parenchyma- tous structures of the higher plants, in the form of round spots (fig. 526), where the still membranous cell-wall is thinner. In wood-cells, in liber-cells, and the greatly thickened cells of fleshy endosperms, hard seed-coats, &c., the formation of a great num- ber of secondary layers upon the wall, always leaving those spots bare, converts the pits into canals running out from the contracted cavity to the primary wall (figs. 530, 531). The marks are really always pits at first, as may be seen by colouring the cell-membrane with iodine. But in old wood-cells they appear some- 486 PHYSIOLOGY. times to become holes, by the absorption of the primary membrane which formed a kind of diaphragm over the outer end. These pitted markings may be circular, oval, or elongated transversely or more or less obliquely, so as to approach to the appearance of slits. Sometimes the. later secondary growths do not extend quite to the edge Fig. 534. Fig. 532. Fig. 533. Fig. 535. Fig. 536. Fig. 532. Liber-cell of Periwinkle. Magn. 75 diam. Fi*. 5*i. Fragment of the cell in tig. G/,2, magnified 300 diam. (The spiral lines on the- urn ><>- Bite side of the cell show th-o'.'-h ami cross.) Fig. 534. Vertical section of epidermis of Vucum album, with many th ickening layers. Magn. Fig. 535. Transverse section of cells of the petiole of Nymphaea alba, showing the larniiml<-rl WHil. j>iugii. 500 dijini. Fig. 536. Fragment of a pitted duct of Laurun sassafras. Magn. 200 diam. of the aperture in the earlier layers, and the successive layers may so retreat from this edge that the canal becomes at length fapnei-*hftped ; in this case the pit, \vhon Been in front, presents a doubl" oufJj: . . one corresponding to the outer end, the other to th<; inner and wider end (fig. 530;. THE CELL-WALL. Bordered Pits. This condition may be further complicated by the existence of a lenticular depression between the contiguous walls of pitted cells, as in the wood of Comferae (fig. 537). The outline of this depression ives the appearance of a circle surrounding the central pit the circle eing due to the greater thickness of secondary growth in that situation. .1 , . i ^ * 3 *.!** Fig. 537. Pits or " GUnde" of Convene. Magn. 10X) diwu. tion which is the primary deposit of the two cells. The lenticular cayity is formed by the resorption of this deposit, and a communication esta- blished between the two adjacent cells. These areolated pits (or i?te, - hacht calls them) are not, as was once supposed, confined to the ra? ; but they are universally found throughout that group with a regularity of disposition and constancy of occurrence not known else- re. Lattice or Clathrate Cells, Sieve disks. A further compli- cation of the pitted structure has been described by Von Mohl a- uA'iirrm^ iu the vctsa propria of the vascular bundles of Mono- !bn$,and in the thin-walled cells, layers of which alternate 488 PHYSIOLOGY. with the long woody fibres in the liber of Dicotyledons. In these cells, which that author calls " latticed " or " clathrate " cells, the membrane which forms the diaphragm closing large pits is marked with an excessively delicate network, apparently formed of fibres applied upon the primary membrane, and generally per- forated. This occurs not only in the pits of the side-walls, but in those which are found on the septa between cells standing one above another, and which constitute ihe sieve disks of the Germans, the said disks being covered on one side with a thick hyaline struc- tureless perforated plate, not coloured blue by iodine, and whose nature and functions are at present unknown. Spiral Deposits. The " fibrous " secondary layers may present the form of a single spiral band, running from one end of the cell to the other, and with the turns of the spire quite close or more or less distant (fig. 538) ; or the spiral band may be double, Fig. 540. Fig. 538. Fig. 539. Fig. 538. Cell from the sporangium of Equiseium arvense. Magn. 2nO diam. Fig. 539. Cells from the sporangium of Marchantia polymorpJM. Magn. 250 diam. Fig. 540. Cells from the leaf of Sanseciera yuineensis. Magn. 400 diam. triple, or even consist of six or more parallel bands. Very often these spiral secondary deposits are sufficiently elastic to allo\v of their being stretched out, the comparatively thin primary membrane to which they adhere giving way at the interstices. In the cells of the coat of the seed of Cottomia, the primary membrane becomes, during the ripening of the seed, converted into a substance which softens and swells up in water ; so that when this structure is wetted, the spiral fibre springs out, opening its coils widely like a wire spring. THE CELL-WALL. 489 The annular thickenings (fig. 539) are less common than the spiral, but occur sometimes in the same cell, and also in association with the next kind, the reticulated. The rings are generally at some little distance apart. The reticulated secondary layers may be uniform over the wall o the cell, or irregular (tig. 540), which' is more frequent, since the ordinary cause of the reticulated appearance is the formation of vertical connecting bars between rings or spiral coils at the angles of the cells ; when this occurs very regularly, a ladder-like arrange- ment results, giving what is called the scalariform structure, espe- cially frequent in the vascular structure of Ferns (fig. 541). Fig. 541. Fig. 542. Fig. 541. Fragment of a scalariform vessel of a Tree Fern : a, walls in contact with other vessels : b, b, walls in contact with cells. Magn. 200 diam. Fig. 542. Wood-cells of Yew ; vertical beetion. Magn. 300 diam. The connecting bars of the reticulated and scalariform cells must not be supposed to originate after the rings or spirals ; they are contempo- raneously developed ; and the diversities in the closeness of the coils of cells are likewise original peculiarities of the deposits. The statement that the turns of spiral coils are opened by longitudinal growth of the primary membrane to which they adhere seems to be founded on specu- lative notions. The spiral structure of secondary deposits is beautifully seen in the elaters of Junf/ermannia and Marchantia, in the cells of the aerial roots of epiphytic Orchids, in the cells of the wood of Cactaceae, and in the spiral vessels of the veins of the leaves and leaf-stalks of Monocotyledonous plants, such as the Hyacinth, Narcissus, Musa (which presents as many as 20 parallel bands), shoots of Elder, leaf -stalks of garden Rhubarb, Strawberries, &c., also in the petals of delicately organized flowers. Annular cells are well seen in the sporanges of Marchantia and other Liverworts, and in many of the structures just mentioned with spiral and reticulated cells. Scalariform Tissue. The scalariform marking is most regular in Ferns, and approaches very nearly to the more regular forms of the thickening above described, so that the spiral-fibrous and tjie dotted forms appear as the extremes of an analogous kind of structure. 490 PHYSIOLOGY. In many wood-cells, especially in root-structures, the reticulated or scalariform cells have the meshes so small that they become in fact pitted cells. Tertiary Layers. In some cells both kinds of thickening occur, so that it is convenient to distinguish tertiary growths. In the wood-cells of the Tew (fig. 542), of the Lime, and other plants the secondary layers are pitted, and a tertiary growth subsequently appears in the form of a spiral fibre. The pits on the walls of contiguous cells correspond, and they do not generally occur opposite intercellular spaces, or on the outside of epidermal cells; but exceptions occur to both these rules, to the latter especially in the leaves of Cycas. The first rule has much influence on the marking of the large cells forming part of ducts, which are often in contact with several cells, one above another, and with parenchyma-cells, other ducts, or with intercellular spaces, on different sides. In the wood-cells of Conifers, the peculiar bordered pits occur only on the sides parallel to the medullary rays, not on the internal and external walls. Cellulose, &c. Cell-membranes, including the secondary layers, are composed of the substance called cellulose, which is one of a class of organic compounds intimately connected as regards chemical constitution, but presenting remarkable physical differences. Of these compounds the most important are : sugar and dextrine, soluble in cold water, and occurring in solution in the cell-sap ; starch, insoluble in cold, but softening and swelling into a mucilage in boiling water, and found in the form of granules in the cell- contents ; and cellulose, insoluble in cold or boiling water, alcohol or ether, obstinately resisting the . _, action of alkaline solutions, but soluble . ^ in strong sulphuric acid, and forming the permanent solid parts of vegetable structure. This cellulose is supposed to be derived from one or other of the materials above mentioned. ' Cell-membranes, originally composed of pure cellulose, undergo changes at sub- sequent periods which alter, in a marked manner, their behaviour towards chemical reagents ; and it is not at present certainly ascertained what is the real cause of the series of modifications which they present. If we compare the membrane of a nascent cell, of thick-walled parenchyma, the solid and often dark-coloured walls of the cells of old heart-wood, of liber-cells, the very resistant membranes of corky tissues, and the layers of gelatinous or cartilaginous consistence so abundantly developed in the larger Algae, we meet with extremely different characteristics, as to the explanation of Wall of the cells of the liber of Cocos : a, primary membrane ; 6, oldest secondary layers; c, more recent secondary " layers ; the layers marked b are strongly in- crusted. Magn. 600 diam. THE CELL-WALL. 491 which different views are entertained. On the one hand it is said that the cellulose produced in the formation of the original membrane or layer of thickening becomes gradually converted into different but related chemical compounds ; on the other, that the cellulose layers become im- pregnated by foreign substances, gradually infused into them from the fluid contents, sucli substances being distinguished by the name of in- crusting matters (fig. 543). A third view is that of Fremy, who con- siders that there are several kinds or modifications of cellulose, and, more- over, that those vegetable structures formerly considered to be made up exclusively of cellulose contain matters of a different chemical com- position. Action of Reagents on Cellulose. Cellulose, as found in the organized condition of cell-membrane, appears to behave somewhat differently to chemical reagents according to the state of aggregation of its particles (that is to say, its density) ; for nascent cell-membranes will in many cases assume a violet or even a blue colour when treated with a strong solution of iodine and washed with water, like starch. The same is the case with some of the sernigelatinous layers of thickening met with in the endosperm or cotyledons of certain seeds (called amyloid}, and, moreover, in the cell-structures generally which have been treated in the way de- scribed below, to remove the so-called " incrusting matters." But, as a general rule, cellulose does not take a blue colour with aqueous solution of iodine, unless some other agent, especially sulphuric acid, be applied at the same time. A solution of iodine in zinc chloride brings out a blue colour in fully developed cell-membranes, still more readily than the sulphuric acid with iodine. These reagents readily affect newly formed tissues in general ; and the more delicate kinds of cellular tissues are permanently sensitive to them. But after a time the thicker cell- membranes, and especially those of woody tissues, the cartilaginous structures, and the tissue of epidermis and bark, no longer become blue, but only yellow or brown, with the above reagents ; and it is the real cause of this alteration which is the subject of the difference of opinion above referred to. Anilin and sulphuric acid stain the lignified cells yellow *. By maceration for several hours, or boiling for a minute or two, in nitric acid for woody and cartilaginous tissues or in strong solution of potash for epidermal and corky tissues, bringing the cells to a point where they still exhibit all their structure, but are bleached and softened, then washing * The iodide solution consists of 1 grain of iodine, 3 grains of potassic iodide, and 1 ounce of distilled water. The sulphuric acid is of the strength of three parts acid to one of water. The preparation to be examined is first moistened with a drop of the iodine solution, which is then wiped off with a brush or piece of blotting-paper, and a drop of the acid is then placed on the preparation, which is covered with thin glass in the usual way. Schulze's solu- tion is made by dissolving an excess of metallic zinc in strong hydrochloric acid, allowing the solution to evaporate over a spirit-lamp to the consistence of syrup, the zinc being kept constantly added if necessary. To the now colourless syrup is added as much potassic iodide as it will take up. The ad- vantage of Schulze's solution is that it does not destroy the tissues, acts more speedily, and is less injurious to the microscope should it happen to come into contact with it. 492 PHYSIOLOGY. them with water and applying iodine, a blue colour is produced like that appearing in nascent cellulose or in tolerably new tissues under the influence of sulphuric acid. It remains to be ascertained whether these processes alter the com- position of the cell-membranes, or merely remove infiltrated matters of nitrogenous composition. The latter view is supported by the fact that, in imperfectly prepared objects, some of the more resisting layers appear Creen, which would seem to result from an optical combination of the lue of the cellulose with the yellow of an infiltrated matter. At the same time it must be noticed that the cellulose is brought into a condition approaching that of starch, only normal in nascent membranes and in the semisolid deposits of " amyloid " above mentioned. Fremy, as above stated, considers that there are other substances besides cellulose entering into the composition of vegetable cell-walls. Tt*ue cellulose forms the cell-wall of the cellular tissue of bark, fruits, roots, &c., and is soluble in ammcniacal copper oxide, made by dissolving copper filings in caustic ammonia. Paracellulose is found in the cells of the pith, the epidermis, the medullary rays, &c. ; it is soluble in the copper solution, but only after special treatment. Fibrose is the constituent of the wood-cells, and is insoluble in the copper solution, except after special treatment, but soluble in strong sulphuric acid. Vasculose, the substance of which vessels are formed, is insoluble in hydrochloric and sulphuric acids and in the copper solutions, but soluble in boiling caustic potash. It is coloured by anilin with a little sulphuric acid. Inorganic Constituents. Cell-membrane in most cases contains a certain amount of inorganic matter ; but this is probably attribu- table in general to its being saturated with the watery cell- sap, in which various salts exist in solution. In particular cases, however, there is a special deposition of inorganic substance in the walls of cells as, for instance, in the Grasses and the Equisetacese, and the Cane-Palms (Calamus), where the epidermal structures are so loaded with silex that they not only acquire a hard texture, render- ing them harsh to the touch, but, when the organic matter is de- stroyed by burning, a complete skeleton of the tissue remains, entirely formed of silex. The siliceous coats of the Diatomece afford another striking example. It is not yet clearly made out whether the silex is here deposited in a layer upon the cell-membrane, or interpenetrates its substance ; but the latter is probably the real state of the case. The pericarp of some plants, as Lithospermum, contains lime, in what form it is not certain ; but the calcium carbonate incrustin^ the cells of many species of Chara is clearly a mechanical deposit upon the outside of the membrane. The membranous wall of the vegetable cell is for the most part a permanent structure : forming the " skeleton " of plants, ti usually remains entire until the decay or destruction of the organism in which it exists. It is, as previously stated, in some cases subjected to periodical variations in thickness, accord- ing to season. Frequently it becomes absorbed or dissolved, THE CELL-WALL. 493 ultimately at particular points, as at the contiguous end-surfaces of those cells which become fused together to form vessels or ducts ; and in the case of the layer closing the outer ends of the canals of the pits or wood-cells, a similar destruction of the primary membrane seems to occur. A phenomenon of this kind is distinctly presented in the large spiral-fibrous cells of Sphagnum (fig. 544), where the walls of old cells are found perforated by large round orifices, produced by the separation of circular pieces of the cell-wall, and in the cells of the leaves of Leucobryum glaucum (fig. 545). In the cells of the Confervoids producing zoo- Fig. 545. Fig. 544. Cell of the leaf of Sphagnum cymbifoUum,mth annular fibres and orifices in the wall. Magn. 400 diam. Pig. 545. Porous cells of the leaf of Leucobryum glaucum ; vertical section. Magn. 400 diam. spores, the wall breaks open at definite places to allow these to escape, exhibiting small lateral or terminal orifices in Conferva (fig. 512, C, d) &c., or breaking quite across by a circular slit in (Edogonium. In this last genus the cell-wall breaks across in the same way in cell-division, to allow the new cells to expand ; and in one of the Palmellece {Schizochlamys) the wall of the parent cell splits off in segments every time a new generation of cells is formed. In the case of the clathrate cells and sieve disks pre- viously mentioned, the bounding membrane ultimately becomes obliterated so as to allow of the passage of the protoplasmic con- tents of one cell into the cavity of the adjoining cell. If a radial section be made of a latticed cell in the stem of a Vegetable Marrow 494 PHYSIOLOGY. and treated with iodine and sulphuric acid, the cellulose becomes stained blue, the protoplasm yellow, and threads of the latter may be seen passing from one cell to the other. In the formation of the ultimately free cells composing; pollen-grains and of the spores of the higher Cryptogamia, the cells are liberated from the parent cells by solution of the* wall of the latter. The outer layers of the cell-wall indeed often assume a different appearance from the inner ones ; and, as in the case of the pollen-tube, the outer coat dies and splits as the inner coat grows into a tube. A still more curious phenomenon occurs in the process of conjugation, where two cells coalesce by complete union of their walls. The last cases appear related in some degree to the origin of the gelatinous coats of the Palmellece and other Confervoids, which are probably produced by the disintegration of the walls of parent cells, which become softened and swell up as the new generations of cells are formed in their interior. Contents of the Cell. The solid cellulose structures forming the persistent mass of vegetable tissues may be regarded as a skeleton or framework; for the vital and chemical phenomena exhibited by plants all depend, in the first instance, upon operations which have their seat in the interior of the cells. The careful investigation of the cell-contents is consequently of primary im- portance in the study of Vegetable Physiology. The fundamental importance of the matters within the cell is not only demonstrated by what we are enabled to observe taking place in the in- terior of living cells, but, in certain of the lower plants, the vitalized con- tents actually emerge from their confinement in the shell of cellulose (as in the case of the so-called zoospores], move, perform all the functions of plant- life, and exhibit in the course of their subsequent conversion into closed motionless cells exactly the same power to form new cell-membrane as takes place in ordinary cell-formation. Cell-sap, &c. The contents of the cell are partly more or less solid, partly fluid. When substances exist dissolved in the cell-sap, they are frequently out of the reach of microscopic observation, on account of the minute quantities in which they exist, or from the want of suitable reagents to ascertain their presence ; among these are the vegetable alka- loids and similar products. The sugar, dextrine, mineral salts, &c. dis- solved in the watery cell-sap do not readily admit of examination in this way. The fluid colouring-matters, essential or fixed oils, resins, &c., on the contrary, are readily observed, on account of their distinct physical and chemical characters. This is still more the case with mineral or organic salts which are sufficiently abundant to crystallize in the cell. But by far the most important of the contents of cells are certain organized structures which are regularly met with in the cell-contents, either universally or, with certain definite exceptions, at particular epochs of the life of cells. These are the protoplasm, the nucleus, and chlorophyll* corpuscles, which are albuminous or proteinaceousin their character, while others are destitute of nitrogen, such as the starch-granules. CONTENTS OF CELLS. 495 Fig. 546. Protoplasm. In all young growing cells we meet with a tough muci- laginous semifluid sub- stance, colourless or with a yellow tinge, and fre- quently of more or less granular character, which increases with the age of the cell. This substance is called the protoplasm. The sperm or elementary units (male) and the cor- responding initial germs, or female organs, are fragments of naked protoplasm. The MvxomvcetOUR Funi aie Transverse section of cell of Junqermaunia Taylori: a, very remarkable. They ^SjS^X^Sf 1 ^^^^^^^^ consist of masses of proto- . plasm, called plasmodia, uncvered by cell-membrane, and which move by creeping over the substance on which they grow, show currents in their interior, and ultimately form reproductive bodies, covered with a cell- wall formed from their 'own substance (see p. 470). Latterly Mr. Francis Darwin has shown that protoplasmic filaments may be ejected and retracted from the cells of the leaf of the common Teazel. Ecto- and Endoplasm. The protoplasm generally presents a division into two layers the outer a hyaline film in contact with the cell- wall, and called the ectoplasm, the other of a granular character, termed the endo- plasm. The ectoplasm or primordial utricle is the outer film of the pro- toplasm, from which it differs in its greater density and different mole- cular structure. It may be seen by soaking the tissue in acetic acid, is coloured yellow by iodine, and is applied intimately to the inner surface of the cell-membrane of young cells, persisting in the cells of tissues which are concerned in the reproduction of cells or the perfor- mance of the functions of assimilation, &c., but disappearing at a com- paratively early period in cells which acquire fibrous or pitted woody secondary layers. The ectoplasm, lining the entire wall of the cell, forms a kind of sac ; but it is not a membrane in the same sense as the proper cell-wall, since, although it presents a certain cohesion and resistance to the penetration of water, it is not merely flexible, but ductile, and capable of moulding itself into new external forms, the sac, in cell-division, becoming con- stricted into two or more portions without wrinkling. When the zoo- spores of the Algae escape from the parent cell, the primordial utricle forms the external boundary of the structure of the zoospore, which has a definite form in each case. The ectoplasm presents a radial striation, rendered more evident by the action of osmic acid. According to Stras- burger it consists. of small rods of relatively dense substance, with the in- tervening spaces filled with cell-sap or watery protoplasm. The cilia of zoospores, which are extremely fine vibratile threads, are productions 496 PHYSIOLOGY. from the rods. The cellulose coat of the cell is secreted by the ectoplasm. The molecular structure of protoplasm is probably varied in different cases. The investigation of this obscure subject is of immense import- ance, as the functions of life seem to depend on the activity and behaviour of the molecules of protoplasm. They have been recently called plasti- dules, and, unlike the molecules of the cell-coat, are not crystalline. The protoplasm is not always readily discoverable in living cells, on account of its close apposition to the cell-wall, but it ma}^ be detected by the application of a weak solution of iodine, which colours it brown, and soon causes it to contract and separate from the cell-membrane (fig. 546). The contraction is disadvantageous in some cases, if it go very far, as the layer becomes applied upon the inner cell- contents. The structure is very well seen by placing portions of the green tissue of leaves, &c. (which retain the primordial utricle after acquiring their full size), of the pulp of fruits, the leaves of Mosses or Liverworts (fig. 546), or the fila- ments of Confervoids, in alcohol, or treating them with dilute nitric or hydrochloric acid. The primordial utricle then separates from the cell- wall without becoming much discoloured. The chemical properties of protoplasm indicate its affinity to albuminoid substances. It is, moreover, mixed with oily substances and inorganic or incombustible materials. Vacuoles, &c. In young cells, such as those in the cambium- layer of stems, in the growing parts of leaves, &c., the protoplasm nearly fills up the cavity, or at all events occupies all the space not filled by the nucleus. By degrees, as the cell expands, spaces called vacuoles make their appearance in the protoplasm, filled with watery cell-sap (fig. 547) ; they may be regarded as drops of watery fluid surrounded by protoplasm, which latter is thus trans- formed into a kind of froth, which is often finally displaced so entirely by the cell-sap that it forms merely a layer applied against the primordial utricle. In many zoospores these vacuoles are seen to contract and expand, probably from the varying contractility or degree of turgescence of the surrounding protoplasm. These movements are identical with similar phenomena witnessed in Pro- tozoa, and are the first indications of a respiratory or circulatory system. Movements in the protoplasm, rendered evident by the movement of the granules floating in it, occur in many plants, probably in all, and are attributed by some to contractility of the protoplasm, by others to alter- nate turgescence and emptying of certain portions of the protoplasm. They are strictly analogous to the movements seen in Amoeba and other similar low animal organisms. The protoplasm is said to be chambered when the cell-sap is traversed by several anastomosing plates of protoplasm. Nucleus. In the protoplasm of most young cells, and persistent through life in the parenchymatous structure of some plants, as of the Orchidacese, occurs the globular or lenticular body called the nucleus of the cell, or cytoblast (figs. 547, n, & 548), discovered by Bauer, and first investigated by Kobert Brown. This appears to be a mass of substance identical with protoplasm, and it mostly CONTENTS OF CELLS. 497 presents the appearance of a central cavity or vacuole containing one or more small granules called nucleoli. Fig. 547. Fig. 548. Fig 547. Upper end of a young hair of the stamen of Tradescantia , showing the cells in various stages of development ; n, n, nuclei. Magn. 400 diam. Fig. 548. Cell with a nucleus, from the stem of Orchis mascula. Magn. 400 diam. The nucleus is not usually found in Fungi or Lichens ; and many Algee are likewise unprovided with it. Movements of the Nucleus, &c. The nucleus probably originally occupies the centre of all nascent cells where it exists, the inter- space between it and the primordial utricle being filled up by pro- toplasm. When the vacuolar displacement of the latter by watery cell-sap takes place, the nucleus, if persistent, is usually carried to one side of the cell, and comes into contact with the inner boundary of the primordial utricle. Sometimes, however, it remains sus- pended in the centre of the cell by cords of tough protoplasm, stretched from a layer of protoplasm coating the nucleus to that which lies upon the primordial utricle. The cords of protoplasm radiating from the nucleus are the persistent boundaries of the vacuolar spaces of the " honeycombed " protoplasm. The nucleus itself, according to Hanstein, is dragged out of shape, as it were, 498 PHYSIOLOGY. by the contraction of the protoplasmic threads attached to it, and, moreover, itself undergoes, in some cases, changes of form ana- logous to those manifested by Amcelce. (See under Myocomycetes, p. 471.) The gradual vacuolation of the protoplasm and the transfer of the nu- cleus to the side of the cell may be well seen in the hairs of the stamens of Tradescantia (fig. 547). In Spirogyra and Zygnema the nucleus re- mains always suspended in the middle of the cell by the protoplasmic cords. The ultimately parietal nucleus of the hairs of Tradescantia ex- hibits radiating cords, the protoplasm here being in process o^absorption. In Vallisneria and in CEdogonium and other Confervoids, the nucleus becomes imbedded in the continuous parietal layer of protoplasm which lies upon the primordial utricle. The nucleus has the property of break- ing up and, as it were, disappearing for a time, to reappear in the form of two or more new nuclei of larger size than the original nucleus. This process occurs in the formation of the pollen in the embryo-sac of Phane- rogamous plants, &c. The nucleus is sometimes, according to Cohn, in- vested with a layer of starch, and is coloured by carmine solution, which leaves the amylaceous envelope unstained. Chlorophyll. In all parts of plants which have Fig. 549. a green colour we find the cell containing in its cavity structures quite distinct from the cell-wall and from the primordial utricle, in which the green colouring-matter resides. The ordinary form of these is that of globular or spheroidal corpuscles, which appear in greater number and of darker green colour in proportion to the intensity of solar light to which the tissue may be exposed. In a few cases the green colouring-matter is found in the form of annular or spiral bands (Draparnaldia, Spirogyra, fig. 549), or of reticulated cords (Clado- pJiora), of mucilaginous consistence, adhering to the^inside of the primordial utricle. In some Con- fervse the green colouring-matter appears diffused through a portion of the protoplasm in the form of very minute granules. In many unicellular Algae, in the Algoid gonidia of Lichens, &c., the green colouring-matter is uniformly distributed through- out the cell, and is not separable from the rest of the protoplasm. The Chlorophyll-corpuscles are of soft consistence ; and their colour is extracted bv ether, alcohol, and , . , mi . . - , ' . ' Cells of a filament various acids. I hey consist 01 protoplasmic colour- of Spiropyra, with less substance mixed with colouring-matter. The former may exist by itself unmixed ; but the colour- ing-matter is never found separate in nature. They appear spiral green bands. Magn. 200 diain. CONTENTS OF CELLS. 499 usually solid and homogeneous when young ; subsequently they often contain starch-granules in the interior, and not unfrequently they become vacuolated like protoplasm when exposed to the direct action of water. Fremy states that the green colour of chlorophyll is due to an admixture of two substances, one yellow and the other blue, called respectively phylloxanth ine tmd phyttocyanine ; but others think that the blue substance is a modification of the yellow, brought about by the agency of the acids. Our chemical knowledge of chloro- phyll, however, is at present incomplete. Sorby states that chlo- rophyll exists in a blue and in a yellow state. Blue chlorophyll when dissolved in alcohol, is of a splendid blue-green colour, the whole of the green part of the spectrum and part of the blue being readily transmitted. Yellow chlorophyll absorbs the whole of the blue and the blue end of the green, so that the colour is a bright yellow-green. Chlorofucine is of a clear yellow-green, colour, fluorescent like the two preceding. These three varieties of chloro- phyll are insoluble in water, soluble in absolute alcohol, but not always in carbon-bisulphide. Other colouring-matters, with different optical properties and soluble in carbon bisulphide, are described by Sorby. The chlorophyll-corpuscles are probably formed from the protoplasm of the cell breaking up into distinct globular corpuscles, or distributing itself according to patterns, as above indicated, upon the cell-wall. When newly formed, in young cells, they are almost colourless, and appear in the vicinity of the nucleus and in the layers or streaks of protoplasm ; and we not unfrequently meet with protoplasmic corpuscles which differ from chlorophyll -corpuscles only in the absence of the green colour. Development of Chlorophyll. The development of chlorophyll takes place thus : In the young cell the protoplasm is colourless and disposed in a thick layer around the inner wall of the cell ; in this appears first a yellow colouring-matter ; and then the inner portion of this protoplasm gradually splits up into polygonal portions, eacn of which becomes a grain of chlorophyll. In other cases the chlorophyll is formed in a layer of pro- toplasm surrounding the nucleus. Vacuoles are formed in it, and break up the substance of the protoplasm into granules. In this latter case more uncoloured protoplasm is left after the formation of the chlorophyll than in the preceding case. Decay of Chlorophyll. The destruction or decay of chlorophyll shows itself first in the change of colour from green to yellow or orange, or, in the case of the spores of Algae, to red. This red colour is supposed to be due to oxidation, assumed at the time when the spores come to rest ; when active vegetation again commences, the green colour is restored. In the case of leaves at the fall, the grains of chlorophyll diminish, then disappear and give place to highly refracting granules of an orange colour, which are the remnants of the disorganized chlorophyll, and to which the colour of leaves in autumn is due (see p. 540). While these processes are going on, 2x 2 I 500 PHYSIOLOGY. the starch and the protoplasm are dissolved and stored away in the perma- nent tissues. In plants kept in the dark Gris noticed that the chlorophyll- grains slowly and gradually become smaller, lose their starch and their colour, till at length nothing but a number of minute amorphous granules remains. Some plants, such as Selaginella, some Ferns, &c., resist the deprivation of light much more than others ; but in the case of quickly growing plants, two or three days' obscurity suffice to disorganize the chlorophyll. Action of Reagents on Nitrogenous Contents. The protoplasm, the nu- cleus, and the chlorophyll-granules are all substances containing nitrogen and closely allied to albumen ; they are more or less coagulable by heat, alcohol, and acids, and soluble in caustic potash. The principal tests are the following, though it must be remembered that their action is masked by the colouring-matters of the cell, and that they are not in all cases manifested in living, but only in dead cells : Iodine gives a brown or yellowish tinge to these structures ; ammoniacal solution of carmine tinges them pink. When treated with nitric acid, and subsequently with am- monia, a yellow tint is formed, indicating the presence of xautho-protein ; when soaked in a solution of copper sulphate and afterwards treated with potash, a violet colour is produced in the protoplasm and chlorophyll ; but this has not been observed in the case of the nucleus. It must be remembered that the solubility of protoplasm in acids and alkalies depends not only on the strength of the solvent, but also on the condition of the substance at the time of the experiment. Aleurone exists in many seeds in the form of roundish co- lourless granules pitted on the surface, or even presenting facets like those of crystals. The granules occur between the starch- grains, or, in the case of oily seeds, in large roundish or angular masses. They are, for the most part, about equal in size; but here and there one occurs much larger than the rest, and which is remarkable for the rapidity with which it dissolves in water ; hence it escapes observation under the microscope when the tissues are examined, as they usually are, in water. Aleurone or protein-grains^ as they are sometimes called, are insoluble in ether, alcohol, and oil ; hence, in order to see the aleurone, the following process is adopted : Thin slices of almonds or other seeds are soaked in olive-oil, the oil is subsequently filtered and allowed to stand. Some hours subsequently a white powder is precipitated ; this is removed from the oil by nitration, and washed in ether or alcohol, so as to remove the oil ; it is then allowed to dry, and the resulting powder is pure aleurone. Aleurone -grains often contain, im- bedded within their substance, crystals of calcium oxalate, or glo- bose masses of magnesium phosphate. Aleurone is coloured brown by iodine, and the inner portions of the grain assume a brick-red colour after soaking for some minutes in a solution of mercuric nitrate ; hence it is considered to be of albuminoid nature, and to be of service in providing nutriment for the developing embryo. CONTENTS OF CELLS. 501 The nature, mode of formation, and chemical history of this sub- stance all stand in need of further investigation. Crystalloids. Masses of proteinaceous substance of a crystalline form, but differing chemically from true crystals, occur imbedded in the protoplasm of many plants, especially of such as are in a dormant condition, as beneath the rind of the tuber of the Potato. Their function seems to be to act as a reserve of nourishment to be used when growth becomes active. Similar crystalloids have been seen in many Red Seaweeds. Starch. Starch-granules appear to occur throughout every class of plants except the Fungi, and are perhaps most frequently of globular form when young : but when they acquire any consider- able size their form usually diverges from this, and presents very- remarkable varieties, often attributable to the conditions in which they grow. Full-grown starch-granules are not homogeneous, but marked with striae indicating the concentric laminae of which they are composed. These laminae are alternately of denser and softer consistence, and surround a commonly more or less excentric point, usually of very small size (fig. 550), which often appears solid when the starch-granule is fresh, but which forms a minute cavity, fre- quently running out into a few radiating cracks, when the starch- granules are dry. The granules occur either singly or collected in masses of definite shape, forming compound granules (fig. 551) very often they exist Fig. 550. Fig. 551. Fig. 550. Starch-granules of Potato. Magn. 400 diam. Fig. 551. Compound starch-granules: a, a double granule from the Potato; 6, grouped granules and two fragments from the rhizome of Arum maculatum. Magn. 400 diam. in the interior of chlorophyll-corpuscles or bands, or imbedded in the protoplasm lining the cell-wall. In certain tissues they fill the cavity of the full-grown cell, and in some cases so densely that they become moulded into polygonal forms by mutual pressure. 502 PHYSIOLOGY. Starch-granules are commonly unaffected by cold water; but when crushed, the inner layers will sometimes absorb it and swell up. Boiling water causes them to swell up into a jelly, losing all trace of their laminated structure as do also diluted sulphuric acid and solution of potash. Iodine colours starch-granules violet, indigo-blue, or deep blackish blue, in proportion to the degree of concentration in which it is employed. By means of dilute sulphuric acid, starch may be converted into dextrine and glucose. Modern researches have shown that starch consists of two substances intimately com- bined, one of which, granulose, is more soluble in saliva than the other, cellulose ; and the action of iodine is also different in the two cases. Mode of formation. Great discussion has taken place of late years as to the structure and the mode of development of starch-granules. They are apparently formed of a numher of concentric laminae, which increase in density from within outwards. Their substance is hardly distinguishable from that condition of cellulose where the cell-membrane swells into a gelatinous substance with dilute sulphuric acid, or even sometimes with water, and takes a more or less decided blue colour with iodine alone. With regard to their mode of development, they appear to be formed either by intussusception, as maintained by Na'geli and Sachs, or by the deposition of successive layers of starch-substance, by protoplasm, in the interior of vacuolar cavities formed in the protoplasmic matter of the cell, either while this exists as a colourless mucilaginous matter, or after it has become more highly organized into chlorophyll-corpuscles. Starch- granules, in fact, appear according to this view, to be formed \)\ secretion on the inside of a utricle of protoplasm, exactly in the same way as the cellulose wall of the cell is secreted on the outside of the primordial utricle. Fig. 552. Fig. 553. Fig. 552. Part of a cell of the stem of the White Lily: n, nucleus, surrounded by protoplasm in which starch -granules () are being developed. Magn. 400 diam. Fig. 553. Starch of Maize: a, section of a young cell of the seed, with nascent starch -granules imbi'dded in protoplasm ; b, section of a full-grown cell with the starch-granules in contact and become angular by mutual pressure. Magn. 200 diam. This mode of development is well illustrated in the formation of starch- granules in the cords of protoplasm which have ceased to circulate, in CONTENTS OF CELLS. 503 many herbaceous Monocotyledonous stems, as that of the White Lily (fig. 552), &c., by the appearance of single or several starch-granule's in old chlorophyll-corpuscles, or in the substance of the bands of Spiro- gyra (fig. 549), &c. Still more strikingly is it shown in the development of the starch-granules which ultimately densely fill the outer cells of the endosperm of Maize, where they are at first free from each other, im- bedded in a collection of protoplasm filling the cell (fig. 553, a), and, as they expand, come into contact and almost displace all the protoplasm, which remains only as a reticulation of slender threads (fig. 553, o). A similar reticulation of protoplasm -threads remains on the walls of the cells of the Potato-tuber after its starch-granules are formed. The origin of the compound granules, in pairs, fours, or very many compacted together into a mass, moulded together by mutual pressure on their contiguous surfaces, is readily explicable, since we often find several isolated nascent granules in one chlorophyll- or protoplasm-corpuscle : as the granules increase in size they come into contact, but remain bound together by the mass of protoplasm in which they lie. Such granules (found in the corms of Crocus and Arum (fig. 553, 6), in the Oat, and more or less abundantly in many other Monocotyledonous plants) are mostly simply coherent, so that they may be separated by slight pressure. But it is not uncommon to find twin granules enclosed by external layers common to both (fig. 553, a). Relation to Chlorophyll. Starch-grains are almost universally present in chlorophyll, from which, indeed, they are formed. This opinion differs from that of Mohl, but is supported by the discoveries of Sachs and Gris, the former of whom shows conclusively that the starch is developed from the chlorophyll under the influence of light, especially in the yellow, red, or orange rays : if light be excluded, no starch is formed, what is already formed disappears, but starch is again formed when the chlorophyll is once more subjected to the influence of light. Without chlorophyll no starch is formed ; it may, however, be stored up in cells containing no chlorophyll, but is brought there from the cells in which it is formed. Decay of Starch-grains. Starch is a temporary ingredient of the cell-contents ; it is accumulated during active vegetation, and is abundantly deposited in the tissues of many organs which remain at rest during certain seasons. In the recommencement of growth it is dissolved, in consequence of the formation of diastase (which converts the insoluble starch into soluble dextrine), and the as- similated substance is applied to the formation of permanent structure. Starch-grains are disintegrated or dissolved, when growth is about to take place, in two ways either locally (when the grains present a worm-eaten appearance) or uniformly over the whole surface. Inulin. In certain plants starch-granules are absent in those situations where they are generally abundant, being replaced by a substance of analogous composition, called inuline. This has been found especially in the roots of tubers of the Composite. It is 504 PHYSIOLOGY. not clear whether it occurs dissolved in the cell-sap or in granules mixed with the protoplasm. From solutions it crystallizes in spherical masses of radiating crystals, which may also be seen by dipping the sections of the tissue in alcohol. As it has no special reactions giving distinct colour, like starch, it cannot be detected except by chemical analysis. Fixed Oils. The fixed oils, which occur abundantly in many seeds and fruits, are easily distinguished in the cell-contents on account of their forming isolated globules, merely suspended in the watery cell-sap, which strongly refract light, and can be made to run together into large globules by pressure and by the application of ether. The oil-globules occur mostly in organs prepared for a season of rest, as in the endosperm (Cocoa-nut) or cotyledons (Almond) of seeds, or in the pericarp (Olive) of the higher plants also sometimes in tubers, as in those of Cyperus esculentus. Among the lower plants oil is especially abundant in the resting-spores of the Algae, taking the place of the starch- granules existing during active vegetation. Essential Oils. Essential oils are readily distinguishable when they exist in quantity suspended in the cell-sap, or entirely filling the cell ; sometimes, however, they exist in such small proportions as to be undistinguishable, as is the case in many scented petals. The essential oils are developed, like the fluid colouring-matters, in vacuoles of the protoplasm, resolved in time into one large cell-cavity bounded by the layer of the protoplasm lining the primordial utricle. The oily matters, caoutchouc, resins, &c., are usually found in compound cellular organs, glands, ducts, &c., to be mentioned presently, under the head of Tissues. Sugar, Gum, etc. Sugar, dextrine, gum, and similar substances dissolved in the watery cell-sap are not capable of detection by the microscope, since the quantities in which they exist are too small to alter sufficiently the refractive power of the liquids ; and we have no colour-test for them. The gummy matters of plants (which swell up in cold water and form a slimy mass) are in many cases parts of the cellulose tissues themselves, as is the case in the seed-coat of Linseed, the Quince, &c. , and the gum of Tragacanth, which latter consists of the collenchymotous tissue into which the pith and medullary rays of the stem are gradually converted. They result from the abundant formation of secondary layers in that state of the " cellulose " compound which is intermediate between cell-mem- brane and dextrine, just as the " amyloid " of the secondary layers of the cells of some Lichens is an intermediate condition between cellulose and starch. Sassorine and Arabine are formed in a similar manner, from the disorganization of the cellulose matters ; hence these materials are to be looked on as excrementitious. CONTENTS OF CELLS. 505 Colours of Flowers. The bright colours of the parts of flowers are produced by substances usually dissolved in the watery cell- sap ; sometimes, however, solid corpuscles or utricular structures are found swimming in coloured cell-sap. In young tissues of flowers the colouring-matter may be observed to be formed gradually in the vacuoles of the protoplasm, and, as the cells ex- pand, increasing in quantity until the separate portions coalesce and till the whole cavity of the cell. This is well seen in the coloured hairs of the stamens of Tradescantia. The colouring-matters of flowers admit of being grouped in two series, the cyanic series and the xanthic series, with green as an intermediate colour : thus, starting with greenish blue, the cyanic series passes through blue, blue-violet, violet, violet-red to red ; the xanthic series, on the other hand, passes from green to greenish yellow, yellow, orange-yellow, orange, orange-red to red. The cyanic colours are usually in solution ; the xanthic colours are usually solid. It very rarely happens that the colours of the two series are met with in the same flower ; 'hence, though Dahlias and Roses of almost all hues are now to be seen, a true blue tint has never been seen in either ; and there are numerous illustrations of this fact in gardens. The various tints of colour are produced either by the interposition of colour- less cells between those containing coloured juices or by the superposition of cells with different colouring-matter one over the other. Thus an orange tint would arise from the superposition of yellow cells over red, and so forth. White is produced either by a very dilute coloured solution or by the presence of air in comparatively large quantities in the tissues. The velvety appearance of the petals of many flowers is due to the fact that the epidermal cells are raised in the form of small conical elevations like the pile of velvet, and the play of light thereon gives rise to the appearance above mentioned. RapMdes. The watery fluids traversing the tissues of growing plants, in consequence of the evaporation from the leaves and the continual absorption by the roots, necessarily contain various in- organic salts dissolved in them. Moreover certain organic acids, such as oxalic, malic, tartaric, &c., are always formed in the pro- cesses of vegetable digestion. All these substances and their com- pounds are, for the most part, dissolved in the cell-sap ; but in most of the higher plants we find, in certain cells of the parenchy- matous tissues, crystals of definite composition, either scattered or collected into groups of definite form. These crystals are called raphides (fig. 555). They are common in certain orders of Flower- ing Plants and Fungi, though others seem destitute of them. It is not clear whether the raphides are to be regarded as a secretion or as an excretion that is, as substances useless or noxious to the plant, laid by in an insoluble form. The latter seems more probable, especially as they are usually deposited in tissues of enfeebled vitality. The Poly- gonaceas (for example, the Garden Rhubarb) form abundance of oxalic and other organic acids, and they always contain a quantity of bundles of raphides composed chiefly of calcium oxalate ; in old stems of Cactacea3, 506 PHYSIOLOGY. the substance of the parenchyma is rendered quite gritty to the touch by crystals of calcium oxalate and phosphate (fig. 554 ) ; the Musacege con- tain crystals of calcium sulphate, &c. The large spicular cells of Arauca- ria and of Welwitschia, already referred to, are covered with small crystals. Fte. 554. Fig. 555. Clustered crystals from Acic-ular crystals (raphides) in a cell Cactus. of Polyanthes tuberosa, magnified 400 diam. : a, a single crystal, more magnified. Crystals usually occur free in the cavity of the cell ; but in some plants, especially in the Urticaceae, we find them accumulated on a clavate process, formed of cellulose, developed from the side-wall of the cell : these are called cystolitties. These curious structures are well seen in the subepidermal cells of the leaf of Ficus elastica and other species also in Parietaria, the Mulberry, &c. Other important substances, such as the vegetable alkaloids and the great number of organic acids usually associated with them, exist either dissolved in the cell-sap, intermixed with the protoplasm, or diffused in the solid cell-structures as impregnating or incrusting substances. With regard to these, microscopic investigation has not hitherto afforded any information. Sect. 3. COMBINATIONS OF CELLS. Tissues consist of collections of cells of uniform character com- bined together by apposition or by more or less complete union of their outer surfaces. They are produced by the aggregation and juxtaposition of cells of equal age or degree, originally separate and distinct, or more frequently by cells which are formed by repeated subdivisions of preexisting cells. In the one case the tissue is mul- tiple from the first as to its elementary constituents ; in the other it is, COMBINATIONS OF CELLS. TISSUES. 507 at least relatively, simple, its constituents being the descendants of a small number of cells. The simplest mode of combination of cells is that which is met with in a large number of the Algae of low organization, where the cells are asso- ciated for a time in what are called colonies, tlie members of which are more or less completely independent of each other in physiological respects, but morphologically represent parts of a determinate whole j while ulti- mately they separate, each to lay the foundation of a new colony. Examples of this may be seen in the grouped Desmidiea, like Pedias- trum (tig. 503, B, ), the Diatomea, &c., and in the Palmellece ; to this head is also referable the structure of some of the filamentous Confervoids, Volvocineae (tig. 503, D), and Hydrudictyon. These groups of cells are either held together by simple attachment at certain points of their sur- faces, as in the Desnudieoe, Ilydrodictyon, Uiati,ma (tig. 503, B, c), &c., or by their being enclosed in a gelatinous common envelope (resulting from the expansion or the decay of parent-cell membranes), as in the Volvocineo!) Palmellece, and Nostochinece. Intercellular boundaries. A complete coalescence of the cellu- lar membrane of one cell with that of its neighbour so as to form a homogeneous whole takes place, so that, although the bounding membrane between one cell and another would appear necessarily to be double, each cell having its own proper cell-wall, yet if very young growing tissues be examined where the cell-walls are very thin, the boundary- wall between adjacent cells may be seen to be simple, without any trace of separation. It is only in older thick- walled cells that a line of demarcation becomes obvious, in the form of an intermediate lamella, at one time spoken of as the inter- cellular substance, and supposed to be a distinct substance, but which is now shown to be the result merely of a difference in den- sity or molecular structure of the cell- walls during their thickening. Where the cells, during growth, separate at various points one from another to form intercellular spaces, there the boundary-walls necessarily split to form the spaces in question. !So also where cells originally united become disconnected, as in the pulp of fruits, the partition- walls naturally become separated, though originally the boundary- wall is uniform and homogeneous. Parenchyma. The tissues are distinguished into kinds accord- ing to the form of the cells, the character of the cell-membrane, and the manner in which the cells are connected together. Where the cells are roundish or elliptical, the tissue is called paren- chyma ; and this is called imperfect or perfect accordingly as the consti- tuent cells have interspaces between them or are closely packed so as to leave no intercellular spaces. Where the cells are much elongated, the tissue is called prosenchyma, and the constituent cells are known as fibres. Cartilaginous tissue is known as collenchyma ; and two other kinds are 508 PHYSIOLOGY. characterized by peculiar modes of combination of the cells, viz. felted tissue (tela contexta) and vascular tissue. Imperfect parenchyma (merenchyma) is composed of cells with more or less rounded surfaces connected into a lax tissue, necessarily presenting abundant intercellular passages and spaces. The cells are tolerably uni- form globular or oval (a), or lobed, and connected at few points, leaving wide intercellular passages between them (b) ; in other cases the cells are more or less stellate, and leave large spaces between them (c). The form a is common in all young organs of the higher plants, espe- cially in the rind and the pith (fig. 520), in the p ; ilp of fruits, &c. ; b is very characteristic of the lower stratum of the internal substance of leaves (fig. 522) ; c occurs in the stems and leaf-stalks of aquatic plants, in the pith of Rushes (fig. 524), &c. Perfect parenchyma is composed of cells bounded and united together by plane surfaces ; where the cells are regular polyhedra, of about equal size, the tissue is (a) regular parenchyma ; if the size is unequal and the forms unlike, the tissue becomes (b) irregular parenchyma. Certain modi- fications of regular parenchyma have received distinct names, viz.: (c) prismatic parenchyma, where the cells are 6-sided prisms with pyramidal ends ; (d) muriform parenchyma, where the cells are square or oblong, with the long diameter horizontal, and packed like bricks in a wall ; and (e) tabular parenchyma, where the cells are flattened from above down- wards. The form a is abundant throughout all classes of plants, and is well seen in fully developed pith of Dicotyledons (fig. 526) ; b is even more common in the soft parts of plants (fig. 527) ; c is met with in the her- baceous stems of Monocotyledons, and in the upper part of the diachyma of leaves, also in a woody condition in the testa of various seeds ; d is characteristic of cortical structures, and may be seen in cork, peri derm of Birch, the rind of the rhizome of Tamus &c., also in the medullary rays of Dicotyledons ; e occurs specially in the epidermal cells. Merenchyma and parenchyma in their various modifications run into one another by countless intermediate conditions. Sclerenchyma consists of ordinary cellular tissue, the constituent cells of which become ultimately filled with stratified woody thick- enings. They occur locally, even as individual cells or in groups (sderites\ or even in more or less continuous layers. A familiar illustration occurs in the "grit" of Pears. Their purport is sup- posed to be to protect and support softer tissues. Prosenchyma is composed of cells elongated greatly in one di- rection, and attenuated to a more or less acute point at each end, forming what is called a fibre. These fibres are necessarily united for the most part by their lateral surfaces, and their ends are insi- nuated into the spaces between those lying above and below them. "We distinguish in prosenchyma two modifications (a) woody fibre, composed of spindle-shaped cells of moderate length, and (b) liber or bast cells, composed of very long slender cells which are occasionally slightly branched. COMBINATIONS OF CELLS. TISSUES. 509 Woody fibre is the main constituent of the trunks of Dicotyledons ; its cells are" mostly of rectangular section, and the walls become greatly thickened with age. Liber, the tibrous substance of the bark of Dico- tyledons, a principal constituent in the fibre-vascular bundles of Monoco- tyledons (fig. 521), and of the fibrous husks of fruits, &c., is composed of very long cells, whose membranes are of a peculiar toughness, even when greatly thickened ; their section is commonly roundish (fig. 529) or hexa- gonal. The peculiar tenacity of the vegetable fibres, Flax, Hemp, &c., arises from the forms and mode of union of the liber-cells of which they consist ; the " grain " of wood is likewise determined by the direction of the long axis of the prosenchymatous cells of which it is composed. Conducting cells are long, cylindrical, thin-walled cells, placed one over the other, and not tapering at the ends, and are supposed to be channels for the passage of the nutrient fluid. Collenchyma is a substance formed especially at the points of contact of cells. It is of a cartilaginous or horny texture, its cells becoming greatly thickened by secondary layers of a substance softening or swelling up in water, or on the addition of weak sul- phuric acid. It never becomes lignified. The lamination of the cell-walls is often invisible until after macera- tion ; so that the tissue looks like a mass of homogeneous substance, exca- vated into cavities, or like a collection of cells with abundant intercellular substance. A solution of chromic acid also serves to show the laminated structure ; but if used too strong, it dissolves the intercellular substance. The outer portion is not coloured by Schulze's solution or anilinj but the inner portion next the cell-wall is tinted blue with iodine. This tissue occurs in the rind of many herbaceous plants, as Chenopodiaceae (tigs. 550 & 557), Cucurbita, Nymphcea (tig. 535), and the pith and medul- Fig. 556. Fig. 557. Fig. 556. Transverse section of collenchyma-cells of the stem of Beet: a, thickened cell-wall Magn. 400 diam. Fig. 5-37. Section of the junction of four cells (a) of fig. 556, treated with hydrochloric acid : a, lamina bounding the cavity of the cells ; b, swollen secondary layers ; c, primary membrane. Magn. 400 diam. lary rays of the species of Astragalus (forming " tragacanth ") ; and to the same head may be referred the substance of fleshy endosperms (tig. 558), and also the cartilaginous thallus of the larger Algje. 510 PHYSIOLOGY. \ Telacontevtais composed of elongated cylindrical cells, sometimes called hyplice, united end to end into filaments, and either simple or branched laterally, interwoven irregularly into a kind of felted mass. This tissue occurs in the thallus of Lichens, forming -pig. 558. the internal or medullary sub- stance, also in the thallus of some Algae. The mycelium of the Funiri is likewise com- posed of felted cellular fila- ments forming a free cottony mass (fig. 1 B, p. 8). Vascular Tissue. Vas- cular tissue is formed by the absorption of a portion of the contiguous walls be- tween cells, so that they tecome converted into con- binuous tubes of more or less considerable length. When the constituent cells have spiral-fibrous Secondary th tckeningS, they Section of the cells of the seeds of Sophora japonica : TT P T a, thickened cell-walls; o, cavity of the cells are Usually Ot prOSeilCny- (bounded by a double line). Magn. 400 diam. matous form, and they over- lap each other so that the lines of union are oblique : sometimes these spiroid tubes are distinguished as vessels from those formed of the usually shorter, mostly wider, and more or less flat-ended cells which have pitted walls, and which are called dotted or pitted ducts. The dotted ducts are connected with the spiroids through the scalari- form vessels, but in their extreme forms are very unlike, and are found in very different situations. The vessels, like the cells, may be spiral, annular, reticulated, or scalariform. They also present special forms hereinafter men- tioned. The constituent cells may be long or short ; in the latter case the vessels are sometimes called moniliform. The spiral- fibrous structure often remains when the primary membrane is ab- sorbed at the surface of junction, so that the constituent cells of a vessel are merely separated by a kind of " grating " of bars. Spiral vessels (fig. 559) are found in the youngest and most delicate parts of the plants in which they occur. They are the parts of the woody structure first developed in stems ; they are extensively developed in the ribs of leaf-stalks and leaves, and almost exclusively constitute those of COMBINATIONS OF CELLS. TISSUES. 511 the organs of flowers, as may be seen in petals. In stems and leaf-stalks, especially of fast-growing organs, the constituent cells are often very Fig. 559. \ \ Fig. 569. A, B, C. Spiral vessels from Sambucus Fibulu*. Magn. 400 diam. Fig. 562. Fig. 560, Fig. 561. E^sEEr^ff 51 * 400 diam. 512 PHYSIOLOGY. long and the course of the vessels straight ; in roots, and in concentrated rhizomes and conns, &c., the constituent cells are mostly short and the course of vessels tortuous. The spiral fibre in the interior of these vessels has been considered to be hollow or tubular : but this is not generally regarded as correct. Ultimately they are empty alike of protoplasm and cell-sap, and serve as air-conductors. Annular vessels (tig. 560) are found in situations similar to the last, being generally formed a little later in the same bundles. They are com- monly of greater diameter than true spirals. This is the commonest form of vessel in the Equisetacese. Reticulated vessels (fig. 562) are abundantly developed with the spiral and annular kinds in succulent stems, roots, petioles, &c. They are very important constituents in the fibro-vascular bundles of Monocotyledons generally. They are mostly of rather large diameter ; their cells long in stem-structures, short and irregularly formed in roots and in the inner cortical region of Monocotyledonous stems, where a number of vessels are often anastomosed into a kind of network. Scalariform vessels (fig. 541) are especially characteristic of the woody structures of the Ferns and Lycopodiacese, in which they sometimes occur of very large diameter. Most vessels are cylindrical, and present a more or less circular section ; but the scalariform are prismatic, usually with an hexagonal section. Vessels, when once formed, are usually persistent; but in some water- plants the stem when young is traversed by a single spiral vessel, which disappears as the stem grows older, so that in the adult condition the stem seems wholly cellular with a central lacuna. The pitted or dotted ducts (fig. 536) are characteristic of the wood of Dicotyledons, where they occur either scattered in the prosenchyrna, or forming the principal constituent of the wood. The walls of pitted ducts are not always uniform, this depending in some cases upon the nature of the organs with which they are in contact, whether cells or other ducts, since the pits always correspond on the walls of adjacent organs, and they are ordinarily less numerous and less regular on the walls of prosenchymatous cells than on those of ducts. The pits and their borders (p. 487) are very generally somewhat elon- gated obliquely ; and the canal of the pit is often enlarged into a trans- verse slit in the inner part, which in some cases becomes confluent with that of its neighbours. In some plants we find ducts with the wall marked both with pits and a spiral fibre, like the walls of the wood-cells of Taxus (fig. 542). Pitted ducts with uniform walls make up the chief mass of the wood of Clematis. In the wood of Elder, Beech, Hazel, Alder, &c. we find ducts with pits numerous on the walls adjoining other ducts, but distant or absent on the walls adjoining wood-cells. In Bombax the wood-cells are for the most part replaced by parenchyma-cells, and the walls of ducts adjoining these have the pits destitute of the border &c. Pitted ducts form the large tubes, visible to the naked eye, seen in cross sections of most woods, especially Oak, Mahogany, &c. They are absent from the wood of the Coniferse, which is wholly composed of simple wood-cells (fig. 537). Vasa propria are elongated cells with thin walls, and either obh'que COMBINATIONS OF CELLS. VESSELS. 513 Fig. 563. or flat ends, where" they adhere together; they vary in diameter, like the spiroids, and sometimes present on their walls large pits or spaces, covered with a kind of line network of fibres, as in the clathrate cells described in a former section. Ceils of this character (which differ from the conducting-cells before alluded to, in that the latter are destitute of markings or pits) always occur in the middle of the fibre-vascular bundles of Monocotyledons ; and they are intermixed, mostly in alternate layers, with the liber in the fibrous layer of the bark of Dicotyledons. They are strikingly distinguished from spi- roids by containing thick and opake sap, while the latter usually contain only air when fully developed. Casparv includes under the head of conducting-cells not only those cylindrical tubes before alluded to, but also elongated cells having the form and appearance of vessels, but which do not form continuous tubes, being separated one from the other by partitions formed by the adjacent ends of the cells. Laticiferous vessels, or milk-vessels, containing the latex or milky juice of such plants as Poppies, Euphorbias, Cichoraceee, &c., are formed from series of cells, the parti- tions between which become very early and speedily obliterated. The constituent cells may be placed one over the other to form ultimately a straight tube, or, more generally, the lateral partition-walls between the cells become obliterated, and the result is a branch- ing tube, or series of tubes, which, according to Trecul, anastomose with other kinds of vessels, and allow the contents of the one to pass into the cavity of the other. They occur most abundantly in the pith and inner layers of the bark, in roots, leaf-stalks, &c., often forming a complete network. Dippel says the laticiferous vessels replace the clathrate or latticed vessels of other plants. Their presence is most easily demonstrated by boil- ing a fragment of tissue in weak solution of potash. Vesicular vessels (Hanstein) resemble simple unbranched laticiferous vessels, containing a milky juice. They are formed of rows of cells Disposed lengthwise, and their partition-walls are thickened and perforated as in the sieve Lati^iferous canals from the root cells (see p. 487). This form of vessel occurs in of Dandellon ' Maga ' 10 diam ' the bulbs of Onions and other Monocotyledons. In Oommelynaceue and in Pandanaceae long rows of cells are met with filled with raphides, and ultimately forming continuous tubes, which are stated by Hanstein to be homologous with latex-tubes. Tyloses. In some instances, as in the Vine, vesicular formations may be seen in the interior of the large vessels. According to Von Mohi, they are produced by a protrusion of the adjacent cell, which penetrates -- L 514 PHYSIOLOGY. the pore, and either tears through or causes the absorption of the primary membrane of the vessel. The Systems are combinations of tissues, of like or different form and character, into elementary structures formed on definite plans, and destined for particular purposes in the economy of the plant. In the simpler plants there generally exists no distinction of systems ; but even in the higher AlgsB and Lichens there is a dif- ference in the cortical and medullary portions of the thallus. In plants possessing stems and leaves, the nbro-vascular or wood- system makes its appearance ; and we may distinguish in the Phanerogamia three primary systems, viz. the Cellular, the Mbro- vascular, and Cortical Systems. These are all formed of proper constituent cells or tissues. Besides these, we have systems which are formed for the most part by the interspaces between the cells of the above tissues, viz. the Aerial System, consisting of intercellular passages, spaces, or even large cavities ; and the Secretory System, including the milk- vessels, reservoirs for secretion, glands, &c. The Cellular System. This name is applied to the cellular tissues forming the great mass of the living structure of plants. In the Thallophytes it forms the whole organization, the super- ficial layer of the larger kinds of thallus not being a true cortical layer like that of the higher plants. In the Mosses and Hepaticse little is added to the cellular system, the fibro -vascular system appearing in a very simple form in the stems, and the cortical in the shape of an epidermis to the seta. In the higher Cryptogamia and the Phanerogamia the cellular system is less predominant, except in the temporary organs. In the stems and roots it forms the pith and medullary rays of Dicotyledons, and the diffused medullary system of Monocotyledons, together with the cambial structures in all growing regions ; and it forms the mass of the leaves and the parts of the flower. It is in this system that the vital processes of vegetation are chiefly carried on. If the con- stituent cells do not grow or divide, they constitute a permanent tissue ; but if the cells divide, they form meristern, or generating tissue. Meristem. That part of the parenchyma, or cellular tissue, whose constituent cells multiply, or are capable of multiplying, by division, as subsequently explained, is called meristem. According to Hanstein's researches on the development of the tissues in the embryo plant, the meristem or growing cellular tissue, in the course of its development, gradually undergoes changes which result in the formation of distinct layers of cells differing in size, form, and mode FIBBO-VASCULAB, SYSTEM. 515 of division, and which may be grouped under the three heads of dermatogen, periblem, and plerome. JFrom the dermatogen-celis the root-cap, the epidermal tissues and their appendages, hairs, &c., develop themselves. The cells constituting the periblem are the precursors of the cortical tissues. The cells of the plerome form the pericambium, procambium, cambium, and ultimately the fibro- vascular bundles and pith. The pericambium is only found in roots, and is merely the outer layer of the plerome (McNab). The procambial cells are those which are destined to develop into the libro-vascular bundles. The cambium is that portion of the original plerome which is not converted into fibres or vessels, but the cells of which retain their more or less spherical form and their power of subdivision. The cambial cells occupy the centre of the fibro- vascular bundles of Dicotyledons, between the outer phloem portions and the inner xylem or vascular portions. At the extreme apex these layers are not yet differentiated, but form a mass of cells of equal size and degree, sometimes called the initial cells. In many Cryptogams, however, the ends of the stem and of its subdivisions are constituted by a single apical cell. The Fibro-vascular System. This system forms all the woody structures of plants, which in all cases are composed of a quantity of conjoined portions of cellular and vascular tissue arranged in a peculiar manner, and derived originally from a definite portion of the plerome called the procambium. The cells of this latter are either all converted into permanent tissue (vessels, liber-cells, &c.), or some of them remain in a merismatic condition, if capable of division, and these form the cambium. The kind of cellular tissue associated with the vessels is mostly prosenctiyma or fibrous tissue ; the constituent elements wood of are called jibro-vascular bundles. In Dicotyledons the fibro-vascular bundle usually con- sists of wood-cells and vessels (xylem) internally, liber-cells (phloem) externally, separated by cambium. The bundles are plunged in paren- chyma. If the bundles are devoid of meristem or cambium they are closed ; if, on the other hand, they contain cambium, the bundles are called open. All woody substance appears originally in the con- dition of isolated fibro-vascular bundles, which, when they remain separate, form what are commonly called " fibres," and when they combine together into a solid mass, form " wood." The bundles re- main as " fibres" in the stems of Monocotyledons ; they are in the same state in the earliest conditions of the stems of Dicotyledons ; and such " fibres " form the ribs of leaves and other organs. That portion of the parenchyma which remains after the con- version of the meristem into fibro-vascular tissue is called the fundamental tissue. 2L2 516 PHYSIOLOGY. Fig. 564. The fibre-vascular bundles differ in their mode of growth in different Classes of Plants, which, in consequence of this, exhibit considerable difference in the structure of their mature stems. The simplest form is absolutely without vessels, as in Mosses and some simple aquatic Phanerogamia (Potamogetori), where the fibro- vascular tissue is composed simply of cords of prosenchyma traversing the cellular tissue. Complete bundles, however, possess several elements arranged in definite order ; these belong to the wood-region, the cambium- region, and the liber-region. The wood-region, which lies next the centre of the stem, is composed of short-celled prosenchyma inter- mingled with spiral and other vessels (and in Dicotyledons pitted ducts) ; the cambium-region is composed of prosenchyma in a nascent condition. The increase of such stems depends on the development of new cells in this region. The liber-region is composed of very long pro- senchymatous tissue (usually in the condition of isolated bundles of thin laminae con- nected by cellular tissue in the Dicotyledons). In the Monocotyledons the region is converted into vasa propria (fig. 564). In the Higher Crypt ogamia there is no dermatogen, but only periblem surrounding the plerorne ; the bundles are closed, t and do not alter in their con- r dition when once formed, and they anastomose with those that succeed them in succes- sive internodes of the stem, so that the fibro-vascular structure appears continuous. In the Monocotyledons there is but little periblem ; the bundles are also closed, are formed by degrees, a cam- bium-region being formed from the plerome and occupying the central part at first ; but after a time this is wholly resolved into wood, liber, and vasa propria. Monocotyledonous fibro- vascular bundle (from the spadix of Phoenix dactylifera). A. Transverse section. B. Vertical section : , parenchyma in which the bundles lie ; w, wood-cells ; s v, spiral vessels; d, reticulated ducts (from w to d are included in the woody portion of the bundle or xylein) ; v p, vasa propria ; I, liber-cells (from v p to I are included in the phloem or liber part 01 the bundle). Magn. 100 diam. These bundles remain isolated CORTICAL SYSTEM. EPIDERMIS. 517 in the stem, never alter in condition after the first season of growth, and turn outwards to terminate at the surface of the stem above and below, anastomosing with their successors. In the Dicotyledons the bundles in a young shoot somewhat resemble those of Monocotyledons, but they stand in a regular ring round the pith. On the inside they present spiral and annular vessels ; next, a mass of prosenchyma with dotted ducts, which passes gradually into the cambium-layer; the latter is bounded externally by liber, among the bundles of which are v asa propria. These bundles are indefinite in their growth, producing new layers of permanent tissue, liber-cells on one side of the cambium and wood-cells on the other. Hence the division of the bundle into phloem or bast tissues, and xylem or wood, separated by the cam- bium when present. The phloem consists of thin-walled, often latticed cells, sieve tubes, and of large thick-walled liber-cells. The xylem consists of thick-walled cells and pitted vessels, surrounded by woody parenchymatous cells. Sometimes the cells do not be- come woody. Great variations occur in the degree in which the several elements are present, even at different parts of the same bundle. The lower extremities elongate indefinitely in the root ; the upper extremities anastomose and become continuous with their successors ; and above all, the cambium-region is ' an indefinite focus of development, forming a new layer of woody substance inside, and a new layer of liber outside during every season of growth. Protecting Sheath. This term is applied by Caspary to a single layer of cells without intercellular spaces surrounding each fibro- vascular bundle, or surrounding the entire ring of bundles. By Van Tieghem this layer is called the endoderm. Its cells are usually more or less lignified. The Cortical System. Epidermis. In young stems and in her- baceous organs generally this system is termed the epidermal system ; as stems grow older, this gives place to the bark. The cortical system may therefore be defined as comprising all the tissues outside the cambium ring when present. The simplest form in which the cortical system exists is that of a simple layer of flat cells firmly united by their sides, forming a continuous coat over the surface of a plant, called the epidermis. The constituent cells of the epidermis do not divide tangentially, but always parallel to the surface. These cells, moreover, are entirely devoid of chlorophyll or granular matter, and are derived from the dermatogen cells. The epidermis is usually caducous, being succeeded by the formation of corky periderm cells. Where the stem remains green the periderm is not formed, but the epi- 518 PHYSIOLOGY. dermis persists. Such an epidermis clothes all the organs of plants above the Class of Mosses ; and it presents this simple general character on all young structures, with one special distinction only, that on submerged organs and on roots it is absolutely con- tinuous and impervious ; while on parts exposed to the air it pre- sents more or less numerous orifices guarded by a peculiar cellular structure called a stoma (fig. 565, a). Stomata. The stomata are orifices between the meeting angles of the epidermal cells (fig. 566, B), in which orifices lie, rather to the underside, a pair of cells of semilunar form (fig. 566, A, C), separate on their adjacent sides, so that in expansion and contrac- tion they close and open a slit-like passage beneath the superficial orifice. This slit (fig. 566, A, s) leads to an open intercellular space within the substance of the leaf. Fig. 566. Fig. 565. Fig. 565. Epidermis of the lower surface of the leaf of Helleborus foetidus; a, stoma, Magn. 200 diam. Fig. 566, Stomata of the leaf of Narcissus Pseudo-Narcissus. A. Vertical section of the epi- dermal and subjacent cells, passing through a stoma, s: c, cuticular pellicle ex- tending down into the stomatal cavity. B & C. Horizontal section of the epi- dermis, passing through the plane of x in A : B, seen from above ; C, seen from below ; d, smaller epidermal cells corresponding in position to the stomata, but remaining in their original condition. Magn. 200 diam. In Neriurn the stomata are on the walls of pits or depressions on the under face of the leaf. Sometimes the stoma is formed of four cells, and CORTICAL SYSTEM. - STOMATA. 519 then either in two pairs, as in Ficus elastica, or the four cells form the quadrants of a circle, as in various Proteaceae. Stomata are most abundant usually on the lower surface of leaves, often wanting on the upper surface except on the floating leaves of aquatic plants, where they exist on the upper surface, and are absent where the leaf touches the water. They are occasionally found in the interior of organs, as on the replum of Crucifers. They vary in frequency, partly "bearing proportion to the size of the cells of the epidermis, partly irrela- tive to this. Sometimes 100 will be found in a square line, sometimes as many as 1000 to 3000. On the leaf of Brassica Rapa a square line bears 1800 on the upper face, 3500 on the lower ; Victoria reyia 1800 on a square line above, and none below. A few other examples may be cited. On the lower face. Cherry-Laurel .............. None. 625 to a square line. Laurustinus ................ do. 625 Daphne Mezereum ............ do. 30 ,, Carnation .................. 250 250 Garden Flag ................ 80 80 Garden Rhubarb ............ 7 30 Lilac ...................... None. 1000 From the researches of Duchartre, Morren, and others, the following conclusions may be drawn, subject, however, to many exceptions. Sto- mata are more abundant in woody than in herbaceous plants, in leathery leaves rather than in those of thinner texture. Succulent leaves contain the smallest numbers of stomata. Where leaves are alike in texture and colour on both surfaces, the number of stomata is about equal on both sides ; when one side is glossy and the other dull, the stomata are most abundant on the latter, &c. Form of Epidermal Cells. The cells of the epidermis exhibit a great variety of forms in the leaves and petals of Phanerogamia. It is very common for the side-walls, by which they adjoin, to be sinuous or zig- zagged, often presenting very elegant patterns (fig. 565), especially on petals. The external wall of the cells is usually more or less convex ; and in petals this condition is carried further, through numerous grada- tions, until we find a papillose condition, arising from each epidermal cell being produced above into a little obtuse cone. Hairs ; Trichomes. Hairs and scales of all kinds, " scurf," such as we see in the Bromeliacese &c., depend on the development of the epidermal cells. Simple hairs are merely single epidermal cells produced into a tubular filament ; cell-multiplication usually occurs in such hairs, so that they present a number of joints (fig. 567, b) ; and not unfrequently they are more or less branched (fig. 567, c, cl). Glandular hairs differ merely in certain of their cells secreting oils or resins in their cavities (fig. 567, /.) Scales are produced by epidermal cells growing out into flat cellular plates instead of projecting filaments. Thorns, such as those of the Hose, the prickles of leaves, like those of the Holly, &c., are epi- 520 PHYSIOLOGY. dermal products in which the cells become thickened by woody secondary deposits. Fig. 567. Epidermal appendages : a, gland of Fraxinella, in vertical section ; b, simple jointed hair of Pelargonium ; c, hair of Sisymbrium Sophia ; d, hair of garden Chrysan- themum; e, hair of a Grevillea; f, hair of the bulbil of Achimenes, with a glan- dular terminal cell. All magn. 50 diam. Thickening layers of Epiderm-cells. The most remarkable diversities of condition of texture of herbaceous organs depend on the consistence which the epidermal layer acquires. The leathery- texture of evergreens, the woody character of the leaves of Coni- fers, &c. depend chiefly on thickening of the wall of the epidermal cells. In all epidermis exposed to the air, the outer walls of the cells Fig. 568. Fig. 569. Fig. 568. Vertical section of epidermal cells of the leaf of Hoy a carnosa : a, the portion of the secondary layer coloured yellow by iodine. Maga. 440 diam. Fig. 569. Section as in fig. 568, treated with caustic potash : a, detached cuticular pellicle ; b, the layers of thickening of the outer walls of the cells. Magn. 440 diam. become early strengthened by secondary thickening; these are very thin and slight in soft herbaceous leaves, especially when such plants are reared in a warm, moist atmosphere. In leathery or hard leaves, also in the thick tough leaves of succulent plants, such as the Aloes, Hoya (figs. 568 & 569), &c., the secondary layers acquire great thickness ; and in the epidermis of the branches of Viscum (fig. 570) the cells become absolutely filled up, and the cells of the subjacent layer of tissue also suffer the same change. In the course of this thickening, the superficial laminae, exposed to"_the COETICAL SYSTEM. CUTICLE. 521 Ficr. 570. air, become more or less. chemically changed, and at the same time fused, as it were, into a continuous layer all over the surface of the organ ; and by maceration, or applying nitric acid, we may separate this outer stratum as a con- tinuous sheet or pellicle. This layer, which strongly resists decomposition, is called the cuticle (figs. 569 & 571, a), and is constituted by the altered outer walls of the cells. It is usually blended with waxy material, which sometimes exudes in the form of "bloom," as on the sur- face of some fruits and leaves. Unlike cellulose, cuticular structures are dissolved in caustic potash, but not by sulphuric acid. Iodine and sulphuric acid stain them yellow. These characteris- tics are similar to those pos- sessed by cork. Anilin and sulphuric acid, according to Wiesner, do not stain them as they do vasculose. In Cycas the inner laminae of the secondary deposits exhibit pits like those found on the walls of wood-cells ; but this is a very rare phe- nomenon. The aerial roots of Orchi- daceae exhibit a curious struc- ture, the growing extremities being clothed by a whitish cellular tissue composed of several layers of cells with a delicate spiral fibrous deposit on their walls. - layer forms a kind of coat over the real epidermis of the root, and Vertical section of epidermal cells of old stem of Viscum album. Magn. 400 diam. Fig. 571. Vertical section of epidermal cells of ILelleborus foetidus: a, cuticle. Magn. 440 diam. This is known by the name of the velamen radicum. Hypoderm. In some cases, beneath the layers of epidermal cells are layers of wood-cells (sclerencJiyma} or of elongated thick-walled cells, like liber-cells. These serve to strengthen the epidermis, and are called hypodennal cells. They originate from the plerome. Cork. The young shoots of Dicotyledonous trees and shrubs are clothed with epidermis like herbaceous plants ; but before the close of the first season of growth, in most cases, the green colour gives place to brown, which is owing to the formation of a layer 522 PHYSIOLOGY. of cork from the outer layers of cortical parenchyma. The surface of the corky layer is usually rough and irregular, and it peels off in laminae periodically in certain plants, being renewed by deve- lopment from the green cellular layer which it covers. In some plants the corky layer is little developed, in others very much, as in the Cork-Oak. In the Vine and Clematis the corky layer is scarcely distinguishable after the first year's growth, as the bark breaks away, down to the liber, in stringy shreds. In Viscum no cork occurs ; even in shoots eight or nine years old the epidermis remains, but completely consolidated by secondary deposits, as noticed above. Cork is composed of tabular thin-walled cells, containing only air, closely arranged in rows at right angles to the surface. The surface of wounds in soft-growing tissue is usually covered with a layer or layers of cork-cells, which form a sort of defence to the wounded tissues. In chemical and physical properties, cork closely resembles the cuticular substances just mentioned. Cork-cells are formed from a special set of cells constituting the cork-cambium or phellogen. The cells divide hori- zontally or parallel to the surface, but always in such a manner, that of two newly-formed cells one remains full of protoplasm, with chlorophyll contents &c., while the other is transformed into a permanent cork-cell. The formation of cork, however, varies in different cases, and is sometimes of a very complex character. According to Sanio, Rauwenhoff, and Vesque, the growing cork-cells grow on the outer or on the inner side of the phellogen or cork-cambium, the formation being centrifugal in the former instance, centripetal in the latter. In other cases the growing cork-cells are placed on both sides of the phellogen. But in this latter case it is only the outermost cells of each layer of the phellogen which become truly corky ; the inner cells in both cases retain their cellulose charac- teristics, and become filled with chlorophyll, forming an herbaceous envelope. Vesque has proposed that the term periderm be applied to the whole of the cork-cells produced by the phellogen ; some of these cells, as above described, become suberified, or converted into passive cork-cells, while others retain their active character and constitute the herbaceous envelope. The periderm layers occur, not only singly, but in separate groups at different depths in the bark, causing the exfoliation of plates or rings of bark, to which the.name rhytidome has been given by Von Mohl and Hanstein. Lenticels are small local formations of cork-cells occurring on young shoots in the form of little warts. The cork-cells are formed beneath portions of the tissues which are decaying or dead, and which surround the cavities beneath the stomata. Similar formations are consequent upon the formation of cracks in the epiderm, the object being, in both cases, to afford protection to the denuded tissues (Trecul). Liber. Every fully developed fibro-vascular bundle consists, as above said, of liber, cambium or generating tissue, and wood encircled by cellular tissue. The liber (phloem) part of the bundle is distinguished from the woody (xylem) part of the bundle by its position outside the cambium, by the larger size of its woody fibres, their different chemical properties, and especially by the presence of latticed or sieve cells, &c. Ihe unlignified liber-cells (called also soft bast cells) contain albuminoid materials, proto- THE AERIAL AND SECRETORY SYSTEMS. 523 plasm, &c., for the nutrition of the plant, and their walls have a cellulose reaction, become blue, not yellow, by addition of iodine and sulphuric acid, &c. The ordinary position of the liber has been above stated, but it may also occur in the interior of the bundles, in the medullary sheath (see Anatomy of Stems), even in the midst of the wood. The liber, once formed, may cease to grow, or it may retain more or fewer cells still endowed with the property of dividiDg. The Aerial System. In most parenchymatous tissues of the higher plants we find the cells so disposed as to leave passages of greater or less capacity between them, which passages are usually found filled with air, apparently secreted from the contents of the cells. In imperfect parenchyma (fig. 521) these intercellular passages occupy a very considerable portion of the space filled by the tissue, and they intercommunicate in all directions. The spongiform cellular substance of leaves is traversed by large passages of this kind (fig. 585), expanded in many places into air-spaces, forming a continuous system of cavities, which are in direct communication with the external air by the stomata. When stellate cellular tissue exists (fig. 521), the air-spaces are very extensively developed. No intercellular passages or spaces exist in young tissues ; they are subsequently formed by the cells separating from, each other as they expand, and excreting air into the interspaces. Air-canals are long tubular channels, in petioles (Nymphae- aceaa) or steins (Hippuris, Potamogeton, &c.), bounded by a cellular wall, and generally arranged in a definite manner in the organs in which they occur. They are sometimes continuous through long tracts of the stems or petioles (NymphseaceaB), or they are sub- divided into chambers by cellular diaphragms occurring at intervals (petioles of Musa, stem of Hippuris, Myriophyllum, &c.). Lacunas are formed by this cellular tissue being torn down and destroyed by expansion of the surrounding tissue ; examples of this occur in the fistular stems of TJmbelliferse, which when young have a solid pith ; but this is torn away by the expansion of the cylinder of fibro-vascular bundles, and leaves a tubular cavity. The hollow stems of Grasses, of Equisetaceae, &c., originate in the same way. Secretory System. The structures in which are found the substances usually called the secretions of plants consist of latici- ferous vessels (see ante, p. 513), glands, reservoirs and canals for peculiar secretions (resins, oils, &c.), and the so-called milk-vessels. They for the most part occur only in particular plants or particular organs, and present many special modifications in different Natural Orders, occurring on the surface or infche interior as single cells or in groups, or as simple or branched tubes, or in layers, but, how- 524 PHYSIOLOGY. ever different in appearance, always forming and storing or con- veying hydro-carbonaceous secretions. Glands are the structures of this kind most frequently met with, and they are generally connected in some manner with the epider- mal tissue. Glands may be divided into simple and compound, and also into external and internal. Simple external glands are in most cases glandular hairs ; i. e. the ter- minal cell (or cells) of a jointed hair is expanded or filled with oil or other secretion. Of this nature are the glands of the foliage, flowers, &c. of many Labiatae, Scrophulariaceae (fig. 567, /), &c. Simple internal glands are mostly isolated cells of the layer imme- diately subjacent to the epidermis, as in the leaves of Beyoma, Lysi- machia vulgaris, the petals of Mac/nolia, &c. Such glands occur also in the leaves of Lauraceae. The cystolithes of Urticaceae are related to these (p. 506). Compound external glands are sometimes hair-like growths from the epidermis, or from the deeper tissues, from whicji they form outgrowths (Droserd). The summit or the base (Dictamnus, fig. 567, a) is sometimes developed into a cellular nodule, the cells of which either contain the secretion or surround a large central cell filled with it. Other superficial glands form papillae of various shapes, in like manner either wholly formed of secreting cells, or with a central reservoir, as in the Hop, Begoniaceae, Rosaceae, Leguminosae, &c. Compound internal glands are commonly reser- Fig. 572. voirs surrounded by a special layer of cells, lying just beneath or sometimes rising in a dome shape a little above the surface of the epidermis. Ex- amples of this occur in the leaves of Ruta (fig. 572), rind of the fruit of Oranges, Lemons, c., leaves and stems of Hypericaceae, Myrtaceae, &c. None of these glands have excretory ducts like the "lands of animals. In many cases the secre- tions exude through the membrane, and give a peculiar character to the surface of the organs in O f R U t a which they are found. A very general form of Magn. 50 diam, secretion of this kind is the exudation of saccharine fluid from the superficial cells, very common at the base of petals and ovaries, on the stigma, and sometimes on leaves or at particular points of the lower surface of the leaves, as of Prunus Laurocerasus, the^ Laurus- tinus, and other shrubs. (For fuller information on these subjects, the memoirs of Trecul, Van Tieghem, and Martinet should be consulted.) Stings are a form of glands, consisting of a long, stiff and pointed hair expanded into a bulb at the base containing the poison. This bulb is surrounded by a layer of cells derived from the epidermis, which by their tension exert a certain pressure, whence ifc results that when the point of the stinging-hair is broken off, the fluid is pressed out from the orifice. Reservoirs for peculiar secretions may b$ regarded as a highly developed form of the internal glands. They consist of tubes INTERNAL ANATOMY OF ORGANS. STEMS. 525 without any proper lining- wall, but surrounded by thin -walled cells tilled with resin and other secretions more or less devoid of oxygen, and which are poured into the cavity lying in the midst of the parenchyma, or in the liber and wood, parallel with the fibro-vascular structures. Similar reservoirs exist in the roots of Rhubarb, in the leaves of Aloes., &c., in varying positions. The cells which bound the cavities sometimes grow and project into them, more or less filling them up. Sect. 4. INTERNAL ANATOMY OF ORGANS. All young plants are composed of cellular tissue alone ; and the Thallophytes never acquire any of the more highly developed " systems " which we meet with in full-grown Flowering Plants and the higher Cryptogamia. In the stems of the latter, the " systems " present special modes of arrangement, respectively characteristic of the great Classes. In embryo plants the tissues have, according to Hanstein, a three-fold origin in dermatogea, periblem, and plerome (see ante, p. 515); and these three layers are distinguishable before even the formation of the cotyledons. Famintzin considers them identical with the embryonic layers of the animal. The more or less uniform condition of the tissues in the Thallophytes is connected with great simplicity in the physiological processes of vegeta- tion and growth ; while in the higher plants the difference of internal organization is accompanied by important differences in the modes of development of the axis. It would cause us to exceed our limits very widely to enter into minute details of the internal structure of the organs of vegetation of plants generally ; but it is requisite not only to give a general sketch of the plan of organization, but to describe some of the more important modifications met with in the higher Classes. Structure of Stems. As a general rule, plants possessing stems and leaves exhibit in their stems a definitely arranged fibro-vas- cular system, the bundles of which send off branches, or pass off themselves entirely, to form the ribs and veins of the leaves. The young stem is made up of wood-cells and vessels, placed the one within the other, superposed in rays and surrounded by connecting cellular tissue. The same axial system furnishes below, directly or indirectly, the bundles which constitute the woody central mass of roots, in which originally the liber and the vessels are placed side by side. Mosses. The simplest form of the fibro-vascular system is seen in the Mosses (p. 431), where a cord of prosenchymatous tissue runs up the centre of the thread-like stern, and in some cases sends off branches to the leaves. Lycopodiaceee. In the Lycopodiacese (p. 423) the axis of the stem is occupied by one or more parallel fibro-vascular bundles, containing spiral 526 PHYSIOLOGY. and scalariform vessels, surrounded by parenchyma. The bundles are regularly developed onwards with the growth of the point of the stem, sending off lateral branches of spiral vessels where leaves arise, but undergoing no change after the internode in which it lies is once formed. Equisetaceae. In the Equisetacere (p. 417) a ring of isolated fibro- vascular bundles exists in the periphery of the aerial stem, surrounded by liber-cells and parenchyma ; these, again, are closed bundles, and grow only at their points as the stem elongates. The constituent vessels are spiral or annular. The epiderm, and specially its hypoderni, fibres are highly developed. The Equisetaceae are the only plants known whose buds originate, deep in the substance of the stem. Filices. In the Ferns (p. 419), where the stem acquires greater di- mensions, we find a number of fibro-vascular bundles standing in an ir- regular circle, surrounding a central cellular axis, and externally sur- rounded by a kind of rind (liber) containing sieve tubes. The bundles do not run straight up the stem, but in waved curves ; and they anastomose laterally and separate again, leaving wide passages of communication between the central parenchyma and the rind (fig. 573). The branches of the bundles going to supply the leaves are given ofi'at the anastomoses of the main bundles ; and the bundles running into the (adventitious) roots arise at similar places. The bundles of the stem have only indirect connexion with those that pass to the leaves, so that in leafless parts of the stem the arrangement is the same as where there are leaves present. These bundles are closed, and therefore the stems never alter in dimensions when once formed. In cases like that of Angiopteris evecta, w^here the stem is reduced to very small proportions, there are, according to Mettenius, three zones of fibro-vascular bundles, one within the other, and connected by intervening net-like bundles. It was formerly supposed that vessels of the scalariform type were the only ones that occurred in Ferns ; but it is now well known that spiral and annular vessels also occur, especially in the younger portions. All the above forms of the stem are characterized by having their fibro-vascular bundles when complete destitute of cambium, hence called closed (p. 515). They are developed only at the point. From this circumstance, these higher Cryptogarnia are often called Acrogens, or Acrobrya (point-growers). Monocotyledons. The stems of Monocotyledonous plants have a very different organization from the above. The most striking peculiarity, at first sight, is the isolation of the fibro-vascular bundles, which, as a rule, anastomose but slightly in any part of their course through the stem, and are scattered singly in the parenchyma of the stem (fig. 574). Another important circumstance is, that they pass entirely into the leaves at their upper ends (fig. 575, a), while at their lower extremities they approach the surface of the stem and anastomose with their fellows to form a more or less developed fibrous network, separating the rind or cortical paren- chyma from the central fibrous part of the stem. It is from this network that the fibro-vascular axes of the (adventitious) roots are derived (fig. 575, 6). The stems of Monocotyledons are very generally herbaceous, and thus present very important varieties of form, arising from non-development of INTERNAL ANATOMY OF ORGANS. STEMS. 527 internodes, according to regular plans. These modifications disguise the structure ; but it may be readily understood by means of diagrammatic illustrations of some of the principal forms. Fig. 573. Fig. 575. Fig. 574. Fig. 573. Diagram of the arrangement of the fibro-vascular bundles in the stem of a Tree-fern. Fig. 574. Diagram representing the arrangement of the fibro-vascular bundles in a Palm-stem. Fig. 575. Another diagram, representing the upper (a) and lower (6) extremities of a Monocotyledonous trunk, with its fibrous layer, where the stem-bundles terminate and those of the root commence, enclosed by a cortical layer. The fibro-vascular bundles of Monocotyledons (fig. 576) being of the definite or closed kind (p. 515), they acquire their full development in each internode before the leaves to which they belong fall ; and hence the stems of this class do not increase in diameter as a general rule, but have a columnar character when they form woody trunks. But there are ex- ceptions to this rule. It has just been stated that the fibro-vascular bundles terminate below, near the periphery of the stem, and there form a more or less evident net- work of fibres ; this network constitutes a kind of sheath round the gene- ral mass of the stem, and is itself covered by a more or less developed rind or cortical parenchyma (fig. 575, &). The tissue in the region of the fibro-vascular network, or fibrous layer, remains in most cases in the con- dition of cambium, as we see adventitious roots readily formed in this situation. In Dractsna. Yucca, and some other woody Monocotyledons the stem becomes increased in thickness with the age of the tree, by the formation of layers of liber-like prosenchyma in this fibrous layer pushing 528 PHYSIOLOGY. the rind outward. The original central fibro-vascular system of the stem remains unaltered. The region, at the junction of the central and cortical paren- chymas, where the fibro-vascular bundles terminate should per- haps be called a oxm&um-region. since the cellular tissue situated here retains its developmental power in many cases. The es- sential difference between this and the cambium-ring of Dico- tyledons depends on the fact of its not coinciding, in a parallel arrangement, with the cambium- region of the tibro-vascular bun- dles, but with the extremities of the bundles, which always re- main isolated from each other. The successive layers of fibrous structure in Draccena &c. are formed in like manner of isolated bundles imbedded in parenchy- ma ; they are unconnected with the old bundles of the primary axis, but are continuous above with the lower ends of bundles be- longing to the branches occurring in these stems. The stems of herbaceous Mo- nocotyledons have the fibro-vas- cular system always in the form Fig. 576. Monocotyledonous flbro-vascular bundle (from the spadix of Phoenix dactylifera). A. Trans- verse section. B. Vertical section; p, parenchy- ma in which the bundles lie ; tc, wood-cells ; s v, spiral vessels ; d, reticulated ducts ; v p, vasa propria; I, liber-cells. Magn. 100 diam. of "stringy" fibres imbedded in succulent parenchyma ; and in those perennial stems of the Class which acquire a solid woody structure the ligneous character depends, not on the fibre-vascular system, but on the general parenchyma of the stem having its cells lignified (sclerenchyrna), of which we have examples in the Cocoa-nut and other Palms, in the Bamboo, &c. The rind of the Monocotyledonous stem, totally different from true bark, is generally little developed. On herbaceous stems it is a mere epidermis ; but on fleshy rhizomes it sometimes acquires considerable thickness, and is then found to be composed of spongiform parenchyma, with large air- cavities, the whole bounded externally by a few layers of tabular paren- chyma with a corky outer surface. A certain number of forms occur aberrant from the type above described. In Aloe the fibro-vascular bundles are so arranged as to form a kind of cylinder, separating a central from a cortical parenchyma. In the Snii- laceae, Dioscoreaceae, and some other Orders, the rhizomes imitate still more the Dicotyledonous arrangement ; for not only do the bundles stand in circles, they do not pass wholly off into the leaves, but run continuously through the structure. Still there is no periodical resumption of activity INTERNAL ANATOMY OF OKGAIS'S. STEMS. 529 in the "bundles, as in the Dicotyledons. In Tradescantia, and in the Grasses also, anastomoses of the isolated fibres take place at the nodes of the stem. Dicotyledonous Stems. The stems of Dicotyle- dons, and of Conifers which agree in the main points, are at first of very simple structure, almost resembling those of the Ferns ; but their fibro-vas- cular bundles being of the open or indefinite kind, capable of lateral growth by addition of new ele- ments season after season in their outer regions, the full-grown stems depart widely from the preceding types. For purposes of comparison, attention must be confined to shoots or stems of Dicotyledons in their first year of growth, as the formation of annual layers is a phenomenon to which there is nothing corre- spondent in the other Classes (excepting Conifers). When a young herbaceous stem of a Dicotyledon is cut across, we find the fibro-vascular bundles standing in a circle round a central parenchymatous mass, the pith, and enveloped by a cellular rind (fig. 577). The bundles run in tolerablystraightvertical courses and anastomose freely ; a certain number of bundles are distributed to each leaf. As the stem increases in age, each fibro-vascular bundle forms a wedge-shaped mass of wood (fig. 578) by development of the inner part of the cam- bium-region, and at the same time a layer of liber at the extreme outer side, next the bark. At the close of the first season, therefore, we have a central pith (fig. 578. p}, immediately bounded by the vascular portion of the bundles (called the medullary ^sheath) (m s), from which pass the vessels to supply the leaves ; next come the wedges of wood (w), formed of pro- senchyma (pr) and ducts (d, d) in most Dicotyledons, of prosenchyma alone 'in Conifers, which passes into the cambial or generating layer (c); and this is continuous outside with the ft&er-bundles (/), corresponding to the wedges of wood : the liber-fibres, like the inner vascular elements, send branches to form part of the ribs of the leaves. The fibro-vascular bundles, standing side by side, do not become abso- lutely united, but are separated by thin plates of compressed cellular tissue, running out from the pith to the cortical parenchyma j these plates are called medullary rays (fig. 579). The liber-portions of the bundles are associated with rows of clathrate cells (p. 487), and frequently with latex-canals (p. 513), and they are sur- rounded by a layer of parenchyma, composed of cells filled with sap and containing chlorophyll, the herbaceous or cellular envelope (fig. 578, c p) ; and this is protected externally by the dry suberous layer (s I), whi< h succeeds to the epidermis when the herbaceous shoot acquires a woody character. Modifications. Many special modifications of the above type are met with in Dicotyledons. In the Piperacea3 there is a kind of double con- 2entric circle of fibro-vascular bundles, the inner circle supplying the 2M Diagram of the arrange- ment of the fibro-vascu- lar bundles in a yearling stem of a Dicotyledon. 530 PHYSIOLOGY. leaves, but not possessed of a cambium-region ; while the outer circle is of the ordinary open or unlimited character. In the Sapindacese, Malpi- ghiaceae, and some other Orders, part of the fibre-vascular bundles remain separate from the principal circle, and lay the foundation of a number of secondary cylinders of wood enclosed by a common bark ; this pheno- menon may'be well observed in Calycanthus, where a square form of the stem results from four fibre-vascular bun dies remaining free from the central cylinder of wood in this way. In the Nymphseaceas we find a very aber- rant condition : the fibro-vascular bundles, formed of vessels and paren- chymatous cells alone, without wcod, are quite isolated, destitute of cam- bium, and form a complicated interlacement closely resembling that oc- curring in Monocotyledons there being no distinction of pith and medul- lary rays, and no bark. Dicotyledonous fibro-vascular bundle (Plane-tree) of one year's growth. A. Transverse section. B. Vertical section ; s I, suberous layer of the bark ; c p, cortical parenchyma ; I, liber ; c, cambium-region ; d, ducts lying in the prosenchyma, or wood-cells, pr ; m s, medullary sheath of spiral vessels ; p,pith. The structures connected by b belong to the bark, those marked w to the wood. In A, the bundle is seen to be bounded on each side by a medullary ray, running from the pith to the cortical parenchyma. Magn. 50 diam. - A still more frequent source of diversity lies in the varied nature and mode of arrangement of the elements of t\z wood. In the Plane (fig. 578) we see the spiral and annular vessels succeeded by a body of prosenchyma, in which are scattered large pitted ducts. In the Hazel and Alder these ducts are far more numerous, as they are also in the Lime. In the Oak the prosenchymatous cells are very small, and become greatly thickened, but the ducts are large. The Box has very small and dense prosenchyma- cells and few and small ducts. In the spongy wood of the Bombacea3 the prosenchyma is almost wholly replaced by thin- walled parenchyma. INTEKNAL ANATOMY OF ORGANS. STEMS. 531 In the Coniferae there is a total absence of ducts, the wood being formed exclusively of prosenchyma with the peculiar bordered pits (fig. 537), or, as in Taxus, with both pits and a spiral fibre (fig. 542). Annual growth of Rings. With the commencement of a second season of growth, a Dicotyledonous stem begins .to acquire its especial peculiari- ties. When the buds open to produce new shoots, cell-division recom- mences in the cambium -region of the old bundles, and an additional layer of wood is added gradually during the season to that formed the year be- fore. Season after season this process is repeated, and thus the cross sections of the stems present a series of concentric laminee of wood corre- sponding to the number of seasons during which the stem has existed (figs. 579 & 580). Fig. 579. Fig. 580. Fig. 579. Diagrams of cross sections of a one-year (A), two-year (B), and three-year old (C) Dicotyledonous stem, or of the branches 1, 2, and 3 of fig. 580. The letters to A indicate : b, suberous layer ; e, cellular envelope running into the black medul- lary rays ; I, liber ; c. cambium- region ; n, wood ; p, medullary rays ; m, medul- lary sheath of spiral vessels ; p, pith. The figures to C, 1, 2, 3, mark the wood and liber belonging to the 1st, 2nd, and 3rd year. Fig. 580. Diagram of a vertical section of a Dicotyledonous stem 3 years old, with 3 branches marked 1, 2, 3, indicating the age in years of the branch and the internode below it. The figures below denote the ages of the layers of liber and wood ; p, pith ; c, cambium ; m, medullary sheath ; w c, layers of wood ; I, layers of liber ; 6, cellular and corky layer of bark. The concentric lamellae of wood in Dicotyledons are really annual rings in most trees of temperate climates. In the tropical trees it frequently 532 PHYSIOLOGY. happens that more than one ring is formed annually. In our own trees an interruption to the vegetation, such as is caused by an accidental de- foliation during the summer, produces additional annular markings. In the common Beetroot several rings are produced in one season. In some tropical trees (Malpighiaceae) the concentric circles are not very clearly marked ; in others they are even separated by a distinct layer of parenchyma. In the Bignoniaceae it is common to find the wood divided into four large portions, separated by wedge-shaped cortical struc- tures, giving in the horizontal section the form of a cross. The old stems of such plants as the Sapindacese &c., above referred to, with isolated bundles outside the central woody cylinder, acquire very anomalous forms with age, since each collection of fibro-vascular bundles is developed annually in its cambium-region, and hence the stem assumes the appear- ance of several stems enclosed in a common bark. In Cycads more than one year is required to complete a woody zone ; thus, in very old stems of Cycads, only a few rings are seen surrounding a voluminous pith. Heart-wood and Sap-wood. As woody trunks increase in size, the older parts of the wood frequently go on increasing in density by the for- mation of secondary layers in the cells of the prosenchyma ; thus the old central wood becomes more solid, forming what is called the duramen or heart-wood, which is sometimes deeply coloured by chemical changes or secretion of various substances, as we see in Ebony, Lignum Vitee, &c. The young external layers of wood, in which the ascending current of fluid passes freely, is called the alburnum or sap-wood. The chemical and physical changes which take place as the sap-wood passes into the state of heart- wood have been previously alluded to. Origin of the Fibro-vascular Bundles. The fibro-vascular systems of the branches of Dicotyledons originate independently in the bud from the procambium, but soon become blended with those of the parent axis, with which their layers of increase become uninterruptedly continuous. When a branch is broken oft' short, leaving no buds upon it to coutiiine its growth, it becomes surrounded and ultimately entirely enveloped by the succeeding annual layers of wood, and in this way forms a " knot." The numerous small knots of the wood of Pinus sylvestris arise from certain of its branches being broken off while small. Pith. The pith or medulla consists of parenchymatous tissue, filled with nutrient matters, stored up for the use of the growing- tissues. It is of most service in young twigs, and becomes more or less inert in after- life, and often disappears as the wood grows. It exists either as a con- tinuous cylinder, or is broken up into disks separated by cavities one from the other, as in the Walnut. The cells of the pith contain starch, or crystals, or simply air. In some cases some of the cells of the pith retain their vitality longer than others, so that there is an admixture of living and dead cells ; and in this way the differences in the pith may even serve to distinguish certain genera one from the other (Gris). Occa- sionally it is more or less completely lignified. Medullary Rays. The medullary rays (fig. 579, A) which separate the primary bundles are developed in the cambium-region with the yearly layers of wood, and always extend to the cortical parenchyma ; in the layers of successive years the new elements of the wood separate into INTERNAL ANATOMY OE ORGANS. ROOTS. 533 parcels divided by secondary medullary rays (fig. 579, B, C), which are repeated in each successive season. The course of the fibro-vascular bundles being slightly sinuous, from their lateral anastomoses, the medul- lary rays have, singly, no great vertical dimensions ; and their transverse diameter varies in different cases. Their cells become lignified in heart- wood. Liber. The liber (for an account of the construction of which see ante, E. 517) is usually formed in successive thin laminae composed of slender iterally anastomosing bundles of liber-cells; and in some plants these laminae are separated by layers of parenchyma or periderm, so that the liber-structure of old stems may be split into its annual layers. In some stems the liber ceases to grow after the first season. The bast of which Russia matting is made consists of the separate liber-layers of the Lime-tree. The " lace " of the Lace-bark tree (Lagetta lintearia) is the liber, and that of other trees of the Order Thymelaceae is used for tying up bundles of cigars &c. The Herbaceous Envelope. The cellular or herbaceous envelope (fig. 578, cp) is generally in an active condition of vegetation during the growing- season, since its tissue must increase laterally (tangentially to the stem) to allow of the increasing diameter, while it produces the new suberous structure on the outside. Cork-layers. The snberous layer differs much in its condition in dif- ferent trees. The general construction has been alluded to at p. 522. The Structure of the Eoot has of late attracted much attention from Nageli, E/einke, Janczewski, Van Tieghem, and others. It is only by studying the mode in which the originally homogeneous cellular mass of the root breaks up into distinct layers and assumes a different form and arrangement of its constituent cells that the structure can rightly be understood. The simplest idea of the root is that of a mere unicellular thread, such as we meet with in the lower Thallogens, and also in the shape of the root-hairs which are produced from the epidermis of more highly organized roots. Physiologically, viewing the root merely as an organ of absorption, this type of root is all important. But in most plants the root is something more than an organ of ab- sorption. It is a laboratory, in which nutritive matters are moved from place to place or are stored up for future use, so that roots of this character have much of the functions of the stem. Ac- cordingly we find, in roots of higher organization, considerable difference of structure, varying also in the different groups of plants. The roots of vascular plants may be defined as outgrowths from the interior of the stem provided with a root-cap (pileorliiza\ but as a rule never producing leaves or buds, and growing in length only near the point beneath the cap. The general structure of the roots of vascular plants may be defined as consisting of an epidermis, bounding a cortical paren- 534 PHYSIOLOGY. chyma, in which is plunged a central cylinder. The epidermis will be spoken of hereafter. The Cortical Parenchyma is wholly cellular, and may be gene- rally subdivided into two zones, an outer and an inner. The cells of the outer zone increase from within outwards (centrif ugally) , decrease in size towards the outside, and are so closely packed as to leave no intercellular spaces. The cells of the inner zone of the cortical parenchyma increase from without inwards (centri- petally), and decrease in size from without inwards. They are disposed in radiating series or in concentric zones, and have inter- cellular spaces. The Protecting Sheath. This, the game protectrice of the French, the Schutzscheide of the Germans, was first pointed out by Caspary. It is a special layer of cells, forming the innermost layer of the cortical parenchyma and separating it from the central cylinder. The cells of the protecting sheath are marked on their sides by transverse folds or ridges, the ridges of one cell fitting into corresponding furrows of its neighbour, so that the cells are " dove-tailed " into one another. In longitudinal section these undulations of the cell-walls give an appearance as of the rounds of a ladder ; in transverse section the appearance is given of very small oval dark spots in the middle of the lateral boundaries of the cell. The Central Cylinder (Pericanibmm) is originally a mass of pleroma or growing cellular tissue : the outermost layer of this develops into a special layer of pericambium, which is thus in im- mediate contact with the protecting sheath on the outer side, its cells being so arranged as to alternate with those of the sheath. Thus one cell of the pericambium comes between two of the sheath, and so on. Hence the layer is readily recognizable under the microscope. The central mass of plerorne forms the vessels which are developed centripetally and alternately with bundles of bast or liber-cells, also developed centripetally. The untransformed cellular tissue surrounding the vessels and bast-cells is called the connecting tissue. Hoots of this character, then, differ especially from the stem in having their bast or liber-cells alternating in position with the vascular bundles proper, not placed external to them. Roots of Vascular Cryptogamia. The structure of the roots of the higher Cryptogams is identical in the main with that just described ; when once the primary structures are completed no further change takes place. The new rootlets originate from the inner layers of the cortical parenchyma. The roots of Equisetaceae have no pericambial layer. Roots of Monocotyledons. The general structure is the same as that of the Vascular Cryptogams, the rootlets originating from the pericambial INTERNAL ANATOMY OF ORGANS. BOOTS. 535 Fig. 581. or rhizogenous layer opposite to the vessels (fig. 581 , A, # r), except in Grasses, where they originate opposite the liber-bundles. The anatomy may be easily studied by tracing the development of the adventitious roots on the rhizomes of Rushes, .Flags, and other plants of this Class. The roots originate in the region where the fibro-vascular bundles of the stem terminate (and frequently form a fibrous plexus). They are at first wholly cellular, and we may dis- tinguish in them three parts, a woody axis, which soon becomes continuous with the fibro-vascular plexus ; a cortical parenchyma, con- tinuous with the inner part of that of the parent stem ; and a kind of conical hood of rather dense cellular tissue, enveloping the end of the root. As the root grows it pushes the hood forward, which breaks down the cellular tissue before it, and finally appears externally. When the epidermis is ruptured in this way, it presents a circular free edge standing up slightly like a collar around the base of the free part of the root : this is called the coleorhiza (fig. 581, B, c) by some authors. The conical hood upon the apex of the root forms the root-cap or the pileorhiza (fig. 581, B,;?), and is more or less persistent in different cases ; in aquatic plants it becomes greatly developed, as may be seen in /. f fn f the Duckweed (Letnna), where it forms a long sheath, appearing as Development of adventitious roots nium. A, B. Fragments of a rhizome with cortical parenchyma (cp), fibrous layer (f) where the fibro-vascular bundles terminate, and central region (mp) in which the bun- dles run. A, a r, shows an adventitious root arising from the cambium tissue at the out- side of the fibrous layer: in B the more ad- vanced root (a r) has emerged, leaving a ragged collar or coleorhiza (c), and haying a root-hood or pileorhiza on its extremity . if slipped over the end of the rootlet. The focus of development of the root is within the pileorhiza, which is pushed forward by the continual development of cells just behind the apex. The pileorhiza may be compared to a kind of shield or guard to the tip of the root, protecting the nascent tissue, by the expansion of which it is pushed forward, itself always possessing a certain solidity which enables it to penetrate between the particles of the soil. In a cross section of the root of a Monocotyledon we see the centre occupied by prosenchymatous tissue, with a circle of vessels around it ; the whole enclosed by regular parenchyma, sometimes by liber-cells, and covered by an epidermis. The ring of vessels spreads out into a kind of rosette at the base, and anastomoses with the extremities of the fibro- vascular bundles of the stem in the fibrous region. Secondary adven- titious roots are formed in the same way in the roots, originating imme- 536 PHYSIOLOGY. diately upon the "vascular ring and breaking through the cortical parenchyma. The "woody adventitious roots of arborescent Monocotyledons differ only in the greater development of the fibre-vascular structures; and they emerge from the stem (Palms) in the form of thick conical shoots. When adventitious roots, like those just described, die away, they decay down to their very origin, and leave a scar in the form of an orifice surrounded by the ragged coleorhiza. In the thickened adventitious roots of Asparagus, which perform the function of tubers, the parenchyma is greatly developed. In the tuberous roots of Orchids (figs. 21 & 22) the central woody axis becomes irregularly expanded into parenchymatous tissue driving 'the vessels out nearly to the periphery, so that the characteristic structure is greatly disguised. The aerial roots of the epiphytic Orchids have the growing extremities clothed by several layers or a parenchymatous tissue, in which the cells are characterized by delicate open spiral-fibrous secondary layers. Roots of Dicotyledons. In these plants the root has at first the same structure and arrangement of its elements as in Cryptogams and Mono- cotyledons, the rootlets being formed opposite the vessels from the peri- cambial layer. A great difference, however, shows itself in a secondary Fig. 582. Fig. 583. Fig. 582. Extremity of the root of a germinating Turnip, with root-hairs. Magn. 30 diam. Fig. 583. Longitudinal section through young root, showing the root-cap. formation of liber and vessels, which enables the roots to thicken and even to form concentric zones exactly as in the stem. In the early stage of the Dicotyledonous roots the bundles of liber-cells and the bundles of vessels are, as in the other groups of plants, alternate with each other, but a secondary formation of cambium-cells takes place on the inner side INTERNAL ANATOMY OF ORGANS. ROOTS. 537 of each of the primitive liber-bundles. This secondary cambium grows both on its outer and its inner surface, forming ultimately on the outer side liber-cells, on the inner side vessels exactly as in the case of the Dico- tyledonous woody bundles. In general terms, then, it may be said that tne Dicotyledonous root consists of a cellular mass encircled by cortex. In the central cellular mass are formed two or more sets of vessels and of liber-cells, each distinct from the other and alternating one with the other (fig. 583). After this primary stage of growth is completed, a secondary development of fibro-vascular bundles, with the liber outside and the vessels inside, takes place on the interior of the primitive liber- bundles, which latter are therefore pushed outwards. Ultimately, then, there are two or more radiating plates of primitive vascular tissue sepa- rated by cellular tissue from a series of radiating plates, consisting of liber and vessels. Great variations occur in different plants in the number and exact dis- position of the bundles &c., for an account of which the original memoirs of the authors above cited must be consulted. In the adult state the axial root of Dicotyledons, being a direct con- tinuation of the stem, displays a circular group of fibro-vascular bundles as in the ascending axis ; but these mostly converge at the point of junction of stem and root (collar}, so that the central axis of parenchyma, the pith, is usually absent, the medullary rays remaining as in the stem. The roots of Dicotyledons increase in diameter by annual layers of wood formed in the fibro-vascular bundles, these, however, being less regular in their arrangement than those of the stem on account of the tortuous course of the roots j hence while the wood of the roots is often useful for ornamental purposes, it is comparatively valueless for carpenters' uses. The branches of the axial root are originally growths from the apex of the root, thrown off to the side, as it were, and their woody axis is derived from a division of that of the main root. The radicle of a germinating Dicotyledon has its root-cap, and grows in the same way as that of the Monocotyledons, by development of cells just behind the apex (figs. 582, 583). Root-hairs. Young roots are covered by a delicate epidermis ; and the cells of this are abundantly produced into hairs in many plants (fig. 584), especially in those growing in light soils ; these fibrils are deciduous, the delicate epidermis (which is always desti- tute of stomata) being gradually converted into a corky layer. Adventitious Roots are very common in Dicotyledons, especially the herbaceous perennial kinds, and they alone can exist on plants raised from cuttings &c. of stems. The roots originate much in the same way as those of the Monocotyledons, appearing first as cellular cones in the region adjacent to the cambium -layer, with which the fibro-vascular structure soon becomes confluent. They break through the rind, with a coleorhiza, and protected by a pileorhiza, just as in Monocotyledons ; but when once formed, they appear to branch in the same manner as the axial root, and not by the formation of secondary adventitious roots. Trecul states that the structure of adventitious roots differs according to the part of the stem whence they emerge. If, for instance, they originate opposite a fibro-vascular bundle, as in Nupha,r, the centre of the 538 PHYSIOLOGY. root is occupied by a bundle of n'bro-vascular tissue ; if they spring from the stem opposite the pith or cellular tissue between the vessels, then the centre of the root is likewise cellular. In Cryptogams, according to Nageli, the roots always originate opposite a n'bro-vascular bundle. The primary form and disposition of the roots depend in a measure on the form of the terminal cells and on the direction of the partitions by which they are divided lengthwise, horizontal, or oblique. Fig. 584. a, epidermal cells ; b, c, d, root-hairs. Tubei-cras Roots of herbaceous Dicotyledons present several modifica- tions in the arrangement of the structures. In the Carrot and Parsnep the fibro-vascular ring has its component parts much separated by the great development of the medullary rays and masses of parenchyma re- placing the ordinary prosenchyma of woody roots, so that the fibro- vascular structure has a deceptive resemblance to that of Monocotyledons ; and the cortical parenchyma, again, is greatly developed, so as to form a thick fleshy rind. In the Turnip the cortical parenchyma is little deve- loped, and the mass of the fibro-vascular bundles lies immediately under the rind, the inner vascular parts of the bundles being split up, as it were, INTERNAL ANATOMY OF ORGANS. LEAVES. 539 into a row of fibres radially arranged and imbedded in a great quantity of lax parenchyma. The libro-vascular bundles converge at the " collar," and then separate again to surround the pith of the stem ; they also con- verge again towards the point of the root. These so-called roots are more nearly allied to the stem, and are, indeed, hypocotyledonary stems. The structure described under the name of spongiotes has no existence in nature. The error has probably arisen from the appearance presented by the pileorhiza. Old roots of Dicotyledons present a dense heart- wood like the trunks, passage of fluid taking place through the outer layers. When the older parts of roots are exposed to the air by removal of soil, they acquire a thick corky periderm. The general structure of the root of Gymnosperms is like that of Dico- tyledons, except that there is no dermatogen, the outer layer of the p'eriblem becoming transformed into epidermis. Fig. 585. Projection of a fragment of the leaf of the Turnip, constructed from sections made in various directions, and magn. 100 diam. : e, epidermis of the upper surface with its stomata ; e , epidermis of the lower face ; , stomata, cut through, opening into intercellular cavities ; TO, close parenchyma (palisade cells) of the upper part of the leaf; m', loose and spongy parenchyma of the lower part ; f.b, the cut end of a fibro-vascular bundle forming on of the veins of the leaf. Structure of Leaves &c. The plan of construction of the leaves and of the other appendicular organs of the stem is in the main identical throughout all cases; but there is very considerable variation within the limits of the general type. The essential character of the anatomy of a leaf is, that it is an expanded layer of parenchyma clothed over its whole surface with epidermis, and furnished, according to its degree of development, with a more 540 PHYSIOLOGY. or less extensive and complicated framework of fibro-vascular bundles. In the leaf of tlie Turnip, for example (fig. 585), we find an upper (e) and lower (V) epidermis, with an intermediate mass of parenchyma (or merenchyma, m, m'), rather close in the upper part, whence the name palisade tissue, and spongiform in the lower part. The epidermis is studded with stomata (a), which open into intercellular spaces commu- nicating freely throughout the spongy tissue, and, further, through the petiole, with the intercellular passages in the stem. The fibro-vascular system (ribs and veins) runs through the lower lax parenchyma (fig. 585, /.>), and consists of bundles of spiral vessels and liber, the former continuous with the medullary sheath and youngest part of the vascular axis of the stem, the latter continuous with the liber-bundle outside the cambium. The primary ribs in most Dicotyledons contain much liber, and thus become very thick, so as to project from the lower face of the leaf. They have a structure almost precisely like that of a small branch. Great differences result from the different degrees of development of the spongy portion, as may be seen by comparing the leaf of the Lilac with that of the Aloe or Mesemlryanthcmitm &c. The degree of consoli- dation of the epidermis bv the formation of thickening layers is the principal source of difference in the degree of solidity of leaves. Submerged leaves of aquatic plants have no stomata nor any extensive intercellular system ; the epidermis is also little developed, and there is commonly a total absence of fibro-vascular tissue : hence the delicate and perishable character of these organs. The leaves and other appendicular organs are especially the seat of the glandular and analogous epidermal structures. Structure of Petioles. The petioles usually consist of a mass of paren- chyma, surrounded by epidermis and traversed by fibro-vascular bundles arranged in a more or less semicircular manner, the spiral vessels being uppermost, corresponding to the medullary sheaths. When cylindrical the bundles form a complete circle, and the structure is then undis- tinguishable from that of a young branch, on which account the ordinary leaf has been regarded as a branch the upper portion of whose vascular tissues are suppressed or depauperated (C. deCandolle). Fall of the Leaf. The fall of the leaf, as of the fruit, and in some cases of the branches (as in Taxodium, &c.), is effected by the gradual for- mation of a layer of thin-walled cells across the petiole, at right angles to the direction of the other tissues, and which thus ultimately separates the inert leaf from the living stem as by a knife-blade. Structure of the Floral Organs. Bracts, sepals, petals, &c. are organized on the same plan as leaves, their epidermis frequently presenting raised conical cells and having stomata. The tissues of these organs are more delicate, the fibro-vascular structures being almost exclusively formed of spiral vessels. The parenchyma of petals contains fluid colouring-matters instead of chlorophyll. In the parenchyma of the floral organs of coloured structures, the cells are filled with fluid colouring-matters of various tints, the depth of colour STRUCTURE OF FLORAL ORGANS. 541 depending on the greater or smaller number of layers of colour-cells beneath the epidermis, the tints differing accordingly as cells containing colouring-matter of different hues overlie one another. Structure of the Anther, &c. Stamens and pistils are composed of rather regular parenchyma with a delicate epidermis, and fibro- vascular ribs more or less developed in different cases. The structure of the anther is somewhat complex, varying not only in different plants but also in different stages of growth. At first consisting of cells of about the same size and form, it subsequently presents a central mass devoted to the formation of the pollen (see under Physiology of Reproductive Organs). This central mass is overlain by three layers of cells : first in order going from within outwards is the endotliecium, con- stituted by a single layer of delicate cells of a different size and shape from the rest, and usually disappearing as the pollen-grains are matured. These cells appareutly contain nitrogenous contents, supposed to be applied to the nutrition of the pollen-cells during their growth. This layer is persistent in the case of anthers opening by pores. Succeeding the endothecium are one or more layers of permanent cells, some of which contain spiral fibres. These cells constitute the mesothecium. The fibrous cells vary in number and situation in different plants, and are sometimes entirely absent, as in the case of anthers opening by pores ; hence they are supposed to act hygrometrically in the dehiscence of valvular anthers. The third layer of the anthers is of an epidermal character, and is called the exothecium. The connective has the general structure of the filament ; sometimes, as in some Lilies, it contains fibrous cells. Each cell of the anther is partly subdivided by cellular projections from the connective; to these processes M. Chatin gives the name of jtlacentoidS) being of opinion that they contribute to the nourishment of the pollen. Pistil. The pistils and fruits have, for the most part, the general structure of leaves. Some of their fibro-vascular bundles run along the placentas and give off spiral vessels through the funiculus to terminate at the chalaza of the ovule. The style has usually in the centre a quantity of loosely packed, cylindrical, elongated cells, constituting the conducting tissue for the pollen-tubes. The stigmatic cells are devoid of epidermal covering, and hence present the form of partly detached prominences or papillae. Ovules, Seeds. The coats of the ovule, as well as the nucleus, are de- scribed as wholly cellular; frequently, however, the vascular tissue, instead of ceasing at the chalaza, is prolonged upwards into the coats, as may be seen in the testa of many seeds, e. y. Almond, Walnut, Cycas, &c. Great changes take place in the nature and arrangement of the cells as the ovules ripen into the seeds. The disposition of the cells of the outer investment of seeds is often very beautiful and characteristic. In the ripening of the fruit the organizing tissues, which carry on the growth of the organ, are situated between the inner epidermal layer and the fibro-vascular zone, as in the case of leaves. IVloreover the fibro- vascular bundles are arranged, as in the leaf-blade, with reference to a surface, and not in a cylindrical disposition as usually in stem-organs. 542 PHYSIOLOGY. Thalamus. The anatomy of the thalamus or receptacle cor- responds with that of the stem. Hollow receptacles, like those of the Rose or of the Apple, in which the carpels are enclosed or imbedded, have essentially a stem-structure, their cambium-layer being placed between the fibro-vascular zone and the outer epi- dermis. Anatomical and organogenetic investigations show that inferior ovaries (p. 130) are really cases of adhesion of the imbedded carpels to the expanded upper extremity of the thalamus. The parts of the flower, and especially the carpels, show many minor variations of structure not clearly referable to either the leaf or the stem type of structure ; and from these, as well as from numerous exceptional and transitional cases, it must be assumed that the distinction between leaf and axis is not absolute but arbitrary, though it must for convenience' sake be retained. CHAPTER II. PHYSIOLOGY OF VEGETATION. Sect. 1. GENERAL CONSIDERATIONS. Plant Organization. The organization of plants is regulated by a series of laws which exhibit different degrees of generality. The most general law of all is that under which protoplasmic substance assimilates inorganic or, more rarely, organic matter, and produces the closed cellular sacs called vegetable cells. This affects all vegetable structure whatsoever. Animal protoplasm has apparently no power of assimilating inorganic matter. The Fungi and parasites live on organic matter ; and this is probably the case to a great extent with cultivated plants grown with excess of organic manures. This will be referred to hereafter. One degree less general are the laws regulating the forms of the cellular sacs or cells. These determine at the same time the specific form of the plant in the Unicellular Algae. Next follow the laws of development of the secondary deposits upon the walls of the cells, which are valid throughout the whole Vegetable Kingdom, but more and more complex in the successively higher classes. The laws of combination of the cells into tissues are a little less general, the diversity increasing here again in proportion to the higher position of the species. The laws regulating the forms of organs are of very great importance and interest j and in these we have to distinguish two aspects, or, it may be s.aid, two coexistent series. GEKEKAL PHYSIOLOGICAL CONSIDEBATIONS. 543 The principal Classes of Plants are characterized by respectively possessing a peculiar type or plan of combination of the organs, having not only a morphological but a physiological speciality. The type, more or less recognizable, is a mark of the existence of a common law of in- herited organization throughout each class. Within the limits of the Classes exist almost infinite varieties of form, referable to morphological laws which have been investigated in the First Part of this work. A complicated but graduated and interconnected body of laws was there shown to regulate the variations of forms in plants generally. Lastly, in the description of the Natural Order of plants, it will have been recognized that there are still more special laws of development, causing the existence of resemblance in limited groups of species; and, beyond this, every species or kind of plant has its form and mode of life more or less definitely fixed and regulated by its special law of organiza- tion derived from hereditary descent, and modified in accordance with external circumstances and the requirements of the plant. These reflections enable us to explain simply the terms higher and lower classes or species of plants. In the Protococcus, consisting of a simple cell, the specific law, that which determines the characteristic foini, follows immediately on the first of those above indicated. In a Conferva, the second and third are both involved ; and the specific law at once succeeds these. Proceeding step by step, we shall find species in which there is a diversity of forms of the cell and of tissues (higher Algse) ; next, an additional diversity of organs (leafy Cryptoganiia) ; and then come into play the laws of the physiological and morphological types of combination of organs, which are most complicated in the Flowering Plants, in the development of which, however, from the original germ, or embryonal vesicle, we may trace, in a graduated series, the commencement of the operation of the successively less general laws of organization. Xot only do different plants display great diversities in structure and composition, but each individual plant offers more or less diverse characters at different periods of life. Plants commence their independent individual life in the form of a cell or a group of cells separated from a parent organism. In the lower plants such cells, once fully developed, as spores or as yonidia, are capable, under suitable circumstances, of growing up into complete plants. In the higher Classes these cells (embryonal vesicles, or the primary cells of a leaf-bud) go through the earlier stages of development connected with the parent organism, and are detached (as seeds or as bubils, &c.) already provided with rudi- mentary organs of vegetation. Duration of Vitality. In those cases where the detached bodies are products of simple vegetative cell-division, they often proceed at once to grow up into new plants (gonidia, zoospores), but more frequently their vitality remains latent for a certain definite period (bulbils, spores of Mosses, Ferns, &c.) ; and when the body is a result of sexual reproduction, it almost always remains for a more 544 PHYSIOLOGY. or less indefinite period (capable of being shortened or prolonged within certain limits by external causes) in a state of rest (seeds, resting -spores of Alyce, &c.), and then undergoes peculiar internal changes before recommencing development (germination) in order to grow up into a new plant. Seeds and resting-spores (and to a less extent the resting- organs pro- duced in vegetative propagation, as bulbs, tubers, &c.) are organized in a manner especially adapted to preserve the latent vitality from injury by external influences. They can withstand great variations of heat or cold, especially in the absence of moisture. Most seeds will bear a temperature very far below freezing-point if kept dry. Wheat left in the Arctic Kegions by the crew of the ' Polaris,' and brought home by Sir George Nares, after two years, was found to have its germinating power unim- paired, and many will even bear an exposure to 100 or 110 Fahr. in dry sand. Prolonged immersion in water at 120 kills most seeds, unless the skin is very thick and they contain oil instead of starch in the endosperm. Some seeds will bear a short immersion in boiling water ( Veronica) ; but the seeds of Cereals, Beans, Linseed, and other plants scarcely survive a 15 minutes' soaking in water of 110, while they will bear 140 in steam and 170 in dry air. Some seeds naturally lose their vitality very soon : this is the case with the seeds of Cqffea, Magnolia, &c. j while other instances are related in which it has been preserved for centuries. The cases related of the germination of Wheat taken from Egyptian Mummies are fallacious : but well-authenticated instances exist of long preservation. The resting-spores of Oonfervoids (Protococcus) have been revived after remaining for years in herbaria ; and it is in curious relation to their growth in shallow pools, often dry in summer, that the resting-spores of these plants appear to require to be dried before they will germinate. Mr. Munby found a bulb of a species of Narcissus sprouting in his herbarium after it had been gathered (in Algeria) upwards of twenty -two years. This bulb, removed into the greenhouse and potted, produced flowers. Periodicity of Growth. Plants are subject to a periodicity in their vital phenomena, partly dependent on their own laws of growth, partly on the seasons in the climate where they grow. As dependent on special laws may be noted the differences between annual, biennial, and perennial plants (properly so called), between deciduous-leaved and evergreen trees, &c. Annual plants are such as germinate from seed, produce their whole vegetable structure, flowers, fruit, and seed, and die away in one season, between spring and autumn : such are the summer annuals of our gardens. Biennials sprout from seed in one season, and bloom, bear fruit and seed, and die in the second; the Turnip, Carrot, (Enothera Uennis, &c. are examples of this. Perennial plants exhibit several varieties of condition. Herbaceous perennials (like the Daisy, Primrose, Garden Flag, &c.) ger- minate in one season, and produce a subterraneous rhizome, of indefinite GENEHAL PHYSIOLOGICAL CONSIDEBATIONS. 545 duration, which annually sends up a flowering shoot or shoots. Other perennial plants of this kind form one shoot, which vegetates uninter- ruptedly for many years before it flowers (Agave americana, Talipot Palm, &c.) ; and after ripening its seeds the stem dies down, leaving usually a number of offsets from the axils of its leaves (monocarpic peren- nials}. Woody perennials, trees and shrubs, usually vegetate for several years before flowering, but are subject to periodic rest, throwing off their foliage and renewing it upon fresh shoots of the same stem every season ; and when they flower, the operation exhausts their accumulated powers of development so little that they continue to flower periodically (every season if in favourable condition) throughout life. Habit of Plants. The " habit " assumed by plants depends in some degree on external conditions. Thus many of our garden annuals are perennial in their native climates : for example, Eicinus (the Castor-oil plant), Mirabilis, and other genera are annual herbs with us, but perennial and even woody in warmer climates. And some annuals may be made to vegetate for more than one season by removing the flower-buds as they appear, as in the case of the so-called Tree-rnigiionnette. The Winter- corn of agriculturalists is really an annual plant, sown in autumn to obtain stronger growth, and is not specifically difl'erent from Spring- corn, sown in spring and reaped in autumn. The common Cherry-tree retains its leaves during the whole year and becomes an evergreen in Cevlon; and many similar instances of changed habit, the result of altered condition, might be cited, while for further particulars respecting the duration of plants the student may refer to the sections treating of the Morphology of Stems. Few perennial plants retain their appendicular organs beyond certain definite periods. Ordinary deciduous trees lose their leaves in autumn in our climate ; and previously to their fall their organs undergo internal changes, in which the assimilated matters are, for the most part, removed and their green colour altered. They are generally cast off by a regular fracture where they join the stem (p. 540) j in the Oak, Beech, and other trees they die in autumn, but do not fall away at once, often remaining, when not exposed to violent winds, until pushed off by the expansion of the stem in the next spring. Evergreen trees and shrubs retain their leaves green and living until the succeeding season, when the new leaf- buds expand, as in the Cherry-laurel, Aucuba, &c. j or, as in many Coni- ferse, they remain attached to the stem for several years (Araucaria imbricata, Thuja, &c.). In some of these cases the so-called leaves are probably f oliaceous branches. The leaves of arborescent Monocotvledons (Palms) are also of long duration. The parts of flowers and ripe fruits are likewise cast off in most cases, although the fruits from which seeds have escaped sometimes remain long attached in a dead condition (Conifers). The axis is the only permanent part of the plant ; and the unlimited duration of this is strictly dependent on the development of leaf-buds. When a shoot ends in a blossom-bud, the growth of that branch of the axis is arrested, and the prolongation of life depends either on the axillary leaf-buds situated below or on the formation of an adventitious bud. The production of flowers and fruit is an exhausting process j it has 546 PHYSIOLOGY. just been noticed that annuals may be made to live several years by pre- venting them from flowering. The arrest of growth of the large and highly developed axes of monocarpic perennials (Agave, Talipot Palm, &c.) is a necessary consequence of the terminal bud producing blossom instead of leaves ; but the formation of propagative offsets from the leaf- axils before death is strictly dependent on the degree of vigour possessed by the main axis at the time of flowering. The duration of herbaceous perennials may be regarded as unlimited, since they are always placed in a position to form new absorbing organs (roots) in the vicinity of their buds. The duration of trees is also theoretically unlimited ; and in many cases great age is attained; but ordinarily trees acquire increased vigour with age up to a certain point, and then begin to decline, a circumstance attributable to the increasing distance to which the buds are removed from the roots, the obstruction to the flow of sap, the local decay of the roots and trunk from external injuries, &c. Cuttings from old trees, if taken from sound shoots, may be made the foundation of new trees as vigorous as the parents were in their earlier years. Palm-trees grow to an age of 200 years or more ; the Draccena (Dragon- trees) of Teneriffe have been known as old trees for centuries. Oaks, Limes, Cedars, Yews, &c. are known to have lived many centuries; and other cases are on record of gigantic trees whose age, deduced from the number of rings of growth of the stems, would amount to upwards of 3000 years. The Bertholletice of Brazil, the Adansonice of Senegal, and the Wellingtonia or Sequoia gigantea of California (363 feet high and 31 feet in diameter at the base) are examples of this. Death of the Plant. In herbaceous perennials the older parts of the plant die and decay in a limited period after the develop- ment of the new axes. In Dicotyledonous trees also the older part, which is enclosed by the new layers, and becomes consolidated into heart-wood, must be regarded as dead after a certain period, ceasing even to carry sap mechanically ; and we see hollow trees of this Class living and growing, where the whole of the older part has been lost by decay, a living shell of wood constituting the bond of connexion between the roots and the growing branches of the axis. This death of the older tissue is not so common in arborescent Monocotyledons ; but it is observed in Pandanus (fig. 10), where the base of the stem and the old roots decay, new (adventitious) roots sprouting out from the living part of the trunk in a continual ad- vance upwards. The death of a plant or part of a plant depends upon the death of the cells composing its tissues. The duration of the life of individual cells is very different, according to their position and function. Cells situated at growing-points (in buds, cambium-regions, tips of roots, &c.) are very transitory, since during active vegetation they are continually divided, as parent cells, into two or more new cells, part of which are left behind as permanent cells, those situated at the periphery, or most advanced point, GENERAL PHYSIOLOGICAL CONSIDERATIONS. 547 becoming in turn the parent cells of a new generation. The permanent cells become parts of parenchymatous, prosenchymatous, or vascular tis- sues in the vegetative organs, or parts of reproductive structures in flowers and fruits. Thus they run through a course of life dependent in each case on the laws of development of the plant, according to which its organs have a shorter or longer duration. The death of the organ or tissue in which they exist results from the cessation of the vital activity of the cells according to these laws ; and their decay, from the now unopposed operation of simple chemical forces. Vital Phenomena. The principal vital phenomena exhibited by plants are connected either with the maintenance and increase of the individual organism, or with the production of special structures endowed with the power of growing up into new individuals when thrown off by the parent. We say the principal vital phenomena, because there are some which we cannot strictly affirm to belong to either of the above classes, although there can be but little doubt that they are in some way related ; of these are the movements of plants like the Sensitive-plants, the folding up of leaves or flowers, &c. Vegetation, Nutrition. The processes of vegetation, or growth of the individual, are, from the peculiar organization of vegetables, connected with the processes of reproduction, properly so called, by the phenomenon of multiplication or propagation through natural or artificial separation of portions of the structure which might remain and form branches of the parent stock. This vege- tative propagation, distinct in important anatomical and physio- logical characters from sexual reproduction, is found in all classes of plants, and from its importance in relation to cultivation deserves separate consideration. The construction of plants from a number of like parts more or less physiologically independent allows of their being increased by mechanical subdivision of the parent " stock," which is effected by making cuttings, &c. The same occurs in the propagation of plants by bulbs, tubers, &c. The Vegetative processes of plants are divisible into several heads, which, however, present many points of interconnexion. Nutrition, properly so called, can only be said to go on in the protoplasmic matters found in the interior of cells, since it is these substances alone that exhibit phenomena of consumption and repara- tion. The tissues of plants are, under ordinary circumstances, never renewed ; the only changes which they undergo are stages of progressive development or growth, succeeded sooner or later by decomposition. Development or organization constitutes the most striking mani- festation of the vegetative action ; but this is a final result, pre- pared from, and incessantly accompanied by, phenomena which are 2N2 548 PHYSIOLOGY. results chiefly o the regulated action of physical and chemical forces. The subsidiary operations of vegetation are absorption of food, diffusion or transmission of fluid through the organic structure, assi- milation of absorbed material, and, intimately connected with this, the processes of respiration, transpiration, and metastasis. Secretion is more nearly related to development than to the processes just enumerated. The relations of many of the secretions of plants are very obscure. Starch, chlorophyll, fixed oils, sugar, &c. are of course intimately connected with the vegetative growth ; but we have little clue to the importance, as regards the plant, of the essential oils, resins, alkaloids, &c. The Vegetative Propagation of plants presents special modifica- tions connected with the peculiar conditions of organization in the different Classes ; and there are some important considerations connected with the contrasts existing between the results of this and of sexual reproduction. The Sexual Reproduction of plants offers a series of phenomena of much interest when viewed comparatively throughout the different great Classes ; and the phenomena of Hybridization and the influ- ence of sexual reproduction in the maintenance of specific characters require especial notice from the vegetable physiologist. As the Vegetative propagation is a process of vegetative life trenching on the region of reproduction, so many of the phenomena accompanying sexual reproduction are properly special vegetative actions induced by peculiar stimuli : among these are the phenomena of ripening- of fruits and sporanges, the evolution of heat from flowers, the irritable movements of floral organs, &c. These, and some other unclassed phenomena, will be most conveniently examined apart. In the succeeding Chapters on Physiology we shall examine separately: 1, the processes of Vegetation ; 2, the phenomena of vegetative Propagation ; 3, the physiology of sexual Reproduction ; and, 4, various unclassed phenomena met with in a more or less limited range of cases of vegetable life. Sect. 2. CELL-LIFE. Movements of the Protoplasm, &c. Intimately connected with the early history of the protoplasm of the cell (p. 495) are cer- tain physiological phenomena of the contents of individual cells, which will be most conveniently described here. During the time when the protoplasmic contents of young cells are becoming gradually hollowed out into spaces filled with watery cell-sap (p. 494), a regular movement of this protoplasm takes place, which may be observed very readily in young hairs of Phane- rogamic plants (fig. 586), and which probably takes place in an CELL-LIFE. 549 Fig. 586. early stage in all other structures. This movement, which is erro- neously called rotation of the cell-sap, is a circulatory movement of the protoplasm made perceptible by the minute opaque granules which exist in the colourless fluid. The nucleus is also carried slowly along in this movement, which, when the protoplasm has become converted into a mere network of cords, has the appearance of a system of reticular currents (fig. 586). This move- ment of the protoplasm ceases in most cells before they are full-grown ; but in many aquatic plants, even of the class Phanero- gainia, the protoplasm does not become excavated in the same way as it does in the cells of hairs &c., but applies itself as a thickish layer upon the inside of the cell-walls, and, retaining its activity, per- forms a rotatory movement around the wall of the cell permanently. In CTiara the moving layer of protoplasm is not applied upon the cell-wall : the primordial utricle, with the chlorophyll-corpuscles imbedded in it, lies on the cell-wall motionless ; and a thick mucilaginous layer, situated between this and the cen- tral cavity filled with watery cell-sap, con- tinually circulates. The circulation in reticulated currents is most easily observed in young hairs of the higher plants. The movement of the parietal layer of proto- plasm is made very visible in the leaves of Vallisneria by the green chlorophyll-corpuscules imbedded in it j and it may be well seen in Ana- charis, in the delicate tissues of Hydrocharis, Stratiotes, &c. It occurs in the rootlets and other parts, as well as in the leaves. The phenomenon is most strikingly shown in the Characefe, especially in the Nitdlce, which are simpler and hence more transparent forms. This movement is only affected by substances that injure the healthy condition of the structure, such as chemical agents producing bursting or solution of the tissue, heat sufficient to cause coagulation or solution of contents, &c. In Char a, the large cells may be tied across, and yet the circulation be set up again in each of the chambers thus formed. Elec- trical currents do not affect it. Causes of the Movements ; Action of Light. The movements in the protoplasm are attributed to various causes according to the nature of the movement, such as contraction of certain portions of it, varying degrees of imbibition in different portions of the mass, the alternations in this wise giving rise to the currents. The movements connected with cell-division and growth and the rotation of the protoplasm take place in darkness as well as in the light. In many cases it has been definitely proved Two cells of a hair of the sta- men, of Tradescantia, with nuclei and reticulated cur- rents of protoplasm. Magn. 250diam. 550 PHYSIOLOGY. that the movement of the juices in which chlorophyll-granules are con- tained is directly dependent on the agency of light, especially of the more highly refrangible rays of the spectrum. Under the influence of diffused light the chlorophyll-granules range themselves parallel to the surface. At night, as well as under the influence of direct light and of the most luminous and least refrangible rays, they are disposed at right angles to the surface, on the lateral walls of the cells. If, however, the light fall from one side only, and the illumination be prolonged, the grains show a tendency to accumulate on the side of the cell most brightly illuminated, just as the zoospores of Algee do. Under unfavourable external condi- tions (low temperature, age, or deficient light) the chlorophyll grains are arranged against the sides of cells adjacent to others, and not on the free surface as under normal circumstances. Analogous to the rotation of tlie protoplasm are the movements of the ciliated zoospores of the Algae and of the ciliated spermatozoids or antherozoids of the higher Cryptogamia and the Algae. Zoospores are formed by the contents of vegetative cells becoming isolated from the cell-wall, and individualized into one (GEdogonium fig. 505), a few (Ulva, Ulothrix* &c.), or numerous (Cladophora, fig. 512, C, and Phseosporeoe) corpuscules, which break out from the parent sac, and when free are seen to be provided with vibratile cilia (2, 4, or many), and to swim about actively for a period of from half an hour to several hours, then to settle down, become encysted by a cellulose membrane, reassume the characters of ordinary vegetative cells, and grow up into new plants by cell- division. It has been observed that those zoospores with cilia at one end direct that extremity (which is destitute of chlorophyll) towards the light ; and, moreover, the locomotion of these bodies is accompanied by a movement of rotation on their own axis. Spermatozoids are filiform bodies of various forms, mostly present- ing one or more spiral curves, or minute globules, and usually furnished with vibratile cilia. They are formed by a metamorphosis of the protoplasmic matter of cells developed for the purpose in the anthericlia of the Cryptogamia. They are extremely minute, but move very actively when they escape from their parent cells, con- tinuing to swim about for some time, being destined to find their way to the archegoniuin (or to the spores in Algae), to perform the fertilization of the germ-cell. Many, however, never reach this, and they gradually dissolve away. In the Volvocineae (fig. 503, D) the separate primordial utricles lie imbedded in a common envelope, without a membranous cell-coat, retain- ing their vibratile cilia throughout life, only becoming encysted and formed into proper vegetable cells when converted into resting-spores. In the intimate affinity between these productions and the Protozoa, or lower Infusorial Animalcules, we perceive the close bond which exists CELL-LIFE. 551 between animal and vegetable organization when reduced to its lowest terms. As long as a cell retains its active protoplasm, it is capable of producing new cells and organized forms of assimilated matter, like starch and chlorophyll, in its contents. This is the case, of course, in all nascent tissues ; but it ceases to be so at various periods in different, parts of the vegetable organization. In all woody tissues, in all pitted and spiral-fibrous cells, it disappears early, secondary deposits of the ligneous character being formed apparently from the watery cell-sap. In herbaceous organs, such as leaves, in the cells of the Cellular plants generally, in fact in all the properly living structures, the protoplasm remains. This explains why the power to form adventitious buds exists not only in the cambium-layer of the higher plants, but, under certain conditions, even in the leaves (as in Bryophyllum, Gloxinia, &c.), and why gemma- tion or propagation by little cellular bulbils, or isolated cells detached from the vegetative organs, is so common among the Cellular plants, and in the Mosses and Liverworts, where parenchymatous tissues so greatly predominate. . Nutrition in Cellular Plants. The elementary structures being essentially alike throughout the Vegetable Kingdom, and the physiological phenomena of vegeta- tion depending almost entirely upon processes taking place in the individual cells, it is very instructive to examine the phenomena of nutrition and growth in those simply organized plants in which we are able to observe directly the changes in the living cells. Many cellular aquatic plants are especially adapted for these researches, from their simple structure, transparency, and their aquatic habit, which permit us to keep them in a growing condition in glass cells beneath the microscope. By way of illustration the history of the Yeast-plant is subjoined. The Yeast-plant. What is called the "Yeast-plant" consists of a particular form of the mycelium of a Fungus (fig. 587, Torula cere- visice). It is composed of simple cells, which will go on multiplying by budding for an indefinite time if placed in a liquid containing a mix- ture of saccharine or dextrinous substances, together with albuminous matters, at a moderately warm temperature (59-67 F.), bubbles of car- bonic dioxide being given off. These cells are simple membranous vesi- cles, with their walls formed of a modification of the compound (cellulose} of which all vegetable cell-membranes are formed, and mixed with which are very minute quantities of sulphur, phosphorus, potassium, magne- sium, and calcium. Within the cells exist nitrogenous matter in the condition of protoplasm, fatty matter, and water. The increase of the plant is dependent on the assimilation of substance requisite for the pro- duction of new cell-membranes, and of other substances to furnish new 552 PHYSIOLOGY. nitrogenous contents. When no material for forming cellulose exists, the plant cannot grow; but in solution of pure su^ar in the absence of any nitrogenous substance, the plant will multiply its cells for a certain time, the protoplasm of the old cells being transferred into the new ones as they are successively evolved. But under these latter circumstances the cells become gradually smaller, and at length cease to multiply, a portion of the nitrogenous matter being wasted in the reproduction until it be- comes insufficient to carry on the growth. On the other hand, if sufficient nitrogenous matter exists, the fermenta- tion goes on, accompanied by the production of a more developed form of the mycelium, consisting of elongated interwoven filaments (the so-called Vineyai<-plant) ; and development of this continues, if not interfered with, until the liquid consists of little else but pure water. The final form is the so-called " mother " of vinegar, which destroys the acetic acid. There fs another mode in which the Yeast-plant is multiplied, and that is Fig. 587. X.800 by endogenous segmentation of the cells. The protoplasm divides by segmenta- tion (fig. 593) into four subdivisions, around each of which a new cell-wall is secreted, as subsequently explained, p. 585. This mode of multiplication may be seen by placing a little yeast on a thin layer of plaster of Paris beneath a bell-glass so as to ensure sufficient mois- ture. After a week or more the new cells may be seen with a i object-glass. In whichever way the multiplication is effected it is clear that the .materials for SUCh increase niUSt be derived irom without the plant must feed; and it has been found, experimentally, that it requires substances to build up and renew its protoplasm or nitrogenous constituent, cellulose, or fatty materials or carbo-hydrates, mineral matters (sulphur, &o.), and water. It is not necessary that these substances should be in the food, simply that the latter should contain the elements out of which they can be formed by the plant. For experimental purposes Pasteur's solution * may be used : this consists of a solution of sugar, furnishing the hydrocarbon, ammonium tartrate supplying the requisite nitrogen, potassium phos- phate, calcium phosphate, and magnesium sulphate yielding the requisite mineral ingredients. The breaking-up of these ingredients, and their *$J*3f5*ISS8l liquid and smaller form on the surface of stale beer. * Pasteur's fluid : Potassium phosphate Calcium phosphate Magnesium sulphate Ammonium tartrate Cane-sugar 1500 Water... , 8576 20 parts 2 100 10,000 CELL-LIFE. 553 recombination in the plants in the single cell, is a " vital " property, one not possessed "by dead matter. Fermentation. The succession of phenomena exhibited is connected with a series of chemical changes which are probably somewhat as follows. The whole of the processes are accompanied by evolution of carbonic dioxide. The earlier growth can go on without access of oxygen, as is evident from the fermentation proceeding in large vats with a stratum of carbonic acid several feet thick over the surface of the liquid; the growth in the latter stages takes place most freely with access of air. The original liquid contains grape-sugar (glu- cose), or dextrine, and nitrogenous matters. If the yeast-cells be kept out from this fluid no fermentation occurs ; but if yeast be added the protoplasmic matter of the yeast decomposes a portion of the fluid, forming cell-membranes. The chemical action set up disturbs the com- bination in the rest of the sugar, which loses carbonic dioxide and becomes alcohol. If the growth of the Fungus continues, the alcohol becomes decomposed (seemingly by contact-action again), absorbs oxygen from the atmosphere, and becomes acetic acid. It is not clear in most cases to what extent the Fungus is nourished on the alcohol, or on the saccharine or dextrinous matters mixed with the alcohol. To form cell-membrane from alcohol would require the absorption of a large quantity of oxygen, and the formation of much acetic acid and water. The growth of the Vinegar-plant in solution of sugar, then, would appear to cause simple liberation of water, while the contact-action in like manner decomposes the sugar into acetic acid. The ''mother of vinegar" finally is developed at the expense of acetic acid, with separation of water. The processes here briefly described cannot be disregarded when we inquire into the mode in which plants generally take up their food. Not only do the Fungi all feed in this way as, for instance, the Dry-rot (Memliu9\ which lives on the dead substance of timber, or the parasites like Pttccm*<8. the Potato-fungus, c., which send their myce- lium into the tissues of living plants to feed upon their juices but the same laws evidently regulate the nutrition of the colourless parasites, such as Orobanchacese (p. 325), and the Balanophorads and allied plants (p. 354). Following out this train of reasoning, we are irresistibly led to the conclusion that the same processes may occur in all plants under particular circumstances, although not absolutely necessary except at certain stages of growth. Germination. In germination, doubtless the decomposition of the store of starch &c., with evolution of carbonic dioxide, during the recommencement of cell-development, is a phenomenon essen- tially similar to the development of the Yeast-plant. And we cannot find any reason to suppose that the roots of plants can refuse to take up organic matters existing in a state of solution in the soil. The extent to which growth may be stimulated, without access of light, by profuse supplies of organic food, is strikingly illustrated by the many succulent vegetables cultivated for the table, 554 PHYSIOLOGY. such as Sea- kale, Celery, forced early Rhubarb, &c. And the tissues of the plants thus grown have exactly that weak, succulent character which is so striking in most leafless parasitic plants and Fungi. Further applications of these facts will be dwelt on in the succeeding Sections. Assimilation of Inorganic matter. By far the most striking phenomena of vegetative life are those in which inorganic matters are assimilated, and the gaseous and liquid constituents of the atmosphere and soil supply the requisite food. If all plants required organic food, the organized substance upon the globe must continually decrease, since, as we have just seen, those which do live upon organic matter waste this through decomposition by contact- action. But the organic matter of soils, upon which plants grow and decay in successive crops, undergoes continual increase, as we observe in the accumulation of vegetable mould on undisturbed grass plains and in forests where the debris (fallen leaves, underwood, &c.) is^not removed. Food of Plants. The majority of plants feed upon water, carbonic dioxide, ammonia, nitrates (and perhaps other nitrogenous compounds), with small quantities of various other elements, such as sulphur, phosphorus, and the salts of lime, potash, &c. Such plants can only flourish under the influence of light ; and under this influence they produce, from the above materials, new cellulose &c. and protoplasmic matter. The assimilation is in such cases , as a general rule, accompanied by the assumption of a green colour, from the formation of chlorophyll. Exceptions to the last assertion appear to exist in the red, olive, and other peculiarly coloured Algae, in which no chlorophyll is produced ; bat we are ignorant of the processes which go on in the vegetation of these plants. Nutrition in Alg9B. The history of the changes which take place in the cell-contents of the green Confervoid Algae (figs. 512, 513), which we are able to observe to a certain extent beneath the micro- scope, affords some material towards the comprehension of the pro- cesses which have their seat in the green parts of the higher plants. We observe, in the elongating apical or branching cells of the Confer- voids, that the contents of the nascent parts (as in the upper half of the dividing-cell of (Edoaoninm &c.) are chiefly composed of colourless pro- toplasm, with watery cell-sap. Under the influence of light, green chlorophyll-corpuscles become more and more abundant; and, under favourable circumstances of light &c. (accompanied by liberation of oxygen gas), the chlorophyll-corpuscles soon present starch-granules in the interior, which multiply and increase considerably in size. This formation of starch occurs chiefly after the cell has attained its full growth, and may be regarded as a continuation of the process which FOOD OF PLANTS. 555 produced r the cellulose of the cell-wall, now no longer required for the purposes of the individual cell, the contents of which, however, proceed with their assimilative action. After a time the cell prepares for propagation, or reproduction. Then the starch-granules disappear, apparently by solution, into dextrinous or analogous matter requisite for the development of new cell-membrane, which soon takes place, either in cell-division (p. 451), or, if the primordial utricle is dis- charged from the parent cell in the form of zoospores (p. 451), in the formation of the cell-membranes of these bodies after they have come to rest. Where resting-spores are to be formed, different changes ensue after the solution of the accumulated starch. The new cell, intended to remain in a quiescent condition, becomes coated by a cellulose membrane, or often two distinct concentric coats ; and, at the same time, that portion of the contents consisting of dextrinous or analogous matter which has not been consumed in forming cell-membrane becomes converted into Jived oil, the green colour disappears, and the contents assume a red or brown colour, and external stimuli (light, &c.) produce no influence. When these bodies germinate (which usually only occurs after they have been dried up and are again placed in water), the chlorophyll gradually reappears and the oil vanishes, and the entire course is run through again. Transfer of Stored Nutriment Metastasis. Comparing these phenomena with what we observe in the higher plants, we notice the similarity as re- gards the production of chlorophyll in the leaves, followed by the appearance of starch-granules, as a form of accumulated nutriment. But the functions being more localized as the organization is more complicated, the starch thus formed is subsequently dissolved, and is carried away to the growing tissues of the plant, to the buds, cambium-region, and roots, where it is laid up in autumn, very often in this same form, but not unfrequently in the condition of h'xed oil, as in the rhizomes of Cyperus, of Lastrcea Filix-mas, &c., and, above all, in structures which, like the resting-spores above mentioned, are to remain quiescent while exposed to considerable diversity of external conditions, namely in seeds, as in the cotyledons of Cruciferae, Almonds, Nuts, Walnuts, &c., or in the perisperm of Poppies, Euphorbiaceee, &c. The oil (or starch in other cases) stored up in the seeds and rhizomes by metastasis undergoes decomposition and solution in germination, to supply material for the cell-membranes of the nascent plant until the roots have become sufficiently developed to provide for it. We have at present no very satisfactory evidence of the kind here brought forward to indicate the mode in which the nitrogenous matters, necessary for the formation of new protoplasm, are taken up. The ques- tion of the assimilation of nitrogenous matters will be considered in the following section, on the Food of Plants. Sect. 3. FOOD OF PLANTS. Constituents of Plants. The first step in the investigation of this subject is to ascertain what substances enter into the compo- sition of vegetable structures and juices. 556 PHYSIOLOGY. Analyses of plants by chemical means, and in some instances by the spectrum, have demonstrated the existence of the following che- mical elements in plants : Oxygen (0), Hydrogen (H), Carbon (0), Nitrogen (N), Chlorine (Cl),' Bromine (Br), Iodine (I), Fluorine (F), Sulphur (S), Phosphorus (P), Silicon (Si), Potassium (K), Sodium (Na), Calcium (Ca), Magnesium (Mg), Aluminium (Al), Manganiuin (Mn), Iron (Fe), Zinc (Zn), Copper (Cu), Lead (Pb), Titanium (Ti), Arsenic (As), Lithium (Li), Rubidium (Ifcb), Csesium (Cso), Strontium (Sr), and Barium (Ba). All of these, however, do not exist in every vegetable substance ; the first four are universally present, while a perfectly healthy condition can- not be assured unless sulphur, potassium, calcium, magnesium, iron, and phosphorus are also present at some time or other. Some of these substances are dissipated by burning, others remain after burning and constitute the ash ; such are the earthy alkalies and metallic substances. The propor- tion of ash ingredients is about 3-6 per cent, of dry matter, i. e. matters dried till they cease to lose weight at a temperature of 100 C. Proportionate Quantities of the Constituents, These elements are not taken up by plants in a simple form ; and none of them exist as such in. vegetable substances. The compounds of the different elements differ much in the proportion in which they exist. Water (HO or H 2 O) may form 90 to 95 per cent. Of the dry substance, compounds of carbon, hydrogen, and oxygen (C, H, 0) may form 66 per cent. ; the carbon furnishing about 50 per cent., the oxygen about 33 per cent., the hydrogen about 5 per cent., the nitrogen |-4 per cent. ; the alkalies, earths, and metallic oxides commonly form 1 to 4 per cent., in rare cases as much as 20 per cent. The great mass of all plants is composed of the first four elements in the list the solid parts of compounds of carbon, hydrogen, and oxygen ; the protoplasmic cell-contents of compounds of these three elements, with the addition of nitrogen. Sulphur and phosphorus appear to be necessary constituents also in the protoplasmic compounds ; the alkalies and earths are, in most cases, requisite in the processes of elaboration, but may, in many cases, be substituted for one another, and perhaps in certain cases may be replaced by ammonia. Potash is an indispensable element in plant-growth its presence being essential in the formation of starch from chlorophyll. Chlorine is necessary in many plants : iodine and bromine are also met with, particularly in marine plants ; but it is not clear whether their presence is necessary, or merely an inevitable result of the absorption of sea- water. Iron and manganese are met with very commonly, iron being essential to the formation of chlorophyll, and therefore of the utmost consequence to plant-growth ; copper and zinc more rarely ; silica abounds in certain Orders (Grasses, Equisetaceae), and is met with in many plants in smaller proportions. The most necessary ingredients for the clue nutrition of the plant are, in various proportions FOOD OF PLANTS. 557 according to circumstances, a nitrate or an ammonia salt, a salt of potash, soda, lime, magnesia, and iron, while lime is necessary in the formation of the cell-wall. These substances appear to act as ferments : for instance, lime is stated to effect the conversion of cane-sugar into cellulose, and to be influential in the transport of starchy materials in a soluble form. Sources of Nutriment. We have stated that (green) plants in general acquire their nitrogenous food by their roots (from the nitrates of the soil), and their carbonaceous food by their leaves. The sources of the food are therefore the soil and atmosphere in which plants grow ; and the inquiry presents itself at once as to the form in which the food is supplied to and taken up by plants. How Plants get their Food. On the one hand, we know that plants can absorb substances only in a liquid or gaseous form ; on the other, we know that both the atmosphere and the soil contain carbonic dioxide, water, and various nitrogenous compounds soluble in the latter. The alkalies, earths, &c. exist only in the soil, and in more or less abundance and in more or less soluble forms in different cases. Observation teaches us that the simpler plants, such as the Palmellea3, Lichens, many Mosses, &c., can grow upon bare rocks or stones, and obtain their carbon, hydrogen, oxygen, and nitrogen from the atmosphere alone ; and experiment shows that these are supplied in the form of carbonic dioxide, water, and ammonia; the substratum here supplies only the small proportion of mineral substance that is required. Moreover it is possible to grow a plant to maturity, and even to make it ripen its seed, in distilled water containing in solution only the ash-elements of aquatic plants, such as Confervas, &c. Similar growth may be obtained by growing a plant in a watery solution of the necessary mineral ; ingredients of the plants, together with a nitrate or an ammonia salt, the excess of carbon in these cases being derived from the air. Numerous and important results have been obtained by growing plants in experimental solutions of this kind water culture ; and . by their aid, as well as by field trials, it has become possible to compound artificial manures adapted to the requirements of parti- cular plants. Further, it is observed that, if a vegetation of this kind goes on undisturbed for a lengthened period, the decay of successive generations of plants leads to the accumulation of organic substance, in vegetable mould, the material of which has been derived from the atmosphere by the plants, but has not been consumed, i. e. decomposed into its original forms of carbonic dioxide &c., by them and their successors. From these facts it has been concluded, in the first place, and 558 PHYSIOLOGY truly, that green plants have the power of feeding upon inorganic substances, and fixing them in definite organic compounds : secondly, but with less justice, that this is the universal law of vegetable nutrition that plants live exclusively on inorganic sub- stances, which they convert into organic matters unfit for their own use, aud only assimilable after a new decomposition. In regard to certain plants this last assertion is altogether inadmis- sible, namely the Fungi, the so-called insectivorous plants such as Drosera, &c. (in which animal substances are dissolved, absorbed, and appropriated by the action of a ferment), and, above all, the colourless parasites ; and not only is it contradicted by the phe- nomena of their life, but it is opposed to the universal experience derived from observation of the cultivation of plants. Lastly, we know of no cause why plants should refuse to absorb organic substances presented to them in a state of solution favourable to endosmotic action in the roots. It is very true that many even of the higher plants will grow upon soil almost destitute of organic matters, as we see on sandy heaths &c. ; but the kind of vegetation which characterizes such soils is very different from that which clothes land covered with vegetable mould. And the influence of manures in agriculture must be attributed in a great measure to the extensive aid afforded to the plant in the shape of additional sup- plies of organic matters, which bear a kind of compound interest, since the increased growth they produce gives increased power of independent assimilative action. Spontaneous vegetation is nourished principally by carbonic dioxide and ammonia always existing in sufficient proportions in the atmosphere. The former substance is taken up by the leaves, and the latter is also absorbed by the aerial organs of plants : but the principal supply to the higher plants seems to be furnished through the soil, which receives ammonia dissolved in rain and dew, and, where porous, absorbs it greedily. Soil, and especially the carbonaceous portions, has also the power of absorbing ammonia from the atmosphere. Plants growing upon soil abounding in decaying vegetable and animal matters are doubtless supplied with part of their food from these sources. Ammonia is a constant product of decomposition of animal substance, carbonic dioxide of this and vegetable matter. But from the researches of Mulder it would appear probable that the old vegetable matters may pass into the living plants without undergoing decomposition into carbonic dioxide and water. The black decaying matter of vegetable origin, called humus, is decomposed in the soil into a series of organic acids, of which the last members possess much affinity for ammonia, and form both with it and the alkalies soluble salts, which may be absorbed as POOD OF PLANTS. 559 such by the roots. In favour of such a view is the fact that carbonate of ammonia, or ammonic carbonate (decomposable by crenic and apocrenic acids), appears in many cases hurtful when applied directly to the roots of plants. In addition to the ten- dency of these organic acids to attract ammonia, they seem to be capable even of causing its production in the soil, since in the progressive oxidation of humus taking place at the expense of water (H 2 O), the hydrogen of the latter possibly combines in its nascent state with the nitrogen of the atmosphere to form ammonia. It has been common in recent works to find the value of humous or carbonaceous matters in the soil estimated very low ; they have been regarded either as merely improving the (physically) absorbent power of soil, or as sources of carbonic dioxide, already sufficiently provided by the atmosphere. But the above observations, borne out by the experi- ments in Turnip-growing by Lawes and Gilbert, are in favour of a higher estimate of the value of decaying carbonaceous matters, and of regarding them as important constituents of farmyard manures for certain purposes. Lawes and Gilbert found that stimulating nitrogenous manures in excess were rather detrimental to the growth of turnips, leaf-formation going on at the expense of the roots ; but this was counteracted in a great measure by supplying, with the nitrogenous manures, carbonaceous sub- stances in considerable proportion. Corenwinder, however, states that the roots exhale carbonic dioxide and do not absorb it except in very minute quantities. Sources of Nitrogen. It was once supposed that there was a power in living plants to fix free nitrogen from atmospheric air ; but this is conclusively negatived by the experiments of Bous- singault, Lawes and Gilbert, Pugh, and others. That ammonia is not absolutely necessary for the food of plants is indicated by the effect of nitrates as manures, rivalling that of salts of ammonia. Moreover it has been stated that ozone (a peculiar condition of oxygen) converts ammonia into nitrous acid ; and there is reason to suppose that the ozone condition of oxygen is produced in certain cases in the liberation of that element by plants. Schlosing states that the ammonia supplied to the soil becomes (if light be excluded) converted in the soil into nitrates by the agency of a vegetable organism acting as a ferment. The amount of nitrogen supplied to the soil by rain is insufficient to account for the amount found in plants; but this quantity is sup- plemented by the direct absorption of ammonia by the leaves, as well as from the soil. Deherain supposes that decaying vegetable matter has the power of producing ammonia from the free nitrogen of the air; but his experiments have not been confirmed. Schlosing confirms the experiments of Sachs and Meyer as to the absorption by the leaves, and also by the soil, of gaseous ammonia, and corroborates the statements that the free nitrogen of the air is not available for plants except to the 560 PHYSIOLOGY. small extent in which, by thunder-storms and electrical disturbances, it is converted into nitrous acid, which latter becoming- oxidized, becomes carried down to the soil as ammonic nitrate. A large proportion of nitrate is lost by drainage, and ultimately finds its way into the sea, where it serves to nourish the marine plants, which in their turn feed the animals. These latter, in decaying, yield ammonia, the excess of which is volatilized into the air, which is thus continually supplied with ammonia, and diffused over the surface of the globe/ According to Schlosing, the ocean is the great source of com- bined nitrogen, ammonia forming the means by which it is conveyed to every part of the globe, supplying the requirements of the vegetable world. Berthelot considers that the nitrogen may be acquired from the atmosphere by electric action. Carnivorous Plants. One occasional source of nitrogen remains to be spoken of, for though, according to our present knowledge, exceptional, it seems probable that it is more general than it is at present proved to be. For many years it had been known that some plants, such as Pitcher- plants (Nepenthes), Sun-dew (Drosera}, Venus Fly-trap (Diomea), acted as fly-traps, retaining insects which alighted on them, but it was hardly supposed that these insects contributed to the nutrition of the plant. The experiments of Hooker, Darwin, Tait, Vines, and others have, how- ever, conclusively shown that insects and various animal matters are : 1, retained by viscid exudation, or, as in Drosera and Dioncea, by move- ments of the/ leaf-lobes analogous to acts of prehension in animals; 2, dissolved ; 3, absorbed ; and 4, appropriated to the requirements of the plant. The shape of the Pitcher-plants -p i(r> 5 g 8j (Nepenthes, Sarracenia, &c.) is evi- dently adapted to retain insects which may 'be attracted on or fall into them by accident ; and their conformation is such as to prevent their exit, while their intimate structure is such as to facili- tate dissolution and absorption. The lobes of the leaf of Drosera &c. are endued with sensitiveness, so that when an insect, or a piece of meat or albu- men, and, still more, a fragment of ammonia salt, comes in contact with the leaf, the lobes in question instantly begin to fold over and imprison the intruding substance (fig. 588), which gradually disappears, some or the whole of it being absorbed a process at- tended by retraction of the protoplasm from the walls of the cell in the shape of a ball (see fig. 590). It was further shown by Riess and Wills that the Leaf of Z>ro*em, showing the glandular Solution of these nitrogenous matters hairs on one half infolded over an insect. is dependent on the presence of a substance which acts like a ferment, and in the absence of which digestion does not take place. Gorup, Besanez, and Vines have shown that this ferment closely resembles that FOOD OF PLANTS. 561 of the peptic glands of animals, and is only efficient when associated with an acid ; so that the solution of nitrogenous matters "by the leaves, pitchers, and other organs of certain plants is now shown to be a true digestive process, resembling in every particular the corresponding pro- cess in the intestinal canal of animals. Ammonia salts have also been found to be rapidly absorbed, and to excite the sensitiveness of the plants to an extraordinary extent : still the actual benefit to the plant seemed doubtful ; for to ordinary observation these so-called carnivorous plants appear to thrive quite as 'well without Fig. 589. Fig. 590. Fig. 589. Cells of petal of Helleborus prior to application of meat. Fig. 590. Cells of petals of Helleborus after the application of meat. as with nitrogenous diet. To settle this point, Mr. Francis Darwin experimented on a large number of plants of Drosera grown under like conditions, half of them fed, the other not receiving artificial supplies. The general result, given in the following Table, shows the great benefit derived by the fed plants, especially in the formation of seeds : Results of Experiments on Drosera. Unfed. Fed. Total weight of plants, excluding flower-stems 100 122 Total number of flower-stems 100 16-5 Sum of heights of flower-stems 100 1GO Total weight of flower-stems 100 232 Total number of capsules 100 194 Average number of seeds per capsule 100 123 Total weight of seeds 100 242 Total number of seeds 100 380 Sources of Mineral Food. For their mineral food, plants are of course chiefly dependent on the soil in which they grow. The gradual decomposition of rocks furnishes the earthy and alkaline constituents, which must vary on different formations or according to diluvial actions. Marine plants naturally accumulate many of 562 PHYSIOLOGY. the mineral elements of sea-water : and plants growing near the sea derive a certain amount of the salts of sea-water from the atmosphere, brought by the winds ; the salt spray is shown to be carried great distances by its being injurious and destructive to many kinds of plants growing exposed to sea- winds. Sect. 4. ABSOEPTICXN-. Since the lower plants consist of closed cells, in the interior of which their vitalized substance resides, and the membrane of their cells, so far as our investigations can reach, is, in general, desti- tute of orifices, the food of these plants can only be taken up in a liquid or gaseous condition by the still mysterious process of imbibition. In plants of more complex organization, although loose parenchymatous tissues exist, and the interspaces become concerned in at least secretion, the external surface of the plant, by which food must penetrate, is care- fully guarded by a continuous epidermis, entirely devoid of orifices in the roots, the principal absorbing organs ; and though perforated by stomatal orifices in the leaves and other aerial organs, these are carefully guarded by special contrivances to prevent the entrance of solid matter, and in all cases lead merely to intercellular passages, external to the membranes of the vegetable cells. Absorption in Cellular Plants. In the Fungi and Algae ab- sorption appears to take place freely at all points of the thallus to which gases and liquids have access. The structure of Mosses, Hepaticse, and the smaller members of the higher groups of Cryp- togams are likewise so simply cellular that they appear to be little dependent on root-structures. Absorption in Vascular Plants. In the higher Cryptogamia and the Phanerogamia the absorption of liquids appears to be confined to the roots and the root-hairs, the epidermis of the leaves &c. being in general so organized as to oppose the entrance of water, while the stomatal cells which guard its orifices, swelling up so as to close the slit between them when filled with fluid, concur to prevent the absorption of water or other liquid. Gases, however, penetrate freely through most cell-membranes, and hence may be absorbed by leaves, and can pass freely through the stomata into the intercellular passages. Osmosis. The physical phenomena of diffusion and osmose are the most important agents in the acquisition, by the cell-contents, of material from without. These phenomena depend, 'first, on adhesion of the liquid to the solid, and then on any circumstances which cause movements in the molecules of the liquid, such as the attraction one for the other of two fluids of different natures and densities. We may say, in g-eneral terms, that when two liquids of different den- sities (the* one "colloidal," or little diffusible, the other "crystalloid" or ABSOEPTIOtf. 563 greatly diffusible) are separated by a membrane or other porous substance, the denser liquid becomes increased in bulk by the passage of the thinner liquid into it through the membrane. This rule is indeed subject to modifications, dependent upon other qualities besides density of the liquids, such as their molecular relations to the substance of the separating membrane, the molecular nature of the membrane itself, &c., since, of two different liquids, that which is more readily imbibed by the membrane passes through in a preponderating current. When we place simple vegetable cells with flexible cell-membranes, such as many pollen-grains, yeast-globules, &c., in water, their dense cell-contents absorb water and the cell-wall expands, sometimes even bursts. On the other hand, placed in strong solutions of sugar or gum, such cells will lose part of their contents and shrink. But these simple experiments are not sufficient to indicate what takes place in the cells of tissues tilled with living protoplasmic matters ; for very frequently, when we place such cells in liquids differing in density from their contents, there ensue successive changes of condition, which must also be involved in many natural processes. Thus if we place in water a fragment of cellular tissue from the region where pollen-grains are being developed in the anther, or spores in sporanges, water is absorbed through the cellulose coat, but the primordial utricle contracts; but when the water pene- trates the latter, it swells again and sometimes expands beyond its original volume, bursting the cell-membrane when this is weak. " The presence of a membranous or porous septum is not essential to such a process of nitration and admixture as above described. Two liquids of different densities placed in contact will gradually mix by the attrac- tive force that the one exerts on the other. This liquid diffusion depends materially in amount on the nature of the liquids colloid or crystalloid, as the case may be. Selecting power. The recognition of endosmose as the cause of the absorption of liquids by the young roots and root-hairs affords some explanation of the apparently contradictory phenomena which have been described by those who have experimented with a view to ascertain whether plants have any selecting power. It has been shown that there exist some very complex circumstances of purely . ! physical nature in endosmotic processes, and that simple density of liquids is by no means the only important point alkaline, acid, or neutral conditions of mineral salts causing special peculiarities, dependent on chemical and molecular relations to the membrane or : porous interposed substance, and in other cases on chemical actions taking place on one or the other side of the membrane. One of the most interesting and suggestive experiments bearing on this subject is that of Knop, who shows that the more chlorine absorbed by a plant the less lime is taken up. Some writers assert that the roots of plants absorb all substances in- differently ; and the experiments of Vogel and others appear to bear this out. But, not to mention that the ashes of different plants grown in the same soil have diiierent composition, Trmchinetti has shown that different 564 PHYSIOLOGY. salts are absorbed in different proportions from mixed solutions ; and in Be Saussure's experiments living roots absorbed differently from diseased or dead ones. Similar inferences may be drawn from the effects of manures : thus Cereals are specially benefited by nitrogenous manures, Leguminous plants by mineral manures ; and yet the ash-analysis of the former shows that they contain a less percentage of nitrogenous matters than do the Leguminosae. Wheat crops and grasses generally, according to the experiments of Lawes and Gilbert, supply themselves with diffi- culty with nitrogen, while Clover and other Leguminosee take it up freely. Such phenomena as these, however, may be explicable on purely phy- sical principles. It has been proved that different chemical salts exhibit unlike quantitative phenomena in passing through dead endosmotic sub- stances ; and thus even from mixed fluids one salt might pass more readily into a cell than another j and, still more, the immediate decomposition of one salt alone, inside the membrane, while the other was not affected, which might take place in a living cell, would greatly affect the endos- mose, since the cell-contents would soon be saturated with the latter, while the other would not accumulate. According to Knop, the roots will absorb from solutions of nutritive salts an amount proportionate to the degree of concentration of the solution : thus the stronger the solu- tion the more dilute the liquid absorbed by the root ; on the other hand, if the solution be less concentrated, the root will take up a relatively larger quantity of water than of the salt. In regard to De Saussure's experi- ments (which are borne out by what we see beneath the microscope when we apply reagents, such as iodine, to healthy or decaying tissues), there is no necessity to have recourse to a vital agency of' selection, since the chemical activity of the cell-contents, quite different in a living and in a dead organism, might account for all the diversities, even if the difference could not be explained by a physical difference of tension in the living cell-membrane and that of a dead organ, in which a process of decay im- mediately commences if it is exposed to the action of water. It has recently been shown that porous vessels placed in mixed solu- tions select, just as plants do under similar circumstances; and those solutions which pass most freely through the walls of cells are those which always pass most freely through the sides of the porous vessels. Those cases' in which the same amount of any given substance is capable of being absorbed by plants which have nevertheless different chemical composi- tion, may also be explained by the different osmotic powers possessed by the cells of different plants. Thus, supposing the root-cells of a Cereal plant and those of a Leguminous plant to take up the same amount of silica from the soil, the quantity of that ingredient would speedily be found to be greater in the Cereal than in the Leguminous plant, because the cells of the former can appropriate silica, and by osmosis store it up in the epidermal tissues, while the cells of the latter, having different osmotic relations to silica, soon become saturated and can take up no more. On the same principle we see cells in juxtaposition containing very different ingredients, which yet do not mix because the conditions for'endosmosis are in some way or other not favourable. Influence of Evaporation. Schlosing says that the power of absorbing mineral ingredients from the soil is diminished by limiting the process ABSOEPTION. 565 of evaporation, as when plants are grown under a bell-glass. Rauweii- hoff also states that absorption exceeds transpiration in amount in propor- tion as the pressure is greater, and where the latter is slight evaporation is in excess. Root-action. It has been shown that absorption of fluids takes place near the extremities of the finest rootlets above the inert root- cap, and by means of the root-hairs. But the water in the soil is often nearly pure water, or, at least, contains little admixture of mineral matter, though more or less impregnated with gases. Again, many of the ingredients of the soil, such as silica for in- stance, are insoluble in pure water. How then do these substances gain access, as we know they do, to the interior of the plant? They must be derived from without and in a liquid form. The explana- tion now given is, that the minute rootlets and root-hairs insinuate themselves between the particles of soil, absorb the water there situated with its minute proportion of dissolved mineral matter. Further, these root-hairs come into close contact with the minute particles of soil, and, by virtue of some processes of excretion not yet thoroughly examined, they excrete a substance, gaseous or liquid, which effects the solution of the mineral substance in the particle of soil. An exhalation of carbonic dioxide from the roots, con- joined with the water in the soil, would effect the solution of lime, for instance. In this way the furrows and impressions on the sur- face of marble made by roots is explained. The opinion that root excretions exist, at one time denied, may thus be correct ; but as they appear to be only excreted when required, and are used up in the process of solution, their presence in the soil is not manifested any more than that of the gastric juice in an empty stomach. Absorption by Leaves. The leaves and other green parts of the higher plants do not appear, as a rule, to absorb liquids all the time the roots are in action, but if root-absorption be insufficient then absorption by the leaves takes place. The good effect of syringing plants in hothouses seems rather to depend on the check given to undue evaporation than to absorption, the structure of the epidermis being generally unfavourable for that process. Whether leaves absorb even watery vapour to any great extent is question- able ; but it is certain that they absorb gases, including ammonia, though, under ordinary circumstances, only in very small quantities (Mayer), and that a very large proportion of the carbon which is consumed by green plants is taken into the system, in the form of carbonic dioxide gas, by the leaves and green shoots. The entrance of gases into the cells is attributable, through their solubility in water, to endosmotic action ; while the laws of diffusion of gases provide for their entrance into the intercellular passages, which brings them into contact with the deeper-seated cells. 566 PHYSIOLOGY. Sect. 5. DIFFUSION OF FLUIDS IK PLANTS. Diffusion in Aquatic and Cellular Plants. In aquatic plants the entire surface is employed in absorption ; and the liberation of gases in the respiratory or other processes being accompanied by condensation of the cell-contents, endosmotic action is kept up constantly during active vegetation. In the Cellular plants, such as Lichens, Fungi, and even in Mosses and Hepaticse, the diffusion of the fluids would appear to be a result of simple endosmotic action continued from cell to cell in more or less complex series ; and in plants growing in air, evaporation of gases increases the density of the contents of the last or uppermost cells of the chain. Diffusion in Vascular Plants. In plants with well-developed stems and roots, the liquid nutriment is absorbed by the latter, and the movements which the absorbed fluids have to make are much more complex, not only from the greater variety of forms of tissue through which they have to pass, but from the multiplied details of the interchanges with elaborated matters arising from the scattered distribution of the leaves over the axis. Ascent of the Sap. As so large a quantity of water is absorbed by the roots from below, it is clear that the diffusion of that fluid (or sap, as it is now called) must in the first instance be in an upward direction ; hence the phrase ascent of the sap. The main current of the watery sap, is upwards from the root, through the stem and branches, to the leaves, wherein, owing to the changes it there undergoes and which will be hereafter alluded to, its cha- racter becomes altered and the direction of its current is varied according to the requirements of different parts of the plant, &c. The term sap is retained for convenience' sake ; but it must be remem- bered that there is no homogeneous fluid, either ascending or descending, crude or elaborated, of similar constitution in all parts of the plant, cor- responding to the blood of animals. The sap varies in constitution in different parts of the same plant at the same time. In like manner there is no continuous system of tubes in which sap could "circulate." In sprino-, when vegetation is most active, or, at other times, when special circumstances favour growth in particular places, a current of watery sap, containing relatively little of the matters formed in consequence of leaf- action, is specially manifest ; and as the ends of the shoots and buds are at this period centres of activity, so the flow is mainly an upward one. In autumn, when consolidation of tissues and storage of nutritive matters are the chief operations of the plant, there is an increased necessity for the presence of matters formed in consequence of leaf-action, and the flow is to a large extent a downward one. But there is no absolute difference between crude and elaborated saps, and no absolutely fixed course for them to take. The ascending sap, so called, which is so manifest in DIFPUSION OF FLUIDS. 567 spring, consists principally of water pumped up from the roots to supply the requirements of the growing cells, and the excess of it is evaporated when the leaves expand ; but though mainly watery, it contains some mineral matters, and also some ingredients which must be derived from the action of the leaves of the preceding season. The upward direction of the watery sap, therefore, and still more the downward current of the elaborated sap, must be understood in a general sense as indicating the prevailing direction of the currents. A more strictly correct expression would be to say that the sap, including all the liquid nutritive juices of the plant, moves in the direction in which cir- cumstances are most favourable to its flow, and to those spots where the sap is most needed for the nutritive processes of the plant, or for purposes of storage, as will be more fully explained in succeeding paragraphs. Causes of Ascent. The causes producing the ascent of the sap are manifold. They vary not only in their nature, but, at different times, in different .parts of the same plant and under varying cir- cumstances. They act also separately or in conjunction. We will first of all allude to the inducing causes separately, and then indi- cate how, when, and where they act. Emlosmotic action consequent on the absorption of fluids by the root is on all hands admitted to play the principal share in the diffusion of fluids throughout the plant. Capillary action and Imbibition facilitate the upward pas- sage in or between the iibro-vascular tissues. Pressure, whether exerted by the tension of the cell-walls upon their contents, and itself consequent on endosmosis, or as the result of increased tem- perature, which expands the air in the stem, forces the fluids to move in the direction of least resistance. The oscillations produced by the swaying of the branches, petioles, &c. by the wind also occasion intermittent pressure, to which Mr. Herbert Spencer attributes an upward thrust of the sap towards the point of least obstruction. The profuse evaporation or transpiration of watery vapour from the leaves is a powerful agent in producing an upward flow of fluid to replace that which is lost in the manner indicated. The extra- vasation or exudation of sap consequent on the mechanical strains effected by the wind also give rise to a current of sap from below. Chemical actions, such as the transformation uf starch into sugar &c., necessitate a supply of water and create osmotic currents of that fluid. Force of upward current. The roots take an important share in pro- moting the upward flow of the spring sap. If, in spring, we notice the surface of stumps of timber-trees which have been sawn off" in the pre- ceding autumn, we find the cut surfaces wet with abundant exudation from the outer layers of the wood ; and experiments made upon the cut ends of branches, by Hales and others, show that the sap rises in them with very considerable force in the case of the Vine, supporting a column of mercury 26 inches in height. Clarke's more recent researches indicate 568 PHYSIOLOGY. a still greater force, as, in one case, in a Vine he found the force of ascent sufficient to balance a column of water 48-50 feet in height. The quantity obtained from a Birch tree 75 feet high, from November to May, was 1486 lb., in one day 63 Ib. being collected. The force and amount are subject to diurnal variations. It is evident that the spring current, at least, is partly owing to absorption by the roots, in the cells of which decomposition and solution of starch are effected, and which must in con- sequence absorb water greedily ; the engorgement of the tissues may cause the liquids to be forced into and upwards along the course of the vessels and ducts. In woody stems osmose also comes into play in conjunction with capil- lary action and pressure dependent on the various causes before named. Pressure resulting from increased temperature is illustrated by the cir- cumstance that the flow of sap in the trunks of trees is greatest during the daytime, when the trunk absorbs the sun's heat by its rough surface, and least at night, when the tree is cooled by radiation. In the leaves the transpiration and the movements effected by the wind afford the main causes for the rush of sap. In the expanding leaf-buds, and in all por- tions of the plant where vegetation is going on actively and where in con- sequence large quantities of nutriment are required, the chemical trans- formation of the cell-contents, which renders them available for nutri- tive purposes, necessitates a large quantity of water ; and in consequence an endosmotic current is produced. This chemical action does not neces- sarily occur at the very point where growth is most active, generally, in- deed, elsewhere, in what may be termed the store-cells, so that a current is determined from the store-cells to the growing points. The transfers just alluded to may be compared to a row of firemen handing on pails of water, in the absence of a hose or continuous pipe, such as is represented by the blood-vessels of an animal. The spring ascent of sap in Dicotyledons is partly to be accounted for by the solution of starch, or the decomposition of fixed oil &c., in the buds and cambium-region, as above mentioned (just as occurs in the root or in a seed beginning to germinate). But, as has been observed by VonMohl, the inspissated juices thus formed do not lie in the sap-wood wherein the ascending current flows, but in the cambium-layers, where the elaborated sap descends ; and it is not clear why the ascending fluid, if moved by endosrnose alone, does not pass out laterally into the cambium as soon a*s it reaches the stem. That the buds, however, do exert this attractive force is seen by the influence of the heat of a greenhouse in causing the flow of sap in a Vine which is planted with its roots outside the house, and its stem brought inside and trained there. Transpiration. In the leaves (and green portions of plants generally) the very important phenomena of evaporation or trans- piration o watery vapours occurs, and constitutes probably the most important agent of all in causing the supply and diffusion of food in plants. It has been stated above that plants absorb their liquid food by their roots ; therefore, under equal external condi- tions, a plant should receive the nutrient matters derived from its liquid food in the ratio of the quantity of water passing through its tissues and evaporated from its leaves &c., since the water DIFFUSION OF FLUIDS. 569 passes off almost as pure vapour, and, at all events, leaves its mineral constituents behind. The amount of evaporation is re- markably great, and accounts in some degree for the sustenance of plants by such extremely dilute solutions of their nutrient matters as they find in the soil. Amount of Transpiration. The experiments of Lawes and Gilbert give the following average daily loss of water in grains in the months indicated, in pots of unmanured soil, the first line from Wheat, the second from Peas : March 19th March 28th April 28th May 25th June 28th July 28th Aug. llth to to to to to to to March 28th. April 28th. May 25th. June 28th. July 28th. Aug. llth. Sept. 7th. 14-3 40-9 162-4 1177-4 1585-3 1101-4 230-9 11-2 42-9 106-4 1079-8 2092-7 377-2 The total amount of water given off during the whole period of 172 days (March 19 to Sept. 7) was, by the Wheat, 113,527 grains, by the Peas, 109,082 grains. The total quantity of mineral ash from each of the samples was, Wheat, 36-49 grains, and Peas, 43-16 grains, which shows that the Wheat took up 32-14 grains and the Peas 39-57 grains of mineral matter in every 100,000 grains of water which evaporated from it. Other elaborate experiments of the same observers, recorded in the Journal of the Horticultural Society for 1851, show that evergreen trees transpire less than deciduous trees, and that great differences are manifested in different plants according to temperature. The maximum of evapora- tion does not always coincide with the maximum temperature. It was also found that plants cultivated without manure frequently evaporated more than those to which manure was applied ; and, further, that under a purely mineral manure more water was transpired than when a mixed mineral and ammoniacal manure was used, so that the more abun- dant the food the less water transpired. Deherain shows that, as a rule, the amount transpired is greater from the younger than the older leaves. Haberlandt, in his experiments on this subject, shows that young grow- ing Cereals before the period of flowering transpire most, and least of all after that process, the relative proportion of root or absorbing organs as compared to transpiring organs being then greatest. The four plants examined by M. Haberlandt evaporated in 24 hours per 100 square centi- metres during the whole period of vegetation (90 days) as follows : Barley 3794, Wheat 3532, Rye 2849, Oats 2666 grammes. But con- sidered in relation to the surface of the plants, the Oat evaporated 2277, the Barley 1236, the Wheat 1179, and the Eye 834 grammes per plant during the same period. Supposing a million plants on a hectare (a hectare =2| acres about), the loss of water, according to the above calcu- lations, over that amount of surface would be : Rve 83,490, Wheat 1,179,920, Barley 1,236,710, and Oats 2,277,760 kilogrammes, which corresponds to a rainfall respectively of 83-5 millimetres, 118 millims., 123-7 millims., and 227*8 millims. In all cases great variations, both as to absorption and transpiration, occur in different individuals of the same species. 570 PHYSIOLOGY. Circumstances regulating Transpiration. The amount of transpiration depends on the amount absorbed, the quantity of water in the tissues, the age of the plant, the amount of surface exposed (Asa Gray calculated that a moderate sized Elm-tree bore seven millions of idRves, the total surface being equal to 5 acres), the nature of the epidermis, the texture of the leaf, &c. : thus it is usually greatest from the lower surfaces of leaves, which are provided with the greatest number of stoinata. External conditions, such as the degree of moisture in or the temperature of the air, exert great influence on transpiration ; the drier and hotter the atmosphere, the greater the transpiration ; but, according to McNab, plants exposed to the sun transpire most in a moist atmosphere, while in the shade transpiration ceases when the atmosphere is loaded with watery vapour. Light also has great effect on the quantity evaporated. McNab's experiments, however, show that the rate of ascent of the watery sap is not checked by placing the branch in darkness for a short time. M. Wiesner shows that part of the light which traverses the chlorophyll is transformed into heat, as a consequence of which there results a rise of tem- perature, and an increased tension in the watery vapour in the inter- cellular passages occurs. The excess of vapour escapes by means of the stoinata. A plant may, as shown \)j McNab and Deherain, transpire in a saturated atmosphere, but only under the influence of light. M. Wie^ner has studied transpiration in three different ways: 1, by comparing that of green plants with that of blanched ones ; 2, by exposing the plants in the solar spectrum ; and 3, by placing them behind solutions of chlorophyll. By these different ways, he has arrived at the same results, viz. : that the presence of chlorophyll markedly increases the action of the light on transpiration; that it is the rays which correspond to the absorption-band of the chlorophyllian spec- trum, and not the most luminous rays, which excite transpiration ; and lastly, that the rays which have traversed a solution of chlorophyll have only a slight influence on transpiration. Other colouring-matters, as xan- thophyll, for instance, may act in the same way as chlorophyll, but to a less extent. The opening of the stomata may accelerate the transpiration ; but the very marked transpiration of young Maize plants, the stomata of which were closed, and the slight transpiration of a Hartwegia comosa, the stomata of which were widely open in obscurity, suffice to show that this cannot be the principal cause of the transpiration in the light. In a very positive manner, but in a less degree than in the case of the luminous rays, the obscure calorific rays act. As to the chemical rays beyond the violet their action is null or very slight. Whatever may be the nature of the rays, they always act in raising the temperature of the tissues. In spring, before the expansion of the buds, absorption is necessarily greater than transpiration ; the water in such a case is stored in the stem, wheie it is made available for the expanding buds and growing tissues generally. In summer the transpiration is greater than the absorption ; and then the leaves depend for their supply on the stores in the stem, or, failing that, they wither. Even in winter, provided the stem be not absolutely frozen, there is a motion of the juices, dependent to a great extent on the temperature of the soil, which is always in that season higher than that of the air, and it increases in amount from the surface down- wards. DIFFUSION OF FLUIDS. 571 The relation of the composition of the fluids of the plant to the amount of transpiration has lately been studied by M. Burgenstein, by growing plants in saline solutions, taking care to prevent all evaporation except from the leaves of the plant, and then weighing the apparatus and plants daily so as to estimate the loss. Acids were found to increase the evaporation, alkalies to diminish it, other things being equal. Saline solutions act vari- ously, according to the nature of the salt and the concentration of the solu- tion,transpiration attaining a maximum at a certain degree of concentration and diminishing after that. In a mixed saline solution, or complete nutri- tive fluid, however diluted, the quantity of water transpired is invariably less than when the plants are grown in distilled water. Tissues through which the Sap flows. As regards the special tissues through which the sap flows, the experiments of Hoffmann and others indicate that a very uniform diffusion of fluids takes place in the Cellular plants and in the Mosses. But the last- named physiologist found that in the plants possessed of fibro- vascular bundles, the fluids passed up in the first instance from the roots chiefly in the prosenchymatous cellular constituents or soft bast-cells of the bundles. These experiments were made by causing the plants to absorb potassic ferr.ocyanide ; and then, by treating sections of them with a per-salt of iron, the course of the sap was shown by the local appearance of Prussian blue. Unger's experiments, in which he caused plants to absord the red juice of the berries of Phytolacca, gave the same results. As a rule, it was found by both observers that the fluids did not pass by the spiral vessels them- selves, unless the continuity of the absorbing surface of the roots had been destroyed. Herbert Spencer's experiments, however, show that the passage through the vessels is much more rapid than through the cellular tissue. Where cut branches are caused to absorb, the fluids rise in the open vessels and ducts by simple capillarity. In McNab's experiments the ascending current was found to pass only through the woody portion of the nbro-vas- cular bundles and not through the liber. The spiral and other vessels do not always participate in the diffusion of the juices ; but in the commencement of the growing-season (with us, in spring), the whole tissue becoming gorged with fluid, the vessels are com- monly found full of sap. In the regular steady course of vegetation the spiral vessels are usually found filled with air. The intercellular passages are also filled with air, except under peculiar circumstances, and therefore take no part in the distribution of the sap. The experiments which have been made to ascertain the course of the fluids absorbed by the roots, tend to show that the sap passes upward in the elongated cells associated with vessels in the fibro-vascular bundles, towards and into the leaves and other organs. The distribution of the fluids must therefore be very different in stems differently organized as regards the arrangement of these bundles. In Monocotyledons we find a series of isolated streams ; in Dicotyledons the fluids ascend in a much freer and wider course, in the more abundant wood of the regularly ar- ranged circle of bundles. A further diversity arises from the changes which take place in stems with age : in Dicotyledons the inner layers of wood 572 PHYSIOLOGY. generally become converted in the course of time into heart-wood, the solidity of which obstructs the passage of fluids, which then ascend chiefly in the outer, younger layers of wood, which constitute the alburnum or sap- wood. This is illustrated by the vegetation of hollow Dicotyledonous trees, in which a sufficient layer of young wood remains within the bark to carry up the absorbed fluids. It is found that the careful removal of the heart- wood of trees does not prevent the supply of liquid to the branches from the roots ; but if the layers of sap-wood are removed, the upper parts of the tree die from desiccation, even when the bark is left uninjured except to such an extent as is sufficient to allow of removing the wood beneath. The removal of a ring of bark does not prevent the ascent of fluid, but, as will be noticed presently, arrests the downward distribution. A certain amount of lateral diffusion takes place from the as- cending current, supplying the surrounding tissues with water, and, perhaps, nitrogenous materials ; but this point is not clear. Crude Sap. The fluid which is found in the sap-wood of Dico- tyledons is of a watery character, containing dextrine and sugar, but not starch, chlorophyll, or any colouring-matter. It may contain matters dissolved out in its course through the tissues, and thus have a nutritive character from the admixture of matters stored up in the previous season in the wood-cells, &c. It contains also mineral salts absorbed by the roots, in an undecomposed condition, at consi- derable heights in the stem. This fluid is called crude sap. and occurs in especial abundance at the time (spring) when the renewed chemical activity in the developing cellular tissues causes an in- creased absorption of fluids. This crude sap flows out freely from incisions into the sap-wood of Dicotyledonous trees in spring, and sometimes spontaneously bursts forth in a kind of overflow, as in what gardeners call " bleeding" of Vines, Birches, &c. The crude sap becomes more and more condensed as it ascends in the stem and other organs. In the leaves and other green parts it undergoes a most important transformation, loses by transpiration much of its water, and receives a new element in its composition, of the highest importance to it as material for development, namely carbon, derived from the car- bonic dioxide absorbed by the leaves and decomposed there in sunlight, with the liberation of oxygen. Descending Sap. The nature of the progress of the sap from the leaves into the cambium-region of the stem and other parts is at present obscure. Some authors, indeed, totally deny that the elaborated sap descends at all; but this is in contra- diction to all experience and observation. All experiments which have been made favour the opinion that there is a descent of sap elaborated in the leaves, in Dicotyledons at least, in that part of the fibro-vascular bundles coinciding with the cambium-ring of the DIFFUSION OF FLUIDS. 573 stem that is, in the cambium-layer of the wood and in the in- ternal tissue of the bark. This supplies the material for the de- velopment of new wood in the fibro- vascular layers ; and this elabo- rated sap evidently passes not only downward through the latticed vessels, sieve tubes, vasa propria, and conducting cells, but inward, by lateral transmission (since we find in autumn starch-granules laid up in the medullary rays between the wedges of developed wood), and also upwards when growth is going on, or where reserve material has to be accumulated. The sap therefore is transferred from place to place in varying directions in Dicotyledons, not in a proper system of vessels, but by a series of disturbances and restorations of equilibrium in a mass of permeable tissues. The changes are dependent upon local phy- sical, chemical, and developmental actions. The evidence of a descent of elaborated sap is overwhelming. The simplest proof, that of removing a ring of bark, which causes the arrest of development of wood below the ring, is borne out by all variations of it. Ringing fruit-trees in this way causes a swelling of the tissues and a temporary increase of product of fruit above or on the distal side of the wound, from the accumulation of the elaborated matter. The formation of tubers in the Potato and similar plants is prevented by interrupting the continuity of the cortical layers; and when hark is removed in patches, and the surface becomes gradually grown over by new wood, the greater part of the new growth comes from the upper side. Still a descending current is not the only direction in which nutritive fluids flow ; for, as has been already stated, the flow mav be in any direction, and new wood may be formed in place without immediate connexion with any descending current. It is Mulder's view that all the nitrogenous constituents of plants are not only absorbed by the roots, but assimilated there at once, and that carbon is fixed in the green organs then, that a continual interchange goes on from above and below, the roots supplying protoplasmic matters which originate all organic phenomena, while the leaves send down the ternary compounds (C H O) which afford the material for cell-membrane, starch^ &c. This author attributes the distribution to simple endosmose ; hut this does not account for the passage of crude sap through the albur- num, and of elaborated nutriment through the inner bark. Other authors consider that organic substances (carbo-hydrates, albuminoids, &c.) are formed in the leaves ; in such a case a descent of the sap must of neces- sity occur. The transfer from one leaf to another of such substances as glucose, albumen, phosphates, &c. may be accounted for by evaporation. Sachs states that the elaborated sap in the cellular tissue is different from that in the vascular ; " the parenchymatous tissues have," says he, " an acid sap, containing sugar, starch, oil, vegetable acids," &c. The vascular and prosenchymatous tissues, including the " vasa propria " and clathrate cells and other elements of the soft bast, have an alkaline sap. The sap passing through these tissues is of an albuminous or nitrogenous nature. Other physiologists, however, doubt whether any such sharply defined dual nature of the elaborated sap exists, though admitting the large share 574 PHYSIOLOGY. which the vasa propria fill in the descent of the elaborated juices. It is clear, however, that the currents of the sap must vary according to the different anatomical disposition of the tissues. Summary. We may conclude by repeating that the nutrient fluids in plants follow certain directions, according to the structure and arrangement of the tissues, the place where evaporation is most active, the locality of the sources of nutriment and of growth or other action ; and that as regards the elaborated fluid the movement may be, 1, from the place of formation to that of consumption, or, 2, to the store-cells or reservoirs, or, 3, from these latter to the place of consumption. The ascending, descending, or horizontal direction of the currents is therefore a secondary matter. To illustrate the movement and transference of nutrient matters, allusion may here be made to the researches of M. A. Gris on the pro- duction and utilization of starch, &c. This observer finds that in winter- time the medullary rays, wood, and pith are all filled with starch-grains. These diminish in spring 1 , but are afterwards replaced during the summer. He concludes from this that there are two special movements of the nutrient substances, as illustrated by their formation in summer and their absorp- tion in the following spring. Sect. 6. ELABORATION OF THE FOOD. Exhalation of Oxygen. When green plants are placed in water containing dissolved carbonic dioxide, and exposed to sunlight, they give off oxygen gas. This may be readily observed in Vattisneria and other submerged green plants grown in glass jars, a continuous stream of bubbles escaping from the plants when standing in the sunshine. The frothy masses of Con- fervse, borne up to the surface of freshwater pools in sunny weather by the entangled bubbles of oxygen, afford another common instance. The absorption of carbonic dioxide, and the elimination of oxygen in the case of aquatic plants, and also in that of leathery leaves as in the Cherry Laurel, where tnere are comparatively few stomata, take place chiefly or entirely on the upper surface. Where no carbonic dioxide exists, as in boiled or distilled water, no oxygen is liberated. Leafy shoots remaining attached to trees, but en- closed in close glass globes," increase the percentage of oxygen in the globes when exposed to daylight ; and cut shoots with the lower ends placed in water containing carbonic dioxide in solution give off more oxygen than when the lower ends are dipped in water devoid of that gas. The oxygen exhaled by leaves &c. is formed at the moment of its liberation; for Confervse, which have no air-passages, and other plants which have had their air-passages exhausted by the air-pump, give off oxygen under the above circumstances. Fragments of loaves perform the Bafne function so long as their organization is uninjured, while the de- struction of the cells by pressure &c. stops the action. The epidermal cells exhale no oxygen. ELABORATION OF FOOD. 575 Effect of various Rays of the Spectrum. The unlike influence of the different rays of the spectrum is very remarkable. According- to Daubeny and Draper, whose observations have been confirmed by numerous ob- servers, sunlight acts in proportion to its illuminating po'wer in the de- oxidating process, which appears to be just the reverse of what occurs in the reducing action of light upon silver. The yellow rays are almost as powerful as white light ; while the more refrangible rays, blue, violet, &c., have little or no effect on the emission of oxygen, though it is pro- bable they may exert great influence on the chemical transformations which follow that process, and have a directly favourable influence on heliotropic curvatures, periodic movements, currents of protoplasm, &c. (Pfeffer, Baranetsky). In green light the leaves emit carbonic dioxide gas, as in darkness. Diffused light is rich in the more refrangible rays, and hence causes a scanty emission of oxygen. Prillieux, however, asserts that the amount of oxygen emitted by light of different colours is in di- rect proportion to their illuminating-power, and that the effect of the vel- low and red rays in causing the disengagement of oxygen is due to ttteir luminous intensity. A corresponding fact has been noticed with regard to the evaporation of water, so that the two phenomena would appear to be in some way connected. It has been found that starch is formed under white, yellow, or blue light, but in different proportions and with different degrees of rapidity, its formation under the influence of blue light being much slower than under white light. Quantity of Oxygen. The quantity of oxygen given off bears a definite proportion to the carbonic dioxide absorbed by a plant ; but excess of carbonic dioxide becomes obnoxious to health. Elimination of Nitrogen, &c. It would appear that nitrogen is also given off by plants exposed to sunlight. Draper observed considerable quantities exhaled ; and Cloez and Gratiolet noticed more than was attributable to air accidentally present in the inter- cellular passages. According to Corenwinder the proportion of nitrogenous matter and phosphates gradually decreases from the time of the opening of the leaves till their fall. Boussingault asserts that in the case of marsh plants a small proportion of carbonic oxide is exhaled by the green parts of plants, but probably not under normal comditions. Elimination of Carbonic Dioxide. When the influence of the sun is withheld from green plants they cease to give off oxygen ; carbonic dioxide is now not absorbed but exhaled, oxygen being absorbed from the surrounding medium. Some entire plants destitute of chlorophyll (Fungi and parasites) and certain parts of most others (buds, roots, flowers, germinating seeds, &c.) absorb oxygen at all times and exhale carbonic dioxide, and thus become, like animals, an apparatus for the combustion of carbon and hydrogen. The carbonic dioxide given off from the interior of stems, roots, 576 PHYSIOLOGY. &c. by day is probably reabsorbed and decomposed in the green parts before it arrives at the surface of the leaves. According to De Saussure, if a plant is kept in a perfectly closed jar containing a measured quantity of atmospheric air, for several days and nights (an equal number of each), no change is found in the volume or composition of the air ; the plant has exhaled oxygen by day and absorbed it by night, and exhaled carbonic dioxide by night and decomposed it by day, in equal proportion. But if this plant is watered with solution of carbonic dioxide, or this gas be added to the air, the quantity of oxygen in the air becomes increased. Under ordinary circumstances the leaves decompose by day much more carbonic dioxide than they exhale by night. The disengagement of oxygen has been observed in some aquatic plants to go on in the dark for some hours after exposure to the sun. The sun's light is thus stored away in the plant and rendered available in some form or other when wanted. If plants are placed under such circumstances that they cannot decom- pose carbonic dioxide and exhale oxygen (hy excluding light from them, or by confining them in vessels deprived of carbonic dioxide), they never acquire proper development ; no green colour appears (they are etiolated), little or no woody matter is formed in the walls of the cells, and the whole energy is consumed in pushing out weak watery shoots j scarcely any of the peculiar resinous, milky, or other secretions are produced ; and plants can only subsist under these circumstances when supplied with or- ganic nutriment We see this when shoots are developed from Potato-tubers in the dark, in the cultivation of Celery and other blanched plants, &c. But in some cases it would seem that plants not only have the power of acquiring carbon by their surfaces, but that they have also the power of growing in an atmosphere deprived of carbonic dioxide provided they can assimi- late the carbon from the carbonic dioxide circulating in their own tissues (Saussure, Corenwinder). A moderate addition of carbonic dioxide to the food of a plant, with free access of light and air, is mostlv accompanied by acceleration of the nutrient processes and a more abundant liberation of oxygen. Many green plants will flourish in sunlight on water and carbonic di- oxide alone. Saussure found that the organic matter of plants increased in the proportion of 2 to 1 of the carbon contained in the carbonic dioxide ; the elements of water being combined with the carbon. Effect of Nitrogen and of a want of Air. When plants are placed in pure nitrogen gas, or in vacuo, all the functions of vegetation are arrested ; not only do the chemical actions above noticed cease, but irritability, like that of the Sensitive-plants &c., is lost, and the plant decays. Even shoots separately enclosed suffer in the same way. The death occurs especially early when the plant is kept in the dark. This accounts in some degree for the injury resulting from roots grow- ing down too deeply into the ground, as is often observed with fruit-trees. Assimilation and Respiration. It appears, therefore, that there are two opposed sets of operations in which plants have close and ELABORATION OF THE FOOD. 577 important relations with the atmosphere : in the one, occurring when they are exposed to the sun's light, oxygen is liberated and carbon is fixed, which must be regarded as a process of assimilation ; in the other, oxygen is absorbed and carbonic dioxide is exhaled, as in the respiration of animals. The plant is thus subjected to two opposing forces in connexion with the chloropliyllian and the general respira- tion the one tending to add, the other to abstract material ; and, ac- cording to the proportion between these two forces, governed as they are by the variations of light and temperature, a plant will either emit oxygen or carbonic dioxide in variable proportions. In a feebly illuminated spot a plant may remain nearly in equilibrium for months. In absolute darkness, the eliminating force being the only one in operation, the plant can only live upon its own con- stituents, emit carbonic dioxide by their combustion, and finally perish without increase of weight (Boussingault). Fixation of carbon is absolutely necessary for the production of new ternary compounds (C H 0), but elimination of carbonic dioxide appears ab- solutely requisite for the maintenance of the life of the plant. The elimination of carbonic dioxide is increased by heat, and is most conspicuous at night or in darkness, but it never entirely ceases during the life of the leaf. In the daytime the quantity eliminated being small, it is entirely taken up and again deoxidized by the chlorophyll. According to Corenwinder the season of vegetation may be divided into two periods : the first that of growth, when the nitrogenous matter is in excess but rapidly diminishing, the period when the true respiratory process is most vigorous ; the second, the period of maturity, when the process of assimilation dependent on the deoxidation of carbonic dioxide by chlorophyll is at its height, the relative proportion of carbonaceous to other constituents being then greatest. The passage of gases, of whatever nature and in whichever direction, is dependent on the laws of diffusion ; the cuticle of the leaf in these cases acts as a dialyzer or filter, checking evaporation, but permitting the pas- sage of gases. Effect of Deoxidation. The assimilative process, in which oxygen is liberated, accompanied by accumulation of carbon in the tissues, is evidently related to the formation of the remarkable series of neutral ternary compounds which constitute the great bulk of the substance of plants, and, further, to the production of the more obscure and far more complex and varied series of sub- stances formed by a further removal of oxygen from the compounds of the first class. The composition of the principal constituents of cellular tissues, and 578 PHYSIOLOGY. the substances found in the watery cell-sap, is generally such that they may be regarded as consisting of carbon plus the elements of water ; but it is by no means to be regarded as settled that they are secondary com- pounds formed by the union of water with carbon. The formation of crystalline acids, such as oxalic acid &c., is theoreti- cally accounted for by a process of deoxidation. A further deoxidation of carbonic dioxide and water would result in the formation of the different carbo-hydrates, cellulose, starch, sugar, &c. A still greater loss of oxygen would account for the formation of the vegetable fats &c. The formation of the neutral ternary compounds being constantly in relation to the absorption of carbonic dioxide and the passage of water through the tissues, with the exhalation of oxygen, it has been assumed that assimilation of carbon in the green parts of plants is the result of decomposition of carbonic dioxide and of the combination of the carbon with water. As Liebig, however, indicated, water is far more easily de- composed than carbonic dioxide ; and perhaps the oxygen may be derived from that, its hydrogen uniting with carbonic dioxide. There is no evidence to show which view is correct. In the next place, Draper regards the decomposition of carbonic acid as a process resulting from contact- action or fermentation excited by the nitrogenous protoplasm, accompanied by a waste of the latter, in which nitrogen is liberated. Mulder, on the other hand, believes that the carbonic dioxide enters into combination with some substance existing in the protoplasm, and that the oxygen is set free by the decomposition of this compound ; for example, that chlorophyll is produced continually in sunshine, the wax associated with this being formed from starch, accompanied by a separation of oxy- gen, that this oxygen partly escapes and partly oxidizes the chlorophyll substance and causes it to become green. Of these views, Draper's appears the most worthy of credit, as agreeing best with the phenomena observed in the cell-contents. Chlorophyll does not originate from starch, but usually vice versa ; and it is quite admis- sible to assume a deoxidating contact-action of the protoplasm under the influence of light, when we observe a distinct oxidizing contact-action of the same part of the cell-contents in the dark, as in the decomposition produced by the growth of the Yeast-plant (p. 552). Nitrogenous Constituents. As to the nitrogenous constituents of plants, we know little at present beyond the fact that they originally exist in the form of protoplasmic substance, which, according to Mulder, consists of modifications of the substance called proteine, Known as vegetable albumen, fibrine, caseine, c. They constitute the substance of the pri- mordial utricle and the protoplasm, on which chiefly depend, in all pro- bability, the vital and chemical activity of the cell-contents. These have the power of decomposing organic compounds by contact-action^ and per- haps of causing new organic combinations. How they originate them- selves is unknown ; but it appears most probable that their source is either ammonia in combination with organic substances, or in some cases nitrates ; and it is most probable that there is ground for Mulder's opinion that all actively vegetating cells (containing protoplasm) are capable of directly assimilating organic matters to some extent, whether exposed to light or not, as has been shown in the case of the carnivorous plants before alluded to (p. 560). s SECKETION". 579 This seems borne out by the universal presence of these nitrogenous compounds in actively vegetating cells, in roots, parts of the flower, in cambium, &c., as well as in green organs. That the crude sap is found to contain uncombined ammoniacal salts high up in the stem in spring may result from the activity of the currents of fluid allowing part of them to flow on undecomposed, while a part only is assimilated in the roots. Proteinaceous matters, it may now be stated with some confidence, when not directly absorbed, originate in the colourless protoplasm, from the decomposition of sugar and ammonia salts, in the same manner aa starch is formed in the chlorophyll under the influence of light. Pasteur, as we have seen, induced the formation of protoplasm in yeast-cells by supplying them with a saccharine solution and a nitrate or ammonia salt. An animal of the simplest organization not only produces heat through respiration, and exhales carbonic dioxide, but a certain portion of the albumen it contains is modified by the respiratory combustion into a crys- talline nitrogenous compound (urea}. In the case of plants, asparayin, an amide, is formed in the darkness as a result of the general respiration, and this is as easily transformed into aspartate of ammonia as urea into its carbonate (Boussingault). This asparagin is a modification of the albuminoid matters stored up in the cotyledons, formed when a transfer of these matters is required, as in germination. Our space compels us to restrict this Section within narrow limits, and we are obliged to omit any special reference to the application of these generalizations to the explanation of the facts of Agriculture*. The student is recommended to study works on physics and organic chemistry, as vegetable physiology is daily becoming more and more a subject for the physicist and chemist ; and without a knowledge of the subjects treated of by students of these sciences, progress in vegetable physiology is im- possible. What is specially wanted are experiments and analyses showing precisely what physical and chemical changes go on in the several parts of the plant at various stages of growth and their rationale. Sect. 7. SECRETION. At the commencement of the periods of activity of plants, as when they shoot up from seeds, or when the new shoots are pushed out in spring, the whole product of the elaborating processes is devoted to the formation of new structure, to growth. As the season advances, the cell-forming activity slackens, the permanent tissues become consolidated by the formation of secondary deposits, and the parenchymatous tissues appear loaded with accumulated products of assimilation, such as chlorophyll, starch-granules, &c., which in annual plants are subsequently consumed in the matura- tion of the seeds, and in perennials are gathered together in autumn and stored up in those tissues which are to carry on the develop- ment in the succeeding season. * The student will find a useful summary of chemical science applied to agriculture in a little work called ' How Crops Grow ' (MacMillan). 580 PHYSIOLOGY. Secretions. The phenomena of growth have been dwelt upon incidentally in preceding Sections, and are further discussed in the next chapter ; but we have here to speak of certain processes, occur- ring more or less extensively in plants, contemporaneously with growth, in which products are formed which are not, like starch, chlorophyll, &c., evidently transitory forms of assimilated substance. These substances, called by the general name of secretions, are of most varied kinds, and their relation to the economy of vegetable life is very obscure ; but a brief notice of the most striking of them is indispensable. A distinction is sometimes made between the peculiar products found in the interior of cells, and those which are accumulated in certain cases in intercellular passages or cavities, or upon the outer surface of cell- membranes, the former being called secretions and the latter excretions. The principal substances secreted by plants are air, water, gum, sugar, volatile oils, balsams, resins, gum-resins, and salts, either entirely inor- ganic, or formed of combinations of mineral bases with organic acids, &c. ; besides these there occur in individual Orders a multitude of alkaloids, neutral substances of various kinds, colouring-principles, &c. Gases. The liberation of gases into intercellular passages, cavities, &c. occurs both as a necessary accompaniment to the chemical decompositions going on in the cells, and as a special process connected with peculiar habit of plants &c., as in the Utricularice, in the air-sacs of Fucus vesicu- losuSj &c. The composition of the air found in the cavities of plants necessarily depends upon the external conditions, as under sunlight there is generally a greater proportion of oxygen than exists in common air, in the dark but excess of carbonic dioxide. Water. Water is given off in a liquid form by various plants, either from glandulir papilla^ or from the general surface of leaves &c. In Nepenthes distillitoria, Sarracenia, &c. water is secreted in the pitchers wherein it accumulates. The leaves of various Musacea3, Aracese, Grasses and other Monocotyledons, Z'ropeeolum, Impatiens, Brassica oleracea, &c. give off drops of water from the leaves. In Caladium there exist orifices at the points of the leaves, communicating with internal canals, whence great quantities of water flow (half a pint in one night). This water is of course contaminated with salts and small quantities of soluble organic matters. Gum is usually poured out into and accumulated in intercellular pas- sages, as in the Cycadacea3, in the bark of the Acacias, Cherry, &c. When it is formed in large quantities, it bursts the tissues and exudes in the form of tears. The formation of the gum Tragacanth in the species of Astragalus is different from this, consisting of collenchymatous thick- ening of the cells of the pith and medullary rays, which swell by absorp- tion of water, and burst out from the stem under certain circumstances. The peculiar organs called cystolithes have a gummy excretion as a basis, in the form of a clavate body, suspended in the interior of an enlarged cell by a cellulose pedicle ; when mature these bodies are covered with SECRETION. 581 crystals of carbonate of lims : they are especially common in Urticacese, as in Ficus elastica, Morus, Itroussonetia, &c. Sugar, commonly occurring as one of the soluble forms of the assimi- lated ternary substances, is occasionally excreted, especially from the parts of flowers, such as the so-called nectaries. Through evaporation of water the sugar sometimes appears in a crystalline form. Grape-sugar (glucose) is apparently formed in the leaves by the combination of carbonic oxide and hydrogen, the former derived from the breaking up of carbonic dioxide, the latter derived from water. At other times it is formed from the me- tamorphosis of starch. It is supposed that from the glucose formed in the leaves the principal carbohydrates, such as cellulose, cuticular sub- stance, some acids (as oxalic and formic), are derived from the oxidation of the glucose. Sugar occurs commonly in the corolla-tubes of monopetalous flowers (Lilac c.), on the nectariferous coronet of various plants, on the glands of petals like those of Ranuncuhis, Parnassia, &c., or in pits in the same situation, as in some Liliacese. On the leaves of various species of Acacia occur glands secreting sugar ; and the same is the case in species of Clerodendron, Laurustinus, the lower surface of young leaves of Primus Laurocerasus, &c. Various species of Ash (Fraxinus) and Tamarix excrete a great quantity of saccharine substance under the form of manna. The wounds inflicted by insects (Aphis) also cause excretion of sugar from leaves, forming " honey-dew." Pectose and Pectase. Pectose is a gelatinous hydrocarbon insoluble in water, alcohol, and ether, found in unripe fruits, and in fleshy roots like carrots. By the agency of acids it is converted into pectine, which gives the viscid character to cooked fruits. Pectase is a peculiar ferment found in fruits, which transforms pectose into pectosic acid. Volatile Oils are extremely numerous. They are ordinarily secreted in glands, either external or internal, situated on the herbaceous parts of plants. They are rarely pure substances, the essential oils usually con- taining dissolved resinous matters, camphor, or active principles of various kinds. The odours of plants and many of their most important qualities depend upon these secretions, which are generally peculiar to particular genera or Orders of plants, and not unfrequently differ in slight degrees, so as to be characteristic of particular species in an Order. The chemistry of the formation of these bodies is still very obscure. Some are hydro- carbons ; others contain oxygen in addition ; and sulphur plays an impor- tant part in many, especially in the Cruciferae. The only general state- ment which can be made is, that the majority of the essential oils contain less oxygen in proportion to carbon and hydrogen than the dextrine and the other neutral ternary compounds, and that their production stands in a certain relation to the access of sunlight to the plants. The Labiates with their external epidermal glands, the Hypericaceae and Aurantiaceae with their internal glands, the Umbelliferse with the oleiferous vittse in the fruit, the Terebinthaceae, RutaceaB, &c. are striking instances of the occurrence of essential oils in particular Orders. Resins, solid or fluid (balsams), are very varied. They occur chiefly in intercellular passages, or in groups of cells especially devoted to the secretion of these products. Very little is known of the processes of their 582 PHYSIOLOGY. formation ; but the same generalities apply to them as to the essential oils with which they are not unfrequently associated. Among the resin-producing Orders may be noticed especially the Coni- ferae, the Leguminosae (Copuifera, Myroxylon, &r\), Amyridaceae, Gutti- ferae, Styraceas, Terebinthaceae, Liliaceae (Aloe, Xanthorrhea), &c. Resinous and waxy matters are found in considerable abundance on the surface of the leaves or fruits of many plants. It is not clear at present how far these are to be regarded as proper excretions or as chemically metamorphosed epidermal structures. Under this head falls the waxy coat of leaves and fruits which exhibit what is called a "blooin," as the' leaves of Primulaceas (P. Auricula, &c.), the fruits of the Plum, &c. The w*x of the Wax Palm ( Ceroxyloii) is formed in flakes upon the surface of the stem. "Wax and resinous matters occur on the outer coat of the pollen of flowers j and the viscid surface presented by the epidermis of many plants, such as Lychnis Viscaria, some Silenes, &c., is attributable to similar causes. Latex. The so-called milky juices (latex) occurring in specially modi- fied intercellular passages (p. 513) are of complex composition, containing essential oils, resins, gum-resins, starch-grains, extractive matters, alka- loids, proteiriaceous compounds, caoutchouc, &c. suspended in water, forming a kind of emulsion. They are not opaque and milky in their natural state ; but become so when exposed to air, and mostly assume a transparent resinous character when their watery constituents evaporate. Very different opinions have been expressed as to the nature of latex and the vessels containing it. By some it has been considered a nutritive fluid analogous to arterial blood, by others as of purely excrementitious nature. A third notion is founded on the comparison of the fluid in question with venous blood. Probably that view by which it is regarded as a fluid containing, mixed with matters of a directly nutritive character, others which are excrementitious in their nature (Sachs, Hanstein) is the most correct. Trecul holds that the laticiferous vessels are the analogues of the veins, and their contents equivalent to venous blood. He traces a contact and inosculation of the laticiferous vessels with the pitted ducts and other vessels. Latex from this point of view would be the residue of the sap after elaboration by the cells the caput mortumn of the sap. Faivre's experiments show that the latex may flow in any direction, and not only through the bark, but through the wood and the pith (in Ficus elastica). These juices abound especially in particular Orders, as in the Papa- veraceae, Euphorbiaceae, roots of Cichoraceae, Apocynacese, Urticaceae, &c. Amongst the most important substances obtained by evaporating them to dryness are : opium from Papaver somniferum, and caoutchouc from various Euphorbiaceae, Urticaceae, and Apocynaceae ; guttapercha from Isonandra yutta, &c. Saline Matters. The saline and purely mineral excretions of plants have been already referred to. They occur as incrustations of the cell- membranes, as silica in the Grasses, Equisetaceae, Stellatae, &c., or car- bonate of lime in Charce, Corallince, and in smaller quantities on the leaves of various Saxifrages. Crystals (raphides, p. 505), either of inor- SECRETION. 583 ganic salts or compounds of organic acids with lime &c., are frequently met with in the cellular tissues j but very little is known at present of the nature of their relation to the chemical processes of vegetation. Calcium oxalate may be regarded, according to Holzner and Hilgers, as a product of elimination, by means of which the superfluous lime is depo- sited in a solid form. This lime is set at liberty by the calcium phosphate absorbed, when this is decomposed to supply the phosphoric acid requisite for the new albuminoid materials. The lime so liberated is combined with the oxalic acid with which young tissues abound. Rauwenhoif shows that these raphides are wanting in plants grown in obscurity; which, therefore, is an indication of inability of the plant to absorb or decompose calcic phosphate. The close relation of the vegetable acids, oxalic, malic, citric, &c., to carbonic dioxide, water, and the ternary assimilated substances has already been alluded to. Tannin, or tannic acid, is a very frequent constituent of the woody tissues when their vital activity has ceased, and is perhaps a product of decomposition. It is formed in plants exposed to li^ht as well as in those grown in obscurity, but in smaller proportions in the latter case. Oak, Sumach, Ithus coriaria, Acacia catechu, &c. owe their tanning pro- perties to this substance. In fruits the proportion of tannin decreases as that of sugar increases, but it is not known what circumstances regulate the change. For the detection of tannin in the cells under the micro- scope, Sanio recommends that sections be macerated in potassic bichro- mate, which causes a reddish-brown precipitate in the cells, and which is consistent enough to allow of sections being made without extravasa- tion and staining of adjacent tissues. Speaking in general terms, it may be said that the immediate principles of plants may be grouped under three heads: 1, those in which oxygen is in excess as pectin, pectose, tannin, and vege- table acids ; 2, those in which H and O are in equal proportions cellulose, starch, gum, sugar, lactic, acetic, quinic acids ; and, 3, those where H is in excess as in resins, essential oils, camphor, salicin, various alkaloids and colouring-matters. 584 PHYSIOLOGY. CHAPTER III. GROWTH AND DEVELOPMENT OF ORGANS. Sect. 1. DEVELOPMENT or CELLS. The formation of new cells takes place in several ways,- though essentially the process always consists in the setting apart of the whole, or more frequently of a portion or portions of the proto- plasm in one or other of the following manners : 1, by condensa- tion or alteration of the molecular structure; 2, by segmentation or by both combined ; and, 3, by the blending of the contents of one cell with those of another. In any case the mass of protoplasm newly set apart is sooner or later invested by a cellulose coat. It is hence convenient to treat of cell-formation under the heads of segregation, conjugation, segmentation, and free-cell formation. Cell-formation by Segregation. A certain portion (or portions) of the protoplasm is set apart from the rest, escapes ultimately from the cell-wall, lives independently for a time, and ultimately is invested with a cellulose coat. The zoospores of (Edoyonium Development of zoospore in (Edogonium: a, parent filament; b, a joint breaking across to emit its contents; c, a more advanced stage, the globular mass of contents (nascent zoo- spore) still within a cellulose pellicle; d, empty parent cell; e, the zoospore escaped from it, with its crown of cilia formed ; f, the zoospore, after it has settled down, become encysted by a cellulose coat, and begun to grow into a new filament. Magn. 200 diam. and other filamentous Algae are formed in this manner (fig. 591). Sometimes the whole of the protoplasm escapes from the cavity of the cell, and ultimately forms a new cell. This is spoken of as re- juvenescence. The detached masses of protoplasm often move in an DEVELOPMENT OF CELLS. 585 amoeboid manner, and swim about by the aid of ciliary projections, and it is not until they come to rest that they form a cellulose coat (fig. 591) and acquire the appearance of a completely formed cell. Formation by Conjugation. This mode of cell-formation, met with in some Algse and in some Fungi (fig. 503, B, b : fig. 512, A, c, d), consists of the transfer of the protoplasmic contents of one cell into the cavity of an adjoining cell, and in the fusion or blending of the protoplasm of the one with that of the other. The spore so formed is called a zygospore. In place of a numerical increase an actual decrease occurs here, from the blending of two into one. Cell-division or Segmentation. This is the common mode of cell-formation in the vegetative system of plants, and occurs also in a slightly modified form in the formation of pollen. In this method of cell-formation the newly-formed cells remain for a time or per- manently in contact with each other, and do not become free or Fig. 592. Section of the outer layers of the rind of Cereus peruvianus soaked in alcohol: a, cortical cells with contracted protoplasm, some with newly formed septa (e); b, cork cells newly formed by division in the outer cortical cells; c, epidermal cells; d, cuticle. Magn. 200 diam. detached, at least at first. The process takes place in all growing parts of plants, but in the higher classes these regions are only ac- cessible by dissection ; in the lower, and especially in aquatic plants, we are able to observe the process of cell-division in living organisms in all its details ; and it is in these that the phenomena 586 PHYSIOLOGY. are most satisfactorily studied. Cell- division can only take place in a cell which retains its protoplasm in an active state, as in the cells constituting the meristem (p. 514). When the parent cell is about to produce two (or four, rarely more) new cells, the protoplasm separates from the cell-wall at the line bounding the plane of divi- sion, and advances inwards in the form of a narrow fold, until the portions of the fold coming from the different sides of the cell coalesce, so that the protoplasm is resolved into two (or more) closed utricles, together completely occupying the place of the original utricle. "While the protoplasm is folding inward, it forms thicken- Fig. 593. Cell-division in Cladophora glomerata. A. Part of a filament in a natural condition : a, cell- membrane ; c, primordial utricle or protoplasm; x, situation where division is about to take place. B & C. Stages of the formation of a septum at x, the filament having been treated with alcohol: a, wall of the parent cell; b, walls of the new cells; c, protoplasm. D. Septum of old filament treated with dilute sulphuric acid, to swell up and. separate the laminae of the cell-wall and contract the protoplasm : a, wall of parent cell ; b, wall of daughter cells; c, protoplasm. Magn. 200 diam. ing cellulose laminae on the wall of the parent cell and on either side of the septum separating the cavities of the two new cells, formed by the infolded portions of the protoplasm (fig. 593). This takes place not only in the vegetative cells but also in the pollen. At other times the new dividing cell-wall is formed gradually, after the sudden division of the protoplasm into two or more portions, DEVELOPMENT OF CELLS. 587 so that the process of cell-division exhibits two principal modifica- tions that in which the new cell- wall is secreted during the divi- sion of the protoplasm, and that in which it is formed only after its complete segmentation. This phenomenon may be traced very clearly in all its minutiae in large species of Confer vae (CladopJiora, fig. 593) ; and so far as we may judge from observations, extended from similar cases, through the accessible structures (nascent leaves, prothallia, &"c.) of Mosses, Ferns, &c., up to what we can detect in sections of the tissues of the Phanerogamia, it is the general mode of subdivision of cells. The principal varieties which this process exhibits depend on the cha- racter of the tissue to which the dividing cell belongs. In filamentous Confervoids this division takes place in most cases both in the end cell of a filament (apical growth) and in cells forming links further down (inter- calary growth) ; in each case the parent cell elongates more or less beyond the ordinary measure before dividing, and the new cells each grow until they equal the adult length of the parent. In the branched Cladophorce (h'g. 512, C) &c. the parent cell sends out a lateral arm, which is at first a pouch with its cavity continuous with that of the parent ; and this is subsequently shut off by a lateral septum formed in the manner above described. The basidiospores of the Agarics &c., and the spores of Penicillium, Bo- try tis, and the allied forms of Fungi, are produced in the same way, as also are the conidia of the " Yeast-fungus/' the new cells emerging like bubbles blown out from the wall of the parent cell, and becoming sub- sequently shut off by a similar process. In the Phanerogamia, the cells of the growing points, as of the apex of buds and roots, of the cambium- layer of the stem, &c., multiply while very minute, so that it is not so easy to trace the changes ; but cell-division may be readily observed in the epidermal hairs of the highest plants, and the protoplasm is observed to be equally efficient as the agent of multiplication in these. The direc- tion in which the division takes place is usually horizontal, sometimes oblique, rarely if ever strictly vertical. It will readily be surmised that the form of the organs and the mode in which they ramify may depend materially on the form of the terminal or apical cells, and on the direction in which they divide. The production of complete cells within cells, the septa dividing the new chambers being continuous with new laminae deposited on the old wall of the parent cells, may not only be observed directly in Clndophora (fig. 593, D), but is beautifully proved by allowing filaments of Spirogyra to decay in water ; but these break up into lengths of eight, four, and' two cells, and at last into single short cells, by the solution of the membranes from without inwards. The softening and swelling up of these parent membranes doubtless give rise to the semigelatinous coat of many of the lower Algae, espe- cially the Nostochinemdia. &c.). In the Hepaticae and Mosses the propagative structures do not arrive at the condition of bttds, although the parent plants have leafy stems. The gemmce of these Classes are merely cellular nodules, more or less de- veloped in different cases, and only acquire leaves after they have become independent. In the Jungermanniaceae they are developed on the leaves or in place of fruits. In Marchantiacese they are fouitd in cup-like re- ceptacles, being especially frequent when the plants grow in damp, shaded localities, a number of them (springing originally from a single cell) lying in the cup like eggs in a nest. The Mosses produce gemmce from all parts of their structures from their leaves, stems, metamorphosed fruit-organs, and, above all, from thread-like runners (protonema) which shoot out from the base of their stems. When their spores germinate, they also form first a mesh of confervoid filaments, each joint of which often gives birth to a leaf-bud (fig. 499, p. 430). Buds of Vascular Cryptogams. The Ferns and allied Classes agree more closely with the Flowering plants in their vegetative propagation, forming leaf -buds in cases where they increase in this way ; but there is a connexion with the Mosses c. in the circumstance that their gemma appear more frequently on the leaves than is the case normally in the Phanerogamia as, for example, in Asplenium rhizophyllum, where the leaves root and form buds at their tips, Cystopteris bidbifera, in which bulbils appear on the petiole, &c. Buds of Phanerogams. In the Phanerogamia the rule is, that every leaf -bud may be separated from the parent stock, and, if properly treated, reared into a new plant ; moreover, in a vast number of cases, the leaf- buds are naturally modified in certain details of their structure, so as to protect them from external injury, and then thrown off spontaneously by the parents to multiply the kind/ Many of the cases of this phenomenon have been described 'in the first part of this work under the head of VEGETATIVE MULTIPLICATION. * 615 Morphology of Stems (p. 20 et seq.} and Buds (p. 69). We have there spoken also of the formation of adventitious buds (p. 70) and cited nume- rous examples strongly indicating that relative independence of the parts of the organization of plants referred to above. Adventitious Buds are formed mostly when a plant or part of a plant loaded with assimilated nourishment is deprived of its natural developing- points. Thus we see ahundant formation of adventitious buds on healthy trunks of trees wliich have been pollarded, i. e. have had their heads cut down so as to remove almost all their natural buds. Sometimes the shoots so produced simply result from the development of otherwise dormant buds. The abundant supply of food existing in the trunk, however, often stimulates the cells of the cambium-reyion (p. 530) into extraordinary de- velopment, and true endogenous leaf-buds are produced, which form vents for the vital energy of the plant. This power exists even in the roots of many trees, as in Madura aurantiaca, Pyrus japonica, &c., fragments of which in a healthy condition may be made to produce new plants. The buds so formed are of endogenous origin, arising in or near the cambium- region. Mention has been made of the formation of adventitious buds (as exo- genous formations) on leaves, which has been observed frequently in wild plants, and is artificially induced in many cases as a means of propagation. As a rule, leaves are less prone to produce buds than stems or even roots, as might be expected from the more actively changing state of the con- tents of their tissues, and the usual absence of any great accumulation of assimilated substance, such as is regularly met with at certain periods in the stem and root. That striking characteristic of vegetables which displays itself in the physiological independence of the leaf-buds, renders the vegetative propa- gation of plants a most important feature in their history, both in a natu- ral and, in a still higher degree, in a cultivated condition. A brief notice of some striking phenomena illustrative of the spon- taneous propagation of the higher plants may be given here. Various herbaceous plants are multiplied by spontaneously detached axillary leaf -buds : of this we have f amiliar examples in Lilium bulbiferum, Dentaria bulbifera, and the cultivated species of Aclrimenes. Similar pro- pagative buds are often produced instead of flowers in the inflorescence of the species of Allium (Garlic, &c.), both in a wild and cultivated con- dition : and the same is the case with some other plants, such as Polygo- num viviparum, &c. The multiplication of bulbs by " cloves," or axillary bulbs produced in the axils of the scales of the parent bulbs, has been described in a former Chapter (p. 25), and there also have been mentioned the structures called tubers, formed of modified stems, which are important agents in propa- gating the plants in which they occur. The Potato, for instance, forms tubers from its branches, the " eyes " or buds of which may be separated and made to produce each a new plant : and the Jerusalem Artichoke, Dahlia, &c. are similar in this respect. The terrestrial Orchids, such as Orchis Morio (tig. 21) &c., are not multiplied by their tubers, but only continued from year to year, since only one new " eye " is formed annually. Still more frequent, perhaps, than the formation of bulbils, bulbs, or tubers is the development of leafy shoots peculiarly organized for the 616 PHYSIOLOGY. purpose of propagating the plant which bears them, commonly compre- hended under the names of offsets, stolons, runners, &c. Almost every gradation of condition occurs here, between the divisible rhizomes of such plants as the Daisy, Primrose, &c.,the "runners" of the Strawberry, Vallisneria, Hydrocharis, &c., the offsets of House-leeks, Stratiotes, and the rosette-like stolons of Epilobia, c., which approach to the axillary bulbils of Achimenes, and connect all these forms with the subterraneous bulbs, corms, and tubers. Propagation by Artificial Means. The artificial propagation of plants by division is effected by a variety of processes founded on the same physiological laws as the natural multiplication by de- tached buds, &c. ; it also includes a peculiar class of operations, in which the new plants are not converted into absolutely inde- pendent stocks, but are made to assume a -pseudo-parasitical habit upon other plants, whose roots furnish them with that portion of their nourishment which is derived from the soil. In the simple propagation, advantage is taken of the vital activity of the cambium-region to stimulate it to the production of roots, in the gardening processes of propagation by slips or cuttings, layers, &c. In the production of pseudo-parasites, as in buddmc/ and (/rafting, the woody structures of two distinct plants are made to become intimately blended by bringing into immediate contact the cambium-structures of both, at points where the cellular tissue is in an active state of development. Cuttings or Slips are ordinarily fragments of stems consisting of young wood bearing one or more buds. These are planted in earth, and in some cases require no especial care to make them produce adventitious roots from the cambium-region, as in slips of Willows and many common soft- wooded plants. Mostly, however, it is necessary to stimulate the vegeta- tive action by a slight degree of artificial heat in all cases, however, guarding against drought ; so that, as a general rule, cuttings are made to " strike " root best in an atmosphere where the watery vapour is confined by a glass covering. It is a matter of indifference whether a cutting having a number of " eyes " or buds is planted with the head upward or with the summit buried in the soil and the lower part left free. In the latter case, the ordinary direction of growth of all the new shoots becomes reversed. When a cutting is made, a callus of cork-cells is formed over the wound, and the adjacent cells are filled with starch-grains, prior to the formation of the roots. It has been stated above that by careful management plants may be raised from cuttings of roots, and even from leaves made to produce ad- ventitious buds by artificial stimulus. Layers only differ from cuttings in the circumstance that the fragments to be detached are made to strike root before they are separated from the parent stock usuallv by bending down the branches and burying them in a portion of their course in the soil ; an incision is usually made into the wood in the buried portion, which causes the more ready production of ad- ventitious roots. An analogous operation is sometimes practised, in which VEGETATIVE MULTIPLICATION. 617 a shoot is caused to root high above ground, by surrounding one or more of its nodes with a mass of earth kept moist by wet bandages or other means. The artificial process of layering, practised commonly with Pinks, Ver- benas, Aucuba, &c.,is analogous to the natural propagation of the Straw- berry by runners. In all the cases comprehended in the above remarks, the adventitious roots are formed most readily in the vicinity of buds, at the nodes, just as we see them naturally occurring chiefly in those situations in creeping plants, such as the Sand-Sedge (fig. 25), Mint, many Grasses, &c., which root at every joint that comes into contact with moist soil, or in the climbing Ivy, in which the adventitious roots forming its organs of attach- ment to foreign bodies are produced in tufts a little below the leaves. Grafting. In the operations of budding and grafting, the parts of the parent plant are caused to assume a kind of parasitical condition, in which they stand in the same relation to a strange " stock " as they would have held to their parent if left in their natural condition. The detached bud or shoot is made to contract an organic union with the cambium- region of a foreign stem, of which it becomes, as it were, a branch, deriving its supplies of root-nourishment from it, and subsequently sending down in return elaborated juices to contribute to the sustenance of its foster parent. It is important to note, however, that in the case of distinct plants thus combined they usually exercise no appreciable influence over each other in regard to modifying the morphological characters of each ; the connexion merely affects the scion and stock in the degree of activity of the general physiological processes of nutrition, &c. Scions grafted on stocks of more enduring character acquire greater vigour and fecundity ; but the products of the buds of the scion, in the great majority of cases, resemble in kind those of their parent, while the stock continues to grow in its own way. The influence of the scion on the stock, is rendered less noticeable in practice from the fact that buds or branches of the stock are always removed after the scion has " taken," in order to concentrate the sap in the latter; and if allowed to develop, the branches of the stock formed below the scion mostly remain unaffected by the stranger which has settled above them. Influence of Stock on Scion. A certain amount of physiological influence of the stock over the scion is shown to exist by such facts of horticultural experience as the dwarfing of certain varieties and their earlier or increased productiveness according to the stock, as in the case of Apples on the Para- dise stock, the fact that the fruit of the Pear is smaller and more highly coloured when " worked on " the Quince or Medlar than when grafted on Pear-stocks, and is earlier when worked on the Mountain Ash. It is not clear here whether the alteration is attributable to greater or less vigour of the stocks, or to an influence obstructing the return of elaborated sap towards the roots, arising out of difference of texture of the wood. Influence of Scion on Stock. On the other hand, the scion has been in a few cases observed to affect the stock. It is well known that the variety of the Yellow Jasmine with variegated leaves, budded on a plant with healthy green leaves, causes the gradual appearance of variegation through- 618 PHYSIOLOGY. out the whole of the foliage of the plant. The same phenomenon has "been witnessed repeatedly in the case of variegated kinds of Abutilon. If a variegated scion of A. TJiomsoni be placed on a green-leaved stock, the new leaves pushed out from the latter become also variegated. If a green scion be placed on a stock of the variegated Abutilon, the new leaves of the scion become variegated. Further, if the variegated scion be removed from the green-leaved stock, the latter no longer produces variegated, but only green leaves. A still more striking phenomenon is the production of a hybrid Laburnum, by grafting Cystisus purpurem upon the common Laburnum. Many such cases are now authenticated, and will be referred to under the head of Hybridization. Budding consists in attaching the bud of one tree upon the developing wood of another. For this purpose the bud is removed from its parent with a slip of the bark surrounding it, bearing on its inside a portion of the_ cambium-tissue existing at the line of junction of the innermost region of the bark with the youngest wood; this is applied upon the surface of a portion of the cambium-layer of the stock, exposed by slitting its bark and turning it back so as to form a kind of pocket. The slip of bark is inserted into this, so as to bring the cambium of bud and stock into complete contact, and the bark of the stock is then carefully bound down over the wound with bandages of bast, tape, &c. The organizing force resident in the cells of the cambium of the two portions causes them to grow firmly together. In Grafting, a shoot instead of a bud is attached to the stock ; and this is commonly effected by cutting off the head of the stock (or a branch of sufficient growth) with an oblique surface, or with a deep notch offer- ing more than one oblique surface ; the bottom of the shoot or graft is pared so as to fit accurately on the oblique surfaces, and in this way con- siderable tracts of the cambium-tissue and young wood are brought into contact their ceUs, however, being partly end to end here, instead of side by side as in budding. Union of the growing region takes place exactly as in the former case. Grafting is usually practised with young woody structures ; but it is also successfully applied to herbaceous plants with careful management ; and some Grasses even admit of being grafted on each other, although the operation is generally confined to Dicotyledonous plants. What is termed Inarching, or " grafting by approach," may be com- pared to layering (p. 617) : in this modification of the process, the scion is brought into union with the stock by bending over or otherwise, without being detached from its own stem, and the separation is not made until the scion has " taken " on its foster-parent, &c. It was at one time imagined that the annual layers of wood of Dico- tyledonous stems grew down absolutely and mechanically from the buds, of which they were said to represent the roots. It was thought also that, in the case of grafts, the scions sent down woody structure over the old wood of the stock, so as at length to enclose it. From the description given before of the horizontal development of the cambium-layer of Dico- tyledons, it will be seen that such notions are devoid of * all ground. Merely fluid matters pass up and down in the cambium and bark, and the only reciprocal influence of stock and scion depends on the respective activities of roots and foliage. TEGETATJVE MULTIPLICATION 619 The success of grafting depending on the contraction of intimate union between the cellular structures of the two plants, it is not sur- piising that, as a rule, it is only between nearly related plants that such union is possible. If the size of the elementary organs, the rapidity or the extent of their periodical multiplication and expansion, &c. are unequal, it is evident that no permanent coherence can exist j a tissue grow ing more rapidly w T ould tear itself away from one less active. As a general rule, the elementary tissues agree closely in allied species, less closely in genera of the same Order, and are very diverse in different Orders ; so we find that grafts take readily on stocks of their own species, to a con- siderable extent on stocks of allied species, and to some extent on stocks of genera belonging to the same Order. As a general rule, genera of distinct Orders cannot be grafted with success. The parasitic Mistletoe, however, attaches itself by a natural graft to various trees, such, as Apples,_Oaks, and even to Coniferae. Some as yet unexplained exceptions exist to the inclination to union between allied genera. In some cases, also, a temporary union is effected, subsequently destroyed by unequal growth. Among the Rosacese we see Pears grafted readily on Quinces, with more difficulty on Apples, and not at all on Plums or Cherries. Cherries and the Cherry-laurel readily unite. In the Oleacese we have the Lilac uniting with the Ash, the Olive with Phillyrea. It is extensively practised also with diverse species as well as varieties of Rhododendron. The Pear may be grafted on the Hawthorn ; but the former grows so much faster than the latter that the communication between the two becomes interrupted in a few years at the point of junction. The practices of grafting and budding are principally carried on, like propagation by slips &c., for the multiplication of varieties, which are, for the most part, grafted on other varieties, or normal specimens of their own species, these being far more healthy and permanent than those ? rafted on allied species. The multiplication of esteemed varieties of loses, fruit-trees, &c. is chiefly effected by this means, the object being to produce specimens promising increased hardiness c., or to obtain size and f ertility earlier than could occur in a plant raised from a small cutting. Moreover, much greater certainty of reproducing the desired form is attained than is the case with seeds. The seeds of an Apple, for instance, rarely reproduce the parent form exactly. The Peach is worked on the Plum in Britain, because the latter is a native of this climate and is stimulated to growth in spring by a lower temperature than the Peach (from Persia) ; it does not succeed well here on Almond-stocks. The Pear seems to succeed better on Quince than on Pear-stocks in loamy soils ; and many similar instances are well known to gardeners. In addition to these circumstances, Pears, Apples, and other plants which may be easily grafted do not readily root from cuttings j moreover esteemed varieties of Rose &c. are quickly multiplied as " standards " &c. by budding them on briar-stocks already of several years' growth ; and, in the case of new seedlings of fruit-trees, buds inserted on full-grown stocks are brought to flower and fruit in a few years, w y hile if left to grow up into trees alone, twenty years or more might elapse before they bore a crop. Certain phenomena of grafting which are observed in practice cannot 620 PHYSIOLOGY. be fully explained by our present knowledge, but doubtless depend on causes similar to those just adverted to ; among these are the facts that the Orange succeeds better on a Lemon-stock than on one of its own species, while the Apricot does better on its own species than on the Plum, &c. The influence of the physiological conditions of the stock upon the scion is turned to account by gardeners in producing a dwarfer " habit " and an earlier and more profuse production of fruit. Thus Apples grafted on the low-growing " Paradise stock " assume the dwarf habit of the stock and become more prolific. So Pears on the Quince-stock not only are dwarfed in size, but produce fruit much more abundantly than when grown on their own roots or grafted on another kind of Pear. Gardeners often practise " ennobling" fruit-trees, where buds and grafts are attached upon stocks of good varieties of the plant in preference to wild stocks. Thus Apples are said to be much superior when grafted on stocks of good varieties instead of on Crabs, &c. ; and a kind of crossing of the qualities of varieties has been attempted on this principle, grafting kinds which bear sickly-flavoured Apples upon stocks of rougher varieties, Jargonelle and " mellow " Pears upon later, gritty varieties, &c. " Double graft- ing " is done when it is desired to secure a particular kind of fruit which will not unite or graft with the ordinary stock ; thus a Pear may be grafted on a Quince-stock, and on the scion may be grafted another Pear, which will not unite directly with the Quince. Further details on the subject of grafting, a most important and interesting one, must be sought in horticultural works. Sect. 2. SEXUAL KEPEODTTCTION. Preliminary Observations. In almost all plants the greater part of the active existence is passed in the development of vege- tative organs, increasing the bulk of the individual, or occasionally also accompanied by multiplication of the plant by mere subdivision into parts. But at certain epochs another tendency manifests itself : the energies of the plant become concentrated in the forma- tion of what are called reproductive organs, for the purpose of producing and maturing those independent germs of new indi- viduals of the species called spores and seeds. The formation of reproductive structures bears a very interesting relation to the vegetative development. Generally speaking, the repro- ductive organs are only formed when the vegetative structures have become healthily developed, so as to accumulate a certain amount of assimilated matter in the substance of the plant. We observe that many garden plants grown in unfavourable soil, in shady localities, &c. will not flower; and the number of years that elapse before the flowering of such plants as the Agave, Talipot Palm, &c., varies with the more or less favourable climate and soil ; moreover, in ordinary cases, the flowering takes place at the close of the season of growth (except where the flowers emerge from buds provided for by the previous year's vegetation, as in Apples &c., in biennial and many perennial herbs). This indicates that vigour of the vegetative organs is a necessary condition of reproduction. SEXUAL EEPEODUCTION. 621 Further, reproduction is an exhausting process ; it kills some animals : and excessive fruiting exhausts perennial plants. At the same time, the reproductive tendency and the vegetative ten- dency appear contrasted and opposed to each other ; for reproduction is often retarded and replaced by rapid development of vegetative structures when plants are placed in too favourable a soil, especially when too freely supplied with water ; and rankly growing plants are frequently made to flower by gardeners cutting the roots, confining them to small pots, or limiting the supply of water. The reproductive bodies produced by plants are either developed at certain epochs from structures originally belonging to the vegetative system, or they are formed in special organs. In the lower Algae we find the cells, as those of the filaments of (Edogonium (fig. 505) or Spirogyra (fig. 5 12), originally true vegetative cells, and at a certain stage of grow y th resolved into reproductive cells and producing spores from their green contents. As we rise in the scale, among the Thallophytes, we soon find special cells (Penicittium, &c., fig. 1, C) or groups of cells, exclusively vegetative or exclusively reproductive. In the higher Cryptogams, assemblages of organs of various kinds are formed upon the stems, in which are ultimately ripened the spores of this group ; while in the highest class, the Phanerogamia, we meet with fiowers containing stamens and pistils, ultimately producing true seeds in fruits which are totally separated m almost every case from the vegetative structures. The spores of the higher Cryptogams (Ferns, Mosses, &c.) cannot be properly compared to the seeds of the Flowering plants (that is, morpho- logically), since they result from a series of physiological processes different in many respects and not directly dependent on sexual agency. With regard to the spores of the Thallophytes, our knowledge is too imperfect at present to enable us to decide in all cases upon all the homologies ; the probable relations of the different kinds of structure are incidentally spoken of in the Sections devoted to the description of these plants. It is probable that representatives of two sexes, male and female, exist in all plants, and that these conjoin to form the rudiments of the new in- dividuals of all Cryptogams, as they do in the formation of the embryo in the seed of Phanerogams. But in the Thallophytes the male and female organs are often reduced to simple masses of protoplasm, " sperm- cell" and "germ-cell " (these being associated often in the same plant), bud-cells, conidia, &c. serving the purposes of vegetative propagation : the exact particulars and homologies are still obscure in many families. The history of reproduction of plants has been greatly studied and much enlarged of late years ; many important discoveries have been made in all classes ; and the course of the processes in Phanerogams and the leafy Cryptogams is now pretty well known. Much still remains to be dis- covered in reference to the Thallophytes, especially the Fungi ; but in the Algae the processes of fertilization of germ-cells by spermatic cor- puscles have been observed more clearly and definitely than in any other plants. Conjugation. The simplest form of sexual reproduction is that known as conjugation, or the fusion of two masses of protoplasm the one into the other, as has been already mentioned under the t>22 PHYSIOLOGY. head of cell-formation, p. 585, and which is adverted to in the description of the Thallophytes. The spore resulting from such union is termed a zyyospore (Mucorini, Algae, &c.). The conju- gating cells are either motionless, or, as in Botrydium and Aceta- bularia, the motile particles of: protoplasm (zoospores provided with cilia) combine one with another to reproduce the plant. In other cases the germ particle is stationary while the sperm particle exhibits active movements. Generally both sperm particles and germ particles are uncovered masses of protoplasm, the cell-wall not being formed around the germ mass until after fertilization. Further details relating to the various modifications observable in the reproductive cells are given in the sections relating to Cell-formation and to the separate natural orders of Cryptogams. Sect. 3. KEPRODTJCTIO^ OE PHA:N T EKOGAMS. The remarkable distinguishing character of this group of plants is the possession of stamens producing pollen and of carpels pro- ducing ovules, the latter containing a large cell, the embryo-sac, within which is the germ or germinal vesicle. The sperm-cell or pollen-grain falls on the stigma, elongates into a long tube, which traverses the style and comes into contact with the embryo- sac containing the germinal vesicle. As a consequence of this con- tact, the germ- vesicle becomes a cell, and this ultimately forms an embryo, as described in other sections. In G-ymnosperras the pollen or sperm-cells are applied directly, without the intervention of style or stigma, to the nucleus of the ovule. The germ-cell here differs from that of Angiosperms, and is called the corpuscle (see ante, p. 358). It is supposed to be homologous with the germ- cell or central cell of Lycopods (p. 424). The differences in the development of the embryo of G-ynmosperms and Angiosperms are treated elsewhere. The formation of the reproductive organs closes the life-cycle of the plant either permanently, or, in the case of perennial plants, the periodic cycle of growth and the progeny thrown off, after passing through a quiescent stage of rest, germinate afresh into a new perfect morphological representative of the species. Alternation of Generations. Vegetative reproduction (agamo- (jenesis) in its varied forms and sexual reproduction (gamogenesis) may be manifested in the plant at the same time, or they may alternate one with the other ; thus the production of spores and the formation of a prothallus in Ferns is an asexual process alter- nating with the development of a perfect plant from the action of a spermatozoid in the central cell of the archegonium. Among REPRODUCTION OF PHANEROGAMS. 623 Thallophytes, as we have seen, great differences often exist in the same plant even, in both asexual and sexual modes of reproduction, the plant at one time and under one set of conditions reproducing itself in one way, at another time and under different conditions in another. For practical purposes such as the investigation of parasitical plants detrimental to animals or to other plants, it is of the greatest importance to know the life-history of the plants in question and the conditions propitious or adverse to its several modes of reproduction, as with such knowledge it may be possible to devise a remedy or avert the mischief. Pollen-grains of Plianerogamia. Sperm-cells. Pollen-grains, the sperm-cells of Phanerogamia, correspond to the microspores of the heterosporous Vascular Cryp- togainia ; their protoplasm exhibits simply a nucleus, with granules of starch, oily matters, and other ordinary cell-contents. In this respect they approach the fertile cells of conjugating Alga?. Structure. In their simplest forms they are single cells, with a proper cell-coat or intine, and an outer cuticular coat or extine, mostly marked with irregularities, forming a kind of pattern on the surface, sometimes very elegant. In particular cases the outer coat is laminated, so that the pollen-cell appears to have several coats. In all cases the outer coat exhibits one, three, or many round holes or slits (pores) (fig. 602, ). where the inner coat is bare ; in the pollen of Passiflora, Cucur- bita, &c. there exist lid-like covers over the pores (fig. 602, c). Bands or fur- rows generally passing along the long diameter of the pollen-cell are frequent, varying in number according to the species : but these bands are generally 1 - Pollen-grams, magn. 1 00 diameters: a. Be gram llis; b, Acacia laxa (com- only visible in the dry state. Form and Size. The form and size of pollen-grains vary very much, as may be observed even in the few examples here figured; but although there may be a general resemblance throughout particular genera, and even Orders, they do not often afford good or regular systematic cha- racters. They sometimes vary in different genera of the same pound grain) ; c, Passiflora ceeru- lea ; d, Periploca graeca ; e, Trade scantia ; f, Cichorium Intybus ; g, Epilobium montanum ; h, Lathrcea squamaria, forming pollen-tubes among the cells of the stigma. 624 PHYSIOLOGY. order, in different species of the same genus, e. g. Viola, and even in the same species, e. g. Fuchsia, Primula, Mimulus. The most frequent cases of agreement in allied plants occur when they possess compouml pollen-grains (fig. 602, b, d), consisting of a number of pollen-cells permanently coherent together. The most striking cases of this are those offered so abundantly in Orchidaceae and Asclepiadaceae as to form valuable systematic characters in these Orders. These pollen-masses or pollinia con- sist either of the entire mass of pollen of an anther-cell, or of a half, quarter, eighth, or smaller fraction, so numerous in some genera as to appear like granules merely coarser than ordinary pulverulent pollen. Formation of Pollen. The existence of pollen-masses and compound grains is readily accounted for by the history of the development of pollen, which agrees in the main points with that of the spores of Mosses &c. (p. 429). The parenchyma in the central region of each lobe of a young anther presents two perpendicular rows of cells, one corresponding to each of the four primary loculi, different in character from those which are to form the walls. The cells in these series multiply by division to a considerable extent ; and ultimately each forms a free cell from its whole contents the parent cell of the pollen. These are set free by solution of the walls of the parenchymatous framework in which they have been de- veloped, and they then lie as loose cells in the loculi or chambers of the anther thus formed. Each parent cell divides into four chambers ; and each of these chambers (special parent cells) produces a pollen-cell, in the case of simple pollen-grains set free by the solution of the special parent cell. In quaternary pollen (fig. 602, d) the membranes of the special parent cells are not dissolved, and thus the pollen-cells are held together in fours ; and the more complex conditions arise from the membranes of the parent cells of anterior stages persisting sufficiently to hold their pro- geny together. The mode of formation of the pollen in the special parent cells is by some attributed to cell-division ; but the more generally adopted view is that it is formed bv free-cell formation. The nucleus of the parent cell divides into two ; "between these two a quantity of granules of protoplasm are aggregated together in a direction across the parent cell : these granules are suddenly seen to be divided by a line, the first indica- tion of the cell-wall between the two cells so produced ; these two again subdivide ; and thus four pollen-cells are ultimately found in one parent cell. The pollen-masses of the Asclepiadacese, and perhaps of some Orchidacea3, result from a different process : in these the outer layers of the primary parent cells do not develop cells in their interior, but become conjoined into a cellular pellicle forming a sac or purse enclosing all the poll en-grains formed within. The pollen-cells acquire their cuticular coat after they have become free ; but part of the material of this structure appears to be derived from the dissolved membranes of the parent cells. Zostera presents a remarkable exception to the usual character of pol- len-grains, the cells here having the form of short cylindrical filaments with but one coat, i. e. without a cuticular layer. In these a rotation POLLEN-GKAINS OF GTMNOSPEEMIA. 625 (p. 549) of the cell-contents may be observed, which is likewise occasion- ally to be seen in recently formed pollen-tubes of other plants. The minute starch-grains of the cell-contents are noticeable as exhibiting a molecular motion, which was at one time imagined to be of vital cha- racter, and might lead the inexperienced to suspect the existence of minute spermatozoids. Examination of Pollen. Pollen-grains should be examined first as dry or opaque objects, as their form and dimensions are altered by en- dosmosis when immersed in fluids. Oil of cloves, syrup, glycerine, or naphtha are convenient fluids for examining pollen. A large number of pollen-cells, illustrative of their form and size, are given in the ' Gardeners Chronicle,' 1876, pp. 516 and 548. The discrepancies in the descriptions given by various authors depend on the conditions under which the pollen is examined. In the anther, and immediately after expansion, it is gene- rally globular, but it often speedily assumes quite a different shape. When the pollen is transported by the" wind, it often happens that the flowers are relatively unattractive, and the individual pollen-cells relatively small and smooth. In insect-fertilized flowers, on the other hand, the flowers are attractive and the pollen spiny or furrowed (Bennett). Too much stress, however, must not be laid on this point. Pollen-grains of Gfymnospermia. The pollen-grains of the Gymnospermia present a modification of the structure above described. They are not simple cells, but produce in their cavity, even before they are discharged from the anther, minute daughter cells, from one of which the pollen-tube is developed, and adherent to that side of the pollen-grain where the slit exists in the outer membrane. This formation is analogous to what is seen in the microspores of Selaginella, which in like manner produce a rudimentary prothallus (p. 425). According to Schacht, in Taxus and Cupressus the pollen-cell only di- vides so as to form two unequal portions, of which the larger develops into the pollen-tube. In Larix and Abies (fie*. 603) the pollen-grains appear to consist of a central and two lateral cells of different appearance to the central cell. These lateral projections are often finely reticulated, and are mere vesicular protrusions of the extine. The central body is the true pollen-cell, in which cell-division goes on, as in the case of Cupressus above mentioned, but with the difference that three or four daughter cells of unequal size are produced instead of one, the uppermost and largest of these new formations being developed into the pollen-tube, which passes through a rent in the extine, the other forming a kind of suspensor. Strasburger dissents from this view, and says that there are never more than two cells, the one marked q being- a simple fissure or rent. The pollen-tube, according to him, is the result of a protrusion of the intine and not of the whole cell. TchistiakofPs researches into the mode of formation of the pollen of Conifers are remarkable as showing varying degrees of complexity and of transition between the formation of new cells by division and the process 2s 626 PHYSIOLOGY. which develops into the pol- len-tube; i, the intine; q, lowermost cell of the male prothallus in contact with the intine (according to Strasburger, this is no of free-cell formation ; and they establish an homology with the mother cells of the antherozoids of Cryptogams. The processes are somewhat complex ; but if the lamination of the cuticle and cell-wall be borne in mind (p. 520), and the differentiation of the protoplasm into por- tions of varying density (p. 495) and crystalloid form be remembered, the stages of the i process will be more readily understood by the student. Tchistiakoff's researches show that the pollen of these plants is divisible into two groups, those with and those without vesicular protrusions or air-bladders. In both cases the mode of for- mation of the extine is identical. In both cases it consists of two layers j but where there are no air-bladders the two layers of extine are formed simultaneously. In the opposite case they are Pollen of Bpruce Fir> after formed in succession, there being at first between Schaeht : bl, the vesicular the two an interspace filled with gelatinous fluid, which absorbs much water by endosmosis. The interspaces therefore become much distended, and ultimately form the air-bladders attached to * the grain, the fluid contents disappearing. The net-like markings on these bladders are due to cell but merely a fis8Ure) . the remains of protoplasmic threads adherent to the extine. As to the division of the pollen-cells and formation of a male prothallus, M. Tchistiakoft* admits three types : 1, that of Ciipressus and other genera ; 2, that of Larix &c. ; 3, that of Abies &c. In all cases the starch in the cells becomes dissolved, the cell-wall (intine) swells up and becomes more hygroscopic, so that by its distention it throws off the cuticular extine, when the pollen-tubes begin to grow or germinate. While these changes in the intine are taking place, the outermost por- tion of the protoplasm becomes developed into a separate layer of globules or crystalloid masses surrounding the whole or only a portion of the plasma or cell-contents. The formation of the new cells may take place simultaneously with, or after, the differentiation of this peripheral layer of protoplasm, which, in the latter case, takes no part in the division. In the Oupressus or Thvja type, the pollen-cells either do not divide, or each divides into two cells. The starch is dissolved, the nucleus divides into two : of these, one becomes more homogeneous, denser, and more transparent than the other, and resembles the homogeneous beak of the zoospores of Algae. Both may be surrounded by the layer of protoplasmic globules just described, or one only. In the Larix type, instead of two subdivisions of the plasma only, the two first formed divide again. In the case of the last subdivision a por- tion of the plasma becomes denser and more homogeneous, as in the former case. In Pinus two or three subdivisions take place, the cells so formed constituting a suspensor, the cell-division being preceded by changes in the protoplasm, as in the case of Thvja. The third cell is formed subsequently to the others, and is of a hemispherical form, sepa- rated by a partition from the second cell of the suspensor, but having no direct communication with the cell-w T all or intine ; nevertheless the mode of formation of the partition is the same- That portion of the protoplasm POLLEN-GRAINS OF GTMNOSPEEMIA. 627 in contact with the partition separating it from the second cell of the sus- pensor now secretes a cell-wall over the hemispherical portion of dense homogeneous protoplasm found in that situation, and the new cell is formed. In the Abies type the two first cells of the suspensor are formed as above indicated ; but the third is formed by true free-cell formation, and is quite detached from the suspensor. In the early stages it is like that of Pinus ; but subsequently it may become completely isolated and divided into secondary and tertiary subdivisions, often in a spiral direction. In the germination of the pollen-tube, the intine of the larger of the two cells into which the primitive one divides alone forms the tube. In Pinus there may be more than one pollen-tube, in either case very large. In it is sometimes formed, by free-cell formation around a nucleus, a large cell, which becomes ultimately liberated by the absorption of the walls of the pollen-tube. The new cells formed by free-cell formation and attached to the sus- pensor, as well as those formed freely in the pollen-tube in the course of its formation, are to be considered, according to this author, as the rudi- ments of the mother cells of the antherozoid, the presence of which Hofmeister had previously suspected. The cells of the suspensor cor- respond precisely to the cells of the male prothallus of Isoetes. In the Phanerogams, when a pollen-grain falls upon a stigma in its proper or " receptive " state (known by the presence of a sac- charine secretion), the inner coat is protruded in the form of a blind pouch (fig. 602, Ti) from one or more of the pores or slits of the pollen-cell itself, and, nourished by the stigmatic secretions, grows into a tube of great tenuity, which makes its way through the loose stigmatic cells, and passes down the canal of the style into the cavity of the ovary, there following the course of the pla- centas when the ovules are numerous. In the Gymnosperms the pollen-grains fall at once upon the ovules and pass into the micropyle, sending down their pollen- tubes (here developed from one of the daughter cells, which pene- trate through the proper coat of the pollen-cell) into the sub- stance of the nucleus of the ovule, towards the deep-seated embryo- sac. The formation of imperfect pollen-tubes may sometimes be caused by placing pollen-grains in syruny fluids ; but when they are placed in dilute sulphuric acid &c. the extrusion of the inner coat which results is mostly a process of mechanical expansion, and the projecting pouches soon burst and discharge the contents of the cell, owing to endosmotic action. Ovules of Phanerogamia. The ovules of Phanerogamia are all constructed according to some modification of one general plan, which has been already described (p. 137). In the succeeding paragraphs some further details as to its history may be given. 2s2 628 PHYSIOLOGY. Ovules of Gymnospermia. The ovules of the Gymnosperms, Pinaceae and their allies and Cycadaceae, are produced upon open carpels, so that the pollen- grains have direct access to the micropyle (fig. 607, A, a). In Pinus two of these occur at the base of the carpel] ary scale. Each consists of a nucleus (or macrosporange) with only a single inte- gument (fig. 605, A). In this first figure the primary embryo-sac, or " macrospore," is represented in the centre as still very small. Before the pollen-grains fall on the micropyle of the ovule, the Pig. 604. Diagrammatic section of an ovule : a, nucleus ; b, embryo-sac ; c, inner coat ; d, outer coat; e, micropyle ; f, chalaza; g, funiculus. Fig. 605. Young ovules of Pinus. A. Vertical section at the time when the primary embryo- sac is a small cell in the centre of the nucleus: m, micropyle. B. Section of an older ovule : m, micropyle with two pollen-grains on the apex of the nucleus; e, the primary embryo-sac filled with cellular tissue. Magn. 50 diam. embryo-sac becomes filled up, by free-cell formation, with delicate cellular tissue (endosperm-cells), which soon disappear, to be re- placed by a fresh development at a subsequent period. This en- dosperm is the female prothallus. Fig. 605, B, represents a section of an ovule with an embryo-sac (e) filled up in this way, and two pollen-grains which have penetrated into the micropyle (m) pushing their pollen-tubes into the substance of the nucleus. In the upper part of the mass of the last formed endosperm (), from five to eight cells are found to expand more than the rest, forming secondary embryo-sacs or corpuscula. These are not formed in the superficial cells of e, but from cells of the second layer, so that each is separated from the membrane of the primary embryo- sac by one cell (fig. 606, A) These corpuscula, as they were called by Robert Brown, their discoverer, are very much like the arche- gonia in the internal prothallium structure of Selaginella. After a time the secondary embryo-sacs divide into an upper or neck-cell, and a lower or central cell, egg or oosphere. The neck-cell speedily OVULES OF GYMNOSPEKMIA. 629 divides and subdivides to form the rosette, which surmounts the central cell. In the upper part of this latter is then formed, from subdivision of the nucleus, a very delicate cell, which is called the canal-cell. The mature corpuscle therefore consists of a large central cell surmounted by a rosette of small cells placed immedi- ately beneath the wall of the primary embryo- sac, or separated from it by a funnel-shaped space. The pollen-tube, after remain- ing passive for a variable space of time, takes on active growth, traverses the endosperm, and arrives at the embryo-sac by the time the corpuscula are developed. It penetrates the wall of the em- bryo-sac, enters into and dilates the funnel-shaped space just mentioned, passes down between the cells of the rosette, pushing them on one side (Taxinece, Cupressinece), or causing their absorp- tion and disappearance (^Abietinece) as well as that of the canal-ceil, and finally penetrates into the cavity of the central cell. The changes which take place in this latter are, according to Stras- burger, these : disappearance of the original nucleus, and forma- tion of four to eight new nuclei by condensation of the protoplasm and subsequent secretion of a cellulose wall around them. In this Development of embryo in Coniferae (Pinus) : A, upper part of the embryo-sac, with two corpuscula or archegonia ; B, the same more advanced, the right-hand one with a pollen- tube (p t) in its canal and germinal corpuscles (a) at the base ; C, D, E, successive stages of development of a in B ; F, G-, H, development of these cells into suspensors, at the end of one of which the embryo is produced, shown in I (em)'. Magn. 100 diam. way four to eight new cells are formed by free-cell formation in the central cell after fertilization ; these new cells divide so as to form cellular filaments, which break out through the bottom of the endosperm into the substance of the nucleus (fig. 606, F, Gr, H). At the ends of these filaments cell-division again occurs (I) ; and from the apex of one of these suspensors or proenibryos is developed, by repeated cell-division in various directions, the embryo (I, em}. At one stage (in Thuja} a single apical cell, the terminal one of a 630 PHYSIOLOGY. group of five, from which ultimately all the tissues of the embryo are formed, recalls the single apical cell of Cryptogams, but it is soon lost by subdivision. As there are several corpuscles, and each produces four suspensors. a large number of rudimentary em- bryos are developed ; but usually only one of all these rudiments is perfected. That embryo which is fully developed gradually increases in size, and most of the structures above described disappear, so that the ripe seed exhibits a sin- gle embryo imbedded in a mass of endosperm or albumen (fig. 607, D), the latter originating apparently from the nucleus of the ovule. The radicle is covered by apileorhiza, which is intimately blended with the substance of the endosperm. The phenomena presented in other Pinaceae, in Taxus, and in the Oy- cadaceae agree in most of the essen- tial particulars. There appear to be Some Curious peculiarities in the D ; Vertical section of the seed (C/a). E. Gnetaceae, which are not yet com- pletely made out. In Welwitschia, whose anomalous structure has been described at pp. 137, 363, the embryo- sacs grow out of the primary embryo-sac *. Pinus sylvestri*. A. Carpel with two naked ovules ; a, micropyle. B. Carpellary scale of ripe cone, with seeds (a). C. A seed separated (a), having a wing-like process D. Vertical section of the seed (C, a). Young plant from germinated seed. Ovules of A.ngiospermia. The early history of the ovules of this group is analogous to that of the ovules of Gymnosperms, excepting in the particular that they arise from the placentas existing in closed ovaries in- stead of being developed upon the exposed surfaces of open carpels. The ovules arise from the placentas as minute cellular papillae (fig. 608), which gradually take form, and exhibit the regions and the modifications of their arrangement described in an earlier section. The annexed drawing (fig. 609) actual views, drawn to a scale, of the development of the minute ovules of Orchis illustrates the gradual for- mation of the coats, &c. Fig. C09, a, represents a young ovule projecting out from the placenta, before it has become anatropous ; the nucleus here consists merely of the embryo-sac surrounded by a single layer of cells, * For further details, which the restrictions imposed by the size of this volume forbid us to enter upon, the student should consult Strasburger's 'Befruchtung bei den Coniferen,' his ' Coniferen und Gnetaceen,' and especially his treatise ' Zellbildung und Zelltheilung.' OVULES OF AKGIOSPEEMIA. 631 which layer is absorbed as the ovule grows (c, d), so that the embryo-sac constitutes the whole nucleus of this ovule. In a the inner integument partially encloses the nucleus ; in b the outer integument has grown up over this to a certain extent; and both are still more developed in c, where the inner coat has covered up the nucleus (leaving the endostome, p. 137), but itself projects from the outer coat. In d the outer coat has Fig. 608. Fig. 609. o Fig. 603. Ovules, showing gradual formatiou of coats over the nucleus and progressive cur- vature. Fig. 609. Development of the ovule of Orchis Morio : o, a young ovule, with the nucleus projecting from the inner coat ; b, an older ovule becoming anatropous, with the outer coat growing up over the inner ; c, section of a more advanced ovule ; d, section of an ovule with the pollen-tube (pt) passing down the micropyle, and in contact with the embryo-sac ; f, an embryo-sac extracted, with three germinal corpuscles ; g, another, with the end of a pollen-tube adherent. Magn. about 100 diam. grown up over the inner, and the micropyle or foramen (p. 137) consists of a wide exostome and a narrow endostome, into which the pollen-tube (p t) has penetrated. Ovules are seldom so small, or composed of so few cells, as the fore- going; more frequently the nucleus is a cellular mass of some size, and the coats are composed of several strata of cells. The outer coat is the primine, the inner the secundine, of Mirbel. At the epoch when the pollen is scattered from the anthers, the ovule presents the characters which are illustrated in fig. 610, which represents the anatropous ovule of the garden Hyacinth. The nucleus (fig. 610, n) is surrounded (in this case) by two coats (s & p\ which are perforated above by a canal, the micropyle (m) ; at the base of the nucleus is the chalazal region (c), whence the integuments (s & p) arise, and where the raphe (r) 9 with its spiral vessels, ends. In the centre of the nucleus is a long sac (e s), the 632 PHYSIOLOGY. embryo-sac. It is a large cell, filled Fig. 610. with watery fluid and protoplasm, and contains at its summit the germinal corpuscles (e v], globular or oval masses of protoplasm, one of which becomes the germinal vesicle. Some authors assert that these corpuscles are cells "before impregnation; but we hold that they are merely corpuscles of proto- plasm, or rather free primordial utricles (p. 495), like the unfertilized spores of Fucus (p. 443). In fig. 612, A, e v, is shown the condition before fertilization in Santalum. Most observers consider that the germinal vesicles exist before fecundation ; but Tu- lasne inclines to the belief that they are the first results of that process. In some cases, at the bottom of the einbryo-sac, small cells (antipodal cells) have been seen, which are formed before the germinal corpuscles by free-cell formation, have only a temporary existence, and disappear after fertilization. The purport of these cells is not known. Embryo-sac. The embryo-sac is usually solitary, but in Crucifers there are several, one of which alone becomes fertilized. It exhibits different modes of development in different Orders of plants. In the OrchidaceaB the cell which constitutes the embryo-sac (fig. 609) very soon oblite- rates the surrounding cells, here a single layer, and comes to form the entire nucleus (c, d, e, /). In the Composite an analogous condition is met with. In the Leguminosae the embryo-sac sometimes expands so much as to cause the absorption of the inner integument even before fertilization. In Gryninosperms the embryo-sac remains sur- rounded by layers of cells belonging to the nucleus till after fertilization has taken place. The embryo-sac often only occupies a moderate part of the nucleus (fig. 610), and may then be a simple cylindrical or oval sac, or run out into pouches or diverti- cula, as occurs especially in Scrophulariaceae. A remarkable condition occurs in Santalacese, Vertical section of the ovule of the garden Hyacinth, just before impregnation : f, funiculus ; r, raphe ; c, chalaza ; n, nucleus ; , inner integument; p, outer integument ; m, micropyle ; es, embryo-sac ; ev, germinal cor- puscles,one of which gives origin to the embryo. Magn. 25 diam. Fig. 611. Vertical.section of the ovary, containing one ovule, of Carduus : s, base of the canal of the style ; o, body of the ovule ; pt, bundle of pollen-tubes, descend- ing from the stigma; es, embryo-sac ; e, nascent embryo. Magn. 25 diam. OVULES OF AKGIOSPERMIA. 633 where the apex of the embryo-sac grows out from the micropyle to meet the pollen-tubes, and in such plants as EpJiedra or Welwitschia, wherein the coat of the ovule is prolonged into a styliform process. In Santalum album and some other plants the embryo is developed entirely outside the nucleus, in the protruded part of the sac. Schacht says that the embryonic vesicles in Santalum, Crocus, and a few other genera, are much elongated ; the lower end becomes rounded off into a cell, while the other end projects beyond the embryo-sac into a slender tubular prolongation into the micropyle. The sides of this are striated and gave rise to the appellation j^/orm appendage, which is considered by Strasburger to correspond with the canal-cell of Cryptogams. It is not clear whether the protru- sion just alluded to is really from the embryo-sac or from the germinal vesicle. Passage of the Pollen-tubes. When the pollen-tubes are formed in the stigma they gradually elongate by growth at the apex into tubes which pass down the canal of the style when this exists, the latter being sometimes several inches long. The time occupied in this growth varies from a few hours to several weeks. In the Hazel-nut and other similar plants the pollen falls on the stigma in spring before the ovules are even formed. The pollen-tubes derive their sustenance from the tissues through which they pass, and mostly die away above as they grow below ; and the stigma withers soon after the pollen-tubes have penetrated. It is remarkable that the stigma remains fresh for a considerable time in unfertilized ovaries ; and in the occasional cases of development of an unfertilized ovule, which has been observed in some dioecious plants, as Ccelebogyne, Hemp, Mercurialis, &c., the stigma does not wither. Pollen-tubes. The pollen-tubes are exceedingly minute, the diameter averaging from 4-^0-5- or TOFO f an i ncn But Amici estimated the number of pollen-tubes formed from the pollen-masses of Orchis Morio at 120,000. Experiments have shown, however, that, under favourable circumstances, a very few pollen-grains suffice for even a many-ovuled ovary. Kolreuter found that when 25 pollen-grains were placed on the stigma of Hibiscus Trionum, 10-16 ovules were developed ; with 50 or 60 grains, above 30 ovules ; and 1,2, or 3 at the most sufficed for the single ovules of Mirabilis Jalapa and M. lonyiflora. The bundle of pollen-tubes proceeding from the style is distributed in fractions, or partial bundles, to the placentas, when several of these exist. The pollen-tubes make their way to the points of the ovules (figs. 611, p t, & 609, d, p ), and one or two enter the micropyle of each. Gene- rally speaking, the tube ceases to elongate when it reaches the outer sur- face of the apex of the embryo-sac. Sometimes it runs onwards a little way (fig. 609, #), often depressing the membrane of the embryo-sac a little. According to Hofmeister, it actually breaks through into the embryo-sac in Canna. In all cases it contracts a firm adherence, and possibly a kind of conjugation takes place (fig. 612, B). The end of the 634 PHTJSIOLOGT, pollen-tube iy always intact and without visible apertures, fc never con- tains any cellular formation within it The arrival of the pollen-tnbe upon the surface of the embryo- Kg- 615. Fig. 613. 5 F. (2 C.) 672 GEOGRAPHICAL AND GEOLOGICAL BOTANY. for the month of September. The southern boundary of this zone in the northern hemisphere corresponds pretty nearly to the limit of distribution of the Oak in Europe and the east coast of North America, the northern boundary to the limit of the distribution of trees. The striking characteristic of this zone is, indeed, the predominance of the Coniferous trees in the woods, giving place northwards to the Birch and Alder, and generally alternating with Willows where the soil is moist. Green pastures occur universally, especially adorned with showy flowering herbs in the spring and summer. 7. The Arctic Zone. The equatorial boundary is the isotherm of 36 -5 F. (2 C.) for the month of September, or the polar limit of arborescent vegetation in the northern hemisphere ; the polar boundary is the isotherm of 41 F. (5 C.) for the month of July. The vegetation of this zone corre- sponds to what we understand commonly as Alpine shrubs, consisting chiefly of prostrate shrubs, with a peculiar tortuous and compact habit of growth, such as the alpine Rhododendra, Andromedae, the dwarf Birch and Alder, the Bog-Myrtle and dwarf Willow, with a variety of low-growing perennial herbs, remarkable for the comparatively large size and bright colour of their flowers. Sedges and Cotton-grasses occur socially, in some places covering extensive tracts ; but the grassv pastures of the last zones are replaced to a great extent by tracts covered with Lichens. 8. The Polar Zone. Equatorial boundary, the isotherm of 41 F. (5 C.) for the month of July ; polar limit, the isotherm of 36 '5 F. (2 C.) for the same month. This zone is characterized by presenting, in the four to six weeks of summer, an alpine vegetation devoid of even shrubs, and con- sisting of herbaceous perennials of dwarf habit, such as Saxifrages, Ra- nunculi, Pyrolse, Potentillse, Dryas, Draba, &c., and possessing, moreover, certain genera (such as Parrya, Phippsia, and others) which, although they extend into the Arctic zone, are not met with in the alpine regions of the mountains of the more southern regions. In Spitzbergen, the number of Cryptogamic plants is remarkable, the Lichens alone equalling the Flowering plants, and predominating even in mass as well as number of species. Sect. 2. KEGIONS OF ALTITUDE. It is well known that the lofty mountains lying within the tropics exhibit a graduated variation of character in their vegeta- tion, and that those which rise above the limit of eternal snow display more or less distinctly marked regions, representing the zones lying between the plains at the foot of such mountains and the eternal ice of the polar zone. Humboldt divided the surface of tropical mountains into three zones, representing the tropical, temperate, and frigid zones of the globe, and indicated the principal subdivisions of these regions. Meyen attempted to lay down a more systematic representation of the conditions in question, corresponding to his division of the DISTEIBUTION OF PLANTS IN ALTITUDE. 673 earth's surface into zones. Great difficulty interposes here in any attempt at generalization, since local conditions, arising from aspect, and conformation of surface, either giving more or less of preci- pitous character, accompanied by sudden changes, or producing elevated plains, &c., cause such great differences, even within the limits of single mountain-systems, that no absolute rule can be ap- plied. The rules laid down by Meyen apply pretty well to his zones within the limits of Europe ; but, in the delineation of the regions of altitude of greater extent, great variation presents itself near the equator. The Snow-line. According to Meyen's views, the snow-line, beginning at the polar zone, rises between 1900 and 2000 feet above the level of the sea, and in the equatorial zone to 15,500 or 16,600 feet ; and he divides the regions of altitude in accordance with this, raising each region between 1900 and 2000 feet in each zone, as he approaches the equator. Now at North Cape, which lies near the polar limit of our subarctic zone, and in Iceland, which is crossed by the same limit, the line of perpetual snow is at about 2000 feet ; we may therefore take this as the snow-line of the arctic zone. The equatorial limit of the subarctic zone falls in Southern Norway, where the snow-line is at about 4000 feet ; while the equatorial limit of our cold temperate zone is not far removed from the Alps and Pyrenees, where the snow-line rises to 8000 feet and more. In the south of Spain, lying within the warm temperate region, snow lies in isolated patches below 11,000 feet. In the district of Sierra Nevada, which is one of the best-known of the mountains of this zone, as regards vegetation, there is a subtropical region up to 600 feet, the true warm temperate vegetation extends up to about 4000 feet, a cold temperate vegetation from about 4000 to 6500 ; the vegetation then passes into a condition allied to the subarctic, but without trees, and characterized by shrubs of a similar nature to those of the arctic zone. This region extends to 8000 feet ; and thence to the summits of 11,000 feet there is an alpine summer vegetation (snow lying for eight months out of the twelve), which, again, is intermediate in character between those of the arctic and polar, con- sisting chiefly of perennial herbs like the latter, but presenting a formation of turfy pasture to some extent in the warm season. In the Caucasus the snow-line is much higher. In the subtropical zone, on the Peak of Teneriffe, we find the vegeta- tion of the warm temperate zone from about 2000 to 4000 feet, a repre- sentation of the cold temperature from 3000 to over 6000 feet ; at about 8000 feet the climate is subarctic. This mountain does not reach the snow-line. In Mexico, lying in our tropical zone, the lines are respectively shifted up in about the same ratio. We see throughout, then, a deviation from Meyen's ratio, in the tendency of the colder zones to widen out on the mountains of warmer zones j but this is partly owing to our dividing the zones according to temperature, and not according to latitude. If we attempt to lay down the conditions of the mountains of Asia under a similar point of view, we find greater deviations. The mass of elevated land in Central Asia modifies all the climatal conditions very much. The snow-lines of the mountains of the cold-temperate and warm- 674 GEOGRAPHICAL AND GEOLOGICAL BOTANY. temperate zones rise to 14,000 feet j that of the Himalayas to 18,000 feet in the northern parts. Our data scarcely suffice for the illustration of these modified conditions, and therefore we have confined ourselves to a limited number of the best-explored mountain-regions of the Old and New Worlds. We now give a brief sketch of the characteristics of the different regions of altitude, as classified by Meyen. 1. Region of Palms and Bananas. Corresponding to the equatorial zone, and already characterized under that head, p. 669. 2. Region of Tree-Ferns and Figs. Corresponding to the tropical zone, p. 670. The genus Ficus is most prevalent in the elevated forests of the equatorial zone of the East Indies, giving them a remarkable character of gloomy grandeur and impervious density. 8. Region of Laurels and Myrtles. Corresponding to the subtropical zone, p. 670. 4. Region of Evergreen Trees. Corresponding to the warm-temperate zone, p. 670. 5. Region of Deciduous Trees. Corresponding to the cold temperate zone, p. 671 ; but this region seems to be absent from the mountains in many parts of the tropical and equatorial zones, since the tree-limit is carried down by peculiarities of climate, which, on the other hand, favour the advance of more southern forms into the upper regions. In Java and Sumatra, stunted trees of the class belonging here replace the dwarf Conifers of European mountains, and form the tree-limit far below the altitude at which forests of tall Conifers occur in the more northern Himalayas, a condition explained in some degree by the local circum- stances of the equatorial mountains, which are deficient in the supplies of moisture furnished by the vast masses of snow resting perpetually upon the Himalayas. 6. Region of Conifers. Corresponding to the subarctic zone, p. 671. This zone, characterized by the growth of Pines and Firs, is well repre- sented on most mountains, with the exception of the Peruvian Cordilleras, where the Escallonieae are said to be substituted for them. But the Conifers do not always form the uppermost belt of trees, even when they flourish in a well-defined region. Thus the region of the Conifers, in a general sense, which reaches to the tree-limit with Pines in the Alps, Pyrenees, and the Andes of Mexico, includes, in the Scandinavian mountains, in the Himalayas, and the Caucasus, a region of Birches, which rise out of it to form the last representatives of arboreal vegetation. 7. Region of Alpine Shrubs or of Rhododendra. This region corre- sponds to the Arctic zone, p . 672. In the Himalayas, dwarf Willows, Juni- pers, and species of Ribes or Current seem to represent the vegetation of this region ; while on the Andes of Quito the genus Befaria appears to cor- respond in its geographical development to the Rhododendra of the north. 8. Region of Alpine Herbs. Corresponding to the polar zone, p. 672, usually presenting only patches of vegetation scattered over a broken surface of ground, covered during the greater part of the year with snow, and ex- hibiting accumulations in all seasons in sheltered spots. Lichens abound here ; Lecidea geographica has been found in most diverse localities where bare rock rises above the ground, forming generally the last trace of vege- tation. The plants of this region are remarkable in many respects, in BOTANICAL BEGIONS. 675 none more than the. beauty and comparatively large size that usually cha- racterize their flowers. They are mostly of perennial growth, since, although the severe cold prevailing throughout the greater part of the year is unfavourable to the maturation and preservation of seeds, the thick covering of snow protects established plants from the severe frost ; and it is known that they are arrested in warmer regions where winter frosts prevail without great accumulations of snow, precisely because they are then incapable of bearing the cold, to which they are directly exposed. The great discrepancies existing between mountains occurring in the same zone indicate that local circumstances must have most powerful in- fluence in determining the altitudes attained by the various classes of vegetation. We are not in a position to give the real temperatures of regions of altitude with any accuracy in most cases, or these would pro- bably greatly assist in ascertaining the direct causes of aberration ; for differences of temperature certainly accompany the difference of elevation attained by particular forms of plants. Good examples of the influence of the form and local conditions of mountains are furnished by Teneriffe, Ararat, the Himalayas, and the Rocky Mountains of North America. The first is an isolated mountain, exposed to the equalizing influence of the ocean ; the second an isolated mountain situated in the interior of a continent ; the two chains are portions of enormous systems of mountains extending over large regions in the interior of continents. To work out this subject thoroughly, however, it is necessary to observe not only the conditions of different mountains, but those of the different declivities of the same mountain ; since, when great elevations are attained, chains of mountains form the boundaries of local climates, and present different conditions on the two faces. Sect. 3. DIVISION or THE GLOBE INTO BEGIONS CHABACTEBISTIC VEGETATION. The character of the vegetation of different regions is influenced not merely by climate, but by the more remote causes referred to in the last Chapter, which have led to the distribution of plants over more or less extensive areas, and their restriction within narrow limits in other cases ; further, by the habit of plants, as by a social mode of growth, by size, &c. Many attempts have been made to divide the earth's surface into Botanical Eegions, according to their characteristic vegetation. None of these can be regarded as satisfactory ; but perhaps the generalizations of Schouw and Grisebach are, on the whole, those which suggest most to the student. We therefore introduce here a brief account of the regions into which those authors divide the globs. Phyto-yeoyraphic Regions. The regions established by Schouw are founded on the following principles : 2x2 676 GEOGEAPHTCAL AND GEOLOGICAL BOTANY. 1. At least one half of the known species of plants of the tract constituting a botanical region are peculiar to it. ' 2. A fourth part of the genera of the region are either peculiar to it, or have so decided a maximum that they are comparatively rare in other regions. 3. The individual Orders of plants are either peculiar to the region or have a decided maximum there. Grisebach's regions in many respects correspond with those of Schouw ; each of them is further divided into zones according to altitude above the sea-level up to the line of perpetual snow. The limits of each region are fixed by mountain barriers, the presence of seas, and other impediments physical and climatic, and therefore varying in particular instances. 1. Region of Mosses and Saxifrages (Arctic- Alpine, or Wahlenberg's Region). Mean temperature. Polar regions, 2-41 Fahr. (-17 to -5 C.). Mountains in the south, 21-37 Fahr. (-6 C. to -3 0.). This corresponds to Grisebach's Arctic region, and includes those regions which lie beyond the limits of forest vegetation. The period of vegetation only lasts a few weeks, Character, Characteristic and predominant genera Ranunculus, Ara- bis, Draba, Arenaria, Dryas, Potentilla, Saxifraga, Rhododendron, Azalea, Gentiana, Pedicularis, Salix, Musci, Lichenes. Of the polar countries especially Coptis, Eutrema, Parrya, Diapensia, Andromeda, Ledum. Of the mountain regions Cherleria, Campanula, Phyteuma, Primula, Aretia, Soldanella. Dwarf perennial herbs with comparatively large ilowers of bright colours. Annuals and trees absent. ^Predominant shrubs and half-shrubs of the polar countries. Betula nana, Salix herbaceaand other species, Rubus Chamsemorus, Empetrum nigruro, Andromeda hypnoides, A. tetragona, Arbutus alpina, A. Uva ursi, Azalea procumbens, Rhododendron lapponicuin, Menziesia cserulea. Predominant shrubs and half -shrubs of the mountains. Juniperus nana, Alnus viridis, Salix reticulata, S. herbacea, Rhododendron ferrugineum, R. hirsutum, R. caucasicum, Vaccinium Myrtillus, V. uliginosum, Azalea procumbens, Arbutus alpina, A. Uva ursi, Empetrum nigrum. Plants ivhich approach very closely to tlie snow-line. Ranunculus gla- cialis, Saxifraga oppositifolia, Silene acaulis ; in the polar countries espe- cially, Agrostis algida, Ranunculus hyperboreus, R. nivalis, Saxifraga rivularis, S, cernua, S. nivalis, Papaver nudicaule, Draba alpina, Lychnis apetala, Diapensia lapponica. In the mountain-regions, Saxifraga inus- coides, S. bryoides, Cherleria sedoides, Aretia helvetica, A. alpina, Draba nivalis, Petrocallis pyrenaica, Arabia bellidifolia, Myosotis nana, Gentiana nivalis, Achillea nana, Linaria alpina. No cultivation in this region. The flora, as a whole, as tabulated by Hooker, is decidedly Scandinavian. Some of its members are universally diffused throughout the globe, even in the tropics (on mountains) j hence the Scandinavian flora is considered BOTANICAL EEGIONS. 677 to be the oldest existing flora. The most northern position in which flowering plants have yet been found is in Smith's Sound, in lat. 82 N., where Dr. Bessels found Draba alpina, Cerastium alpinum, Taraxacum dens leonis, and Poaflexuosa. (The principal authority on the subject of the Arctic Flora in its geographical aspect is Hooker, whose paper " On the Distribution of Arctic Plants " is included in the Linnaean Transac- tions, vol. xxiii.) 2. Region of Umbelliferce (North-European and North- Asiatic, or Linnceus's Region). Mean temperature, 29-46 Fahr. (-2 to -8 C.). This corresponds to Grisebach's Europseo-Siberian Forest region, and is characterized by uniform temperature and absence of a dry season. The Atlantic coast is milder than the inland continental regions. Grise- bach establishes 7 zones of altitude : 1. The zone of the Sweet Chestnut, Castanea vesca ; 2. The zone of Plnus picea (Germany) ; 3. The zone of the Turkey Oak, Quercus Cerris (Hungary) ; 4. The central Russian forest zone (Oaks) ; 5. The northern zone of Conifers (Larches, Pines, Firs, with Birch) ; 6. The zone of Quercus mongolica ; and 7. The zone of Betula Ermanni. General Character. Umbelliferae, Cruciferse, Coniferae, Amentaceae, Graminaceae, Carices, Fungi, Cichoracese, Cynareae ; in Asia, more par- ticularly, saline plants (such as Salsola and Salicornia) and Astragaleae. Luxuriant pastures ; forest trees with deciduous leaves ; a few Heaths. Predominant trees and shrubs. Pinus sylvestris, P. cembra, P. sibirica, Abies excelsa, A. pectinata, Larix europaea, Juniperus conamunis, Betula alba, Alnus glutinosa, A. incana, Fagus sylvatica, Quercus pedunculata, Q. sessilifl ora, Carpinus Betulus, Castanea vesca, Salices, Populus tremula, Cory his Avellana, Ulmus campestris, Calluna vulgaris, Primus spinosa, Pyrus Aucuparia, Acer Pseudo-platanus, A. platanoides, A. campestre, Tiii a platyphylla, T. microphylla. Cultivated plants. Cereals : Rye, Barley, Oats, Wheat, Spelt, Maize, Millet (Panicum miliaceum) , Buckwheat, Potato. Barley extends furthest to the north, followed southward by Rye, Oats, and Wheat. Fruits. Apple, Pear, Quince, Cherries, Plums, Apricot, Peach, Mul- berry, Walnut, Grape, Currant, Gooseberry, Strawberry, Melons. Esculent vegetables. Cabbage, Rape, Turnip, Radish, Mustard, Peas, Beans, Lentils, Spinach, Beet, Cucumber, Gourd, Carrot. Fodder plants, fyc. Clovers, Vetches, Lucerne, Rye-grass ; Hops, Flax, Hemp, Tobacco. (The publications of Ledebour, Regel, and nume- rous other Russian botanists should be consulted as to this region.) 2 a. The Steppe Region. This region, as laid down by Grisebach, extends from the Black Sea to the frontiers of China, and from Southern Siberia to the Himalayas, thus including almost the whole of Central Asia. The climatal conditions are a severe winter, a short spring, a burning summer succeeded by winter. 678 GEOGRAPHICAL AND GEOLOGICAL BOTANY. The plants, then, native to it must be capable of growing in the short spring and, while at rest, be able to endure prolonged drought and intense extremes of temperature. Bulbous plants, plants with stift'spiny branches and email foliage, or plants densely covered with hairs, abound. Salt plains are abundant yielding a peculiar vegetation, including many Che- nopods, such as the Saxal Anabasis ammodendron. (Humboldt's ' Asie Centrale ' should be consulted on this region.) 3. Region of the Labiates and Caryophyllece (Mediterranean^ or De Candolle's Region}. Mean temperature, 65-73 Fahr. (18-23 C.). This, the Mediterranean region of Grisebach, is characterized clima- tically by very hot dry summers and mild winters. Plants grow in spring, rest in the hot dry season, and g'row again in autumn. Schouw includes the Atlantic islands in this botanical region. Character. Labiatse, Caryophyllese, Boragiueae, Cistinere, Liliaceae ; the Orders cited in the preceding region, but mostly less prevalent, espe- cially the Carices. Representatives of tropical Orders Palmae, Tere- binthaceae, Lauracege, Orders which increase towards the equator be- coming more numerous: Leguminosa3, Malvaceas, Solanaceae, Euphor- biacese, Urticaceae. Genera. Adonis, Trigonella,Trifoliurn,Medicago, Genista, Cytisus, Sca- biosa, Anthemis, Achillea, Verbascum, Narcissus ; many evergreen trees and shrubs ; a greater number of woody plants than in the second region j pasture less luxuriant ; a winter flora existing. Predominant trees and shrubs. Evergreen trees and shrubs form a feature of the flora. Pinus Pinea, P. Pinaster, P. halepensis, P. Laricio, Oupressus sempervirens, Juniperus phoenicea, J. macrocarpa, Quercus Cerris, Q. pedunculata, Q. sessiliflora, Q. Ilex, Q. Suber, Q. ^Egilops, Q. coccifera, Q. infectoria, Castanea vesca, Platanus orientalis, Alnus cordifolia, Corylus Colurna, Ostrya vulgaris, Acer monspessulanum, A. neapolitanum/ Pistacia Lentiscus, P. Terebinthus, Ceratonia siliqua, Cercis siliquastrum, Genista scoparia, Mespilus pyracantha, Prunus lauro- cerasus, Tamarix gallica, T. africana, Myrtus communis, Punica Grana- tum, Opuntia vulgaris, Viburnum Tinus, Arbutus Unedo, Erica arborea, E. scoparia, Rhododendron ponticum, R. maximum, Cisti, Phyllyrea lati- folia, P. angustifolia, Ornus europsea, O. rotiuidifolia, Nerium Oleander, Rosmarinus oflicinalis, Ephedra distachya, Chama3rops humilis, Ruscus aculeatus, Smilax aspera, Tanius communis. (The highest parts of the mountains here belong to the first region, the middle elevations to the second region.) Many plants have been introduced and become quasi naturalized ; such as the Date-Palm, Agave americana, Opuntia^ Euca- lyptus globulus, &c. Cultivated plants. The same as in the preceding region j but the follow- ing are more rare, or only seen on the mountains Rye, Currants, Goose- berry, Buckwheat, and Hop ; while the following are added : Cereals. Rice, Millets (Sorghum vulgare, Panicum italicum). Fruits. Figs, Almond, Pistachia-nut, Lemon, Citron, Sweet and Seville Oranges, Prickly Fig (Opuntia), Water-Melon, Olive, the latter being characteristic. BOTANICAL BEGIONS. 679 Esculents $c. Melongena, Tomato, Anise, Coriander, Cotton, White Mulberry, Saffron, Sumach, Lupins, Sainfoin. CJmracteristic forms. Sempervivum arboreum, S. canariense, S. tor^- tuosum, &o., Ilex Perado, "Cacalia, Kleinia, Sonchus fruticosus, Arbutus callicarpa, Ardisia excelsa, Ceropegia aphylla, Echium giganteurn, &c., Laurus foetens, Euphorbia balsamifera, E. canariensis, Myrica Faya, Pinus canariensis. 4. Region of Asteres and Solidagines (Northern North-American, or Michaux's Region). Mean temperature, 9-59 Fahr. (12-15 C.). The northern part of this region corresponds to the Europaso-Siberian region of Grisebach (p. 077), the Califoruian coast represents the Medi- terranean region, while the central prairies are the analogues of the Asiatic steppes. The American forest region has a lower temperature than that of Europe. New York has about the summer temperature of Rome and the winter temperature of Copenhagen. The United States Flora, accord- ing to Gray and Hooker, consists of three main elements, an endemic American, a European, and an Asiatic ; while that of the temperate Old "World is, in a continental point of view, binary Europe and Asia having many types in common, but very few representatives of the strictly Ame- rican flora. The distribution of North-American plants, unlike the Euro- pean, is mainly in a meridional direction, the difference of the floras of the Eastern, Central, and Western States being wonderfully great. The European components extend over the whole breadth of the continent, diminishing, however, to the westward. The American components pro sent many localized genera, inhabiting the Eastern, Central, and Western States respectively ; they increase in numbers and peculiarity, as also in restriction of range, towards the west. The Asiatic components are found both in the Eastern and Western States, but hardly at all in the Central ; and some of them are common to both the east and west, while others are peculiar to each. But whereas the European components prevail on the side towards Europe, the maximum of Asiatic represen- tation is on that remote from Asia. This has been conspicuously shown by Gray's discovery, in the Eastern States, of single representatives of Japanese genera previously supposed to be monotypic ; and what is most noteworthy is, that such representatives are in some cases extremely rare local plants, found in single and very restricted areas, indicating a dying- out of the Asiatic representation in America. Character. More species of Coniferse and Amentaceae than in the second region, but fewer Umbelliferae, Cruciferse, Cichoraceag, and Cynareas. Genera. Hydrastis, Sanguinaria, Hudsonia, Ptelea, Robinia, Gymno- cladus, Purshia, Gillenia, Decodou, GEnothera, Clarkia, Ludwigia, Bar- tonia, Claytonia, Heuchera, Itea, Hamamelis, Mitchella, Aster, Solidago, Liatris, Rudbeckia, Gaillardia, Vaccinium, Andromeda, Kalmia, Sabbatia, Houstonia, Hydrophyllum, Phlox, Monarda, Dodecatheon, Dirca, Hamil- tonia, Lewisia, Trillium, Medeola. Predominant trees and shrubs. Pinus Strobus, P. inops, P. resinosa, P. 680 GEOGEAPHICAL AND GEOLOGICAL BOTANY. Banksiana, P. variabilis, P. rigida, P. serotina, P. pungens, Abies bal- samea, A. taxifolia, A. canadensis, A. nigra, A. rubra, A. alba, Larix pen- dula, L. macrocarpa, Thuja occidentalis, T. sphaeroidea, Juniperus virgi- niana, J. Sabina, Taxus canadensis, Quercus, 25 sp., Fagus sylvatica, F. ferruginea, Castanea americana, C. pumila, Ostrya virginica, Carpinua americana, Corylus americana, C. rostrata, Alnus glutinosa, A. crispa, A. serratula, Betula nigra, B. papyracea, &c., Salix, 27 sp., Populus bal- aamifera, P. monilifera, &c., Myrica cerifera, &c., Platanus occidentalis, Liquidambar styraciflua, Juglans nigra, J. cinerea, &c., Ulmus americana, &c., Nyssa aquatica, Fraxinus alba, F. nigra, &c., Ornus americana, Kibes floriduni, R. aureum, &c., Vaccinium, 20 sp., Andromeda, 10 sp., Kalmia latifolia, K. angustifolia, K. glauca, Azalea viscosa, A. nitida, A. glauca, A. nudiflora, &c., Rhododendron maximum, Gornus florida, C. alba, C. ca- nadensis, &c., Hamamelis virginiensis, Spiraaa salicifolia, S. chamsedri- folia, S. opulifolia, S. hypericifolia, &c., Gillenia trifoliata, Cratsegus, sp., Cerasus pumila, C. nigra, &c., Purshia tridentata, Rubus, 20 sp., Pyrus sp., Robinia Pseud-acacia, R. hispida, Gymnocladus canadensis, Rhus typhina, R. glabra, R. venenata, R. toxicodendron, &c., Ptelea trifoliata, Ceanothus americanus, &c., Rhamnus alnifolius. &c., Ilex opaca, &c., Euonymus americanus, E. atropurpureus, Staphylea trifolia, Ampelopsis hederacea, Acer rubruni, A. dasycarpum, A. saccharinum, A. striatum, Negundo fraxinifolium, Xantboxylum fraxineum, X. tricarpum, Tilia gla- bra, T. pubescens, Liriodendron tulipifera. In the northern parts (to 50-55 N. L.) no cultivation. South of this the same plants as those cultivated in the second region, but Maize more extensively. The Californian climate is very uniform, the resting period of vegetation occurring in the dry summer, "vines, Olives, Maize, Oranges, and Iruit-trees of all kinds nourish here as well as Wheat, whilst the loftiest forest trees, the Sequoias, grow here as once they did in Britain. The Prairie Region corresponds to the Steppe Region of Central Asia. Extremes of temperature and great drought are the characteristics of this region; salt plains exercise a marked influence on the vegetation, but where irrigation is practicable the country becomes very fertile. The evidences of climatic changes in past eras of the existing flora of the continent, says Hooker, are seen in the prevalence of arctic and northern species of plants in the alpine zones of the meridional mountain- chains, the Appalachian, Rocky Mountains, and Sierra Nevada, even as far south as the 33rd parallel. These plants had spread southwards during a period of cold, and on its subsequent mitigation had retired to the lofty situations they now inhabit. To the former existence of a warmer climate we may partly look for the extension of Mexican types to the dry regions west of the Rocky Mountains up to the 41st parallel ; and to it may be attributed the remarkable northward extension of the Cacti in a very narrow meridional belt, scarcely 100 miles broad, along the eastern flanks of the same mountains, from their headquarters in New Mexico, in the 33rd, almost to the 50th parallel. (See Gray's ' Botany of the Northern United States,' and numerous publications of the American botanists on the Flora of their continent. Sir W. Hooker's Flora Boreali-Americana ' should also be consulted.) BOTANICAL BEGIOFS. 681 5. Region of Magnolice (Southern North- American) or Pursh's Region). Mean temperature, 59-73 Fahr. (15-23 0.)- This region is included with the preceding in Grisebach's North -Ame- rican Forest zone, but the vegetation is of a more tropical type, and ever- green exogenous trees are more abundant. Character. A certain approximation to the tropical vegetation ; Can- ness (Canna, Thalia), Palmae (Chamaerops), Yucca, Cycadese (Zamia), Lauras, Ipomasa, Bignonia, Asclepias, Cacteae (Mammillaria, Opuntia), Khexia, Passiflora, Cassia, Sapindus. Few Labiatae, Caryophylleae, Unibelliferae, Cichoraceae, Geranieae ; few species of Aster or Solidago. Trees with broad shining leaves and large flowers. Genera. Magnolia, Liriodendron, Illicium, Asimina, Dionaea, Pavia, Amorpha, Gleditschia, Baptisia, Petalostemon, Calycanthus, (Enothera, Claytonia, Rudbeckia, Liatris, Silphium, Kalmia, Houstonia, Frasera, Halesia, Dodecatheon. Predominant trees and shrubs. Magnolia grandiflora, M. glauca, &c., Illicium floridanum, I. parviflorum, Liriodendron Tulipifera, Asimina, sp., Pavia flava, P. macrostachya, &c., Amorpha fruticosa, &c., Gleditschia triacanthos, &c., Robinia viscosa, Cassia Tora, C. marilandica, &c., Acacia glandulosa, Calycanthus floridus, &c., Kalmia hirsuta, K. cuneata, Opuntia vulgaris, O. fragilis, O. missouriensis, Halesia tetraptera, H. diptera, Lau- rus Catesbyanus, L. caroliniensis, L. Benzoin, L. Sassafras, &c., Juglans fraxinifolia, Carya aquatica, C. myristiciformis, Liquidambar styraciflua, Carpinus americanus, Castanea americana, C. pumila, Platanus occiden- talis, Quercus, 25 sp., Taxodium distichum, I 3 inus Taeda, P. palustris, in the south Pinus australis covers large districts of sandy waste, Zamia integrifolia, Yucca gloriosa, Y. aloifolia, &c., Chamasrops Hystrix, C. Palmetto, C. serrulata. Cultivated plants. About the same as in the third region, with the ex- ception of the Olive. Cultivation of Rice more extensive. In the southern parts some tropical plants, especially Cotton and the Sugar-cane. 6. Region of Camelliece and Celastrinece ( Chinese, Japanese, or Kcempfer's Region). Mean temperature, 54-68 Fahr. (12-20 C.). This is the Chino- Japanese region of Grisebach. The climate is mode- rate with abundant, equally diffused rainfall. The country has been so long under cultivation, the forests destroyed, and much of the land altered by irrigation, that the natural characteristics are greatly obliterated. . Genera. Magnolia, Nandina, Eurya, Camellia, Thea, Celastrus, Ilex, Euonymus, Bumalda, Hovenia, Kerria, Spiraea, Gonocarpus, Lagerstroe- mia, Aucuba, Bladhia, Eleagnus, Polygonum, Pollia. Predominant trees and shrubs. Rhapis flabelliformis, Pinus sinensis, &c., Cunuinghaniia lanceolata, &c., Taxus nucifera, T. vertieillata, Salis- "buria adiantifolia, Cryptomeria japonica, Cupres^us pendula, Juniperus 682 GEOGKAPHICAL AND GEOLOGICAL BOTANY. yirginiana, Thuja orientalis, T. dolabrata, Quercus glabra, Q. glauca, Alnus japonica, Juglans nigra, Broussonetia papyrifera, Daphne odora, Laurus glauca, L. lucida, L. umbellata, L. pedunculata, Olea fragrans, Diospyros Kaki, Mespilus japonica, Sophora japonica, Acer japonicum, A. septem- lobatum, A. palinatum, &c., Camellia japonica, C. Sasanqua. Cultivated plants. Rice, Wheat, Barley, Oats, Dotira (Sorghum vul- gare), Millet (Eleusine corocana), Buckwheat, Sago (Cycas revoluta), Jaro (Arum or Caladium esculentum), Batatas or Sweet Potato ; various species of Pear, Apple, Crab, c.. Quince, Plum, Apricot, Peach, Medlar ; many species of Citrus (Oranges, Shaddocks, &c.), Melons. Tea, Rape (Brassica sinensis), Radish, Cucumber, Gourds, Water- Melon, Anise, Star- Anise, Soja, Nelumbium, Trapa, Scirpus tube- rosus, Convolvulus reptans, Beans, Peas, Solanum asthiopicum, Sesa- mum, Hemp, Paper Mulberry, Cotton, Indigo, Isatis indigotica, Urtica nivea. (The publications of Bunge, Maximowicz, Bentham (Hong Kong), Siebold, Miquel, Gray, Franchet, and Savatier are amongst the principal dealing with this region.) 7. Region of the Scitaminece (Indian^ or Roxburgh's Region). Mean temperature, 66-83 Fahr. (19-29 C.). This corresponds nearly to Grisebach's Indian Monsoon region, and is tropical in character, varying according to altitude and the direction of winds, the degree of moisture, &c. The growing period for plants is in the rainy season. It includes the Indo-Malayan region with the islands of Java, Borneo, New Guinea, &c. Character. The tropical Orders make their appearance, or become more abundant : Palmacese, Cycadaceae, Scitamineae, Aroidese, ArtocarpaceaB, TJrticaceae, Euphorbiaceas, Lauracese, Convolvulaceee, Bignoniaceaa, Apo- cynaceae, Rubiaceae, Leguminosa3, Terebinthacese, Meh'aceae, Guttiferee, Sapindaceae, Byttneriaceee, Malvaceae. The extra-tropical vanish, or only present themselves sparingly : Cari- ceae, Coniferae, Amentacese, Labiate, Boragineae, Compositae, Rosaceae, Caryophylleae, Cistacese, Cruciferse, Ranunculaceae. Genera. Uvaria, Grewia, Eriolaena, Garcinia, Buchanania, Crotalaria, Flemingia, Butea, Carpopogon, Janibosa, Gratiola, Tectona, Holmskiol- dia, Ficus, Phytocrene, Calamus. The trees are never without leaves. The number of arborescent plants is greater than outside the tropics. Large and splendid flowers. Many climbing, parasitical, and epiphytic plants. Predominant arborescent plants. Dilleniaornata, D. scabrella, Uvaria, sp., Michelia Champaca, &c., Bombax insignis, &c., Sterculia, sp., Astrapaaa Wallichii, Elasocarpus, sp., Calophyllum, sp., Garcinia, sp., Sapindus, sp., Swieteniafebrifuga, Cissus, sp., Aquilaria malaccensis, Semecarpus Anacar- dium, Melanorrhoea usitata, Mimosa, sp., Acacia, sp., Amherstia nobilis, Pterocarpus santalinus, Cassia fistula, Janibosa, sp., Gardenia, sp., Nauclea, sp., Uncaria Gambir, Diospyros Ebenum, &c., [Jrceola elastica, Bignonia, sp., Avicennia tomentosa, Tectona grandis,T. Hamiltoniana, Laurus Cassia, L. Cinnamomum, L. malabathrica, Tetrauthera, sp., Myristica, sp.,Hernan- dia sonora, Ficus religiosa, F. indica (the Banyan), F. elastica, F. benja- BOTANICAL EEGIONS. 683 mina, and many others; Cycas revoluta, Borassus flabelliformis, Cocos nucifera, Calamus Rotang, C. rudentum, C. Draco, &c., Areca Catechu, Dracaena Draco, Pandanus odoratissimus, Bambusa arundinacea. Cultivated plants. Rice, Millets, &c. (Panicuin frunientaceum, Eleusine coracana, Sorghum, sp.). Sago (Cycas circinalis), Yams, Ground-nut (Ara- chis), Cocoa-nut, Tamarind, Mango, Mangosteen, Bananas, Plantain, Rose- Apples (Eugenia, Jambosa), Guava, Oranges, Shaddock, Water-Melon, Sugar, Coffee, Cloves, Peppers, Ginger, Cardamoms, Turmeric, Cotton, Indigo, &c., Soja, Beans, Pulses (Dolichos, sp.), Opium, Poppy, &c. (The publications of Roxburgh, Royle, Blume, Wight, Hooker, Thomson, Miquel, Beccari, and others on the botany of this region are very numerous. Hooker's * Flora of British India ' will be the most complete enumeration.) 8. Region of Rhododendron-trees (JEmodic, or WallicKs Region). Altitude, 5000-12,000 feet. Mean temperature, 66 Fahr. (19 C.). Character. Included in Grisebach's Indian Monsoon region, of which it forms a marked subdivision. Tropical forms disappear or decrease : Palmaceae, Cycadaceae, Scitamineae, Euphorbiaceae, Convolvulaceae, Apo- cynaceae, Terebinthaceae, Leguminosae, Malvaceae, Anonaceae. Extratropical, especially European, forma come to light, or become more abundant than in 7, such as Cariceae, Amentaceae, Coniferas, Poly- goneae (Rumex, Polygonum, Rheum), Primulaceae (Primula, Lysimachia), Labiatae, Ericaceae (Rhododendron, Andromeda), Cichoraceae, Umbelli- ferae, Rosaceae (Potentilla, Rubus, Rosa, Pyrus, Mespilus, Prunus), Ace- raceae, Caryophyllaceae (Stellaria, Cerastium, Arenaria), Cruciferae, Ranunculaceae (Aconitum, Ranunculus, Thahctrum). The Orchideae and Ferns are very numerous. Other characteristic forms are the Genera. Alliurn, Paris, Plantago, Veronica, Rhinanthus, Pedicularis, Didymocarpeae, Gentiana, Swertia, Campanula, Valeriana, Galium, Conius, Viburnum. Most important trees and shrubs. Pinus Pindrow, P. Webbiana, P. excelsa, P. Khutrow, P. Gerardiana, Abies Smithiana, A. Browniana, Cedrus Deodara, Cupressus torulosa, Podocarpus latifolia, Juniperus squamata, J. excelsa, Quercus spicata and ten other sp., Corylus ferox, Betula utilis, B. nitida, B. alnoides, Alnus nepalensis, Salix disperma, S. cuspidata, S. japonica, Daphne cannabina, D. Gardneri, D. sericea, Elaeagnus arborea, E. conferta, E.umbellata,Hippophae salicifolia, Fraxi- nus fJoribunda, Ligustrum nepalense, L. bracteolatum, Xylosteuni ligus- trinum, Caprifolium japonicum, C. macranthum, Cornus oblonga, C. capitata, Viburnum foetidum, &c., Andromeda formosa, A. ovalifolia, &c., Rhododendron arboreum, R. barbatum, R. Falconeri, and many other sp. ; Ilex dipyrena, I. odorata, &c., Ribes Takare, Rosa microphylla, c., Rubus rugosus, R. betulinus, &c., Spiraea canescens, &c.,Neillia thyrsiflora, M. rubiflora, Mespilus affinis, &c., Prunus undulata, P. cerasoides, Rhus juglandifolium, R. fraxinifolium, &c.,Rhamnus, sp., Celastrus, sp., Euony- mus, sp., Acer acuminatum, A. oblongum, Dobinaea vulgaris, Magnolia, sp., Berberis asiatica, B. Wallichiana. Note. The western portion of the Himalayas differs considerably from 684 GEOGEAPHICAL AND GEOLOGICAL BOTANY. the eastern portion, from the predominance of Dicotyledonous forests and a damp climate in the former, with a variety of Conifers until the limit of Abies Smithiana (10,000 feet) is attained, and an extension of the tropical plants to a greater altitude ; while in the drier eastern portion the Coni- fers are diffused throughout, the forests less considerable; and the plants of temperate climates diffused lower down. Cultivated plants. The cereals and orchard fruits of Europe, mountain Rice, and a few tropical plants in the lower regions. (For the Indian flora consult Roxburgh's l Flora Indica,' Hooker and Thomson's l Flora Indica ' (a most valuable introductory treatise), Hooker's 1 Flora of British India,' and numerous memoirs by Wallicn, Wight, Griffith, and many other botanists, principally British. For the Sikkim Himalayan see especially Hooker's publications.) 9. Polynesian (or Reinwardf s) Region. Mean temperature, 66-84 Fahr. (19-29 C.). Altitude, 0-6000 feet. Character. Resembling that of the Indian region, and included by Grisebach in his Indian Monsoon region. The principal distinction con- sists in the greater number of Orchidese (especially parasitic species, which appear here in many peculiar forms), of Ferns, and species of Ficus. A slight approximation to the Australian forms : Melaleuca, Metrosideros, Proteaceae (Heliophyllum). Among the other character- istic forms are the Genera. Licuala, Lodoicea, Rafflesia, Brugmansia, Stemonurus, An- tiaris, Myristica, Nomaphila, Hydrophytum, Philagonia, Esenbeckia, Echinocarpus, Aromadendron. Predominant trees and shrubs. Primaeval forests, composed especially of species of Ficus, LauraceaB, Calameae, and Bignoniaceae, with Licuala speciosa, Broussonetia papyrifera, Artocarpus incisa, Antiaris toxicaria (Upas), Myristica, sp., Ardisia, sp., Tectona grandis, Strychnos tieute, Diospyros, sp., Barringtonia speciosa, B. excelsa, Philagonia procera, Cereus, sp., Calophyllum Inophyllum, Elaeocarpus, sp., Esenbeckia altis- sima, Echinocarpus Sigun. Cultivated plants. The same as in the Indian region, with Bread-fruit, Cassava, Inocarpus edulis, Nutmeg, Camphor, Papaw, Cotton (tree, &c. ), Paper-mulberry, Hemp. 10. Upper Javan (or Blume's) Region. Altitude, 5000-12,000 feet. Character. This region, like the preceding included in Grisebach's Indian Monsoon region, bears a certain resemblance to the Emodic region, and ought perhaps to be united with it. Extratropical forms replace the tropical. Oak-woods replace the forests of Ficus ; and these are succeeded by forests of Podocarpus mingled with Ternstrcemiaceous trees, above which the shrubby Heaths (Thibaudia) and woody Gnaphalia occur at a comparatively low elevation (9000 feet), where the trees cease. Genera. Plantago, Lysimachia, Veronica, Gentian a, Swertia, Vac- cinium, Gaultheria, Vireya, Thibaudia, Bellis, Galiurn, Saprosma. BOTANICAL REGIONS. 685 Characteristic trees and shrubs. TernstroemiaceaB (Cleyera), Gordonia, Schima, Eurya, Meliaceae, arborescent Eupatoriese, Lauraceae, Ficus, Podocarpus amara, P. imbricata, P. latifolia, P. bracteata, Agathis loran- thifolia, Quercus, 16 sp., Myrica javanica, Castanea javanica, C. argentea, &c., Dithocarpus javensis, Engelhardtia spicata, E. rigida, Thibaudia, sp., Viburnum, sp.,Sambucus javanica, Haemospermum arboreum, Mespilus, sp. (For further information on the botany of this region the publications of Blume, Miquel, Beccari, and other botanists should be consulted.) 11. Oceanic (or Chamisso's) Region. Mean temperature, 73-83 Fahr. (23-29 C.). Character. A sparing and not very peculiar flora. Greater approxi- mation to the flora of Asia than to that of Africa ; some affinity to the Australian (Casuarina, Proteaceae, Myoporum, Epacrideae, Melaleuca, Acaciae aphyllae). Genera. Schiedea, Antholoma, Aporetica, Crossostylis, Codia, Timo- nius, Kadua, Cyathostegia, Argophyllum, Melodinus, Ascarina. Predominant trees and shrubs. Dracaena terminalis, Tacca pinnatifida, Pandanus odoratissimus, Cocos nucifera, Corypha umbraculifera, Cupressus columnaris, Oasuarina equisetifolia, C. nodiflora, Ficus, sp., Artocarpus incisa, Aleurites triloba, Embothiium strobilinum, Scaevola Koenigii, Vac- cinium cereum, LobeHa arborea, &c. ; Coffea kaduana, 0. Mariniana, Kadua Cookiana, &c., Rhizophora Mangle, R. gymnorhiza, Terminalia Catalpa, Barringtonia speciosa, Melaleuca virgata, &c., Osteomeles anthyl- lidifoua, Cassia Sophora, Mimosa Mangium, Adenanthera scandens, Black- burnia pinnata, Calophyllum Inophyllum, Clusia sessilis, C. pedicellata, Sapindus Saponaria, Dodonaea spathulata, D. viscosa, Aporetica pinnata, A. ternata, Grewia Mallococca, Sterculia Balangas, S. foetida, Commersonia echinata, Tetracera Euryandra. Cultivated plants. Bread-fruit, Taro (Arum esculentum), Arum sa- gittifolium, A. microrhizon, Tacca pinnatifida, Convolvulus chrysorhizus, Yam (Dioscorea alata), Cocoa-nut, Banana, Inocarpus edulis, StercuUa Balangas, Ficus aspera, F. Granatum, Shaddock, Hog-plum (Spondias dulcis), Mimusops dissecta, Terminalia glabra, Crataeva religiosa, Eugenia malaccensis, Dracaena terminalis, Macropiper methysticum, Areca oleracea, Paper-mulberry . (Seemann's * Flora Vitiensis ' may be consulted for a complete list of the plants of Fiji, &c.) 12. Region of Balsamic trees (Arabian or ForskaVs Region). This and the following region are properly grouped in one region by Grisebach, the broad climatal and botanical features being the same from the Atlantic to the Indian Ocean, south of the Mediterranean district and north of the Central African region. It extends to Arabia, Scinde, and the Punjab. Great heat and almost rainless seasons are characteristic. The vegetation is peculiar, consisting often of spiny, bulbous, or succulent plants. Character. Tropical j in greatest part, Indian forms. GEOGRAPHICAL AND GEOLOGICAL BOTANY. Characteristic genera. Straeniia, Maerua, Semea, Oncoba, Caucanthus, Geruma, Balsamodendron, Cadia, Orygia. Some approximation to tlie South- African flora (Stapelia, Haernanthus). Predominant trees and shrubs. Pandanus odoratissimus, Ficus Svca- morus, F. salicifolia, F. populifolia, F. Forskalii, F. palmata, F. serrata, F. Sur, F. Toka, Avicennia tomentosa, Cynanchuni arboremn, Balsamoden- dron gileadense, B. Opobalsamum, B. Kataf, B. Kaful, Celastrus edulis, C. parviflora, Grewia populifolia, Maerua unifiora, M. racemosa. Cultivated plants. Millets (species of Sorghum), six-rowed Barley, Maize, Arum Oolocasia, Date-palm, Plantain, Cocoa-nut, Tamarind, Fig, Papaw, Peach, Apricot, Plum, Apple, Quince, Vine, Coffee, Sugar, Ginger, Radish, Spinach, Gourd, Dolichos, sp., Tree-cotton, Indigo. Note. This region extends to the plains of North-east India (Scinde), and should probably include part of Persia and also of the Abyssinian region. (Boissier's ' Flora Orientalis ' is a most valuable book on the flora of these regions. See also Cosson's memoirs.) 13. The Desert Eegion (Delias Region). Mean temperature, 73-86 Fahr. (23-30 C.). Character. This region, like the preceding, is subject to the unchecked prevalence of trade-winds. It varies in character according to the rocky or sandy character of the plains, the presence of oases, &c. A very p^oor flora. No characteristic Orders or genera, but the following species : Pennisetum dichotomum, Phoenix dactylifera, Cucifera thebaica, Euphor- bia rnauritanica, ^Erua tomentosa, Acacia nilotica, A. arabica, A. gummi- fera, A. Senegal, Cassia obovata, C. Singueana, Alhagi mauronim, Mimosa Habbus, Zizyphus Palma Christi, Zygophyllum simplex, Z. album, Fago- nia arabica, F. Oudneyi. Cultivation. Only in the Oases; here principally the Date-Palm. Doura (Sorghum vulgare), Wheat, Barley. South-European and certain [ndian fruits. 14, Region of Tropical Africa (Adansoris Region). Mean temperature, 73-8G Fahr. (23-30 C.). Character'. The Sudan region of Grisebach ; is remarkable for the large number of peculiar generic types, each often containing but few species. Leguminosae, Rubiaceae, Cyperaceae very prevalent. Comparatively few species of Palmaceas, Filices, Scitamineaa, Piperaceae, Passifloreae. Genera. Adansonia, Dombeya, Melhania, Christiania, Pentadesma, Napoleona, Parkia, Thonningia. Predominant trees and shrubs. Anona senegalensis, c., Cadaba fari- nosa, Crataeva Adansonii, Capparis edulis, Pentadesma butyracea, Bom- bax pentandrum, B. guineense, Adansonia digitata, Sterculia acuminata, Grewia carpinifolia, Acacia, sp., Cassia occideutalis, Pterocarpus esculen- tus, Parkia africana, Chrysobalanus Icaco, Conocarpus pubescens, Rhizo- phora, sp., Psychotria, sp., Bignonia tulipifera, Avicennia africana, Eu- phorbia (shrubby species), Ficus, sp., Elais guineensis, E. nielanococca, Rhapis vinifera, Phoenix spinosa, Pandanus candelabrum. BOTANICAL REGIONS. 687 Cultivated plants. Maize, Rice, Millets (Sorgliuin vulgare, saccharatum, Panicum, sp.), Yam (Dioscorea alata, saiiva), Cassava, Arum esculentum, Plantains, Mango, Papaw, Pine-apple, Oil-palm, Cashew-nut, Figs, Tama- rind, Citrus, sp. (Oranges, Limes, Lemons, &c.), Coffee, Sugar, Ginger, Cardamoms, Grains of Paradise, c., Beans of various kinds, and Do- lichos pulses, Ground-nut (Arachis), edible Solaua, Cotton, Tobacco, (For information respecting the flora of this district, see specially Oliver's ' Flora of Tropical Africa/ Peters's * Mossambique,' Hooker's ' Niger Flora,' various papers of Burchell, Welwitsch, and others.) Intermediate in position and in characteristics between the preceding region and the South- African or Cape Region is Grisebach's Kalahari Region, a dry stony desert, without oases. Spiny Acacias and bulbous plants manage to live, as well as Cucurbits, succulent Vines, and, most curious of all, the strange Welwitschia. 15. Region of Cacti and Piperacece (Jacquirfs Region}. Mexico, Guiana, fyc. Altitude, up to 5000 feet. Mean temperature, 68-84 Fahr, (20-29 C.). Character. Bromeliacea?, Piperaceae, Passifloraceae, Cactaceae, Euphor- biaceae, Convolvulacese, Apocynaceae, Rubiaceae. Tropical Orders less frequent here than in other places within the tropics : Filices, Scitami- neae, Orchidaceae, Myrtaceae, Leguminosae, Terebinthaceae, Aurantiaceae, Tiliaceae, Malvaceae. Extratropical Orders appearing or becoming more abundant : Labiatas, Ericaceae, Campanulaceae, Composite, Umbelliferae, Crassulaceae, Rosaceae, Caryophyllaceae, Cruciferae, Rauunculaceae. Characteristic genera. Phytelephas, Kunthia, Galactodendron, Podo- pterus, Salpianthus, Russellia, Lagascea, Gronovia, Inga, Thouinia, Lace- pedia, Theobroma, Guazuma. Predominant trees and shrubs. Cyathea spinosa, C. villosa, Meniscium arborescens, Agave americana, Yucca acaulis, Cocos nucifera, C. buty- racea, Mauritia flexuosa, Martinezia caryotifolia, Oreodoxa montana, Kunthia montana, Chamaerops morini, Coi'ypha Miraguama, C. Purnos, C. tectorum, &c., Liquidambar styraciflua, Cecropia peltata Galactoden- dron utile, Rhopala ovata, Avicennia tomentosa, Ehretia ternifoiia, Cordia dentata, Cereus, sp., Melocactus, sp., Opuntia, sp., Pereskia, sp., Mammil- laria, sp., Lecythis elliptica, &c., Bertholletia excelsa, arborescent Mela- stomae, Bauhinia splendens, B. suaveolens, &c., Haematoxylon carnpe- chianum, Caesalpinia cassioides, &c., Acacia cornigera, A. foetida, &c., Hymenaea Courbaril, &c., Inga Humboldtiana, I. insignis, &c., Mimosa, sp., Swietenia Mahogani, Bonplandia trifoliata. Cultivated plants. Maize, Doura, Cassava, Yam, Batatas, Plantain, Mango, Custard-apples, Guavas, Cocoa-nut, Papaw, Peach, Pine-apple, Cashew-nut, Tamarind, species of Citrus, Granadilla, Vine, Cactus-fig, Rose-apnle, Cocoa, Vanilla, Coffee, Sugar, Tomatos, Capsicums, Pigeon- peas (Cajanus), Ground-nut, Cochineal-cactus, Tobacco, Cotton. Grisebach very properly separates the cisaequatorial region of South America from the Mexican region. The shores of northern South America, as well as the river districts of the Orinoco and Amazon, are covered with dense forests, with few Conifers, but many Palms and climbing plants. 688 GEOGRAPHICAL AND GEOLOGICAL BOTANY. The savannahs and llanos are plains or plateaux covered with grass, with few trees, and sometimes deserts. 16. Region oftJie Mexican Highlands (Bonpland's Region). Altitude, above 5000 feet. Mean temperature, C7-79 Fahr. (20-27 C.). Character. The climate of the Mexican Highlands is very uniform. Tropical forms vanishing or decreasing : Tree-ferns, Palmaceae, Piperaceae, Euphorbiaceae, Melastoniaceae, Passifloraceae. Extratropical forms make their appearance or become more abundant : Amentacess (Salix, Quercus), Coniferse (Pinus, Cupressus), Labiatae (Salvia, Stachys, Marrubium), Pedicularis, Anchusa, Myosotis, Polemoniura, Ericaceae (Vaccinium, Ar- butus, Arctostaphylos), Compositae (greatly increasing),Valeriana, Galium, Cornus, Caprifolium, Umbelliferae, Rosaceae (Amygdalus, Mespilus, Rosa, Potentilla), Caryophylleae (Arenaria), Cruciferse (Draba), Ranun- culacese (Anemone, Ranunculus). Characteristic genera. Mirabilis, Maurandya, Leucophyllum, Holtzia, Dahlia, Zinnia, Schkuhria, Ximenesia, Lopezia, Vauquelinia, Choisya, Cheirostemon. Predominant trees and shrubs. Forests of Oaks and Conifers. Pinus occidentals, Abies hirtella, Cupressus thurifera, C. sabinoides, Taxodium distichum, Quercus (16 sp.), Salix Bonplandiana, S. paradoxa, &c., Arbu- tus mollis, A. petiolaris, Arctostaphylos polifolia, A. pungens, c., Vac- cinium geminiflorum, V. stamineum, V. confertum, Rosa Montezumae, Mespilus pubescens, Amygdalus microphylla, Cheirostemon platanoides. Cultivated plants. Maize, European cereals, Olives and fruits, and es- pecially Agave americana. Note. In the uppermost regions of the mountains the flora acquires an alpine aspect. Here occur Cyperus toluccensis, Chelone gentianoides, Cnicus nivalis, Ageratum arbutifolium, Senecio (many procumbent spe- cies), Potentilla ranunculoides, Lupinus elegans, L. montana, Arenaria bryoides. (For the geographical botany of this and adjacent districts the volume preparing by Mr. Hemsley for Messrs. Salvin and Godman's ' Natural History of Mexico and Central America ' will be most important.) 17. Region of Cinchonas (Andes, or Humloldfs Region). Altitude, 5000-9000 feet. Mean temperature, 59-68 Fahr. (15-20 C.) . Character. The tropical Andean region of Grisebach. The Pacific slope is very sudden, the coast being nearly rainless and the vegetation poor. On the eastern slope of the Cordilleras a long summer rainy season is very favourable to forest vegetation, among which the Cinchona-yield- ing trees may be specially mentioned. Extratropical forms make their appearance, or become more frequent : Graminaceas, Amentacese (Quer- cus, Salix), Labiatse (Salvia, Stachys, Scutellaria), Anchusa, Myosotis, Swertia, Ericacea3, Compositaa (very numerous), Caprifoliaceae (Viburnum, Sambucus), Umbelliferae (Ferula, Ligusticum), Rosaceae, Cruciferae, Ranunculaceae. On the other hand, certain tropical forms vanish or be- come rarer, but a few particular species of Palmas, Piperaceae, Cactaceae, PassifloreaB, and Melastomaceae ascend to a considerable altitude. BOTANICAL EEGIONS. Genera. Lileea, Cervantesia, Oreocallis, Lachnostoma, Gaylussaccia, Stevia, Flaveria, Tagetes, Espeletia, Cinchona, Guilleminia, Loasa, Ka- geneckia, Negretia, Amicia, Perottetia, Dulongea, Laplacea, Freziera, Abatia, Monnina. Predominant trees and shrubs. Oreodoxa frigida, Ceroxylon andicola, Podocarpus taxifolia, Salix Humboldtiana, Quercus Humboldtiana, Q. almaguerensis, Q. tolimensis, Ficus velutina, Rhopala cordifolia, Oreo- callis grandiflora, Persea laevigata, P. Mutisii, P. sericea, Ocotea mollis, O. sericea, Vaccinium caracasanura, Andromeda bracamorensis, Befaria Slauca, B. ledifolia, Cinchona Condaminea, C. cordifolia, C. oblongifolia, . laucifolia, &c., Weinmannia elliptica, W. Balbisiana, &c., Osteomeles glabrata, Rubus floribundus, Ilex bumelioides, I. myticoides, Clusia el- liptica. Cultivated plants. The tropical cultivated plants mentioned under 15 almost entirely disappear ; Maize and Coffee, however, are cultivated in this region ; after these come the European cereals and fruits, Potatoes, and Chenopodium Quinoa. (Humboldt's publications afford the best general view of the vegetation of this district.) 18. Region of Escallonice and Calceolaria (Ruiz and Pavon's Region). Altitude, 9000-18,000 feet. Mean temperature, 59-34 Fahr. (15-1 C.). Character. This is nearly the same as the Chilian transition region of Grisebach, intermediate between the Antarctic region to the south and the Andean region to the north ; eastward are the Pampas. The general climate is like that of the Mediterranean, but with longer periods of drought. The tropical forms have disappeared almost entirely, but the following genera still occur : Tillandsia, Oncidium, Peperomia, Rhexia, Passifiora. The forms which characterize the colder temperate and the polar zones become more common: Lichens, Musci, Carex, Luzula, Alnus, Rumex, Plantago, Gentiana, Swertia, Yaccinium, Campanula, Ca- calia, Senecio, Umbelliferee, Valeriana, Saxifraga, Ribes, Rubus, Alche- milla, Caryophyllaceae (Sagina, Arenaria, Cerastium, Stellaria), Cruciferae (Draba, Arabis). Predominant Orders. Compositse, Graminaceee, Ericaceae. No large trees. Characteristic genera. Desyeuxia, Tigridia, Gardoquia, Calceolaria, Thibaudia, Lysipoma, Barnadesia, Homanthis, Chuquiruga, Culcitium, Wernera, Dumerillia, Escallonia, Pectophytum, Klaprothia, Polylepis. Predominant shrubs. Alnus ferruginea, A. acuminata, Vaccinium acu- minatum, V. empetrifolium, V. floribundum, &c., Thibaudia rupestris, T. floribunda, T. longifolia, T. strobilifera, Befaria grandiflora, B. coarctata, Ribes frigidum, Escallonia myrtilloides, E. tortuosa, E. berberidifolia, Ilex scopularum, Drymis granatensis. (Gay's ' Flora of Chili,' and Miers and Weddell's publications on the flora of Chili, Bolivia, &c., may be consulted for further details.) 19. West-Indian (or Siuartz's) Region. Mean temperature, 59-79 Fahr. (15-26 C.). Character. Tropical heat with two rainy seasons are very favourable to the growth of plants, but the original character of the flora has been 690 GEOGRAPHICAL AND GEOLOGICAL BOTANY. much altered by cultivation. The flora of this group of islands approaches that of the adjacent continent, but is distinguished especially (like the Polynesian from the Indian flora) by the great quantity of Filices and Orchidacese. In addition to these Orders, we find among the characteristic forms the following : Genera. Thrinax, Epistylium, Alchornea, Tanaecium, Tetrantlms, Catesbaea, Belonia, Portlandia, Picramnia, Legnods, Lithophila, Valen- tinia, Hypelate. The following are deserving of mention among the predominant trees and shrubs : Cocos nucifera, Pinus occidentalis, Laurus, sp., Melastoma, sp., Myrtus, sp., Sterculia, sp., Uvaria, sp. Cultivated plants the same as in 15. (Grisebach's ' Flora of the West Indies ' is the best general guide to the flora of these islands.) 20. Region of Palms and Melastoma {Brazilian of Martins s Region). Mean temperature, 59-84 Fahr. (15-29 0.). Character. The Amazon district is perhaps best placed with the cis- eequatorial. The central Brazilian region consists of a mountain range to the east, near the coast, and in the interior high tableland. In the dry season vegetation is dormant, but extraordinarily varied and vigorous in the rainy season. Probably it is that portion of the globe in which the Vegetable Kingdom presents the greatest profusion and variety. Abundance of genera and species, magnitude of individuals, impenetrable (primaeval) forests, numerous climbing and parasitical plants. Among the characteristic, although not peculiar Orders may be named Palmacere, Haernodoraceas, Gesneraceae, Melastomaceae, and Sapindaceae ; the Vochy- siaceae are peculiar. The peculiar genera are too numerous to be men- tioned here ; among those richest in species are the Genera. Vellosia, Barbacenia, Manihot, Franciscea, Ditassa, Lycno- phora, Diplusodon, Kielmeyra, Sauvagesia, Lavradia. Characteristic genera and species, according to the different modes of occurrence. In the primaeval forests : Palms of various genera, Ficus, Cecropia, Anda, Ehopala, Myristica, Bignonia, Tlieophrasta, Stifftia, Oxyanthus, Coutarea, Psychotria, Bertiera, Feuillea, Carica, Myrtus, Gus- tavia, Lecythis, Bertholletia, Melastoma, Hymenaea, Dimorpha, Tratti- nickia, Pilocarpus, Trichilia, Cedrela, Cupania, Banisteria, Hippocratea, Caryocar, Marcgravia, Clusia, Calophyllum, Sloanea, Gothea, Lebretonia, Abroma, Carolinea, Bixa, Uvaria. In the Catingas (or open woods, where the trees lose their leaves in the dry season) : Jatropha, sp., Acacia, sp., Mimosa, sp., Caesalpinia pubescens, &c., Spondias tuberosa, Thryallis brasiliensis, Chorisia ventricosa, Bombax, sp., Eriodendron, sp., Pourretia ventricosa, Capparis lineata, &c., Anona obtusifolia, &c. In the Campos (open treeless plains): Paniceae, Amaryllis, Alstrce- meria, Vellosia, Barbacenia, Burmannia, Stelis, Cnemidostachys, lihopala, Laurus, Ocotea, Gomphrena, Lantana, Echites, Hancornia speciosa, Ges- nera, Lycnophora, Baccharis, Vernouia, Mikania, Stevia, Melastoma, Khexia, Terniinalia fagi folia, Gaudichaudia, Sauvagesia, Lavradia, Plect- anthera. BOTANICAL EEGIONS. 691 On the sea-coasts: Cocos schizophylla, Diplothemium maritimum, Eriocaulon, sp., Xyris, sp., Avicennia tomentosa, Rhizophora Mangle, Conocarpus erectus, racemosa, Bucida Buceras. Cultivated plants, about as in 15. (The most detailed works on the flora of this region are the splendid works of Von Martins, continued by Eichler and other botanists.) 21. Region of shrubby Composites (Extratropical S.- American, or St.-HilairJs Region}. Mean temperature, 59-74 Fahr. (15-23 0.). Character. The tropical forma decrease or vanish ; extratropical, espe- cially European, forms take their place. Ranunculaceae, Cruciferae, Heli- anthemum, Caryophyllacese, Lathyrus, Galiurn, Teucrium, Plantago, Carex; a few South- African forms, Polygala, Oxalis, Gnaphalium. This region has more than half its genera in common with Europe. Numerous Compositae ; many among these shrubby. Genera. Larrea, Hortia, Diposis, Boopis, Acicarpha, Cortesia, Petunia, Jaborosa, Tricycla, Caperonia, Bipennula. The vegetation of the Pampas here takes its character from the long periods of drought, no rainy seasons occurring, and only occasional thunder-storms. Arborescent vegetation is scanty or entirely absent. Spiny shrubs and salt plants are found in the interior. Onopordon Acanthium has in some districts overrun the whole country, displacing the few native plants. Cultivated plants. Mostly the European : Wheat, Vine. The Peach is very widely spread. 22. The Antarctic Region (D'Urvilles Region). Mean temperature, 41-48 Fahr. (5-9 C.). diameter. Climate of northern portion mild, equable, damp. Great resemblance to the North-European flora (Region 2). The tropical forms have entirely vanished. Forests prevail in tne south ; Fagus antarctica and an evergreen species are abundant. In the extreme south Saxifrages, Ranunculi, &c. prevail. Predominant Orders. Composite, Graminaceae, Caricese, Musci, Li- chenes. The following are also common; Ranunculaceae, Cruciferae, Caryophyllaceee, Rosaceae, Umbelliferse. Two thirds of the genera in common with Europe. A slight approximation to South Africa (Gla- diolus, Witsena, Galaxia, Crassula) and to Australia (Embothrium, Ourisia, Stylidiae, Mniarum). Characteristic genera. Gaimardia, Astelia, Callixene, Philesia, Dra- petes, Bsea, Calceolaria, Pernettya, Oligosporus, Nassavia, Bolax, Azorella, Donatia, Acaena, Hamadryas. Predominant trees and shrubs. Fagus antarctica, Salix magellanica, Embothrium coccineum, Pernettya empetrifolia, P. mucronata, Andro- meda myrsinites, Baccharis tridentata, Chiliotrichum amelloides, Ribes raagellanicum, Escallonia serrata, Fuchsia coccinea, Myrtus numnaularia, Berberis ilicifolia, B. inermis, B. microphylla, B. enipetrifolia, Drimys Winteii. No cultivation. (Hooker's ' Flora Antarctica ' is the best flora of this region.) 692 GEOGEAPHICAL AND GEOLOGICAL BOTANY. 23. Region of Stapeliee and Mesembryanthema (S.-African or Thunberg's Region). Mean temperature, 54-73 Fahr. (12-23C.). Character. A succession of mountain ranges and intervening plateaux separate the coast region from the elevated plains in the interior. The coast region has a flora very rich in forms, flowers abundant and beautiful, but the trees or shrubs not luxuriant ; no large dense forests, or abund- ance of climbing plants, &c. ; many succulent plants. Characteristic Orders. Restiaceae, Iridaceae, Proteaceae, Ericaceae, Fi- coidere, Bruniaceae, Diosmeae, Geraniaceas, Oxalideae, Polygalaceae. Genera. Restio, Ixia, Gladiolus, Morsea, Watsonia, Haemanthus, Stru- maria, Agapanthus, Eucomis, Massonia, Strelitzia, Passerina, Gnidia, Protea, Leucadendron, Leucosperrnum, Serruraria (and many other Pro- teaceae), Stilbe, Selago, Stapelia, Erica, Gnaphalium, Helichrysum, Stobaea, Pteronia, Osteospermum, Tarchonanthus, Relhania, Gorteria, Arctotis, Othonna, Stoebe, CEdera, Anthospermum, Mesembryanthemum, Vahlia, Liparia, Borbonia, Lebeckia, Raffuia, Aspalathus, Stavia, Brimia, Phylica, Diosma, Pelargonium, Oxalis, Sparmannia, Muraltia, Polygala, Penaea. Predominant forms. On the sandy districts of the coasts : Stapelia, Iridaceae, Mesembryanthemum, Restio, Diosma. On the mountains : Proteaceae, Erica, Crassula, &c. On the dry plateaux : Acacia capensis, A. Giraffae, A. detinens, A. viridiramis, Euphorbia mauritanica, E. tenax, Poa spinosa, Mesembryanthemum, sp., Aloe, Iridaceae, Erica, Diosmeae, Restio. Other remarkable species. Haemanthus coccineus, Amaryllis toxicaria, Testudinaria montana, T. elephantipes, Podocarpus elongatus, Salix gariepina, Protea mellifera, P. grandiflora, Leucadendron argenteuro, Laurus bullata, Lycium tetandrum, Olea similis, Rhizogum trichotomum, Tarchonanthus camphoratus, Stcebe rhinocerotis, Crassula coccinea, Portulacaria afra, Mesembryanthemum edule, M. turbiniforme, Metro- sideros angustifolia, Acacia elephantina, Zizyphus bubalina, Calodendron capense. Cultivated plants. The European cereals, fruits, and esculent vege- tables ; also Sorghum caffrorum, Batatas, Plantains, Tamarind, Guava, Shaddock. The Kalahari region of Grisebach, which intervenes between this region and the Sudan, is alluded to at p. 687. (The works of Harvey and Sonder afford the best general insight into the nature of this flora.) 24. Region of the Eucalypti and Epacrides {Australian, or R. Brmvn's Region.') Mean temperature, 53-73 Fahr. (12-23 C.). Character. The Australian flora, as a whole, is tropical in the north, where it approximates to the Indian monsoon and Oceanic types, in the centre is a dry desert region, while south the climate is like that of the Mediterranean. The vegetation necessarily presents great differences according to the variations in climate. In Tasmania the rainfall is more evenly distributed throughout the year. The Australian is one of the richest and most peculiar floras, but without any considerable profusi on INSULAB FLORAS. 693 of vegetation. The plants of Swan River present much in common, so far as generic types are concerned, with those of the Cape. The characteristic Orders and genera are : Xerotes, Xanthorrhcea, Pterostylis, Casuarinae, Leptoineria, Pimelea, Proteaceas (Banksia, Hakea, Persoonia, Grevillea, Petrophila, Isopogon, Dryandra), Myoporineae,West- ringia, Logania, Mitrasacme, Epacridaceae (Epacris, Leucopogon, Sty- phelia), Stackhousieae, Scaevoleae, Goodenovieae, Stylidiae, Eucalyptus, Melaleuca, Leptospermum, Acacia3 aphyllae, Platylobium, Bossiaea, Dios- meas (Boronia, Zieria), Pittosporeae, Tremandreae, Pleurandra, Hibbertia. Predominant trees and shrubs. Three fourths of the forests are com- posed of species of Eucalyptus, the number of which amount to more than a hundred ; some are very lofty. Next to these come Proteaceae, Epa- crideae, Diosmeae, Casuarinae, and Acaciae aphyllae, forming woods and " bush." Also Coniferae, Araucaria excelsa, A. Bidwilli, A. Cunningharnii, A. Cookii, Dacrydium Franklmii, Podocarpus spinulosa. Cultivated plants. In the European colonies the cereals, fruits, and vegetables of Europe. (For further information consult the works of Robert Brown, Baron von Miiller, and specially Bentham's ' Flora Austra- liensis.') 25. New-Zealand Region (Foster's Region). Temperate climate. Character. The flora is more nearly related to that of South Chili than to that of Australia. Evergreen forests, lofty Conifers, and Tree Ferns, Cordylines, &c. abound. Tropical forms vanish, or appear but sparingly. Half the genera European. Approximation to Australia (Pimelea, Myoporuni, Epacris, Styphelia, Cassinia, Melaleuca) ; to South Africa (Gnaphalium, Xeranthemum, Tetragonia, Mesenibryauthemum, Oxalis, Restio) ; to the Antarctic region (Mniarum, Fuchsia, Acsena, Drimys). Many Ferns. Genera. Phormium, Pennantia, Knightia, Forstera, Griselinia, Meli- cope, Uicera, Plagianthus, Melicytus. Characteristic species. Cyathea medullaris, Gleichenia furcata, Dra- caena indivisa, D. australis, Phormium tenax, Areca sapida, Dacrydium taxifolium, Dammara austrahs, Podocarpus Totarra, Knightia excelsa, Avicennia resinifera, Andromeda rupestris, Epacris juniperina, Wein- mannia racemosa, Tetragonia expansa, Fuchsia excorticata, Melaleuca, sp., Dicera dentata, &c. Cultivated plants. Arum esculentum, Convolvulus chrysorhizus, Phor- mium tenax, &c. In the European colonies the cereals, fruits, and escu- lents of Central Europe. (Hooker's Flora and Handbook to the Flora of New Zealand constitute the best general works on the Flora of New Zealand.) Insular Floras. The flora of islands remote from any continent is of peculiar interest where it has not been interfered with by cultivation or other destructive agency. The questions to be solved are : How did the plants now existing on these islands get there ? Were they created in situ, or were they imported ? If so, How, when, 694 GEOGRAPHICAL A1S T D GEOLOGICAL BOTANY. and whence? Speaking generally, insular floras comprise some species which are absolutely peculiar or endemic ; some which are so closely allied to continental forms, that it may readily be conceived that they came from a common stock at a compara- tively recent period ; and, thirdly, species identical with those of ome continent, and that not necessarily the nearest to them, often indeed, not so ; hence the probability that these islets received their vegetation from these distant continents at a geological epoch very remote from the present. Unfortunately cultivation, the destruction of forests, the ravages of goats, rats, and other destructive animals, have in most cases materially altered the character of the flora. The aboriginal flora of St. Helena, for instance, is all but entirely destroyed, and its place supplied by introduced vegetation, or by species in no way peculiar to the island. When near a continent, and divided from it by a shallow sea, the floras of island and con- tinent are, in a broad sense, identical, as those of England and Northern Germany ; but where, as in the case of Madagascar, an island is large and separated by a deep channel several hundreds of miles wide, the flora is different. Some islands are of volcanic origin, like Madeira, the Azores, and the Canaries ; and the anti- quity of their flora can be studied with reference to their geological history. The Atlantic Islands. The general character of the flora is distinct, with an intermixture of Mediterranean elements, and of species from the African mainland. Lyell considers that these islands had never any connexion with the mainland, but that they originated as volcanoes in Miocene times, and were peopled by waifs and strays from Europe and Northern Africa in that period. The presence of such North- American types as Persea and Clethra is explained by the fact that in Miocene times, when the Atlantic volcanoes first reared their crest above the waves, Europe was covered with a very rich vegeta- tion, containing many genera now peculiar to America (Hooker), so that the genera in question in Madeira may he looked on as "survivals " from the Miocene period. Monizia edults, a native of one of the Desertas, belongs to a genus which has no representative elsewhere in the world. This, too, like Companula Vidalii, which only exists on one rock off the coast of Flores, may be regarded as a " survival." Hooker (Lecture on Insular Floras, < Gardeners' Chronicle,' 1867) considers that Volcanic Islands received their flora by means of immigrants from various con- tinents, and does not favour the view that these distant islets ever formed parts of existing continents. The same>author points out, in general terms, that islands, owing to the similarity of physical circumstances, are peopled with similar plants, and that their vegetation is consequently similar, as in the abundance of Mosses and Ferns and of evergreen trees. Animals, on the other hand, are rare. Species are few in proportion to genera, genera to Orders, hence the remarkable difference in the flora. The mountains, moreover, have relatively few alpine plants. INSTILAR FLORAS. 695 The Cape- Verde Islands have a flora which is quite of the Saharan type. St. Helena had a large number of trees of peculiar character show- ing an African type. The Mascarene Islands. Madagascar, Mauritius, Bourbon, and the Seychelles are tropical islands of volcanic or metamorphic origin. Half the species, according to Baker (whose ' Flora of Mauritius ' is'the most recent enumeration), are peculiar to one or other island, or common to the whole Archipelago, while 6 per cent, are African, 8 Asiatic, 14 common to Asia and Africa, and 21 per cent, common to the Old and New Worlds. The most abundantly repre- sented Orders are Ferns, Orchids, Grasses, Sedges, Rubiaceae, Euphor- biacefe, Coinpositae, and Leguminosse. The total proportion of species to a genus is 2-3, and of species to an order between 9 and 10. No less than 2G9 species, according to Mr. Baker, have been introduced, and have established themselves in Mauritius, while the native flora has been to a large extent exterminated by cultivation, &c. Pacific Islands, fyc. The floras of the Indian Archipelago, of the Sandwich and Fiji Islands, are closely related to the Indo-Malay type of vegetation, as already men- tioned, and form a transition between it and that of Northern Australia. New Caledonia and Lord Howes Island belong to the Australian type as regards their flora, with some peculiar forms. The flora of Norfolk Island, broadly speaking, is allied to the New-Zealand flora, with admixture of Australian and Indo-Malayan types. The Auckland and Campbell Islands have the general features of New- Zealand vegetation. Chrysobactron Rossii, a noble yellow-flowered Aspho- del^ is one of the characteristic plants. Antarctic Islands. Under this head brief mention may be made of Juan Fernandez, the flora of which is mainly South Chilian, with marked preponderance of Composites and many peculiar types. Kerguelen's Island has a flora allied to that of Fuegia. The Kerguelen Cabbage, Prim/lea antiscorbutica, is characteristic, and, according to Bennett, differs from most European Crucifers in being wind-fertilized, an interesting fact to be correlated with the large proportionate numbers of wingless insects. The flora of Marion Island is of similar character. The Falkland Islands are of similar general character to Kerguelen's Land, and are remarkable for baing covered with dense tufts of Tussac grass, Dactylis ccespitosa, and with hummocks or cushion-shaped masses of an Umbellil'er, Bolax ylebaria. Cockburn's Island, lat. 64 12' S. lat., due south of Cape Horn, yields little or no vegetation beyond Mosses and Lichens of cosmopolitan diffusion. South-Atlantic Islands. The floras of St. Helena and Ascension have been already alluded to. It remains to make brief reference to the floras of Amsterdam Island, 696 GEOGEAPHICAL AND GEOLOGICAL BOTANY. St. Paul's, and Tristan d'Acunha. Very little is known of the vegetation of these islets ; but a species of Phylica is supposed to form the forest of the first-mentioned island, and to connect botanically the islands of St. Helena, Tristan d'Acunha, and Amsterdam one with another and with the African continent, species of Phylica being found in each, and most abundantly in South Africa. Spartina arundinacea, a grass, is common to the islands of Amsterdam, St. Paul's, and Tristan d'Acunha. Chenopo- dium tomentosum, Ncrtera df presto, Dactylis ccespitosa, and Accena indi- cate a connexion with the Fuegian and Antarctic floras, and through a species of Pelargonium with the South-African. Sect. 4. STATISTICS OF VEGETATION. Number of Species. Various authors have made computations from existing data, with a view to ascertain the total number of existing species of Phanerogams; but as the opinions of authors as to what limits a species are so extremely varied, it seems useless to occupy space with such speculative matter. The computations range from 100,000 to 300,000 species and upwards. It is some- what more easy to lay down some general statistical facts regard- ing the distribution, and particularly in reference to the relative proportions of the more important Classes and Orders, in different regions of the globe. Relative Proportion of the larger Groups. Materials are insufficient to enable us to calculate the relative distribution of Cryptogams and Pha- nerogams in different regions. The former appear to bear a higher pro- portion to the latter as we recede from the equator to the poles ; but this may depend upon our better acquaintance with the Cryptogamic Floras of the northern temperate regions than with the Cryptogams of the warmer climates. As regards the relative abundance of Monocotyledons and Dicotyledons in different latitudes, it is generally agreed that the proportion of Mono- cotyledons to Dicotyledons increases from the equator towards the poles a retrogression of the proportional number taking place, however, in the icy regions of the poles and on the alpine summits. Asa rule also, closely connected with the above statements, Monocotyledons are more pre- dominant in proportion to the greater moisture of a climate. Probably no Orders, except the Leguminosae and the Compositae, con- tain a number of species amounting to 5 per cent, of the total number of Phanerogamic species. Thus the existence of species of one Order in any region exceeding in number 5 per cent, of all species found there, indicates a predominance of that Order. If such predominance occur only in one region, the Order becomes characteristic of that region ; if such predomi- nance of the same Order occur in many regions, it indicates wide diffusion of that Order. In a very long list of Floras, from all parts of the globe, compared by Ajph. De Candolle, it was found that only 35 Orders of Phanerogamia formed more than 5 per cent, in any one or several regions. STATISTICS OF VEGETATION. 697 The orders which presented in one or but a few floras from 10 to 19 per cent, of the Phanerogamic species were : Caryophyllaceae . . Spitzbergen (14f per cent). Cruciferae Spitzbergen (19) and Melville Island (13f). Leguminosae .... Almost all intertropical and subtropical regions. Kubiaceae Sierra Leone (10). Proteaceae Australia (11|). Melastomaceae . . West coast of tropical America (11 J), Brazil (?). Saxifragaceae .... Spitzbergen (1 1|), Melville Island (15). Solanaceae Ascension (13) (naturalized). Myrtacese Brazil (?). Cyperaceae Lapland (13), Iceland (11), Brocken (12). Orchidaceee New Guinea (16^), Java (10), Mauiitius (11|), S. Mexico (10). Of Orders ordinarily exceeding 10 per cent, of a flora, Grarninaceae constituted 18 per cent, in Spitzbergen ; 21 in Melville Island ; 27 in Kerguelen's Land. Composite, 18| per cent in California and Mexico ; 19 in the Malouines ; 21 in Chili j 22 at Quito ; 25 in the S. of Buenos Ayres ; 27 in Juan Fernandez. Orders with more than 30 per cent, occurred in exceptional localities, viz. Compositse (33|) in the elevated parts of Chili, and Cyperaceae (33^) at Tristan d'Acunha. Certain Orders predominate in particular latitudes, without being in their nature characteristic of those latitudes. Tropical Floras. Thus, while in some regions of the tropical zone the Palms, Zingiberaceae, Marantaceae, Melastomaceae, Malpighiaceae, &c., are really characteristic, the predominant species of the tropical floras are not members of such Orders as Lauraceae, Menispermaceae, Anonaceas, Bom- bacese, which have their maximum in hot climates, but belong to the Leguminosae, Graminaceae, and Cornpositae, which exceed 10 per cent, generally in the tropics : the Orchidaceae and Cyperaceae follow next, then Euphorbiaceae, Urticaceae, Melastoniaceae, and Scrophulariaceae; of which, Melastomaceae alone belong exclusively to hot regions. Other Orders occurring in many tropical floras, but forming less than 5 per cent, of the species, are : Convolvulaceae, Malvaceae, Piperaceae, Zingiberacese, and Marantaceae, Solanaceae, and less commonly Acanthaceae, Amentacese, Apocynaceae, Bignoniaceae, Boraginaceae, Capparidaceae, Cucurbitaceae, Gentianaceee, Labiatae, Lauraceae, Lorauthaceae, Malpighiaceae, Myrtaceee, Uinbelliferae, Palrnaceae, Passifloraceae, Kosaceae, liutaceae, Anacardiaceae, and Ver- benaceae. The Ferns are likewise exceedingly predominant in species in the islands of the tropics (16, 21, 26 per cent.). Temperate Floras. In northern temperate latitudes (from the tropic to 60 N. lat.), again, Compositae, Graminaceae, C^yperaceae, and Legumi- noseae predominate in species the Cyperaceas increasing northward, the Leguminosae rapidly decreasing (Granada 8 per cent., Yorkshire 4^ per cent.). Next follow Cruciferas, Umbelliferae, and Caryophyllaceae ; then Labiataa, Rosaceee, and Scrophulariaceae. No other Orders exceed 5 per cent, of the species, and only attain this in exceptional localities. 698 GEOGRAPHICAL AND GEOLOGICAL BOTANY. In the northern zone beyond 60 N. lat., the species predominating northwards are Graminacese, Cruciferae, Saxifragaceae, Caryophyllacese, Ranunculaceae, Rosaceae, Cyperaceae (5-7 per cent.). Composite form 7 per cent, in Melville Island, but only 4-5 per cent, in Spitzbergeu. Ainentiferae (Betulaceae, Salicaceae, &c.) and Juncaceae barely reach 5 per cent. ; Polygonaceae, Ericaceae, and Scrophulariaceae approach this number, but are mostly below it. In the south temperate zone we find two classes of regions, one dry, the other with a damp climate. The former comprehends the Cape of Good Hope, Australia, Chili, and La Plata. Cornpositse predominate at the Cape and in America, but in Australia fall to 7 per cent. Leguminosae, on the contrary, make but 7 to 12 per cent, in America and at the Cape, "but 14 per cent, in Australia. The Grasses are not more than 3 to 6 per cent, anywhere, and the Cyperaceae still fewer. The Cape and Australia have, however, certain especially abundant Orders ; thus Proteaceae form 2 to 6 per cent, at the Cape, 8-12 per cent, in Australia ; Myrtaceae 9 per cent, and Epacridaceae 4-5 per cent, in Australia; Iridaceae 4-6 per cent, Liliaceas 4-5 per cent., and Ericaceae 2-6 per cent, at the Cape ; Stylidiaceae and Goodeniaceae are especially Australian. ^ In the moist regions, comprising parts of the African coast, Tasmania, New Zealand, Island of Chiloe, &c., the Grasses and Compositae increase iu departing from the tropics ; Cyperaceae rise to 4-8 per cent, j Orchidaceae, 4|-8| per cent. ; and Ferns are very numerous in the islands. Restiaceae increase in Tasmania, but Proteaceae, Leguminoseae, with Stylidiacese, Goodeniaceae, &c. decrease. The proportions in the Southern extremity of America approach those of the temperate and moist regions of the northern hemisphere. As a general statement, it may be said that of the three most fre- quently predominating Orders, Leguminosae are diminished in propor- tion to temperature, the Compositae are lessened by combined cold and humidity, and the Graminaceae are least predominant where the climate is dry. It must be borne in mind that the above calculations are approximate only, and apply to species, or genera, or orders, and by no means repre- sent the distribution of individual plants. CHAPTER III. BOTANICAL GEOLOGY. Sect. 1. NATUEE AND IMPORTANCE or FOSSIL PLANTS. Remains and traces of plants are met with in most of the strati- fied rocks which have been produced by successive geological changes of the earth's surface. These remains afford an indica- tion, more or less perfect in different cases, of the nature of the NATUEE OF FOSSIL PLANTS. 699 vegetation which has existed in earlier periods of the world's his- tory. Vegetable remains found imbedded in geological formations are called fossil plants ; and the condition in which these fossils occur are exceedingly varied, both as to the nature of the substance preserving the vegetable forms, and the degree of perfection of the forms preserved. The principal kinds of fossils may be classed as follows : 1. Petrified plants, in which the structures of plants have been more or less completely impregnated with mineral matter, hardening them into a stony mass. They present various modifications, in which more or less of the organic matter remains, completely impregnated with mineral substances, or where the mineralization is so complete that the organic substance has totally disappeared. The mineral substance of such fossils is different in different cases. Silicified remains are the most common ; fossils im- pregnated with carbonate or sulphate of lime abound in other strata, while fossils of dense or earthy ironstone, argillaceous ironstone, and, lastly, iron-pyrites are frequent in particular rocks ; impregnations with rock-salt, oxide of copper, alumina, &c. are rarer. 2. Coal, where the vegetable substance is more or less completely con- verted into a solid, black, combustible carbonaceous substance, of stone- like aspect. This occurs in almost every possible modification, in masses or in the form of isolated plants or organs of plants, from the solid stony anthracite to the brown coal or lignite, which preserves the organic texture and is recognizable at first sight as vegetable matter. Coal-beds are formed through the accumulation of vast masses of vegetation, and their conversion through pressure and chemical changes into solid masses ; but leaves, steins, or parts of stems, such as layers of bark, fruits, &c., con- verted into coal, are found isolated in strata of various composition. With these last are intimately connected the numerous fossils which are true petrifactions, but have the organic matter preserved in the mineral substance in the condition of coal, giving a coal-like aspect to the fossil. 3. Impressions or natural casts of plants or organs of plants, which have been formed by the vegetable objects being incrusted by, or imbedded in, mineral substance and decaying subsequently to the solidification of the enclosing substance ; the cavity left by the decayed vegetable may be filled up by the same or a different mineral substance ; and casts of the internal parts of stems &c. are met with, from the penetration of the mineral matter into cavities formed by the quicker decay of succulent structures, such as pith. 4. Objects contained in Amber, the fossil resin of a Pine, which has accidentally enclosed various vegetable and animal bodies which it flowed over while" liquid. The objects are sometimes thoroughly impregnated with amber, like microscopic objects enclosed in Canada balsam, these having been enclosed in a dead or dry condition ; in other cases, where fresh organs have been enclosed, hollow casts only are found, the enclosed matter having been more or less decomposed. The study of vegetable fossils is far less satisfactory than that of animal remains, since, in the great majority of cases, the structures most dis- tinctive of the subordinate groups of plants are formed of very perishable matter. Genera, and even species, of animals may be recognized by bones 700 GEOGRAPHICAL AND GEOLOGICAL BOTANY. and shells, which are of a very persistent nature, and are found abundantly in stratified rocks. The preservation of fossils can only have occurre'd through the agency of water, impregnated with mineralizing matter, or loaded with mud which enclosed the remains : the vegetable bodies which can resist the long-continued action of water are few ; and these mostly afford only characters of large sections of the vegetable kingdom, without furnishing generic, far less specific distinctions. Added to the fragmentary character of the fossils known, those kinds hitherto found possibly only represent partially prevailing forms of vegetation. Attempts, however, have been made, by combining the conclusions of stratigraphical geology and animal paleontology with those of vegetable palaeontology, to form conceptions of the character of the vegetation of succeeding geological periods. The ideas obtained in this way, however, are very superficial and exceedingly speculative. Still there is much that is promising in the investigations ; and the general tendency of all the facts hitherto collected is to indicate that there has been a gradually increasing complexity of organization in the plants successively created, that the plants of the earliest epochs belong to the lower Classes, and that the higher Phanerogams appeared only in the later formations in the last of these probably in smaller proportion than in existing vegetation. In the earliest formations (Cambrian, Silurian, &c.) the few vegetable remains are those of Algae, Fucoids, &c. In the Devonian and Carboni- ferous periods vascular Cryptogams, Ferns, Lycopods, Equiseta prevailed. In the Triassic and Oolitic periods Gymnosperrnous plants formed a marked feature, such as Conifers, Cycads, &c., with Tree-ferns and traces of Monocotyledonous plants. With the Cretaceous period appear Angio- spermous plants, beginning with a preponderance of Incomplete, and passing through Dialypetalse to the more recent formations, where Gamopetalous plants prevail. But in all cases, though there is evidence of progress, there is an overlapping of the characteristics of one period by those of another. One important point, however, must not be overlooked in inquiries relating to this subject ; that is, the probability of the coexistence of diversified local floras, as at the present day, the remains of which might, from purely systematic considerations, be regarded as of different antiquity. In illustration of this, it may be observed that the remains found in the European formations belonging to the epoch immediately preceding the present offer a general resemblance to the prevailing forms of existing jNorth-American vegetation. Sect. 2. FOSSIL PLANTS CHARACTERIZING PARTICULAR GEOLOGICAL FORMATIONS. 1. Flora of the Palceozoic Strata. Lower and Middle Palaeozoic, or Transition Period. Comparatively few plants are known in these strata, and a considerable amount of un- certainty exists in reference to the determination of the fossils. What remnants remain in the Cambrian, Silurian, and Lower Devonian series are apparently those of marine Alga3. In the more recent deposits of this age Ferns, including some allied to Hymenopliyllum and Trichomanes, FOSSIL FLOEAS. 701 Calamites, Asterophyllites, and Conifers are found. Psilophytum extends in America through Upper Silurian and Devonian formations. It is a plant probably Cryptogamous, but not referable to any existing form, but presenting resemblances to Khizocarpeae and Lycopodiaceae. Cyclostigma is more distinctly Lycopodiaceous, as also Lycopodites. Conifers are represented by Prototaxites, described as presenting indications of Coni- ferous structure in a simpler condition than now existing. In the Upper Silurian traces of Lycopods occur. Upper Palaeozoic, or Carboniferous System. The known floras of tins system, remarkable for the presence of the great Coal-beds of Europe, afford a very large number of species, in which there is a continued great predominance of the Leafy Cryptogamia (Ferns, Lycopods, Equiseta, &c.), in many respects of higher organization than those now existing. The principal characteristics revealed here are the absence of Dicotyle- dons, the paucity of Monocotyledons, the predominance of the Ferns and allied Classes, and of certain plants of organization not met with in ex- isting vegetation, referred by some authors to the Class of GymuosDerms, by others, and probably more correctly, to the vicinity of Lycopodiaceae, &c. Conifers and Cycads begin to appear, with Stigmarias, Sigillarias, Lepidodendron, c. The general character of this flora is very monoto- nous, and alike in character from the poles to the equator. About 150 species of Ferns have been found in the British Coal- formation. Lepidodendron has the habit and spores of Lycopodium. Lepidostrobus is the fruit-spike of Lepidodendron, having the structure of existing Lycopodium. Calamites seem to have been gigantic Equiseta. Asterophyllitvs, Annularia, Sphenophyllum are possibly forms of Calamites. Stigmaria is the root of Siyillaria, a plant of doubtful affinity, referred by Carruthers to Lycopodiacese, by others to Gymnoeperms. The Conifers are represented by Dadoxylon, allied to Araucaria, Sterribergia, Trigono- carpum, &c. Sternbergia is supposed to have been the pith of Dadoxylon. Antholites has much the general appearance of an Orobanche. Permian System. The fossils of the Magnesian Limestone afford only fragmentary representatives of the Carboniferous flora, most of the cha- racteristic genera having disappeared. The Orders are much the same, but less numerously represented by species. Silicified Coniferous wood, Walchia, Ferns, Calamites, Lepido'dendron, and Algae are found, and also evidence of the existence of Palms. Nwggerathia has the venation of Salisburia. 2. Flora of the Mesozoic, or Secondary Strata. Triassic, or New Red System. In the " Variegated Sandstone " strata of this formation, comparatively few species have yet been observed. The Carboniferous species have disappeared; Ferns still predominate and exhibit peculiar forms; Conifers (Voltzia, Haidingerd) are abundant; Cycadeae rare, and a few doubtful Monocotyledons (Yuctites, Palceoxyris) occur. In the "Keuper" Sandstones, with a general analogy in the proportion of Orders, except that Coniferae are rare and Cycadacese abun- dant, the genera of Ferns and allied Orders are mostly distinct from those of the Vosgesian, or " Variegated '' Sandstones. Liassic System. The essential characters of this epoch are the great 702 GEOGRAPHICAL AND GEOLOGICAL BOTANY. predominance of Cycadeae (Zamites), which here appear in several new genera, and the existence of Ferns with more highly organized foliage than that of the genera of older formations. Algae, Fungi, Lichens, Ly- copods, and Conifers also existed at this period, but no Angiospermous Dicotyledons have yet been discovered. Oolitic System. The nature of the strata referable here is very diverse ; the general character of the fossil vegetation consists in abundance of Ferns proper, Equiseta, arid of Cycadeas, especially of those genera (Zamites and Otozamites) approaching nearest to existing forms, and the greater frequency of the Coniferse, Brachyphyllum and Thuytes, than in the Lias. Cones of Araucarias have been found, as well as endogenous plants allied to Pandanus and Arum. Algae, Marsileas, Lycopods are also found. There are a large number of known species. The dirt-beds of Portland are layers of soil with remains of Cycadaceous trees in an erect position. Some of these are distorted by pressure into the shape of birds' nests. Wealden System. This formation, remarkable as a freshwater product, has afforded comparatively few species of plants, mostly congeneric, al- though specifically distinct from those of the Lias ; but the proportion of the Cycadaceae to the Ferns is smaller. Equisetum and Char a (the latter by its* fruits) are represented. Dicotyledons have not been discovered. Cretaceous System. In this formation we are at once struck with the diminution of Ferns, Equisetaceae, and allied forms, the reduction of the species of Gymnosperms, and the appearance of Angiospermous Phanero- gamia, chiefly dicotyledonous (Betula, Myrica, Salix, &c.), though traces of Palms and Grasses have been met with. The Cycadaceae are still numerous ; but they and the Coniferae do not more than equal the Dico- tyledons. The genus Crednaria, supposed to belong to the last class, is very characteristic of the Chalk formation. The Ferns and Equisetaceae almost disappear. The fossil plants of the Upper Cretaceous system, the equivalent of the Upper Chalk of this country, show a terrestrial flora in which all the great subdivisions of the vegetable kingdom are represented. Dr. Debey estimates the number of species at Aix at about 200, of which 67 are Cryptogams. Gleichenia, Lye/odium, and Asplenium among Ferns have been identified as generically identical with the plants now so named. Among Conifers, Cycadopieris closely resembles Sequoia ; Araucarias also are found, but few Cycads. Pandanads existed, and, among Dicotyledons, Figs, Oaks, Walnuts, Myrtles, and numerous Proteads, the structure of the leaves of the latter being so perfectly preserved that even the stomata may be seen. Attempts have been made even to correlate the genera with existing types of Proteads ; but this is a very hazardous procedure, seeing how variable the leaves of Proteaceae are. Still the general indications point to a vegetation like that of Australia. 3. Floras of the Tertiary System. The floras of this system form a more or less connected whole, which is continued in the later strata into existing vegetation. They are especially distinguished from those of older epochs by FOSSIL FLORAS. 703 the abundance of Angiosperinous Phanerogams, Dicotyledons, and Monocotyledons above all, Palmaceas. But a sort of transition takes place from the Cretaceous period to the Eocene. In this system, however, the proportion of Gymnosperms rapidly de- creases, and the Cycadaceas disappear from Europe, while the Conifers approach the character of the existing genera of temperate regions. Eocene Flora. The distinctive characteristics, as compared with other epochs, are the presence, though rare, of Palraaceee, Nipadites, the com- parative abundance of Algae and marine Monocotyledons (Caulinites, Zosterites, .fee.), and the existence in Europe of numerous now exotic forms, such as Gleichenia among Ferns, especially represented by the fossil fruits of the Isle of Sheppey, the Barton Bed in the Isle of Wight, &c. Though less rich than the Miocene, these formations include a large number of species of an Australian or Indian type, such as Lauracete, Aralia, Anona, Ficus, various Proteacese, Petrophila, Isrtpogon. Temperate species, such as are found in the Miocene, are wanting. Miocene Flora. A very rich flora. No less than 900 species have been detected in one locality in Switzerland by Heer. The Australo-Indian forms give place to plants of an American type, resembling the existing vegetation of the United States, Mexico, and Japan. One of the most striking features is the abundance of Palmaceae, Sabal, together with Gamopetalous Dicotyledons, espe- cially a supposed Rubiaceous genus, Steinhawria. The list of fossils contains also a Bambusa, Lauracese, Combretaceae, Legurninosae, Apocynaceae, Vitis, belonging to warm climates, with many Amen- taceous trees, Populus mutabilis, Carpinus, Aceraceae, Proteaceae, Nymphaeacese, and other plants now belonging to temperate regions. Numerous vegetable remains occur in beds of this forma- tion at Bovey Tracey, Devonshire, and in the Isle of Wight. At Bovey Tracey one bed is described as a perfect mat of the debris of a Sequoia intermediate between the existing Red-wood, 8. semper- virens, and 8. gigantea ( Wellingtons) of California. At QEningen, on the Rhine, are beds of this formation containing numerous insects and plants, the latter being of special interest in this case, because the leaves are so often associated with fruits, rendering the identification so much more trustworthy. Numerous Maples with foliage and samaras have been found. Planes also are found with leaves and fruit, and with the bark peeling off, as in existing species. The flora of the Miocene period, as a whole, is of a subtropical and temperate character, and presents many American forms, such as Liqui- dambar, Sequoia, &c. In the Arctic regions, Greenland, &c., Miocene beds occur, very rich in vegetable remains, many of which are pronounced identical with those of the Miocene beds of Central Europe. In these now inhospitable regions once grew at least ten species of Conifers, in- 704 GEOGKAPHICAL AND GEOLOGICAL BOTANY. eluding ^Sequoias, Taxodium distichum, Abies excelsa, Common Spruce, Salisburias, Oaks, Planes, Poplars, Elms, Birch, Maples, Walnuts, Magno- lias, Andromeda, Viburnum, Zamia, Vines, Ivies, Ferns, and many others, more or less correctly referred to existing generic types, but, in any case, affording evidence of a subtropical or warm temperate climate. It is conceivable, then, that the plants of the Miocene epoch, so many of which are of American types, started from Greenland and were dispersed throughout Europe, Asia, and America. linger and Heer supposed that the plants might have migrated from America to Europe by way of a now sunken continent, the Atlantis of Plato, the position of which is marked by the accumulations of Sargasso Weed. The presence of American genera, Clethra &c. in Madeira, has already been alluded to with re- ference to this view. Asa Gray and Oliver, however, consider that the existing evidence is more favourable to a migration from America through Asia to Europe ! Pleiocene Flora. The Dicotyledons predominate, and are most varied, as in existing vegetation; the Monocotyledons are rare; and the Pal- macese of the preceding epochs are wanting. The general analogy of the flora is with those of the temperate and warmer regions of Europe, North America, and Japan at the present day. According to the determinations made by palaeontologists, many existing genera are represented, such as Glyptostrobus, Taxodium, Salisburia, Cyperacese, Comptonia, Thymelacese, Santalaceae, LauraceEe, Liqnidambar, Nyssa, Robinia, Gleditschia, Bauhinia, Oassia, Acacia, Rhus, Juglans, Ceanothus, Cclastrm, Sapindus, Lirioden- dron, Cappari*, Sideroxylon, Achras, Symphcos, Cornacere, Myrtaceae, Pomaceae, Tiliaceas, Magnoliaceae, &c. This list includes especially modern North-American genera, which existed at that time in Europe. Quercus, Ace?', &c. appeared then as now. Pleistocene Deposits. The glacial drift and the diluvial deposits be- longing to this group afford hardly any recognizable vegetable remains, beyond fragments of fossil wood of Coniferae, met with occasionally in connexion with the bones of extinct Mammalia and in a few Lignite beds. The flora of the Glacial period still exists in Alpine districts. 4. Floras of Early Formations of the present Geological Period. The formations referable to this group consist chiefly of freshwater calcareous deposits (tufa), the older peat-bogs, and forests now buried or submerged beneath the sea. The remains existing in calcareous tufa have not yet been well inves- tigated, partly because the beds are not greatly developed in most countries, and partly because they usually contain only casts of vege- table structure, produced through incrustation. As far as we know, the plants are similar to those of the existing floras of the regions, with a lew exceptions. The old peat-bogs, especially of Northern Europe, often contain vast quantities of recognizable vegetable remains, belonging to species no longer growing in the same spots, but found further south, as remains of Corylus, Pinus picea, &c. in the Shetland Islands, of Oaks, Maples, Limes, Ash, &c. in Sweden, beyond the present limits of those plants. FOSSIL FLOE AS. 705 Remains of forests formed of still existing species occur in many parts of Europe, enclosed in diluvial beds. The city of Breslau stands on the site of an ancient forest, whence the trunks of Quercus pedunculata are dug out ; the same is the case with the city of Bamberg, where the trunks of trees of great diameter have been found in excavations for railways, &c. Similar trunks of Oak are occasionally dug out of the diluvial beds in England, as in the upper part of the valley of the Med- way. Submarine forests are known to exist off many points of the British coast and the west coast of France ; wood obtained from a large sub- merged bed ofl' the coast of Pembrokeshire is found to consist of Oak and Alder, and of Pinus sylvestris : the Oak, Elm, Hazel, Walnut, &c. are found in the British Channel. In the Lake-dwellings of Switzerland seeds of Cereals, Apples, Nuts, &c., and Linseed have been found, indi- cating not only the existence of these plants, but also, as in the case of Cereals, of cultivation. These facts, together with the analogous but more complete evi- dence derived from animal remains, show a gradual transition from the Tertiary to the present geological epoch. As to the wider question of the descent of existing species from their fossil representatives, or from preexisting forms now extinct, such filiation can hardly be doubted in many cases, although the exact line of descent is often not traceable. On the other hand, many of the earlier types of vegetation were of their kind more highly organized than their existing representatives ; hence it is a question whether the latter are really degenerate descendants from their progenitors, or whether the more highly endowed Lycopods and Equiseta, for instance, have not died out and become extinct. Thallophytes seem to have existed in all ages much as we see them now. Vascular Cryptogams and Conifers early came into exist- ence, and were, as we have seen, highly organized. Traces of Angiospermous Dicotyledons are not visible till a much more recent, but still inconceivably remote period ; while from the time of the Eocene and Miocene periods > there is a gradual increase in the number of forms, such as are now found in various parts of the globe. It is clear, then, on the whole, that there has been a succession of vegetable types, and a gradual progression in morphological complexity, but that such succession has been interrupted and not continuous in any one locality, that many links have been utterly lost, and many forms become extinct, so that the attempts made to create a " phylogeny " or genealogical history of the Vegetable Kingdom on so imperfect a basis as is now available must be accepted with great reserve. 2z 707 INDEX TO SYSTEMATIC BOTANY, CONTAINING THE BOTANICAL NAMES OF CLASSES, ORDERS, AND GENERA, AND THE VERNA- CULAR NAMES OF SPECIES REFERRED TO IN PART II. OF THIS WORK. Abele, 346. Abies, Tournef. 358. ABIETINE^E, 358. Abronia, Jacq. 223. Abrus, L. 253. Absinthe, 292. Acacia, Willd. 254. Aealypka, L. 338. ACANTHACEJE, 322. Acanthera, 316. Acanthodiurn, Del. 322. Acanthus, L. 322. Acer, L. 231. ACERACE^, 231. Achillea, Neck. 292. Acliiinenes, P. Br. 324. ACHLAMYDE^E, 329. Achlya, Nees, 452. Achras, 302. Achyranthes, L. 330. Aconitum, Tournef. 196. Acorus, L. 396. ACRAMPHIBRYA, 186. ACROBRYA, 186. Acrocbisma, Hook.fil. 432. ACROGENS, 187. Acrostichum, L. 419. Actea, L. 196. Actiiiocarpus, R. Br. 389. Adansonia, L. 221. Adenanthera, L. 251. Adhatoda, Nees, 322. Adiantum, L. 419. Adonis, DC. 196. Adoxa, L. 282. ^Echmea, R. 8f P. 381. ^Ecidium, Gmel. 4(50. ^EGICERACE^;, 301. ^Egiceras, L. 301. ^Egiphila, 321. yEgle, Corr. 235. ./Eschynanthus, 7ac&, 324. ^Esculus, Z. 230. -^Ethalium, 471. ^Ethusa, L. 280. African Hemp, 386. African Teak, 340. AGARICINI, 463. Agaricus, i. 462. Agathopnyllum, Juss. 333. Agathotes, Don. 308. Agave, L. 378. Agrostis, L. 404. Ailanthus, J)es/. 242. Aizoon, L. 269. Ajuga, Z. 320. ALANGIACE^:, 263. Alangium, L. 263. Alaria, Grev. 451. Alchemilla, Tournef. 257. ^Ife, 345. Aldrovanda, Monti, 215. Aletris, i. 380. Aleurites, Forst. 339. Alexanders, 282. Alfonsia, JTww^, 392. , 414, 435. Algaroba, 254. Alhagi, 253. Alisma, Juss. 389. ALISMACE^E, 388. Alkanet, 318. Allamanda, Z. 308. Allium, L. 385. Allosorus, Bernh. 419. Allspice, 260. Almond, 258. Alnus, Z. 345. Aloe, Tournef. 385. ' Aloes-wood, 254, 336". Aloexylum, 254. Alona, ZzW/. 317. Alopecurus, Z. 404. Aloysia, 321. Alpiuia, Z. 375. Alsine, Wahlenb. 219. ALSINE^E, 219. Alsodeia, Thouars, 216. Alsophila, J2. ^r. 419. Alstonia, Z. 309. Alstrcemeria, Z. 378. ALSTRCEMERIEJE, 378. Altha,Z. 221. ALTINGIEJE, 278. Alum-root, 238. Alyssum, Z. 211. Alyxia, 309. AMARANTACEJE, 330. Amarantus, Z. 330. Amarauchaete, 471. AMARYLLEJE, 378. AMARYLLIDACEJE, 378. 2z2 708 INDEX TO SYSTEMATIC BOTANY. Amaryllids, 378. Amaryllis, L. 378. Ambrosinia, L. 398. American Aloe, 379. Ammannia, Houst. 265. Ammi, Tournef. 282. Ammoniacum, 282. Amomum, L. 375. Amorpli oph allus, Blume, 397. Ampelopsis, Rich. 244. AMPHIBBYA, 186. AMYGDALE^, 257. Amygdalus, 258. AMYBIDACEJE, see Bur- seraceae. Amyris, L. 248. ANACABDIACEJE, 246. Anacharis, Sab. 382. Anagallis, Tournef . 300. Anagyris, L. 253. Anamirta, Coleb. 201. Ananassa, Lindl. 381. Anandria, Siegesb. 293. Anchusa, i. 318. Ancistrocladus, Wall. 225. Andira, 253. Andrea, Elir. 432. ANDB^ACEJE, 431. Andrographis, Wall. 322. Andromeda, i. 296. Andropogon, L. 403. Androsace, Tourn. 301. Anemone, Haller, 196. ANEMOKE2E, 196. Anethum, Z. 282. Angelica, Hoffm. 280. Angelica, 282. An'giopteris,-H r o^ > m.420, ANGIOSPEBMIA, 193. Angostura bark, 241. Angrsecum, Thouars, 374. Anime, 254. ^Lwwc, 282. Annatto, 214. Anomochloa, 405. Anona, i. 200. ANONACE^, 200. Anthemis, DC. 292. Anthericuni, L. 385. Aristolocliia, Tournef. Anthistiria, L. 406. 355. Anthocercis,Z&z7/. 316. AKISTOLOCHIACEJE, ANTHOCEBOTE^E, 435. 355. Anthoxanthum, L. 404. Armeria, Wittd. 299. Anthriscus, L. 279. Anthurium, Schott. 397. Antiaris, ZcscA. 343. Antidesma, L. 343. Antirrhinum, i. 326. Apeiba, L. 224. APETAL^E, 328. Aphanomyces, 456. Aphelexis, Dor. 294. Aphyllanthes, 385. API ACE M, 278. Apium, Hoffm, 282. Aplectrum, Nutt. 374. APLOSPOBE^:, 448. APOCYNACE^, 308. Apocynum, Tournef. 309. Aponogeton, Thunb. 389. APOSTASIACE^E, 374. Apple, 258. Apricot, 258. AQUIFOLIACEJE, 303. Aqnilaria, iaw. 336. AQUILABIACE^:. 336. Armoracia, 212. Arnica. L. 292. ABOIDEJE, 395. Aroniodendron, 199. Arracacha, 282. Arrow-root, 376. Arrow-root, Portland 397. Arrudea, ^.-JT?7. 227. Artanthe, Miq. 348. Artemisia, i. 292. Artichoke, 293. ABTOCABPACEyE, 342. Artocarpus, L. 342. Arum, Z. 396. Arundo, L. 405. Asafcetida, 282. Asagraea, iw?<77. 387. Asarum, Tournef. 355. ASOLEPIADACE^E, 309. Asclepias, L. 310. Ascobolus, Pers. 465. Ash, 305. Asparagus, Z. 385. Asparagus, 386. Aquilegia, Tournef. 196. Aspergillus, 3ftbA. 467 A 1 T C\1 T A T ' j T,y C\r\ *~ Arabis, Z. 211. ABACE^J, 396. Arachis, L. 253. Aralia, L. 282. ABALIACEJE, 282. Araucaria, Juss. 358. Arbor-vitce, 361. Aspidistra, Ker, 385. Aspidium, Swartz, 419. Aspidosperma. M. & Z. 309. Asplenium, L. 419. Assam Tea, 227. Astelia, Banks, 399. lu Voyaqeur, 378. Aster, JV r ees, 291. Arbutus, Tournef. 296. Asteranthos, Desf. 261. Archangelica, Hoffm. Astilbe, Ham. 266. 282. Astragalus, Z. 250, 253. ABCHISPEBMS, 357. Astrantia,7W?'e/ > . 279. Arctium, Lam. 293. Astrocarpus, Neck. 214. Arctostaphylos, Adam. Astrocaryum, Mey. 394. 297. ' Astroloma, R. Br. 298. Areca, L. 391. Ataccia, R. Br. 309. Arenaria, L. 219. Atelanthera, jHooA;. f. Argania, Sch. 302. 212. Argemone, Tournef. 207. Argyrophyllum, 287. ATHEBOSPEEMACEJE, 334. Atriplex, L. 331. INDEX TO SYSTEMATIC BOTANY. 709 Atropa, L. 316. ATROPACE^:, 315. Attalea, H. B. K. 391. Attar of Roses, 258. Aubergine, 317. Aucklandia, 293. Aucuba, Thunb. 283. AURANTIACE.E. 235, 241. Auricula, 301. Australian Tea, 241. Australian Currants, 287. Autumn Crocus, 387. Ava, 348. A vena, L. 404. Averrhoa, L. 237. Avicennia, L. 321. Avocado Pear, 333. Azalea, Z. 297. Bacillus, 472. Bacteria, 471. Beeckia, L. 259. Bael fruit, 236. Bajree, 406. Balanophora, jFbrstf. 353. BALANOPHORACE.JE, 353. Ballota, L. 320. Balm, 321. Mm o/ Gtffead, 248. Balm of Mecca, 248. Balsam of Copaiba, 254. Balsam-of-Gilead Fir, 360. Z/sam o/ Perw, 254. Balsam of Tolu, 254. BALSAMINACE^E, 238. Balsamodendron, Barbadoes Cherry, 233. Barbadoes Gooseberry, 277. Barclaya, TFa//. 204. fe', 287. , Winter's, 199. Barleria, Z. 322. ^r%, 405. Barosma, Wittd. 241. BARRINGTONIACE.E, 261. Bartonia, Sims. 275. Bartramia, Hedw. 432. Bar-wood, 254. Basella, Z. 332. BASELLACE^E, 332. BASIDIOMYCETES, 461. Basil, 321. Bamboo, 405. Bambusa, L. 404. Banana, 377. Banisteria, Z. 233. Banksia, L.fil. 336. Baobab, 222. Baphia, 254. Baptisia, 253. Barbacenia, Vandelli, 380. Bassia, Jw. 302. Bast, 224. Batarrhea, 464. Batis, P. Br. 341. Bauhinia, Plum. 254. Bay-tree, 333. Bdellium, 248. Bean-capers, 240. .&?Sm. 338. ' Cofiea, L. 287. COFPE^E, 287. Cofee, 287. Coir, 394. Coix, i. 403. Cola, Schott. 223. Colchicum, Tournef. 385. Colchicum, 385. Coleochgete, J5re6. 452. Collema, ^IcA. 469. Colletia, Comm. 246. CoUomia, JVt<. 311. Collophora, 309. Colocasia, Ray, 396. Colocynth, '274. Coltsfoot, 293. Columbine, 198. COLUMELLIACEJE, 324. Colutea, 252. COMBBETACE^;, 262. COMBBETEJE, 262. Combretum, Laffl. 2G2. Commelyna, Z)i//. 387. COMMELYNACE^E, 387. COMPOSITE, 289. Comptonia, Banks, 345. Conanthera, R. $P. 385. ^:, 451. ^E, 451. , 358. Conium, L. 279, 281. CONJUGATE, 453. CONNABACE^:, 247. Conoearpus, 262. ConvaUaria, De-sf. 365. CONVOLVULACE^:, 312. Conyolvulus, L. 312. Cookia, Sonner. 235. Copaiba, 254. Copaifera, L. 251. Copal, 254. Copal, Indian, 225. Copernicia, Mart. 394. Coprosma, Forst. 287. Coptis, tfaftsJ. 198. Coquilla-nut, 394. Corallina, Tournef. 447. COBALLINEJE, 447. Corallines, 448. COBALLOBHIZA, 374. Corchorus, Z. 224. Cordia, P/wm. 317. COBDIACE^E, 317. COBDYLINE, 386. Corema, Don, 341. Coriander, 282. Coriandrum, L. 280. Coriaria, 242. COBABIEJE, 242. Cork-Oak, 351. COBMOPHYTA, 408. COBNACEJE, 283. Cornus, Tournef. 283. COBOLLIFLOBJE, 284. Coronilla, i. 253. Correa, Smith, 241. Corsican Moss, 448. COBTICIUM, 462. INDEX TO SYSTEMATIC BOTAXY. 713 Corrdalis, DC. 208. Corylus, L. 350. COBYMBIFEBJE, 292. Cosniarium. Menegh. 454. Costus, L. 375. Costus, 293. Cotton-grot*, 402. Cotton-plants, 222. Cotyledon, DC. 267. Couch-grass, 406. Coutarea, 287. Cowhage, 253. Cow-plant, 311. Cowrie Pswe, 360. Cowslip, 301. Cow-tree, 309, 343. Crambe, Tournef. 211. Cranberry, 297. Crane's-bills, 237. Crassula, If aw. 267. CBASSULACEJE, 267. CBASSULEJE, 267. Cratcegus, X. 258. Cratseva, i. 215. Crawfurdia, TFa#. 308. Creasote-plant, 240. CREMOSPEBME^E, 273. Crescentia, -. 323. CBESCENTIACE^E, 322. CVm, 212. CRIBBABIA, 471. Crithmum, Tournef. 282. Crocus, Tournef. 381. Cross-lowers, 209, CBOTALABIA, 252. Croton, i. 338. Croton-oil, 339. Croivberry, 341. Crown Imperial, 386. CBOZOPHOBA, 340. CBUCIFEB^E, 209. CBYPTOCABYA, 333. CBYPTOGAMIA, 408. Cryptomeria, -Dow, 358. CBYPTONEMIE^E, 447. Cubeba, Miq. 347. Cubebs, 348. Cucumber, 274. Cucumis, i. 273. Cucurbita, Z. 273. CUCUBBITACE^, 271. Cudbear, 470. Cuminum, L. 282. Cummin, 282. Cunninghamia, R. ^?-. 359. Cunonia, L. 266. CUNONIE^E, 266. Cupania, L. 230. Cuphea, /acy. 265. CUPBESSINEJE, 358. Cupressus, Tournef. 358. CUPUJLIFER^E, 350. Curagoa, 236. Curculigo, Gcertn. 379. Curcuma, i. 376. Currant (grape), 244. Currants, Til, 287. Cuscuta, Tournef. 312. CUSPABIEVE, 241. Custard-apple, 200. Cyathea, 5i^, 419. CYATHEEJE, 419. CYCADACEJE, 364. Cycas, L. 365. Cyclamen. Tournef. 301. CYCLANTHEJE, 395. Cyclanthus, Po^. 395. Cyclocodon, 295. Cycnoches, Lindl. 373. Cydonia, Tournef. 258. Cynanchum, L. 310. CYNABE^:, 292. Cynodon, Rich. 406. Cynomorium, Michel. 353. Cynosurus, i. 406. CYPEBACE^E, 400. Cyperus, L. 400. CYPHIE^;, 295. Cypress, 361. Cypress (deciduous\ 361. Cypripedium, L. 371. CYBILLACE^, 304. Cyrtandra, Forst. 324. CYBTANDBE^E, 324. Cystopteris, Bernh. 419. CYSTOPUS, 457. Cystoseira, Agh. 449. CYTINACE^E, 354. Cytinus, L. 354. Cytisus, 253. Dacrydium, Sol 361. Dacrymyces, 462. Daffodil, 379. Dahk-trees, 253. DaAfo'a, 293. Ztewy, 293. Dalbergia, Z. 253. Dammar Pine, 360. Dammar Pitch, 225. Dammara, Humph. 359. Damson, 258. Danaea, /". Sm. 420. Dandelion, 293. Daphne, Z. 335. DAPHNIPHYLLACE.ZE, 340. Darlingtonia, Torr. 205. Darnel, 406. Date, 394. Date-plum, 303. Datisca, X. 275. DATISCACEJE, 275. Datura, L. 314. Daucus, L. 280. Deciduous Cypress, 361. Dehaasia, 333. Delabechea, 223. Delesseria, Lamx. 447. DELESSEBIE^E, 447. Delima, L. 198. Delphinium. Tournef. 196. Dendromecon, 206. Deodar, 360. Dermatia, Haw. 465. Dermatocarpon, Eschw. 469. Desfontainea, -R. & P. 306. Desmarestia, Lamx. 450. DESMIDIE^, 454. Desmidium, Agh. 454. Desmodium, 252. DESVAUXIACEJE, 399. Detarium, 251. Deutzia, Thunb. 266. 714 INDEX TO SYSTEMATIC BOTANY. Dhoona pitch, 225. Dialium, 254. Diamorpha, Nutt. 267. DIAMORPHE.E, 267. Dianthus, L. 219. DlAPENSIACE^E, 311. Diatoma, DC. 454. DlATOMACEJE, 454. DlATOME^E, 454. Dicentra, Borkh. 208. Dichama, Fries, 468. DlCOTYLEDONES, 193. Dicranum, Hedw. 432. Dictamnus, L. 241. DICTYOGENS, 187. Dictyopteris, Lamx. 449. Dictyosiphon, Grev. 450. Dictyostelium, 471. Dictyota, Lamx. 448. DICTYOTACE^E, 448. Didymium, 470. Dieffenbachia. Schott. 396. Dielytra, 208. Diervilla, Tournef. 285. Digitalis, L, 326. Dilkea, Mast. 270. Dill, 282. Dillenia, Z. 198. DlLLENIACEJE, 198. Dion, Lindl. 365. Dionaea, Ellis, 215. Dioscorea, L. 369. DIOSCOREACEJE, 369. Diosma, L. 241. Diospyros, L. 302. Diphaca, Lour. 251,255. Dipladenia, DC. 309. Diplophractum, Desf. DIPLOZYGIJE, 280. DIPSACE^, 288. Dipsacus, Tournef. 288. DlPTEBACE^E, 225. Dipterocarpus, Gcertn. 225. Dipteryx, Reinw. 251 7 25S Dischidia, JR. Br. 311. DlSCOMYCETES, 465. Dittany of Crete, 321. . Dim-dim, 254. Docks, 330. Dodders, 313. DODONE^E, 230. Day-banes, 308. Dog's-tooth, 386. Dog-violet, 217. Dogivood, 284. Dolichos, Z. 253. Dombeya, (7av. 223. Dorema, Dow, 282. Doronicum, Z. 292. Doryphora, -Ewf//. 334. Dorstenia, Plum. 340. D0z^ Valerian, 311. Green-heart, 333. Green Laver, 453. Grevillea, JR. -Sr. 336. Grewia, Jwss. 224. Griffithsia, -4^A. 447. Grimmia, Ehrh. 432. Grislea, i. 265. Gronovia, Z. 275. GROSSULACE^E, 277. Ground- Ivy, 328. Ground-nut, 253. Guaiacum, 240. Guaiacum, P/wm. 240. Guarana bread, 230. Guarea, Z. 237. Guava, 260. Guelder Rose, 285. Guepinia, 462. Guettarda,. F^. 287. Guimauve, 222. Gulancha, 201. Gulf-weed, 450. Acacia, 254. Anime, 225. Arabic, 254. Dammar, 361. Dragon, 253. Zac, 253, 339. Gummi gutta, 229. 6rwm Senegal, 254. Gum-trees, 260. Guunera, Z. 282. Gustavia, Z. 260. Gtofita Percha, 302. GUTTIFER^;, 227. Gymnema, 311. Gymnoascus, 466. Gymnocarpea, jR. 5r. 270. GYMNOGENS, 187. Gymnogramme. Z>^sv. 419. GYMNOSPERMIA, 356. Gynandropsis, DC. 216.^ Gynerium, ZT. -B. ^". 406. Gypsophila, 220. Gyrinopsis. Gcertn. 336. GYROCARPE^E, 262. Gyrocarpus, Jacq. 262. GYROSTEMONE^, 332. Hsemanthus, 379. H8ematox} T lon, Z. 254. IL^MOD GRACE JE, 379. Hsemodorum, Sm. 380. Hair-bells, 295. Hakea, ^c^rarf. 336. Halesia, Z7fe, 304. Halidrys, Lyngb. 449. HALORAGACEJE, 264. Haloragis, Forst. 264. HAMAMELE^E, 278. HAMAMELIDACEJE, 277. Hamanielis, Z. 278. Hancornia, Gom. 309. Hand-plant, 224. HAPLOZYGI^E, 279. INDEX TO SYSTEMATIC BOTANY. 717 Haricots, 252. Hawthorn, 258. Hazel, 351. Hearts-ease, 217. Heath, 297. Hedeoma, Pers. 320. Hedera, Z. 282. Hedwigia, Hook. 248. Hedvchium, Kcenig, 375. Hedyosmum, Sclnvartz, 347. Hedyotis, Zarw. 294. Hedysarese, 252. Heliamphora, Benth. 205. Helianthemum, TOMT- nef. 214. Helianthus, Z. 293. Helichrysum, 294. Heliconia, L. 377. Helicteres, L. 223. Heliotrope, 318. Hellebore, Wliite, 387. HELLEBORES, 196. Helleborus, Adans. 196. Helmintliocliorton, 448. Helosis, Rich. 353. Helvella, Z. 405. Helwingia, Willd. 282. Hemerocallis, 385. Hemidesmus, R. Br. 311. Hemistemma, Commers. 198. Hemlock, 281. Hemlock Dropwort, 281. Hemlock Spruce, 360. Hemp, 342. Zfcm;?, African, 386. Hemp, Indian, 342. Hemp, Manilla, 378. Henbane, 315. Hennah, 264. HEPATICJE, 433. Heracleum, Z. 280. Heritiera, ^1#. 223. Hermannia, i. 223. HERMAXXIEJE, 223. Hernandia, Plum. 335. Heteria, ^w^/. 388. HETEROSCIADEJB, 279. HETEROSPORIA, 424. Heuchera, 267. Hevea, 339. Hibbertia, Andr. 198. HIBISCES, 221. Hibiscus, L. 221. Hickory, 350. Hierochloe, 406. Hillebrandia, 274. Himanthalia, Lyngb. 449. HlPPOCASTANEJE, 230. HlPPOCRATEACE^J, 245. Hippomane, L. 338. Hippophae, L. 336. Hippuris, L. 264. Hiraea, Jacq. 233. Hog-gum, 247. Hog-plum, 247. Hollboellia, JFa#. 202. JTo%, 303. Hollyhock, 222. JTo/m Oa^, 351. HOMALIACE^I, 275. Homalium, Jacq. 275. Honckenya, Ehr. 225. Honey-locust, 254. Honeysuckle, 285. Hordeum, i. 404. Horehound, 321. Hornbeam, 351. Horse-chestnut, 230. Horse-radish, 212. Horse-sugar, 304. Horse-tails, 417. Horsfieldia, 280. Hottentots fig, 270. Hottonia, Z. 300. Houseleek, 268. Hovenia, TVmw^. 246. Hoya, 72. #r. 310. HTHHIRIACE^:, 304. Humulus, i. 342. Hundred-years' Plant, 379. .Hwow JVwe, 360. Hura, X. 338. Hyacinth, 385. Hyacinthus, Z. 384. Hyalostemma, J-Fa//. 334. Hydnocarpus, G&i'tn. 270. Hydnora, 354. Hydnum, Z. 462. Hydrangea, L. 267. Hydrastis, Z. 198. Hvdrocera. Blum. 238. HYDROCHARIDACE^E, 382. Hydrocharis, Z. 382. Hydrocotyle, Tournef. 278, 279. Hvdrodictyon, J2o^7i, 452. Hydrolea, Thouars,3ll. Hydropeltis,^zcA. 204. HYDROPHYLLACES, 311. Hvdrostachys, Pet.-Th. 349. Hymensea, Z. 254. Hymenogaster, 464. HYMEXOMYCETES, 462. HYMENOPHYLLE^E, 419. Hymenophyllum, Sm. 419. Hyoscyamus, Tournef. 314. Hypecoum, Tournef. 207, 208. HYPERICACEJE, 228. Hypericum, Z. 228. Hj-phsene, 394. Hypnum, Z. 432. Hypodermii, 459. HYPOXIDACEJE, 379. Hypoxis, Z. 379. Hyssopua, Z. 320. Iberis, Z. 210. ICACIXACE^E, 304. 718 INDEX TO SYSTEMATIC BOTANY. Iceland Moss, 470. Icica, Aubl. 248. Ignatia, 307. Ilex, L. 303. ILICACEJE, 303. ILLECEBRACEJE, 268. Illecebrum, Gcertn.f. 268. Illicium, L. 199. Illigera, Bl. 262. Immortelles, 293. Impatiens, L. 238. INCOMPLETE, 328. Indian Copal, 225. Indian Corn, 406. Indian Cress, 239. Indian Figs, 276. Indian Shot, 377. Indigo, 253. Indigoi'era, Z. 252. Inga, Willd. 251. Inocarpus, 336. Inula, Gcertn. 292. lodes, Blume, 343. lonidium, 217. jfy>adw, 234. Ipecacuan, 287. Ipecacuan, black, 287. Ipecacuan, white, 287. Ipomcea, i. 312. IRIDACEJE, 380. Iridsea, 448. Iris, L. 381. JraA Moss, 448. Isatis, i. 212. ISOETEJE, 425. Lsoetes, L. 425. Isolepis, R. fir. 400. Isonandra, Wight, 302. ISOSPORIA, 416. Isotoma, 294. Ispaghula seeds, 298. Isthmia, Agh. 434. Itaka-wood, 253. jfron/, Vegetabk, 394. Ji#, 283. Jw/, Ground, 321. Iwarancusa, 406. Ixia, i. 381. Ixora, Z. 288. Jacaranda, JMSS. 322. Jacob's Ladder, 311. .Ta/op, 212. Jambosa, Humph. 269. Jasione, i. 295. JASMIN ACE^E, 305. Jasminum, L, 305. Jateorrliiza, Miers, 201. Jatropha, JKA. 338. Jeffersonia, Bart. 202. Jerusalem Artichokes, 293. Jb&'s T^ars, 406. Jubsea, 394. JUGLANDACEE, 349. Juglans, i. 350. Jujube, 246. JUNCACE./E, 398. JUNCAGINEE, 389. Juncus, DC. 399. Jungermannia, Dill. 433. JUNGEBMANNIACEE, 433. Junker, 360. Juniperus, i. 358. Justicia, L. 322. J?^, 224. Kadsura, Juss. 202. Kalmia, 297. Kamala, 339. Kangaroo-grass, 406. Za, 245. Kava, 348. J^Zp, 450. Kermes Oak, 351. Kielmeyera, Jtfar^. 226. Kingia, It. Br. 399. Kino, 253. Kino, Botany Bay, 260. Kobresia, TFiW. 401. Koelreuteria, Lam. 230. Kousso, 258. Krameria, ZCP^. 232. Kumquat, 235. LABIATE, 319. LABIAT^EFLOII^E, 291. Laburnum, 253. Lace-bark, 336. Lachnanthes, Elliott, 380. Lacis, J>m^. 349. LACISTEMACE^E, 340. Lactuca, X. 293. Ladanum, 214. Lagenaria, /&r. 274. Lagerstroemia, L. 265. Lagetta, 7wss. 335. Lamb's Lettuce, 288. Laminaria, Lamx. 449. Lamimn, Z. 320. Lamprocaulos, Mast. 400. Lance-wood, 200. Landolphia, Pafe. 309. Langsat, 234. Lansium, Humph. 234. Lantana, i. 321. Lapageria, 72. $ Pay. 383. Larch, 360. Lardizabala, ^?-4 Cherry-, 258. ZawW, " O*6fl," 283. Laurel, Portugal, 258. Laurel^ Spurge-, 335. Laurelia, 334. Laurencia, Lamx. 447. LAURENCIEJE, 447. Laurustinus, 285. Lauras, Tournef. 333. Lavandula, Z. 320. INDEX TO SYSTEMATIC BOTANY. 719 Lavender, 321. Laver, 448. Lawsonia, L. 265. Leathesia, Gray, 450. Lecanora, Achar. 470. Lechea, 214. Lecidea, Ach. 469. LECYTHIDACE^E, 260. Lecythis, Loeffl. 260. Ledum, L. 297. Leek, 386. Legnotidese, 262. LEGUMINOSJE, 248. Lemna, L. 397. LEMNACEJE, 397. Lemon, 235. Lemon-grass, 406. Lemon-plant, 235. LENTIBULABIACE^S, 328. Lentils, 253. Leontodon, i. 293. Leopoldinia, J/r. 394. Lepidium, jR. Br. 212. Lepidostacliys, JFa//. 340. Leptonychia, 223. LEFTOSPEBMEJEj 259. Lepturus, .#. 2?r. 404. Lepyrodia, J2. Br. 400. Leschenaultia, -R. -Br. 294. Lettuce, 293. Leucojum, i. 379. Lewisia, Pursh. 269. LICHENES, 413, 468. Lignum colubrinum, 307. Lignum Rhodium, 248. Lujnum-vitce, 240. LlGULIFLOKJE, 291. Ligustrum, Tournef. 305. iifoc, 305. LILIACE^E, 384. Ztfoc*, 385. Lilium, L. 384. i% of the Fields, 379. Lily of the Valley, 8SQ, Lime, 235. ime or Linden, 224. LlMNANTHACE^, 239. Linmanthemuni, 308. Limnanthes, JR. Br. 239. Limnocliaris, H. fy B, 889. LlNACEJE, 236. Linaria, Tournef. 326. Linseed, 236. Linum, i. 236. Liquidanibar, i. 278. Liquorice, 253. Liriodendron, j&. 199. Lissanthe, .R. Br. 298. ZzYc/w, 231. Lithospermum, L. 318. Litmus, 470. Littorella, i. 298. Liver-worfo, 434. Loasa, Adans. 275. LOASACE^E, 275. Lobelia, i. 294. LOBELIACE^E, 294. Locust-trees, 253. Lodoicea, Ldbill. 391. Logania, JZ. i?y. 306. LOGANIACE2E, 306. Log-wood, 254. Lolium, L. 404. Lonyan, 231. Zow^ Pepper, 348. Lonicera, Z)^s/*. 285. Lophiola, 385. LopMra, Banks, 225. LOEANTl^XCE^E, 352. Loranthus, L. 352. Lotus, i. 250. Lotus, ancient, 204, 233, 246. Loudonia, Lindl. 264. Love-lies-bleeding, 331. Lucern, 252. Luffa, Tournef. 274. Luhea, TT/W. 224. Lupines, 253. Lupinus, i. 250. Luzula, DC. 399. Lychnothamnus, 444. Lychnis, L. 219. Lycium, 203. Lycoperdon, Tournef. 449. Lycogala, Micheli, 471. Lycopersicum, 317. LYCOPODIACEJE, 423. Lycopodium, i. 423. Lygeum, 407. Lygodium, Swartz, 420. Lysimachia, Mcench. 300. LYTHKACEJE, 264. Lythrum, i. 265. Macadamia, P. Jf. 337. Jtfaw, 334. Machaerium, 253. Madura, 343. Macropiper, Miq. 347. Macrozamia, Miq. 365. Madagascar Poison-nut, 309. jtfiwfcfer, 287. Madia, 293. Mserua, 213. Magnolia, Z. 199. MAGNOLIACE^:, 199. MAGNOLIEJE, 199. Maguey-plants, 379. Mahogany, 234. Mahonia, JVw. 203. MALESHEBBIACEJE, 271. Mallotus, Lour. 339. Jtfa^ow, 222. Malope, L. 222. Malpighia, Plum. 233. MALPJLGIIIACEJE, 233. Malva, L. 221. MALVACEAE, 220. Malvaviscua, 222. MALVEJE, 221. Mamillaria, Haw. 276. Mammee apple, 228. Manchineel, 339. Manchineel, bastard, 309. Mandrag-ora, Town. 314. Mandioc, 340. Mandrake, 316. Mangifera, i. 247. Mango, 247. 720 INDEX TO SYSTEMATIC BOTANY. Mangold-wurzel, 331. Mangosleen, 228. Mangrove, White, 321. Mangrove, 262. Manilla Hemp, 378. Manna, 218, 253, 305. Manna of Mount Sinai, 218. - Maples, 231. Maranta, Plum. 376. MARANTACE-SJ, 376. Marattia, Sm. 420. MABATTIE^:, 420. M arcgraavia, L. 226. MARCGRAAVIE^E, 226. Marchantia, March. 434. MARCHANTIACEJE, 434. Margosa, 234. Marigold, 293. Mariscus, VaM, 401. Marjoram, 321. Marking-nut, 247. Maiiea, J?o#&. 263. Marmalade, 236, 302. MaiTubium, Z. 320. Marsdenia, -R. Zr. 311. Marsh-mallow, 222. Marsilea, Z. 427. MARSILEACE^E, 427. Martynia, L. 323. Maruta, Case. 292. Marvel of Pew, 330. JJfasfic, 247. Mate, 303. Mafrco, 293, 348. Matricaria, L. 292. Matthiola, jR. Br. 212. Maurandia, Ortey. 327. Mauritia, 394. MAYACE2E, 388. Meadow Saffron, 387. Meconella, Nutt. 207. Meconopsis, Vig. 207. Medeola, Gronov. 384. JMc, 252. Medinilla, Gaudich. 263. Medlar, 258. Megacarpsea, -D.C. 206, 211. Megaclinium, Zme?/. 372. Melaleuca, L. 259. Melambo bark, 276. Melampyrum, Z. 327. MeJanorrhea, Wall. 257. MELAXTHACEJE, 85. Melanthium, L. 385. Melastoma, i. 263. MELASTOMACE^, 263. Melhania, Forsk. 223. Melia, L. 237. MELIACEJE, 237. Melianthus, L. 240. Melicocca, 231. Melilotus, 252. Meliosma, Endl. 230. MELIOSME^E, 230. Melobesia, Lamx. 447. Melon, 274. Melosira, ^4^. 454. MEXISPERMACEJE, 201. Menispemium, Tournef. 201. Mentha, L. 320. Mentzelia, i. 275. Menyanthes, L. 308. Mercurialis, L. 338. Mercury, English, 331. Mertensia, #. i?. /f. 344. Mertensia, Willd. 419. MESEMBBYANTHA- CEJE, 269. Mesembryanthemum, L. 269. Metrosideros, It. Br. 259. Mespilus, 258. METASPERMS, 357. Metroxybn, 394. . Metzgeria, Radd, 434. Mezereon, 335. Mezieria, Gaud. 275. Michelia, i. 199. Miconia, DC. 263. Microcachrys, 360. Microcoleus, Desmaz. 454. Miersia, Lindl. 388. Mignonnette, 213. Milk-ivorts, 231. J/^/ete, 405. Mimosa, Z. 251. MIMOSEJE, 251. Mimulus, Z. 327. Mimusops, L. 302. JlfMrf, 320. Mirabilis, L. 330. Mistletoe^, 352. Mitrasacme, ia6:7/. 306. Mitclia-mitcho, 237. Mitreola, Z. 306. Mock-Orange, 267. Modecca, Z. 270. MOLLUGINEJE, 268. Mollugo, Z. 268. Momordica, Z. 273. Monacautlms, 373. Monarda, 321. MONJMIACE^:, 200. Monkey-apple, 228. Monkey-pot trees, 261. Monkshood, 197. Monuina, -Rw?'s ^ Pv. 232. MONOCHLAMYDEJE. 329. MONOCOTYLEDONES, 367. Monodora, Dun. 200. Monotaxis^firow^n. 338. Monotropa, A r w^. 297. MONOTROPEJE, 297. Monsonia, Z. 238. Montia, Michel. 269. Moon-seed, 201. Morchella, Z>z7/. 4G5. Morells, 466. Moreton-bay Pine, 360. Morinda, FaU 238. MORINGACE^:, 255. Morisia, 212. Moronobea, Anbl. 227. Moms, Tournef. 342. Mosses, 431. Mountain Ash, 258. Mouriria, J?/ss. 263. Moutabea, ^Iw6/. 232. a, 292. INDEX TO SYSTEMATIC BOTANY. 721 Mucor, Mich. 453. MUCORINI, 458. Mucuna, Adam. 253. Mudar, 310. Mulberry, 343. Mulinum, Pers. 278. Mullein, 328. Mundita, Kunth, 232. Munjeeth, 287. Musa, Tournef. 377. MUBACE2B. 377. Muscari, Tournef. 386. Musci, 431. MusciNE-as, 428. Mushroom, 4G2. Musk-plant, 327. Mustard, 212. Mustard-tree, 306. Mutisia, i.//. 291. Myanthus, Zmc?/. 373. Myoporum. .Z?Ax & Sol. 321. Myosotis, I/. 318. Myrica, L. 844. MYRICACE^;, 344. Myricaria, Desv. 218. Myrionema, Grev. 450. Myriophyllum, F?7/. 264. Myriotrichia, Harv. 450. _ Myristica, _L. 334. MYRISTICACE^E, 334. Myrobalan, 262. Myroxylon, Mut. 254. 3/yrrA, 248. MYRSINACEJE, 301. Myrsine, L. 301. MYRTACE>E, 259. MYRTEJE, 259. Myrtle, 259. Myrtus. Tournef. 259. MYXOMYCETES, 470. Myzodendron, Sol. 352. NAIADACE^, 389. Naias, Willd. 389. Napoleona, Pal. 267. NARCISSE./E, 378. Narcissus, L. 378. Nardostachys, D(7. 288. Narthecium, Mcehr. 399. Narthex, J^a/c. 282. Nasturtium.-R. Br. 212. Natchnee, 406. Navicula, ^ory, 454. Nectandra, Rottl. 333. Nectarine, 258. Nectria, .Fms, 468. Neem-tree, 234. Negimdo, Mcench. 231. NELUMBIACE^E, 204. Nelumbiunij 7wss. 204. Nemophila. Bartl. 311. Neottia, L. 375. Nepal Barley, 405. NEPENTHACEJE, 335. Nepenthes, i. 335. Nephelium, L. 231. Nerium, L. 308. t 236. Order, 341. , Stinging, 342. Nettle-tree, 344. Neurada, i. 257. NEURADE^, 257. New-Jersey Tea, 246, New-Zealand Flax, 386. Nicotiana, Tournef. 314. Nidularia, l^^s, 464. Nigella, Tournef. 196. Nightshade, 316. Nipa, Rumph. 395. Nitella, ^. 444. Nitraria, X. 233. Nolana, i. 317. NOLANACEJE, 317. Nopal-plant, 277. Norfolk-Island Pine, 360. Nostoc, FawA. 452. Nidlipores, 448. Nuphar, ^mi^A, 204. Nut-galls, 351. Nutmeg, 334. Nutmegs, Brazilian, 333. Nuytsia, .K. ^r. 352. Nux-vomica, 306. NYCTAGIXACE^;, 330. Nvctanthes, Jwss. 305. Nymphgea, Neck. 203. NYMPH^ACE^, 203. Nyssa, Gron. 263. OaA; ^rees, 350. Oats, 405. Obolaria, i. 303. OCHNACE^E, 242. (EDOGONIE^E, 453. Qidogonium, Link, 452. (Enanthe, Lam. 280. CEnothera, L. 264. Oil of Ben, 255. Oil of Bergamot,%3. Oil of Spike, 320. Oz7 of Palms, 394. OLACACEJB, 304. Old-man's beard, 382. Oldenlandia,P.^r.287. Oldfieldia, Benth, 340. Olea, Tournef. 305. OLEACEJE, 304. OLE^E, 304. Oleander, 309. Olibanum, 248. Oligomeris, Camlass. 213. m?, 305. Seaweeds, 448. Omphalobium, Gcertn. 248. ONAGRACEJE, 263. Oncoba, Jbr*. 214. Onion, 386. Onobrychis, Tournef. 252. Onopordum, Z. 294. Opegrapha, Pe?*s. 469. Opercularia. ^4. JS/cA, 267. Ophiocaryon, Schomb. 230. OPHIO GLOSSED, 420. Ophioglossum. L. 421. 3A 722 INDEX TO SYSTEMATIC BOTANY. Ophiopogon, Ait, 385. Ophrys, Sivz. 371. Opium Poppy, 207. Opoponax, Koch, 282. Opuntia, Tournef. 276. Orach, 331. Orange, 235. ORCHIDACEJE, 369. Orchids, 369. OcM, 470. Orchis, L. 371. Oreodaphne, Afo$, 333. Origanum, Z. 320. Ornithogalum, Z. 386. Ornithopus, L. 250. Onus, Pers. 305. OROBANCHACE^;, 324. Orobanche, L. 324. ORONTIACEJE, 396. Oroiitium, L. 396. Orris-root, 381. Orthanthera, TFMtf. 311. Oryza, Z. 404. Osage Orange, 343. Oscillatoria, J?osc, 454. OSCILLATOBIACEJE, 453. Otter*, 346. Osmunda, L. 420. OSMUNDEJE, 420. Ostrva, Scop. 351. Osyns, Z. 353. Otto of Hoses, 258. Ouvirandra, Thouars, 390. OXALIDACE^E, 237. Oxalis, L. 237. Oxleya, .4. Cunn. 235. O#% 301. Oxvcoccus, Tournef. 297. Oyster -bay Pine } 361. Padina, Adans. 449. Paeonia, Tournef. 196. P^EONIE^:, 196. Palissandre, 253. Paliurus, Tournef. 246. PALMACE^;, 391. Palmella, ^A. 452. . 391. Palmyra-wood, 394. Pampas-grass, 406. Panax, i. 282. Pancratium, i. 378. PANDANACEJE, 394. PANDANE^E, 395. Pandanus, L.fl. 395. Pandorina, Ehrenb. 455. PANGIACEJE, 270. Pangium, Reinw. 270. PANICEJE, 403. Panicum, Z. 403. Pansy, 217. Papaver, Tournef. 205. PAP AVERAGES, "205. Papaiv, 270. PAPAYACE^E, 270. Papayrola, -4w6/. 216. Paper- Mulberry, 343. PAPILIONACE^, 250. Pappea, ^. # Z. 231. Papyrus, W r 7W. 401. Paraguay Tea, 303. Pareira brava, 201. PAR IET ALES, 209. Parietaria, Tournef. 341. PARIETAEJE^E, 341. Paris, Z. 384. Parkeria, Hook, 419. PARKERIEJE, 417. Parkia, i. 251. Parmelia, Fr. 469. Parmentiera, D(7.323. Parnassia, L. 228. Paronychia, /wss. 216. PARONYCHIACE.E, 268. PARONYCHJE^E, 268. Paropsia, Nor. 271. Parrotia, C. A. Mey. 278. Parsley, 282. Parsnep, 282. Partridge canes, 394. Paspaliim, i. 406. Passi flora, Jwss. 270. PASSIFLORACEJE, 270. Passion-Jloiuers, 271. Patchouli, 321. Patellaria, JPrwa, 465. Paullinia, L. 230. Pa via, jBoerA. 230. Pavonia, Cav. 221. P^ac/?., 258. Peach, Sierra Leone, 287. P^r, 258. Peas, 253. PEDALIACEJE, 323. Pediastrum, Mey en, 454 Pedicularis, i. 328. Peganum, L. 240, 241. Pelargoni um v Herit. 238. X Peliosanthes, 385. Pellitory of Spain, 292. Penaea, Z. 340. PEN^EACE^;, 340. Penicillaria, A"w/^7?,406. Penicillium, Lk. 467. Penny -royal, 320. Pentaptera, Roxb. 262. Penthorum, Z. 267. Pentstenion, Herit. 327. Peperomia, ^. P. 348. Peplis, Z. 2G5. Pepper, 347. Pepper-dulse, 448. Peppermint, 320. Peppers, 347. Peranospora, -De P. 457. Pereskia, Jfum. 276. Periploca, i. 318. Persea, JV^s, 353. Persimmon, 303. PETALOIDE^E, 368. PETIVERIEJE, 332. Petroselinum, Hcffm. 282. Petunia, Juss. 314. Peucedanum, Z. 282. Peziza, Dill. 465. Pliaca, i. 252. PHACIDIE^, 465. PH^OSPORE^:, 4oO. PHALARIDEJE, 403. Phalaris, L. 403. Phallus, L. 464. INDEX TO SYSTEMATIC BOTANY. 723 PHANEROGAMIA, 193. Pbarbitis, Chris. 312. Phascum, L. 432. Phaseolus, L. 250, 252. PHILADELPHES, 266. Philadelphia, L. 267. PmLESIACES, 383. Pliillyrea, Tournef. 305. Philodendron. Schott. 397. PHILYDRACES, 388. Phleum, L. 406. Phlomis, L. 320. Phlox, L. 311. Phoenix, L. 391. Phormiuin, Forst. 386. Phragmites, L. 406. Phryma, L. 321. Phycomycetes, 455. Phyllanthus, L. 338. Phyllocactus, Link. 277. Phyllocladus,Z.a469. Poc/c J2oa^, 214. Rondeletia, ^/. 287. Rosa, Tournef. 257. ROfiA0E2B, 255. ROSE^E, 257. Rose-apples, 260. Rosemary, 321. Hoses, 258. Rosewood, 253. ROSID^E, 257. Rosmarinus, Z. 320. Rottlera, JRoa*. 338, 340. Roupellia, T? r ?/. 309. ROXBURGHIACEJE, 383. Royena, Z. 302. Rubia, Tournef. 286, 287. RUBIACE2E, 285. Rubus, Z. 257. INDEX TO SYSTEMATIC BOTANY. 725 Ruellia,322. Kumex, L. 329. Ruppia, L. 389. Kuiscus, Tournef. 385. Rushes, 399. Jfowte, 461. Kuta, Tournef. 241. I1UTACE2E, 240. Rye, 405. Rye-grass, 406. Sabadilla, 387. Sabal, Adans. 391. SABIACKiE, 202, 247. Sandal-iuood, red, 361. Sandarac, 361. Sangiunaria, Z>?77. 207. 472. Saccharum, Z. 405. Safflower, 293. Saffron, 381. Sai/apenum, 282. %r, 321. Sageretia. Brongn. 246. Sagina, Z. 219. Sagittaiia, Z. 389. Sago-palms, 391. Sago-plants, 366. Saguems, Rumph. 394. Sagus, Gcertn. 391. Samtfoin, 252. -Safe/?, 374. SALICACE^E, 345. Salicine, 346. Salicornia, Tourn. 331. Salisburia, $w. 361. Salix, Z. 345. Sallows, 345. Salomonia, Lour. 232. Safcfl/y, 293. Sal^ola, Z. 331. SALVADOBACE^:, 305. Salvertia, /Sf.-t/. 261. Salvia, Z. 320. Salvinia, Mich. 427. Sambucus, Tourn. 285. Samolus, Tournef. 300. Samphire, 282. SAMYDACE^E, 271. Sandal-wood, 353. Sanicula, Tournef. 279. Sanseviera, Thunb. 386. SANTALACE^J, 353. Santalum, Z. 353. Sap-green, 246. SAPINDACE^E, 229. SAPINDE^:, 230. Sapindus, Z. 230. Sapodilla-plum, 302. Saponaria, Z. 219. Saponine, 220. SAPOTACE^E, ^02. Sapria, (?r^ 355. SAPBOLEGNIE^E, 455. Sapucaya-nuts, 26 1. Sarcina, Goodsir, 471. Sarcocephalus, 287. Sarcocol, 340. SarcocoUa, -BTM. 340. Sarcophyte, Sparrm. 353. Sargassum, Rumph. 449. Sarracenia, Z. 205. SABBACENIACE^E, 205. Sarsaparilla, 384. Sarsaparilla, wild., 283. Sassafras, JV&, 333. Sassafras, 333. Satin-wood, E. I. 235. Sauraja, Willd. 226. SAUBAJE^E, 226. Sauridia, Jfarv. 379. SAUBUBACE^:, 348. Saururup, Z. 348. SAUVAGESIACEJE, 217. Savine, 361. Savory, 321. Saxifraga, Z. 265. SAXIFBAGACEJE, 265. Saxifrages, 266. Scabiosa, JRo'm. <^ /SfcAw/z5. 288. Scale-Mosses, 433. Scsevola, Z. 295. Scammony, 312. Scaphopetalum. Mast. 223. Scarlet Runner Beans, 252. SCEPACEJE, 340. Scheuchzeria, Z. 389. Schleichera, Willd. 231. Schmidelia, Jfwrr. 231. Sciadopit ys, 8. $ Z. 360. Schinus, Z. 247. Schiz^ea, Smith, 420. SCHIZ^EE^E, 420. Sclnzandra. Z. (7. J2ecA, 202. SCHIZANDBACE^I, 202. ScMzanthus, R. $ P. 333. SCHIZOMYCETES, 471. Schizopetalon, Hook. 211. Scliobeiia, Moq. 331. Schoenus, Z. 400. Schweinitzia, J?//. 297. Scilla, Z. 384. /Sfc/o Turpentine, 247. Scirpus, Z. 401. SCLEBANTHE^, 268. Scleranthus, Z. 268. Sclerolobium, Fb^. 251 . Scolopendrium, Smith, 419. Scorzonera, Z. 293. ^co^cA Fir, 358. Screw Pines, 395. Scrophualaria, Tournef, 326. SCBOPHULABIACEJE, a^, 225. Sea-Buckthorn, 336. Sea-Kale, 212. Seaweeds, 436. &?- Wracks, 449. Sechium, P. ^r. 273. Seeuridaca, Z. 232. -Sfed^c*, 400. Sediim, Z. 267. 726 IKDEX TO SYSTEMATIC BOTAKT. SELAGINACEJE, 321. Selaginella, Spring. 425. Selago, L. 322. Selliera, Cav. 294. Semecarpus, L. 247. Semen contra, 292. Sempervivum, L. 267, 268. Senecio, Less. 293. Senna, 254. Sequoia, Endl. 360. Sesamum, L. 323. Sesuvium, Z. 269. Setaria, Z. 403. &w#fe Orange, 235. Shallot, 386. /Sfta/oo, 406. Shamoola, 4QQ. * . Shea, 302. Shorea, Roxb. 225. Sicyos, Z. 273. Sida,Z. 221. Silene, Z. 219. SILENE.E, 219. Silk- cotton trees, 222. Silk-weeds, 451. Silver-Fir, 360. Simaba, ^Iw6/. 242. Simaruba, ^Lw6/. 242. SlMARUBACEJE, 242. Sinapis, Tournef. 212. Singhara-nut, 264. Siphocampylus, PoA/, 294. Siphonia, Benth. 339. Sisyrinchium, Z. 381. Sizygites, Tul 458. ^A;^^/^^ Cabbage, 397. Smeathmarmia, Soland. 270. SMILACEJE, 383. Srnilacina, Desf. 385. Smilax, i. 384. Smithia, ^t^. 252. Snake-gourd, 274. Snake-nut, 230. Snap-dragon, 327. Snow-berry, 285. Snowdrop, 379. Snowdrop-tree, 304. Snoiv-jlake, 379. Soap-root, 220. Soap-worts, 229. Sobralia, 374. SOLANACE^, 313. Solanum, X. 314. Soldanella, i. 301. Solenosteinma, Heyne, 310. SoUya, Zew^. 243. Solomons Seal, 386. Sophora, i. 250, 253. Sorghum, Pers. 403. fibrrf/, 329. Souari-nuts, 227. Sour-sops, 200. Southernwood, 292. SPADICIFLOB^, 390. Spcetlum, 269. Sparganium, i. 369. Sparmannia, X. 225. Spathularia, Pe? % s. 466. Spatulum, 269. Specularia, ZTm^. 295. Speedwell, 328. #/>e#, 406. Spergida, i. 268. Sperrnacoce, i. 286. Spliseria, L. 468. Sphaerocarpus, Mich. 435. SPHJEROCOCCEJE, 447. Sphcerococcus, Grev. 447. Sphaerophoron, Pers. 469. Sphaeroplea, Agh. 452. Sphserostemma, Blum. 202. SPHAGNACEJE, 432. Sphagnum, Dillen. 432. Spider-worts, 387. Spigelia, i. 306. /Sr/wfo, ot7 o/, 320. Spikenard, 288. Spinach, 331. Spinach, New-Zealand, 269. Spinacia, Tournef. 331. Spindle-tree, 245. Spiraea, Z. 257. SPIB^ID^:, 257. Spirilla, ZTa.ss. 471. Spirogyra, ZmA', 452. Splachnum, Z. 432. Split-Mosses, 432. Spondias, Z. 247. Spondiese, 247. Spruce Fir, 360. Spumaria, Pers. 470. Spurge Laurel, 335. 4*00, 386. fetaavia, Thunb. 278. Stachys, .Bew^. 320. STACKHOUSIACE^E, 245. Stagmaria, Jack, 247. Stangeria, Moore, 365. Stapelia, i. 310. Staphylea, L. 231. STAPHYLEACE^:, 231. Star- Anise, 199. Star-apple, 302. Star-wort, 349. Statice, i. 329. Stauntonia, DC. 202. Stavesacre, 198. SteUaria, i. 219. STELLATE, 287. Stemonitis, Gled. 471. Stephanosphaera, Colm, 455. Sterculia, Z. 223. STERCULIACE^E, 223. STERCULIE^E, 223. Stereocaulon, Schreb. 469. Sternbergia, Artis, 379. Sticta, Schreb. 4( 9. Stictis, Per. 465. Stigmatia, Fries, 468. St.-Ignatius''s Bean, STILAGINACE^E, 343. Stilago, Z. 343. Stilbe, Berg. 321. Stillingia, 340. INDEX TO SYSTEMATIC BOTANY. 727 Stinging-nettle, 342. Stink-horns, 464. Stipa, L. 404. St. Johns-wort, 228. Stock, 212. Stone-crop, 268. Stone-pine, 360. Storax-gum, 304. S tor ax', liquid, 278. Strasburg Turpentine, 361. Stratiotes, L. 382. Strawberry, 258. Strelitzia, Banks, 377. Streptanthus, Nutt.212. Streptoearpus, Zm<$. 324. Streptoch8eta,A r . 294. STYBACACE^E, 303. Styrax, Tournef. 303. Subularia, Adam. 21 .1. Succory, 293. Sugar-cane, 405. Sumach, 247. Sumbul, 282. Sundews, 215. Sun-flower, 293. Sun-hemp, 222. Surinam Medlar, 302. Swamp Pine., 360. Swartzia, JF7/d. 250. Sweet-leaf, 304. Sto Potato, 312. Siveet-sop, 200. Sweet Vernal Grass, 406. /Sw^tf Fiofctf, 216. /Sfc?^ William, 220. Swietenia, Z. 234. Sycamore-fig, 343. Symphoricarpus, Z)*7/. "285. Symphytum, Z. 318. Symplocarpus, Schult. '397. Symplocos, Jctcy. 304. SYNGENESIA, 292. SYNSPOBE^;, 453. Syringa, Z. 305. Syringa, 267. Tabasheer, 407. Tabernaemontana, P/wm. 309. Tacamahaca, 228. Tacca, Por^. 369. TACCACEJS, 3('8. Tacsonia, Jtw*. 271. Talinum, ^4r/a/vS. 269. Tallow-tree, 340. TAMARICACE^E, 217. Tamarind, 254. Tamarind-plum, 254. Tarnarindus, Z. 251. Tamarisk, 217. Tamarix, Z. 217. Tamus, Z. 369. Tanghinia, Thouars, 309. Tangle, 451 . Taonia, /. -4^-. 449. Tapioca, 340. Tara, 397. Taraxacum, 7?/ss. 291. Tarragon, 292. Tasmannia, JK. ^r. 199 TAXACEJE, 361. Taxodium, i. C, J2/cA, 358. Taxus, i. 361. Tea, 226. 7>a, (7a/?e of Good Hope, 293. Tea, Paraguay, 303. jf. ' Interpetiolar stipules, 54. Leaf-stalk, 49. 736 GENEKAL AND GLOSSARIAL INDEX. Leaves, absorption by, 565. , arrangement of, 42. , development of, 599. , forms of, 55, 57. , modifications of. 66. , radical, 48. , structures of, 539. , veins of, 540. Legume, 145. Lenticels, 522. Lepidotus, 66. Liber, 517, 522, 533. Liber-cells, 477. Liber-region, 576, 529. Lichens, morphology of, 468. , reproduction of, 469. Life of plants, 473. Light, action of, 549, 575, 605, 652. Ligulate corollas, 112. Ligule, 54. Liliaceous perianth, 110. Limb of calyx, 107. of corolla, 112. of petal, 109. Lindley's System, 187. Linear, 58. Linear-lanceolate, 58. Linnaean System, 18. Lip, 115, 370. Lobed leaves, 60. Lobes, 61, 65. of anther, J22. of calyx, 107. Loculi of anthers, 122. of ovaries, 128. Loculicidal, 143. Locusta, spikelet of a grass, 78, 402. Lodiculae, 117. Lomentum, 147. Luminosity of plants, 649. Lycopodiaceoe, morpho- logy of, 423. , reproduction of, 409. , stems of, 525. Lyrate, 61. Mace, 154. Macrcspore, 139, 424. Macrotiierms, 660. Macrozoospore, 438. Male flowers, 94. Malpighiacese, stems of, 530. Manubrium, 446. Manures, 557. Marcescent calyx, 109. Margins of leaves, 59. Marine plants, 561. Marsileacese, morphology of, 426. , reproduction of, 626. Mealy endosperm, or al- bumen, 155. Medulla, 529, 532. Medullary rays, 529, 532. . sheath, 529. Meiotherms, 660. Membrane, cell-, 481. of cells, composition of, 490. , porosity of, 481. Membranous, 65. Merenchyma, 508. Mericarps, 144, 150. Meristem, 514. Mesocarp, 141. Mesothecium, 541. Mesotherms, 660. Metamorphosed leaves, 66. Metamorphosis, 88. Metastasis, 555. Methods of study, 3. Metis, 641. Microgonidia, 441. Micropyle, 137, 149, 631. Microscope, 5. Microspores, 126, 424. Microtherms, 660. Microzoospore, 438. Midrib, 55. Migration of species, 662 Milk-vessels, 523. Milky juices, 582. Mineral products, 582. Mistletoe, 20. Molecules, 483. Monadelphous, 97, 126. Monandrous, 124. Moniliform, 120. ducts, 510. Mono^arpic, 545. Mono3hlamydeous, 93, 116. Mono cot yledones, 12, 14. , roots of, 534. , stems of, 528. Monoclinous, 638. Monoecious, 94, 637. Monopetalous, see Gamo- petalous, 97, 112. corolla, 112. Monophyllous, 116. Monopodial, 39, 82. Monosepalous, 107. Monothalarnic, 145. Monstrous carpels, 128. Morphology, general, 7. - of Cryptogamia, 408. of Phanerogamia, Mosses, morphology of, 428. , reproduction of, 428, 432. , stems of, 525-. Movements of nucleus, 497. of plants, 650. of protoplasm, 548. of spermatozoids, 550. of tendrils, 657. of zoospores, 550. Mucronate, 59. Mules, 641. Multijugate, 63. Multilocular ovary, ISO. Multiplication, 92, 579. Muriform parenchyma, 508. Mycelium, 413. Naked buds, 71. flower, 93. Names of plants, 164. , generic, 165. , specific, 165. , varietal, 168. Napiform root, 16. Natant, 65. Natural classification, 182. families, 160. selection, 163. Navicular, 110. Neck-3ell, 628. Nectary, 110 GENEBAL A1SD GLOSSARIAL ITfDEX. Nectaries, 114. Nervature of leaves, 55. Nerves, 55. Neuter flowers, 94. Nitrogen, sources of, 559. , effect of, 576. . elimination of, 575. Nitrogenous constituents, 578. Nodding, 40. Nodes, 21, 42. Nodose, 40. Nomenclature, 164. Noterophiles, 661. Nucleolus, 497. Nucleus of cells, 496. , changes in, 588. band, 588. of ovule, 136. Nuculanium, 150. Nucule of Charaeere, 445. Nucules, 140. Number, 90. Nutans, 40. Nutriment, sources of, 557. Nutrition of cells, 547, 551. in Algae, 554. Nymphasaceas, stein of, 530. Obcorclate, 59. Obdiplostemonous, 124. Oblique, 58. Obliquity, 101. Obovate, 57. Obtuse, 59. Obvolute, 73. Occluse, 114. Ocrea, 54. Offsets, 33. Oils, essential, 504. , fixed, 503. , volatile, 581. Oosphere, 156. Oospores, 455, 628. Opercular dehiscence of anthers, 123. Operculum of Mosses, 423. Opposite, 42. Orbicular, 57. Orchids, roots of, 536. , names of, 169. Organic acids, 578. Organ ogeny, 87. Organs, 73. , development of, 87, 591. , essential, 118. , internal anatomy of, 525. Orthotropous, 138. Osmose, 562. Ovary, 12, 128. Ovate, 57. Ovate-lanceolate, 58. Overhanging, 40. Ovule, 136. , characters of, 136. -, development of, 601. , parts of, 137. of Angiosperms,630. of Gyinnosperins, 628. , of Phanerogams, 627. , structure of, 541. Oxygen, evolution off 575. Ozone, action of, 559. Palate, 113. Pales, 76, 117, 403. of capitula, 80. Palisade tissue, 540. Palmate, 63. Palmifid, 61. Palminerved, 55. Palmipartite, 61. Palrnipinnate, 64. Palrnisect, 61. Panicle, 78. Paper, botanical, 4. Papilionaceous corolla, 111. Pappus, 108. Paracellulose, 492. Parallel-nerved, 55. Parasitic plants, 20. Parenchyma, 507. Parietal placentas, 132. Paripinnate, 63. Partial petiole, 62. Passages, intercellular, 523. Patent, 41. Pectase, 581. Pectin, 581. Pectose, 581. Pedate, 61, 63. Peclatifid, 61, 63. Pedatipartite, 61, 63. Pedatisect, 61,63. Pedicel, 75. Peduncle, 75. , foliaceous, 85. Peltate, 59. anthers, 124. stigma, 135. Pendent, 40. Pendulous, 40. ovule, 137. Penicillate stigmas, 135. Penninerved, 55. Pentadelphous, 126. Pentamerous flowers, 91. Pentastichous, 44. Pepo, 151. Perennial plants, 544. Perfect flowers, 91, 118. Perfoliate, 58. Perforated cells, 493. Perianth, 11, 104. , characters of, 108, 114. of Grasses, 117. Periblem, 515. Pericambium, 515, 597. Pericarp, 140. Perichsetial leaves, 433. Perichastium, 433. Periderm, 522. Peridium, 467. Perigone, 104. ( Jungermanniacese), 433. Perigonial leaves, 433. Perigynium, 117. Perigynous, 99, Periodicity in plants, 544. Peripherical embryo, 157. Perisperm, 154. Peristome, 431. Perithecia, 468. Persistent, 86. calyx, 109. corolla, 114. Personate, 113. Perulae, 71. Petals, 11, 103, 109. strap-like, 110. Petaloid, 110. filament, 120. perianth, 115. Petiole, 49, 51, 148. , structure of, 540. 3 B 738 GEKEEAL AND GLOSSAEIAL INDEX. Petiolule, 62. Phanerogamia, 9, 193. Plumule, 14, 32, 69, 122, 156. Podosperm, 137. Pollarding. 615. Pollen, 17, 119, 126, 623. , examination of, 625. of Gymnospermia, 625. -, formation of, 624. Pollen-masses, 126, 624. Pollen-tubes, 627, 633. Pollinia, 127, 624. Pollinodium, 465. Polyadelphous, 100. Polyandrous, 124. Polycotyledonous, 157. Polygamous, 94, 637. Polypetalous, 97, 110. Polyphyllous, 115. Polysepalous, 97, 107. (rilyx 107 Prothallium, 409. Protogynous, 638. Protonema, 411, 428. Protoplasm, 495. ~ rcppocliictioii oty 622. Phellogen, 522. Philotherms, 660. Phloem, 517, 522. Phosphorescence, 649. Phyllocyanine, 499. Phyllodes, 51. Phyllodia, 66. Phyllody, 87, 128. Phyllome, 11, 20, 41. Phyllotaxy, 42. of flowers, 89. Phylloxanthine, 499. Physiology, 473. Pileorhiza, 535. Pileus, 463. Pilose, 41, 65. Pinnae, 62, 65. Pinnate, 62. Pinnatifid, 60. Pinnatipartite, 60. Pinnatisect, 60. Pinnules, 61, 65. Pistils, characters of, 127. , structure of, 541. Pitcher-plants, 66. Pitchers, 66. Pith of Dicotyledons, 532. Pits of cell-membrane, 487. Pitted cells, 485. ducts, 512. Placenta, 129, 132. Placentoids, 122, 541. Plaited aestivation, 105. Planogamete, 459. Plants, description of, 170. , distribution of, 663, 668. , food of, 554, 555. fossil 699 j ni OYG incuts oiy 0*10* Pruinose, 65. Pubescent, 65. Pulvinus, 53. Putamen, 141. Pycnidia, 469. Pyrene, 141. Pyxis, 148. Quinate, 63. Quincuncial, 44, 104. aestivation, 104. Eaceme, 78. Paces, nature of, 160. Eachis, 62. Eadiant florets, 81, 290. Eadiate, 135. Eadical leaves, 49. Eadicle, 15, 156, 592. Eadix multiceps, 32. Eamal leaves, 49. Eamification, 38, 41, 70. mnrlpa nf ^& Polythalamic, 137. Pomum, 151. Porosity of membrane, 481. Porous cells, 485-493. dehiscence of anthers, 23. of fruit, 143. Posterior, 89, Postrentitious bulbs, 26. Praefloration, 105. Prgefoliation, 72. Prtemorse, 31, 592. Praeventitious bulbs, 26. Pressure, 567. Prickles, 687. Primary membrane, 482. Primine, 137, 153, 601. Primitive fibre, 484. Primordial parenchyma, 479. utricle, 495. Procambium, 515. Procumbent, 40. Proembryo, 629. Progressive vascular bun- dles, 517. Prolification, 88. Propagation, 616. Prosenchyma, 507, 508. Prostrate, 40. Protandrotis, 638. Protecting-sheath, 517. Proteinaceous matters, 500, 579. ~ - , moQcS oi, oo. , monopodial, 38. , sympodial. 39. Eamosissimus, 41. Eaphe, 138, 153. Eaphides, 506, 582. Eate of growth, 612. Eay, 81. Eays, medullray, 529,532. Eeagents, chemical, 6. Eeceptacle of flowers, 88, 100. , anatomy of, 542. coiiiiiioii 80 , Fungi, 413. Eeceptacular tube, 99. 106, 107. Eeclinate, 73, 104. Eeduplicate, 105. Eegions of altitude, 672. of vegetation, 695, Eegular calyx, 108. corolla, 110. flower, 99. Eejuvenescence, 584. Eeniform, 58. Eepand, 59. Eepens, 40. Eeplurn, 132, 148, 209. , simplest, 8. Plasinodiocarp, 470. Plasinodium, 413, 495. Plastidule, 496. Pleiomery, 93. Pleiotaxy, 92. PI rome, 515. Plicate, 74, 104. aestivation, 105. GENERAL AND GLOSSARIAL INDEX. 739 Eepresentative species, 664. Reproduction, 613. , vegetative, 613. of Cryptogamia, 409, 416. of Thallophyta, 435. of Phanerogamia, 581, 622. Reservoirs for secretions, 523. Resins, secretion of, 581. Respiration of plants, 576. -, chlorophyllian, 574, 577. Rosaceous corolla, 110. Rosette, 629. Rosulate, 47. Rotate corolla, 112. Rotation of cell-sap, 448. Ruminated endosperm or albumen, If, 6. Runcinate, 61. Runners, 33. Saccate, 108. 3, 110. , general, 575, 577. Resting-spore, 442, 544. Resupinate ovule (of Plumbaginaceoe), 137. Reticulated cells, 489. vessels, 510. Retinaculum, 127. Retroserrate, 59. Retuse, 59. Reversion, 643. Revolute, 59, 74. Rhizome, 15, 30. Rhizotaxy (arrangement of roots), 16. Rhomboiclal, 58. Rbytidome, 522. Ribbed, 40. Ribs, 55, 540. Rind of Monocotyledons, 528. Ringent, 114. Ringing of stems, 573, Root, 10, 14. Roots, adventitious, 15, 17, 537. , aerial, 18. , axial, 15. , buds on, 15. , development of, 596. , direction of, 589. , fibrils of, 116. , selecting power of, 563, 564. , structure of, 533. , tuberous, 17, 538. Root-action, 565. Root-cap, 535, 597. Root-hairs, 17, 537. Root-stock, 30. Sagittate, 58. Salver-shaped, 112. Samara, 148. Sap, ascent of, 566, 568. , causes of, 567. , crude, 572. , descent of, 572. , force of, 568. 572. Sapindacese, stems of, 530. Saprophytes living on decaying matter, 558. Sap-wood, 532. Sarcocarp, 141. Scabrous, 65. Scalariform cells, 489. vessels, 512. Scales, 519. of corollas, 114. Scaly, 66. - bulb, 25. Scandens, 40. Scape, 75. Scattered, 42. Schizocarp, 143. Sclerenchyma, 508. Scorpioid cyme, 82. Scurfy, 66. Secondary layers, 483. spiral, 46. Secretion, 579. Secretions, canals for, 524. , reservoirs for, 524. Secretory system, 523. Secund, arranged on one side only. Secundine, 153, 631. Seedling, development of, 591. Seeds, 10. , characters of, 153. Seeds, vitality of, 544, 645. Segmentation, 585. Segments, 61, 65. Selecting power of roots, 503. Selection, natural, 163. Self-impregnation, 639. Sensitive plants, 650. Sepals, 11, 106. Septa of cells, 480, 507. Septenate, 63. Septicidal, 143. Septifragal, 142. Septum of anthers, 122. of fruits, 142. Sericeous, 65. Serrate, 59. Sessile, 50. flower, 75. leaves, 50. stigma, 133. Seta of Mosses, &c., 431. Setae, 66. Setose, 41, 65. Sexual reproduction, 620. Sheath, leaf-,52. Sieve disks, 488. cells, 488. Silica, excretion of, 582. Siliceous deposits, 492. Silicula, 148. Siliqua, 148. Simple leaf, 55. - pistils, 129. Simultaneous vascular bundles, 516. whorls, 48. Sinistrorse, 106. Sinuate, 60. Sinus, 107. Skeleton of plants, 492. Sleep of plants, 652. Slips, 616. Snow-line, 673. Soft bast, 522. Solitary flowers, 75. SoriofAlgje, 439. of Ferns, 419. Sorosis, 152. Spadix, 78. Spathe, 76. Spatulate, 58. Species, names of, 159, 165, 166. , nature of, 159. , origin of, 163. 740 GENEEAL AND GLOSSAEIAL INDEX. Species, representative, 664. Specific character, 177. centres, 665. Spermatia, 469. Spermatozoids, 416, 448, 464, 550. Sperm-cells, 621, 623. Sperm ogonia, 469. Spicular cells, 479. Spike, 78. fcpikelet, 76. Spines, 68, 519. Spinose-serrate, 59. Spinosus, 66. Spinous, 67. Spiral embryo, 157. , fundamental, 45. growth, 656. (leaves), 43. , secondary, 45. vessels, 510. Spongioles, 539. Sporanges, 154, 409. Spore-fruits, 427. Spores, 409, 621. , resting, 441. , vitality of, 544. Sporocarps, 427. Sporogonium, 430. Sports, 642. Spur, 110. Spurious dissepiments, 131. Spurred petals, 110. Stamens, branched or compound, 120, 601. , characters of, 119. , development of, 601. of Gymnospermia, 124. , number of, 124. Staminode, 117. Standard, 111,249. Starch, 501. Starch-granules, 502. , test for, 502. Statistics of vegetation, 696. Stellate cells, 478. Stems, 10, 20. , anatomy of, 525. , development of, 594. , regions of, 22. Stichidium, 439, 448. Stigma, 12, 133. Stigmas, characters of, 128. Stigmata bicruria, 127. Stings, 66, 524. Stipels, 54, Stipitate, 101. Stipules. 51, 53. Stock, 36. Stomata, 580. , development of, 591. Straight embryo, 157. Striate, 40. Strictus, 40. Strobilus, 152. Structure of anthers, 541. of flowers, 86, 540. of leaves, 539. of ovules, 541. of petioles, 540. of roots, 533. of stems, 525. of thalamus, 542. Style, 12, 128. , characters of, 133. , structure of, 541. Stylospores, 464. Suberous layer, 524, 529. Submerged leaves, 65. Subrotuud, 58. Substitution, 88, 101. Subulate, 58, 120. Successive whorls, 48. Sugar, 404. , secretion of, 581. Superior, 98. ovary, 130. Superposition, 91, 94, 101. Suppression, 93. Supradecomposite, 63. Surfaces of leaves, 65. Survival, 163. Suspended ovule, 138. Suspensor, 626. Sutural dehiscence, 123, 142. Sutures of anther, 123. , dorsal, 129. , ventral, 129. Swarm-spores, 614. Syconus, 151. Symmetrical flower. 91. Sympetalous, 97 Sympode, 30, 82. Syncarpous fruits, 145. - pistil, 130. Syngenesious, 97, 126. Synonyms, 167. Synsepalous, 97. System, aerial, 514. , cellular, 514. , cortical, 514. , fibro-vascular, 515. , secretory, 515. System of Benthain and Hooker, 187. of Caruel, 190. of Braun, 188. of De Candolle, 186. of Endlicher, 186. of Jussieu, 185. of Lindley, 187- of Linneeus, 181. Systematic botany, 158. Systems, artificial, 180. , natural, 1 82. of classification, 180. Tabular cells, 478. Tannin, 582. Tap-root, 16. Teeth of calyx, 107. Tegmen, 137, 153. Tela contexta, 510. Temperature of plants, 647. Tendrils, 67, 657. Tension, 609. Teratology, 87. Terete, 40. Ternary compounds, 578. Ternate, 663. Ternato -pinnate, 64. Tertiary layers, 460. Testa, 130, 153. Tetradynamous, 124. Tetramerous flowers, 91. Tetraspores, 439, 447, 614. Texture of leaves, 65. Thalamifloral, 98. Thalamus, 99, 100, 542. , development of, 100. , structure of, 542. Thallophyta, 9, 411,435. , morphology of, 411. GENERAL AND GLOSS ART AL INDEX. 741 Thallophyta, reproduc- tion of, 411, 435. Thallus, 154, 409. Thorns, 68. Throat of calyx, 107. of corolla, 112. Thyrse (a form of pani- cled inflorescence in which the central stalks are longest). Tigellum (hypocotyledo- nary axis), 13, 156, 593. Tissue, conducting, 541. , felted, 510. , kinds of, 506. , vascular, 510. Tissues, 475. Tomentose, 65. Torus, see Thalamus. Transitional forms, 87. Transpiration, 567, 568. Triadelphous, 126. Triandrous, 124. Triangular, 40. Tribes, 439, 447. Trichogyne, 590, 593. Trichome, 17, 519. Trigonous, 40. Trimeroiis flowers, 91. Trimorphism, 636. Trioecious, 637. Tripinnate, 63. Tripinnatifld, 61. Tripinnatisect, 61. Triple-nerved, 55. Triquetrous, 40. Tristichous, 43. Trunk, 34. Tube of calyx, 107. of corolla, 112. of receptacle, 99. Tubers, stem-, 28. Tuberous roots, 17, 527. Tubular, 101, 105. Tufted, 47. Tunicated bulb, 26. Turbinate, 108. Turgescence, 609. Turio, 32. Twining, 40. Tyloses, 513. Typical flower, 91. Umbel, 79. Umbellule, 79. Umbilical cord, 137. Undulated, 59. Unguis, 109. Unijugate, 63. Unilocular anther, 123. ovary, 130. Union, 97. Unisexual, 93, 112. Urceolate, 108. Utricles, primordial, 495. Utriculus, 118. of Carex, 117. Uva, 150. Vacuoles, 496, 591. Vagina, 52. Vaginule of Mosses, 431. Valvate, 73, 105. eestivation, 105. Valves of fruits, 142. Valvular (sutural) dehi- scence of anther, 123. of fruits, 142. Varieties, 159. , names of, 168. , nature of, 159. Vasa propria, 512, 516. Vascular tissue, 476, 510. Vasculose, 492. Vegetation, physiology of, 542. , regions of, 675. , statistics of, 696. , zones of, 669. Vegetative multiplication, 613. Veins, 55. of leaves, 55, 540. Velamen radicum, 521. Venation of leaves, 55. Vernation, 72. Versatile anther, 121. Verticillaster, 84. Verticillate, 42. Vessels, 476. Vessels, annular, 512. , development of, 591. , laticiferous, 513. , moniliform, 510. , reticulated, 512. , scalariform, 512. , spiral, 510. , vesicular, 513. Vexillary aestivation, 105. Vexillum, 111. Villous, 65. Vinegar-plant, 552. Viscous, 66. Viscum, epidermis of, 521. Vitality of seeds and spores, 543. Volatile oils, 505, 581. Volva, 463. Volubilis, 40. Vorblatt, 51 . Water-culture, 557, Wax, excretion of, 582. Whorled, 42. Winged, 41. Wings, 111. Wood, 515. of Dicotyledons, 515, 529. Wood-region, 516. Woody fibre, 508. Xantho -protein, 500. Xerophiles, 661. Xylem, 517, 522. Yeast-plant, 551. Yew, wood-cells of, 490. Yucca, stem of, 527. Zones of vegetation, 668. Zoosporangia, 455. Zoospores, 438, 614. , development of, 584. , emission of, 438. , movement of, 552. Zygospore, 455, 585. Zygote, 459. THE END. PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. 14 DAY USE RETURN TO DESK FROM WHICH BORROWED This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. MAY 4 190f JUN 8 1961 LD 21-50m-6 ) '60 (B1321slO)476 BERKELEY LIBRARIES