THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES UNIVERSITY of CALIFORNT- ;''l i LOS ANGELES LIBRARY UNIVERSITY of CALIFORNIA AT LOS ANGELES L1BRAJRY SAMUEL W. JOHNSON, M. A. HOW CROPS GROW. A. TREATISE ON THE CHEMICAL COMPOSITION, STRUCTURE AND LIFE OF THE PLANT, FOB STUDENTS OF AGRICULTURE. 2. 2. / 3 -5 BY SAMUEL W. JOHNSON, M. A., PROFESSOR OF THEORETICAL AND AGRICULTURAL CHEMISTRY TS THE SHOT FIELD SCIENTIFIC SCHOOL OF YALE UNIVERSITY ; DIRECTOR O THE CONNECTICUT AGRICULTURAL EXPERIMENT STATION; MEMBER OF THE NATIONAL ACADEMY OF SCIENCES. StVISED AND ENLARGED EDITiqy. OEANGE JUDD COMPANY, 1911 Entered, according to Act of Congress, In the year 1890, by the ORANGE JTJDD COMPANY, in the Office of the Librarian of Congress, at Washington. e 7~^~~- r -^(tXfl------**J f -^ r i * , g. A, S J PREFACE. The original edition of this work, first published in 1868, was the result of studies undertaken in preparing instruction in Agricultural Chemistry which the Author has now been giving for three and thirty years. To- gether with the companion volume, "How Crops Feed," it was intended to present concisely but fully the then present state of Science regarding the Nutrition of the higher Plants and the relations of the Atmosphere, Water, and the Soil, to Agricultural Vegetation. Since its first appearance, our knowledge of the subject treated of in the present volume has largely participated in the remarkable advances which have marked all branehes of Science during the last twenty years and it has been the writers' endeavor in this revised edition to post the book to date as fully as possible without greatly enlarging its bulk or changing its essential character. In attempting to reach this result he has been doubly embarassed, first, by the great and rapidly increasing amount of recent publications in which the materials for revision must be sought, and, second, by the fact that official duties have allowed very insufficient time for a careful and compre- hensive study of the literature. In conclusion, it is hoped that while the limits of the book make necessary the omission of a multitude of interesting details, little has been overlooked that is of real importance to ;i fajr presentation of the subjects discussed. Ill TABLE OF CONTENTS. INTRODUCTION 1 DIVISION I. CHEMICAL COMPOSITION OF THE PLANT. CHAP. I. THE VOLATILE PART OF PLANTS 12 1. Distinctions and Definitions..- 12 2. Elements of the Volatile Part of Plants 14 63. Chemical Affinity 29 $4. Vegetable Organic Compounds or Proximate Elements 36 1. Water 37 2. Carbhydrates 39 3. Vegetable Acids 75 4. Fats S3 . Albuminoids and Ferments 87 6. Amides 114 7. Alkaloids 120 8. Phosphorized Substances 122 CHAP. II. THE ASH OF PLANTS 126 1. Ingredients of the Ash 126 Non-metallic Elements 127 Carbon and its Compounds 128 Sulphur and its Compounds 129 Phosphorus and its Compounds 132 Chlorine and its Compounds 132 Silicon and its Compounds 134 Metallic Elements 138 Potassium and its Compounds 138 Sodium and its Compounds 139 Calcium and its Compounds 139 Magnesium and its Compounds 14* Iron and its Compounds 141 Manganese and its Compounds 142' Salts 143 Carbonates 144 Sulphates 146 Phosphates 147 Chlorides 149 Nitrates 149 2. Quantity, Distribution, and Variations of the Ash 151 Table of Proportions of Ash In Vegetable Matter 152 3. Special Composition of the Ash of Agricultural Plants 161 1. Constant Ingredients 161 2. Uniform composition of normal specimens of given plants 161 Table of Ash-analyses 164 3. Composition of Different parts of Plant 171 4. Like composition of similar plants 173 6. Variability of ash of same species 174 6. What is normal composition of the ash of a plant? 177 7. To what extent is each ash-ingredient essential or accidental 18C Water-culture 180 Essential ash-ingredients 186 Is Sodium Essential to Agricultural Plants ? 186 Iron indispensable 192 Manganese unessential 193 Is Chlorine indispensable ? 194 Silica is not essential 197 Ash-ingredients taken up in excess 201 Disposition of superfluous matters 203 State of Ash-ingredients in plant 207 6 4. Functions of the Ash-ingredients 210 CHAP. III. 1. Quantitative Relations among the Ingredients of Plants 220 52. Composition of the plant in successive stages of growth 223 Composition and Growth of the Oat Plant 223 T VI TABLE OF CONTENTS. DIVISION II. THE STRUCTURE OP THE PLANT AND OFFICES OF ITS ORGANS. CHAP. I. GENERALITIES 241 Organism, Organs 242 CHAP. II. PRIMARY ELEMENTS OF ORGANIC STRUCTURE ...243 1. The Vegetable Cell 243 2. Vegetable Tissues 254 CHAP. III. VEGETATIVE ORGANS 256 1. The Root 256 Offices of Root 260 Apparent Search for Food 263 Contact of Roots with Soil 266 Absorption by Root 269 Soil Roots, Water Roots, Air Roots 273 2. The Stem .282 Buds 283 Layers, Tillering 286 Root-stocks '. 287 Tubers 288 Structure of the Stem... 289 Endogenous Plants 290 Exogenous Plants 296 Sieve-cells 303 3. Leaves 306 Leaf Pores 309 Exhalation of Water Vapor 311 Offices of Foliage 314 CHAP. IV. REPRODUCTIVE ORGANS 315 1. The Flower 316 Fertilization 319 Hybridizing 324 Species. Varieties 326 2. Fruit 330 Seed 332 Embryo 333 3. Vitality of -seeds and their influence on the Plants they produce 335 Duration of Vitality 335 Use of old and unripe seeds 338 Density of seeds 339 Absolute weight of seeds 340 Signs of Excellence 345 Ancestry. Race- vigor 346 DIVISION III. LIFE OF THE PLANT. CHAP. 1. GERMINATION 349 1. Introductory , 349 2. Phenomena of Germination 350 3. Conditions of Germination 351 Proper Depth of Sowing 355 4. Chemical Physiology of Germination 357 Chemistry of Malt 358 CHAP. II. 1. Food of the Plant when independent of the Seed 366 2. The Juices of the Plant. Their Nature and Movements369 Flow of Sap 370 Composition of Sap 376 Kinds of Sap. 378 Motion of Nutrient Matters 379 3. Causes of Motion of the Juices 385 Porosity of Tissues 385 Imbibition 386 Liquid Diffusion 390 Osmose or Membrane Diffusion 393 Root Action ... 399 Selective Power of Plant 401 4. Mechanical effects of Osmose 406 APPENDIX. TABLE. Composition of Agricultural Products 409 HOW CROPS GROW. 2.2/33 INTRODUCTION. The object of agriculture is the production of certain plants and certain animals which are employed to feed, clothe and otherwise serve the human race. The first aim, in all cases, is the production of plants. Nature has made the most extensive provision for the spontaneous growth of an immense variety of vegetation ; but in those climates where civilization most certainly attains its fullest development, man is obliged to employ art to provide himself with the kinds and quantities of vegetable produce which his necessities or luxuries de- mand. In this defect, or, rather, neglect of nature, ag- riculture has its origin. The art of agriculture consists in certain practices and operations which have gradually grown out of an obser- vation and imitation of the best efforts of nature, or have been hit upon accidentally, or, finally, have been deduced from theory. The science of agriculture is the rational theory and systematic exposition of the successful art. Strictly considered, the art and science of agriculture are of equal age, and have grown together from the ear- 2 HOW CROPS GROW. liest times. Those who first cultivated the soil by dig- ging, planting, manuring and irrigating, had their suffi- cient reason for every step. In all cases, thought goes before work, and the intelligent workman always has a theory upon which his practice is planned. No farm was ever conducted without physiology, chemistry, and physics, any more than an aqueduct or a railway was ever built without mathematics and mechanics. Every suc- cessful farmer is, to some extent, a scientific man. Let him throw away the knowledge of facts and the knowl- edge of principles which constitute his science, and he has lost the elements of his success. The farmer without his reasons, his theory, his science, can have no plan; and these wanting, agriculture would be as complete a failure with him as it would be with a man of mere science, destitute of manual, financial and executive skill. Other qualifications being equal, the more advanced and complete the theory of which the farmer is the mas- ter, the more successful must be his farming. The more he knows, the more he can do. The more deeply, com- prehensively, and clearly he can think, the more econ- omically and advantageously can he work. That there is any opposition or conflict between science and art, between theory and practice, is a delusive error. They are, as they ever have been and ever must be, in the fullest harmony. If they appear to jar or stand in con- tradiction, it is because we have something false or incom- plete in what we call our science or our art ; or else we do not perceive correctly, but are misled by the narrowness and aberrations of our vision. It is often said of a ma- chine, that it was good in theory, but failed in practice. This is as untrue as untrue can be. If a machine has failed in practice, it is because it was imperfect in theory. It should be said of such a failure the machine was good, judged by the best theory known to its inventor, but its incapacity to work demonstrates that the theory had a flaw* ttftBODUCTIOK. 3 But, although art and science are thus inseparable, it must not be forgotten that their growth is not altogether parallel. There are facts in art for which science can, as yet, furnish no adequate explanation. Art, though no older than science, grew at first more rapidly in vigor and in stature. Agriculture was practiced hundreds and thousands of years ago, with a success that does not com- pare unfavorably with ours. Nearly all the essential points of modern cultivation were regarded by the Ro- mans before the Christian era. The annals of the Chi- nese show that their wonderful skill and knowledge were in use at a vastly earlier date. So much of science as can be attained through man's unaided senses, reached considerable perfection early in the world's history. But that part of science which re- lates to things invisible to the unassisted eye, could not be developed until the telescope and the microscope had been invented, until the increasing experience of man and his improved art had created and made cheap the other inventions by whose aid the mind can penetrate the veil of nature. Art, guided at first by a very crude and im- perfectly-developed science, has, within a comparatively recent period, multiplied those instruments and means of research whereby science has expanded to her present proportions. The progress of agriculture is the joint work of theory and practice. In many departments great advances have been made during the last hundred years ; especially is this true in all that relates to implements and machines, and to the improvement of domestic animals. It is, however, in just these departments that an improved theory has had sway. More recent is the development of agriculture in its chemical and physiological aspects. In these directions the present century, or we might almost say the last fifty years, has seen more accomplished than all previous time. 4 HOW CROPS GEOW. The first book in the English language on the subjects which occupy a good part of the following pages, was written by a Scotch nobleman, the Earl of Dundonald, and was published at London in 1795. It is entitled: "A Treatise showing the Intimate Connection that sub- sists between Agriculture and Chemistry." The learned Earl, in his Introduction, remarked that " the slow pro- gress which agriculture has hitherto made as a science is to be ascribed to a want of education on the part of the cultivators of the soil, and the want of knowledge in such authors as have written on agriculture of the intimate connection that subsists between the science and that of chemistry. Indeed, there is no operation or process, not merely mechanical, that does not depend on chemistry, which is defined to be a knowledge of the properties of bodies, and of the effects resulting from their different combinations. " Earl Dundonald could not fail to see that chemistry was ere long to open a splendid future for the ancient art that always had been and always is to be the prime support of the nations. But when he wrote, how feeble was the light that chemistry could throw upon the fundamental questions of agricultural science ! The chemical nature of atmospheric air was then a discovery of barely twenty years' standing. The composition of water had been known but twelve years. The only ac- count of the composition of plants that Earl Dundonald could give was the following: "Vegetables consist of mucilaginous matter, resinous matter, matter analogous to that of animals, and some proportion of oil. * * Besides these, vegetables contain earthy matters, formerly held in solution in the newly-taken-in juices of the growing vegetable." He further explains by mentioning on subsequent pages that starch belongs to the mucil- aginous matters, and that, on analysis by fire, vegetables yield soluble alkaline salts and insoluble phosphate of lime. But these salts, he held, were formed in the pro* INTRODUCTIOH. 5 cess of burning, their lime excepted, and the fact of their being taken from the soil and constituting the indispen- sable food of plants, his Lordship was unacquainted with. The gist of agricultural chemistry with him was, that plants are " composed of gases with a small proportion of calcareous matter;" for " although this discovery may appear to be of small moment to the practical farmer, yet it is well deserving of his attention and notice, as it throws great light on the nature and food of vegetables." The fact being then known that plants absorb carbonic acid from the air, and employ its carbon in their growth, the theory was held that fertilizers operate by promoting the conversion of the organic matter of the soil or of composts into gases, or into soluble humus, which were considered to be the food of plants. The first accurate analysis of a vegetable substance was not accomplished until fifteen years after the publication of Dundonald's Treatise, and another like period passed before the means of rapidly 'multiplying good analyses had been worked out by Liebig. So late as 1838, the Got- tingen Academy offered a prize for a satisfactory solution of the then vexed question whether the ingredients of ashes are essential to vegetable growth. It is, in fact, during the last fifty years that agricultural chemistry has come to rest on sure foundations. Our knowledge of the structure and physiology of plants is of like recent devel- opment. What immense practical benefit the farmer has gathered from this advance of science ! Chemistry has ascertained what vegetation absolutely demands for its growth, and points out a multitude of sources whence the requisite materials for crops can be derived. Cato and Columella knew indeed that ashes, bones, bird- dung and green manuring, as well as drainage and aera- tion of the soil, were good for crops ; but that carbonic acid, potash, phosphate of lime, and compounds of nitro- gen are the chief pabulum of vegetation, they did not HOW CROPS GROW. know. They did not know that the atmosphere dissolves the rocks, and converts inert stone into nutritive soil. These grand principles, understood in many of their de- tails, are an inestimable boon to agriculture, and intelli- gent farmers have not been slow to apply them in prac- tice. The vast trade in phosphatic and Peruvian guano, and in nitrate of soda ; the great manufactures of oil of vitriol, of superphosphate of lime, of fish fertilizers ; and the mining of fossil bones and of potash salts, are indus- tries largely or entirely based upon and controlled by chemistry in the service of agriculture. Every day is now the witness of new advances. The means of investigation, which, in the hands of the scien- tific experimenter, have created within the writer's mem- ory such arts as photography and electro-metallurgy, and have produced the steam-engine, the telegraph, the tele- phone and the electric light, are working and shall ever- more continue to work progress in the art of agriculture. This improvement will not consist so much in any re- markable discoveries that shall enable us to "grow two blades of grass where but one grew before;" but in the gradual disclosure of the reasons of that which we have long known, or believed we knew ; in the clear separa- tion of the true from the seemingly true, and in the ex- change of a wearying uncertainty for settled and positive knowledge. It is the boast of some who affect to glory in the suf- ficiency of practice and decry theory, that the former is based upon experience, which is the only safe guide. But this is a one-sided view of the matter. Theory is also based upon experience, if it be worth the name. The fancies of an ignorant and undisciplined mind are not theory as that term is properly understood. Theory, in the strict scientific sense, is always a deduction from, facts, and the best deduction of which the stock of facts in our possession admits. It is therefore also the inter* INTKODUCTION. 7 pretation of facts. It is the expression of the ideas which facts awaken when submitted to a fertile imagination and well-balanced judgment. A scientific theory is intended for the nearest possible approach to the truth. Theory is confessedly imperfect, because our knowledge of facts is incomplete, our mental insight weak, and our judg- ment fallible. But the scientific theory which is framed by the contributions of a multitude of earnest thinkers and workers, among whom are likely to be the most gifted intellects and most skillful hands, is, in these days, to a great extent worthy of the Divine truth in nature, of which it is the completest human conception and ex- pression. Science employs, in effecting its progress, essentially the same methods that are used by merely practical men. Its success is commonly more rapid and brilliant, because its instruments of observation are finer and more skill- fully handled ; because it experiments more industriously and variedly, thus commanding a wider and more fruit- ful experience ; because it usually brings a more culti- vated imagination and a more disciplined judgment to bear upon its work. The devotion of a life to discovery or invention is sure to yield greater results than a desul- tory application made in the intervals of other absorbing pursuits. It is then for the interest of the farmer to avail himself of the labors of the man of science, when the latter is willing to inform himself in the details of practice, so as rightly to comprehend the questions which press for a solution. Agricultural science, in its widest scope, comprehends a vast range of subjects. It includes something from nearly every department of human learning. The natu- ral sciences of geology, meteorology, mechanics, physics, chemistry, botany, zoology and physiology, are most in- timately related to it. It is not less concerned with so- cial and political economy. In this treatise it will not be 8 HOW CROPS GROW. attempted to touch, much less cover, all this ground, but some account will be given of certain subjects whose un- derstanding will be of the most direct service to the agri- culturist. The Theory of Agriculture, as founded on chemical, physical and physiological science, in so far as it relates to the Chemical Composition, the Structure and the Life of the Plant, is the topic of this volume. Some preliminary propositions and definitions may be serviceable to the reader. Science deals with Matter and Force. Matter is that which has weight and bulk. Force is the cause of changes in matter it is appre- ciable only by its effects upon matter. Force resides in and is inseparable from matter. Force manifests itself in motion and change. All matter is perpetually animated by force is there- fore never at rest. What we call rest in matter is simply motion too fine for our perceptions. The different kinds of matter known to science have been resolved into some seventy chemical elements or sim- ple substances. The elements of chemistry are forms of matter which have thus far resisted all attempts at their simplification or decomposition. In ordinary life we commonly encounter but twelve kinds of matter in their elementary state, viz. : Oxygen, Carbon, Mercury, Tin, Nitrogen, Iron, Copper, Silver, Sulphur, Zinc, Lead, Gold. The numberless other substances with which we arc familiar, are mostly compounds of the above, or of twelve other elements, viz. : Hydrogen, Silicon, Calcium, Manganese, Phosphorus, Potassium, Magnesium, Chromium, Chlorine, Sodium, Aluminum, Nickelt INTRODUCTION. So far as human agency goes, these chemical elements are indestructible as to quantity, and not convertible one into another. We distinguish various natural manifestations of force which, acting on or through matter, produce all material phenomena. In the subjoined scheme the recognized forces are to some extent classified and defined, in a man- ner that may prove useful to the reader. - Repulsive \ Att ctive distances I Act only at insensible distances Attractive HEA? } Radiant ELECTRICITY inductive MAGNETISM j" 3 GRAVITATION Cosmical Physical COHESION CRYSTALLIZATION ADHESION SOLUTION ^-Molecular OSMOSE AFFINITY Atomic Chemical VITALITY Organic Biological Within human experience the different kinds of force are mostly convertible each into the others, and must therefore be regarded as fundamentally one and the same. Force, like matter, is indestructible. Force acting on a body may either increase its Kinetic Energy, or be stored up in it as Potential Energy. Kinetic (or ac- tual) energy is the energy of a moving body. Potential (or possible) energy is the energy which a body may be able to exert because of its state or position. A falling stone or running clock gives out actual energy. The stone while being raised, or the clock while winding, ac- quires and stores potential energy. In a similar manner kinetic solar energy, reaching the earth as light, heat and chemical force, not only sets in operation the visible ac- tivities of plants, but accumulates in them a store of po- tential energy which, when they serve as food or fuel, re- appears as kinetic energy in the forms of animal heat, muscular and uervous activity, or as fire and light. The sciences that more immediately relate to agricult- ure we Physics, Chemistry and Biology. 10 HOW CROPS GROW. Physics, or "natural philosophy," is the science which considers the general properties of matter and such phenomena as are not accompanied by essential change in its obvious qualities. All the forces in the preceding scheme, save the last two, manifest themselves through matter without destroying or masking the matter itself. Iron may be hot, luminous, or magnetic, may fall to the ground, be melted, welded, and crystallized ; but it re- mains iron, and is at once recognized as such. The forces whose play does not disturb the evident characters of sub- stances are physical. Chemistry is the science which studies the proper- ties peculiar to the various kinds of matter, and those phenomena which are accompanied by a fundamental change in the matter acted on. Iron rusts, wood burns, and both lose all the external characters that serve for their identification. They are, in fact, converted into other substances. Chemical attraction, affinity, or chem- ism, as it is variously termed, unites two or more ele- ments into compounds, unites compounds together into more complex compounds ; and, under the influence of heat, light, and other agencies, is annulled or overcome, so that compounds resolve themselves into simpler com- binations or into their elements. Chemistry is the science of composition and decomposition ; it considers the laws and results of affinity. Biology, or physiology, unfolds the laws of the propagation, development, sustenance, and death of liv- ing organisms, both plants and animals. When we assert that the object of agriculture is to de- velop from the soil the greatest possible amount of cer- tain kinds of vegetable and animal produce at the least cost, we suggest the topics which are most important for the agriculturist to understand. The farmer deals with the plant, with the soil, with manures, These stand in close relation to each other, INTRODUCTION. 11 and to the atmosphere which constantly surrounds and acts upon them. How the plant grows, the conditions under which it flourishes or suffers detriment, the ma- terials of which it is made, the mode of its construction and organization, how it feeds upon the soil and air, how it serves as food to animals, how the air, soil, plant, and animal stand rel?ted to each other in a per- petual round of the most beautiful and wonderful trans- formations, these are some of the grand questions that come before us ; and they are net less interesting to the philosopher or man of culture, than important to the farmer who depends upon their practical solution for his comfort ; or to the statesman, who regards them in their bearings upo^ *he weightiest of political considerations. DIVISION 1. CHEMICAL COMPOSITION OF THE PLANT. CHAPTER 1. THE VOLATILE PART OF PLANTS. V 1* DISTINCTIONS AND DEFINITIONS. OKGANIC AND INORGANIC MATTER. All matter may be divided into two great classes Organic and Inorganic. Organic matter is the product of growth, or of vital organization, whether vegetable or animal. It is mostly combustible, i. e., it may be easily set on fire, and burns away into invisible gases. Organic matter either itself constitutes the organs of life and growth, and has a pecu- liarly organized structure, inimitable by art, is made up of cells, tubes or fibres (wood and flesh) ; or else is a mere result or product of the vital processes, and desti- tute of this structure (sugar and fat). All matter which is not a part or product of a living organism is inorganic or mineral matter (rocks, soils, water, and air). Most of the naturally-occurring forms of inorganic matter which directly concern agricultural chemistry are incombustible, and destitute of anything like organic structure. By the processes of combustion and decay, organic matter is disorganized or converted into inorganic matter, while, on the contrary, by vegetable growth inorganic matter is organized, and becomes organic,. 13 14 HOW CROPS GROW. Organic matters are in general characterized by com- plexity of constitution, and are exceedingly numerous and various ; while inorganic bodies are of simpler com- position, and comparatively few in number. VOLATILE AND FIXED MATTER. All plants and ani- mals, taken as a whole, and all of their organs, consist of a volatile and fixed part, which may be separated by burning ; the former usually by far the larger share passing into and mingling with the air as invisible gases ; the latter forming, in general, but from one to five per cent, of the whole remaining as ashes. EXPERIMENT 1. A splinter of wood heated in the flame of a lamp takes fire, burns, and yields volatile matter, which consumes with flame, and ashes, which are the only visible residue of the combustion. Many organic bodies, products of life, but not essential vital organs, as sugar, citric acid, etc., are completely volatile when in a state of purity, and leave no ash. USE OF THE TERMS ORGANIC AND INORGANIC. It is usual among agricultural writers to confine the term or- ganic to the volatile or destructible portion of vegetable and animal bodies, and to designate their ash-ingredients as inorganic matter. This is not an entirely accurate distinction. What is found in the ashes of a tree or of a seed, in so far as it was an essential part of the organism, was as truly organic as the volatile portion, and, by sub- mitting organic bodies to fire, they may be entirely con- verted into inorganic matter, the volatile as well as the fixed parts. ULTIMATE ELEMENTS THAT CONSTITUTE THE PLANT. Chemistry has demonstrated that the volatile and de- structible part of organic bodies is chiefly made up of four substances, viz. : carbon, oxygen, hydrogen, and nitrogen, and contains two other elements in lesser quantity, viz. : sulphur and phosphorus. In the ash we may find phos- phorus, sulphur, silicon, chlorine, potassium, sodium, cal- TEE VOLATILE PART OP PLAKTS. 15 cium, magnesium, iron, and manganese, as well as oxy- gen, carbon, and nitrogen.* These fourteen bodies are elements, which means, in chemical language, that they cannot be resolved into other substances. All the varieties of vegetable and ani- mal matter are compounds, are composed of and may be resolved into these elements. The above-named elements being essential to the or- ganism of every plant and animal, it is of the highest im- portance to make a minute study of their properties, 2. ELEMENTS OF THE VOLATILE PART OF PLANTS. For the sake of convenience we shall first consider the elements which constitute the combustible part of plants, viz. : Carbon, Nitrogen, Sulphur, Oxygen, Hydrogen, Phosphorus. The elements which belong exclusively to the ash will be noticed in a subsequent chapter. Carbon, in the free state, is a solid. "We are familiar with it in several forms, as lamp-black, charcoal, black- lead, and diamond. Notwithstanding the substances just named present great diversities of appearance and physical characters, they are identical in a certain chem- ical sense, as by burning they all yield the same product, viz. : carbonic acid gas, also called carbon dioxide. That carbon constitutes a large part of plants is evi- dent from the fact that it remains in a tolerably pure state after the incomplete burning of wood, as is illus- trated in the preparation of charcoal. * Rarely, or to a slight extent, lithium, rubidium, iodine, bromine, fluorine, barium, copper, zinc, titanium, and boron. 16 SOW CEOPS GROW. EXP. 1. If a splinter of dry pine wood be set on fire and the burning end be gradually passed into the mouth of a narrow tube (see figure 1), whereby the supply of air is cut off, or if it be thrust into sand, the burning is incomplete, and a stick of charcoal re- mains. Carbonization and Charring are terms used to express the blackening of organic bodies by heat, and are due to the separation of carbon in the free or uncombined state. The presence of carbon in animal matters also is shown by subjecting them to incomplete com- bustion. EXP. 3. Hold a knife-blade in the flame of a tallow candle ; the full access of air is thus prevented, a portion of carbon . - escapes combustion, and is deposited on the blade in the form * " of lamp-black. Oil of turpentine and petroleum (kerosene) contain so much carbon that a portion ordinarily escapes in the free state as smoke, when they are set on fire. When bones are strongly heated in closely-covered iron pots, until they cease yielding any vapors, there remains in the vessels a mixture of impure carbon with the earthy matter (phosphate of lime) of the bones, which is largely used in the arts, chiefly for refining sugar, but also in the manufacture of fertilizers under the name of animal char- coal, or bone-black. Lignite, bituminous coal, anthracite, coke the porous, hard, and lustrous mass left when bituminous coal is heated with a limited access of air, and the metallic ap- pearing gas-carbon that is found lining the iron cylinders in which illuminating coal-gas is prepared, all consist largely or chiefly of carbon. They usually contain more or less incombustible matters, as well as a little oxygen, hydrogen, nitrogen, and sulphur. The different forms of carbon possess a greater or less degree of porosity and hardness, according to their origin and the temperature at which they are prepared. Carbon, in most of its forms, is extremely indestructi- THE VOLATILE PAET OF PLANTS. 17 ble under ordinary circumstances. Hence stakes and fence posts, if charred before setting in the ground, last much longer than when this treatment is neglected. The porous varieties of carbon, especially wood char- coal and bone-black, have a remarkable power of absorb- ing gases and coloring matters, which is taken advantage of in the refining of sugar. They also destroy noisome odors, and are used for purposes of disinfection. Carbon is the characteristic ingredient of all organic compounds. There is no single substance that is the ex- clusive result of vital organization, no ingredient of the animal or vegetable produced by their growth, that does not contain this element. Oxygen. Carbon is a solid, and is recognized by our senses of sight and feeling. Oxygen, on the other hand, is an air or gas, invisible, odorless, tasteless, and not dis- tinguishable in any way from ordinary air by the unas- sisted senses. It exists in the free (uncombined) state in the atmos- phere we breathe, but there is no means of obtaining it pure except from some of its compounds. Many metals unite readily with oxygen, forming compounds (oxides) which by heat separate again into their ingredients, and thus furnish the means of procuring pure oxygen. Iron and copper, when strongly heated and exposed to the air, acquire oxygen, but from the oxides of these metals (forge cinder, copper scale) it is not possible to separate pure oxygen. If, however, the metal mercury (quicksil- ver) be kept for a long time near the temperature at which it boils, it is slowly converted into a red powder (red precipitate, red oxide of mercury, or mercuric ox- ide), which on being more strongly heated is decomposed, yielding metallic mercury and gaseous oxygen in a pure state. The substance usually employed as the most convenient source of oxygen gas is the white salt called potassium 2 18 HOW CHOPS GROW. chlorate. Exposed to heat, this body melts, and present* ly evolves oxygen in great abundance. EXP. 4. The following figure illustrates the apparatus employed for preparing and collecting this gas. A tube of difficultly fusible glass, 8 inches long and J inch wide, con- tains the red oxide of mercury or potassium chlorate.* To its mouth is connected, air-tight, by a cork, a narrow tube, the free extremity of which passes under the shelf of a tub nearly filled with water. The shelf has, beneath, a funnel-shaped cavity opening above by a narrow orifice, over which a bottle filled with water is inverted. Heat being Pig. 2. applied to the wide tube, the common air it contains is first expelled, and presently, oxygen bubbles rapidly into the bottle and displaces the water. When the bottle is full, it may be corked and set aside, and its place supplied by another. Fill four pint bottles with the gas, and set them aside with their mouths in tumblers of water. From one ounce of potassium chlorate about a gallon of oxygen gas may be thus obtained, which is not quite pure at first, but becomes nearly so on standing over water for some hours. When the escape of gas becomes slow and cannot be quickened by increased heat, remove the delivery- tube from the water, to prevent the latter receding and breaking the apparatus. As this gas makes no peculiar impressions on the senses, * The potassium chlorate is best mixed with about one-quarter its weight of powdered black oxide of manganese, as this facilitates the preparation, and renders the heat of a common alcohol lamp sufficient* 10 we employ its behavior toward other bodies for its recog- nition. EXP. 5. Place a burning splinter of wood In a vessel of oxygen (lifted for that purpose, mouth upward, from the water). The flame is at once greatly increased in brilliancy. Now remove the splinter from the bottle, blow out the flame, and thrust the still glowing point into the oxygen. It is instantly relighted. The experiment may be repeated many times. This is the usual test for oxygen gas. Combustion. When the chemical union of two bodies takes place with such energy as to produce visible phe- nomena of fire or flame, the process is called combustion. Bodies that burn are combustibles, and the gas in which a substance burns is called a supporter of combustion. Oxygen is the grand supporter of combustion, and nearly all cases of burning met with in ordinary experi- ence are instances of chemical union between the oxygen of the atmosphere and some other body or bodies. The rapidity or intensity of combustion depends upon the quantities of oxygen and of the combustible that unite within a given time. Forcing a stream of air into a fire increases the supply of oxygen and excites a more vigorous combustion, whether it be done by a bellows or result from ordinary draught. Oxygen exists in our atmosphere to the extent of about one-fifth of the bulk of the latter. When a burning body is brought into unmixed oxygen, its combustion is, of course, more rapid than in ordinary air, four-fifths of which is a gas, presently to be noticed, that is compara- tively indifferent in its chemical affinities toward most bodies. In the air a piece of burning charcoal soon goes out ; but if plunged into oxygen, it burns with great rapidity and brilliancy. EXP. 6. Attach a slender bit of charcoal to one end of a sharpened wire that is passed through a wide cork or card ; heat the charcoal to redness in the flame of a lamp, and then insert it into a bottle of oxy- gen, Fig. 3. When the combustion has declined, a suitable test applied 20 HOW CEOPS GROW. to the air of the bottle will demonstrate that another invisible gas has taken the place of the oxygen. Such a test is lime-water.* On pouring some of this into the bottle and agitating vigorously, the previously clear liquid becomes milky, and, on standing, a white deposit, or precipitate, as the chemist terms it, gathers at the bottom of the vessel. Carbon, by thus uniting to oxygen, yields carbonic acid gas, which in its turn combines with lime, producing carbonate of lime. These substances will be further noticed in a subsequent chapter. Metallic iron is incombustible in the at- mosphere under ordinary circumstances, but 3 ' if heated to redness and brought into pure oxygen gas, it burns as readily as wood burns in the air. EXP. 7. Provide a thin knitting-needle, heat one end red hot, and sharpen it by means of a file. Thrust the point thus made into a splinter of wood (a bit of the stick of a match, J inch long) ; pass the other end of the needle through a wide, flat cork for a support ; set the wood on fire, and immerse the needle in a bottle of oxygen, Fig. 4. After the wood consumes, the iron itself takes fire and burns with vivid scintillations. It is converted into two distinct oxides of iron, of which one, ferric oxide, will be found as a yellowish-red coating on the sides of the bottle ; the other, magnetic oxide, will fuse to black, brittle globules, which falling, often melt quite into the glass. Fig. 4. The only essential difference between these and ordi- nary cases of combustion is the intensity with which the process goes on, due to the more rapid access of oxygen to the combustible. Many bodies unite slowly with oxygen, oxidize, as it is termed, without these phenomena of light and intense heat which accompany combustion. Thus iron rusts, lead tarnishes, wood decays. All these processes are cases of oxidation, and cannot go on in the absence of oxygen. Since the action of oxygen on wood and other organic matters at common temperatures appears to be analogous * To prepare lime-water, put a piece of unslaked lime, as large as a chestnut, into a pint of water, and after it lias fallen to powder, agitate the whole for a few minutes in a well-stoppered bottle. On standing, the excess of lime will settle, and the perfectly clear liquid above it is ready for use. THE VOLATILE PART OF PLANTS. 21 in a chemical sense to actual burning, Liebig has pro- posed the term eremacausis (slow burning), to designate the chemical process of oxidation which takes place in decay, and which is concerned in many transformations, as in the making of vinegar and the formation of salt- peter.* Oxygen is necessary to organic life. The act of breath- ing introduces it into the lungs and blood of animals, where it aids the important office of respiration. Ani- mals, and plants as well, speedily perish if deprived of free oxygen, which has therefore been called vital air. Oxygen has a nearly universal tendency to combine with other substances, and form with them new com- pounds. With carbon, as we have seen, it forms carbonic acid gas or carbon dioxide. With iron it unites in vari- ous proportions, giving origin to several distinct oxides. In decay, putrefaction, fermentation, and respiration, numberless new products are formed, the results of its chemical affinities. Oxygen is estimated to be the most abundant body in nature. In the free State, but mixed with other gases, it constitutes one-fifth of the bulk of the atmosphere. In chemical union with other bodies, it forms eight-ninths of 'the weight of all the water of the globe, and one-third of its solid crust, its soils and rocks, as well as of all the plants and animals which exist upon it. In fact, tli ere are but few compound substances occurring in or- dinary experience into which oxygen does not enter as a necessary ingredient. Nitrogen. This body is the other chief constituent of the atmosphere, of which it makes up about four-fifths the bulk, and in which its office would appear to be * Recent investigation has demonstrated that the oxidations which Liebig classed under the term eremacausis, are for the most part strict- ly dependent on the vital processes of extremely minute organisms, which are in general characterized by the terms microbes or micro- demes, and are more specifically designated bacteria, i. e., "rod-shaped animalcules or plautlets." 22 fiow CROPS GROW. mainly that of diluting and tempering the affinities of oxygen. Indirectly, however, it serves other most im- portant uses, as will presently be seen. For the preparation of nitrogen we have only to remove the oxygen from a portion of atmospheric air. This may be accomplished more or less perfectly by a variety of methods. "We have just learned that the process of burn- ing is a chemical union of oxygen with the combustible. If, now, we can find a body which is very combustible and one which at the same time yields by union with ox- ygen a product that may be readily removed from the air in which it is formed, the preparation of nitrogen from ordinary air becomes easy. Such a body is phosphorus, a substance to be noticed in some detail presently. EXP. 8. The bottom of a dinner-plate is covered half an Inch deep with water ; a bit of chalk hollowed out into a little cup is floated on the water by means of a large flat cork or a piece of wood ; into this cup a morsel of dry phosphorus as large as a pepper- corn is placed, which is then set on fire and covered by a capacious glass bottle or bell-jar. The phosphorus burns at first with a vivid light, which is presently ob- scured by a cloud of snow-like phosphoric acid. The combustion goes on, however, until nearly all the oxy- gen is removed from the included air. The air is at first expanded by the heat of the flame, and a portion of it escapes from the vessel ; afterward it diminishes in volume as its oxygen is removed, so that it is need- ful to pour water on the plate to prevent the external air from passing into the vessel. After some time the white fume will entirely fall, and be absorbed by the water, leaving the inclosed nitro- gen quite clear. EXP. 9. Another instructive method of preparing nitrogen is the fol- lowing: A handful of green vitriol (protosulphate of iron or ferrous sulphate) is dissolved in half a pint of water, the solution is put into a quart bottle, a gill of ammonia-water or fresh potash-lye is added, the bottle stoppered, and the mixture vigorously agitated for some minutes ; the stopper is then lifted, to allow fresh air to enter, and the whole is again agitated as before. This is repeated occasionally for half an hour or more, until no further absorption takes place, when nearly pure nitrogen remains in the bottle. Free nitrogen, under ordinary circumstances, mani- fests no active properties, but is best characterized by its chemical indifference to most other bodies. That it is THE VOLATILE PAET OF PLANTS. 23 incapable of supporting combustion is proved by the first method we have instanced for its preparation. EXP. 10. A burning splinter is immersed in the bottle containing the nitrogen prepared by the second method, Exp. 9; the flame immediate- ly goes out. Nitrogen cannot maintain respiration, so that animals perish if confined in it. Vegetation also dies in an at- mosphere of this gas. For this reason it was formerly called .Azote (against life). In general it is difficult to effect direct union of nitrogen with other bodies, but at a high temperature, in presence of alkalies, it unites with carbon, forming cyanides. The atmosphere is the great store and source of nitro- gen in nature. In the mineral kingdom, especially in soils, it occurs in small relative proportion, but in large aggregate quantity as an ingredient of saltpeter and other nitrates, and of ammonia. It is a constant constituent of all plants, and in the animal it is a never-absent com- ponent of the working tissues, the muscles, tendons and nerves, and is hence an indispensable ingredient of food. Hydrogen. Water, which is so abundant in nature, and so essential to organic existence, is a compound of two elements, viz. : oxygen, that has already been consid- ered, and hydrogen, which we now come to notice. Hydrogen, like oxygen, is a gas, destitute, when pure, of either odor, taste, or color. It does not occur nat- urally in the free state, except in small quantity in the emanations from boiling springs and volcanoes. Its most simple preparation consists in abstracting oxygen from water by means of agents which have no special affinity for hydrogen, and therefore leave it uncombined. Sodium, a metal familiar to the chemist, has such an attraction for oxygen that it decomposes water with great rapidity. Exp. 11. Hydrogen is therefore readily procured by inverting a bot- tle full of water in a bowl, and inserting into it a bit of sodium as large *s a pea. The sodium should first be wiped tree from the naphtha in 24 HOW CROPS GROW. which it is kept, and then be wrapped tightly in several folds of paper. On bringing it, thus prepared, under the mouth of the bottle, it floats upward, and when the water penetrates the paper, an abundant escape of gas occurs. Metallic iron, when at a red heat, rapidly decomposes water, uniting with oxygen and setting hydrogen free, as may be shown by passing steam from boiling water through a gun-barrel filled with iron-turnings and heated to bright redness. Certain acids which contain hydro- gen are decomposed by iron, zinc, and some other metals, their hydrogen being separated as gas, while the metal takes the place of the hydrogen with formation of a salt. Hydrochloric acid (formerly called muriatic acid) is a compound of hydrogen with chlorine, and may accord- ingly be termed hydrogen chloride. When this acid is poured upon zinc the latter takes the chlorine, forming zinc chloride, and hydrogen escapes as gas. Chemists represent such changes by the use of symbols (first letters of the names of chemical elements), as follows : H. 1^1 i rr n VT ^-'1 I ** *-vi HC1 + Zn_Zn cl + H or 2 (H Cl) -\- Zn = Zn C1 2 + H, EXP. 12. Into a bottle fitted with cork, funnel, and delivery tubes (Fig. 6) an ounce of iron tacks or zinc clippings is introduced, a gill of water is poured upon them, and lastly an ounce of hydro- chloric acid is added. A brisk effervescence shortly com- mences, owing to the escape of nearly pure hydrogen gas, which may be collected in a bottle filled with water as di- rected for oxygen. The first portions that pass over are mixed with air, and should be rejected, as the mixture Is dan- gerously explosive. One of the most strik- ing properties of free hy- Fig. 6. flrogen is its levity. It is the lightest body in nature THE VOLATILE PART OF PLANTS. fhat has been weighed, being fourteen and a half times lighter than common air. It is hence )used in filling balloons. Another property is its combustibility ; it inflames on contact with a lighted taper, and burns with a flame that is intensely hot, though scarcely luminous if the gas be pure. Finally, it is itself incapable of supporting the com- bustion of a taper. Exp. 13. All these characters may be shown by the following single experiment. A bottle full of hydrogen is lifted from the water over which it has been collected, and a taper attached to a bent wire, Fig. 7, is brought to its mouth. At first a slight explosion is heard from the sudden burning of a mixture of the gas with air that forms at the mouth of the vessel ; then the gas is seen burning on its lower surface with a pale flame. If now the taper be passed into the bottle it will be extin- guished; on lowering it again, it will be relighted by the burning gas; finally, if the bottle be suddenly turned mouth upwards, the light hy drogen rises in a sheet of flame. In the above experiment, the hydrogen burns only where it is in contact with atmospheric oxygen ; the pro- duct of the combustion is an oxide of hydrogen, the uni- versally diffused compound, water. The conditions of the last experiment do not permit the collection or iden- tification of this water ; its production can, however, readily be demonstrated. EXP. 14. The arrangement shown in Fig. 8 may be employed to exhibit Fig. a the formation of water by the burning of hydrogen. Hydrogen gas is generated from zinc and dilute acid in the two-necked bottle. Thus 26 HOW CHOPS GEOW. produced, it is mingled with spray, to remove which it is made to stream through a tube loosely filled with cotton. After air has been entirely displaced from the apparatus, the gas is ignited at the up- curved end of the narrow tube, and a clean bell-glass is supported over the flame. Water collects at once, as dew, on the interior of the bell, and shortly flows down in drops into a vessel placed beneath. In the mineral world we scarcely find hydrogen occur- ring in much quantity, save as water. It is a constant ingredient of plants and animals, and of nearly all the numberless substances which are products of organic life. Hydrogen forms with carbon a large number of com- pounds, the most common of which are the volatile oils, like oil of turpentine, oil of lemon, etc. The chief illu- minating ingredient of coal gas (ethylene or olefiant gas), the coal or rock oils (kerosene), together with benzine and paraffine, are so-called hydro-carbons. Sulphur is a well-known solid substance, occurring in commerce either in sticks (brimstone, roll sulphur) or as a fine powder (flowers of sulphur), having a pale yellow color, and a peculiar odor and taste. Uncombined sulphur is comparatively rare, the com- mercial supplies being almost exclusively of volcanic ori- gin ; but, in one or other form of combination, this ele- ment is universally diffused. Sulphur is combustible. It burns in the air with a pale blue flame, in oxygem gas with a beautiful purple- blue flame, yielding in both cases a suffocating and fum- ing gas of peculiar nauseous taste, which is called sul- phurous acid gas or sulphur dioxide. EXP. 15. Heat a bit of sulphur as large as a grain of wheat on a slip of iron or glass, over the flame of a spirit lamp, for observing its fusion, combustion, and the development of sulphur dioxide. Further, scoop out a little hollow in a piece of chalk, twist a wire round the latter to serve for a handle, as in Fig. 3 ; heat the chalk with a fragment of sul- phur upon it until the latter ignites, and bring it into a bottle of oxygen gas. The purple flame is shortly obscured by an opaque white fume of sulphur dioxide. Sulphur forms with oxygen another compound, the tri- oxide, which, in combination with water, constitutes com- THE VOLATILE PAET OF PLANTS. 27 mon sulphuric acid, or oil of vitriol. This oxide is devel- oped to a slight extent during the combustion of sulphur in the air and the acid is prepared on a large scale for commerce by a complicated process. Sulphur unites with most of the metals, yielding com- pounds known as sulphides, or formerly as sulphurets. These exist in nature in large quantities, especially the sulphides of iron, copper, and lead, and many of them are valuable ores. Sulphides may be formed artificially by heating most of the metals with sulphur. EXP. 16. Heat the bowl of a tobacco-pipe to a low red heat In a stove or furnace ; have in readiness a thin iron wire or watch-spring made into a spiral coil ; throw into the pipe-bowl some lumps of sulphur, and when these melt and boil, with formation of a red vapor or gas, intro- duce the iron coil, previously heated to redness, into the sulphur vapor. The sulphur and iron unite ; the iron, in fact, burns in the sulphur gas, giving rise to a black iron sulphide, in the same manner as in Exp. 7 it burned in oxygen gas and produced an iron oxide. The iron sulphide melts to brittle, round globules, and remains in the pipe-bowl. With hydrogen, the element we are now considering unites to form a gas that possesses in a high degree the odor of rotten eggs, and is, in fact, the chief cause of the noisomeness of this kind of putridity. This gas, com- monly called sulphuretted hydrogen, or hydrogen sulphide, is dissolved in, and evolved abundantly from, the water of sulphur springs. It may be produced artificially by acting on some metallic sulphides with dilute sulphuric or hydrochloric acid. EXP. 17. Place a lump of the iron sulphide prepared in Exp. 16 in a cup or wine-glass, add a little water, and lastly a little hydrochloric acid. Bubbles of hydrogen sulphide will shortly escape. In soils, sulphur occurs almost invariably in the form of sulphates, compounds of sulphuric acid with metals, a class of bodies to be hereafter noticed. In plants, sulphur is always present, though usually in small proportion. The turnip, the onion, mustard, horse- radish, and assafoatida owe their peculiar flavors to vola- tile oils of which sulphur is an ingredient. 28 HOW CROPS GROW. Albumin, globulin, casein and similar principles, never absent from plant or animal, possess also a small con- tent of sulphur. In hair and horn it occurs to the amount of three to five per cent. When organic matters are burned with full access of air, their sulphur is oxidized and remains in the ash as sulphates, or escapes into the air as sulphur dioxide. Phosphorus is an element which has such intense af- finities for oxygen that it never occurs naturally in the free state, and when prepared by art, is usually obliged to be kept immersed in water to prevent its oxidizing, or even taking fire. It is known to the chemist in the solid state in two distinct forms. In the more commonly oc- curring form, it is colorless or yellow, translucent, wax- like in appearance ; is intensely poisonous, inflames by moderate friction, and is luminous in the dark ; hence its name, derived from two Greek words signifying light- bearer. The other form is brick-red, opaque, far less in- flammable, and destitute of poisonous properties. Phos- phorus is extensively employed for the manufacture of friction matches. For this purpose yellow phosphorus is chiefly used. When burned in air or in oxygen gas this ele- ment forms a white substance phosphorus pentoxide (formerly termed anhydrous phosphoric acid) which dis- solves in water, at the same time uniting chemically with a portion of the latter, and thus yielding a body of the utmost agricultural importance, viz., phosphoric acid, EXP. 18. Burn a bit of phosphorus under a bottle, as in Exp. 8, omit- ting the water on the plate. The snow-like cloud of phosphorus pen- toxide gathers partly on the sides of the bottle, but mostly on the plate. It attracts moisture when exposed to the air, and hisses from develop- ment of heat when put into water. Dissolve a portion of it in hot water, and observe that the solution is acid to the taste. Finally evapo- rate the solution to dryness at a gentle heat. Instead of recovering thus the white opaque phosphorus pentoxide, the residue is a trans- parent mass of phosphoric acid, a compound of phosphorus, oxygen and hydrogen. In nature phosphorus is usually found in the form of THE VOLATILE PART OF PLANTS. 29 phosphates, which are phosphoric acid whose hydrogen has been partly or entirely replaced by metals. In plants and animals, it exists for the most part as phosphates of calcium (or lime), magnesium (or mag- nesia), potassium (or potash), and sodium (or soda). The bones of animals contain a considerable proportion (10 per cent.) of phosphorus, mainly in the form of cal- cium phosphate. It is from this that the phosphorus employed for matches is largely procured. EXP. 19. Burn a piece of bone in a fire until it becomes white, or nearly so. The bone loses about half its weight. What remains is bone-earth or bone-ash, and of this 90 per cent, is calcium phosphate. Phosphates are readily formed by bringing together solutions of various metals with solution of phosphoric acid. EXP. 20. Pour into each of two wine or test glasses a small quantity of the solution of phosphoric acid obtained in Exp. 18. To one, add some lime-water (see note p. 19) until a white cloud or precipitate is per- ceived. This is a calcium phosphate. Into the other portion drop solu- tion of alum. A translucent cloud of aluminium phosphate is immedi- ately produced. In soils and rocks, phosphorus exists in the state of phosphates of calcium, aluminium, and iron. The tissues and juices of animals and plants generally contain small proportions of several highly complex " or- ganic compounds" in which phosphoric acid is associated with the elements carbon, oxygen, hydrogen and nitrogen. Such substances are chlorophyll, lecithin and nuclein, to be noticed hereafter. We have thus briefly considered the more important characters of those six bodies which constitute that part of plants, and of animals also, which is volatile or de- structible at high temperatures, viz. : carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus. Out of these substances, which are often termed the organic elements of vegetation, are chiefly compounded all the numberless products of life to be met with, either in the vegetable or animal world. 30 HOW CROPS GROW. ULTIMATE COMPOSITION OF VEGETABLE MATTER. To convey an idea of the relative proportions in which these six elements exist in plants, a statement of the ultimate or elementary percentage composition of several kinds of vegetable matter is here subjoined. Grain of Straw of Tubers of Grain of Hay of Red, Wheat. Wheat. Potato. Peas. Clover. Carbon ...................... 46.1 48.4 44.0 46.5 47.4 Hydrogen ................... 5.8 5.3 5.8 6.2 5.0 Oxygen ...................... 43.4 38.9 44.7 40.0 37.8 Nitrogen .................... 2.3 0.4 1.5 4.2 2.1 Ash, including sulphur \ 9 . 7ft 4n ,1 7T and phosphorus 100.0 100.0 100.0 100.0 100.0 3ulj5hur ................... 0.12 0.14 0.08 0.21 0.18 Phosphorus ................. 0.30 0.80 0.34 0.34 0.20 Our attention may now be directed to the study of such compounds of these elements as constitute the basis of plants in general ; since a knowledge of them will pre- pare us to consider the remaining elements with a greater degree of interest. Previous to this, however, we must, first of all, gain a clear idea of that force chemical affinity in virtue of whose action these elements are held in their combina- tions and, in order to understand the language of chem- ical science, must know something of the views that now prevail as to the constitution of matter. CHEMICAL AFFINITY. THE ATOMIC-MOLECULAR THEORY. Chemical Attraction or Affinity is that force or kind of energy which unites or combines two or more sub- stances of unlike character, to a new body different from its ingredients. Chemical Combination differs essentially from mere mixture. Thus we may put together in a vessel the two gases, oxygen and hydrogen, and they will remain uncom- biued for an indefinite time, occupying their original vol- THE VOLATILE PAET OP PLANTS. 31 time ; but if a flame be brought into the mixture they in- stantly unite with a loud explosion, and, in place of the light and bulky gases, we find a few drops of water, which is a liquid at ordinary temperatures, and in winter weather becomes solid, which does not sustain combus- tion like oxygen, nor itself burn as does hydrogen ; but is a substance having its own peculiar properties, differ- ing from those of all other bodies with which we are ac- quainted. In the atmosphere we have oxygen and nitrogen in a state of mere mixture, each of these gases exhibiting its own characteristic properties. When brought into chem- ical combination, they are capable of yielding a series of no less than five distinct compounds, one of which is the so-called laughing-gas, while the others form suffocating and corrosive vapors that are totally irrespirable. Chemical Decomposition. Water, thus composed or put together by the exercise of affinity, is easily de- composed or taken to pieces, so to speak, by forces that oppose affinity e. g., heat and electricity or by the greater affinity of some other body e. g., sodium as al- ready illustrated in the preparation of hydrogen, Exp. 11. Definite Proportions. A further distinction be- tween chemical union and mere mixture is, that, while two or more bodies may, in general, be mixed in all pro- portions, bodies combine chemically in comparatively few proportions which are fixed and invariable. Oxygen and hydrogen, e. g., are found united in nature, princi- pally in the form of water ; and water, if pure, is always composed of one-ninth hydrogen and eight-ninths oxy- gen by weight, or, since oxygen is, bulk for bulk, sixteen times heavier than hydrogen, of one volume or measure of oxygen to two volumes of hydrogen. Atoms. It is now believed that matter of all kinds consists of indivisible and unchangeable particles called atoms, which are united to each other by chemical at- 32 HOW CEOPS GROW. traction, and cannot ordinarily exist in the free state. On this view each particular kind of matter or chemical substance owes its individuality either to the special kinds or to the numbers of the atoms it consists of. Atoms may be defined as the smallest quantities of matter which can exist in chemical combination and the smallest of which we have any knowledge or conception. Atomic Weight of Elements. On the hypothesis that chemical union takes place between atoms of the elements, the simplest numbers expressing the propor- tions by weight* in which the elements combine, are ap- propriately termed atomic weights. These numbers are only relative, and since hydrogen is the element which unites in the smallest proportion by weight, it is assumed as the standard unit. From the results of a great number of the most exact experiments, chemists have generally agreed upon the atomic weights given in the subjoined table for the elements already mentioned or described. Symbols. For convenience in representing chemical changes, the first letter (or letters) of the Latin name of the element is employed instead of the name itself, and is termed its symbol. TABLE OP ATOMIC WEIGHTS AND SYMBOLS OF ELEMENTS.f Element. Atomic Weight. Symbol. Hydrogen 1 H Carbon 12 C Oxygen 16 O Nitrogen 14 N Sulphur 32 S Phosphorus 31 P Chlorine 35.5 Cl Mercury 200 Hg (Hydrargyrum) Potassium 39 K (Kalium) Sodium 23 Na (Natrium) Calcium 40 Ca Iron 56 Fe (Ferrum) * Unless otherwise stated, parts or proportions by weight are always to be understood. t Now, chemists receive as the true atomic weights double the num- bers "that were formerly employed, those of hydrogen, chlorine and a few others excepted. "The atomic weights here given are mostly whole numbers. The actual atomic weights, as experimentally determined, differ from the above by small fractions, wluch may be neglected. THE VOLATILE PART OF PLANTS. 33 Multiple Proportions. When two or more bodies unite in several proportions, their quantities, when not expressed by the atomic weights, are twice, thrice, four, or more times, these weights ; they are multiples of the atomic weights by some simple number. Thus, carbon and oxygen form two commonly occurring compounds, viz., carbon monoxide, consisting of one atom of each in- gredient, and carbon dioxide, which contains to one atom, or 12 parts by weight, of carbon, two atoms, or 32 parts by weight, of oxygen. Molecules* contain and consist of chemically-united atoms, and are the smallest particles of matter that can have an individual or physical existence. While the atoms compose and give character to the molecules, the molecules alone are sensibly known to us, and they give character to matter as we find it in masses, either solid, liquid or gaseous. In solids the molecules more or less firmly cohere together ; in liquids they have but little cohesion, and in gases they are far apart and tend to sepa- rate from each other. The so-called "elements" are, in fact, mostly compounds whose molecules consist of two or more like atoms, while all other chemical substances are compounds whose molecules are made up of two or more unlike atoms. Molecular Weights of Compounds. The mole- cular weight of a compound is the sum of the weights of the atoms that compose it. For example, water being composed of 1 atom, or 16 parts by weight, of oxygen, and 2 atoms, or 2 parts by weight, of hydrogen, has the molecular weight of 18. f The following scheme illustrates the molecular compo- sition of a somewhat complex compound, one of the car- * Latin diminutive, signifying a little mass. t We must refer to recent treatises on chemistry for fuller informa- tion as to atoms and molecules and the methods of finding the atomic and molecular weights. 3 34 HOW CEOPS GBOW. bonates of ammonium, which consists of four elements, ten atoms, and has a molecular weight of seventy-nine. Ammonia gas results from the union of an atom of nitrogen with three atoms of hydrogen. One molecule of ammonia gas unites with a molecule of carbon dioxide gas and a molecule of water to produce a molecule of ammonium carbonate. Atoms. Atomic Molecular weights, weights. {Ammonia (Hydrogen, 3 = 3 ) _ 117 "| Imol. {Nitrogen, 1 = 14 { *' Carbon di- ( Carbon, 1 = 12 ) -44 I _ 79 oxide 1 mol.- } Oxygen, 2 = 32 } ~ Water, _< Hydrogen, 2 = 2 ) _ la 1 mol. \ Oxygen, 1 =: 16 j 18 J Notation and Formulas of Compounds. For the purpose of expressing easily and concisely the composi- tion of compounds, and the chemical changes they undergo, chemists have agreed to make the symbol of an element signify one atom of that element. Thus H implies not only the light, combustible gas hydrogen, but also one part of it by weight as compared with other elements, and S suggests, in addition to the idea of the body sulphur, the idea of 32 parts of it by weight. Through this association of the atomic weight with the symbol, the composition of compounds is expressed in the simplest manner by writing the symbols of their elements one after the other. Thus, carbon monoxide is represented by CO, mercuric oxide by HgO, and iron monosulphide by FeS. The symbol 00 con- veys to the chemist not only the fact of the existence of carbon monoxide, but also instructs him that its mole- cule contains an atom each of carbon and of oxygen, and from his knowledge of the atomic weights he gathers the proportions by weight of the carbon and oxygen in it. When a compound contains more than one atom of an element, this is shown by appending a small figure to the symbol of the latter. For example : water consists of two atoms of hydrogen united to one of oxygen, and iu 35 symbol is H 2 0. In like manner the symbol of carbon dioxide is C0 2 . When it is wished to indicate that more than one mole- cule of a compound exists in combination or is concerned in a chemical change, this is done by prefixing a large figure to the symbol of the compound. For instance, two molecules of water are expressed by 2 H 2 0. The symbol of a compound is usually termed a formula and if correct is a molecular formula and shows the com- position of one molecule of the substance. Subjoined is a table of the molecular formulas of some of the com- pounds that have been already described or employed. FORMULAS OF COMPOUNDS. Name. Formula. Molecular Weight. Water H Z O 18 Hydrogen Sulphide H 2 S 34 Iron Monosulphide FeS 88 Mercuric Oxide HgO 216 Carbon Dioxide CO, 44 Calcium Chloride CaCl, 111 Sulphur Dioxide SO, 64 Sulphur Trioxide SO, 80 Phosphorus Pentoxide P 2 O 6 142 Empirical and Rational Formulas. It is obvious that many different formulas can be made for a body of complex character. Thus, the carbonate of ammonium, whose composition has already been stated (p. 33), and which contains 1 atom of Nitrogen, 1 atom of Carbon, 3 atoms of Oxygen, and 5 atoms of Hydrogen, may be most compactly expressed by the symbol NC0 8 H 6 . Such a formula merely informs us what elements and how many atoms of each element enter into the compo- sition of the substance. It is an empirical formula, being the simplest expression of the facts obtained by analysis of the substance. Rational formulas, on the other hand, are intended to convey some notion as to the constitution, formation, or HOW CBOPS GROW. modes of decomposition of the body. For example, the real arrangement of the atoms in ammonium carbonate is believed to be expressed by the rational (or structural) formula =\O-H in which the carbon is directly united to oxygen, to which latter one hydrogen and the nitrogen are also linked, the remaining hydrogens being combined to the nitrogen. Valence. The connecting lines or dashes in the fore- going formula show the valence of the several atoms, i. e. , their "atom-fixing power." The single dash from H indicates that hydrogen is univalent or lias a valence of one. The two dashes connected with express the bivalence of oxygen or that the atom of this element can combine with two hydrogens or other univalent atoms. The nitrogen is united on one hand with 4 hydrogen atoms, and also, on the other hand, satisfies half the val- ence of oxygen ; it is accordingly quinquivalent, i. e. , has five units of valence. Carbon is quadrivalent, being joined to oxygen by four units of valence. Equations of Formulas serve to explain the results of chemical reactions and changes. Thus, the breaking up by heat of potassium chlorate into potassium chloride and oxygen is expressed by the following statement: Potassium Chlorate. Potassium Chloride. Oxygen 2 KC1O, = 2 KC1 + 3 O, The sign of equality, =, shows that what is written before it supplies and is resolved into what follows it. The sign -j- indicates and distinguishes separate com- pounds. The employment of this kind of short-hand for exhib- iting chemical changes will find frequent illustration as we proceed with onr subject. Modes of Stating Composition of Chemical $7 Compounds. These are two: 1, atomic or molecular statements, and 2, centesimal statements, or proportions in one hundred parts (per cent, p. c., or %). These modes of expressing composition are very useful for com- paring together different compounds of the same ele- ments, and, while usually the atomic statement answers for substances which are comparatively simple in their composition, the statement per cent is more useful for complex bodies. The composition of the two compounds of carbon with oxygen is given below according to both methods. Atomic. Per cent. Atomic. Percent. Carbon (C), 12 42.86 (C) 12 27.27 Oxygen (O), 16 57.14 (O 2 ) 32 72.73 Carbon Monoxide (CO), 28 100.00 Carbon Dioxide (CO 2 ), 44 100.00 The conversion of one mode of statement into the other is a case of simple rule of three, which is illustrated in the following calculation of the centesimal composition of water from its molecular formula. Water, H 2 O, has the molecular weight 18, I. e., it consists of two atoms of hydrogen, or two parts, and one atom of oxygen, or sixteen parts by weight. The arithmetical proportions subjoined serve for the calculation, viz. : H 2 O Water H Hydrogen 18 J 100 : t 2 ; per cent sought (11.11) H 2 O Water O Oxygen 18 ' 100 : : 16 : per cent sought (=88.89) By multiplying together the second and third terms of these propor- tions, and dividing by the first, we obtain the required per cent, viz., of hydrogen, 11.11 ; and of oxygen, 88.89. The reader must bear well in mind that chemical affin- ity manifests itself with very different degrees of inten- sity between different bodies, and is variously modified, excited, or annulled, by other natural agencies and forces, especially by heat, light and electricity. 8 4. VEGETABLE ORGANIC COMPOUNDS, OB PROXIMATE PRINCIPLES. We are now prepared to enter upon the study of the organic compounds, which constitute the vegetable struc- 38 HOW CBOPS GROW. ture, and which are produced from the elements carbon, oxygen, hydrogen, nitrogen, sulphur, and phosphorus, by chemical agency. The number of distinct substances found in plants is practically unlimited'. There are already well known to chemists hundreds of oils, acids, bitter principles, resins, coloring matters, etc. Almost every plant contains some organic body peculiar to itself, and usually the same plant in its different parts reveals to the senses of taste and smell the presence of several individual substances. In tea and coffee occurs an intensely bitter " active principle," caffeine. From tobacco an oily liquid of eminently narcotic and poison- ous properties, nicotine, can be extracted. In the orange are found no less than three oils ; one in the leaves, one in the flowers, and a third in the rind of the fruit. Notwithstanding the great number of bodies thus occurring in the vegetable kingdom, it is a few which form the bulk of all plants, and especially of those which have an agricultural importance as sources of food to man and animals. These substances, into which any plant may be resolved by simple, partly mechanical means, are conveniently termed proximate principles, and we shall notice them in some detail under eight principal classes, viz.: 1. WATER. 2. The CARBHYDRATES. 3. The VEGETABLE ACIDS. 4. The FATS and OILS. 5. The ALBUMINOIDS or PROTEIN BODIES and FER- MENTS. 6. The AMIDES. 7. The ALKALOIDS. 8. PHOSPHORIZED SUBSTANCES. i. Water, H 2 0, as already stated, is the most abund- ant ingredient of plants. It is itself a compound of oxygen and hydrogen, having the following centesimal composition : THE VOLATILE PART OF PLANTS. 39 Oxygen ... Hydrogen . 88.89 11.11 100.00 It exists in all parts of plants, is the immediate cause of the succulence of their tender portions, and is essen- tial to the life of the vegetable organs. In the following table are given the percentages of water in some of the more common agricultural products in the fresh state, but the pro- portions are not quite constant, even in the same part of different specimens of any given plant. WATEB IN FRESH PLANTS. (PER CENT.) Average. Meadow grass 71 Red clover 80 Maize, as used for fodder 82 Cabbage 85 Potato tubers 75 Sugar beets 81 Range. 60 to 78 Carrots 86 Turnips 91 In living plants, water is usually perceptible to the eye or feel, as sap. But it is not only fresh plants that contain water. When grass is made into hay, the water is by no means all dried out, but a considerable propor- tion remains in the pores, which is not recognizable by the senses. So, too, seasoned wood, flour, and starch, when seemingly dry, contain a quantity of invisible water, which can be removed by heat. EXP. 21. Into a wide glass tube, like that shown in Fig. 2, place a spoonful of saw dust, or starch, or a little hay. Warm over a lamp, but very slowly and cautiously, so as not to burn or blacken the sub- stance. Water will be expelled from the organic matter, and will col- lect on the cold part of the tube. It is thus obvious that vegetable substances may con- tain water in at least two different conditions. Red clover, for example, when growing or freshly cut, contains about 80 per cent of water. When the clover is dried, as for making hay, the greater share of this wa- ter escapes, so that the air-dry plant con- tains but about 15 per cent. On subject- ing the air-dry clover to a temperature Fig. 9. of 212 for some hours, the water is completely expelled, and the substance becomes really dry, i. e., water-free. 40 HOW CROPS GROW. To drive off all water from vegetable matters, the chemist usually employs a water-oven, Fig. 9, consisting of a vessel of tin or copper plate, with double walls, between which is a space that may be half filled with water. The substance to be dried is placed in the interior chamber, the door is closed, and the water is brought to boil by the heat of a lamp or stove. The precise quantity of water belonging to, or contained in, a substance, is ascertained by first weighing the sub- stance, then drying it until its weight is constant. The loss is water. In the subjoined table are given the average quantities, per cent, of water existing in various vegetable products when air-dry. WATER IN AIB-DKY PLANTS. PER CENT. Meadow grass (hay) 15 Red clover hay 17 Pine wood 20 Straw and chaff of wheat, rye, etc 15 Bean straw 18 Wheat (rye, oat) kernel 14 Maize kernel 12 That portion of the water which the fresh plant loses by mere exposure to the air is chiefly the water of its juices or sap, and, on crushing the fresh plant, is mani- fest to the sight and feel as a liquid. It is, properly speak- ing, the free water of vegetation. The water which remains in the air-dry plant is imperceptible to the senses while in the plant, can only be discovered on expelling it by heat or otherwise, and may be designated as the hygroscopic or combined water of vegetation. The amount of water contained in either fresh or air- dry vegetable matter is somewhat fluctuating, according to the temperature and the dryness of the atmosphere. 2. The Carbhydrates. This group falls into three subdivisions, viz. : a. THE AMYLOSES, comprising Cellulose, Starch, Inu- lin, Glycogen, the Dextrins and Gums, having the formula (C 6 Hi 5 )n. ~b. THE GLUCOSES, which include Dextrose, Levulose, Galactose and similar sugars, having the composition C 6 Hi 2 6 . c. THE SUCROSES, viz. : Cane Sugar or Saccharose, Maltose, Lactose and other sugars, whose formula iu most cases is C l2 H 22 On. THE VOLATILE PART OF PLANTS. 41 On account of their abundance and uses the Carbhy- drates rank as the most important class of vegetable sub- stances. Their name refers to the fact that they consist of Carbon, Hydrogen and Oxygen, the last two elements being always present in the same proportions that are found in water. These bodies, especially cellulose and starch, form by far the larger share perhaps seven-eighths of all the dry matter of vegetation, and most of them are distributed throughout all parts of plants. a. The Amyloses. Cellulose (CjH 10 5 )n. Every agricultural plant is an aggregate o.f microscopic cells, i. e., is made up of minute sacks QY closed tubes, adhering to each other. Fig. 10 reprs?e^its an extremely thin slice from the stem of a cabbage, magnified 230 diameters. The united walls of two cells are seen in sec- tion at a, whale at 6 an empty space is noticed. Fig. 10. The crater coating, or wall, of the vegetable cell con- sists chiefly or entirely of cellulose. This substance is accordingly the skeleton or framework of the plant, and the material that gives toughness and solidity to its parts. Next to water it is the most abundant body in the vege- table world. 3 HOW CHOPS GROW. Nearly all plants and all their parts contain cellulose, but it is relatively most abundant in stems and leaves. In seeds it forms a large portion of the husk, shell, or other outer coating, but in the interior of the seed it exists in small proportion. The fibers of cotton (Fig. 11, a), hemp, and flax (Fig. 11, J), and white cloth and unsized paper made from these materials, are nearly pure cellulose. The fibers of cotton, hemp, and flax are simply long and thick-walled cells, the appearance of which, when highly magnified, is shown in Fig. 11 where a represents the thinner, more soft, and col lapsed cotton fiber, and 6 the thicker and more due able fiber of linen. Wood, or woody fiber, consists of long and slender cells of various forms and di- mensions (see p. 293), which are delicate when young (in the sap wood), but as. they become older fill up interiorly by the deposition of re peated layers of cellulose, which is more or less inter- grown with other substances.* The hard shells of nuts and stone fruits contain a basis of cellulose, which is im- pregnated with other matters. When quite pure, cellulose is a white, often silky or spongy, and translucent body, its appearance varying * Wood was formerly supposed to consist of cellulose and so-called "lignin." On this view, according to F. Schulze, lignin impregnates (not simply incrusts) the cell-wall, is soluble in hot alkaline solutions, and is readily oxidized by nitric acid. Schulze ascribes to it the com- position Carbon 55.3 Hydrogen 5.8 Oxygen 38.9 100.0 This is, however, simply the inferred composition of what is left after the cellulose, etc., have been removed. " Lignin " cannot be separated in the pure state, and has never been analyzed. What is thus desig- nated is a mixture of several distinct substances. Fremy's lignose, lig- none, lignin, and lignireose, as well as J. Erdman's glycolignose and liguose, are not established as chemically distinct substances. THE VOLATILE PAET OF PLANTS. 43 somewhat according to the source whence it is obtained. In the air-dry state, at common temperatures, it usually contains about 10 % of hygroscopic water. It has, in common with animal membranes, the character of swell- ing up when immersed in water, from imbibing this liquid ; on drying again, it shrinks in bulk. It is tough and elastic. Cellulose, as it naturally occurs, for the most part dif- fers remarkably from the other bodies of this group, in the fact of its slight solubility in dilute acids and alkalies. It is likewise insoluble in water, alcohol, ether, the oils, and in most ordinary solvents. It is hence prepared in a state of purity by acting upon vegetable tissues con- taining it, with successive solvents, until all other mat- ters are removed. The "skeletonized" leaves, fruit vessels, etc., which compose those beautiful objects called phantom bouquets, are commonly made by dis- solving away the softer portions of fresh succulent plants by a hot solu- tion of caustic soda, and afterwards whitening the skeleton of fibers fliat remains by means of chloride of lime (bleaching powder). They are almost pure cellulose. Skeletons may also be prepared by steeping vegetable matters in a Aixture of potassium chlorate and dilute nitric acid for a number of EXP. 22. To 500 cubic centimeters* (or one pint) of nitric acid of dens- ity 1.1, add 30 grams (or one ounce) of pulverized potassium chlorate, and dissolve the latter by agitation. Suspend in this mixture a num- ber of leaves, etc.,t and let them remain undisturbed, at a temperature not above 65 F., until they are perfectly whitened, which may require from 10 to 20 days. The skeletons should be floated out from the solution on slips of paper, washed copiously in clear water, and dried under pressure between folds of unsized paper. The fibers of the whiter and softer kinds of wood are now much em- ployed in the fabrication of paper. For this purpose the wood is rasped * On subsequent pages we shall make frequent \ise of some of the French decimal weights and measures, for the reasons that they are much more convenient than the English ones, and are now almost ex- clusively employed in all scientific treatises and investigations. For small weights, the gram, abbreviated gm. (equal to 15 grains, nearly), is the customary unit. The unit of measure by volume is the cubic cen- timeter, abbreviated c. c. (30 c. c. equal one fh'iid ounce nearly). Gram weights and glass measures graduated into cubic centimeters are fur- nished by all dealers in chemical apparatus. t Full-grown but not old leaves of the elm, maple, and maize, heads of unripe grain, slices of the stem and joints of maize, etc., may be em- ployed to furnish skeletons that will prove valuable in the study of th structure of these organs. 44 HOW CROPS GKOW. to a coarse powder by machinery, then heated with a wsak soda lye, and finally bleached with chloride of lime. Though cellulose is insoluble in, or but slightly affected by, weak or dilute acids and alkalies, it is altered and dis- solved by these agents, when they are concentrated or hot. The result of the action of strong acids and alka- lies is various, according to their kind and the degree of strength in which they are employed. Cellulose Nitrates. Strong nitric acid transforms cellulose into various cellulose nitrates according to its concentration. In these bodies portions of the hydrogen and oxygen of cellulose are replaced by the atomic group (radicle), N0 3 . Cellulose hexanitrate, C 12 H 14 (N0 3 ) 6 10 , is employed as an explosive under the name gun cotton. The collodion employed in photography is a solution in ether of the penta- and tetranitrates, C 12 H 15 (N0 3 ) 5 Oio and Ci 2 H 16 (N03)40 10 . Sodium hydroxide changes these cellulose nitrates into cellulose and sodium nitrate. Hot nitric acid of ordinary strength destroys cellulose by oxidizing it with final formation of carbon dioxide gas and oxalic acid. Cellulose Sulphates. "When cold sulphuric acid acts on cellulose the latter may either remain apparently unaltered or swell up to a pasty mass, or finally dissolve to a clear liquid, according to the strength of the acid, the time of its action, and the quality (density) of the cellulose. In excess of strong oil of vitriol, cellulose (cotton) gradually dissolves with formation of various cellulose sulphates, in which OH groups of the cellulose are replaced by S0 4 of sulphuric acid. These sulphates are soluble in water and alcohol, and when boiled with water easily decompose, reproducing sulphuric acid, but not cellulose. Instead of the latter, dextrin and dextrose (grape sugar) appear. Soluble Cellulose, or Amyloid. In a cooled mix- ture of oil of vitriol, with about ^ its volume of water, THE VOLATILE PART OF PLANTS. 45 cellulose dissolves. On adding much water to the solu- tion there separates a white substance which has the same composition as cellulose, but is readily converted into dextrin by cold dilute acid. This form of cellulose as- sumes a fine blue color when put in contact with iodine- tincture and sulphuric acid. EXP. 23. Fill a large test-tube first with water to the depth of two or three inches. Then add gradually three times that bulk of oil of vitriol, and mix thoroughly. When well cooled pour a part of the liquid on a slip of unsized paper in a saucer. After some time the paper is seen to swell up and partly dissolve. Now flow it with solution of iodine,* when these dissolved portions will assume a fine and intense blue color. This deportment is characteristic of cellulose, and may be employed for its recognition under the microscope. If the experiment be re- peated, using a larger proportion of acid, and allowing the action to continue for a considerably longer time, the substance producing the blue color is itself destroyed, and addition of iodine has no effect.f Un- altered cellulose gives with iodine a yellow color. Paper superficially converted into amyloid constitutes vegetable parchment, which is tough and translucent, much resembling bladder, and very useful for various purposes, among others as a substitute for sausage " skins." EXP. 24. Into the remainder of the cold acid of Exp. 23 dip a strip of unsized paper, and let it remain for about 15 seconds ; then remove, and rinse it copiously in water. Lastly, soak some minutes in water, to which a little ammonia is added, and wash again with pure water. These washings are for the purpose of removing the acid. The success of this process for obtaining vegetable parchment depends upon the proper strength of the acid, and the time of immersion. If need be, repeat, varying these conditions slightly, until the result is obtained. The denser and more impure forms of cellulose, as they occur in wood and straw, are slowly acted upon by chem- ical agents, and are not easily digestible by most animals ; but the cellulose of young and succulent stems, leaves, and fruits is digestible to a large extent, especially by animals which naturally feed on herbage, and therefore cellulose is ranked among the nutritive ingredients of cattle-food. Chemical composition of cellulose. This body is acom- * Dissolve a fragment of iodine as large as a wheat kernel in 20 c. c. of alcohol, and add 100 c. c. of water to the solution. t According to Grouven, cellulose prepared from rye straw (and im- pure?) requires several hours' action of sulphuric acid before it will strike a blue color with iodine (Zter Salsmunder liericht, p. 467). 46 HOW CHOPS GEOW. pound of the three elements, carbon, oxygen, and hydro- gen. Analyses of it, as prepared from a multitude of sources, demonstrate that its composition is expressed by the formula (C 6 H 10 O s )n. The value of n in this form- ula is not certainly known, but is at least two, and the formula C 12 H 20 Oio is very commonly adopted. In 100 parts it contains Carbon 44.44 Hydrogen 6.17 Oxygen 49.39 100.00 Modes of estimating cellulose. In statements of the composition of plants, the terms fiber, woody fiber, and crude cellulose are often met with. These are applied to more or less impure cellulose, which is ob- ta'ned as a residue after removing other matters, as far as possible, by alternate treatment with dilute acids and alkalies. The methods are Confessedly imperfect, because cellulose itself is dissolved to some ex- tent, and a portion of other matters often remains unattacked. The method of Henneberg, usually adopted ( Vs. St., VI, 407), is as follows : -igrams of the finely divided substance are boiled for half an hour with JOO cubic centimeters of dilute sulphuric acid (containing l\ per cent of tal of vitriol), and, after the substance has settled, the acid liquid is youred off. The residue is boiled again for half an hotir with 200 c. c. of dilute potash lye (containing 1J per cent of dry caustic potash), and, after removing the alkaline liquid, it is boiled twice with water as before. What remains is brought upon a filter, and washed with water, then with alcohol, and, lastly, with ether, as long as these solvents take up anything. This crude cellulose contains ash and nitrogen, for which corrections must be made. The nitrogen is assumed to belong to some albuminoid, and from its quantity the amount of the latter is calcu- lated ; (see p. 113). Even with these corrections, the quantity of cellulose is not obtained with entire accuracy, as is usually indicated by its appearance and its composition. While the crude cellulose thus prepared from the pea is perfectly white, that from wheat bran is brown, and that from rape- cake is almost black in color, from impurities that cannot be removed by this method. Grouven gives the following analyses of two samples of crude cellu- lose obtained by a method essentially the same as we have described. (2ter Salzmunder Bericht, p. 456.) Rye-straw fiber. Flax fiber. Water. 8.65 5.40 Ash 2.05 1.14 N 0.15 0.15 C 42.47 38.36 H. 6.04 5.89 40.64 48.95 100.00 100.00 On deducting water and ash, and making proper correction for the THE VOLATILE PAKT OF PLANTS. 4? nitrogen, the above samples, together with one of wheat-straw fiber, analyzed by Henneberg, exhibit the following composition, compared with pure cellulose. Eye-straw fiber. Flax fiber. Wheat-straw fiber. Pure cellulose. C .. 47.5 41.0 45.4 44.4 H... .... 6.8 6.4 6.3 6.2 45.7 62.6 48.3 49.4 100.0 100.0 100.0 100.0 Fr. Schulze has proposed (1857) another method for estimating cellu- lose, which, though troublesome, is in most cases more correct than the one already described. Kiihn, Aronstein, and H. Schulze (Henneberg's Journal fur Landwirthschaft, 1866, pp. 289 to 297) have applied this method in the following manner : One part of the dry pulverized sub- stance (2 to 4 grams), which has been previously extracted with water, alcohol, and ether, is placed in a glass-stoppered bottle, with 0.8 part of potassium chlorate and 12 parts of nitric acid of specific gravity 1.10, and digested at a temperature not exceeding 65 F. for 14 days. At the expiration of this time, the contents of the bottle are mixed with some water, brought upon a filter, and washed, firstly, with cold and after- wards with hot water. When all the acid and soluble matters have been washed out, the contents of the filter are emptied into a beaker, and heated to 165 F. for about 45 minutes with weak ammonia (1 part commercial ammonia to 50 parts of water); the substance is then brought upon a weighed filter, and washed, first, with dilute ammonia, as long as this passes off colored, then with cold and hot water, then with alcohol, and, finally, with ether. The substance remaining con- tains a small quantity of ash and nitrogen, for which corrections must be made. The fiber is, however, purer than that procured by the other method, and the writers named obtained a somewhat larger quantity, by J to H per cent. The results appear to vary but about one per cent from the truth. The observations of Konig (Vs. St. 16), and of Hoffmeis- ter (Vs. St. 33, 155), show much larger differences in favor of Fr. Schulze's method. Hugo Muller (Die Pflanzenfaser, p. 27) has described a method of ob- taining cellulose from those materials which are employed in paper- making, which is based on the prolonged use of weak aqueous solu- tion of bromine. Trials made on hay and Indian-corn fodder with this method by Dr. Osborne, at the author's suggestion, gave results widely at variance with those obtained by Henneberg's method. The average proportions of cellulose found in various vegetable matters, in the usual or air-dry state, are as fol- lows : AMOUNT OF CELLULOSE IN PLANTS. Per cent. Per cent. Potato tuber 1.1 Red clover plant in flower 10 Wheatkernel 3.0 " " hay 34 Wheatmeal. 0.7 Timothy 23 Maize kernel 5.5 Maize cobs 38 Barley " 8.0 Oat straw 40 Oat " 10.3 Wheat" 48 Buckwheat kernel 15.0 Rye " 84 48 HOW CROPS GROW. Starch (C 6 H 10 5 )n is of very general occurrence in plants. The cells of the seeds of wheat, corn, and all other grains, and the tubers of the potato, contain this familiar body in great abundance. It occurs also in the wood of all forest trees, especially in autumn and winter. It accumulates in extraordinary quantity in the pith of some plants, as in the Sago-palm (Sagus Rttmphii), of the Malay Islands, a single tree of which may yield 800 pounds. The onion, and various plants of the lily tribe, are said to be entirely destitute of starch. The preparation of starch from the potato is very sim- ple. The potato tuber contains about 70 per cent, water, 24 per cent starch, and 1 per cent of cellulose, while the remaining 5 per cent consist mostly of matters which are easily soluble in water. By grating, the potatoes are reduced to a pulp; the cells are thus broken and the starch-grains set at liberty. The pulp is agitated on a fine sieve, in a stream of water. The washings run off milky from suspended starch, while the cell-tissue is re- tained by the sieve. The milky liquid is allowed to rest in vats until the starch is deposited. The water is then poured off, and the starch is collected and dried. Wheat-starch may be obtained by allowing wheaten flour mixed with water to ferment for several weeks. In this process the gluten, etc., are converted into soluble matters, which are removed by washing, from the unal- tered starch. Starch is now most largely manufactured from maize. A dilute solution of caustic soda is used to dissolve the albuminoids (see p. 87). The starch and bran remaining are separated by diffusing both in water, when the bran rapidly settles, and the water, being run off at the proper time, deposits nearly pure starch, the corn-starch of com- merce. Starch is prepared by similar methods from rice, horse- chestnuts, and various other plants. THE VOLATILE PAET OF PLANTS. 49 Arrow-root is starch obtained by grating and washing the root-sprouts of Maranta Indica, and M. arundinacea, plants native to the East and West Indies. EXP. 25. Reduce a clean potato to pulp by means of a tin grater. Tie up the pulp in a piece of not too fine muslin, and squeeze it repeatedly in a quart or more of water. The starch grains thus pass the meshes of the cloth, while the cellulose is retained. Let the liquid stand until the starch settles, pour off the water, and dry the residue. Starch, as usually seen, is either a white powder which consists of minute, rounded grains, and hence has a slightly harsh feel, or occurs in 5 or 6-sided columnar masses which readily crush to a powder. Columnar starch acquires that shape by rapid drying of the wet substance. When observed under a powerful magnifier, the starch-grains often present characteristic forms and dimensions. In potato-starch they are egg or kidney-shaped, and are distinctly marked with curved lines or ridges, which Fig. 12. surround a point or eye ; a, Fig. 12. Wheat-starch con- sists of grains shaped like a thick burning-glass, or spec- tacle-lens, having a cavity in the centre, J. Oat-starch is made up of compound grains, which are easily crushed into smaller granules, c. In maize and rice the grains are usually so densely packed in the cells as to present an angular (six-sided) outline, as in d. The starch of the bean and pea has the appearance of e. The minute 50 HOW CROPS GROW. starch-grains of the parsnip are represented at /, and those of the beet at g. The grains of potato-starch are among the largest, be- ing often 5 o of an inch in diameter; wheat-starch grains are about y^^ of an inch ; those of rice, ^^^ of an inch, while those of the beet-root are still smaller. The starch-grains have an organized structure, plainly seen in those from the potato, which are marked with curved lines or ridges surrounding a point or eye ; a, Fig. 12. When a starch-grain is heated cautiously, it swells and exfoliates into a series of more or less distinct layers. Starch, when air-dry, contains a considerable amount of water, which may range from 12 to 23 per cent. Most of this water escapes readily when starch is dried at 212, but a temperature of 230 F. is needful to expel it com- pletely. Starch, thus dried, has the same composition in 100 parts as cellulose, yiz. : Carbon 44.44 Hydrogen 6.17 Oxygen 49.39 100.00 Starch-grains are unacted upon by cold water, unless broken (see Exp. 26), and quickly settle from suspension in it, having a specific gravity of 1. 5. Iodine-Test for Starch. The chemist is usually able to recognize starch with the greatest ease and certainty by its peculiar deportment towards iodine, which, when dis- solved in water or alcohol and brought in contact with starch-grains, most commonly gives them a beautiful blue or violet color. This test may be used even in microscopic observations with the utmost facility. Some kinds of starch-grains are, however, colored red, some yellow, and a few brown, probably because of the pres- ence of other substances. EXP. 26. Shake together in a test-tube 30 c. c. of water and starch of the bulk of a kernel of maize. Add solution of iodine drop by drop, agitating until a faint purplish color appears. Pour off half the liquid THE VOLATILE PART OF PLAKfS. 51 Into another test-tube, and add at once to it one-fourth its bulk of iodine solution. The latter portion becomes intensely blue by trans- mitted, or almost black by reflected, light. On standing, observe that In the first case, where starch preponderates, it settles to the bottom, leaving a colorless liquid, which shows the insolubility of starch in cold water ; the starch itself has a purple or red tint. In the case iodine was used in excess, the deposited starch is blue-black. By the prolonged action of dry heat, hot water, acids, or alkalies, starch is converted first into amidulin, then into dextrin, and finally into the sugars maltose and dex- trose, as will be presently noticed. Similar transformations are accomplished by the action of living yeast, and of the so-called diastase of germinat- ing seeds. The saliva of man and plant-eating animals likewise disintegrates the starch-grains and mostly dissolves the starch by converting it into maltose (sugar). It is much more promptly converted into sugar by the liquids of the large intestine. It is thus digested when eaten by ani- mals. Starch is, in fact, one of the most important ingredients of the food of man and domestic animals. The starch-grains are not homogeneous. After pro- longed action of saliva, hot water, or of dilute acids on starch-grains, an undissolved residue remains which De- Saussure (1819) regarded as nearly related to cellulose. This residue is not changed by boiling water, but, under prolonged action of dilute acids, it finally dissolves. With iodine, after treatment with strong sulphuric acid, it gives the blue color characteristic of cellulose. There- fore it is commonly termed starch-cellulose. Starch-cellulose amounts to 0.5 to 6 per cent of the starch-grains, varying with the kind of starch and the nature and duration of the solvent action. Whether it be originally present or a result of the treatment by acids, etc., is undecided. The chemical composition of starch-cellulose is identi- cal with that of the entire starch-grain, viz. : (C 6 H 10 5 )n. The starch-grains also contain a small proportion of amidulin, or soluble starch, presently to be noticed. 62 HOW CROPS GROW. Gelatinous Starch. When starch is heated to near boiling with 12 to 15 times its weight of water, the grains swell and burst, or exfoliate, the water is absorbed, and the whole forms a, jelly. This is the starch- paste used by the laundress for stiffening muslin. The starch is but very slightly dissolved by this treatment. On freezing gelatinous starch, the water belonging to it is separated as ice and on melting remains for the most part distinct. EXP. 27. Place a bit of starch as large as a grain of wheat in 30 c. c. of cold water and heat to boiling. The starch is converted into thin, translucent paste. That a portion is dissolved is shown by filtering through paper and adding to one-half of the filtrate a few drops of iodine solution, when a perfectly clear blue liquid is obtained. The delicacy of the reaction is shown by adding to 30 c. c. of water a little solution of iodine, and noting that a, feu- dro/s of the solution of starch suffice to make the large mass of liquid perceptibly blue. When starch-paste is dried, it forms a hard, horn-like mass. Tapioca and Sago are starch, which, from being heated while still moist, is partially converted into starch-paste, and, on drying, acquires a more or less translucent aspect. Tapioca is obtained from the roots of various kinds of Manihot, cultivated in the West Indies and South America. Cassava is a preparation of the same starch, roasted. Sago is made in the islands of the East Indian Archipelago, from the pith of palms (Sagiis). It is granulated by forcing the paste through metallic sieves. Both tapioca and sago are now imitated from maize starch. Next to water and cellulose, starch is the most abund- ant ingredient of agricultural plants. In the subjoined table are given the proportions of starch in certain vegetable products, as determined by Dr. Dragendorff. The quantities are, however, somewhat variable. Since the figures below mostly refer to air-dry substances, the proportions of hygroscopic water found in the plants by Dragendorff are also given, the quantity of which, being changeable, must be taken into account in making any strict comparisons. AMOUNT OF STARCH IK PLANTS. Water. Starch. Per cent. Per cent. Wheat 13.2 59.5 Wheatflour 15.8 68.7 Rye 11.0 59.7 Oats 11.9 46.6 Barley 11.5 57.5 Timothy-seed 12.6 45.0 Rice (hulled) 13.3 61.7 Peas 5.0 37.3 Beans(white) 16.7 33.0 Clover-seed 10.8 10.8 Plaxseed 7.6 23.4 Mustard-seed 8.5 9.9 Colza-seed 5.8 8.6 Teltow turnips* dry substance 9.8 Potatoes dry substance 62.5 * A sweet and mealy turnip, grown 011 light soils, for table use. THE VOLATILE PART OF PLANTS. 53 Starch Is quantitatively estimated by various methods. 1. In case of potatoes or cereal grains, it may be determined roughly by direct mechanical separation. For this purpose 5 to 20 grams of the substance are reduced to fine division by grating (potatoes) or by sof- tening in warm water, and crushing in a mortar (grains). The pulp thus obtained is washed either upon a fine hair-sieve or in a bag of muslin, until the water runs off clear. The starch is allowed to settle, is dried, and weighed. The value of this method depends upon the care employed in the operations. The amount of starch falls out too low, because it is impossible to break open all the minute cells of the sub- stance analyzed. 2. In many cases starch may be estimated with great precision by conversion into sugar. For this purpose Sachsse heats 3 grams of air- dry substance, contained in a flask with reflux condenser, in a boiling water bath for 3 hours, with 200 c. c. of water and 20 c. c. of a 25 per cent hydrochloric acid. After cooling, the acid is nearly neutralized with sodium hydroxide, and the dextrose into which the starch has been con- verted is determined by Allihn's method, described on p. 65. Winton, Report Ct. Ag. Exp. St., 1887, p. 132. 3. For Dragendorff s method, see Henneberg's Journal, fur Land- Wirthschaft, 1862, p. 206. Amidulin, or Soluble Starch. A substance soluble in cold water appears to exist in small quantity in the in- terior of ordinary starcb-grains. It is not extracted by cold water from tbe unbroken starch, as shown by Exp. 26. On pulverizing starch-grains under cold water by rubbing in a mortar with sharp sand, the water, made clear by standing or filtration, gives with iodine the char- acteristic blue coloration. Exp. 27 shows that when starch is gelatinized by hot water, as in making starch paste, a small quantity of starch goes into actual solu- tion. Ordinary insoluble starch may be largely converted into soluble starch by moderate heating, either for a long time to the temperature of boiling water or for a short space to 375 F. Maschke obtained a perfectly clear solu- tion of potato-starch by heating it with 30 times its bulk of water in a sealed glass tube kept immersed for 8 days in boiling water. Zulkowski reached the same result by heating potato-starch (1 part) with commercial glycerine (16 parts). In this case the starch at first swells and the mixture acquires a pasty consistence, but, when the 54 HOW CEOPS GROW. temperature rises to 375 F., the starch dissolves to a nearly clear thin liquid. Amidulin also appears to be the first product of the action of diastase (the ferment of sprouting seeds) on starch and doubtless exists in malt. Soluble starch is colored blue by iodine and is thrown down from its solution in water, or glycerine, by addition of strong alcohol. It redissolves in water or weak alco- hol. Its concentrated aqueous solutions gelatinize on keeping and the jelly is no longer soluble in water. Dilute solutions when evaporated leave a transparent residue that is insoluble in water. On boiling together diluted sulphuric acid and starch the latter shortly dissolves, and if as soon as solution has taken place, the acid be neutralized with carbonate of lime and removed by filtration, soluble starch remains dissolved. (Schulze's Amidulin.) Amylodextrln. Nageli has described as Amylodextrin I and Amylo- dextrin II, two substances that result from the action of moderately strong acids on potato-starch at common temperatures. The starch when soaked for many weeks in 12% hydrochloric acid remains nearly unchanged in appearance, but the interior parts of the grains grad- ually dissolve out, being changed into amylodextrin II, which closely resembles and is probably identical with amidulin. The starch-grains that remain unchanged in outward appearance, if tested with iodine solution from time to time, are at first colored blue, but after some days they take on a violet tinge and after prolonged action of the acid are made red and finally yellow by iodine. The grains, which are now but empty shells, may be freed from acid by washing with cold water, and then, if heated to boiling with pure water, they readily dissolve to a clear solution (amylodextrin I), from which Nageli, by freezing and by evaporation, obtained crystalline disks. These bodies, when dry, have the same composition as cellulose, starch, and amidulin. Dextrin (CeH^Os) was formerly thought to occur dissolved in the sap of all plants. According to Von Bibra's investigations, the substance existing in bread- grains, which earlier experimenters believed to be dex- trin, is for the most part gum. Busse, who examined yarious young cereal plants and seeds, and potato tubers, for dextrin, found it only in old potatoes and young THE VOLATILE PART OF PLANTS. 55 wheat plants, and there in very small quantity. Accord- ing to Meissl, the soy bean contains 10 per cent of dex- trin. Dextrin is easily prepared artificially by the trans- formation of starch, or, rather, of amidulin derived from starch, and its interest to us is chiefly due to this fact. When starch is exposed some hours to the heat of an oven, or for 30 minutes to the temperature of 415 F., the grains swell, burst open, and are gradually converted into a light-brown substance, which dissolves readily in water, forming a clear, gummy solution. This is dex- trin, and thus prepared it is largely used in the arts, especially in calico-printing, as a cheap substitute for gum arabic. In the baking of bread it is formed from the starch of the flour, and often constitutes ten per cent of the loaf. The glazing on the crust of bread, or upon biscuits that have been steamed, is chiefly due to a coat- ing of dextrin. Dextrin is thus an important ingredient )f those kinds of food which are prepared from the Starchy grains by cooking. Commercial dextrin appears either in translucent brown masses or as a yellowish-white powder. On ad- dition of cold water, the dextrin readily dissolves, leaving oehind a portion of unaltered starch. When the solu- tion is mixed with strong alcohol, the dextrin separates in white flocks. With iodine, solution of commercial dextrin gives a fine purplish-red color. There are doubtless several distinct dextrins scarcely dis- tinguishable except by the different degrees to which they affect polarized light or by various chemical deportment (reducing effect on alkaline copper solutions). They are characterized as erythrodextrins, which give with iodine a red color, and achroodextrins, which give no color with iodine. Investigators do not agree as to the precise num- ber of dextrins that result from the transformation of starch. 56 HOW CROPS GROW. EXP. 28. Cautiously heat a spoonful of powdered starch in a porce lain dish, with constant stirring so that it may not burn, for the space of five minutes; it acquires a yellow, and later, a brown color. Now add thrice its bulk of water, and heat nearly to boiling. Observe that a slimy solution is formed. Pour it upon a filter; the liquid that runs through contains dextrin. To a portion add twice its bulk of alcohol ; dextrin is precipitated. To another portion, add solution of iodine ; this shows the presence of dissolved but unaltered starch. To a third portion of the filtrate add one drop of strong sulphuric acid and boil a few minutes. Test with iodine, which, as soon as all starch is transformed, will give a red instead of a blue color. Not only heat but likewise acids and ferments produce dextrins from starch and, according to some authors, from cellulose. In the sprouting of seeds, dextrin is abundantly formed from starch and hence is an ingre- dient of malb liquors. The agencies that convert starch into the dextrins easily transform the dextrins into sugars (maltose or dextrose), as will be presently noticed. The chemical composition of dry dextrin is identical with that of dry cellulose, starch, and amidulin. Inulin, C 36 H 62 36 , closely resembles starch in many points, and appears to replace that body in the roots of the American artichoke,* elecampane, dahlia, dandelion, chicory, and other plants of the same natural family (composite). It may be obtained in the form of minute white grains, which dissolve easily in hot water, and sep- arate again as the water cools. According to Bouchar.dut, the juice of the dahlia tuber, expressed in winter, becomes a semi-solid white mass after reposing some hours, from the separation of 8 per cent of inulin. Inulin, when pure, gives no coloration with iodine. It may be recognized in plants, where it occurs as a solu- tion, usually of the consistence of a thin oil, by soaking a slice of the plant in strong alcohol. Inulin is insolu- ble in this liquid, and under its influence shortly separ- * Helianthus tuberosiis, commonly known as Jerusalem artichoke, and cultivated in Europe under the name topmamhour, is a native of the Northern Mississippi States. THE VOLATILE PART OF PLANTS. 57 ates as a solid in the form of spherical granules, which may be identified with the aid of the microscope, and have an evident crystalline structure. When long heated with water it is slowly but complete- ly converted into a kind of sugar (levulose); hot dilute acids accomplish the same transformation in a short time. It is digested by animals, and doubtless has the same value for food as starch. In chemical composition, inulin, dried at 212, differs from cellulose and starch by containing for six times C 6 H 10 5 , the elements of an additional molecule of water ; C 36 H 62 36 = 6C 6 H 10 5 -f H 2 Kiliani. Levulin (C 6 H 10 5 )n coexists with inulin in the mature or frozen tubers of the artichoke, dahlia, etc., and, accord- ing to Muentz, is found in unripe rye-grain. It is a highly soluble, tasteless, gum-like substance resembling dextrin, but without effect on polarized light. It appears to be formed from inulin when the latter is long heated with water at the boiling point, or when the tubers contain- ing inulin sprout. Dilute acids readily transform it into levulose, as they convert dextrin into dextrose. SrLYCOGEN (C 6 H 10 05)n exists in the blood and mus- cles of animals in small quantity, and abundantly in the liver, especially soon after hearty eating. It is obtained by boiling minced fresh livers with water, or weak potash solution, and adding alcohol to the filtered liquid. It is A white powder which, with water, makes an opalescent solution. It is colored wine-red by iodine. Boiling di- lute sulphuric acid converts it into dextrose. With saliva, it is said to yield dextrin, maltose and dextrose. Accord- ing to late observations, glycogen occurs in the vegetable kingdom, having been identified in various fungi and in plants of the flax and the potato families. The Gums and Pectin Bodies. A number of bodies exist in the vegetable kingdom, which, from the similarity of their properties, have received the common 58 HOW CROPS GROW. designation of gums. The best known are Gum Arabic, the gums of the Peach, Cherry and Plum, Gum Traga- canth and Bassora Gum, Agar-Agar and the Mucilages of various roots, viz., of mallow and comfrey ; and of certain seeds, as those of flax and quince. Gum Arabic exudes from the stems of various species of acacia that grow in the tropical countries of the East, especially in Arabia and Egypt. It occurs in tear-like, transparent, and, in its purest form, colorless masses. These dissolve easily in their own weight of water, form- ing a viscid liquid, or mucilage, which is employed for causing adhesion between surfaces of paper, and for thickening colors in calico-printing. Gum Arabic is, however, commonly a mixture of at least two very similar gums, which are distinguished by their opposite effect on polarized light and by the differ- ent products which they yield when boiled with dilute acids. Cherry Gum. The gum which frequently forms glassy masses on the bark of cherry, plum, apricot, peach and almond trees, is a mixture in variable proportions of two gums, one of which is apparently the same as occurs in gum arabic, and is fully dissolved in cold water, while the other remains undissolved, but Bwollen to a pasty mass or jelly. Gum Tragacanth, which comes to us from Persia and Siberia, has much similarity in its properties to the insoluble part of cherry gum, as it dissolves but slightly in d ' ""JC/ JC^ water and swells up to a paste or jelly. The so-called Vegetable mucilages much resemble the insoluble part of cherry gum and are found in the seeds of flax, quince, lemon, and in various parts of many plants. THE VOLATILE PABT OF PLANTS. 59 Flax-seed mucilage is procured by soaking unbroken flaxseed in cold water, with frequent agitation, heating the liquid to boiling, strain- ing, and evaporating, until addition of alcohol separates tenacious threads from it. It is then precipitated by alcohol containing a little hydrochloric acid, and washed by the same mixture. On drying, it forms a horny, colorless, and friable mass. Fig. 13 represents a highly magnified section of the ripe flaxseed. The external cells, a, contain the dry mucilage. When soaked in water, the mucilage swells, bursts the cells, and exudes. The Pectin Bodies. The flesh of beets, turnips, and similar roots, and of most unripe fruits, as apples, peaches, plums, and berries of various kinds, contain one or several bodies which are totally insoluble in water, but which, under the action of weak acids or alkaline solu- tions, become soluble and yield substances having gummy lr gelatinous characters, that have been described under the names pectir*, pectic acid, pectosic acid, mctapectic acid, etc. Their true composition is, for the most part, not positively established. They are, however, closely related to the gums. The insoluble substance thus trans- formed into gum-like bodies, Fremy termed pectose. The gums, as they occur naturally, are mostly mix- tures. By boiling with dilute sulphuric or hydrochloric acid they are transformed into sugars. In the present state of knowledge it appears probable that the common gums, for the most part, consist of a few chemically distinct bodies, some of which have been distinguished more or less explicitly by such names as Arabin, Metarabin, Pararabin, Galactin, Paragalactin, etc. Arabin, or Arabic Acid, is obtained from some va- rieties of Gum Arabic* by mixing their aqueous solution, with acetic acid and alcohol. It is best prepared from sugar-beet pulp, out of which the juice has been ex- pressed, by heating with milk of lime ; the pulp is thereby broken down, and to a large extent dissolves. * Those sorts of commercial Gum Arabic which deviate the plane of polarization of light to the left contain arabiii in largest proportion.. 60 HOW CROPS GROW. The liquid, after separating excess of lime and adding acetic acid, is mixed with alcohol, whereupon arabin is precipitated. Arabin, thus prepared, is a milk-white mass which, while still moist, readily dissolves in water to a mucilage. It strongly reddens blue litmus and ex- pels carbonic acid from carbonates. "When dried at 212 arabin becomes transparent and has the composition C 12 H 2 20ii. Dried at 230 it becomes (by loss of a mole- cule of water) Ci 2 H 2 o0 10 , or 2 C 6 H 10 5 . Arabin forms compounds with various metals. Those with an alkali, lime, or magnesia as base are soluble iu water. Gum arabic, when burned, leaves 3 to 4 per cent of ash, chiefly carbonates of potassium, calcium and mag- nesium. Arabic acid, obtained by Fremy from beets by the foregoing method, but not in a state of purity, was described by bim as "metapectic acid." To Scheibler we owe the proof of its identity with the arabin of gum arabic. Metarabin. When arabin is dried and kept at 212 for some time, it becomes a transparent mass which is no longer freely soluble in water, but in contact therewith swells up to a gelatinous mass. This is designated metarabin by Scheibler. It is dissolved by alkalies, and thus converted into arabates, from which arabin may be again obtained. The body named pararabin by Reichardt, obtained from beet and carrot pulp by treatment with dilute hy- drochloric acid, is related to or the same as metarabin. Fremy's "pectin," obtained by similar treatment from beets, is probably impure metarabin. EXP. 34. Reduce several white turnips or beets to pulp by grating. Inclose the pulp in a piece of muslin, and wash by squeezing in water until all soluble matters are removed, or until the water comes oft nearly tasteless. Bring the washed pulp into a glass vessel, with enough dilute hydrochloric acid(l part by bulk of commercial muriatic acid to 15 parts of water) to saturate the mass, and let it stand 48 hours. Squeeze the acid liquid, filter it, and add alcohol, when " pectin " will THE VOLATILE PART OF PLANTS. 61 It may be that metarabin is identical with the "pec- tose " of the sugar beet, since both yield arabin under the influence of alkalies. It is evident that the composition found for dried arabin properly belongs to metarabin, and it is probable that arabin consists of metarabin C 12 H 22 U plus one or several molecules of water, and that metara- bin is an anhydride of arabin. Arabin and metarabin, when heated with dilute sul- phuric acid, are converted into a cry stalli 'able sugar called arabinose, C 5 H 10 5 . The gums that exude from the stems of cherry, plum and peach trees appear to con- sist chiefly of a mixture of freely soluble arabates with insoluble metarabin. Gum Tragacanth is perhaps mostly metarabin. All these gums yield, by the action of hot dilute acids, the sugar arabinose. Galactin, C 6 H 10 5 , discovered by Miiutz in the seeds of alfalfa and found in other legumes, has the appearance, solubility in water and general properties of arabin, and is probably the right-polarizing ingredient of gum arabic. Boiled with dilute acids it is converted into the sugar galactose, C 6 H 12 6 . Paragalactin, C 6 H 10 5 . In the seeds of the yellow lupin exists up to 20 per cent of a body that is insoluble in water, but dissolves by warming with alkali solutions, and when heated with dilute acids yields galactose. Ac- cording to Steiger it probably has the composition C G H 10 5 . Maxwell has shown it to exist in other leguminous seeds, viz., the pea, horse-bean (Faba vulgaris) and vetch. In the " Chinese moss," an article of food prepared in China from sea-weeds, and in the similar gum agar or "vegetable gelatine" of Japan, exists a substance which is insoluble in cold water, but with that liquid swells up to a bulky jelly, and yields galactose when heated with dilute acids. This corresponds to metarabin. Xylin, or 'Wood Gum. The wood of many decidu- ous trees, the vegetable ivory nut, the cob of Indian 62 HOW CEOPS GROW. corn and barley husks, contain 6 to 20 per cent of a sub stance insoluble in cold water, but readily taken up in cold solution of caustic soda. On adding to the solution an acid, and afterwards alcohol, a bulky white substance separates, which may be obtained dry as a white powder or a translucent gum-like mass. It dissolves very slightly in boiling water, yielding an opalescent solution. The composition of this substance was found by Thomsen to be C 6 H 10 6 . Xylin differs from pararabin and pectose in not being soluble in milk of lime. It is converted by boiling with dilute sulphuric acid into a crystallizable sugar, xylose, whose properties have been but little investigated. Flax-seed Mucilage, C 6 H 10 5 , resembles metarabin, but by action of hot dilute acids is resolved into cellulose and a gum, which latter is further transformed into dex- trose. The yield of cellulose is about four per cent. Quince-Seed Mucilage appears to be a compound of cellulose and a body like arabin. On boiling with dilute sulphuric acid it yields nearly one-third its weight of cel- lulose, together with a soluble gum and a sugar, the last being a result "of the alteration of the gum. The sugar is similar to arabinose. The Soluble Gums in Bread-grains. In the bread- tains, freely soluble gums occur often in considerable _roportion. ftVBLE OF THE PROPORTIONS (percent.) OF GUM* IN VARIOUS AIR-DRY GRAINS OR MILL PRODUCTS. (According to Von Jlibra, Die Getreidearten und das Brod.) Wheat kernel 4.50 Barley flour 6.33 Wheat flour, superfine 6.25 Spelt flour ( Triticum spclta) .. 2.48 Wheat bran 8.85 Spelt bran 12.52 Rye kernel 4.10 Rye flour 7.25 Rye bran 10.40 Barley bran 6.88 Oat meal 3.50 Rice flour 2.00 Millet flour 10.60 Maize meal 3.05 Buckwheat flour 2.85 * The " gum " in the above table (which dates from 1859), includes per- haps soluble starch and dextrin in some, if not all cases, and, accord- ing to O'Sullivan, barley, wheat and rye contain two distinct left-pol- arizing gums, which he lerms a-atnylan and b-amylctn. These occur in barley to the extent of 2.3 per cent. By action of acids they yield dextrose. THE VOLATILE PART OF PLANTS. 63 The experiments of Grouven show that gum arable is digestible by domestic animals. There is little reason to doubt that all the gums are digestible and serviceable as ingredients of the food of animals. #. The Glucoses, C 6 Hi 2 6 (or C 5 H 10 5 ), are a class of sugars having similar or identical composition, but dif- fering from each other in solubility, sweetness, melting point, crystal-form and action on polarized light. The glucoses, with one exception, contain in 100 parts : Carbon ........................... 40.00 Hydrogen ........................ 6.67 Oxygen ........................... 53.33 100.00 Levulose, or Fruit Sugar (Fructose), CHi 2 0, exists mixed with other sugars in sweet fruits, honey and molasses. Inulin and levulin are converted into this sugar by long boiling with dilute acids, or with water alone. When pure, it forms colorless crystals, which melt at 203, but is usually obtained as a syrup. Its sweetness is equal to that of saccharose. Dextrose or Grape Sugar, C 6 H 12 6 , naturally oc- curs associated with levulose in the juices of plants and in honey. Granules of dextrose separate from the juice of the grape on drying, as may be seen in old " candied " raisins. Honey often granulates, or candies, on long keeping, from the crystallization of its dextrose. Dextrose is formed from starch and dextrin by the ac- tion of hot dilute acids, in the same way that levulose is produced from inulin. In the pure state it exists as minute, colorless crystals, and is, weight for weight, but two-thirds as sweet as saccharose or cane-sugar. It fuses at 295. Dextrose unites chemically to water. Hydrated glucose, Cs occurs in commerce in an impure state as a crystalline mass, which becomes doughy at a slightly elevated temperature. This hydrate loses its crystal-water at 212. Dissolved in water, dextrose yields a syrup, which is 64 HOW CEOPS GROW. thin, and destitute of the ropiness of cane-sugar syrup. It does not crystallize (granulate) so readily as cane- sugar. EXP. 30. Mix 100 c. c. of water with 30 drops of strong sulphuric acid, and heat to vigorous boiling in a glass flask. Stir 10 grains of starch with a little water, and pour the mixture into the hot liquid, drop by drop, so as not to interrupt the boiling. The starch dissolves, and passes successively into amiduliii, dextrin, and dextrose. Continue the ebul- lition for several hours, replacing the evaporated water from time to time. To remove the sulphuric acid, add to the liquid, which may be still milky from impurities in the starch, powdered chalk, until the sour taste disappears; filter from the calcium sulphate (gypsum) that is formed, and evaporate the solution of dextrose* at a gentle heat to a syrupy consistence. On long standing it may crystallize or granulate. By this method is prepared the so-called grape-sugar, or starch-sugar of commerce, which is added to grape-juice for making a stronger wine, and is also employed for preparing syrups and imitating molasses. The syrups thus made from starch or corn are known in the trade as glucose.^ Imitation-molasses is a mixture of dextrose-syrup with some dextrin to make it " ropy." Even cellulose is convertible into dextrose by the pro- longed action of hot acids. If paper or cotton be first dissolved in strong sulphuric acid, and the solution diluted with water and boiled, the cellulose is readily transformed into dextrose. Sawdust has thus been made to yield an impure syrup, suitable for the production of alcohol. In the formation of dextrose from cellulose, starch, amidulin and dextrin, the latter substances take up the elements of water as repre- sented by the equation Starch, etc. Water. Glucose. CeH 10 O 5 + H 2 O = C 6 H 12 O 6 In this process, 90 parts of starch, etc., yield 100 parts of dextrose. Trommer's Copper test. A characteristic test for dextrose and levu- lose is found in their deportment towards an alkaline solution of cop- per, which readily yields up oxygen to these sugars, the copper being reduced to yellow cuprous hydroxide or red cuprous oxide. EXP. 31. Prepare the copper test by dissolving together in 30 c. e. of warm water a pinch of sulphate of copper and one of tartaric acid: add to the liquid, solution of caustic potash until it acquires a slip. * If the boiling has been kept up but an hour or so, the dextrose will contain dextrin, as may be ascertained by mixing a small portion of the still acid liquid with 5 times its bulk of strong alcohol, which will precipitate dextrin, but not dextrose. t Under the name glucose, the three sugars levulose, dextrose and maltose were formerly confounded together, by chemists. THE VOLATILE PART OF PLANTS. 65 pcry feel. Place in separate test tubes a few drops of solution of cane- sugar, a similar amount of the dextrin solution, obtained in Exp. 28; of solution of dextrose, from raisins, or from Exp. 30; and of molasses ; add to each a little of the copper solution, and place them in a vessel of hot water. Observe that the saccharose and dextrin suffer little or no alteration for a long time, while the dextrose and molasses shortly cause the separation of cuprous oxide. EXP. 32. Heat to boiling a little white cane-sugar with 30 c. c. of water, and 3 drops of strong sulphuric acid, in a glass or porcelain dish, for 15 minutes, supplying the waste of water as needful, and test the liquid as in the last Exp. This treatment transforms saccharose into dextrose and levulose. The quantitative estimation of the sugars and of starch is commonly based upon the reaction just described. For this purpose the alkaline copper solution is made of a known strength by dissolving a given weight of sulphate of copper, etc., in a given volume of water, and tha dextrose or levulose, or a mixture of both, being likewise made to a known volume of solution, the latter is allowed to flow slowly from a graduated tube into a measured portion of warm copper solution, until the blue color is discharged. Saccharose is first converted into dex- trose and levulose, by heating with an acid, and then examined in the same manner. Starch is transformed into dextrose by heating with hydrochloric acid or warming with saliva. The quantity of sugar stands in definite relation to the amount of copper separated, when the experiment is carried out under certain conditions. See Allihn, Jour./ilr Pr. Chemie, XXII, p. 52, 1880. Galactose, C 6 H 12 6 , is formed by treating right- polarizing gum arabic, galactin, or milk-sugar with dilute acids. It crystallizes, is sweet, melts at 289 and with nitric acid yields mucic acid (distinction from ara- binose, dextrose and levulose). Mannose (Seminose?) C 6 H 12 6 is a fermentable sugar prepared artificially by oxidation of mannite (see p. 74), and, according to E. Fischer, is probably identical with the Seminose found by Reiss as a product of the action of acids on a body existing in the seeds of coffee and in palm nuts. (Serichte, XXII, p. 365). Arabinose, C 5 Hi 5 , obtained from arabin (of left- polarizing gum arabic), and from cherry gum by action of hot dilute acids, appears in rhombic crystals. It is less sweet than cane sugar, and fuses at 320. c. The Sucroses, C^H^On, are sugars which, boiled with dilute acids, undergo chemical change by taking up the 5 66 HOW CROPS GAOW. elements of water and are thereby resolved into glucoses. In this decomposition one molecule of sucrose usually yields either two molecules of one glucose or a molecule each of two glucoses, C 12 H 22 U -f ILO = C 6 H 12 6 -f C 6 H 12 6 . Saccharose, or Cane Sugar, Ci 2 H 22 On, so called because first and chiefly prepared from the sugar-cane, is the ordinary sugar of com- merce. When pure, it is a white solid, readily soluble in water, forming a color- Fig. 14. less, ropy, and intensely sweet solution. It crystallizes in rhombic prisms (Fig. 14), which are usually small, as in granulated sugar, but in the form of rock-candy may be found an inch or more in length. The crystallized sugar obtained largely from the sugar-beet, in Europe, and that furnished in the United States by the sugar- maple and sorghum, when pure, are identical with cane- sugar. Saccharose also exists in the vernal juices of the wal- nut, birch, and other trees. It occurs in the stems of unripe maize, in the nectar of flowers, in fresh honey, in parsnips, turnips, carrots, parsley, sweet potatoes, in the stems and roots of grasses, in the seeds of the pea and bean, and in a multitude of fruits. EXP. 29. Heat cautiously a spoonful of white sugar until it melts (at 356 F.) to a clear yellow liquid. On rapid cooling, it gives a transpar- ent mass, known as barley swjar, which is employed in confectionery. At a higher heat it turns brown, froths, emits pungent vapors, and be- comes burnt sugar, or caramel, which is used for coloring soups, ale, etc. The quantity per cent of saccharose in the juice of various plants is given in the annexed table. It is, of course, variable, depending upon the variety of plant in case of cane, beet, and sorghum, as well as upon the stage of growth. SACCHAROSE IN PLANTS. Per cent. Sugar-cane, average 18 Peligot. Sugar-beet, " 10 " Sorghum 13 Collier. Maize, just flowered 3| Liidersdorff. Sugar-maple, sap, average 2i Liebig. Bed maple, " " 2J " THE VOLATILE PART OF PLANTS. 67 The composition of saccharose is the same as that of arabin, and it contains in 100 parts : Carbon 42.11 Hydrogen 6.43 Oxygen 51.46 100.00 Cane-sugar, by long boiling of its concentrated aqueous solution, and under the influence of hot dilute acids (Exp. 32) and yeast, loses its property of ready crystallization, and is converted into levulose and dextrose. According to Dubrunfaut, a molecule of cane-sugar takes up the ele- ments of a moleciile (5.26 per cent.) of water, yielding a mixture of equal parts of levulose and dextrose. This change is expressed in chemical symbols as follows : C l2 H 22 O n + H,0 = C 8 H 12 6 + C 6 H 12 6 Cane-sugar. Water. Levulose. Dextrose. This alterability on heating its solutions occasions a loss of one-third to one-half of the saccharose that is really contained in cane-juice, when this is evaporated in open pans, and is one reason why solid sugar is obtained from the sorghum in open-pan evaporation with such dif- ficulty. Molasses, sorghum syrup, and honey usually contain all three of these sugars. Honey-dew, that sometimes falls in viscid drops from the leaves of the lime and other trees, is essentially a mix- ture of the three sugars with some gum. The mannas of Syria and Kurdistan are of similar composition. Maltose, C 12 H 22 11 .H 2 0, is formed in the sprouting of seeds by the action of a ferment, called diastase, on starch. It is also prepared by treating starch or glycogen with saliva. In either case the starch (or glycogen) takes up the elements of water, 2 C 6 H 10 5 -j- H 2 = C 12 H 22 O n . Maltose in crystallizing unites with another molecule of water, which it loses at 212. Maltose, thus dried, attracts moisture with great avidity. Boiled with dilute acids one molecule of maltose yields 68 ' SOW CEOPS GROW. two molecules of dextrose, Ci 2 H 22 O n -j- n 2 = 2 C 6 H 12 6 . Maltose is also produced when starch and dextrin are heated with dilute acids, and thus appears to be an inter- mediate stage of their transformation into dextrose. Maltose is accordingly an ingredient of some commer- cial "grape-sugars" made from starch by boiling with diluted sulphuric acid. Lactose, or Milk Sugar, Ci 2 H 22 Oii -}- H 2 0, is the sweet principle of the milk of animals. It is prepared for commerce by evaporating whey (milk from which casein and fat have been separated for making cheese). In a state of purity it forms transparent, colorless crys- tals, which crackle under the teeth, and are but slightly sweet to the taste. When dissolved to saturation in water, it forms a sweet but thin syrup. Heated to 290 the crystals become water-free. Lactose is said to occur with cane-sugar in the sapo- dilla (fruit of Acliras sapotd) of tropical countries. Treatment with dilute sulphuric acid converts it into galactose and dextrose. C 12 H 22 O n + H 2 O = C 6 H 12 O 6 + C 6 H 12 O 6 Lactose. Water. Galactose. Dextrose. Raffinose, C 18 H 32 16 -f- 5 H 2 (?), first discovered by Loiseau in beet-sugar molasses, was afterwards found by Berthelot in eucalyptus manna, by Lippmann in beet- root, and by Boehm & Ritthausen in cotton-seed. It crystallizes in fine needles, and is but slightly sweet. It begins to melt at 190 with loss of crystal-water, which may be completely expelled at 212. The anhydrous sugar fuses at 236. It is more soluble in water and has higher dextrorotatory power than cane-sugar. Heated with dilute acids it yields dextrose, levulose and galactose. C 18 H 32 )8 + 2 H 2 = 3 (C 6 H 12 6 ). The Sugars in Bread- Grains. The older observers assumed the presence of dextrose in the bread-grains. THE VOLATILE PART OF PLANTS. 69 Thus, Vauquelin found, or thought he found, 8.5% of this sugar in Odessa wheat. More recently, Peligot, Mitscherlich, and Stein denied the presence of any sugar in these grains. In his work on the Cereals and Bread, (Die Getreidearten und das Brod, 1860, p. 163), Von Bibra reinvestigated this question, and found in fresh- ground wheat, etc., a sugar having some of the charac- ters of saccharose, and others of dextrose and levulose. Marcker and Kobus, in 1882, report maltose (which was unknown to the earlier observers) in sound barley, and maltose and dextrose in sprouted barley. Von Bibra found in the flour of various grains the following quanti- ties of sugar : PROPORTIONS OF SUGAR IN AIR-DRY FLOUR, BRAN, AND MEAL. Per cent. Wheat flour 2.33 Spelt flour 1.41 Wheat bran 4.30 Spelt bran 2.70 Rye flour 3.46 Rye bran 1.86 Barley meal 3.04 Barley bran 1.90 Oat meal 2.19 Rice flour 0.39 Millet flour 1.30 Maize meal 3.71 Buckwheat meal 0.91 Olucosides. There occur in the vegetable kingdom a large number of bodies, usually bitter in taste, which contain dextrose, or a similar sugar, chemically combined with other substances, or that yield it on decomposition. Salicin, from willow bark ; phloridzin, from the bark of the apple-tree root ; jalapin, from jalap ; aesculin, from the horse-chestnut, and amygdalin, in seeds of almond, peach, plum, apple, cherry, and in cherry-laurel leaves, are of this kind. The sugar may be obtained from these so-called glucosides by heating with dilute acids. The seeds of mustard contain the glucoside myronic acid united to potassium. This, when the crushed seeds are wet with water, breaks up into dextrose, mustard-oil, and acid potassium sulphate, as follows : C 10 H 18 K N S, 10 = C 6 H I2 8 + C 3 H 6 N C S + K H S O Xhe cambial juice of the conifers contains conifer in, crystallizing in 70 HOW CHOPS GROW. brilliant needles, which yields dextrose and a resin by action of dilute acid, and by oxidation produces vanillin, the flavoring principle of the vanilla bean. Mutual Transformations of the Carbhydrates. One of the most remarkable facts in the history of this group of bodies is the facility with which its members undergo mutual conversion. Some of these changes have been already noticed, but we may appropriately review them here. a. Transformations in the plant. In germinati on, the starch which is largely contained in seeds is converted into amidulin, dextrin, maltose and dextrose. It thus ac- quires solubility, and passes into the embryo to feed the young plant. Here these are again solidified as cellulose, starch, or other organic principle, yielding, in fact, the chief part of the materials for the structure of the seed- ling. At spring-time, in cold climates, the starch stored up over winter in the new wood of many trees, especially the maple, appears to be converted into the sugar which is found so abundantly in the sap, and this sugar, carried upwards to the buds, nourishes the young leaves, and is there transformed into cellulose, and into starch again. The sugar-beet root, when healthy, yields a juice con- taining 10 to 14 per cent, of saccharose, and is destitute of starch. Schacht has observed that, in a certain dis- eased state of the beet, its sugar is partially converted into starch, grains of this substance making their appear- ance. (Wilda's Centralblatt, 1863, II, p. 217.) In some years the sugar-beet yields a large amount of arabin, in others but little. The analysis of the cereal grains sometimes reveals the presence of dextrin, at others of sugar or gum. Thus, Stepf found no dextrin, but both gum and sugar in maize-meal (Jour, filr Prakt. Chem., 76, p. 92); while Fresenius, in a more recent analysis ( Vs. St., I, p. 180), obtained dextrin, but neither sugar nor gum. The sample of maize examined by Stepf contained 3.05 p. c. gum and 3.71 p. c. sugar ; that analyzed by Fresenius yielded 2.33 p. . dextrin. THE VOLATILE PART OF PLANTS. 71 Marcker & Kobus made comparative analyses of well-cured and of sprouted barley, with the following results per cent: Sound. Grown. Starch 64.10 57.98 Soluble starch 1.76 1.17 Dextrin 1.10 0.00 Dextrose 0.00 4.92 ' Maltose 3.12 7.92 The various gums are a result of the transformation of cellulose, as Mohl first showed by microscopic study. b. In the animal, the substances we have been describ- ing also suffer transformation when employed as food. During the process of digestion, cellulose, so far as it is acted upon, starch, dextrin, and probably the gums, are all converted into dextrose or other sugars, and from these, in the liver especially, glycogen is formed. c. Many of these changes may also be produced apart from physiological agency, by the action of heat, acids, and ferments, operating singly or jointly. Cellulose and starch are converted, by boiling with a ililute acid, into amidulin, dextrin, maltose and dextrose. Cellulose and starch acted upon for some time by strong nitric acid give compounds from which dextrin may be separated. Cellulose nitrate sometimes yields gum (dex- trin) by its spontaneous decomposition. A kind of gum also appears in solutions of cane-sugar or in beet-juice, when they ferment under certain conditions. Inulin and the gums yield glucoses, but no dextrin, when boiled with weak acids. d. It will be noticed that while physical and chemical agencies produce these metamorphoses mostly in one di- rection, under the influence of life they go on in either direction. In the laboratory we can in general only reduce from a higher, organized, or more complex constitution to a lower and simpler one. In the vegetable, however, all these changes, take place with the greatest facility. The Chemical Composition of the Carbhydra/tes. It HOW CROPS GROW. has already appeared that the substances just described stand very closely related to each other in chemical com- position. In the following table their composition is ex- pressed in formulae. CHEMICAL FORMULA: OF THE CARBHYDBATES. Amyloses. Dried Cellulose, C H 10 O 5 Soluble cellulose, Amyloid, } C.H 10 6 * Starch, C B H, O 5 Soluble starch, ) Amidulin, J C 6 H 10 6 * Amylodextrin, ) Dextrin, C 6 H 10 5 Inulin, 6 (C 6 H 10 6 ) + H 2 = Cgg H 62 O 31 Levulin, 2 (C 8 H 1() Og) -f- H 2 O ~ C 12 HJJ O n Glycogen, Cg H 10 O 6 Pectin, (?) Arabin, ) Metarabin, ) O /r 1 TT f\ \ I TT f\ i, ^g ljo \Jg) -}- Jlj \J C HJJ O,, Galactin, C 6 H 10 5 Paragalactin, C 6 H 10 5 Flax-seed mucilage, Cg H 10 O s Quince-seed mucilage, C 6 H 10 5 + 2 (C, H 10 6 >-H t O = C 18 HM O w Glucoses. Crystallized Levulose, C 6 H 12 6 C 6 H t2 Og Dextrose, C 6 H u O 7 and C 6 H u O 6 C 6 H 12 6 Galactose, C 6 H 12 O 6 C 6 H 12 0, Mannose, C 6 H,,0 6 CgH 12 Og Arabinose, Cg H 10 O 6 C s H 10 O s Sucroses. Saccharose, Cj2 H^ O u C 12 H M O n Maltose, C 12 H M Ou C 12 H 22 O u Lactose, C 12 H M O 12 C 12 H 22 O tl Rafflnose, C 18 H 42 O 2 i Cis H S2 O 16 As above formulated, it is seen that all these bodies, except arabinose, contain 6 atoms of carbon, or a num- ber which is some simple multiple of 6, united to as much hydrogen and oxygen as form in most cases 5, 6 or 11 molecules of water (H 2 0). Being thus composed of car- bon and the elements of water they are termed CarWiy- drates. The mutual convertibility of the carbhydrates is the * These soluble bodies when dried probably lose water which is essential U> their composition, as on drying they become insoluble. THE VOLATILE PART OF PLANTS. 73 easier to understand since it takes place by the loss or gain of several molecules of water. The formulae given are the simplest that accord with the results of analysis. In case of many of the amyloses it is probable that the above formulae should be multi- plied by 2, 4, or 6, or even more, in order to reach the true molecular weight. Isomerism. Bodies which like cellulose and dextrin, or like levu- lose and dextrose are identical in composition, and yet are character- ized by different properties and modes of occurrence, are termed isom- eric; they are examples of isomerism. These words are of Greek deri- vation, and signify of equal measure. We must suppose that the particles of isomeric bodies which are com- posed of the same kinds of matter, and in the same quantities, exist in different states of arrangement. The mason can build, from a given number of bricks and a certain amount of mortar, a simple wall, an aqueduct, a bridge or a castle. The composition of these unlike struc- tures may be the same, both in kind and quantity ; but the structures themselves differ immensely, from the fact of the diverse arrangement of their materials. In the same manner we may suppose starch to dif- fer from dextrin by a difference in the relative positions of the atoms of carbon, hydrogen, and oxygen in the molecules which compose them. By use of " structural formulae " it is sought to represent the different arrangement of atoms in the molecules of isomeric bodies. In case of substances so complex as the sugars, attempts of this kind have but recently met with success. The following formulae exhibit to the chemist the probable differences of constitution between dextrose and levulose. Dextrose. Levulose. H H H C O H H C O H H C O H C O C-H H-C-0 H H C O H H C O H H C O H H C O H _ C O H H C O H i i To those familiar with advanced Organic Chemistry the foregoing formulae, to some extent, "account for" the chemical characters of these sugars, and explain the different products which they yield under decomposing influences. APPENDIX TO THE CARBHYDRATES. Nearly related to the Carbhydrates are the following suostances : 74 HOW CROPS GROW. Mannite, C 6 H M O 6 , is abundant in the so-called manna of the apoth- ecary which exudes from the bark of several species of ash that grow in the eastern hemisphere (Ji'raxinus ornus and rotund ij'olia). It likewise exists in the sap of our fruit trees, in edible mushrooms, and sometimes is formed in the fermentation of sugar (viscous fermenta- tion). It appears in minute colorless crystals and has a sweetish taste. It may be obtained from dextrose and levulose by the action of nascent hydrogen as liberated from sodium amalgam and water, C 6 H 12 O 6 + H 2 = C 6 H 14 O 6 . Dulcite, CftHuOg, is a crystalline substance found in the common cow- wheat (Melampyrum nemorostim) and in Madagascar manna. It is obtained from milk-sugar by the action of sodium amalgam. The isomeres mannite and dulcite, when acted on by nitric acid, are converted into acids which are also isomeric. Mannite yields saccharic acid, which is also formed by treating cane-sugar, dextrose, levulose, dextrin and starch with nitric acid. Dulcite yields, by the same treat- ment, mucic acid, which is likewise obtained from arabin and other gums. Milk-sugar yields both saccharic and mucic acid. Saccharic acid is very soluble in water. Mucic acid is quite insoluble. Both have the formula C 6 Hj O 8 . The Pectin-bodies. The juice of many ripe fruits, when mixed with alcohol, yields a jelly-like precipitate which has long been known under the name of pectin. "When the firm flesh of acid winter-fruits is subjected to heat, as in baking or stewing, it sooner or later softens, becomes soluble in water and yields a gummy liquid from which by adding alcohol the same or a similar gelatinous substance is separated. Fremy supposes that in the pulp " pectose " exists which is transformed by acids and heat into pectin. Exp. 33. Express, and, if turbid, filter through muslin the juice of a ripe apple, pear, or peach. Add to the clear liquid its own bulk of alcohol. Pectin is precipitated as a stringy, gelatinous mass, which, on drying, shrinks greatly in bulk, and forms, if pure, a white sub- stance that may be easily reduced to powder, and is readily soluble in told water. Pectosic and Pectic Acids. These bodies, according to Fremy, com- pose the well-known fruit-jellies. They are both insoluble or nearly 80 in cold water, and remain suspended in it as a gelatinous mass. Pectosic acid is soluble in hot water, and is supposed to exist in those fruit-jellies which liquefy on heating but gelatinize on cooling. Pec- tic acid is stated to be insoluble in hot water. According to Fremy, pectin is changed into pectosic and pectic acids and finally into meta- pectic acid by the action of heat and during the ripening process. EXP. 35. Stew a handful of sound cranberries, covered with water, just long enough to make them soft. Observe the speedy solution of the firm pulp or "pectose." Strain through muslin. The juice contains soluble pectin, which may be precipitated from a small portion by alcohol. Keep the remaining juice heated to near the boiling point in a water bath (i. e., by immersing the vessel containing it in a larger one of boiling water). Alter a time, which is variable according to the condition of the fruit, and must be ascertained by trial, the juice on cooling or standing solidifies to a jelly, that dissolves on warming, and reappears again on cooling Fremy's pectosic acid. By further THE VOLATILE PART OF PLANTS. 75 heating, the juice may form a jelly which is permanent when hot pectic acid. Other ripe fruits, as quinces, strawberries, peaches, grapes, apples, etc., may be employed for this experiment, but in any case the time required for the juice to run through these changes cannot be pre- dicted safely, and the student may easily fail in attempting to fol- low them. Scheibler having shown that Fremy's metapectic acid of beets is arable- acid, it is probable that Fremy's pectin, pectic acid and pectosic acid of fruits, are bodies similar to or identical witli the gums* already described. The pectin bodies of fruits have not yet been certainly ob- tained in a state of purity, since the analyses of preparations by vari- ous chemists do not closely agree. The Vegetable Acids. Nearly every family of the vegetable kingdom, so far as investigated, contains one or more organic acids peculiar to itself. Those of more general occurrence which alone concern us here are few in number and must be noticed very concisely. The vegetable acids rarely occur in plants in the free state, but are for the most part united to metals or to organic bases in the form of salts. The vegetable acids consist of carboxyl, COOH, united generally to a hydrocarbon group. They are monobasic, dibasic or tribasic, according as they contain one, two or three carboxyls. The Monobasic Acids, to be mentioned here, fall into two groups, viz. : Fatty acids and Oxyfatty acids. THE FATTY ACIDS constitute a remarkable "homolo- gous series, " the names and formulae of a number of which are here given : Found in Formic acid, H, C O O H Pine needles, icd ants, guano. Acetic " C H, C O O H Vinegar and many vegetable juices. Propionic " C 2 H s COOH Yarrow-flowers. Butyric " C 3 H 7 C O O H Butter,limburgercheese,parsnip seeds. Valeric " C 4 H 9 C O O H Valerian root, old cheese. Caproic " C 5 H n COOH Butter, cocoanut oil. Oenanthylic " C H 13 C O O H (Artificial.) [fusel oil. Caprylic " C 7 H 1B COOH Butter, cocoanut oil, limburger cheese, Pelargonic " C 8 H I7 COOH Rose-geranium. Capric " C 9 II,,, COOH Butter, cocoanut oil. Umbellic " Cj H 21 C O O H Seeds of California laurel. Laurie " C u Hjg COOH Laurel oil, butter, bayberry tallow. Iridecylic M C u HjsCOOH (Artificial.) 76 HOW CHOPS GROW. Myristlc ac Isocetic Palmitic Margaric Stearic Nondecylie Arachic Medullic Belienic ld,C 1lt H 27 C O O H CH H.J9 C O O H Gu H 31 C H C 16 Hga C O O H C I7 Hag C O O H C 18 H 37 C H C 19 H 39 C O O H C 20 H 41 C O O H C 21 H 43 C H CM H 45 C H C^ H 47 C O H C 24 H 49 C H C K H 51 C H Lignoceric Hyenic Orotio Nutmeg'oil. Seeds of Jatropha. Butter, tallow, lard, palm oft. (Artificial.) Tallow, lard. (Unknown.) Butter, peanut oil. Marrow of ox. Oil of Moringa oleifera. (Unknown.) Beech-wood tar. Hyena-fat. (Unknown.) Beeswax, carnauba wax, wool-fat. It is to be observed that these fatty acids make a nearly complete series, the first of which contains one carbon and two hydrogen atoms, and the last 27 carbon and 54 hydrogen atoms, and that each of the intermediate acids differs from its neighbors by CH 2 . The first two acids in this series are thin, intensely sour, odorous liquids that mix with water in all proportions ; the third to the ninth inclusive are oily liquids whose consistency in- creases and whose sourness and solubility in water dimin- ish with their greater carbon content. The tenth and other acids are at common temperatures nearly tasteless, odorless, and fatty solids, which easily melt to oily liquids whose acid properties are but feebly manifest. Of these acids a few only require further notice. Acetic Acid, 2 H 4 2 , or CH 8 COOH, formed in the "acetic fermentation" from cider, malt, wine and whis- ky, alcohol being in each case its immediate source, exists free in vinegar to the extent of about 5 per cent. When pure, it is a strongly acid liquid, blistering the tongue, boiling at 246, and solidifying at about 60 to a white crystalline mass. In plants, acetic acid is said to exist in small proportion, mostly as acetate of potassium. Butyric Acid, C 4 H 8 2 , or CH 3 CH 2 CH 2 COOH, in the free state, occurs in rancid butter, whose disagreeable odor is largely due to its presence. In sweet butter it exists only as a glyceride or fat of agreeable qualities. THE VOLATILE PAET OF PLANTS. 77 The other acids of this series are mostly found in veg- etable and animal fats or fatty oils. (See p. 85.) OXYFATTY ACIDS. The acids of this class differ from the corresponding fatty acids by having an additional atom of oxygen, or by the substitution of OH for H in the latter. There are two acids of this class that may be briefly noticed, viz. : oxyacetic, or glycollic acid, and oxy> propionic or lactic acid. Glycollic Acid, C 2 H 4 3 or HOCH 2 COOH, exists in the juices of plants (grape-vine), and like acetic acid may be formed by oxidizing alcohol. Lactic, C 3 H 6 3 , or CH 3 CH (OH) COOH, is the acid that is formed in the souring of milk, where it is produced from the milk-sugar by a special organized ferment. It is also formed in the "lactic fermentation" of cane- sugar, starch and gum, and exists accordingly in sour- kraut and ensilage. The fatty and oxyfatty acids are monobasic, i.e., they contain one carboxyl, COOH, and each acid forms one salt only, with potassium, for instance, in which the hy- drogen of the carboxyl is replaced by the metal. Thus, potassium acetate is CH 3 COOK. The oxyfatty acids are especially prone to form anhy- drides by loss of the elements of water. Lactic acid cannot be obtained free from admixed water when its aqueous solutions are evaporated, without being partially converted into an anhydride. Gentle heat up to 270 changes it, with loss of water, into so-called lactolactic acid* C 6 H 10 5 , a solid, scarcely soluble in water, but that slowly reproduces lactic acid by contact with water, and dissolves in alkalies to form ordinary lactates. Lacto- lactic acid, heated to 290, loses water with formation of lactide,\ C 6 H 8 4 , a solid nearly insoluble in water, but also convertible into lactic acid by water, and into lactates by alkalies. ~~*~2 (C.H.OS) = C 6 H 10 5 + H,0 t C 6 H 10 6 = C S H,O 4 + H,O 78 HOW CROPS GROW. Dibasic Acids> "^The acids of this class requiring notice are COOH OOH Malonic acid, C S H 4 O<, or CH 2 Oxalic add, C.H,O 4 , or C Succinic acid, CJ^O^, or C CHj COOH H. COOH CH 2 COOH Malic acid (Oxysuccinic acid), C 4 H 6 O 5 , or CH(OH)-COOH CH(OH) COOH Tartaric acid (Dioxysuccinic CiHgOg, or acid), CH(OH) COOH The salts formed by union of these acids with metallic bases are either primary or secondary, according as the metal enters into one or two of the carboxyls. Oxalic acid, C 2 H 2 4 , exists largely in the common sorrel, and is found in greater or less quantity in nearly all plants. The pure acid presents itself in the form of color- less, brilliant, transparent crystals, not unlike Epsom salts in appearance (Fig. Fig. 15. 15), but having an intensely sour taste. Primary potassium oxalate (formerly termed acid ox- alate of potash), HOOC COOK, occasions the sour taste of the juice of sorrel, from which it may be obtained in crystals by evaporating off the water. It may also be prepared by dissolving oxalic acid in water, dividing the solution into two equal parts, neutralizing * one of these by adding solution of potash and then mixing the two solutions and evaporating until crystals form. Secondary potassium oxalate (neutral oxalate of potash), KOOC COOK, is the result of fully neutralizing oxalic acid with potash solution. It has no sour taste. Primary calcium oxalate exists dissolved in the cells of plants so long as they are in active growth. Second- ary calcium oxalate is extremely insoluble in water, and * As described in Exp. 38. THE VOLATILE PAET OF PLANTS. 79 Yery frequently occurs within the plant as microscopic crystals. These are found in large quantity in the ma- ture leaves and roots of the beet, in the root of garden rhubarb, and especially in many lichens. Secondary ammonium oxalate is employed as a test for calcium. EXP. 36. Dissolve 5 grams of oxalic acid in 50 c. c. of hot water, add. solution of ammonia or solid carbonate of ammonium until the odor of the latter slightly prevails, and allow the liquid to cool slowly. Long, needle-like crystals of ammonium oxalate separate on cooling, the compound being sparingly soluble in cold water. Preserve for future use. EXP. 37. Add to any solution of lime, as lime-water (see note, p. 20), or hard well-water, a few drops of solution of ammonium oxalate. Secondary Calcium oxalate immediately appears as a white, powdery precipitate, which, from its extreme insolubility, serves to indicate the presence of the minutest quantities of lime. Add a few drops of hydro- chloric or nitric acid to the calcium oxalate; it disappears. Hence ammonium oxalate is a test for lime only in solutions containing no free mineral acid. (Acetic and oxalic acids, however, have little effect upon the test.) Malonic acid and Succinic acid occur in plants in but small quantities. The former has been found in sugar-beets, the latter in lettuce and unripe grapes. Malic acid, C 4 H 6 5 , is the chief sour principle of ap- ples, currants, gooseberries, plums, cherries, strawberries, and most common fruits. It exists in small quantity in a multitude of plants. It is found abundantly in the gar- den rhubarb, and primary potassium malate may be ob- tained in crystals by simply evaporating the juice of the leaf-stalks of this plant. It is likewise abundant as cal- cium salt in the nearly ripe berries of the mountain ash, and in barberries. Calcium malate also occurs in con- siderable quantity in the leaves of tobacco, and is often encountered in the manufacture of maple sugar, separat- ing as a white or gray sandy powder during the evapora- tion of the sap. Pure malic acid is only seen in the chemical laboratory, and presents white, crystalline masses of an intensely sour taste. It is extremely soluble in water. 80 HOW CHOPS GROW. Tartaric acid, C 4 H 6 6 , is abundant in the grape, from the juice of which, during fermentation, it is de- posited as argol. This, on purification, yields the cream of tartar (bitartrate of potash) of commerce. Tartrates of po- tassium and calcium exist in small quan- tities in tamarinds, in the unripe berries of the mountain ash, in the berries of the sumach, in cu- cumbers, potatoes, pineapples, and many other fruits. The acid itself may be obtained in large glassy crystals (see Fig. 16), which are very sour to the taste. Of the Tribasic Acids known to occur in plants, but one need be noticed here, viz., citric acid. C H 2 C O O H C 6 H 8 T ,or C(OH)COOH C H a C O H Citric acid exists in the free state in the juice of the lemon, and in unripe tomatoes. It accompanies malic acid in the currant, gooseberry, cherry, strawberry, and raspberry. It is found in small quantity in tobacco leaves, in the tubers of the artichoke (Helianthus), in the bulbs of onions, in beet-roots, in coffee-berries, in seeds of lupin, vetch, the pea and bean, and in the needles of the fir tree, mostly as potassium or calcium salt. It also exists in cows' milk. In the pure state, citric acid forms large transparent or white crystals, very sour to the taste. Relations of the Vegetable Acids to each other, and to the Amyloses.-* Oxalic, malic, tartaric and citric acids usually occur together in our ordinary fruits, and some of them undergo mutual conversion in the living plant. According to Liebig, the unripe berries of the mountain ash contain much tartaric acid, which, as the fruit ripens, is converted into malic acid. Tartaric acid can be artificially transformed into malic acid, and this into succinic acid. When citric, malic and tartaric acids are boiled with nitric acid, or heated with caustic potash, they all yield oxalic acid. Cellulose, starch, dextrin, the sugars, yield oxalic acid when heated THE VOLATILE PART 02 PLANTS. 81 with potash or nitric acid. Commercial oxalic acid is thus made from sawdust. Gum (Arabic), sugar and starch yield tartaric acid by the action of nitric acid. Definition of Adds , Bases, and Salts. In the popular sense, an acid is any body having a sour taste. It is, in fact, true that all sour substances are acids, but all acids are not sour, some being tasteless, others bitter, and some sweet. A better characteristic of an acid is its capability of forming salts by its interaction with bases. The strong- est acids, i. e., those bodies whose acid characters are most highly developed, if soluble, so as to have any effect on the nerves of taste, are sour, viz., sulphuric acid, phos- phoric acid, nitric acid, etc. Bases are the opposite of acids. The strongest bases, when soluble, are bitter and biting to the taste, and cor- rode the skin. Potash, soda, lime, and ammonia are ex- amples. Magnesia, oxide of iron, and many other com- pounds of metals with oxygen, are insoluble bases, and hence destitute of taste. Potash, soda, and ammonia are termed alkalies ; lime and magnesia, alkali-earths. Salts are compounds that result from the mutual ac- tion of acids and bases. Thus, in Exp. 20, the salt, cal- cium phosphate, was produced by bringing together phosphoric acid, and the base, lime. In Exp. 37, cal- cium oxalate was made in a similar manner. Common salt in chemical language, sodium chloride is formed when caustic soda is mixed with hydrochloric acid, water being, in this case, produced at the same time. NaOH + HCl NaCl + H,O Sodium hydroxide. Hydrochloric acid. Sodium chloride. Water. In general, salts having a metallic base are formed by substituting the metal for the hydrogen of the acid ; or if an organic acid, for the hydrogen that is united to oxy- gen, i.e., of carboxyl, COOH. Ammonia, NH 8 , and many organic bases unite directly to acids in forming salts. 6 82 HOW CHOPS GROW. NH 3 + HC1 NH 4 C1 Ammonia. Hydrochloric acid. Ammonium chloride.* NH 3 + CH 3 COOH CH 3 COONH 4 Ammonia. Acetic acid. Ammonium Acetate. Test for acids and alkalies. Many vegetable colors are altered by sol- uble acids or soluble bases (alkalies), in such a manner as to answer the purpose of distinguishing these two classes of bodies. A solution of cochineal may be employed. It has a ruby-red color when coiicen-. trated, but, on mixing with much pure water, becomes orange or yel- lowish-orange. Acids do not affect this color, while alkalies turn it to an intense carmine or violet-carmine, which is restored to orange by acids. EXP. 38. Prepare tincture t of cochineal by pulverizing 3 grams of cochineal, and shaking frequently with a mixture of 50 c. c. of strong alcohol and 200 c. c. of water. After a day or two, pour off the clear liquid for use. To a cup of water add a few drops of strong sulphuric acid, and to an- other similar quantity add as many drops of ammonia. To these liquids add separately 5 drops of cochineal tincture, observing the coloration in each case. Divide the dilute ammonia into two portions, and pour into one of them the dilute acid, until the carmine color just passes into orange. Should excess of acid have been incautiously used, add am- monia, until the carmine reappears, and destroy it again by new por- tions of acid, added dropwise. The acid and base thus neutralize each other, and the solution contains sulphate of ammonia, but no free acid or base. It will be found that the orange-cochineal indicates very mi- nute quantities of ammonia, and the carmine-cochineal correspond- ingly small quantities of acid. In the formation of salts, the acids and bases more or less neutralize each other's properties, and their com- pounds, when soluble, have a less sour or less acrid taste, and act less vigorously on vegetable colors than the acids or bases themselves. Some soluble salts have no taste at all resembling either their base or acid, and have no effect on vegetable colors. This is true of common salt, glauber salts or sulphate of sodium, and saltpeter or nitrate of potassium. Others exhibit the properties of their base, though in a reduced degree. Carbonate of am- monium, for example, has much of the odor, taste, and * Also termed ammonic chloride, ammonia hydrochlorate, ammonia hydrochloride, and formerly muriate of ammonia. t Tinctures, in the language of the apothecary, are alcoholic solutions. Tincture of litmus (procurable of the apothecary), or of dried red cab- bage, may also be employed. Litmus is made red by soluble acids, and blue by soluble bases. With red cabbage, acids develop a purple, and the bases a green color. THE VOLATILE PART Of PLANTS. effect on vegetable colors that belong to ammonia. Car- bonate of sodium has the taste and other properties of caus- tic soda in a greatly mitigated form. On the other hand, sulphates of aluminum, iron, and copper, have slightly acid characters. 5. FATS AND OILS (WAX). We have only space here to notice this important class of bodies in a very general manner. In all plants and nearly all parts of plants we find some representatives of this group ; but it is chiefly in certain seeds that they occur most abundantly. Thus the seeds of hemp, flax, colza, cotton, bayberry, peanut, butternut, beech, hickory, almond, sunflower, etc., con- tain 10 to 70 per -cent of oil, which may be in great part removed by pressure. In some plants, as the common bayberry and the tallow-tree of Nicaragua, the fat is solid at ordinary temperatures, and must be extracted by aid of heat ; while, in most cases, the fatty matter is liquid. The cereal grains, especially oats and maize, con- tain oil in appreciable quantity. The mode of occur- rence of oil in plants is shown in Fig. 17, which repre- sents a highly magnified section of the flax-seed. The oil exists as minute, transparent globules in the cells,/. From these seeds the oil may be completely extracted by ether, benzine, or sulphide of car- bon, which dissolve all fats with readiness, but scarcely affect the other vegetable principles. Many plants yield small quanti- ties of wax, which often gives a glossy coat to their leaves, or forms a bloom upon their fruit. The lower leaves of the oat-plant at the time of blossom contain, in the dry state, 10 per cent of fat and wax (Arendt). Scarcely two Fig. 17. of these oils, fats, or kinds of wax, are exactly alike in 84 HOW CEOPS GROW. their properties. They differ more or less in taste, odor, and consistency, as well as in their chemical composition. The "oils" are the simplest in chemical composition, and have the lowest melting points. The "fats" have larger content of carbon, and higher points of fusion. The varieties of wax are most complex in composition, and have the highest melting points and greatest content of carbon. These differences are mostly gradational. In chemical constitution these bodies are alike. EXP. 39. Place a handful of fine and fresh corn or oatmeal, which has been dried for an hour or so at a heat not exceeding 212, in a bottle. Pour on twice its bulk of ether, cork tightly, and agitate frequently for half an hour. Drain off the liquid (filter, if need be) into a clean porce- lain dish, and allow the ether to evaporate. A yellowish oil remains, which, by gently warming for some time, loses the smell of ether and becomes quite pure. The fatty oils must not be confounded with the ethe- real, essential, or volatile oils, which, however, do not occur to much extent in agricultural plants. The former can not evaporate except at a high temperature, and when brought upon paper leave a permanent "grease spot." The latter readily volatilize, leaving no trace of their presence. The former, when pure, are without smell or taste. The latter usually possess marked odors, which adapt many of them to use as perfumes. In the animal body, fat (in some insects, wax) is formed or appropriated from the food, and accumulates in con- siderable quantities. How to feed an animal so as to cause the most rapid and economical fattening is one of the most important questions of agricultural chemistry. However greatly the various fats may differ in external characters, they are all mixtures of a few elementary fats. The most abundant and commonly-occurring fats, espe- cially those which are ingredients of the food of man and domestic animals e.g., tallow, olive oil, and butter con- sist mainly of three substances, which we may briefly notice. These elementary fats are Stearin, Palmitin, THE VOLATILE PART OF PLANTS. 85 and Olein,* and they consist of carbon, oxygen, and hy- drogen, the first-named element being greatly prepon- derant. Stearin is represented by the formula C 57 H 110 6 . It is the most abundant ingredient of the common fats, and exists in largest proportion in the harder kinds of tallow. EXP. 40. Heat mutton or beef tallow in a bottle that may be tightly corked, with ten times its bulk of concentrated ether, until a clear solution is obtained. Let cool slowly, when stearin will crystallize out in pearly scales. Palmitin, C 51 H 98 6 , receives its name from the palm oil, of Africa, in which it is a large ingredient. It forms a good part of butter, and is one of the chief constituents of beeswax, and of bayberry tallow. Olein, C 6 7H 1(H 6 , is the liquid ingredient of fats, and occurs most abundantly in the oils. It is prepared from olive oil by cooling down to the freezing point, when the stearin and the palmitin solidify, leaving the olein still in the liquid state. Other elementary fats, viz., butyrin, laurin, myristin, etc., occur in small quantity in butter, and in various vegetable oils. Flaxseed oil contains linolein ; castor oil, ricinolein, etc. We have already given the formulae of the principal fats, but for our purposes, a better idea of their composi- tion may be gathered from a centesimal statement, viz. : CENTESIMAL COMPOSITION OF THE ELEMENTARY FATS. Stearin. Palmitin. Olein. Carbon 76.6 75.9 77.4 Hydrogen 12.4 12.2 11.8 Oxygen 10.0 11.9 10.8 100.0 100.0 100.0 Saponification. The fats are characterized by forming soaps when heated with strong potash or soda-lye. They are by this means decomposed, and give rise to fatty * Marffarin, formerly thought to be a chemically-distinct fat, is a mix- ture of stearin and palmitin. Oleomargarine is the commercial designa- tion of an artificially-obtained mixture of fats, animal or vegetable, that has nearly the consistence of dairy buttei. 86 HOW CEOPS GROW. acidt, which remain combined with the alkali-metal, and to glycerin, a substance which acts as a base. The fats are therefore termed glycerides. EXP. 41. Heat a bit of tallow with strong solution of caustic potash until it completely disappears, and a soap, soluble in water, is obtained. To one-half the hot solution of soap, add hydrochloric acid until the lat- ter predominates. An oil will separate which gathers at the top of the liquid, and, on cooling, solidifies to a cake. This is not, however, the original fat. It has a different melting point, and a different chem- ical composition. It is composed of the three fatty acids, corres- ponding to the elementary fats from which it was produced. When saponified by the action of potash, stearin yields stearic acid, Ci 8 H 86 2 ; palmitin yields palmitic acid, C 16 H 82 2 ; and olein gives oleic acid, C 18 H 34 02.* The so-called stearin candles are a mixture of stearic and palmitic acids. The glycerin, C 8 H 8 8 , that is simul- taneously produced, remains dissolved in the liquid. Glycerin is found in commerce in a nearly pure state, as a colorless, syrupy liquid, having a pleasant, sweet taste. The chemical act of saponiflcation consists in the re-arrangement of the elements of one molecule of fat and three molecules of water into three molecules of fatty acid, and one molecule of glycerin. Palmitin. Water. Palmitic acid. Glycerin. CsiH^Oe + 3(H 2 0) = 3 (C 16 H 32 O 2 ) + C 3 H 8 O S Saponification is likewise effected by the influence of strong acids and by heating with water alone to a temperature of near 400 F. Ordinary soap is nothing more than a mixture of stearate, palmitate, and oleate of potasssium or of sodium, with or without glycerin. Com- mon soft soap consists of the potassium compounds of the above- named acids, mixed with glycerin and water. Hard soap is usually the corresponding sodium-compound, free from glycerin. When soft soap is boiled with common salt (chloride of sodium), hard soap and chlo- ride of potassium are formed by transposition of the ingredients. On cooling, hard-soap forms a solid cake upon the liquid, and the glycerin remains dissolved in the latter. Relations of Fats to Carbhydrates. The oil or fat of plants is in many cases a product of the transformation of starch or other member of the cellulose group, for the oily seeds, when immature, contain starch, which van- * Oleic acid differs from stearic acid in containing two atoms less ol hydrogen, and is one of a series that bear this relation to the fatty acids of corresponding content of carbon. THE VOLATILE PAST OF PLANTS. 87 ishes as they ripen, and in the sugar-cane the quantity of wax is said to be largest when the sugar is least abund- ant, and vice versa. In germination the oil of the seed is converted back again into starch, sugar, etc. The Estimation of Fat (including wax) is made by warming the pul- verized and dry substance repeatedly with renewed quantities of ethef , or sulphide of carbon, as long as the solvent takes up anything. On evaporating the solutions, the fat remains, and after drying thorough- ly, may be weighed. The ether extract thus obtained is usually accom- panied by a small amount of other substances, especially chlorophyll and lecithin, and is hence properly termed crude fat. PROPORTIONS OF CRUDE FAT EN VARIOUS VEGETABLE PRODUCTS. Per cent. Per cent. Meadow grass 0.8 Turnip 0.1 Red clover (green) 0.7 Wheat kernel 1.6 Cabbage 0.4 Oat Meadow hay 3.0 Maize Clover hay 3.2 Pea 1.6 7.0 .3.0 Wheat straw 1.5 Cotton se d 34.0 Oat straw 2.0 Flax Wheat bran 1.5 Colza Potato tuber 0.3 .34.0 .45.0 6. THE ALBUMINOIDS OR PROTEIDS. The bodies of this class essentially differ from those of the groups hith- erto noticed, in the fact of their containing, in addition to carbon, oxygen, and hydrogen, 15 to 18 per cent of nitrogen, with a small quantity of sulphur, and, in some cases, perhaps phosphorus. These bodies, though found in some proportion in all parts of plants, being everywhere necessary to growth, are chiefly accumulated in the seeds, especially in those of the cereal and leguminous grains. The albuminoids or proteids* that occur in plants are so similar, in many characters, to those which constitute a large portion of every animal organism, that we may advantageously consider them in connection with the latter. * The nomenclature of these substances is unavoidably confused. They are often termed nitrogenous or nitrogenized bodies, also albu minous bodies, and protein bodies. The term albuminoids has been latterly restricted, by some authors, to the substances of which gel tine is a type. The word albuminates is applied to syiitouin an7\ ai d the residue, when ki eaded with water, forms no gluten. If, however, the salt solution of gl >bulin, in contact with the flour, is largely diluted with water, the Hour will yield gluten by kneading. * Weyl and Bisehof believe that gluten does nr ,1 d rye, just as fibrin does not exist in living blc emical change during the wetting and knead ugh. According to them a strong solution of < 94 HOW CBOPS GROW. Casein. Animal Casein is the peculiar albuminoid of milk, in which it exists dissolved to the amount usually of 3 to 6 per cent. By saturating milk with magnesium sulphate the casein separates as an opaque white precipi- tate. Thus obtained it is freely soluble in water. Casein is also precipitated from milk by adding a little acetic or other acid, but is then nearly insoluble in water, has a decided acid reaction, and reddens blue litmus. The spontaneous curdling of milk, after standing at or- dinary temperatures for some time, appears to be directly due to the lactic acid which develops from milk-sugar as the milk sours. When milk is swallowed by a mamma- lian animal it curdles directly, and in the making of cheese the casein of milk is coagulated by the use of rennet, which is an infusion of tbe membrane lining the calf's stomach. Coagulated casein, though insoluble in water, dissolves in very dilute acids, and also in very dilute alkalies. The coherent cheese curd which is separated from milk by rennet is doubtless a decomposition-product of casein, and carries with it a considerable portion of the phosphates and other salts of the milk. These salts are not found in the casein precipitated by acids, being kept in solution by the latter, but casein appears to contain a small amount of phosphorus (equivalent to 0.9 per cent phosphoric oxide) in organic combination. Skim-milk cheese, when new, consists mainly of coagulated casein with a little fat. Cheese made from entire milk contains most of the fat of the milk. Exp. 50. Observe the coagulation of casein when milk is treated with a few drops of dilute hydrochloric acid. Test the curd with nitrate of mercury. EXP. 51. Boil milk with a little magnesium sulphate (Epsom salts) until it curdles. Vegetable Casein. Several distinct substances have been described as vegetable caseins. Our knowledge with regard to them is in many important respects very defi- cient. Even their elementary composition is a matter of uncertainty. THE VOLATILE PART OF PLANTS. 95 Gluten- Casein. That part of the gluten of wheat which is insoluble in cold alcohol is digested in a highly dilute solution of potash, and the clear liquid is made faintly acid by acetic acid. The curdy white precipitate thus obtained, after washing with water, alcohol and ether, and dried, is the gluten-casein of Eitthausen. It is insoluble in water, and in solutions of common salt, easily soluble in weak alkalies and coagulated by acids. Eitthausen obtained this body from wheat, rye, barley, and buckwheat. Legumin is the name that has been applied to the chief albuminoid of oats, peas, beans, lupins, vetches, and other legumes. It is extracted from the pulverized seeds by dilute alkalies, and is thrown down from these solutions by acids. From some leguminous seeds it may be partially extracted by pure water, probably because of the presence of alkali-phosphates which serve to dissolve it. It is generally mixed with conglutin, from which it may be separated by soaking in weak brine (a 5 per cent solution of common salt). Thus obtained, it is insoluble in pure water and in brine, but soluble in dilute alkalies, and has a decided acid reaction. Legumin, as existing in the horse-bean ( Viciafaba], is soluble in brine, but after solu- tion in alkali and precipitation with acids, is insoluble in salt solution. The casein, animal or vegetable, that is thrown down from salt-solution by acids is evidently a chemical compound of the original proteid with the acid (acid-proteid). EXP. 52. Prepare a solution of vegetable casein from crushed peas, almonds, or pea-nuts, by soaking them for some hours in warm water, to which a few drops of dilute ammonia-water or potash-lye has been added, and allowing the liquid to settle clear. Precipitate the casein by addition of an acid to the solution. The Chinese are said to prepare a vegetable cheese by boiling peas to a pap, straining the liquor, adding gypsum until coagulation occurs, and treating the curd thus ob- tained in the same manner as practiced with milk-cheese, 96 SOW CROPS GKOW. viz.: salting, pressing, and keeping until f.he odor and taste of cheese are developed. It is cheaply sold in the streets of Canton under the name of Tao-foo. Vegetable casein appears to occur in small quantity in the potato, and many plants ; and may be exhibited by adding a few drops of acetic acid to turnip juice, for instance, which has been freed from albumin by boiling and filtering. The Globulins are insoluble in water, but dissolve in neutral salt-solutions. Some dissolve only in salt-solu- tions of moderate strength and are thrown down from these solutions by more salt. Others are soluble in sat- urated salt-solutions. They are coagulated by heat. Some animal globulins may first be noticed. Vitellin is obtained from the yolk of eggs ; fat and pigment are first removed by ether, and the white residue is dissolved in a solution of common salt (1 of salt to 10 of water). Addition of water to the filtered solution separates the vitellin as a white, flocky mass. Paraglobulin exists in blood serum, and may be thrown down by saturating the serum with magnesium sulphate. It may be obtained in transparent microscopic disks that are probably crystalline. Its solutions in brine coagulate by heat, like albumin. Fibrinogen. When blood fresh from the veins of the horse is mixed directly with a saturated aqueous solution of magnesium sulphate, fibrinogen dissolves, and the liquid, after filtering from the red corpuscles, upon mix- ing with a saturated brine of common salt, deposits this body in white flocks, which unite to a tough, elastic mass. Its solutions in brine coagulate at a lower tem- perature than those of paraglobulin. Fresh-drawn blood, after standing a short time, coag- ulates of itself to a more or less firm clot. Under the microscope this process is seen to consist in the rapid formation of an intricate net-work of delicate threads or fibrils. These are fibrin, and come from the coagulation THE VOLATILE PART OF PLANTS. 97 of fibrinogen. Coagulation here appears to be induced by a ferment whose effect is suspended by strong saline solutions, but is renewed when these are mixed with much water. This ferment occasions decomposition of the fibrinogen, fibrin being one of the products. The fibrin-ferment is supplied from ruptured white blood- corpuscles. The chemical composition of fibrinogen and fibrin, as determined by analysis, is quite the same. Myosin. Lean beef or other dead muscle-tissue, after mincing and washing with water to remove coloring mat- ters, is soaked in 10 per cent salt-solution. Myosin dis- solves and is precipitated from the filtered brine by diluting with water. It dissolves also in dilute hydrochloric acid and in dilute potash solution. Strong hydrochloric acid converts it into syntonin. Myosin does not exist in liv- ing muscle, but is formed after death, during rigor mor- tis, from the juices of the muscles by a process of coag- ulation. Its formation is accompanied by the develop- ment of lactic and carbonic acids. Myosin is the chief ingredient of what was formerly known as muscle-fibrin. Vegetable Globulins occur abundantly in seeds where they are chief ingredients of the so-called aleurone or protein-granules. From these protein-granules, or from the pulverized seeds, the globulins are extracted by salt- solutions and by weak alkalies. The globulin which water alone extracts from many seeds is dissolved by help of the salts, which are there present. Such saline ex- tracts are coagulated by heat and thus globulins have figured, no doubt, as ''vegetable albumin." Some glob- ulins are only known in the amorphous or granular state ; others occur as crystals. Conglutin exists abundantly, according to Eitthausen, in the seeds of peach, almond, lupin, radish, pea-nut, hickory-nut, and hazel-nut, where it is usually associated with legumin. It may be separated by weak brine, in which it is invariably soluble, while legumin, after sepa- 7 98 HOW CROPS GROW. ration from alkali-solutions, is undissolved by brine. The conglutin obtained from lupins and pea-nuts differs some- what from that found in the hazel-nut, and in almond and peach seeds. Conglutin cannot be crystallized from salt-solutions, as readily happens with vegetable vitellin. Vegetable Vitellin. Applying this designation to al- buminoids which are insoluble in water, but dissolve in saturated salt-solutions, and are thence precipitated by water, we find vitellin more or less abundantly in seeds of squash, hemp, sunflower, lupin, bean, pea, Brazil-nut, castor-bean, and various other plants. It may be extracted from squash seeds by common-salt-solution (of 10 per cent) or dilute alkali. Diluting the brine with water or neutralizing the alkali with acids precipitates the vitellin, which, after washing with water, alcohol and ether, may be obtained in crystals (microscopic octahedrons) by dis- solving in warm brine and slowly cooling. From seeds of hemp and castor-bean Ritthausen obtained crystals identical in appearance and composition with those of squash seeds, but soluble in water, probably because of the presence of alkali salts. Vegetable Myosin. Weyl and Bischof consider that cereal and leguminous seeds contain or yield myosin anal- ogous to muscle-myosin, which differs from vitellin (and conglutin) in being precipitated from its solution in weak brine by saturating the same with salt. They find that wheat-flour contains but little if any proteid besides myosin, and that when this is removed from the flour by salt-solution or by very weak soda-lye or by hydrochloric acid of 0.1%, the residue is incapable of yielding gluten. Gluten is therefore a decomposition-product of myosin. These results are confirmed by the recent work of Mar- tin (Jour, of Physiology, 1887). Zoeller found that the pulp of potatoes, after starch and soluble matters had been removed by copious washings, with water, yielded to salt-solution an albuminoid which separated when thi THE VOLATILE PART OF PLANTS. 99 brine was saturated by addition of salt in excess. He also precipitated myosin from the juice of the tubers by sat- urating it with salt. The myosins are precipitated by conversion into alkali- proteids, when their brine-solutions are deprived of salt by dialysis or when these solutions are kept for some hours at 100 F. (Sidney Martin. ) Vegetable Paraglobulin is recently stated to exist in papaw-juice, and in the seeds of lequirity, Abrus preca- torius. It is distinguished from myosin by requiring a higher temperature for coagulation from salt-solutions and in not suffering conversion into an insoluble alkali- proteid by dialysis or long heating to 100 F. (Martin.) Acid-Proteids are bodies formed from proteids by the prolonged action of acids. They are insoluble in water, alcohol and brines, but easily soluble in dilute acids or alkalies, and are precipitated by neutralizing these solu- tions. The solutions of acid-proteids in acids are not co- agulable by heat. The albumins and globulins are grad- ually converted into acid-proteids by cold, highly dilute acids, and more rapidly by stronger acids and gentle heat. Syntonin is the acid-proteid resulting from solution of muscle-flesh, or myosin, in weak hydrochloric acid, and is thrown down when the solution is neutralized by an alkali, as a white gelatinous substance. Acid-proteids may exist in seeds such as the oat, lupin, pea, bean, etc., which contain so much free acid, or acid salt, that the water extract is strongly acid to test-papers. Alkali-Proteids, or Albuminates. The action of dilute alkali-solutions on most proteids converts them into bodies which, like acid-proteids, are insoluble in water and salt-solutions, but soluble in dilute acids and alkalies, and are thrown down from these solutions by neutralization. Dilute acids do not convert them into acid-proteids. Alkali-proteids are said to exist gener- ally in the young cells of the animal, and may also occur 100 SOW CROPS GROW. in plants in the alkaline juices of tlie cambium. The "vegetable caseins," viz., legumin and gluten-casein, as they occur in the alkaline juices or extracts of plants, are probably bodies of this class, and when precipitated by acids unite to the latter, forming compounds with an acid reaction. Casein of milk has been by some consid- ered to be an alkali-proteid, but is probably distinct. Proteoses and Peptones. These terms designate bodies that result from the chemical alteration of albu- minoids, under the influence of "ferments" which exist in plants, but which have been most fully studied as they occur in the digestive apparatus of animals. The albuminoids, as found in plants, are mostly insol- uble in the vegetable juices, and those which are soluble (probably because of the presence of salts, acids or alka- lies) are mostly incapable of freely penetrating the cell- membranes which inclose them, and cannot circulate in the vegetable juices, and likewise, when they become the food of animals, cannot leave the alimentary canal so as to be- come incorporated with the blood until they have been chemically changed. During the processes of animal digestion the albuminoids of whatever kind undergo solu- tion and conversion into bodies which are freely soluble in water, and rapidly penetrate the moist membranes of the intestines, and thus enter into the circulation. These bodies have been prepared for purposes of study by a partly artificial digestion, carried on in glass vessels with help of the digestive ferments obtained from the stomach (pepsin) or pancreas (trypsin) of animals.* It appears from Kuhne and Chittenden's investigations that a series of soluble and diffusible products are formed from each albuminoid with progressive diminution of carbon and increase of oxygen, and, in some cases, of nitrogen. The first-formed products are termed pro- * Reference may be had to Chittenden's Studies in Physiological Chemistry, Connecticut Acad., Vols. II and 111, 1887 and 1889. THE VOLATILE PAKT OF PLANTS. 161 teoses (albumoses, caseoses, globuloses, etc.) ; those last produced they designate peptones, but investigators are not as yet agreed as to the precise application of these terms. What have been formerly called peptones are now considered to be largely proteoses. The composition of some of these bodies may be seen from the following analyses by Chittenden and Painter : c. H. N. s. o. Casein 53.30 7.07 15.91 0.82 22.03 Protocaseose 52.50 7.15 15.73 0.96 23.86 Deuterocaseose 51.59 6.98 15.73 0.75 25.03 Casein-Peptone 49.94 6.51 16.30 0.68 26.57 Of the several products which have been analyzed and classed as proteoses and peptones, it is not certain that any one is a strictly homogeneous substance. It is more than probable that some of them are mixtures. The proper use of these names is provisional, to characterize certain evidently distinct stages of albuminoid metamor- phosis, whose exact nature can only be cleared up by further investigation. The peptones may be defined as the final products of the action of the peptic ferment. They are soluble in water and freely diffusible through animal membranes. The albumoses (or proteoses) are intermediate between the albuminoids and the peptones, being mostly soluble in water but not freely diffusible. The proteoses much resemble the albuminoids from which they are derived, not only in composition, but iu many of their properties. The peptones have less re- semblance, but appear capable of partially reverting to proteoses, as some of the latter are said to yield coagula- ble albuminoids when kept in the moist state. Weak acids and alkalies also convert the albuminoids into proteoses and peptones, and probably the acid-pro- teids, perhaps also the alkali-proteids, already mentioned, contain proteoses in admixture. Since pepsin-digestion requires the aid of a free acid and trypsin-digestion sue- 102 HOW CROPS GROW. ceeds best in presence of a free alkali, the conditions under which the proteoses of digestion are formed are in part identical with those that give rise to the acid-pro- teids and alkali-proteids. Peptones have been found in small proportions in the ivater-extract of various plants, e. g., seedlings, lupins, barley-malt, young grass, alfalfa, etc. (Vs. St., XXIV, 363, 371, 440, and XXXII, 389.) Vines has found a proteose in considerable quantity in the seeds of lupin, peony, and wheat and in the Brazil- nut and castor-bean, and considers bodies of this class to be of general occurrence in the protein-granules of plants. The proteose (hemialbumose*) from lupins has, exclu- sive of 0.81 p. c. of ash, the following composition per cent according to Vines : c. H. N. s. o. 52.58 7.24 14.87 1.52 23.79 Sidney Martin reports the existence of a proteose (hemialbumose) in the juice of the papaw or melon tree (Carica papaya) where it is associated with the fer- ment papain, which is very similar to that of the pan- creatic secretion of animals. Ferments are substances which produce or excite chemical changes in a manner as yet mostly unexplained, the ferments themselves not appreciably contributing of their own substance to the products of the processes which they set in operation. The ferments that figure in agricultural chemistry are closely related to and apparently derived from the albu- minoids, but in no case has their chemical composition been positively established. They are distinguished and characterized almost solely by the sources whence they are derived, and the effects which they produce. The Kiihne first distinguished the products of pepsin or trypsin diges- tion into hemialbumose and antialbumose, the former being converted by trypsin into amido-acids (see p. 114), the latter remaining unaltered by the digestive ferments. KUhne & Chittendon have more recently shown " hemialbumose " to be a mixture mainly of proto and dentero- albumose. THE VOLATILE PART OF PLANTS. 103 substances which the chemist can prepare, and to which he gives special designations, are doubtless mixtures, and in most cases contain but a small proportion of the real ferment, which, in a state of entire purity, is unknown. Leaven, or Yeast, which has been employed in mak- ing bread, wine and beer for many centuries, contains, or mainly consists of, a microscopic plant of very simple structure (pp. 244-5), which, when placed in a solution of cane-sugar, is able in the first place to cause the "inver- sion " of that substance into the two sugars, dextrose and levulose, and, secondly, to transform both the latter into alcohol and carbon dioxide. The " inverting " effect of yeast upon cane-sugar has been traced to a substance which can be separated from the yeast and obtained as a dry, white powder. The alcoholic fermentation requires the living yeast plant for its accomplishment. Ferments are accordingly divided into the two classes, unorganized and organized. We shall here notice briefly a few unor- ganized ferments or enzymes, as they are also termed, that have been somewhat carefully studied. Invertin is obtained from dry, pulverized yeast by heating it to 212 to coagulate albumin and then ex- tracting with warm water. The invertin dissolves, and, by addition of alcohol, is precipitated. Barth thus ob- tained a substance containing 6 per cent of nitrogen which was able, in the course of 48 hours, to transform (invert) 760 times its weight of cane-sugar. Invertin has no effect on starch or dextrin. Diastase is the name applied to a substance that may be obtained as a whitish powder from sprouted barley (malt) by extracting with dilute alcohol and precipitation with strong alcohol, which is capable of transforming 2,000 times its weight of starch, first into dextrin and finally into maltose and dextrose. The purest diastase prepared by Lintner contained 10.4 per cent, nitrogen and gave reactions for albuminoids, but it had properties besides 104 HOW CROPS GROW. its action on starch that strikingly distinguished it from the ordinary proteids. Pepsin is that ferment of the so-called gastric juice of the animal stomach which enables this organ to dissolve and "peptonize" the albuminoids of the food. It may be extracted from the inner coating of the stomach by glycerine or very dilute hydrochloric acid, and is precip- itable from these solutions by strong alcohol. Pepsin requires the presence of a free acid to dissolve the albu- minoids ; in neutral or alkaline solution it has no "di- gestive power." Trypsin is a ferment formed in the pancreas and exist- ing in the pancreatic juice which, in mammalian animals, during the digestion of food, is poured into the upper intestine, where it continues and completes the solution of albuminoids begun by the gastric juice. Trypsin acts jn neutral but most effectively in alkaline solutions ; its operation is arrested by free acids. The results of its action differ in some respects from those of pepsin. Papain. The milky juice of the Brazilian plant Car- tea papaya, or melon-tree, contains this ferment, which, like trypsin, is freely soluble in water, rapidly dissolves albuminoids, best in neutral or alkaline solutions, convert- ing them into proteoses and peptones. Papain itself, as obtained by Wurtz & Bouchut, has the properties and composition that characterize the proteoses. Ferments appear to perform very important functions in the vegetable as well as in the animal organism, and have to be referred to frequently as occasioning the con- version of insoluble into soluble substances, and of com- plex into simpler bodies. Composition of the Albuminoids. There are va- rious reasons why the exact composition of some of the bodies just described is still a subject of uncertainty. They are, in the first place, naturally mixed or associated with other matters from which it is very difficult to separate THE VOLATILE PART OF PLANTS. 105 them fully. Again, if we succeed in removing foreign substances, it must usually be done by the aid of acids, alkalies, salt-solutions, alcohol and ether, and there is reason to believe that in many cases these reagents essen- tially modify the properties and composition of the pro- teids. These bodies, in fact, as a class, are extremely susceptible to change and alter in respect to appearance, solubility, and other qualities that serve to distinguish them, without any corresponding change in chemical composition being discoverable by our methods of anal- ysis. On the other hand, the substances that have been prepared by different experimenters from the same sources, and by substantially the same methods, often show decided differences of composition. Finally, the methods of analysis used in determin- ing their composition are liable to considerable error, and, if applied to the pure substances, are scarcely delicate enough to indicate their differences with entire accuracy. In the accompanying table (p. 106) are given the most recent and trustworthy analyses of the various vegetable albuminoids, and of the corresponding substances of ani- mal origin. Referring to the analyses of Albumins we observe that the egg-albumin differs from serum-albumin in contain- ing about one per cent more of oxygen and one less of carbon, while hydrogen, nitrogen and sulphur are prac- tically the same. These two albumins have been very thoroughly studied, their difference of composition is well established, and they have positive differences in their properties, so that there can be little doubt that they are specifically distinct substances. Of the Vegeta- ble Albumins none offer any reasonable guarantee of purity. The composition of barley-albumin is near that of the animal albumins, but it contains one-third less sulphur. So far, then, as present data indicate, the veg- 106 HOW CEOPS GROW. COMPOSITION OF ALBUMINOIDS. ALBUMINS. Egg Blood serum. Wheat Barley FIBRINS. Blood Gluten-fibrin, wheat. " " maize . CASEINS. 52.2 53.1 53.1 52. 87 6.9 15.8 1.923.2 .9 16. Oil. 8 22. 2 7.217.61.620.5 .215.81.223.0 . 7 6 62 54 54.67.5l5.50.721,7 .3 7 Milk casein * Gluten-casein, wheat 152. " 62. Gluten-casein, buckwheat*. 50. Legumin, lupins 51. GLOBULINS. Paraglobulin 52. Fibrinogen, blood 52. Myosin, beef 152. Conglutin, lupin 50 . 1 hazel-nut Vitellin, squash " hemp (crystals) " Brazil-nut 51.2 51. 61. 52. GLIADIN, wheat . Analysts. Chittenden & Polton. Hammarsten. Ritthausen. 8116.9 1.1122. 5 Hammarsten. 2 16.9 1.0(20.6 ) T> mhall <, pn Rltt nausen. !)7.f 87 47 53.37.1 15.90.822.0 017.11.022.0 015.811.123.3 817.4'1.524.1 017.50.623.5 Chittenden & Painter. Ritthausen. Chittenden & Smith. I Ritthausen. Hammarsten. 77.015.81.123.4 96.916.71.322.2 8 7. 1 ' 16. 8 1.3 1 21. 9 Chittenden & Cummins. 7.0,18.71.123.0 1 47 .5 18. .0,18.70.8 22.5! I .118.10.521.9i Weyl. 52.77.1 18.00.921.3 Ritthausen. MUCEDIN, wheat 54.1 6.9 16.6 0.9 21.5 Ritthausen. See pp. 101 and 102 for analyses of Proteoses and Peptone. etable albumins are not identical with those derived from the animal. As respects the Fibrins we have already seen that there is no similarity in properties between that of blood and those obtained from gluten. The analyses of the two gluten-fibrins show either that these substances are quite distinct or that they have not yet been obtained in the pure state. The Vegetable Caseins, as analyzed by Ritthausen, are * The analysis of milk casein should include 0.9 phosphorus. The buckwheat casein contained 0.9 phosphorus, which is not included in the analysis. Whether phosphorus is an ingredient of casein, or an " impurity," is ivot perhaps positively established. THE VOLATILE PART OF PLANTS. 107 observed to contain more nitrogen by 1.2 to 1.6 per cent than exists in animal casein. Furthermore, they differ from each other so widely in carbon content (2.7 percent) as to make it highly probable that their true composition was not in all cases correctly determined. This conclusion is justified by the results of Chittenden & Smith, who have recently analyzed five different prep- arations of gluten-casein, made from wheat by Eitthau- sen's method. The average of their accordant analyses is given above.* Since nitrogen was determined by two methods (those of Dumas and Kjeldahl) these analyses would appear to establish the composition of gluten- casein, which accordingly closely agrees with that found by Ritthausen for " albumin " from barley, and with that of paraglobulin, and has the same nitrogen content as the casein of milk. The Animal Globulins agree in composition with each other as well as with animal fibrin which is formed from globulin (fibrinogen). The Vegetable Globulins are strik- ingly different in composition, containing 1.5 to 2 per cent more nitrogen and mostly but half as much sul- phur. The hazel-nut conglutin and the hemp-seed vitel- lin have the same composition. It is evident that the vegetable albuminoids, on the whole, are distinct from those of the animal, but their true composition and relations to each other, to a great extent, remain to be established. Some Mutual Relations of the Albuminoids. It was formerly supposed that these bodies are identical in com- position, the differences among the analytical results being due to foreign matters, and that they differ from each other in the same way that cellulose and starch differ, viz. : on account of different arrangement of the atoms. Afterwards, Mulder advanced the notion that the albuminoids are compounds of various proportions * Kindly communicated by the authors. 108 HOW CROPS QKOW. of hypothetical sulphur and phosphorus radicles with a common ingredient, which he termed protein ^from the Greek signifying " to take the first place," because of the great physiological importance of such a body). Hence the designations protein-bodies and proteids. The transformations which these substances are capable of undergoing sufficiently show that they are closely related, without, however, satisfactorily indicating in what manner. In the animal organism, the albuminoids of the food, of whatever name, are dissolved in the juices of the digestive organs, and pass into the blood, where they form blood albumin and globulin. As the blood nour- ishes the muscles, they are modified into the flesh-albu- minoids ; on entering the mammary system they are converted into casein, while in the appropriate part of the circulation they are formed into the albumin of the egg, or embryo. In the living plant, similar changes of place and of character occur among these substances. The Albuminoids in Animal Nutrition. We step aside for a moment from our proper plan to direct atten- tion to the beautiful adaptation of this group of organic substances to the nutrition of animals. Those bodies which we have just noticed as the animal albuminoids, together with others of similar composition, constitute a large share of the healthy animal organism, and espec- ially characterize its actual working machinery, being essential ingredients of the muscles and cartilages, as well as of the nerves and brain. They likewise exist largely in the nutritive fluids of the animal in blood and milk. So far as we know, the animal body has not the power to produce a particle of albumin, or fibrin, or casein except by the transformation of similar bodies pre- sented to it from external sources. They are hence indis- pensable ingredients of the food of animals, and were THE VOLATILE PAET OF PLANTS. 109 therefore designated by Liebig as the plastic elements of nutrition. They have also been termed the blood-build- ing or muscle-forming elements. It is, in all cases, the plant which originally constructs these substances, and places them at the disposal of the animal. The albuminoids are mostly capable of existing in the liquid or soluble state, and thus admit of distribution throughout the entire animal body, as in blood, etc. They likewise readily assume the solid condition, thus becom- ing more permanent parts of the living organism, as well as capable of indefinite preservation for food in the seeds and other edible parts of plants. Complexity of Constitution. The albuminoids are highly complex in their chemical constitution. This fact is shown as well by the multiplicity of substances which may be produced from them by destructive and decom- posing processes as by the ease with which they are broken up into other and simpler compounds. Kept in the dissolved or moist state, exposed to warm air, they speedily decompose or putrefy, yielding a large variety of products. Heated with acids, alkalies, and oxidizing agents, they mostly give origin to the same or to anal- ogous products, among which no less than twenty differ- ent compounds have been distinguished. The numbers of atoms that are associated in the mole- cules of the proteids are very great, though not in most cases even approximately known. The Haemoglobin of blood, which forms red crystals that admit of preparing in a state of great purity, contains in 100 parts C H N O S Fe 54.2 7.2 16.1 21.6 0.5 0.4 The iron (Fe) is a constant and essential ingredient, and if one atom only of this metal exist in the haemoglobin molecule, its empirical formula must be something like Ce4oHioooN"i M FeS 3 Oi9o, and its molecular weight over 14,- 000. Haemoglobin readily breaks up into a proteid and a 110 HOW CROPS GROW. much simpler red crystalline substance, Haemaeetin, yield- ing about 96 per cent of the former and 4 per cent of the latter. Haematin has approximately the formula CssHaiNiFeOs, so that the proteid, though simpler than haemoglobin, must have an extremely complicated mole- cule, and it is, accordingly, difficult to decide whether a few thousandths of the acids, bases or salts which may be associated with these bodies, as they exist in plants or pass through the hands of the chemist, are accidental or essential to their constitution. Occurrence in Plants. Aleurone. It is only in the old and virtually dead parts of a living plant that albu- minoids are ever wanting. In the young and growing organs they are abundant, and exist dissolved in the sap or juices. They are especially abundant in seeds, and here they are often deposited in an organized form, chiefly ooooa Fig. 18. Fig. 19. in grains similar to those of starch, and mostly insoluble in water. These grains of albuminoid matter are not, in many cases at least, pure albuminoids. Hartig, who first de- scribed them minutely, has distinguished them by the name aleurone, a term which we may conveniently em- ploy. By the word aleurone is not meant simply an THE VOLATILE PAKT OF PLANTS. Ill albuminoid, or mixture of albuminoids, but the organ- ized granules found in the plant, of which the albumin- oids are chief or characteristic ingredients. In Fig. 18 is represented a magnified slice through the outer cells (bran) of a husked oat kernel. The cavities of these outer cells, a, c, are chiefly occupied with very fine grains of aleurone. In one cell, b, are seen the much larger starch grains. In the interior of the oat kernel, and other cereal seeds, the cells are chiefly occu- pied with starch, but throughout grains of aleurone are more or less intermingled. Fig. 19 exhibits a section of the exterior part of a flax-seed. The outer cells, a, contain vegetable muci- lage ; the interior cells, e, are mostly filled with minute grains of aleurone, among which droplets of oil, /, are distributed. In Fig. 20 are shown some of the forms assumed by in- dividual albuminoid- grains ; a is aleurone from the seed of the vetch, J from the castor-bean, c from flax-seed, d from the fruit of the bayberry (Myrica cerifera) and e from mace (an appendage to the nutmeg, or fruit of the Myristica moscliatd). Crystalloid aleurone. It has been already remarked c Fig. 20. Fig. 21. that crystallized albuminoids exist in plants. This was first observed by Hartig (Entwickelungsgeschichte des 112 HOW CHOPS GEOW. PflanzenTceims, p. 104). In form they sometimes imitate crystals quite perfectly, Fig. 21, a; in other cases, 5, they are rounded masses, having some crystalline planes or facets. They are soft, yield easily to pressure, swell up to double their bulk when soaked in weak acids or alkalies, and their angles have not the constancy peculiar to ordinary crystals. Therefore the term crystalloids, i.e., having the likeness of crystals, has been applied to them. As Cohn first noticed (Jour, fur Prakt. Ckem., 80, p. 129), crystalloid aleurone may be observed in the outer portions of the potato tuber, in which it invariably pre- sents a cubical form. It is best found by examining the cells that adhere to the rind of a potato that has been boiled. In Fig. 21, a represents a cell from a boiled potato, in the center of which is seen the cube of aleurone. It is surrounded by the exfoliated remnants of starch- grains. In the same figure, 5 exhibits the contents of a cell from the seed of the bur reed (Sparganium ramo- sum], a plant that is common along the borders of ponds. In the center is a comparatively large mass of aleurone, having crystalloid facets. As already stated, the proteids in the crystalloid aleu- rones of hemp, castor-bean and squash have the chemical characters of globulin. The aleurone of the Brazil-nut (Bertholletia) and that of the yellow lupin contain, ac- cording to Hartig and Kubel, 9.4% of nitrogen which corresponds to some 50 or 60% of proteids. Weyl obtained from the Brazil-nut a very pure amor- phous vitellin with 18.1% of nitrogen. The vitellin of Brazil-nut, castor-bean, and of hemp and squash seeds has been recrystalized from salt solutions by Schmiedeberg, Drechsel, Griibler and Ritthausen. According to Vines, seeds of lupin and peony yield a myosin to salt-solution, and sunflower seeds, after treatment with ether to remove oil, yield a globulin with the properties of myosin, but if alcohol is used, the proteid has the character of vitellin. THE VOLATILE PART OF PLANTS. 113 Vines, who has examined the aleurone of many plants, finds it in all cases more or less soluble in water. The globulin doubtless goes into solution by help of the salts present. Vines also states that a body soluble in water, having the properties of a proteose (hemialbumose), is universally present in aleurone. Estimation of the Albuminoids. The quantitative sep- aration of these bodies, as they occur in plants, is mostly impossible in the present state of science. In many cases their collective quantity in an organic substance may be calculated with approximate accuracy from its content of nitrogen. In calculating the nutritive value of a cattle-food the albuminoids are currently reckoned as equal to its nitro- gen multiplied by 6.25. This factor is the quotient ob- tained by dividing 100 by 16, which, some 25 years ago, when cattle-feeding science began to assume its present form, there was good reason to assume was the average per cent of nitrogen in the albuminoids. As Eitthausen has insisted, this factor is too small, since the albuminoids of the cereals and of most leguminous seeds, as well as of the various oil-cakes, contain nearer 17 than 16 per cent of nitrogen, if our analyses rightly represent their com- position, and the factor 6 (= 100 -f- 16.66) would be more nearly correct. This mode of calculation only applies with strictness where all the nitrogen exists in albuminoid form. This appears to be substantially true in most seeds, but in case of young grass and roots there is usually a considerable proportion of non-albuminoid nitrogen, for which due allowance must be made. (See Amides.) * * Ammonia, NH 3 , and Nitric acid, XHO 3 . These bodies are mineral, not organic substances, and are not, on the whole, considerable ingredients of plants. They are however the principal sources of the nitrogen of vegetation, and, serving as plant-food, enter plants through their roots, chiefly from the soil, and exist within them in small quantity, and for a time, pending the conversion of their nitrogen into that of the amides and albuminoids, to whose production they are probably essential. In seeds and fruits, and in mature plants, growing in soil* 114: HOW CROPS GEOW. AVERAGE QUANTITY OF ALBUMINOIDS IN VARIOUS VEGETABLE PBODUCTS. ALBUMINOIDS = N X 6.26. American, Jenkins. German, Wolff, Maize fodder, green 1.8 1.9 Beet tops, " 2.7 3.0 Carrot tops, " 4.3 6.1 Meadow grass, in bloom 3.1 4.8 Red clover, " 3.7 4.8 White clover, " 4.0 6.6 Turnips, fresh 1.1 1.8 Carrots, " 1.1 2.2 Potatoes, " 2.2 3.4 Corn cobs, air-dry 2.3 2.3 Straw, " 3.5 4.0 Pea straw, " 7.3 10.4 Bean straw, " 10.2 16.3 Meadow hay , in bloom 7.0 15.5 Red-clover hay, " 12.5 19.7 White-clover hay, " 14.6 23.2 Buckwheat kernel, air-dry 10.0 14.4 Barley Maize Rye Oat Wheat Pea Bean .12.4 16.0 .10.6 16.0 .10.6 17.6 .11.4 17.6 .11.8 20.8 .22.4 35.8 .24.1 40.8 THE AMIDES, AMIDOACIDS, IMIDES, AND AMINES. Ammonia and the ammonium salts, so important as food to plants, and as ingredients of the atmosphere, of soils, and of manures, occur in so small proportions in living vegetation as to scarcely require notice in this work occupied with the composition of Plants. They are, however, important in connection with the amides now to be briefly described. Ammonia, an invisible gas of pungent odor which dissolves abundantly in water to form the aqua ammonia of spirits of hartshorn of the apothecary, is a compound of one atom of nitrogen with three atoms of hydrogen. It unites to acids, forming the ammonium salts : of moderate fertility, both ammonia and nitric acid, .or strictly speak- ing, ammonia-salts and nitrates, commonly occur in very small pro- portions. In roots, stems, and foliage of plants situated in soils rich in these substances, they may be present in notable quantity. The dry leaves and stems of tobacco and beets sometimes contain several per cent of nitrates. When these substances are presented to plants in abundance, especially in dry weather, they may accumulate in the roots and lower parts of the plant more rapidly than they can be assim- ilated. On the other hand, when their supply in the soil is relatively small they are so completely and rapidly assimilated as to be scarcely detectable. Their possible presence should be taken into account when it is undertaken to calculate the albuminoids of the plant from the amount of nitrogen found in its analysis. THE VOLATILE PART OF PLANTS. 115 CH S COOH + NH S C Acetic acid. Ammonia. Ammonium acetate. Amides. This term is often used as a general desig- nation for all the bodies of this section which result from the substitution of the hydrogen of ammonia by any atom or group of atoms. In a narrower sense amides are those ammonia-derivatives containing "acid-radi- cals " which are indicated in their systematic names. Acetamide, CHgCONH^ Many ammonium salts, when somewhat strongly heated, suffer decomposition into amides and water. CH S COONH 4 = CHjCONH, + H,O Ammonium acetate. Acetamide. Water. The above equation shows that acetamide is ammonia, NH 8 , or HNH 2 , one of whose hydrogens has been re- placed by the group of atoms, CH 3 CO, the acetic acid radical, so called. Acetamide is a white crystalline body. The simple amides, like acetamide, are as yet not known to exist in plants. They readily unite with water to produce ammonium salts. Carbamide, or Urea CO(NH 2 ) 2 . This substance the amide of carbonic acid CO(OH) 2 naturally occurs in considerable proportion in the urine of man and mam- malian animals. It is a white, crystalline body, with a cooling, slightly salty taste, which readily takes up the elements of water and passes into ammonium carbonate. Urea has not been found in plants, but derivatives of it in which acid radicals replace a part of its hydrogen are of common occurrence. (Guanin, allantoin.) Amidoacids are acids containing the NH 2 group as a part of the acid radical. Amidoacetic Acid, C 2 H 5 N0 2 , or CH 2 (NH 2 )COOH, is derived from acetic acid, CH 8 COOH, by the replace- ment of H in CH 8 by NH 2 . The amidoacids have not a sour, but usually a sweetish taste, and, like the amides, act both as weak acids and weak bases. Amidoacetic 116 HOW CROPS GROW. acid, also called glycocoll, has not as yet been found in plants, but exists in the scallop and probably in other shell-fish, and a compound of it, benzoylglycocoll or hip- puric acid, is a nearly constant ingredient of the urine of the horse and other domestic herbivorous animals. Betain, or trimethylglycocoll, C 5 H U N0 2 , a crystalliza- ble substance found in beet-juice, stands in close chem- ical relations to amidoacetic acid. Amidovaleric acid, CsHnNC^, occurs in ox-pancreas and in young lupin plants. Amidocaproic acid, or Leucin, C 6 H 13 N0 2 , first observed in animals, has lately been discovered in various plants. The same is true of Tyrosin, or oxyphenyl-amidopropionic acid, CsHnNOs, and of phenyl - amidopropionic acid, C 9 H U N0 2 . The above amidoacids are readily obtained as productf of decomposition of animal and vegetable albuminoids by the action of hot acids. Amidoacetic acid was thus first obtained from gelatin. Leucin and Tyrosin are com- monly prepared by boiling horn shavings with dilute sul- phuric acid ; they are also formed from vegetable albu- minoids by similar treatment and are final results of the digestion of proto- and deutero-proteoses (hemialbumose) under the action of trypsin and papain. Asparagin and Glutamin. These bodies, which are found only in plants, are amides of amidoacids, being de- rived from dibasic acids. Asparagin, the amide of amidosuccinic acid, CH(jSTH 2 )COOH CHjCOXH, has been found in very many plants, especially in those just sprouted, as in asparagus, peas, beans, etc. Aspara- gin forms white, rhombic crystals, and is very soluble in water. Glutamin, the amide of amidoglutaric acid, THE VOLATILE PART OP PLAKTS. H7 has been found, together with asparagin, in beet-juice and in squash seedlings. , The amides, when heated with water alone, and more easily in presence of strong acids and alkalies, are con- verted into ammonia and the acids from which they are derived. Thus, asparagin yields ammonia and amido- succinic acid at the boiling heat under the influence of hydrochloric acid, or of potassium hydroxide, and gluta- min is broken up by the last-named reagent at common temperatures, and by water alone at the boiling point, with formation of ammonia and amidoglutaric acid. The amidoacids are not decomposed by hot water or acids with separation of ammonia. Amidosuccinic and amidoglutaric acids result from albuminoids by boiling with dilute sulphuric acid, and by the action of bromine. The latter acid as yet has been obtained from vegetable albuminoids only, and is prepared most abundantly from gluten, and especially from mucedin. Imides, closely related to the amides, are a series of very interesting substances, into whose chemical consti- tution we cannot enter here further than to say that they contain several NH* groups, i. e., ammonia, NH 8> in which two hydrogens are replaced by hydro-carbon, or oxycarbon groups or carbon atoms. These bodies are Uric acid, C 6 H 4 N 4 3 , Adenin, C 6 H 6 N 6 , Guanin, C 5 H 5 N 5 0, Allantoin, C 4 H 6 N 4 3 , Xanthin, Hypoxanthin, C 5 H 4 lSr 4 0, Theobromin, C 7 H 8 4 2 , Caffein, C,H 10 N 4 2 , and Vernin, C 16 H 20 N 8 8 . Of these the first, so far as now known, occurs exclusively in the ani- mal. Adenin, Guanin, Allantoin, Xanthin, and Hypo- xanthin, are common to animals and plants ; the last three are exclusively vegetable. Caffein exists in coffee and tea combined with tannic acid. In the pure state it forms white, silky, fibrous crystals, and has a bitter taste. In coffee it is found to * Or its hydro-carbon derivatives. 118 HOW CROPS GROW. the extent of one-half per cent ; in tea it occurs in much larger quantity,, sometimes as high as 6 per cent. Theobromin resembles caffein in its characters. It is found in the cacao-bean, from which chocolate is man- ufactured. Vernin, discovered recently in various plants, young clover, vetches, squash-seedlings, etc., yields guanin by the action of hydrochloric acid. All these bodies stand in close chemical relations to each other, being complex imide derivatives of dioxymalonic (mesoxalic) acid. The amides and amidoacids, like ammonia, are able to combine directly with acids, are accordingly bases, but they are weak bases, because the basic quality of their ammonia is largely neutralized by the acid radicals already present in them. On the other hand, amides and ami- doacids often act as weak acids, for a portion of the hydro- gen of the jSTH 2 group is easily displaced by metals. The amides thus in fact possess in a degree the quali- ties of both the acid and of the base (ammonia) from which they are derived. They also are commonly "neu- tral" in the sense of having no sharp acid or alkaline taste or corrosive character. In vegetation amides appear as intermediate stages be- tween ammonium salts and albuminoids. They are, on the one hand, formed in growing plants from ammo- nium salts by a constructive process, and from them or by their aid, probably, the albuminoids are built up. On the other hand, in animal nutrition they are stages through which the elements of the albuminoids pass in their reversion to purely mineral matters. In germinat- ing seeds and developing buds they probably combine both these offices, being first formed in the germ from, the albuminoids of the seed, entering the young plant or shoot, and in it being reconstructed into albuminoids. Their free solubility in water and ability to penetrate moist membranes adapt them for this movement. They THE VOLATILE PART OF PLANTS. 119 temporarily accumulate in seedlings and buds, but disap- pear again as growth takes place, being. converted into albuminoids, in which transformation they require the conjunction of carbhydrates. Their ability to unite with acid as well as bases further qualifies them to take part in these physiological processes. The imides are also at once weak bases and weak acids. Uric acid and allantoin, relatively rich in oxygen, have the acid qualities best developed. Guanin and caffein, with less oxygen and more hydrogen, are commonly classed among the organic bases, as in them the basic characters are most evident. Amines. When the hydrogen of ammonia is replaced by hydrocarbon groups (radicals) such as Methyl, CH 3 , Ethyl, C 2 H 5 , Phenyl, C 6 H 5 , etc., compound ammonias or amines result which often resemble ammonia in physical and chemical characters, and some of them appear to be stronger bases than ammonia, being able to displace the latter from its combinations. Trimethylamine, N(CH 3 ) 8 , may be regarded as ammo- nia whose hydrogens are all substituted by the methyl group, CH 3 , and is a very volatile liquid having a rank, fishy odor, which may be obtained from herring pickle, and exhales from some plants, as from the foliage of Chenopo- dium vulvaria, and the flowers of Crataegus oxycantha. It is produced from detain (trimethylamidoacetic acid), by heating with potash solution, just as ammonia is formed from many amides under similar treatment. CJiolin, C 6 H 16 N0 2 , and Neurin, C 5 H 13 NO, are organic bases related to trimethylamine, which were first ob- tained from the animal. Cholin is an ingredient of the bile, and is found also in the brain and yolk of eggs, where it exists as a component of lecithin. It has latterly been discovered in the hop, lupin and pumpkin plants, and in cotton seed ; by oxidation it yields betain. Neu- rin is readily formed from cholin by the action of alka- 120 -HOW CROPS GEOW. lies and in the process of putrefaction. It is a violent poison, and is perhaps one of the ingredients which, in the seeds of the vetch and of cotton, prove injurious, or even fatal, when these seeds are too largely eaten by ani- mals. Cholin and Neurin are syrupy, highly alkaline liquids. 7. ALKALOIDS is the general designation that has been applied to the organic bases found in many plants, which are characterized in general by their poisonous and medicinal qualities. Caffein and Theobromin, already noticed, were formerly ranked as alkaloids. We may mention the following : Nicotin, Ci H 14 N 2 , is the narcotic and intensely poi- sonous principle in tobacco, where it exists in combina- tion with malic and citric acids. In the pure state it is a colorless, oily liquid, having the odor of tobacco in an extreme degree. It is inflammable and volatile, and so deadly that a single drop will kill a large dog. French tobacco contains 7 or 8 per cent; Virginia, 6 or 7 per cent; and Maryland and Havana, about 2 per cent of nicotin. Nicotin contains 17.3 per cent of nitrogen, but no oxygen. Lupinidin, C 8 Hi 5 lSr, Lupanin, CigH^^O, and Lu- pinin, C 2 iH4oN 2 2 , are bases existing in the seeds of the lupin. The first two are liquids ; the last is a crystal- line solid. They are poisonous and are believed to occa- sion the sickness which usually follows the use of lupin- seeds in cattle food. Sinapin, Ci 6 H 28 N0 6 , occurs in white mustard. When boiled with an alkali it is decomposed, yielding neurin as one product. Vicin, C 2 8H 51 Nn0 2 i, and Convicin, doH^NgO;, are crystalline bases that occur in the seeds of the vetch, with regard to whose nature and properties little is known. Avenin, C 56 H 21 NOi 8 , according to Sanson, is a sub- s.tance of alkaloidal character, existing in oats. It is said THE VOLATILE PABT OF PLANTS. 121 to be more abundant in dark than in light -colored oats, and, when present to the extent of more than nine-tenths of one per cent, to act as a decided nerve-excitant on ani- mals fed mainly on oats. Avenin is described as a gran- ular, brown, non-crystallizable substance, but neither Osborne (at the Connecticut Experiment Station) nor Wrampelmeyer (Vs. St., XXXVI, p. 299) have been able to find any evidence of the presence of such a body in oats. Morphin, Ci 7 Hi 9 N0 3 , occurs, together with several other alkaloids, in opium, the dried milky juice of the seed-vessels of the poppy cultivated in India. Its use in allaying pain and obtaining sleep and its abuse in the "opium habit" are well known. Piperin, Ci 7 H 19 N0 3 , the active principle of white and black pepper, is a white crystalline body isomeric with morphin. Quinin, C 20 H 24 !N" 2 2 , is the most important of several bases used as anti-malarial remedies obtained from the bark of various species of cinchona growing in the forests of tropical South America, and cultivated in India. Strychnin, C 2 iH 22 N 2 2 , and Brucin, C 28 H 26 N20H, ia the intensely poisonous alkaloid of nux vomica (dog button). Atropin, Ci 7 H 23 N0 8 , is the chief poisonous principle of the " Nightshade" or belladonna, and of stramonium or "Jamestown weed." Veratrin, C 32 H 49 N0 9 , is the chief toxic ingredient of the common White Hellebore, so much used as an insecticide. Solanin, C 42 H 87 NOi 6 (?), is a poisonous crystalline alkaloid found in many species of Solanum, especially in the black nightshade (Solanum nigrum). It occurs in the sprouted tubers and green fruit of the potato (Solanum tuberosum) and in the stems and leaves of the tomato (Solanum ly coper sicum). The alkaloids, so far as investigated, appear to be more 122 2*>W CROPS GBOW. or less complex dsrivativss of the bases Pyridin, C 6 H 4 N, and Quinolin, C 9 H 7 N, which are colorless, volatile liquids with sharp, unpleasant odor, produced from albu- minoids at high temperatures, and existing in smoke, bone-oil and tar. The alkaloids bear to these bases simi- lar relations to those subsisting between the amines and ammonia. 8. PHOSPHOBIZED SUBSTANCES. This class of bodies are important because of their obvious relations to the nutrition of the brain and nerve tissues of the animal, which have long been known to contain phosphorus as an essential ingredient. All our knowledge goes to show that phosphorus invariably exists in both plants and ani- mals as phosphoric acid or some derivative of this acid, or, in other words, that their phosphorus is always united to oxygen as in the phosphates, and is not directly combined to carbon, hydrogen, or nitrogen. Nuclein. This term is currently employed to desig- nate various imperfectly-studied bodies that resemble the albuminoids in many respects, but contain several per cent of phosphorus. They are easily decomposable, boiling water being able to remove from them phosphoric acid, and under the action of dilute acids they mostly yield phosphoric acid, albuminoids and hypoxanthin, C 5 H 4 N 4 0, or similar imide bases. They are very difficult of digestion by the gastric juice. The nucleins are found in the protoplasm and especially in the cell-nuclei (see p. 245), of both plants and animals, and have been ob- tained from yeast, eggs, milk, etc., by a process based on their indigestibility by pepsin. Chemists are far from agreed as to the nature or composition of the nucleins. Lecithin, C^HgoNPOg. This name applies to a num- ber of substances that have been obtained from the brain and nerve tissue of animals, eggs and milk, as well as from yeast, and the seeds of maize, peas, and wheat. The lecithins are described as white, wax-like substances, THE VOLATILE PART OF PLANTS. 123 imperfectly crystallizable, similar to protagon in their deportment toward water, and readily decomposed into cholin, glycerophosphoric acid, and one or more fatty acids. Three lecithins appear to have been identified, yielding respectively, on decomposition, stearic, palmitic, and oleic acids. The formula C 44 H 90 NP0 9 is that of distearic lecithin, which is composed of glyceryl, C 3 H 5 , united to two stearic acid radicals, and also to phosphoric acid, which again is joined to cholin, as represented by the formula \OPO Lecithin is believed to be a constant and essential in- gredient of plants and animals. Protagon, CieoHgosXePOss, discovered by Liebreich in the brain of animals, has been further studied by Gam- gee & Blankenhorn. It is a white substance that swells up with water to a gelatinous mass and finally forms an opake solution. From solution in ether or alcohol it can be easily obtained in needle-shaped crystals, whose com- position is given below. Alkalies decompose protagon into glycero-phosphoric acid, stearic and other fatty acids, and cholin or neurin. Protagon was formerly confounded with lecithin and thought to exist in plants, but its presence in the latter has not been established. Protagon. Lecithin. Carbon ......................... 66.39 65.43 Hydrogen ...................... 10.69 11.16 Nitrogen ........................ 2.39 1.73 Phosphorus .................... 1.07 3.84 Oxygen ......................... 19.46 17.&i 100.00 100.00 Knop was the first to show that the crude fat which is extracted from plants by ether contains an admixture of some substance of which phosphorus is an ingredient. In the oil obtained from the sugar-pea he found 1.25 per cent, of phosphorus, Topler afterwards examined the 124 HOW CROPS GROW. oils of a large number of seeds for phosphorus with the subjoined results : Source of Per cent, of fat. phosphorus. Lupin 0.29 Pea 1.17 Horse-bean 0.72 Vetch 0.50 Winter lentil 0.39 Horse-chestnut 0.40 Chocolate-bean none Millet " Poppy " Source of Per cent, of fat. phosphorus. Walnut trace Olive none Wheat 0.25 Barley 0.28 Rye 0.31 Oat 0.44 Flax none Colza " Mustard * It is probable that the phosphorus in these oils existed in the seeds as lecithin, or as glycerophosphoric acid, which is produced in the decomposition of lecithin. Max- well (Constitution of the Legumes), reckoning from the phosphoric acid found in the ether-extract, estimates the pea kernel to contain 0.368 per cent, the horse-bean (Faba vulgaris) 0.600 per cent, and the vetch 0.532 per cent of lecithin. Lecithin is thus calculated to make up 19.63 per cent of the crude fat of the pea, 31.54 per cent of the crude fat of the horse-bean, and 35.24 per cent of that of the vetch. Chlorophyl, i. e., leaf -green, is the name applied to the substance which occasions the green color in vegeta- tion. It is found in all those parts of most annual plants and of the annually renewed parts of perennial plants which are exposed to light. The green parts of plants usually contain chlorophyl only near their surface, and in quantity not greater than one or two per cent of the fresh vegetable substance. Chlorophyl, being soluble in ether, accompanies fat or wax when these are removed from green vegetable mat- ters by this solvent. It is soluble in alcohol and hydro- chloric and sulphuric acids, imparting to these liquids an intense green color, but it suffers alteration and decom- position so readily that it is doubtful if the composition of chlorophyl, as it exists in the living leaf, is accurately known, especially since it is there mixed with other sub- THE VOLATILE PART OF PLANTS. 135 stances, separation from which is difficult or imprac- ticable. Chlorophyllan, obtained by Hoppe-Seyler from grass, separates from its solution in hot alcohol in characteristic acicular crystals which are brown to transmitted light, and in reflected light are blackish green, with a velvety., somewhat metallic lustre. This substance has the con- sistence of beeswax, adheres firmly to glass, and at about 230 melts to a brilliant black liquid. The crystallized chlorophyllan has a composition as follows : CHLOROPHYLLAN. Carbon 73.36 Hydrogen 9.72 Nitrogen 5.68 Phosphorus 1.38 Magnesium 0.34 Oxygen 9.52 100.00 Chlorophyllan is chemically distinct from chlorophyl, as proved by its optical properties, but in what the dif- ference consists is not understood. Boiling alkali decom- poses it with formation of chlorophyllanic acid that may be obtained in blue-black crystals, and at the same time glycerophosphoric acid and cholin, the decomposi- tion-products of lecithin, are produced. Tschirch found that chlorophyllan, by treatment with zinc oxide, yields a substance whose optical properties lead to the belief that it is identical with the chlorophyl that occurs in the living plant. It was obtained as a dark-green powder, but its exact chemical composition is not known. The special interest of chlorophyl lies in the fact that it is to all appearance directly concerned in those con- structive processes by which the plant composes starch and other carbhydrates out of the mineral substances which form its food. Xanthophyl is the yellow coloring matter of leaves and of many flowers. It occurs, together with chlorophyl, in green leaves, and after disappearance of chlorophy] remains as the principal pigment of autumn foliage. 126 HOW CROPS GEOW. CHAPTER IL THE ASH OF PLANTS. II- THE INGREDIENTS OF THE A8H. As has been stated, the volatile or destructible part of plants, i. e., the part which is converted into gases or vapors under the ordinary conditions of burning, con- sists chiefly of Carbon, Hydrogen, Oxygen and Nitro- gen, together with small quantities of Sulphur and Phos- phorus. These elements, and such of their compounds as are of general occurrence in agricultural plants, viz., the Organic Proximate Principles, have been already described in detail. The non-volatile part or ash of plants also contains, or may contain, Carbon, Oxygen, Sulphur, and Phos- phorus. It is, however, in general, chiefly made up of eight other elements, whose common compounds are permanent at the ordinary heat of burning. In the subjoined table, the names of the 12 elements of the ash of plants are given, and they are grouped under two heads, the non-metals and the metals, by rea- son of an important distinction in their chemical nature. ELEMENTS OF THE ASH OF PLANTS. Non-Metals. Metals. Oxygen. Potassium. Carbon. Sodium. Sulphur. Calcium. Phosphorus. Magnesium. Silicon. Iron. Chlorine. Manganese. If to the above be added Hydrogen and Nitrogen THE ASH OF PLANTS. 127 the list includes all the elementary substances that belong to agricultural vegetation. Hydrogen is never an ingredient of the perfectly burned and dry ash of any plant. Nitrogen may remain in the ash under certain con- ditions in the form of a Cyanide (compound of Carbon and Nitrogen), as will be noticed hereafter. Besides the above, certain other elements are found, either occasion- ally in common plants, or in some particular kind of vegetation ; these are Iodine, Bromine, Fluorine, Titanium, Boron, Arsenic, Lithium, Rubidium, Barium, Aluminum, Zinc, Copper. These elements, how- ever, so far as known, have no special importance in agricultural chemistry, and mostly require no further notice. We may now complete our study of the Composition of the Plant by attending to a description of those ele- ments that are peculiar to the ash, and of those com- pounds which may occur in it. It will be convenient also to describe in this section some substances, which, although not ingredients of the ash, may exist in the plant, or are otherwise important to be considered. The Non-metallic Elements, which we shall first notice, though differing more or*less widely among them- selves, have one point of resemblance, viz., they and their compounds with each other have acid properties, i. e., they either are acids in the ordinary sense of being sour to the taste, or enact the part of acids by uniting to met- als or metallic oxides to form salts. We may, therefore, designate them as the acid elements. They are Oxygen, Sulphur, Phosphorus, Carbon, Silicon, and Chlorine. With the exception of Silicon, and the denser forms of Carbon, these elements by themselves are readily volatile. Their compounds with each other, which may occur in vegetation, are also volatile, with two exceptions, viz., Silicic and Phosphoric acids. In order that they may resist the high temperature at which ashes are formed, they must be combined with the metallic elements or their oxides as salts. 128 HOW CEOPS GEOW. Oxygen, Symbol 0, atomic weight 16, is an ingredient of the ash, since it unites with nearly all the other ele- ments of vegetation, either during the life of the plant, or in the act of combustion. It unites with Carbon, Sulphur, Phosphorus, and Silicon, forming acid bodies ; while with the metals it produces oxides, which have the characters of bases. Chlorine alone of the elements of the plant does not unite with oxygen, either in the living plant, or during its combustion. CAEBON AND ITS COMPOUNDS. Carbon, Sym. C, at. wt. 12, has been noticed already with sufficient fullness (p. 14). It is often contained as charcoal in the ashes of the plant, owing to its being en- veloped in a coating of fused saline matters, which shield it from the action of oxygen. Carbon Dioxide, commonly termed Carbonic acid, Sym. C0 2 , molecular zveight 44, is the colorless gas which causes the sparkling or effervescence of beer and soda water, and the frothing of yeast. It is formed by the oxidation of carbon, when vegeta- ble matter is burned (Exp. 6). It is, therefore, found in the ash of plants, combined with those bases which in the living organism existed in union with organic acids ; the latter being destroyed by burning. It also occurs in combination with calcium in the tissues of many plants. Its compounds with bases are carbon- ates, to be noticed presently. When a carbonate, as mar- ble or limestone, is drenched with a strong acid, like vinegar or muriatic acid, the carbon dioxide is set free with effervescence. Carbonic Acid, H 2 C0 3 , or CO(OH) 2 , mo. wt. 62. This, the carbonic acid of modern chemistry, is not known as a distinct substance, since, when set free from carbon- ates by the action of a stronger acid, it falls ^nto carbon dioxide and water : 129 CaCO 3 + 2 HC1 = CaCl, + H 2 CO 3 and H 2 CO 3 = H,O -\- CO P Carbon dioxide is also termed anhydrous carbonic acid, or again, carbonic anhydride. CYANOGEN, Sum, C 2 > T 2 . This important compound of Carbon and Ni- trogen is a gas \vlncl has an odor like that of peach-pits, and \vhic> burns 011 contact with * lighted taper with a fine purple flame. In its union with oxygen by combustion, carbon dioxide is formed, and nitro- gen set free : CjN, + 4 O = 2 C0 2 + N 2 . Cyanogen may be prepared bj" heating an intimate mixture of tw S-S G r 30 3 dd is M 0) ^ c s , Way & lomson. q g . |g- ^ fi M^H ts 3) K*i * 1 ' : o- 3 fl" j? rO- - S" p- - - - S" .R mr3 2% % 5 * OO ^ -3 S"c83 03 03 rHrH & C3 3=533 - rt r4 ^H fl^ "3 s s .3 gsssssfl g^ ^ H g tl lyl j"] "*^ f>J rH w - S mwjoosp CS CB op rH CO 1ft 00 g O} ^J5^Jc,J- C04^^ IM O 01 rH = cp o 4^ x no <-, M O Q^ O 4) >v& so g'S a+s ** Sf d 03 ^3 333 " ^"So* S... "2 O>" " " S *r H S* ' " ^'S^O O3 II w > O"" 1 r* hH > 5j3 ^fe K "3 r^W O 1O w S QJ -^ OO OOCOO O rHOCM OO HrHOCNrHOO coNcoeicocooccco CO COIN lOrHIO S=15SrfS23c15c1 1? COCiCOlOt-lMCOCOl CO 10 N CO rH T* tMTCCt-CXIOOCOt-r-l . t>3 " ^~ " S^" M ~ 3 if a a [j 1C TH rH T-H T-i T-< O 1< M 1C IO -C:?l * 1C 3 H *d* ^ o y- H"- . CO CO CO t CO OOt-OT-.tCOI-lOlOO^Ot- t~ ^* CO CO O tO CO CO 13 ^2sS5^^5^3 2 sss^ss^s 1 ,2s IClOWrtrt OOiOCO Cl^CSOCO^COlOtO id o o OOOCd O'OO O % T-I CN O T-i CJ O C7J oo* +f3 g f-X^CO^ lOCOCOCOfNCOCNCOTHj^tOCO CNCOC.OJ^OOW.N c _: tjc.~ cj ^ (NO 1CC1 t-; OtO-^OCOOOCMt-COOCOO e : c 1 ^co^= 1 co s^ = r.r,^ r * r +r4 ^^ rt T- -S - LI - CO N O t~ IO O CM IO IO O5 OOOCM le t- 10 cookie t- 5 x C 71 CN !N C- O 00 co T-I t- o co co T-I co oooco OONCCTtin-NO g J,^ C CO l-l OC CO OOT)ICOCOOOOCOt-t-t-tOt-00 t-lOCMIMCO^OOl" "^ JM * JS S 3 " S JjjCjOg^jx^icorogcoo CNScS^isC^jScS S 5 CN-^lOO IO T-I COCO t-dCOTH IO * CO CM t- O C - * P * 166 HOW CBOPS GBOW. || I| 1 I Ij ~ Oo, U v 5a d 1 * d S Pi .-*, s U 1 g 1 . Jg -53 i H .^ oj jjij 2 S 3 ^2* iJ ceoi B g*ls * ^>2 g, 5 >>s ^ >> S w ^5^ o >,- p3^ o *" ^'S S * ^ft rr" -i K_ r3 >>- - 1^ ^J * 3^ i S*" 1 ^ ir! 05 SiS^ W D PRODU CO <3> _H -H S g, "^ 1? OcS "SS-S^^ ^3 H rt ^3 "H 2 o - >> o 2 f -| | S ! ^ ~ '. ' ~ M e3" " bO 43 A " ~ Is -2iT 3 5? 5 ^ . ^ ^ rt g" 5 | 5 1 a s c^J- QQ E- ._, bo W 'S bo * as a g ^ ^ >, g 1 i|t w 1 ill te w ij 03^2 ^ c3"" ^ Q) *'* ^'Soij S 3 3 3 ^Mg S s s ^",5 ; a y, ^ ^ "j "^ 5 ^J J Q |7| r,^ Q ti 5 Q ji ^ '"^ _j 2 "3 P^ ^ h << )-J W^l l d 6 O^r-,0000 5 rt ooo-*to i-o <, 1'5 ? OrH^ -4 MOO5IM S*f | H g>oHt- Wooto^^=,=,to W 1HW*WWW il > ^ c3^^^ ^OOO^HOOC^J^ OOOOON f* o oa oo o g of >-< 02 -^ fe a "S EH 1 ^ cz i o H S jj ^.^< M (Ni-lrH CO t- rH t- OS O * p5 QQ N to M< t- W Tf CO iac^^< t-too .S 4 p g 3 OrtOlNNN 5fNt4lOMC50J rf <* H 1-1 to eo H OCO /. - ! -*^ P 10 p** w t> 2 |S ^*-, O M w W 2 c COlOi-lOiiHNt- 3 WOCJNC4 to -N d* 3 ft 2-^ M ^,5co >o^-* coMrtrt csoort edoo<-id s o g H fl ooo t-oooo ^t* oo to to o n?-i 1 || t-CON Tj 8J 10 50 OC!t-tOOOON Cl-OOOO t- .M^-^ C, O laioio g^w eodt^ritoo'oj tO rl r- ?Q g O HOCOO t~o ^.2 cc __ . S , ^jt.^1 t-oOTi< os co 10 * n &> t- 1O ^ t- O 00 tO rH 10 to mm t~f c 'o'w t-^t-^t-i otc>o p c4 c! 53 to jf 10 iS Tt< S o 23 ^.^- rt to to ^pC u PH X 43 1=1 CJlHCO H*N^ t^ ^3 C^ O CO t*CO <$* CO Ci H II THE ASH OP PLANTS. 167 e3 - Jl s ^ ! I s l a l M 5 y CS^ * rrt " ^ 3 43 3 3 - T 73 ;sg 1 g e| go ?,o| 2 5-33 ( g tJSo *E* GO .O p ^d S ** -> S s en ^ OJ^aJ of , S te S "5^ M S i. o ^ 5. S ll^ | >>>!; | ^ ll-l- >-H i- 5 i" c3 " ^|J rt ^ ^ ^ > _, to -H a S * -S - 1 1 5" l|s si 5 '3" * " bo r3i 3 fcc S 3 5" " " So ^ g s _22 ic y ^ ^gs ^ gsS o * ww o > ^ C^CO^Wqj'CQ ll.=l 'oS o O CJ o . * ^ 2 S* x S S^e-3 s Illl 1 Si^Jl^OIIg lsi^!" 3 Ill S|5H o i> -^ COO COCi ^OCiCOOOO^ ^^^ - K" 0.2 - ~" o co CO C^C^J r^CO P^ COCOCOrHt-^ ^ E>H t*^ cot cot odo 4 ^, J ^ "" H H cc 5! ^ ^ 2... i> CC ' ">H co ^^ 1 00 >o )i t- "O oo to ** co E w-2'3 3 sisi5 SS25^^!O .^lO^^Sco^ oo S 10 * eoco . w _/ *^ ' *^ ^ T ^~ y"^ 1 C S. ~ '- S "S .0 -0 = t-fOOi-iCOfl J< O 1-1 O5 00 tO *? *** oooisirotco 2 ? 5 S '"-"^ t-t-cst->cco t-t-oo^coaj S S 833S!^3 OC U j; y 4 tt.2 (TCO-* v o co o t- i-i oooooocoio t- CO ft CJfl t CO CO CO O I-H CO s|5'33 C V. CM O O ".^cOTf^io "N^ *? e idididood'fd -( ,S^^ ^.s M<0000 tOO-*-0003 10--M(Mi- co o ^fru- -f ir'^T' ^ *3 s 2 2 2^g SSSiSS S322S S ^ 55?qS12 c?^ IK jl W^i CN05COC* iocs CNO> c; c^< idv eoid id oid 3 OOWrH^CO cd <*faoco<-i 168 HOW CROPS GROW. 1 Ritter & Knop. Way & Ogston. .nalyses. not Included above. y Scluilz - Fleeth, and 1 by Metzdorff. [Wolff. Walz. Herapath. Bretschneider. AVay & Ogston. others.* Analyses. " [above, fses by Heiden not included y Ritthausen. ' Bretschneider. [berg. ' Bret schiieider & Kiillen- off man u armrodt. Analyses. L W. Average of 9 Analyses. " 4 " by " 5 " " Lowest percentage in 9 A Highest " 9 j Old Analyses by Hertwig Average of 39 Analyses. 7 b 8 3 5 4 3 8 Lowest percentage in 39 1 Highest " 39 Av rage of 4 recent Anal; ROOT. Average of 40 Analyses. " 13 " t " 11 " ' 14 " Additional Analysis by t " " " K Lowest percentage in 40 i Highest " 40 o w P5 CO 00 00 O 1C CO ^ t~toi~oi< d cr p H COOrHrtOrHCOCOOOOCO H clSrfSSSdd 1 OQ *jr 1ft to to CO to CO ~| id to * i-I co TH TATO 2353533SS pq 1 rirfclSSrfSS O pi* 2 s g'o COCO t-;OO>O coo coo t~co o - ocoooooqcoo_iC"i;oi-; p c/: 55235SSS A 0*3 o; IN t-; t-; en o SjHrteiti^^^^^S SilSSS^ ^ft 4) _, eg t- to .-( to as * ot-racsoocotoooo OOOCOOrHIOCOC*rH cn co to t-Tj. tocooNn-oooTK rf .0 co oo t- -H * O OO ^< CM H 1C CO T-H O 00 O C^ N C<) O C^ 1-H OOCSCNiC^iC* t- to co * co o Ci^HioocoiONoswoo .. rt ' ^ (N CON^< W 1-1 O 1 3 O) OD eS H O o ^ "c ^J S2 . S=M> H 3 O JHH _ fr =1 to "Oui 41 a co 5 ^i 5 ?2 o g" "5 H^ ^35 oo H i H OSCOOO5--OO30 M OSOOOSi-;'* W^,oiOU3i-O IOOl-i- o- -, ^S 2 3 g: CO CO CO y *r*i SO co 2. . 8 cc - - & o* alyses. " by Way " Wu " " Ca " " oth ge in 12 Anal.e 12 " 36 6 24 2 e g JK < O COOO H CSCJ t( So i j H H -fe+3 t, sT-i 5 o H H ~ o 1CCOCO M OJ 6 t^OON t-.t-t-.rHOO 00 * 00 O O Ol CO T 1 ? W "Jf? "^ cit-^co CMoiiCcorH ^aa -< O CM "C CO rH CM t-; CO *JJ OO O OO P2 CMrtCM rH CM CO CN?5:->CO^)CO C??CM CMCO ^5 OCO-l;COiOI~; H ee > /=> . COW 5r-t OCOC*OCJSC75 CO CO ^* r"H Grain*.... 30 12 3 46 Straw... 1327 3 7 5 LEGUMES Kernel... 44 7 5 35 Straw... 2711 7 25-39 8 ROOT CROPS Roots.... 60 3-9 612 818 Tops.... 37 316 1035 38 GRASSES In flower.. 33 4 8 8 THE ASH OF PLANTS. 171 The composition of the ash of a number of ordinary crops is concisely exhibited in the subjoined general state- ment. Ma #- jim* Phosphor- &,*,, Sulphur- rj,,.,,.^., Alkalies, nesia. Lime " ic Acid. Mlwa. ic Acid ^ Chlorine. CEREALS 2 2.5 1 5070 2.5 2 14 2 5 26 67 14 512 39 3 6-13 517 35 4 5 3. Different parts of any plant usually exhibit decided differences in the composition of their ash. This fact is made evident by a comparison of the figures of the table above, and is more fully illustrated by the following anal- yses of the parts of the mature oat-plant, by Arendt, 1 to 6 (Die Haferpflanze, p. 107), and Norton, 7 to 9 (Am. Jour. Sci., 2 Ser. 3, 318). 1 2 34 56789 Lower Middle Upper Lower Upper Ears. Chaff. Husk. Kernel Stem. Stem. Stem. Leaves. Leaves. husked. Potash 81.2 68.3 55.9 36.9 24.8 13.0) Soda 0.4 1.5 1.0 0.9 0.4 O.I) 10 - 06 12 - 4 31-7 Magnesia 2.1 3.6 3.9 3.8 3.9 8.9 1 2.3 8.6 Lime 3.6 5.3 8.6 16.7 17.2 7.3 I 9 4.3 5.3 Oxide of Iron.... 1.0 0.0 0.2 2.7 0.5 trace f 11 " 5 0.3 0.8 Phosphoric acid. 2.7 1.4 2.7 1.7 1.5 36.5 J 0.6 49.1 Sulphuric acid.. 0.0 1.3 1.1 3.2 7.5 4.9 5.3 4.3 0.0 Silica 4.1 9.3 20.4 34.0 41.8 26.0 68.0 74.1 1.8 Chlorine 8.6 11.7 7.4 1.6 2.4 3.8 3.1 1.4 0.2 The results of Arendt and Norton are not in all respects strictly com- parable, having been obtained by different methods, but serve well to establish the fact in q .icstion. We see from the above figures that the ash of the lower stem consists chiefly of potash (81%). This alkali is pre- dominant throughout the stem, but in the upper parts, where the stem is not covered by the leaf sheaths, silica and lime occur in large quantity. In the ash of the leaves, silica, potash, and lime are the principal ingredients. In the chaff and husk, silica constitutes three-fourths of the ash, while in the grain, phosphoric acid appears as the char- Exclusive of husk* 172 HOW CHOPS GROW, acteristic ingredient, existing there in connection with a large amount of potash (32%) and considerable magne- sia. Chlorine acquires its maximum (11.7%) in the mid- dle stem, but in the kernel is present in small quantity, while sulphuric acid is totally wanting in the lower stem, and most abundant in the upper leaves. Again, the unequal distribution of the ingredients of the ash is exhibited in the leaves of the sugar-beet, which have been investigated by Bretschneider ( Hoff. Jahresbe- riclit, 4, 89). This experimenter divided the leaves of 6 sugar-beets into 5 series or circles, proceeding from the outer and older leaves inward. He examined each series separately with the following results: I. II. III. IV. V. Potash 18.7 25.9 32.8 37.4 50.3 Soda 15.2 14.4 15.8 15.0 11.1 Chloride of Sodium.... 5.8 6.4 5.8 6.0 6.5 Lime 24.2 19.2 18.2 15.8 4.7 Magnesia 24.5 22.3 13.0 8.9 6.7 Oxide of Iron 1.4 0.5 0.6 0.6 0.5 Phosphoric acid 3.3 4.8 5.8 8.4 12.7 Sulphuric acid 5.4 5.6 5.6 5.2 5.9 Silica 1.5 0.8 2.7 2.1 1.5 From these data we perceive that in the ash of the leaves of the sugar-beet, potash and phosphoric acid regularly and rapidly increase in relation to the other ingredients from without inward, while lime and magnesia as rapidly diminish in the same direction. The per cent of the othef ingredients, viz., soda, chlorine, oxide of iron, sulphuric acid, and silica, remains nearly invariable throughout. Another illustration is furnished by the following anal- yes of the ashes of the various parts of the horse-chestnut tree made by Wolff (Ackerlau, 2. Anf., 134): Baric. Wood. Leaf-sterns. Leaves. Flower-stems. Calyx. Potash 12.1 25.7 46.2 27.9 63.6 61.7 Lime .76.8 42.9 21.7 29.3 9.3 12.3 Magnesia 1.7 5.0 3.0 2.6 1.3 5.9 Sulphuric acid trace trace 3.8 9.1 3.5 trace Phosphoric acid 6.0 19.2 14.8 22.4 17.1 16.6 Silica 1.1 2.6 1.0 4.9 0.7 1.7 Chlorine 2.8 6.1 12.2 5.1 4,7 2.4 THE ASH OF PLANTS. 173 Ripe Fruit. Stamens. Peta.lt. Green Fruit. Kernel. Green Brown Shell. Shell. Potash 60.7 61.2 58.7 61.7 75.9 54.6 Lime 13.8 13.6 9.8 11.5 8.6 16.4 Magnesia 3.1 3.8 2.4 0.6 1.1 2.4 Sulphuric acid trace trace 3.7 1.7 1.0 3.6 Phosphoric acid... 19.5 17.0 20.8 22.8 5.3 18.6 Silica 0.7 1.5 0.9 0.2 0.6 0.8 Chlorine 2.8 3-8 4.8 2.0 7.6 5.2 4. Similar kinds of plants, and especially the same parts of similar plants, exhibit a close general agreement in the composition of their ashes ; while plants which are un- like in their botanical characters are also unlike in the proportions of their fixed ingredients. The three plants, wheat, rye, and maize, belong, botan- ically speaking, to the same natural order, graminece, and the ripe kernels yield ashes almost identical in composi- tion. Barley and the oat are also graminaceous plants, and their seeds should give ashes of similar composition. That such is not the case is chiefly due to the fact, that, unlike the wheat, rye, and maize-kernel, the grains of barley and oats are closely invested with a husk, which forms a part of the kernel as ordinarily seen. This husk yields an ash which is rich in silica, and we can only prop- erly compare barley and oats with wheat and rye, when the former are hulled, or the ash of the hulls is taken out of the account. There are varieties of both oats and bar- ley, whose husks separate from the kernel the so-called naked or skinless oats and naked or skinless barley and the ashes of these grains agree quite nearly in composi- tion with those of wheat, rye, and maize, as may be seen from the table on page 174. By reference to the table (p. 166), it will be observed that the pea and bean kernel, together with the allied vetch and lentil (p. 171), also nearly agree in ash-com- position. So, too, the ashes of the root-crops, turnips, carrots, 174: HOW CROPS GROW. and beets, exhibit a general similarity of composition, as may be seen in the table (p. 168-9). Potash Wheat. Average of seventy-nine Analyses. .....31.3 Rye. Average of twenty-one Analyses. 28.8 Maize. Average of seven Analyses. 27.7 Skinless oats. Analysis by Fr. Scliulze. 33 4 Skinles barleys. Analysis by Fr. Schulze, 35 9 3.2 4.3 4.0 1 12.3 11.6 15 11 8 13 7 Lime 3.2 3.9 1.9 36 2 9 0.7 0.8 1 8 7 Phosphoric acid. 46.1 45.6 47.1 46 9 45 1.2 1.9 1 7 Silica 1.9 2.6 2.1 24 7 Chlorine... .. 0.2 0.7 0.1 The seeds of the oil-bearing plants likewise constitute a group whose members agree in this respect (p. 170). 5. The ash of the same species of plant is more or less variable in composition, according to circumstances. The conditions that have already been noticed as in- fluencing the proportion of ash are in general the same that affect its quality. Of these we may specially notice : a. The stage of growth of the plant. b. The vigor of its development. c. The variety of the plant or the relative development of its parts, and d. The soil or the supplies of food. a. The stage of growth. The facts that the different parts of a plant yield ashes of different composition, and that the different stages of growth are marked by the development of new organs or the unequal expansion of those already formed, are sufficient to sustain the point now in question, and render it needless to cite analytical evidence. In a subsequent chapter, wherein we shall at- tempt to trace some of the various steps in the progress- ive development of the plant, numerous illustrations will be adduced (p. 241). b. Vigor of development. Arendt (Die Haferpflanze, p. 18) selected from an oat-field a number of plants in blossom, and divided them into three parcels : 1, com- THE ASH OF PLANTS. 175 posed of very vigorous plants ; 2, of medium ; and, 3, of very weak plants. He analyzed the ashes of each parcel, with results as below : 123 Silica 27.0 39.9 42.0 Sulphuric acid 4.8 4.1 5.6 Phosphoric acid 8.2 8.5 8.8 Chlorine 6.7 5.8 4.7 Oxide of Iron 0.4 0.5 1.0 Lime 6.1 5.4 5.1 Magnesia, Potash and Soda. 45.3 34.3 30.4 Here we notice that the ash of the weak plants con- tains 15 per cent less of alkalies, and 15 per cent more of silica, than that of the vigorous ones, while the propor- tion of the other ingredients is not greatly different. Zoeller (Liebig's Erndhrung der Vegetabilien, p. 340) examined the ash of two specimens of clover which grew on the same soil and under similar circumstances, save that one, from being shaded by a tree, was less fully de- veloped than the other. Six weeks after the sowing of the seed, the clover was cut, and gave the following results on partial analysis : Shaded clover. Unshaded clover. Alkalies 54.9 36.2 Lime 14.2 22.8 Silica 5.5 12.4 c. The variety of the plant or the relative development of its parts must obviously influence the composition of the ash taken as a whole, since the parts themselves are unlike in composition. Herapath (Qu. Jour. Chem. Soc., II, p. 20) analyzed the ashes of the tubers of five varieties of potatoes, raised on the same soil and under precisely similar circum- stances. His results are as follows : White Prince's Axbridge Apple. Beauty. Kidney. Magpie. Forty-fold. Potash 69.7 65.2 70.6 70.0 62.1 Chloride of Sodium.. 2.5 Lime 3.0 1.8 5.0 5.0 3.3 Magnesia 6.5 5.5 5.0 2.1 3.5 Phosphoric acid 17.2 20.8 14.9 14.4 30.7 Sulphuric acid 3.6 6.0 4.3 7.5 7.9 Silica 0.2 176 SOW CROPS GROW. d. The soil, or the supplies of food, manures included, have the greatest influence in varying the proportions of the ash-ingredients of the plant. It is to a considerable degree the character of the soil which determines the vigor of the plant and the relative development of its parts. This condition, then, to a certain extent, in- cludes those already noticed. It is well known that oats have a great range of weight per bushel, being nearly twice as heavy, when grown on rich land, as when gathered from a sandy, inferior soil. According to the agricultural statistics of Scotland, for the year 1857 (Trans. Highland and Ag. Soc., 1857-9, p. 213}, the bushel of oats produced in some districts weighed 44 pounds per bushel, while in other districts it was as low as 35 pounds, and in one instance but 24 pounds per bushel. Light oats have a thick and bulky husk, and an ash-analysis gives a result quite unlike that of good oats. Herapath (Jour. Roy. Ag. Society, XI, p. 107) has published analyses of light oats from sandy soil, the yield being six bushels per acre, and of heavy oats from the same soil, after "warping,"* where the produce was 64 bushels per acre. Some of his results, per cent, are as follows : Light oats. Heavy oatt. Potash 9.8 13.1 Soda 4.6 7.2 Lime .'.... 6.8 4.2 Phosphoric acid 9.7 17.6 Silica 56.5 45.6 . Wolff (Jour, fur PraTct. Chem., 52, p, 103) has anal- ysed the ashes of several plants, cultivated in a poor soil, with the addition of various mineral fertilizers. The in- fluence of the added substances on the composition of the plant is very striking. The following figures comprise his results on the ash of buckwheat straw, which grew * Thickly covering with sediment from muddy tide-water. THE ASH OP PLANTS. 17? on the unmanured soil, and on the same, after applica- tion of the substances specified below : 1234 56 Unma- Chloride Nitrate Carbonate Sulphate Carbonate nured. of of of of of tedium, potash, potash, magneria. lime. Potash 31.7 21.6 39.6 40.5 28.2 23.9 Chloride of potassium.... 7.4 26.9 0.8 3.1 6.9 9.7 Chloride of sodium 4.6 3.0 3.2 3.8 3.4 1.7 Lime 15.7 14.0 12.8 11.6 14.1 18.6 Magnesia 1.7 1.9 3.3 1.4 4.7 4.2 Sulphuric acid 4.7 2.8 2.7 4.3 7.1 3.5 Phosphoric acid 10.3 9.5 6.5 8.9 10.9 10.0 Carbonic acid 20.4 16.1 27.1 22.2 20.0 23.2 Silica 3.6 4.2 4.2 4.2 4.8 5.2 100.0 100.0 100.0 100.0 100.0 100.0 It is seen from these figures that all the applications employed in this experiment exerted a manifest influ- ence, and, in general, the substance added, or at least one of its ingredients, is found in the plant in increased quantity. In 2, chlorine, but not sodium ; in 3 and 4, potash ; in 5, sulphuric acid and magnesia, and in 6, lime, are present in larger proportion than in the ash from the unmanured soil. 6. What is the normal composition of the ash of a plant ? It is evident from the foregoing facts and con- siderations that to pronounce upon the normal composi- tion of the ash of a plant, or, in other words, to ascer- tain what ash-ingredients and what proportions of them are proper to any species of plant or to any of its parts, is a matter of much difficulty and uncertainty. The best that can be done is to adopt the average of a great number of trustworthy analyses as the approximate expression of ash-composition. From such data, how- ever, we are still unable to decide what are the abso- lutely essential, and what are really accidental, ingredi- ents, or what amount of any given ingredient is essential, and to what extent it is accidental. Wolff, who appears to have first suggested that a part of the ash of plants 178 HOW CROPS GROW. may be accidental, endeavored to approach a solution of this question by comparing together the ashes of sam- ples of the same plant, cultivated under the same circum- stances in all respects, save that they were supplied with unequal quantities of readily-available ash-ingredients. The analyses of the ashes of buckwheat-stems, just quoted, belong to this investigation. Wolff showed that, by assuming the presence in each specimen of buckwheat- straw of a certain excess of certain ingredients, and de- ducting the same from the total ash, the residuary ingre- dients closely approximated in their proportions to those observed in the crop which grew in an unmanured soil. The analyses just quoted (p. 163) are here "corrected" in this manner, by the subtraction of a certain per cent of those ingredients which in each case were furnished to the plant by the fertilizer applied to it. The num- bers of the analyses correspond with those on the previ- ous page. 123456 20 p. c. ZOp.c. 25 p. c. 8.5 p. e. 16.6 p. c. Chloride Carbonate Carbonate Sulphate Carbonatet After deduction of of of of ofcalc'mand of Nothing, pptas- potas- potas- magne- magne- sium, sium. sium. slum. sium. Potash 31.7 27.0 32.5 33.5 30.6 28.0 Chloride of potassium. 7.4 9.1 1.0 3.9 7.4 11.3 Chloride of sodium... 4.6 3.8 4.0 4.7 3.7 1.9 Lime 15.7 17.3 16.0 14.5 15.3 14.6 Magnesia 1.7 2.4 4.1 1.7 2.3 2.9 Sulphuric acid 4.7 3.5 3.4 5.4 2.1 4.1 Phosphoric acid 10.3 11.7 8.1 11.2 11.8 11.7 Carbonic acid 20.4 20.1 25.9 19.8 21.6 19.3 Silica 3.6 5.2 5.2 5.3 5.2 6.1 100.0 100.0 100.0 100.0 100.0 100.0 The correspondence in the above analyses thus " cor- rected," already tolerably close, might, as Wolff remarks (loc. cit.), be made much more exact by a further correc- tion, in which the quantities of the two most variable in- gredients, viz., chlorine and sulphuric acid, should be reduced to uniformity, and the analyses then be recalcu- lated to per cent. THE ASH OF PLANTS. 179 In the first place, however, we are not warranted in assuming that the "excess" of potassium chloride, potassium carbonate, etc., deducted in the above analyses respectively, was all accidental and unnecessary to the plant, for, under the influence of an increased amount of a nutritive ingredient, the plant may not only mechani- cally contain more, but may chemically employ more in the vegetative processes. It is well proved that vegeta- tion, grown under the influence of large supplies of nitro- genous manures, contains an increased proportion of truly assimilated nitrogen as albuminoids, amido-acids, etc. The same may be equally true of the various ash- ingredients. Again, in the second place, we cannot say that in any instance the minimum quantity of any ingredient neces- sary to the vegetative acts is present, and no more. It must be remarked that these great variations are only seen when we compare together plants produced on poor soils, i. e., on those which are relatively deficient in some one or several ingredients. If a fertile soil had been employed to support the buckwheat plants in these trials, we should doubtless have had a very different result. In 1859, Metzdorf ( Wilda's CentralUatt, 1862, II, p. 367) analysed the ashes of eight samples of the red- onion potato, grown on the same field in Silesia, but dif- ferently manured. Without copying the analyses, we may state some of the most striking results. The extreme range of varia- tion in potash was 5 per cent. The ash containing the highest percentage of potash was not, however, obtained from potatoes that had been manured with 50 pounds of this substance, but from a parcel to which had been ap- plied a poudrette containing less than three pounds of potash for the quantity used. The unmanured potatoes were relatively the richest in 180 HOW CROPS GROW, lime, phosphoric acid, and sulphuric aeid, although sev- eral parcels were copiously treated with manures contain- ing considerable quantities of these substances. These facts are of great interest in reference to the theory of the action of manures. 7. To what extent is each ash-ingredient essential, and how far may it be accidental ? Before chemical analysis had arrived at much perfection, it was believed that the ashes of the plant were either unessential to growth, or else were the products of growth were gener- ated by the plant. Since the substances found in ashes are universally dis- tributed over the earth's surface, and are invariably pres- ent in all soils, it is not possible, by analysis of the ash of plants growing under natural conditions, to decide whether any or several of their ingredients are indispen- sable to vegetative life. For this purpose it is necessary to institute experimental inquiries, and these have been prosecuted with great painstaking, and with highly val- uable results. Experiments in Artificial Soils. The Prince Salm- Horstmar, of Germany, was one of the first and most laborious students of this question. His plan of experi- ment was the following : The seeds of a plant were sown in a soil-like medium (sugar-charcoal, pulverized quartz, purified sand) which was as thoroughly as possible freed from the substance whose special influence on growth was the subject of study. All other substances presum- ably necessary, and. all the usual external conditions of growth (light, warmth, moisture, etc.), were supplied. The results of 195 trials thus made with oats, wheat, barley, and colza, subjected to the influence of a great variety of artificial mixtures, have been described, the most important of which will shortly be given. Experiments in Solutions. Water-Culture. Sachs, W. Knop, Stohmann, Nobbe, Siegert, and others THE ASH OF PLAKTS. 181 have likewise studied this subject. Their method was like that of Prince Salm-Horstmar, except that the plants were made to germinate and grow independently of any soil; and, throughout the experiment, had their roots im- mersed in water, containing in solution or suspension the substances whose action was to be observed. Water-Culture has recently contributed so much to our knowledge of the conditions of vegetable growth, that some account of the mode of conducting it may be prop- erly given in this place. Cause a num- ber of seeds of the plant it is desired to experiment upon to germinate in moist blotting-paper, and, when the roots have become an inch or two in length, select the strongest seedlings, and support them so that the roots shall be immersed in water, while the seeds themselves shall be just above the surface of the liquid. For this purpose, in case of a single maize plant, for example, provide a quart cylinder or bottle with a wide mouth, to which a cork is fitted, as in Fig. 22. Cut a vertical notch in the cork to its center, and fix therein the stem of the seedling by packing with cotton. The cork thus serves as a sup- port of the plant. Fill the jar with pure water to such a height that when the cork is brought to its place, the seed, 8, shall be a little above the liquid. If the endosperm or cotyledons dip into the water, they will speedily mould and rot ; they require, however, to be kept in a moist atmosphere. Thus arranged, suitable warmth, ventilation, and illumination alone are requi- site to continue the growth until the nutriment of the seed Fig. 281 182 HOW CHOPS GBOW. is nearly exhausted. As regards illumination, this should be as full as possible, for the foliage ; but the roots should be protected from it, by enclosing the vessel in a shield of black paper, as, otherwise, minute parasitic algae would in time develop upon the roots, and disturb their functions. For the first days of growth, pure distilled water may ad- vantageously surround the roots, but, when the first green leaf appears, they should be placed in the solution whose nutritive power is to be tested. The temperature should be properly proportioned to the light, in imitation of what is observed in the skillful management of conservatory or house-plants. The experimenter should first learn how to produce large and well-developed plants by aid of an appropriate liquid, before attempting the investigation of other prob- lems. For this purpose, a solution or mixture must be prepared, containing in proper proportions all that the plant requires, save what it can derive from the atmos- phere. The experience of Nobbe and Siegert, Knop, Wolff, and others,* supplies valuable information on this point. Wolff has obtained striking results with a variety of plants in using a solution made essentially as follows: Place 20 grams of the fine powder of well-burned bones with a half pint of water in a large glass flask, heat to boil- ing, and add nitric acid cautiously in quantity just suffi- cient to dissolve the bone-ash. In order to remove any injurious excess of nitric acid, pour into the boiling liq- uid a solution of pure potassium carbonate until a slight permanent turbidity is produced; then add 11 grams of potassium nitrate, 7 grams of crystallized magnesium sul- phate, and 3 grams of potassium chloride, with water enough to make the solution up to the bulk of one liter. Wolff's solution, thus prepared, contains in 1000 parts as follows, exclusive of iron: * See especially Tollens (Hennebery's Jour.filr Landurlrthschaft, 1882, p. 637) for full and concise instructions. THE ASH OF PLANTS. 183 Phosphoric acid 8.2 Lime 10.5 Potash 9.1 Magnesia 1.4 Sulphuric acid 2.2 Chlorine 0.9 Nitric acid . . . .29.7 Solid Matters 62 Water 938 1000 For use, dilute 15 or 20 c. c. of the above solution with water to the bulk of a liter and add one or two drops of strong solution of ferric chloride. The solution should be changed at first every week, and, as the plants acquire greater size, their roots should be transferred to a larger vessel filled with solution of the same strength, and the latter changed every 5 or 3 days. It is important that the water which escapes from the , jar by evaporation and by transpiration through the plant should be daily or oftener replaced, by filling it with pure water up to the original level. The solution, whose prep- aration has been described, may be turbid from the sepa- ration of a little calcium sulphate before the last dilution, as well as from the precipitation of phosphate of iron on adding ferric chloride. The former deposit may be dis- solved, though this is not needful; the latter will not dis- solve, and should be occasionally put into suspension by stirring the liquid. When the plant is half grown, fur- ther addition of iron is unnecessary. In this manner, and with this solution, Wolff produced a maize plant five and three quarters feet high, and equal in every respect, as regards size, to plants from similar seed, cultivated in the field. The ears were not, however, fully developed when the experiment was interrupted by the plant becoming unhealthy. With the oat his success was better. Four plants were brought to maturity, having 46 stems and 1535 well-de- veloped seeds. (Vs. St., VIII, pp.190-215.) 184 HOW CEOPS GROW. In similar experiments, Nobbe obtained buckwheat plants, six to seven feet high, bearing three hundred plump and perfect seeds, and barley stools with twenty grain-bearing stalks. (Vs. St., VII, p. 72.) In water-culture the composition of the solution is suf- fering continual alteration, from the fact that the plant makes, to a certain extent, a selection of the matters pre- sented to it, and does not necessarily absorb them in the proportions in which they originally existed. In this way, disturbances arise which impede or become fatal to growth. In the early experiments of Sachs and Knop, in 1860, they frequently observed that their solutions suddenly acquired the odor of hydrogen sulphide, and black iron sulphide formed upon the roots, in consequence of which they were shortly destroyed. This reduction of a sulphate to a sulphide takes place only in an alkaline liquid, and Stohmann was the first to notice that an acid liquid might be made alkaline by the action of living roots. The plant, in fact, has the power to decompose salts, and by appropriating the acids more abundantly than the bases, the latter accumulate in the solution in the free state, or as carbonates with alkaline properties. To prevent the reduction of sulphates, the solution must be kept slightly acid, if needful, by addition of a very little free nitric acid, and, if the roots blacken, they must be washed with a dilute acid, and, after rinsing with water, must be transferred to a fresh solution. On the other hand, Kiihn has shown that when am monium chloride is employed to supply maize with nitro- gen, this salt is decomposed, its ammonia assimilated, and its chlorine, which the plant cannot use, accumulates in the solution in the form of hydrochloric acid to such an extent as to prove fatal to the plant (Henneberg' s Journal, 1864, pp. 116 and 135). Such disturbances are avoided by employing large volumes of solution, and by frequently renewing them, THE ASH OF PLANTS. 185 The concentration of the solution is by no means a matter of indifference. While certain aquatic plants, as sea-weeds, are naturally adapted to strong saline solutions, agricultural land-plants rarely succeed well in water cul- ture, when the liquid contains more than ^^ of solid matters, and will thrive in considerably weaker solutions. Simple well-water is often rich enough in plant-food to nourish vegetation perfectly, provided it be renewed suffi- ciently often. Sachs's earliest experiments were made with well-water. Birner and Lucanus, in 1864 ( Vs. /Stf.,VIII, 154), raised oat-plants in well-water, which in respect to entire weight were more than half as heavy as plants that grew simul- taneously in garden soil, and, as regards seed-production, fully equalled the latter. The well-water employed con- tained but sisW f dissolved matters, or in 100,000 parts: Potash 2.10 Lime 15.10 Magnesia 1.50 Phosphoric acid 0.16 Sulphuric acid 7.50 Nitric acid 6.00 Silica, Chlorine, Oxide of iron traces 100,000 On the other hand, too great dilution is fatal to growth. Nobbe (Vs. St., VIII, 337) found that in a solution con- taining but Ti\ Porinri 1 June 30, (12 clays), Arendt Shortly before full heading. JU } " 29, (10 days), Bretschneider The plants were headed. o/i T>*r*^A I July 10, (10 days), Arendt Immediately after bloom. )a } " 8, ( 9 days), Bretsclmeider Full bloom. 4th pprirwi \ Jul y 21 ( n da y s )> Arendt Beginning to ripen. 30 ) " 28, (20 days), Bretschneider " " fith Vpriodl jul y 31 ' (10 days), Arendt Fully ripe. M I Aug. 6, ( 9 days), Bretschneider Fully ripe. It will be seen that the periods, though differing some- what as to time, correspond almost perfectly in regard to the development of the plants. It must be mentioned that Arendt carefully selected luxuriant plants of equal size, so as to analyze a uniform material (see p. 171), and took no account of the yield of a given surface of soil. Bretschneider, on the other hand, examined the entire produce of a square rod. The former procedure is best adapted to study the composition of the well-nourished individual plant; the latter gives a truer view of the crop. The unlike character of the material as just indicated is but one of the various causes which might render the two series of observations discrepant. Thus, differences in soil, weather and seeding, would necessarily influence the relative as well as the absolute development of the two crops. The results are, notwithstanding, strikingly ac- cordant in many particulars. In all cases the roots were not and could not be included in the investigation, as it is impossible to free them from adhering soil. * Das Wa.c.hsthum der Haferpfln.nze, Leipzif/, 1859. t WachsthumsverhMtnisse der Haferyflanze, Jour./ur Prakt. Chem., 76, 193. COMPOSITION 12? SUCCESSIVE STAGES. 225 The Total Weight of Crop per English acre, at the end of each period, was as follows: TABLE I.Bretschneider. 1st Period, 6,358 Ibs. avoirdupois* 2d " 10,603 " 3d " 16,623 " 4th " 14,981- 5th " 10,622 " The Total Weights of Water and Dry Matter for all but the 2d Period the material of which was acci- dentally lost were: TABLE Il.Bretschneider. Dry Matter, Water, Ibs. av. per acre. Ibs. av. per acre. 1st Period, 1,284 5,074 2d<&3d" 4,383 12,240 4th " 5,427 9,554 5th 6,886 3,736 1. From Table I it is seen: That the weight of the live crop is greatest at or before the time of blossom.* After this period the total weight diminishes as it had previously increased. 2. From Table II it becomes manifest: That the organ- ic tissue (dry matter) continually increases hi quantity up to the maturity of the plant; and 3. The loss after the 3d Period falls exclusively upon the water of vegetation. At the time of blossom the plant has its greatest absolute quantity of water, while its least absolute quantity of this ingredient is found when it is fully ripe. By taking the difference between the weights of any two Periods, we obtain: The Increase or Loss of Dry Matter and Water during each Period. TABLE m.Bretschneider. Dry Matter, Water, Ibs per acre. Ibs per acre. 1st Period, (58 days), 1,284 Gain. 5,074 Gain. 2d&3d" (19 days), 3,09 " 7,166 " 4th " (20 days), 1,044 " 2,686 Loss. 5th " ( S days), 1,456 " 5,818 * *In Areiidt's Experiment, at the time ef "Jia*Uiig out?" 3d -Period 15 226 HOW CROPS GROW. On dividing the above quantities by the number of days of the respective periods, there results: The Average Daily Gain or Loss per Acre during each Period. TABLE IV.Bretschneider. Dry Matter. Water. 1st Period, 22 Ibs. Gain. 87 Ibs. Gain. 2d & 3d " 163 " 377 " " 4th " 52 " " 134 " Loss. 5th " 162 " " 646 " 4. Table III., and especially Table IV, show that the gain of organic matter in Bretschneider's oat-crop went on most rapidly at or before the time of blossom (accord- ing to Arendt at the time of heading out). This was, then, the period of most active growth. Afterward the rate of growth diminished by more than one-half, and at a later period increased again, though not to the maximum. Absolute Quantities of Carbon, Hydrogen, Oxy- gen, Nitrogen (Organic Matter), and Ash in the dry oat-crop at the conclusion of the several periods (Ibs. per acre) : TABLE V.Sretschneider. Carbon. Hydrogen. Oxygen. Nitrogen. Ash.* 1st Period, 593 80 455 46 110 2d & 3d " 2,137 286 1,575 122 263 4th " 2,600 343 2,043 150 291 5th " 3,229 405 2,713 167 372 Amounts of Carbon, Hydrogen, Oxygen, Nitro- gen, and Ash-ingredients assimilated by the oat-crop during the several periods. Water of vegetation is not included (Ibs. per acre) : TABLE VI.Bretschneider. Nitrogen. AtMngredients. 46 110 76 153 28 28 17 81 * In Bretschneider's analyses, " ash " signifies the residue left after carefully burning the plant. In Arendrs investigation the sulphur and chlorine were determined in the unburned plant. 1st Period, Carbon. 593 Hydrogen. 80 Oxygen. 455 2d&3d " 1,544 206 1,575 4th " 453 57 468 5th " 629 62 670 COMPOSITION IN SUCCESSIVE STAGES. 22? Relative Quantities of Carbon, Hydrogen, Oxy- gen, Nitrogen (Organic Matter) and Ash in the dry oat-crop, at the end of the several periods (per cent) : TABLE VII. Bretschneider. Carbon. Hydrogen. Oxygen. Nitrogen. (Organic Matter.) Ash. 1st Period, 46.22 6.23 35.39 3.59 91.43 8.57 2d & 3d " 48.76 6.53 35.96 2.79 94.04 5.96 4th " 47.91 6.33 37.65 2.78 94.67 5.33 5th " 46.89 5.88 39.40 2.43 94.60 5.40 Relative Quantities of Carbon, Hydrogen, Oxy- gen, and Nitrogen, in dry substance, after deducting the somewhat variable amount of ash (per cent) : TABLE VIII. Bretschneider. Carbon. Hydrogen. Oxygen. Nitrogen. 1st Period, 50.55 6.81 38.71 3.93 2d & 3d " 51.85 6.95 38.24 2.86 4th " 50.55 6.96 39.83 2.93 5th " 49.59 6.21 41.64 2.56 5. The Tables V, VI, VII, and VIII, demonstrate that while the absolute quantities of the elements of the dry oat-plant continually increase to the time of ripening, they do not increase in the same proportion. In other words, the plant requires, so to speak, a change of diet as it advances in growth. They further show that nitro- gen and ash are relatively more abundant in the young than in the mature plant ; in other words, the rate of assimilation of Nitrogen and fixed ingredients falls be- hind that of Carbon, Hydrogen, and Oxygen. Still oth- erwise expressed, the plant as it approaches maturity organizes relatively more carbhydrates and less albu- minoids. The relations just indicated appear more plainly when we compare the Quantities of Nitrogen, Hydrogen, and Oxygen, assimilated during each period, calculated upon the amount of Carbon assimilated in the same time and assumed at 100. TABLE IX. Bretschneider. Carbon. Nitrogen. Hydrogen. Oxygen. 1st Period, 100 7.8 13.4 73.6 2d&3d" 100 4.9 13.3 72.5 4th " 100 6.1 12.3 100.8 6th " 100 2.6 10.6 100.6 228 HOW CROPS GROW. From Table IX we see that the ratio of Hydrogen to Carbon regularly diminishes as the plant matures ; that of Nitrogen falls greatly from the infancy of the plant to the period of full bloom, then strikingly increases during the first stages of ripening, but falls off at last to mini- mum. The ratio of Oxygen to Carbon is the same during the 1st, 3d, and 3d Periods, but increases remarkably from the time of full blossom until the plant is ripe. As already stated, the largest absolute assimilation of all ingredients most rapid growth takes place at the time of heading out, or blossom. At this period all the volatile elements are assimilated at a nearly equal rate, and at a rate similar to that at which the fixed matters (ash) are absorbed. In the first period Nitrogen and Ash ; in the 4th Period, Nitrogen and Oxygen ; in the 5th Period, Oxygen and Ash are assimilated in largest proportion. This is made evident by calculating for each period the relative average daily increase of each ingredient, the amount of the ingredients in the ripe plant being assumed at 100, as a point of comparison. The figures resulting from such a calculation are given in TABLE X.retschneider. Carbon. Hydrogen. Oxygen. JfUrogen. Ash. 1st Period, 0.31 0.33 0.28 0.47 0.50 2dand3d " 2.51 2.68 2.17 2.39 2.13 4th " 0.89 0.88 1.07 1.06 0.47 5th " 1.49 1.16 1.89 0.75 1.70 The increased assimilation of the 5th over the 4th Period is, in all probability, only apparent. The results of analysis, as before mentioned, refer only to those parts of the plant that are above ground. The activity of the foliage in gathering food from the atmosphere is doubt- less greatly diminished before the plant ripens, as evi- denced by the leaves turning yellow and losing water of vegetation. The increase of weight in the plant above ground probably proceeds from matters previously stored COMPOSITION IN SUCCESSIVE STAGES. 229 in the roots, which now are transferred to the fruit and foliage, and maintain the growth of these parts after their power of assimilating inorganic food (C0 2 , H 2 0, NH 3 , 1S T 2 5 ) is lost. The following statement exhibits the absolute average daily increase of Carbon, Hydrogen, Oxygen, Nitrogen, and Ash, during the several periods (Ibs. per acre) : TABLE XI.Bretschneider. . Carbon. Hydrogen. Oxygen. Nitrogen. Ath. 1st Period, 10.0 1.4 7.8 0.8 1.9 2dand3d " 81.0 10.8 83.0 4.0 8.0 4th " 22.6 2.9 23.4 1.4 1.4 6th " 70.0 6.9 74.4 1.9 9.0 Turning now to Arendt's results, which are carried more into detail than those of Bretschneider, we will notice: A. The Relative* (percentage] Composition of the Entire Plant and of its Parts* during the several periods of vegetation. 1. Fiber \ is found in greatest proportion 40 per cent in the lower joints of the stem, and from the time when the grain "heads out," to the period of bloom. Relatively considered, there occur great variations in tha same part of the plant at different stages of growth. Thus, in the ear, which contains the least fiber, the quantity of this substance regularly diminishes, not absolutely, but only relatively, as the plant becomes older, sinking from 27 per cent at heading to 12 per cent at maturity. In the leaves, which, as regards fiber, stand intermediate between the stem and ear, this * Aremlt selected large and well-developed plants, divided them into six parts, and analyzed each part separately. His divisions of the plants were: 1, the three lowest joints of the stem; 2, the two middle joints; 3, the upper joint; 4, the three lowest leaves; 5, the two upper leaves; 6, the ear. The stems were cut just above the nodes, the leaves included the sheaths, the ears were stripped from the stem. Arendt rejected all plants which were not perfect when gathered. When nearly ripe, the cereals, as is well known, often lose one or more of their lower leaves. For the numerous analyses on which these conclu- sions are based we must refer to the original. t L e., Crude cellulose; see p. 45. 230 HOW CEOPS GROW. substance ranges from 22 to 38 per cent. Previous to blossom, the upper leaves, afterwards the lower leaves, are the richest in fiber. In the lower leaves the maxi- mum (33 per cent) is found in the fourth ; in the upper leaves (38 per cent), in the second period. The apparent diminution in amount of fiber is due in all cases to increased production of other ingredients. 2. Fat and Wax are least abundant in the stem. Their proportion increases, in general, in the upper parts of the stem as well as during the latter stages of its growth. The range is from 0.2 to 3 per cent. In the ear the propor- tion increases from 2 to 3. 7 per cent. In the leaves the quantity is much larger and is mostly wax with little fat. The smallest proportion is 4.8 per cent, which is found in the upper leaves when the plant is ripe. The largest proportion, 10 per cent, exists in the lower leaves, at the time of blossom. The relative quantities found in the leaves undergo considerable variation from one stage of growth to another. 3. Non-nitrogenous matters, other than fiber, viz., starch, sugars, gums, etc.,* undergo great and irregular variation. In the stem the largest percentage (57 per cent) is found in the young lower joints; the smallest (43 per cent) in ripe upper straw. Only in the ear occurs a regular in- crease, viz., from 54 to 63 per cent. 4. The albuminoids, f in Arendt's investigation, exhibit a somewhat different relation to the vegetable substance from what was observed by Bretschneider, as seen from the subjoined comparison of the percentages found at the different periods : PERIODS. i. ii. in. rv. v. Arendt 20.93 11.65 10.86 13.67 14.30 Bretschneider 22.73 17.67 17.61 15.39 * What remains after deducting fat and wax, albuminoids, fiber and ash, from the dry substance, is here included. t Calculated by multiplying the percentage of nitrogen by 6.33. These differences may be variously accounted for. They COMPOSITION IN SUCCESSIVE STAGES. 231 are due, in part, to the fact that Arendt analyzed only large and perfect plants. Bretschneider, on the other hand, examined all the plants of a given plot, large and small, perfect and injured. The differences illustrate what has been already insisted on, viz., that the develop- ment of the plant is greatly modified by the circum- stances of its growth, not only in reference to its exter- nal figure, but also as regards its chemical composition. The relative distribution of nitrogen in the parts of the plant at the end of the several periods is exhibited by the following table, simple inspection of which shows the fluctuations (relative) in the content of this element. The percentages are arranged for each period separately, pro- ceeding from the highest to the lowest : PERIODS. I. II. III. IV. V. Upper leaves. Lower leaves. Upper leaves. Ears. Ears. 3.74 2.3i) 2.27 2.85 3.04 Lower leaves. Upper leaves. Lower leaves. Upper leaves. Upper leaves. 3.38 2.19 2.18 1.91 1.74 Lower leaves. Ears. Ears. Lower leaves. Upper stem. 2.15 2.06 1.85 1.62 1.56 Middle stem. Upper stem. Upper stem. Lower leaves. 1.52 1.34 1.60 1.43 Upper stem. Middle stem. Middle stem. Middle stem. 0.87 0.98 1.20 1.17 Lower stem. Lower stem. Lower stem. Lower stem. 0.80 0.88 0.83 0.79 5. Ash. The agreement of the percentages of ash in the entire plant, in corresponding periods of the growth of the oat, in the independent examinations of Bret- schneider and Arendt, is remarkably close, as appears from the figures below : Bretschneider 8.57 Arendt... ...8.03 II. 5.24 PERIODS. III. 5.96 5.44 IV. 5.33 5.20 V. 5.40 5.17 As regards the several parts of the plant, it was found by Arendt that, of the stem, the upper portion was richest in ash throughout the whole period of growth. Of the leaves, on the contrary, the lower contained most fixed matters. In the ear there occurred a continual decrease 232 HOW CROPS GROW. from its first appearance to its maturity, while in the stem and leaves there was, in general, a progressive increase towards the time of ripening. The greatest percentage (10.5 per cent) was found in the ripe leaves; the smallest (0.78 per cent) in the ripe lower straw. Far more interesting and instructive than the relative proportions are B. The Absolute Quantities of the Ingredients found in the Plant at the conclusion of the sev- eral periods of growth. These absolute quantities, as found by Arendt, in a given number of carefully- selected and vigorous plants, do not accord with those obtained by Bretsclmeider from a given area of ground, nor could it be expected that they should, because it is next to impossible to cause the same amount of vegeta- tion to develop on a number of distinct plots. Though the results of Bretschneider more nearly rep- resent the crop as obtained in farming, those of Arendt give a truer idea of the plant when situated in the best possible conditions, and attaining a uniformly high development. We shall not attempt to compare the two sets of observations, since, strictly speaking, in most points they do not admit of comparison. From a knowledge of the absolute quantities of the substances contained in the plant at the ends of the several periods, we may at once estimate the rate of growth, i. e., the rapidity with which the constituents of the plant are either taken up or organized. The accompanying table, which gives in alternate col- umns the total weights of 1,000 plants at the end of the several periods, and (by subtracting the first from the second, the second from the third, etc.) the gain from matters absorbed or produced during each period, will serve to justify the deductions that follow, which are taken from the treatise of Arendt, and which apply, of course, only to the plants examined by this investigator. COMPOSITION IN SUCCESSIVE STAGES. 233 3 be sIS a - b jooiNiq > OO CO CO joqc^o 60 ? ! 1 III SS8 0 r^ be* 3 "S S fe p 234 HOW CBOPS GROW. 1. The plant increases in total weight (dry matter) through all its growth, but to unequal degrees in differ- ent periods. The greatest growth occurs at the time of heading out ; the slowest, within ten days of maturity. We may add that the increase of the oat after blossom takes place mostly in the seed, the other organs gaining but little. The lower leaves almost cease to grow after the 3d Period. 2. Fiber is produced most largely at the time of head- ing out (3d Period). When the plant has finished blos- soming (end of 3d Period), the formation of fiber entirely ceases. Afterward there appears to occur a slight diminution of this substance, more probably due to unavoidable loss of lower leaves than to a resorption or metamorphosis in the plant. 3. Fat is formed most largely at the time of blossom. It ceases to be produced some weeks before ripening. 4. Albuminoids are very irregular in their formation. The greatest amount is organized during the 4th Period (after blossoming). The gain in albuminoids within this period is two-fifths of the total amount found in the ripe plant, and also is nearly two-fifths of the entire gain of organic substance in tb,e same period. The absolute amount organized in the 1st Period is not much less than in the 4th, but in the 3d, 3d and 5th Periods the quantities are considerably smaller. Bretschneider gives the data for comparing the pro- duction of albuminoids in the oat crop examined by him with Arendt's results. Taking the quantity found at the conclusion of the 1st Period as 100, the amounts gained during the subsequent periods are related as follows: PERIODS. I. II. III. (II. & III.) IV. (II., III. & IV.) V. Arendt 100 67 46 (113) 120 (233) 36 Bretschneider .100 ? ? (165) 62 (22T) 35 We perceive striking differences in the comparison. In COMPOSITION IN SUCCESSIVE STAGES. 235 Bretschneider's crop the increase of albuminoids goes on most rapidly in the 3d and 3d Periods, and sinks rapidly during the time when in Arendt's plants it attained the maximum. Curiously enough, the gain in the 3d, 3d and 4th Periods, taken together, is in both cases as good as identical (233 and 227), and the gain during the last period is also equal. This coincidence is doubtless, how- ever, merely accidental. Comparisons with other crops of oats examined, though much less completely, by Stockhardt (Chemischer Ackersmann, 1855) and Wolff (Die Erschopfung des Bodens durch die Cultur, 1856) demonstrate that the rate of assimilation is not related to any special times or periods of development, but depends upon the stores of food accessible to the plant and the favor of the weather, or other external conditions. The following figures, which exhibit for each period of both crops a comparison of the gain in albuminoids with the increase of the other organic matters, further strikingly demonstrate that, in the act of organization, the nitrogenous principles have no close quantitative relations to the non-nitrogenous bodies (carbhydrates and fats). The quantities of albuminoids gained during each period being represented by 10, the amounts of carbhy- drates, etc., are seen from the subjoined ratios : PERIODS. Ratio in I. II & III. IV. V. Ripe Plant. Arendt 10:34 10:114 10:28 10 : 25 10:66 Bretschneider..lO : 30 10 : 50 10 : 46 10 : 120 10 : 51 5. The Ash-ingredients of the oat are absorbed through- out its entire growth, but in regularly diminishing quan- tity. The gain during the 1st Period being taken at 10, that in the 2d Period is 9, in the 3d, 8, in the 4th, 5, in the 5th, 2 nearly. The ratios of gain in ash -ingredients to that in entire dry substance, are as follows, ash-ingredients being assumed as 1, in the successive periods : 236 HOW CROPS GEOW. 1 : 12}, 1 : 27, 1 : 16, 1 : 23, 1 : 19. Accordingly, the absorption of ash-ingredients is not proportional to the growth of the plant, but is to some degree accidental, and independent of the wants of vegetation. Recapitulation. Assuming the quantity of each proxi- mate element in the ripe plant as 100, it contained at the end of the several periods the following amounts (per cent) : Fiber. Fat. Carbhydrates.* Albuminoids. Ah. 1. Period, 18 20 15 27 29 II. " 81 50 47 45 55 III. " 100 85 70 57 79 IV. " 100 100 92 90 95 V. " 100 100 100 100 100 Taking the total gain as 100, the gain during each period was accordingly as follows (per cent) : Fiber. Fat. Carbhydrates.* Albuminoids. Ash. I. Period, 18 20 15 27 29 II. " 63 30 32 18 26 HI. " 19 35 23 12 24 IV. " 15 22 33 16 V. " 00 8 10 5 100 100 100 100 "lOO 6. As regards the individual ingredients of the ask, the plant contained at the end of each period the follow- ing amounts, the total quantity in the ripe plant being taken at 100. Corresponding results from Bretschneider enclosed in ( ) are given for comparison: Sulphuric Phosphoric Silica. Oxide Oxide Lime. Magnesia. Potash. Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. L Period, 18 ( 22) 20 (42) 23 ( 23) 30 (31) 24 ( 31) 39 ( 42) II. 41| (5 62 J (44) 42} 58 (83) 42. 70. III. " 70 J 52' 73* 79) ' 58 J 91 ' IV. 93 (72) 90 ( 39) 91 (74) 99 ( 74) 84 ( 77) 100 (100) V. " 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) 100 (95*) The gain (or loss, indicated by the minus sign ) in these ash-ingredients during each period is given below: * Exclusive of Fiber. COMPOSITION IN SUCCESSIVE STAGES. 237 Silica. Sulphuric Oxide. Phosphoric Oxide. Lime. Magnesia. Potash. Per cent . Per cent. Per cent . Per cent. Per cent. Per cent. I. II. III. Period, 18 ( 22) " 23 \(35) 29) 20 32 (42) j( 2) 23 19 31 (23) |(40) 30 (31 ) 24 18 16 (31) [(42) 39 31) 21) (42) |(47) IV. V. " 23 ( 15) 7 ( 28) 38 10 (-5*) (56) 18 9 (10) (27) 20 1 (-*) (17) 26 16 (4) (23) 9 (11 ) (-5*) 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) These two independent investigations could hardly give all the discordant results observed on comparing the above figures, as the simple consequence of the unlike mode of conducting them. We observe, for example, that in the last period Arendt's plants gathered less silica than in any other only 7 per cent of the whole. On the other hand, Bretschneider's crop gained more silica in this than in any other single period, viz. : 28 per cent. A similar statement is true of phosphoric oxide, f It is obvious that Bretschneider's crop was tak- ing up fixed matters much more vigorously in its last stages of growth than were Arendt's plants. As to potash, we observe that its accumulation ceased in the 4th Period in both cases. C. Translocation of Substances in the Plant. The transfer of certain matters from one part of the plant to another during its growth is revealed by the analyses of Arendt, and since such changes are of inter- est from a physiological point of view, we may recount them here briefly. It has been mentioned already that the growth of the stem, leaves, and ear of the oat plant in its later stages probably takes place to a great degree at the expense of the roots. It is also probable that a transfer of carbhy- *In these instances Bretschneider's later crops appear to contain less sulphuric oxide, lime and potash, than the earlier. Thisresult maybe due to the washing of the crop by rains, but is probably caused by unequal development of the several plots. t Phosphoric oxide is the "phosphoric acid," P 2 O S , of older and to a great degree of current usage. See p. 163. 238 HOW CROPS GROW. drates, and certain that one of albuminoids, goes on from the leaves through the stem into the ear. Silica, appears not to be subject to any change of posi- tion after it has once been fixed by the plant. Chlorine likewise reveals no noticeable mobility. On the other hand, phosphoric oxide passes rapidly from the leaves and stem towards or into the fruit in the ear- lier as well as in the later stages of growth, as shown by the following figures : One thousand plants contained in the various periods quantities (grams) of phosphoric oxide as follows : 1st 2d 3d 4th 6th Period. Period. Period. Period. Period. 3 lower joints of stem, 0.47 0.20 0.21 0.20 0.19 2 middle " " 0.39 1.14 0.46 0.18 Upper joint " 0.66 1.73 0.31 0.39 3 lower leaves " 1.05 0.70 0.69 0.51 0.35 2 upper leaves " 1.75 1.67 1.18 0.74 0.59 Ear, 2.36 5.36 10.67 12.52 Observe that these absolute quantities diminish in the stem and leaves after the 1st or 3d Period in all cases, and increase very rapidly in the ear. Arendt found that sulphuric oxide existed to a much greater degree in the leaves than in the stem through- out the entire growth of the oat plant, and that, after blossoming, the lower stem no longer contained sulphur in the form of sulphates at all, though its total in the plant considerably increased. It is almost certain, then, that sulphuric oxide originates, either partially or wholly, by oxidation of sulphur or some sulphurized compound, in the upper organs of the oat. Magnesium is translated from the lower stem into the upper organs, and in the fruit, especially, it constantly increases in quantity. There is no evidence that Calcium moves upward in the plant. On the contrary, Arendt's analyses go to show that in the ear, during the last period of growth, it COMPOSITION IK SUCCESSIVE STAGES. 239 diminishes in quantity, being, perhaps, replaced by magnesium. As to potassium, no transfer is fairly indicated, except from the ears. These contained at blossoming (Period III) a maximum of potassium, During their subsequent growth the amount of this element diminished, being probably displaced by magnesium. The data furnished by Arendt's analyses, while they indicate a transfer of matters in the cases just named, and in most of them with great certainty, do not and cannot from their nature disprove the fact of other simi- lar changes, and cannot fix the real limits of the move- ments which they point out. DIVISION II. THE STRUCTURE OF THE PLANT AND OFFICES OF ITS ORGANS. CHAPTER I. GENERALITIES. We have given a brief description of those elements and compounds which constitute the plant in a chemical sense. They are the materials the stones and timbers, so to speak out of which the vegetable edifice is built. It is important, in the next place,, to learn how these building materials are put together, what positions they occupy, what purposes they serve, and on what plan the edifice is constructed. It is impossible for the builder to do his work until he has mastered the plans and specifications of the archi- tect. So it is hardly possible for the farmer with cer- tainty to contribute in any great, especially in any new, degree, to the upbuilding of the plant, unless he is acquainted with the mode of its structure and the ele- ments that form it. It is the happy province of science to add to the vague and general information which the observation and experience of generations have taught, a more definite and particular knowledge, a knowledge acquired by study purposely and carefully directed to special ends. An acquaintance with the parts and structure of the plant is indispensable for understanding the mode by which it derives its food from external sources, while the 16 241 242 HOW CEOPS GROW. ingenious methods of propagation practiced in fruit- and flower-culture are only intelligible by the help of this knowledge. ORGANISM OF THE PLANT. We have at the outset spoken of organic matter, of organs and organization. It is in the world of life that these terms have their fit- test application. The vegetable and animal consist of numerous parts, differing greatly from each other, but each essential to the whole. The root, stem, leaf, flower and seed are each instruments or organs whose co-oper- ation is needful to the perfection of the plant. The plant (or animal) being thus an assemblage of organs, is called an Organism; it is an Organized or Organic Structure. The atmosphere, the waters, the rocks and soils of the earth, do not possess distinct co-operating parts ; they are Inorganic matter. In inorganic nature, chemical affinity rules over the transformations of matter. A plant or animal that is dead, under ordinary circumstances, soon loses its form and characters ; it is gradually consumed, and, at the ex- pense of atmospheric oxygen, is virtually burned up to air and ashes. In the organic world a something, which we call Vitality, resists and overcomes or modifies the affinities of oxygen, and insures the existence of a continuous and perpetual succession of living forms. An Organism or Organized Structure is characterized and distinguished from inorganic matter by two par- ticulars : 1. It builds up and increases its own mass by appro- priating external matter. It absorbs and assimilates food. It grows by the enlargement of all its parts. 2. It reproduces itself. It develops from a germ, and in turn gives origin to new germs. ULTIMATE AND COMPLEX ORGANS. In our account of the Structure of the Plant we shall first consider the ELEMENTS OF ORGANIZED STRUCTURE. 243 elements of that structure the Cells which cannot be divided or wounded without extinguishing their life, and by whose expansion or multiplication all growth takes place. Then will follow an account of the com- plex parts of the plant its Organs which are built up by the juxtaposition of numerous cells. Of these we have one class, viz., the Eoots, Stems and Leaves, whose office is to sustain and nourish the Individual Plant. These may be distinguished as the Vegetative Organs. The other class, comprising the Flower and Fruit, are not essential to the existence of the individual, but their function is to maintain the Race. They are the Repro- ductive Organs. CHAPTER II. PRIMARY ELEMENTS OF ORGANIZED STRUCTURE. THE VEGETABLE CELL. One of the most interesting discoveries that the micro- scope has revealed, is that all organized matter originates in the form of minute vesicles or cells. If we examine by the microscope a seed or an egg, we find nothing but a cell-structure a mass of rounded or many-sided bags lying closely together, and more or less filled with solid or liquid matters. From these cells, then, comes the frame or structure of the plant or of the animal. In the process of maturing, the original vesicles are vastly mul- tiplied and often greatly modified in shape and appear- ance, to suit various purposes ; but still it is always easy, especially in the plant, to find cells of the same essential characters as those occurring in the seed. 244 HOW CROPS GROW. Cellular Plants. In the simpler forms or lower orders * of vegetation, we find plants which, throughout all the stages of their life, consist entirely of similar cells, and indeed many are known which are but a single cell. The phenomenon of red snow, frequently observed in Alpine and Arctic regions, is due to a microscopic one-celled plant which propagates with great rapidity, and gives its color to the surface of the snow. In the chemist's laboratory it is often observed that in the clear- est solutions of salts, like the sulphates of sodium and magnesium, a flocculent mold, sometimes red, some- times green, most often white, is formed, which, under the microscope, is seen to be a vegetation consisting of single cells. Brewers' yeast, Fig. 27, is nothing more than a mass of one or few-celled plants. In sea-weeds, mushrooms, the molds that grow on damp walls, or upon bread, cheese, etc., and in the blights which infest many of the farmer's crops, we have examples of plants formed exclusively of cells. All the plants of higher orders we find likewise to consist chiefly of globular or angular cells. All the growing parts especially, as the tips of the roots, the leaves, flowers and fruit, are, for the most part, aggrega- tions of such minute vesicles. If we examine the pulp of fruits, as that of a ripe *Viz. : the Cryptogams, including Molds and Mushrooms (Fungi\ Mosses, Ferns, Sea- Weeds (Algae) and Bacteria (Schizomycetes). ELEMENTS OF OBGANIZED STBUCTUBE. 245 apple or tomato, we are able, by means of a low magni- fier, to distinguish the cells of which it almost entirely consists. Fig. 28 represents a bit of the flesh of a ripe pippin, magnified 50 diameters. The cells mostly cohere together, but readily admit of separation. Structure of the Cell. By the aid of the micro- scope it is possible to learn something with regard to the internal structure of the cell itself. Fig. 29 exhibits the appearance of a cell from the flesh of the Artichoke (Helianthus), magnified 230 diameters ; externally the membrane, or wall of the cell, is seen in section. This membrane is filled and distended by a transparent liquid, the sap or free water of vegetation. Within the cell is ob- served a round body, b, which is called the nucleus, and upon this is seen a smaller nucleolus, c. Lining the inte- rior of the cell-membrane and connected with the nucleus, is a yellowish, turbid, semi-fluid substance of mucilaginous consistence, a, which is designated the protoplasm, or formative layer. This, when more highly magnified, is found to contain a vast number of excessively minute granules. By the aid of chemistry the microscopist is able to dis- sect these cells, which are hardly perceptible to the unassisted eye, and ascertain to a good degree how they are constituted. On moistening them with solution of iodine, and afterward with sulphuric acid, the outer membrane the cell-wall shortly becomes of a fine blue color. It is accordingly cellulose, the only vegetable substance yet known which is made blue by iodine after, and only after, the action of sulphuric acid. At the same time we observe that the interior, half -liquid, pro- toplasm, coagulates and shrinks together, separates, therefore, from the cell-wall, and, including with it the 246 HOW CROPS GEOW. nucleus and the smaller granules, lies in the center of the cell like a collapsed bladder. It also assumes a deep yellow or brown color. If we moisten one of these cells with nitric acid, the cell- wall is not affected, but the liquid penetrates it, coagulates the inner membrane, and colors it yellow. In the same way this membrane is tinged violet-blue by hydrochloric acid. These reactions leave no room to doubt that the slimy inner lining of the cell or protoplasm contains abundance of albuminoids. The protoplasm is not miscible with water and main- tains itself distinct from the cell-sap. In young cells it is constantly in motion, the granules suspended in it cir- culating as in a liquid current. If we examine the cells of any other plant we find almost invariably the same structure as above described, provided the cells are young, i. e., belong to growing parts. In some cases isolated cells consist only of proto- plasm and nucleus, being destitute of cell-walls during a portion or the whole of their existence. In studying many of the maturer parts of plants, viz., such as have ceased to enlarge, as the full-sized leaf, the perfectly formed wood, etc., we find the cells do not cor- respond to the description just given. In external shape, thickness, and appearance of the cell-wall, and especially in the character of the contents, there is indefinite va- riety. But this is the result of change in the original cells, which, so far as our observations extend, are always, at first, formed closely on the pattern that has been de- scribed. Vegetable Tissue. It does not, however, usually happen that the individual cells of the higher orders of plants admit of being obtained separately. They are attached together more or less firmly by their outer sur- faces, so as to form a coherent mass of cells a tissue, as it is termed. In the accompanying cut, Fig. 30, is shown a highly-magnified view of a portion of a very thin slice ELEMENTS OF ORGANIZED STRUCTURE. 247 across a young cabbage-stalk. It exhibits the outline of the irregular empty cells, the walls of which are, for the most part, externally united and appear as one, a. At the points indicated by 5, air-filled cavities between the cells are seen, called intercellular spaces. A slice across the potato-tuber (see Fig, 52, p. 300) has a similar ap- pearance, except that the cells are filled with starch, and it would be scarcely pos- sible to dissect them apart; but when a potato is boiled the starch - grains swell, and the cells, in conse- 'quence, separate from each other, a practical result of which is to make the po- tato mealy. A thin slice of vegetable ivory (the seed ofPhytelephas macro- Fig, so. carpa) under the micro- scope, dry or moistened with water, presents no evident trace of cell-structure ; however, upon soaking in sul- phuric acid, the mass softens and swells, and the indi- vidual cells are revealed, their surfaces separating in six-sided outlines. Form of Cells. In the soft, succulent parts of plants, the cells lie loosely together, often with consider- able intercellular spaces, and have mostly a rounded out- line. In denser tissues, the cells are crowded together in the least possible space, and hence often appear six- sided when seen in cross-section, or twelve-sided if viewed entire. A piece of honey-comb is an excellent illustra- tion of the appearance of many forms of vegetable cell- tissue. The pulp of an orange is the most evident example of cell-tissue. The individual cells of the ripe orange may be easily separated from each other. Being mature and 248 HOW CROPS GROW. incapable of further growth, they possess neither proto- plasm nor nucleus, but are filled with a sap or juice con- taining citric acid, sugar and albuminoids. In the pith of the rush, star-shaped cells are found. In common mold the cells are long and | thread-like. In the so-called frog-spittle (algce) they are cylindrical and attached end to end. In the bark of many trees, in the stems and leaves of grasses, they are square or rectangular. Cotton-fiber, flax, and hemp consist of long and slender cells, Fig. 31. Wood is mostly made up of elongated cells, tapered at the ends and adhering together by their sides. See also Fig. 49, c, h, p. 292. Each cotton-fiber is a single cell which forms an external appendage to the seed-vessel of the cotton ^ plant. Wlieii it has lost its sap and become air-dry, its sides collapse and it resembles a twisted strap. \A, in Fig. 31, exhibits a portion of a cotton-fiber highly magnified. The flax-liber, from the inner bark of the flax-stem, b, Fig. 31, is a tube of thicker walls and smaller bore than the cotton-fiber, and. hence is more durable than cotton. It is very flexi- ble, and even when crushed or bent short retains much of its original tenacity. Hemp-fiber closely resembles flax-fiber in appearance. Thickening of the Cell-Membrane. The growth of the cell, which, When young, has a very delicate outer membrane, often results in the thick- ening of its walls by the interior dep- osition of cellulose and woody mat- ters. This thickening may take place vJ-| regularly and uniformly, or interrupt- edly. The flax-fiber, b, Fig. 31, is an ex- ample of nearly uniform thickening. The irregular deposition of cellulose is shown in Fig. 32, which exhibits a sec- tion from the seeds (cotyledons) of the common nasturtium ( Tropveolum majus). The original membrane is coated interiorly with several dis- tinct and successively-formed linings, which are not continuous, but are irregularly developed. Seen in section, the thickening has a waved outline, and, at points, the original coil-membrane is bare. Were these cells viewed entire, we should see at these points, on the exterior of the cell, dots or circles appearing like orifices, but being simply the Fig. 31. Fig. 32. ELEMENTS OF ORGANIZED STBUCTDBE. 249 ttnthickened portions of the cell-wall. The cells in fig. 32 exhibit each a central nucleus surrounded by grains of aleurone. Cell Contents. Besides the protoplasm and nucleus, the cell usually contains a variety of bodies, which have been, indeed, noticed already as ingredients of the plant, but which may be here recapitulated. Many cells arc altogether empty, and consist of nothing but the cell- wall. Such are found in the bark or epidermis of most plants, and often in the pith, and although they remain connected with the actually living parts, they have no longer any proper life in themselves. All living or active cells are distended with liquid. This consists of water, which holds in solution gum, dex- trin, inulin, the sugars, albuminoids, organic acids, and other vegetable principles, together with various salts, both of organic and mineral acids, and constitutes the sap of the plant. In oil-plants, droplets of oil occupy certain cells, Fig. 17, p. 83; while in numerous kinds of vegetation colored and milky juices are found in certain spaces or channels between the cells. The water of the cell comes from the soil, or in some cases from the air. The matters, which are dissolved in the sap of the plant, together with the semi-solid proto- plasm, undergo transformations resulting in the produc- tion of various solid substances. By observing the sev- eral parts of a plant at the successive stages of its devel- opment, under the microscope, we are able to trace within the cells the formation and growth of starch- grains, of granular or crystalline bodies consisting chiefly of albuminoids, and of the various matters which give color to leaves and flowers. The circumstances under which a cell develops deter- mine the character of its contents. The outer cells of the potato-tuber are incrusted with corky matter, the inner ones are for the most part filled with starch. In oats, wheat, and other cereals, we find, just within 250 HOW CHOPS GEOW. the skin or epidermis of the grain, a few layers of cells that contain scarcely anything but albuminoids, with a little fat ; while the interior cells are chiefly filled with starch. Fig. 18, p. 110. Transformations in Cell Contents. The same cell may exhibit a great variety of aspect and contents at different periods of growth. This is especially to be observed in the seed while developing on the mother plant. Hartig has traced these changes in numerous plants under the microscope. According to this ob- server, the cell-contents of the seed (cotyledons) of the common nasturtium (TropcBolum majus) run through the following metamorphoses. Up to a certain stage in its development the interior of the cells are nearly devoid of recognizable solid matters, other than the nucleus and the adhering protoplasm. Shortly, as the growth of the seed advances, green grains of chlorophyll make their appearance upon the nucleus, completely covering it from view. At a later stage, these grains, which have enlarged and multiplied, are seen to have mostly become detached from the nucleus, and lie near to and in contact with the cell- wall. Again, in a short time the grains lose their green color and assume, both as regards appear- ance and deportment with iodine, all the characters of starch. Subsequently, as the seed hardens and becomes firmer in its tissues, the microscope shows that the starch-grains, which were situated near the cell-wall, have vanished, while the cell-wall itself has thickened inwardly the starch having been converted into cellu- lose or bodies of similar properties. Again, later, the nu- cleus, about which, in the meantime, more starch-grains have been formed, undergoes a change and disappears ; then the starch-grains, some of which have enlarged while others have vanished, are found to be imbedded in a pasty matter, which has the reactions of an albuminoid. From this time on, the starch-grains are gradually converted ELEMENTS OF ORGANIZED STKUCTtJBE. 251 from their surfaces inwardly into smaller grains of aleu- rone, which, finally, when the seed is mature, completely occupy the cells. In the sprouting of the seed similar changes occur, but in reversed order. The nucleus reappears, the aleurone dissolves, and even the cellulose* stratified upon the inte- rior of the cell (Fig. 32) wastes away and is converted into soluble food (sugar ?) for the seedling plant. Fig. 38. The Dimensions of Vegetable Cells are very vari- ous. A creeping marine plant is known the Caulerpa, prolifera (Fig. 33) which consists of a single cell, though it is often a foot in length, and is branched with what have the appearance of leaves and roots. The pulp of * Or more probably metarabin, paragalaetin, xylin, or the like insol- uble substances, which as yet have been but imperfectly distinguished from cellulose iu the thickened cell-walls. 252 HOW CROPS GROW. the orange consists of cells which are one-quarter of an inch or more in diameter. The fiber of cotton is a single cell, commonly from one to two inches long. In most cases, however, the cells of plants are so small as to re- quire a powerful microscope to distinguish them, are, in fact, no more than j^^ to 5 ....from 309 to 473 Vetch, .< 33 to 66 Lupin, 486 to 639 Differences often no less marked are found among the seeds in any considerable sample, gathered from a large number of plants and representing a crop. Nobbe, with great painstaking, has ascertained the average, maxi- mum and minimum weights, of 180 kinds of seeds, such as are found in commerce or are used in Agriculture, Horticulture, and Forestry. The following table gives some of his results : EEPEODUCTIVE ORGANS OF PLANTS. 341 Absolute Weight of Commercial Seeds. Number of Weight of one Seed in Samples Milligrams. Examined. Average. Maximum. Minimum! Oats, 84 28.8 54.1 14.7 Barley, 66 41.0 48.9 27.7 Rye,... 119 23.3 47.9 13.0 Wheat, 96 37.6 45.8 15.2 Maize, 22 282.7 382.9 114.5 Beet, 39 22.0 42.4 14.2 Turnip, Brassica rapifera,.. 23 2.2 3.0 1.4 Carrot, 35 1.2 1.7 0.8 Pea, 43 185.8 564.6 46.1 Kidney Bean, Phaseolus 5 585.6 926.3 367.3 Horse Bean, Vicia 7 676.0 2061.0 256.4 Potato, 3 0.6 0.7 0.5 Tomato, 5 2.5 2.7 2.4 Spinage, 4 6.9 9.0 2.4 Radish, 5 7.1 9.7 5.7 Lettuce, 18 1.1 1.7 0.8 Parsnip, 3 3.1 3.8 2.3 Squash, 5 173.0 322.0 106.7 Musk Melon, 3 32.9 35.5 28.2 Cucumber, 6 25.4 27.0 21.0 Timothy, Phleum pratense,, 73 0.41 0.59 0.34 Blue Grass, Poa pratensis, . . 28 0.15 0.21 0.10 Red Clover, 355 1.60 2.08 1.14 White Clover, 53 0.61 0.69 0.47 Ten-weeks-stocks, Mattlii- ola annua, 4 1.50 1.60 1.39 Oak, Quercus pedunculata,. 15 2013.4 4213.5 761.6 It ia noteworthy, that in case of Oats, Eye, Wheat, Maize, Beet, Spinage, and Squash, the heaviest seeds weigh thrice as much as the lightest. With Turnip, Carrot, Kidney-bean, Lettuce, and Blue grass, some seeds are double the weight of others. The horse-bean gives some seeds eight times as heavy as others. The differences brought out in the Table in many cases are due to the representation of different varieties ; the larger seeds, to some extent, belonging to larger plants ; but the great range of weight, noted with regard to the seed of the Oak, applies to 15 crops of sound acorns from one and the same tree, gathered in 15 successive years. In many varieties of Indian Corn, the kernels at the base of the ear are larger, and those at the tip are smaller, than those of the middle portion. Other varie- ties are characterized by great uniformity in the size of the kernels, having been " bred up " to this quality by careful seed-selection. It is well-known that the middle part of the ears of 342 HOW CROPS GROW. wheat and barley produce the heaviest kernels. Nobbe numbered and weighed the spikelets from an ear of six- rowed barley and from one of winter wheat. Either ear contained 27 spikelets, each with three kernels. The kernels of the smallest barley-spikelet, No. 2, from the base of the ear, weighed 1.5 milligrams; those of the largest, No. 10, weighed 103.5 mg. No. 27 weighed 32.5 mg. The corresponding numbers in wheat weighed 0.5, 34.5 and 10.8 mg. In case of barley, each of the first five spikelets, count- ing from the base, weighed less than 70 milligrams. The 6th to the 22d, inclusive, weighed 75 mg. or more. The 7th to the 16th weighed 90 mg. or more. The 17th to the 21st, 80 mg. or more. Thence, to the tip, the weight rapidly declined to about 30 milligrams. The wheat kernels exhibited quite similar variation of weight. Dividing the 27 spikelets into three groups of nine each, we have the following comparison of weights of seeds, to which is added the total lengths of the rootlets that were formed after germination had gone on for five BARLEY. WHEAT. Weight. Length of Root. Weight. Length of Root. Spikelets, 1 to 9 426 mg. 670mm. 153 mg. 223mm. 10 to 18 828 8281 " 282 1094 18 to 27 512 1364 " 191 " 454 The seeds of the middle portion of the ears of barley and wheat are thus seen to be very considerably heavier than those of either the base or tip, and also show greater ger- minative vigor, as measured by the comparative growth of the roots in a given short time. The greater weight and germinative energy of the seeds from the middle of the ears, stand in relation to the fact that these seeds are the oldest the flowers from which they develop being the first to open and fructify. In case of a head of summer rye, Nobbe found that the REPRODUCTIVE ORGANS OF PLANTS. 343 33 spikelets, each with two buds, required a week for blossoming ; the first of the 66 flowers to open were mostly those of the thirties and forties, and the last those of the tens, fifties, and sixties, counting from the base upward. These middle seeds had accordingly an earlier start, and better chance for full development, than those at the base and tip of the ear. Oat kernels usually grow in pairs, the upper one of each pair being in general lighter and smaller than the lower one. Nobbe counted out 200 upper kernels, 200 lower kernels, and 200 average kernels, without selection. These were weighed, and, after soaking In water for 24 hours, were placed in a sprouting apparatus at a tem- perature of about 70 F. The results were as follows : 100 seeds Number of seeds that sprouted. weighed. On the Total in Grams. 3d, 4th, 5th, 6th, 7th, 8th, 9th, 10th days. 10 days. Upper Kernels, 1.53 2 100 76 15 3 2 1 199 Lower Kernels, 3.46 109 75 9 3 2 198 Average Kernels, 2.69 45 110 30 8 4 1 1 199 Here, as in case of wheat and barley, the light seeds were slower to germinate. In general, it would appear that, other things being equal, stronger and more perfect plants and larger crops are produced from heavy than from small seeds. Many comparisons are on record that have given such results ; not only small trials in garden plats, but also field experiments on a larger scale. Lehmann sowed, on each of three plats of 92 square feet, the same number (528) of peas, of the same kind but of different weight, with results as here tabulated Weights of 100 No. of Yield (grams). seed-peas, plants. Kernels. Pods. Straw. Total. Small seed-peas, 160 gm. 423 998 280 2010 3288 Medium seed-peas, 221 " 478 1495 357 2630 4482 Large seed-peas, 273 " 480 1814 437 3170 5421 Of the peas sown, there failed to germinate about 9 344 HOW CEOPS GEOW. per cent, both of the large and medium sizes, and 20 per cent of the small ones. The total produce from the small seeds was less abun- dant in all respects than that of the medium, and this less than that of the large seeds. Calculated upon the same number of plants, the differ- ences, though less in degree, are still very decided : 100 Plants Yielded Kernels. Pods. Straw. Total. From small seeds, 236 66 475 777 From medium seeds, 313 75 550 938 From large seeds, 378 91 660 1129 Lehmann, in another experiment, found that from the same weight of seed a larger crop is given by large seed than by small, although the number of plants may be considerably less. From the same weight (188 gin.) of seed-peas were produced : Number of Weight of Kernels Seed-peas. Plants. per 92 sq.ft. Per 100 plants. By small seed, 780 680 1590 234 By medium seed, 530 505 2224 440 By large seed, 384 360 2307 640 DriesdorfE sowed separately, on the same land, winter wheat, as winnowed, and the same divided by sifting into three sizes. In April and May the vegetation from the largest seed was evidently in advance, and at harvest the relative yield for 100 of unsifted seed was 121 from the largest, 105 for the medium, and 95 for the smallest seed. Improved varieties are often the result of continued breeding from the heaviest or largest seeds, accompanied by high culture on rich soil, and thin planting, so that the roots have abundant earth for unhindered develop- ment. Hallet, in 1857, selected two ears of Nursery Wheat, " the finest quality of red wheat grown in England," con- taining, together, 87 grains, and planted the kernels 12 inches apart every way. At harvest one prime grain REPRODUCTIVE ORGANS OF PLANTS. 345 produced 10 ears, that contained in the aggregate 688 kernels. The finest 10 ears that could be selected from the whole produce of the other 86 grains yielded but 598 kernels. The 79 kernels of the one best ear were planted as before, and the produce of the finest seed, as shown by the harvest, was used for the next year's sow- ing. The results of continuing this process of selection are tabulated below : Number of Length, Containing, ears on Year. inches. grains. finest stool. 1857. Original 4f 47 1858. Finest ear, 6J 79 10 1859. Finest ear 7| 91 22 1860. Ears imperfect from wet season, ... 39 1861. Finest ear, gf 123 52 In five years, accordingly, the length of the ears was doubled, their contents nearly trebled, and the tillering capacity of tbe plant increased five-fold. (Journal Royal Ag. Soc., XXII, p. 374.) Wollny has given account of 27 garden trials, with large and small seeds of rye, buckwheat, beans, vetches, peas, lupins, soybeans, colza, mustard, maize, and red- clover, on plats of four square meters (43 sq. ft.), during the years 1873 to 1880, with the nearly invariable results : 1, that the quantity of crop increases with the size of the seed ; 2, that the large seed produces principally large seed, and the small seed small ; 3, that the relative productiveness of the small seed is greater than that of the large ; and 4, that the vitality of the plants from small seed is usually less than that of the plants from large seed. The facts of experience fully justify the conclusion that, in general, other things being equal, the heaviest seed is the best. Signs of Excellence. So far as the common judg- ment can determine by external signs, the best seed is that which, on the one hand, is large, plump, and heavy, and on 346 HOW CEOPS GEOW. the other is fresh or bright to the eye, and free from musty odor. The large, plump, and heavy seeds are those which have attained the fullest development, and can best support the embryo when it shall begin to grow ; those fresh in color and odor are likely to be new, and to have the most vigorous vitality. Ancestry ; Race-Vigor ; Constancy. There are, however, important qualities in seed that are involved in their heredity and give no outward token of their pres- ence. Race-vigor and Constancy are qualities of this sort, and these wonderfully persist in some kinds of seed and are lacking in others. All cultivated plants occur in numerous varieties, and, as the years go on, older varieties "run out " or are neglected and forgotten, their place being taken by newer and often, or for a time, bet- ter ones. It would appear that a long course of careful cultivation under the most favorable and uniform condi- tions, coupled with careful and intelligent selection of seed from the best-developed plants, not only leads to the formation of the best varieties, but tends to establish their permanence, so that when soil, climate, and care are unfavorable, the kind maintains its character and makes a stout resistance to deteriorating influences. In order to properly appreciate the value of seed, its Pedigree must therefore be known. But seed of ances- try, that has a long-established character for certain qualities, in a given locality, may prove of little value under widely different circumstances, or, if its products be cultivated under new conditions, it may lose its char- acteristics more or less, and develop into other varieties. It is well known that various perennial plants of tropical climates, like the castor bean, become annuals in north- ern latitudes, and it may easily happen that the seed of some prized variety which is of unquestioned pedigree, as far as the remote lines of its descent can indicate, is of lit- tle worth in soils or climates to which it is unaccustomed, REPEODUCTIVE ORGANS OF PLANTS. 347 from not having the power to transmit the specially valuable qualities of its progenitors. In high, northern latitudes, the summer cereals ripen after a short period of rapid growth, but seed of such grain, sown in the soil of temperate regions, does not produce early varieties ; its rate of growth, after a few years at most, is 'governed by the climate to which it is exposed. In considering the pedigree of seed, therefore, it is not merely the repute or. characters of the ancestry, but the probability that the ancestral excellencies reside in and will be trans- mitted by the seed, that constitutes the practical point. DIVISION III. LIFE OF THE PLANT. CHAPTER I. GERMINATION. 1- \ INTRODUCTORY. Having traced the composition of vegetation from its ultimate elements to the proximate organic compounds, and studied its structure in the simple cell as well as in the most highly-developed plant, and, as far as needful, explained the characters and functions of its various organs, we approach the subject of VEGETABLE LIFE and NUTRITION, and are ready to inquire how the plant increases in bulk and weight and produces starch, sugar, oil, albuminoids, etc., which constitute directly or in- directly almost the entire food of animals. The beginning of the agricultural plant is in the flower, at the moment of fertilization by the action of a pollen tube on the contents of the embryo-sack. Each embryo whose development is thus ensured is a plant in miniature, or rather an organism that is capable, under proper circumstances, of unfolding into a plant. 349 350 HOW CEOPS GROW. The first process of development, wherein the young plant commences to manifest its separate life, and in which it is shaped into its proper and peculiar form, is called germination. The GENEEAL PEOCESS and CONDITIONS of GEEMIN- ATION are familiar to all. In agriculture and ordinary gardening we bury the ripe and sound seed a little way in the soil, and in a few days, or weeks, it usually sprouts, provided it finds a certain degree of warmth and moisture. Let us attend somewhat in detail first to the phenom- ena of germination and afterward to the requirements of the awakening seed. 2. THE PHENOMENA OP GERMINATION. The student will do well to watch with care the various stages of the act of germination, as exhibited in several species of plants. For this purpose a dozen or more seeds of each plant are sown, the smaller, one-half, the larger, one inch deep, in a box of earth or sawdust, kept duly warm and moist, and one or two of each kind are uncovered and dissected at successive intervals of 12 hours until the process is complete. In this way it is easy to trace all the visible changes which occur as the J embryo is quickened. The seeds of the kidney-bean, pea, of maize, buckwheat, and barley, may be employed. We thus observe that the seed first absorbs a large amount of moisture, in consequence of which it swells and becomes more soft. We see the germ enlarging be- neath the seed coats, shortly the integuments burst and the radicle appears, afterward the plumule becomes manifest. In a 1 ! agricultural plants the radicle buries itself in GEBMINATIOH. 351 the soil. The plumule ascends into the atmosphere and seeks exposure to the direct light of the sun. The endosperm, if the seed have one, and in many cases the cotyledons (so with the horse-bean, pea, maize, and barley), remain in the place where the seed was deposited. In other cases (kidney-bean, buckwheat, squash, radish, etc.) the cotyledons ascend and become the first pair of leaves. The ascending plumule shortly unfolds new leaves, and, if coming from the seed of a branched plant, lateral buds make their appearance. The radicle divides and subdivides in beginning the issue of true roots. When the plantlet ceases to derive nourishment from the mother-seed the process is finished. 3. THE CONDITIONS OP GEEMINATION. As ta the Conditions of Germination we have to con- sider in detail the following : a. Temperature. Seeds sprout within certain more or less narrow limits of warmth. Sachs has approximately ascertained, for various agri- cultural seeds, the limits of warmth at which germina- tion is possible. The lowest temperatures range from below 40 to 55, the highest, from 102 to 116. Below the minimum temperature a seed preserves its vitality, above the maximum it is killed. He finds, likewise, that the point at which the most rapid germination occurs is intermediate between these two extremes, and lies be- tween 79 and 93. Either elevation or reduction of temperature from these degrees retards the act of sprouting. In the following table are given the special tempera* tures for six common plants : 352 HOW CROPS GROW. Lowest Highest Temperature of most Temperature. Temperature, rapid Germination. Wheat,* 40 F. 104 F. 84 F. - Barley, 41 104 84 Pea, 44.5 102 84 Maize, 48 115 93 Scarlet-bean, 49 ill 79 Squash, 54 115 93 For the agricultural plants cultivated in New England, a range of temperature of from 55 to 90 is adapted for healthy and speedy germination. It will be noticed in the above Table that the seeds of plants introduced into northern latitudes from tropical regions, as the squash, bean, and maize, require and endure higher temperatures than those native to temper- ate latitudes, like wheat and barley. The extremes given above are by no means so wide as would be found were we to experiment with other plants. Some seeds will germinate near 32, the freezing point of water, as is true of wheat, rye, and water-cress, as well as of various alpine plants that grow in soil wet with the constant drip from melting ice. On the other hand, the cocoa- nut is said to yield seedlings with greatest certainty when the heat of the soil is 120. Sachs has observed that the temperature at which germination takes place materially influences the relative development of the parts, and thus the form, of the seed- ling. Very low temperatures retard the production of new rootlets, buds, and leaves. The rootlets which are rudimentary in the embryo become, however, very long. On the other hand, very high temperatures cause the rapid formation of new roots and leaves, even before those existing in the germ are fully unfolded. The medium and most favorable temperatures bring the parts of the embryo first into development, at the same time the rudiments of new organs are formed which are afterwards to unfold. * Wheat, and probably barley, may, occasionally, germinate at, or very near, 32. GEBMINATION. 353 6. Moisture. A certain amount of moisture is indis- pensable to all growth. In germination it is needful that the seed should absorb water so that motion of the contents of the germ-cells can take place. Until the seed is more or less imbued with moisture, no signs of sprouting are manifested, and if a half-sprouted seed be allowed to dry the process of growth is effectually checked. The degree of moisture different seeds will endure or require is exceedingly various. The seeds of aquatic plants naturally germinate when immersed in water. The seeds of most agricultural plants, indeed, will quicken under water, but they germinate most health- fully when moist but not wet. Excess of water often causes seeds to rot. c. Oxygen Gas. Free Oxygen, as contained in the air, is likewise essential. Saussure demonstrated by ex- periment that proper germination is impossible in its absence, and cannot proceed in an atmosphere of other gases. The chemical activity of oxygen appears to be the means of exciting the growth of the embryo. d. Light. It has been erroneously taught that light is prejudicial to germination, and that therefore seed must be covered. (Johnston's Lectures on Ag. Chem. & Geology, 2d Eng. Ed., pp 226 and 227.) Nature does not bury seeds, but scatters them on the surface of the ground of forest and prairie, where they are, at the most, half -covered and by no means removed from the light. The warm and moist forests of tropical regions, which, though shaded, are by no means dark, are covered with sprouting seeds. The seeds of heaths, calceolarias, and some other ornamental plants, germinate best when un- covered, and the seeds of common agricultural plants will sprout when placed on moist sand or sawdust, with apparently no less certainty than when buried out of eight. *3 354 HOW CHOPS GROW. Finally, R. Hoffmann (Jaliresbericht Uber Agricullur Chem., 1864, p. 110) found, in special experiments with 24 kinds of agricultural seeds, that light exercises no appreciable influence of any kind on germination. The time required for Germination varies exceed- ingly according to the kind of seed. It is said that the fresh seeds of the willow begin to sprout within 12 hours after falling to the ground. Those of clover, wheat, and other grains, mostly germinate in three to -ten days. The fruits of the walnut, pine, and larch lie four to six weeks before sprouting, while those of some species of ash, beech, and maple are said not to germinate before the expiration of one and a half or two years. The starchy and thin-skinned seeds quicken most readily. The oily seeds are in general more slow, while such as are situated within thick and horny or other- wise resistant envelopes require the longest periods to excite growth. The time necessary for germination depends naturally upon the favorableness of other conditions. Cold and drought delay the process, when they do not check it altogether. Seeds that are buried deeply in the soil may remain for years, preserving, but not manifesting, their vitality, because they are either too dry, too cold, or have not sufficient access to oxygen to set the germ in action. Notice has already been made of the frequent presence in clover-seed, for example, of a small proportion of seeds that have a dense coat which prevents imbibition of water and delays their germination for long periods. See p. 335. To speak with precision, we should distinguish the time from planting the dry seed to the commencement of germination, which is marked by the rootlet becom- ing visible, and the period that elapses until the process is complete ; i. e., until the stores of the mother-seed are 6EBMINATION. 355 exhausted, and the young plant is wholly cast upon its own resources. At 41 F., in the experiments of Haberlandt, the root- let issued after four days, in the case of rye, and in five to seven days in that of the other grains and clover. The sugar-beet, however, lay at this temperature 22 days before beginning to sprout. At 51, the time was shortened about one-half in case of the seeds just mentioned. Maize required 11, kidney- beans 8, and tobacco 31 days at this temperature. At 65 the cereals, clover, peas, and flax began to sprout in one to two days ; maize, beans, and sugar-beet in three days, and tobacco in six days. The time of completion varies with the temperature much more than that of beginning. It is, for example, according to Sachs, at 4155 for wheat and barley 4045 days, at 95 100 " " 10-12 At a given temperature small seeds complete germina- tion much sooner than large ones. Thus at 55-60 the process is finished with beans in 3040 days. " maize in 30-35 " " wheat in 2*-25 " clover in 810 " These differences are simply due to the fact that the smaller seeds have smaller stores of nutriment for the young plant, and are therefore more quickly exhausted. Proper Depth of Sowing. The soil is usually the medium of moisture, warmth, etc., to the seed, and it affects germination only as it influences the supply of these agencies ; it is not otherwise essential to the pro- cess. The burying of seeds, when sown in the field or garden, serves to cover them away from birds and keep them from drying up. In the forest, at spring-time, we may see innumerable seeds sprouting upon the surface, or but half covered with decayed leaves. 356 HO^ CfeOPS GROW. While it is the nearly universal result of experience in temperate regions that agricultural seeds germinate most surely when sown at a depth not exceeding one or two inches, there are circumstances under which a widely different practice is admissible or even essential. In the light and porous soil of the gardens of New Haven, peas may be sown six to eight inches deep without detriment, and are thereby better secured from the ravages of the domestic pigeon. The Moqui Indians, dwelling upon the table lands of the higher Colorado, deposit the seeds of maize 12 or 14 inches below the surface. Thus sown, the plant thrives, while, if treated according to the plan usual in the United States and Europe, it might never appear above ground. The reasons for such a procedure are the fol- lowing : The country is without rain and almost with- out dew. In summer the sandy soil is continuously parched by the sun, at a temperature often exceeding 100 in the shade. It is only at the depth of a foot or more that the seed finds the moisture needful for its growth moisture furnished by the melting of the winter snows.* E. Hoffmann, experimenting in a light, loamy sand, upon 24 kinds of agricultural and market-garden seeds, found that all perished when buried 12 inches. When planted 10 inches deep, peas, vetches, beans, and maize, alone came up ; at 8 inches there appeared, besides the above, wheat, millet, oats, barley, and colza ; at 6 inches, those already mentioned, together with winter colza, buckwheat, and sugar-beets ; at 4 inches of depth the above and mustard, red and white clover, flax, horse- radish, hemp, and turnips ; finally, at 3 inches, lucern also appeared. Hoffmann states that the deep-planted seeds generally sprouted most quickly, and all early dif- * For these Interesting facts, the writer is indebted to Prof. J. S. Newberry. GERMINATION. 357 ferences in development disappeared before the plants blossomed. On the other hand, Grouven, in trials with sugar-beet seed made, most probably, in a well-manured and rather heavy soil found that sowing at a depth of three-eighths to one and a fourth inches gave the earliest and strongest plants ; seeds deposited at a depth of two and a half inches required five days longer to come up than those planted at three-eighths of an inch. It was further shown that seeds sown shallow, in a fine wet clay, required four to five days longer to come up than those placed at the same depth in the ordinary soil. Not only the character of the soil, which influences the supply of air and warmth, but the kind of weather which determines both temperature and degree of moist- ure, have their effect upon the time of germination, and since these conditions are so variable, the rules of prac- tice are laid down, and must be received, with a certain latitude. 4. THE CHEMICAL PHYSIOLOGY OP GERMINATION. THE NUTRITION OF THE SEEDLING. The young plant grows at first exclusively at the expense of the seed. It may be aptly compared to the suckling animal, which, when new-born, is incapable of providing its own nourishment, but depends upon the milk of its mother. The Nutrition of the Seedling falls into three pro- cesses, which, though distinct in character, proceed sim- ultaneously. These are : 1, Solution of the Nutritive Matters of the Cotyledons or Endosperm ; 2, Transfer ; and 3, Assimilation of the same. 1. The Act of Solution has no difficulty JL case of 358 HOW CROPS GROW. dextrin, gum, the sugars, and soluble proteids. The water which the seed imbibes, to the extent of one-fourth to five-fourths of its weight, at once dissolves them. It is otherwise with the fats or oils, with starch and with proteids, which, as such, are nearly or altogether insoluble in water. In the act of germination provision is made for transforming these bodies into the soluble ones above mentioned. So far as these changes have been traced, they are as follows : Solution of Fats. Sachs was the first to show that squash-seeds, which, when ripe, contain no starch, sugar, or dextrin, but are very rich in oil (50%) and albuminoids (40%), suffer by germination such chemical change that the oil rapidly diminishes in quantity (nine- tenths disappear), while, at the same time, starch, and in some cases sugar, is formed. (Vs. St., Ill, p. ].) Solution of Starch. The starch that is thus organized from the fat of the oily seeds, or that which exists ready-formed in the farinaceous (floury) seeds, undergoes further changes, which have been previously alluded to (p. 50), whereby it is converted into substances that are soluble in water, viz., dextrin and dextrose. Solution of Albuminoids. Finally, the insoluble al- buminoids are gradually transformed into soluble modi- fications. Chemistry of Malt. The preparation and proper- ties of malt may serve to give an insight into the nature of the chemical metamorphoses that have just been indicated. The preparation is in this wise. Barley or wheat (sometimes rye) is soaked in water until the kernels are soft to the fingers ; then it is drained and thrown up in heaps. The masses of soaked grain shortly dry, become heated, and in a few days the embryos send forth their radicles. The heaps are shoveled over, and spread out so as to avoid too great a rise of temperature, and when GERMINATION. 359 the sprouts are about half an inch in length, the germin- ation is checked by drying. The dry mass, after remov- ing the sprouts (radicles), is malt, such as is used in the manufacture of beer. Malt thus consists of starchy seeds, whose germination has been checked while in its early stages. The only product of the beginning growth the sprouts being removed, it exhibits in the residual seed the first results of the process of solution. The following figures, derived from the researches of Stein, in Dresden ( Wilda's Centralblatt, 1860, 2, pp. 8- 23), exhibit the composition of 100 parts of Barley, and of the 92 parts of Malt, and the two and a half of Sprouts which 100 parts of Barley yield.* , , 100 pts. of ) _ ( 92 pts. of ) , ( 2J of > , Composition of Barley. | = { >Ialt. j + { Sprouts. } + Ash, 2.42 2.11 0.29 Starch, 54.48 47.43 Fat, 3.56 2.09 0.08 tasoluble Albuminoids, 11.02 9.02 0.37 Soluble Albuminoids 1.26 1.96 0.40 Dextrin, t 6.50 6.951 Extractive Matters (soluble in 0.47 water and destitute of nitrogen) 0.90 3.68 ) Cellulose, 19.86 18.76 0.89 100. 92. 2.5 It is seen from the above statement that starch, fat, and insoluble albuminoids have diminished in the malt- ing process ; while soluble albuminoids, dextrin, and other soluble non-nitrogenous matters have somewhat increased in quantity. "With exception of 3% of soluble "extractive matters," \ the differences in composition between barley and malt are not striking. The analyses refer to the materials in the dry state. Ordinarily they contain from 10 to 16 per cent of water. It must not be omitted to mention that the proportions of malt and sprouts, as well as their composition, vary somewhat according to circumstances ; and further- more, the best analyses which it is possible to make are but approxi- mate. t Later investigators deny the existence of dextrin in barley, but find, instead, amidulin and amylan. See p. 62, note. t The term extractive matters is here applied to soluble substances, whose precise nature is not understood. They constitute a mixture which the chemist to not able to analyze. 360 OW CROPS GROW. The properties of the two are, however, remarkably different. If malt be pulverized and stirred in warm water (155 F.) for an hour or two, the whole of the starch disappears, while sugar and dextrin take its place. The former is recognized by the sweet taste of the wort. as the solution is called. On heating the wort to boiling, a little albuminoid is coagulated, and may be separ- ated by filtering. This comes in part from the trans- formation of the insoluble albuminoids of the barley. On adding to the filtered liquid its own bulk of alcohol, dextrin becomes evident, being precipitated as a white powder. Furthermore, if we mix two to three parts of starch with one of malt, we find that the whole undergoes the same change. An additional quantity of starch remains unaltered. The process of germination thus develops in the seed an agency by which the conversion of starch into soluble carbhydrates is accomplished with great rapidity. Diastase Payen & Persoz attributed this action to the nitrogenous ferment which they termed Diastase, and which is found in the germinating seed in the vicin- ity of the embryo, but not in the radicles. They assert that one part of diastase is capable of transforming 2,000 parts of starch, first into dextrin and finally into sugar, and that malt yields one five-hundredth of its weight of this substance. See p. 103. A short time previous to the investigations of Payen & Persoz (1833), Saussure found that Muceclin,* the soluble nitrogenous body which may be extracted from gluten (p. 92, note), transforms starch- in the manner above described, and it is now known that various albu- minoids may produce the same effect, although the rap- * Saussure designated this body mncln, but this term being established as the name of the characteristic ingredient of animal mucus, Kitthau- sea has replaced it by mucedin. GERMINATION. 361 idity of the action and the amount of effect are usually far less than that exhibited by the so-called diastase. It must not be forgotten, however, that in all cases in which the conversion of starch into dextrin and sugar ia accomplished artificially, an elevated temperature is re- quired, whereas, in the natural process, as shown in the germinating seed, the change goes on at ordinary or even low temperatures. It is generally taught that oxygen, acting on the albu- minoids in presence of water, and within a certain range of temperature, induces the decomposition which confers on them the power in question. The necessity for oxygen in the act of germination has been thus accounted for, as needful to the solution of the starch, etc., of the cotyledons. This may be true at first, but, as we shall presently see, the chief action of oxygen is probably of another kind. How diastase or other similar substances accomplish the change in question is not certainly known. Soluble Starch. The conversion of starch into sugar and dextrin is thus in a sense explained. This is not, however, the only change of which starch is suscepti- ble. In the bean (Phaseol- us multiflorus) Sachs (Sitz- ungsberichte der Wiener Akad., XXXVII, 57) in- forms us that the starch of the cotyledons is dissolved, passes into the seedling, and reappears (in part, at least) as starch, without conver- sion into dextrin or sugar, as these substances do not appear in the cotyledons during any period of germination, except in small quantity near $e joining of #M? seedling, Compare p, 3, Fig. 65. 362 HOW CROPS GROW. The same authority gives the following account of the microscopic changes observed in the starch-grains them- selves, as they undergo solution. The starch-grains of the bean have a narrow interior cavity (as seen in Fig. 65, 1). This at first becomes filled with a liquid. Next, the cavity appears enlarged (2), its borders assume a corroded appearance (3, 4), and frequently channels are seen extending to the surface (4, 5, 6). Finally, the cavity becomes so large, and the channels so extended, that the starch-grain falls to pieces (7, 8). Solution continues on the fragments until they have completely disappeared. Soluble Albuminoids. The insoluble proteids of the seed are gradually transferred to the young plant, probably by ferment-actions similar to those referred to under the heading " Proteoses and Peptones," p. 100. The production of small quantities of acetic and lactic acids (the acids of vinegar and of sour milk) has been observed in germination. These acids perhaps assist in the solution of the albuminoids. Gaseous Products of Germination. Before leav- ing this part of our subject, it is proper to notice some other results of germination which have been thought to belong to the process of solution. On referring to the table of the composition of malt, we find that 100 parts of dry barley yield 92 parts of malt and 2% of sprouts, leaving 5 parts unaccounted for. In the malting pro- cess, 1 parts of the grain are dissolved in the water in which it is soaked. The remaining 4 parts escape into the atmosphere in the gaseous form. Of the elements that assume the gaseous condition, carbon does so to the greatest extent. It unites with atmospheric oxygen (partly with the oxygen of the seed, according to Oudemans), producing carbonic acid gas (C0 2 ). Hydrogen is likewise separated, partly in union with oxygen, as water (H?0), but to some degree GERMINATION. 363 in the free state. Free nitrogen appears in considerable amount (Schulz, Jour, far Prakt. Chem., 87, p. 163), while very minute quantities of Hydrogen and of Nitro- gen combine to gaseous ammonia (NH 3 ). Heat developed in Germination. These chemical changes, like all processes of oxidation, are accompanied with the production of heat. The elevation of temper- ature may be imperceptible in the germination of a sin- gle seed, but the heaps of sprouting grain seen in the malt-house, warm so rapidly and to such an extent that much care is requisite to regulate the process ; otherwise the malt is damaged by over-heating. 2. The Transfer of the Nutriment of the Seed- ling from the cotyledons or endosperm where it has un- dergone solution, takes place through the medium of the water which the seed absorbs so largely at first. This water fills the cells of the seed, and, dissolving their con- tents, carries them into the young plant as rapidly as they are required. The path of their transfer lies through the point where the embryo is attached to the cotyle- dons ; thence they are distributed at first chiefly down- wards into the extending radicles, after a little while both downwards and upwards toward the extremities of the seedling. Sachs has observed that the carbhydrates (sugar and dextrin) occupy the cellular tissue of the rind and pith, which are penetrated by numerous air-passages ; while at first the albuminoids chiefly diffuse themselves through the intermediate cambial tissue, which is destitute oi air-passages, and are present in largest relative quantity at the extreme ends of the rootlets and of the plumule. In another chapter we shall notice at length the phe- nomena and physical laws which govern the diffusion oi liquids into each other and through membranes similar to those which constitute the walls of the cells of plants, and there shall be able to gather some idea of the causes 364 HOW CEOPS QBOW. which set up and maintain the transfer of the materials of the seed into the infant plant. ,3. Assimilation is the conversion of the transferred nutriment into the substance of the plant itself. This process involves two stages, the first being a chemical, the second, a structural transformation. The chemical changes in the embryo are, in part, simply the reverse of those which occur in the cotyle- dons; viz., the soluble and structureless proximate prin- ciples are metamorphosed into the insoluble and organ- ized ones of the same or similar chemical composition. Thus, dextrin may pass into cellulose, and the soluble albuminoids may revert in part to the insoluble condi- tion in which they existed in the ripe seed. But many other and more intricate ehanges proceed in the act of assimilation. With regard to a few of these we have some imperfect knowledge. Dr. Sachs informs us that when the embryo begins to grow, its expansion at first consists in the enlargement of the ready-formed cells. As a part elongates, the starch which it contains (or which is formed in the early stages of this extension) disappears, and sugar is found in its stead, dissolved in the juices of the cells. When the organ has attained its full size, sugar can no longer be detected ; while the walls of the cells are found to have grown both in circumference and thickness, thus indicating the accumulation of cellulose. Oxygen Gas needful to Assimilation. Traube has made some experiments, which prove conclusively that the process of assimilation requires free oxygen to surround and to be absorbed by the growing parts of the germ. This observer found that newly-sprouted pea- seedlings continued to develop in a normal manner when the cotyledons, radicles, and lower part of the stem were withdrawn from the influence of oxygen by coat- ing with varnish or oil. On the other hand, when the GERMINATION. 365 tip of the plumule, for the length of about an inch, was coated with oil thickened with chalk, or when by any means this part of the plant was withdrawn from contact with free oxygen, the seedling ceased to grow, withered, and shortly perished. Traube observed the elongation of the stem by the following expedient. A young pea-plant was fastened by the cotyledons to a rod, and the stem and rod were both graduated by deli- cate cross-lines, laid on at equal intervals, by means of a brush dipped in a mixture of oil and indigo. The growth of the stem was now manifest by the widening of the spaces between the lines ; and, by comparison with those on the rod, Traube remarked that no growth took place at a distance of more than ten to twelve lines from the base of the terminal bud. Here, then, is a coincidence which appears to demon- strate that free oxygen must have access to a growing part. The fact is further shown by varnishing one side of the stem of a young pea. The varnished side ceases to extend, the uncoated portion continues enlarging, which results in a curvature of the stem. Traube further indicates in what manner the elabora- tion of cellulose from sugar may require the co-operation of oxygen and evolution of carbon dioxide, as expressed by the subjoined equation. Glucose. Oxygen. Carbon dioxide. Water. Cellulose. 2(C 12 H 14 12 ) + 240 = 12 (CO,) + 14 (H,O) + C^H^d,,. When the act of germination is finished, which occurs as soon as the cotyledons and endosperm are exhausted of all their soluble matters, the plant begins a fully inde- pendent life. Previously, however, to being thus thrown upon its own resources, it has developed all the organs needful to collect its food from without ; it has unfolded its perfect leaves into the atmosphere, and pervaded 9 portion of soil with its rootlets. 366 HOW CROPS GROW. During the latter stages of germination it gathers its nutriment both from the parent seed and from the exter- nal sources which afterward serve exclusively for its support. Being fully provided with the apparatus of nutrition, its development suffers no check from the exhaustion of the mother seed, unless it has germinated in a sterile soil, or under other conditions adverse to vegetative life. CHAPTER II. 1. THE FOOD OF THE PLANT WHEN" INDEPENDENT OF THE SEED. This subject will be sketched in this place in but the briefest outlines. To present it fully would necessitate entering into a detailed consideration of the Atmosphere and of the Soil, whose relations to the Plant, those of the soil especially, are very numerous and complicated. A separate volume is therefore required for the adequate treatment of these topics. The Roots of a plant, which are in intimate contact with the soil, absorb thence the water that fills the active cells ; they also imbibe such salts as the water of the soil holds in solution ; they likewise act directly on the soil, and dissolve substances, which are thus first made of avail to them. The compounds that the plant must derive from the soil are those which are found in its ash, since these are not volatile, and cannot, therefore, exist in the atmosphere. The root, however, commonly takes FOOD AFTER GERMINATION. 367 up some other elements of its nutrition to which it has immediate access. Leaving out of view, for the present, those matters which, though found in the plant, appear to be unessential to its growth, viz., silica and sodium salts, the roots absorb the following substances, viz. : Sulphates "I f Potassium, Phosphates , | Calcium, Nitrates and f Magnesium and Chlorides _ Iron. These salts enter the plant by the absorbent surfaces of the younger rootlets, and pass upwards, through the stem, to the leaves and to the new-forming buds. The Leaves, which are unfolded to the air, gather from it Carbon dioxide Gas. This compound suffers decomposition in the plant ; its Carbon remains there, its Oxygen or an equivalent quantity, very nearly, is thrown off into the air again. The decomposition of carbon dioxide takes place only by day and under the influence of the sun's light. From the carbon thus acquired and the elements of water with the co-operation of the ash-ingredients, the plant organizes the Carbhydrates. Probably some of the glucoses are the first products of this synthesis. Starch, in the form of granules, is the first product that is recognizable by help of the microscope. The formation of carbhydrates appears to proceed in the chlorophyl-cells of the leaf, where starch-granules first make their appearance. The Albuminoids require for their production the presence of a compound of Nitrogen. The salts of Nitric Acid (nitrates) are commonly the chief, and may be the only, supply of this element. ' The other proximate principles, the fats, the alkaloids, and the acids, are built up from the same food-elements. In most cases the steps in the construction of organic matters are unknown to us, or subjects of uncertain con- jecture. HOW CHOPS GEOW. The carbhydrates, albuminoids, etc., that are organ- ized in the foliage, are not only transformed into the solid tissues of the leaf, but descend and diffuse to every active organ of the plant. The plant has, within certain limits, a power of select- ting its food. The sea- weed, as has been remarked, contains more potash than soda, altbough the latter is 30 times more abundant than the former in the water of the ocean. Vegetation cannot, however, entirely shut out either excess of nutritive matters or bodies that are of no use or even poisonous to it. The functions of the Atmosphere are essentially the same towards plants, whether growing under the con- ditions of water-culture or under those of agriculture. The Soil, on the other hand, has offices which are pe- culiar to itself. We have seen that the roots of a plant have the power to decompose salts, e. g., potassium nitrate and ammonium chloride (p. 184), in order to appropriate one of their ingredients, the other being rejected. In water-culture, the experimenter must have a care to remove the substance which would thus accu- mulate to the detriment of the plant. In agriculture, the soil, by virtue of its chemical and physical qualities, commonly renders such rejected matters comparatively insoluble, and therefore innocuous. The Atmosphere is nearly invariable in its composi- tion at all times and over all parts of the earth's surface. Its power of directly feeding crops has, therefore, a nat- ural limit, which cannot be increased by art. The Soil, on the other hand, is very variable in com- position and quality, and may be enriched and improved, or deteriorated and exhausted. From the Atmosphere the crop can derive no appreci- able quantity of those elements that are found in its Ash. In the Soil, however, from the waste of both plants MOTION OP THE JUICES. 369 animals, may accumulate large supplies of all the elements of the Volatile part of Plants. Carbon, cer- tainly in the form of carbon dioxide, probably or possi- bly in the condition of Humus (Vegetable Mold; Swamp Muck), may thus be put as food, at the disposition of the plant. Nitrogen is chiefly furnished to crops by the soil. Nitrates are formed in the latter from various sources, and ammonia-salts, together with certain proxi- mate animal principles, viz., urea, guanin, tyrosin, uric acid and hippuric acid, likewise serve to supply nitrogen to vegetation and are often ingredients of the best ma- nures. It is, too, from the soil that the crop gathers all the Water it requires, which not only serves as the fluid medium of its chemical and structural metamorphoses, but likewise must be regarded as the material from which it mostly appropriates the Hydrogen and Oxygen of its solid components. * THE JUICES OF THE PLANT, THEIB NATUBE AND MOVEMENTS. Very erroneous notions have been entertained with regard to the nature and motion of sap. It was formerly taught that there are two regular and opposite currents of sap circulating in the plant. It was stated that the "crude sap" is taken up from the soil by the roots, ascends through the vessels (ducts) of the wood, to the leaves, there is concentrated by evaporation, "elabor- ated" by the processes that go on in the foliage, and thence descends through the vessels of the inner bark, nourishing these tissues in its way down. The facts from which this theory of the sap naturally arose admit of a very different interpretation ; while numerous con- 24 370 HOW CEOPS GROW. eiderations demonstrate the essential falsity of the theory itself. Flow of Sap in the Plant not Constant or Necessary. We speak of the Flow of Sap as if a rapid current were incessantly streaming through the plant, as the blood circulates in the arteries and veins cf an ani- mal. This is an erroneous conception. A maple in early March, without foliage, with its whole stem enveloped in a nearly impervious bark, its buds wrapped up in horny scales, and its roots sur- rounded by cold or frozen soil, cannot be supposed to have its sap in motion. Its juices must be nearly or abso- lutely at rest, and when sap runs copiously from an ori- fice made in the trunk, it is simply because the tissues are charged with water under pressure, which escapes at any outlet that may be opened for it. The sap is at rest until motion is caused by a perforation of the bark and new wood. So, too, when a plant in early leaf is situa- ted in an atmosphere charged with moisture, as happens on a rainy day, there is little motion of its sap, although, if wounded, motion may be established, and water may stream more or less from all parts of the plant towards the cut. Sap does move in the plant when evaporation of water goes on from the surface of the foliage. This always happens whenever the air is not saturated with vapor. When a wet cloth hung out, dries rapidly by giving up its moisture to the air, then the leaves of plants lose their water more or less readily, according to the nature of the foliage. Mr. Lawes found that in the moist climate of England common plants (Wheat, Barley, Beans, Peas, and Clover) exhaled, during five months of growth, more than 200 times their (dry) weight of water. Hellriegel, in the drier climate of Dahme, Prussia, observed exhalation to average 300 times the dry weight of various common MOTION OF THE JUICES. 371 crops (p. 312). The water that thus evaporates from the leaves is supplied by the soil, and, entering the roots, more or less rapidly streams upwards through the stem as long as a waste is to be supplied, but this flow ceases when evaporation from the foliage is suppressed. The upward motion of sap is therefore to a great de- great independent of the vital processes, and compara- tively unessential to the welfare of the plant. Flow of Sap from the Plant ; " Bleeding." It is a familiar fact, that from a maple tree " tapped " in spring-time, or from a grape-vine wounded at the same season, a copious flow of sap takes place, which continues for a number of weeks. The escape of liquid from the vine is commonly termed " bleeding," and while this rapid issue of sap is thus strikingly exhibited in compar- atively few cases, bleeding appears to be a universal phe- nomenon, one that may occur, at least, to some degree, under certain conditions with very many plants. The conditions under which sap flows are various, according to the character of the plant. Our perennial trees have their annual period of active growth in the warm season, and their vegetative functions are nearly suppressed during cold weather. As spring approaches the tree renews its growth, and the first evidence of change within is furnished by its bleeding when an open- ing is made through the bark into the young wood. A maple, tapped for making sugar, loses nothing until the spring warmth attains a certain intensity, and then sap begins to flow from the wounds in its trunk. The flow is not constant, but fluctuates with the thermometer, being more copious when the weather is warm, and fall- ing off or suffering check altogether as it is colder. The stem of the living maple is always charged with water, and never more so than in winter.* This water * Experiments made In Tharand, Saxony, under direction of Stoeck- hardt, show that the proportion of water, both in the bark and wood 372 HOW CROPS GROW. is either pumped into the plant, so to speak, "by the root- power already noticed (p. 269), or it is generated in the trunk itself. The water contained in the stem in winter is undoubtedly that raised from the soil in the autumn. That which first flows from an auger-hole, in March, may be simply what was thus stored in the trunk ; but, as the escape of sap goes on for 14 to 20 days at the rate of several gallons per day from a single tree, new quantities of water must be continually supplied. That these are pumped in from the root is, at first thought, difficult to understand, because, as we have seen (p. 272), the root-power is suspended by a certain low tempera- ture (unknown in case of the maple), and the flow of eap often begins when the ground is covered with one or two feet of snow, and when we cannot suppose the soil to have a higher temperature than it had during the pre- vious winter months. Nevertheless, it must be that the deeper roots are warm enough to be active all the winter through, and that they begin their action as soon as the trunk acquires a temperature sufficiently high to admit the movement of water in it. That water may be pro- duced in the trunk itself to a slight extent is by no means impossible, for chemical changes go on there in spring-time with much rapidity, whereby the sugar of the sap is formed. These changes have not been suffi- ciently investigated, however, to prove or disprove the generation of water, and we must, in any case, assume that it is the root-power which chiefly maintains a pres- sure of liquid in the tree. The issue of sap from the maple tree in the sugar- season is closely connected with the changes of tempera- ture that take place above ground. The sap begins to of trees, varies considerably in different seasons of the year, ranging, in case of the beech, from 35 to 49 per cent of the fresh-felled tree. The greatest proportion of water in the wood was found in the months of December and January ; in the bark, in March to May. The minimum of water in the wood occurred in May, June, and July; in the bark, much irregularity was observed. Chem. Ackersmann, 1866, p. 159. MOTION OF THE JUICES. 373 flow from a cut when the trunk itself is warmed to a cer- tain point and, in general, the flow appears to be the more rapid the warmer the trunk. During warm, clear days, the radiant heat of the sun is absorbed by the dark, rough surface of the tree most abundantly ; then the 'jemperature of the latter rises most speedily and acquires the greatest elevation even surpasses that of the atmos- phere by several degrees ; then, too, the yield of sap is most copious. On clear nights, cooling of the tree takes place with corresponding rapidity ; then the snow or surface of the ground is frozen, and the flow of sap is checked altogether. From trees that have a sunny ex- posure, sap runs earlier and faster than from those hav- ing a cold northern aspect. Sap starts sooner from the spiles on the south side of a tree than from those towards the north. Dnchartre (Comptes Rendus, IX, 754) passed a vine situated in a grapery, out of doors, and back again, through holes, so that a middle portion of the stem was exposed to a steady winter temperature ranging from 18 to 10 F., while the remainder of the vine, in the house, was surrounded by an atmosphere of 70 F. Under these circumstances the buds within developed vigor- ously, but those without remained dormant and opened not a day sooner than buds upon an adjacent vine whose stem was all out of doors. That sap passed through the cold part of the stem was shown by the fact that the interior shoots sometimes wilted, but again recovered their turgor, which could only happen from the partial suppression and renewal of a supply of water through the stem. Payen examined the wood of the vine at the con- clusion of the experiment, and found the starch which it originally contained to have been equally removed from the warm and the exposed parts. That the rate at which sap passed through the stem was influenced by its temperature is a plain deduction 374 HOW CROPS GROW. from the fact that the leaves within were found wilted in the morning, while they recovered toward uoon, al- though the temperature of the air without remained below freezing. The wilting was no doubt chiefly due to the diminished power of the stem to transmit water ; the return of the leaves to their normal condition was probably the consequence of the warming of the stem by the sun's radiant heat.* One mode in which changes of temperature in the trunk influence the flow of sap is very obvious. The wood-cells contain, not only water, but air. Both are expanded by heat, and both contract by cold. Air, especially, undergoes a decided change of bulk in this way. Water expands nearly one-twentieth in being warmed from 32 to 212, and air increases in volume more than one-third by the same change of temperature. When, therefore, the trunk of a tree is warmed by the sun's heat, the air is expanded, exerts a pressure on the sap, and forces it out of any wound made through the bark and wood-cells. It only requires a rise of tempera- ture to the extent of a few degrees to occasion from this cause alone a considerable flow of sap from a large tree. (Hartig.) If we admit that water continuously enters the deep- lying roots whose temperature and absorbent power must remain, for the most part, invariable from day to day, we should have a constant slow escape of sap from the trunk were the temperature of the latter uniform and sufficiently high. This really happens at times during every sugar-season. When the trunk is cooled down to the freezing point, or near it, the contraction of air and water in the tree makes a vacuum there, sap ceases to flow, and air is sucked in through the spile ; as the trunk * The temperature of the air is not always a sure indication of that of the solid bodies which it surrounds. A thermometer will often rise by exposure of the bulb to the direct rays of the sun, 30 or 40 above its Indications when in the shade. MOTION OF THE JUICE3. 375 becomes heated again, the gaseous and liquid contents of the ducts expand, the flow of sap is renewed, and pro- ceeds with increased rapidity until the internal pressure passes its maximum. As the season advances and the soil becomes heated, the root-power undoubtedly acts with increased vigor and larger quantities of water are forced into the trunk, but at a certain time the escape of sap from a wound suddenly ceases. At this period a new phenomenon supervenes. The buds which were formed the previous summer begin to expand as the vessels are distended with sap, and finally, when the temperature attains the proper range, they unfold into leaves. At this point we have a proper motion of sap in the tree, whereas before there was little motion at all in the sound trunk, and in the tapped stem the motion was towards the orifice 'and thence out of the tree. The cessation of flow from a cut results from two cir- cumstances : first, the vigorous cambial growth, where- by incisions in the bark and wood rapidly heal up ; and, second, the extensive evaporation that goes on from foliage. That evaporation of water from the leaves often pro- ceeds more rapidly than it can be supplied by the roots is shown by the facts that the delicate leaves of many plants wilt when the soil about their roots becomes dry, that water is often rapidly sucked into wounds on the stems of trees which are covered with foliage, and that the proportion of water in the wood of the trees of tem- perate latitudes is least in the months of May, June, and July. Evergreens do not bleed in the spring-time. The oak loses little or no sap, and among other trees great diver- sity is noticed as to the amount of water that escapes at a wound on the stem. In case of evergreens we have a stem destitute of all proper vascular tissue, and admit- 376 HOW CROPS GROW. ting a flow of liquid only through perforations of the wood-cells, if theae really exist (which Sachs denies). Again, the leaves admit of continual evaporation, and furnish an outlet to the water. The colored heart-wood existing in many trees is impervious to water, as shown by the experiments of Boucherie and Hartig. Sap can only flow through the white, so-called sap-wood. In early June, the new shoots of the vine do not bleed when cut, nor does sap flow from the wounds made by break- ing them off close to the older stem, although a gash in the latter bleeds profusely. In the young branches, there are no channels that permit the rapid efflux of water. Composition of Sap. The sap in all cases consists chiefly of water. This liquid, as it is absorbed, brings in from the soil a small proportion of certain saline mat- ters the phosphates, sulphates, nitrates, etc., of potas- sium, calcium, and magnesium. It finds in the plant itself its organic ingredients. These may be derived from matters stored in reserve during a previous year, as in the spring sap of trees ; or may be newly formed, as in summer growth. The sugar of maple-sap, in spring, is undoubtedly pro- duced by the transformation of starch which is found abundantly in the wood in winter. According to Hartig (Jour, fttr Prakt. Ch., 5, p. 217, 1835), all deciduous trees contain starch in their wood and yield a sweet spring sap, while evergreens contain little or no starch. Hartig reports having been able to procure from the root- wood of the horse-chestnut in one instance no less than 26 per cent of starch. This is deposited in the tissues during summer and autumn, to be dissolved for the use of the plant in developing new foliage. In evergreens and annual plants the organic matters of the sap are derived more directly from the foliage itself. The leaves absorb carbon dioxide and unite its carbon to the eler MOTION OF THE JUICES. 37T ments of water, with the production of sugar and other carbhydrates. In the leaves, also, probably nitrogen from the nitrates and ammonia-salts gathered by the roots, is united to carbon, hydrogen, and oxygen, in the formation of albuminoids. Besides sugar, malic acid and minute quantities of proteids exist in maple sap. Towards the close of the sugar-season the sap appears to contain other organic substances which render the sugar impure, brown in color, and of different flavor. It is a matter of observation that maple-sugar is whiter, purer, and " grains " or crystallizes more readily in those years when spring-rains or thaws are least frequent. This fact would appear to indicate that the brown or- ganic matters which water extracts from leaf -mold may enter the roots of the trees, as is the belief of practical men. The spring-sap of many other deciduous trees of tem- perate climates contains sugar, but while it is cane sugar in the maple, in other trees it appears to consist mostly or entirely of dextrose. Sugar is the chief organic ingredient in the juice of the sugar cane, Indian corn, beet, carrot, turnip, and parsnip. The sap that flows from the vine and from many cul- tivated herbaceous plants contains little or no sugar ; in that of the vine, gum or dextrin is found in its stead. What has already been stated makes evident that we cannot infer the quantity of sap in a plant from what may run out of an incision, for the sap that thus issues is for the most part water forced up from the soil. It is equally plain that the sap, thus collected, has not the normal composition of the juices of the plant ; it must be diluted, and must be the more diluted the longer and the more rapidly it flows. Ulbricht has made partial analyses of the sap obtained 378 HOW CHOPS GROW. from the stumps of potato, tobacco, and sun-flower plants. He found that successive portions, collected separately, exhibited a decreasing concentration. In sunflower sap, gathered in fiye successive portions, the liter contained the following quantities (grams) of solid matter : 1. 2. 3. 4. 5. Volatile substance,... 1.45 0.60 0.30 0.25 0.21 Ash, 1.58 1.66 1.18 0.70 0.60 Total, sioi 2il6 7*8 0.95 O81 The water which streams from a wound dissolves and carries forward with it matters that, in the uninjured plant, would probably suffer a much less rapid and ex- tensive translocation. From the stump of a potato-stalk would issue, by the mere mechanical effect of the flow of water, substances generated in the leaves, whose proper movement in the uninjured plant would be downwards into the tubers. Different Kinds of Sap. It is necessary at this point in our discussion to give prominence to the fact that there are different kinds of sap in the plant. As we have seen (p. 289), the cross section of the plant pre- sents two kinds of tissue, the cellular and vascular. These carry different juices, as is shown by their chemi- cal reactions. In the cell-tissues exist chiefly the non- nitrogenous principles, sugar, starch, oil, etc. The liquid in these cells, as Sachs has shown, commonly con- tains also organic acids and acid-salts, and hence gives a red color to blue litmus. In the vascular tissue albumin- oids preponderate, and the sap of the ducts commonly has an alkaline reaction towards test papers. These dif- ferent kinds of sap are not, however, always strictly con- fined to either tissue* In the root-tips and buds of many plants (maize, squash, onion), the young (new- formed) cell-tissue is alkaline from the preponderance of MOTION OF THE JUICES. 370 albuminoids, while the spring sap flowing from the ducts and wood of the maple is faintly acid. In many plants is found a system of channels (milk- ducts, p. 304), independent of the vascular bundles, Which contain an opaque, white, or yellow juice. This liquid is seen to exude from the broken stem of the milk- weed (Asdepias), of lettuce, or of celandine (Chelidon- ium), and may be noticed to gather in drops upon a fresh-cut slice of the sweet potato. The milky juice often differs, not more strikingly in appearance than it does in taste, from the transparent sap of the cell-tissue and vascular bundles. The former is commonly acrid and bitter, while the latter is sweet or simply insipid to the tongue. Motion of the Nutrient Matters of the Plant. The occasional rapid passage of a current of water up wards through the plant must not be confounded with the normal, necessary, and often contrary motion of the nutrient matters out of which new growth is organized, but is an independent or highly subordinate process by which the plant adapts itself to the constant changes that are taking place in the soil and atmosphere as re- gards their content of moisture. A plant supplied with enough moisture to keep its tis- sues turgid is in a normal state, no matter whether the water Avithin it is nearly free from upward flow or ascends rapidly to compensate the waste by evaporation. In both cases the motion of the matters dissolved in the sap is nearly the same. In both cases the plant develops nearly alike. In both cases the nutritive matters gath- ered at the root- tips ascend, and those gathered by the leaves descend, being distributed to every growing cell ; and these motions are comparatively independent of, and but little influenced by, the motion of the water in which they are dissolved. Tb., IX, p. 1.) MOTION OF THE JUICES. 381 Fig. 01 for growth, as in moist, warm air, with its lower extremity in water, roots form chiefly at the edge of the bark just above the removed ring. The twisting, or half -breaking, as well as ringing of a layer, promotes the development of roots. Latent buds are often called forth on the stems of fruit trees, and branches grow more vigorously, by making a transverse incision through the bark just below the point of their issue. Girdling a fruit-bearing branch of the grape-vine near its junction with the older wood has the effect of greatly enlarging the fruit. It is well known that a wide wound made on the stem of a tree heals up by the formation of new wood, and commonly the growth is most rapid and abundant above the cut. From these facts it was concluded that sap descends in the bark, and, not being able to pass below a wound, leads to the organization of new roots or wood just above it. The accompanying illustration, Fig. 66, represents the base of a cut- ting from an exogenous stem (pear or currant), girdled at B and kept for some days immersed in water to the depth indicated by the line L. 382 HOW CHOPS GROW. The first maif estation of growth is the formation of a protuberance at the lower edge of the bark, which is known to gardeners as a callous, C. This is an extension of the cellular tissue. From the callous shortly appear rootlets, R, which originate from the vascular tissue. Rootlets also break from the stem above the callous and also above the water, if the air be moist. They appear, likewise, though in less number, below the girdled place. Nearly all the organic substances (carbhydrates, al- buminoids, acids, etc.) that are formed in a plant are produced in the leaves, and must necessarily find their way down to nourish the stem and roots. The facts just mentioned demonstrate, indeed, that they do go down in the bark. We have, however, no proof that there is a downward flow of sap. Such a flow is not indicated by a single fact, for, as we have before seen, the only current of water in the uninjured plant is the upward one which results from root-action and evapora- tion, and that is variable and mainly independent of the distribution of nutritive matters. Closer investigation has shown that the most abundant downward movement of the nutrient matters generated in the leaves proceeds in the thin-walled sieve-cells of the cambium, which, in exogens, is young tissue common to the outer wood and the inner bark which, in fact, unites bark and wood. The tissues of the leaves communicate directly with, and are a continuation of, the cambium, and hence matters formed by the leaves must move most rapidly in the cambium. If they pass with greatest freedom through the sieve-cells, the fact is simply demonstration that the latter communicate most directly with those parts of the leaf in which the matters they conduct are organized. In endogenous plants and in some exogens (Piper me- dium, Amaranthus sanguineus), the vascular bundles containing sieve-cells pass into the pith and are not con- fined to the exterior of the stem. Girdling such plants does not give the result above described. With them, roots are formed chiefly or entirely at the base of the cutting (Hanstein), and not above the girdled place. MOTION OF THE JUICES. 383 In all cases, without exception, the matters organized in the leaves, though most readily and abundantly mov- ing downwards in the vascular tissues, are not confined to them exclusively. When a ring of bark is removed from a tree, the new cell-tissues, as well as the vascular, are interrupted. Notwithstanding, matters are trans- mitted downwards, through the older wood. When but a narrow ring of bark is removed from a cutting, roots often appear below the incision, though in less number, and the new growth at the edges of a wound on the trunk of a tree, though most copious above, is still de- cided below goes on, in fact, all around the gash. Both the cell-tissue and the vascular thus admit of the transport of the nutritive matters downwards. In the former, the carbhydrates starch, sugar, inulin the fats, and acids, chiefly occur and move. In the large ducts, air is contained, except when by vigorous root- action the stem is surcharged with water. In the sieve- ducts (cambium) are found the albuminoids, though not unmixed with carbhydrates. If a tree have a deep gash cut into its stem (but not reaching to the colored heart- wood), growth is not suppressed on either side of the cut, but the nutritive matters of all kinds pass out of a vertical direction around the incision, to nourish the new wood above and below. Girdling a tree is not fatal, if done in the spring or early summer when growth is rapid, provided that the young cells, which form externally, are protected from dryness and other destructive influ- ences. An artificial bark, i. e., a covering of cloth or clay to keep the exposed wood moist and away from air, saves the tree until the wound heals over.* In these cases it is obvious that the substances which commonly preponderate in the sieve-ducts must pass through the * If the freshly exposed wood be rubbed or wiped with a cloth, whereby the moist cambial layer (of cells containing nuclei and capa- ble of multiplying) is removed, no growth can occur. Ratzeburg. 384 HOW CROPS GROW. cell-tissue in order to reach the point where they nourish the growing organs. Evidence that nutrient matters also pass upwards in the bark is furnished, not only by tracing the course of colored liquids in the stem, but also by the fact that undeveloped buds perish in most cases when the stem is girdled between them and active leaves. In the excep- tions to this rule, the vascular bundles penetrate the pith, and thereby demonstrate that they are the chan- nels of this movement. A minority of these exceptions again makes evident that the sieve-cells are the path of transfer, for, as Hanstein has shown, in certain plants (SolanacesB, Asclepiadeae, etc.), sieve-cells penetrate the pith unaccompanied by any other elements of the vascu- lar bundle, and girdled twigs of these plants grow above as well as beneath the wound, although all leaves above the girdled place be cut off, so that the nutriment of the buds must come from below the incision. The substances which are organized in the foliage of a plant, as well as those which are imbibed by the roots, move to any point where they can supply a want. Garb- hydrates pass from the leaves, not only downwards, to nourish new roots, but upwards, to feed the buds, flow- ers, and fruit. In case of cereals, the power of the leaves to gather and organize atmospheric food nearly or altogether ceases as they approach maturity. The seed grows at the expense of matters previously stored in the foliage and stems (p. 237), to such an extent that it may ripen quite perfectly although the plant be cut when the kernel is in the milk, or even earlier, while the juice of the seeds is still watery and before starch-grains have begun to form. In biennial root-crops, the root is the focus of motion for the matters organized by growth during the first year ; but in the second year the stores of the root are completely exhausted for the support of flowers and seed, CAUSES OF THE MOTION OF JUICES. 385 BO that the direction of the movement of these organized matters is reversed. In both years the motion of water is always the same, viz., from the soil upwards to the leaves. * The summing up of the whole matter is that the nutri- ent substances in the plant are not absolutely confined to any path, and may move in any direction. The fact that they chiefly follow certain channels, and move in this or that direction, is plainly dependent upon the structure and arrangement of the tissues, on the sources of nutriment, and on the seat of growth or other action. 3. THE CAUSES OF MOTION OF THE VEGETABLE JUICES. Porosity of Vegetable Tissues Porosity is a property of all the vegetable tissues and implies that the molecules or smallest particles of matter composing the tis- sues are separated from each other by a certain space. In a multitude of cases bodies are visibly porous. In many more we can see no pores, even by the aid of the highest magnifying powers of the microscope ; nevertheless the fact of porosity is a necessary inference from another fact which may be observed, viz., that of absorption. A fiber of linen, to the unassisted eye, has no pores. Under the microscope we 6nd that it is a tubular cell, the bore being much less than the thickness of the walls. By immersing it in water it swells, becomes more trans- parent, and increases in weight. If the water be colored by solution of indigo or cochineal, the fiber is visibly * The motion of water is always upwards, because the soil always contains more water than the air. If a plant were so situated that its roots should steadily lack water while its foliage had an excess of this liquid, it cannot be doubted that then the "sap" would pass down in a rej?ular flow. In this case, nevertheless, the nutrient matters would take their normal course. 25 386 HOW CROPS GROW. penetrated by the dye. It is therefore porous, not only in the sense of having an interior cavity which becomes visible by a high magnifying power, but likewise in hav- ing throughout its apparently imperforate substance in- numerable channels in which liquids can freely pass. In like manner, all the vegetable tissues are more or less penetrable to water. Imbibition of Liquids by Porous Bodies. Not oniv do the tissues of the plant admit of the access of water into their pores, but they forcibly drink in or aosoro tnis liquid, when it is presented to them in excess, until their pores are full. "When the molecules of a porous body have freedom of motion, they separate from each other on imbibing a liquid ; the body itself swells. Even powdered glass or fine sand perceptibly increases in bulk by imbibing water. Clay swells much more. Gelatinous silica, pectin, gum tragacanth, and boiled starch hold a vastly greater amount of water in their pores or among their molecules. In case of vegetable and animal tissues, or membranes, we find a greater Dr less degree of expansibility from the same cause, but here the structural connection of the molecules puts a limit to their separation, and the result of saturating them with a liquid is a state of turgidity and tension, which subsides to one of yielding flabbiness when the liquid is partially removed. The energy with which vegetable matters imbibe water may be gathered from a well-known fact. In granite quarries, long blocks of stone are split out by driving plugs of dry wood into holes drilled along the desired line of fracture and pouring water over the plugs. The liquid penetrates the wood with immense force, and the toughest rock is easily broken apart. The imbibing power of different tissues and vegetable matters is widely diverse. In general, the younger or- gans or parts take up water most readily and freely. The CAUSES OF THE MOTION OF JUICES. 38? sap-wood of trees is far more absorbent than the heart- wood and bark. The cuticle of the leaf is often com- paratively impervious to water. Of the proximate ele- ments we have cellulose and starch-grains able to retain, even when air-dry, 10 to 15% of water. "Wax and the solid fats, as well as resins, on the contrary, do not greatly attract water, and cannot easily be wetted with it. They render cellulose, which has been impregnated with them, unabsorbent. Those vegetable substances which ordinarily manifest the greatest absorbent power for water, are the gummy carbhydrates and the albuminoids. In the living plant the protoplasmic membrane exhibits great absorbent power. Of mineral matters, gelatinous silica (Exp. 58, p. 137) is remarkable on account of its attraction for water. Not only do different substances thus exhibit unlike adhesion to water, but the same substance deports itself variously towards different liquids. One hundred parts of dry ox-bladder were found by Liebig to absorb during 24 hours : 268 parts of pure "Water. 133 " " saturated Brine. 38 " " Alcohol (84%). 17 " " Bone-oil. A piece of dry leather will absorb either oil or water, and apparently with equal avidity. If, however, oiled leather be immersed in water, the oil is gradually and perfectly displaced, as the farmer well knows from his experience with greased boots. India-rubber, on the other hand, is impenetrable to water, while oil of tur- pentine is imbibed by it in large quantity, causing the caoutchouc to swell up to a pasty mass many times its original bulk. The absorbent power is influenced by the size of the pores. Other things being equal, the finer these are, the greater the force with which a liquid is imbibed. This 388 HOW CROPS GROW. is shown by what has been learned from the study of a kind of pores whose eifect admits of accurate measure- ment. A tube of glass, with a narrow, uniform caliber, is such a pore. In a tube of 1 millimeter (about ^ of an inch), in diameter, water rises 30 mm. In a tube of -fa millimeter, the liquid ascends 300 mm. (about 11 inches) ; and, in a tube of T T mm., a column of 3,000 mm. is sustained. In porous bodies, like chalk, plaster stucco, closely packed ashes or starch, Jamin found that water was absorbed with force enough to overcome the pressure of the atmosphere from three to six times ; in other words, to sustain a column of water in a wide tube 100 to 200 ft. high. (Comptes Rendus, 50, p. 311.) Absorbent power is influenced by temperature. Warm water is absorbed by wood more quickly and abundantly than cold. In cold water starch does not swell to any striking or eyen perceptible degree, although consider- able liquid is imbibed. In hot water, however, the case is remarkably altered. The starch-grains are forcibly burst open, and a paste or jelly is formed that holds many times its weight of water. (Exp. 27, p. 51.) On freezing, the particles of water are mostly withdrawn from their adhesion to the starch. The ascent of liquids in narrow tubes whose walls are unabsorbent, is, on the contrary, diminished by a rise of temperature. Adhesive Attraction. The absorption of a liquid into the cavities of a porous body, as well as its rise in a narrow tube, are expressions of the general fact that there is an attraction between the molecules of the liquid and the solid. In its simplest manifestation this attrac- tion exhibits itself as Adhesion, and this term we shall employ to designate the kind of force under considera- tion. If a clean plate of glass be dipped in water, the liquid touches, and sticks to, the glass. On withdraw- ing the glass, a film of water comes away with it the adhesive force of water to glass being greater than the cohesive force among the water molecules. CAUSES OF THE MOTION OF JUICES. 389 Capillary Attraction. If two squares of glass be set up together upon a plate, so that they shall be in contact at their vertical edges on one side, and one- eighth of an inch apart on the other, it will be seen, on pouring a little water upon the plate, that this liquid rises in the space between them to a hight of several inches where they are in very near proximity, and curves downwards to their base where the interval is large. Capillary attraction, which thus causes liquids to rise in narrow channels or fine tubes, involves indeed the adhesion of the liquid to the walls of the tube, but also depends on a tension of the surface of the liquid, due to the fact that the molecules at the surface only attract and are only attracted by underlying molecules, so that they exert a pressure on the mass of liquid beneath them. Where the liquid adheres to the sides of a containing tube or cavity, this pressure is diminished and there the liquid rises. Adhesion may be a Cause of Continual Move- ment under certain circumstances. When a new cotton wick is dipped into oil, the motion of the oil may be fol- lowed by the eye, as it slowly ascends, until the pores are filled and motion ceases. Any cause which removes oil from the pores at the apex of the wick will disturb the equilibrium which had been established between the solid and the liquid. A burning match held to the wick, by its heat destroys the oil, molecule after mole- cule, and this process becomes permanent when the wick is lighted. As the pores at the base of the flame give up oil to the latter, they fill themselves again from the pores beneath, and the motion thus set up propagates itself to the oil in the vessel below and continues as long as the flame burns or the oil holds out. We get a further insight into the nature of this motion when we consider what happens after the oil has all been sucked up into the wick. Shortly thereafter the dimen- 390 HOW CROPS GROW. fiions of the flame are seen to dimmish. It does not, however, go out, but burns on for a time with continually decreasing vigor. When the supply of liquid in the por- ous body is insufficient to saturate the latter, there is Btill the same tendency to equalization and equilibrium. If, at last, when the flame expires, because the combus- tion of the oil falls below that rate which is needful to generate heat sufficient to decompose it, the wick be placed in contact at a single point, with another dry wick of equal mass and porosity, the oil remaining in the first will enter again into motion, will pass into the second wick, from pore to pore, until the oil has been shared nearly equally between them. In case of water contained in the cavities of a porous body, evaporation from the surface of the latter becomes remotely the cause of a continual upward motion of the liquid. The exhalation of water as vapor from the foliage of a plant thus necessitates the entrance of water as liquid at the roots, and maintains a flow of it in the sap-ducts, or causes it to pass by absorption from cell to cell. Liquid Diffusion. The movements that proceed in plants, when exhalation is out of the question, viz., such as are manifested in the stump of a vine cemented into a gauge (Fig. 43, p. 248), are not to be accounted for by capillarity or mere absorptive force under the conditions as yet noticed. To approach their elucidation we require to attend to other considerations. The particles of many different kinds of liquids attract each other. Water and alcohol may be mixed together in all proportions in virtue of their adhe-ive attraction. If we fill a vial with water to the rim and carefully lower it to the bottom of a tall jar of alcohol, we shall find after some hours that alcohol has penetrated the vial, and water has passed out into the jar, notwithstanding the latter liquid is considerably heavier than the former. CAUSES OF THE MOTION OF JUICES. 391 If the water be colored by indigo or cherry juice, its motion may be followed by the eye, and after a certain lapse of time the water and alcohol will be seen to have become uniformly mixed throughout the two vessels. This manifestation of adhesive attraction is termed Liq- uid Diffusion. What is true of two liquids likewise holds for two solutions, i. e., for two solids made liquid by the action of a solvent. A vial filled with colored brine, or syrup, and placed in a vessel of water, will discharge its con- tents into the latter, itself receiving water in return ; and this motion of the liquids will not cease until the whole is uniform in composition, i. e., until every mole- cule of salt or sugar is equally attracted by all the mole- cules of water. When several or a large number of soluble substances are placed together in water, the diffusion of each one throughout the entire liquid will go on in the same way until the mixture is homogeneous. Liquid Diffusion may be a Cause of Continual Movement whenever circumstances produce continual disturbances in the composition of a solution or in that of a mixture of liquids. If into a mixture of two liquids we introduce a solid body which is able to combine chemically with, and solidify one of the liquids, the molecule? of this liquid will begin to move toward the solid body from all points, and this motion will cease only when the solid is able to combine with no more of the one liquid, or no more remains for it to unite with. Thus, when quicklime is placed in a mixture of alcohol and water, the water is in time completely condensed in the lime, and the alcohol is rendered anhydrous. Rate of Diffusion. The rate of diffusion varies with the nature of the liquids ; if solutions, with their degree of concentration and with the temperature. 392 HOW CROPS GROW. Colloids and Crystalloids. There is a class of bodies whose molecules are singularly inactive in many respects, and have, when dissolved in water or other liquid, a very low capacity for diffusive motion. These bodies are termed Colloids,* and are characterized by swelling up or uniting with water to bulky masses (hydrates) of gelatinous consistence, by inability to crystallize, and by feeble and poorly-defined chemical affinities. Starch, dextrin, the gums, the albuminoids, pectin and pectic acid, gelatin (glue), tannin, the hydroxides of iron and aluminium and gelatinous silica, are colloids. Opposed to these, in the properties just specified, are those bodies which crystallize, such as saccharose, glucose, oxalic, citric, and tartaric acids, and the ordinary salts. Other bodies which have never been seen to crystallize have the same high diffusive rate ; hence the class is termed by Graham Crystalloids, f Colloidal bodies, when insoluble, are capable of imbib- ing liquids, and admit of liquid diffusion through their molecular interspaces. Insoluble crystalloids are, on the other hand, impenetrable to liquids in this sense. The colloids swell up more or less, often to a great bulk, from absorbing a liquid ; the volume of a crystalloid admits of no such change. In his study of the rates of diffusion of various sub- stances, dissolved in water to the extent of one per cent of the liquid, Graham found the following APPBOXIMATE TIMES OF EQUAL DIFFUSION. Hydrochloric acid, Crystalloid, 1. Sodium Chloride, " 2J. Cane Sugar, " 7. Magnesium Sulphate, " 7. Albumin, Colloid, 49. Caramel, " 98. * From two Greek words which signify glue-like. t We have already employed the word Crystalloid to distinguish the amorphous albuminoids from their modifications or combinations which present the aspect of crystals (p. 107). This use of the word was proposed by Nageli, m 1862. Graham liad employed it, as opposed to colloid, in 1861. CAUSES OF THE MOTION OF JUICES. 393 The table shows that the diffusive activity of hydro- chloric acid through water is 98 times as great as that of caramel (see p. 66, Exp. 29). In other words, a mole- cule of the acid will travel 98 times as far in a given time as the molecule of caramel. Osmose,* or Membrane Diffusion. When two miscible liquids or solutions are separated by a porous diaphragm, the phenomena of diffusion (which depend upon the mutual attraction of the molecules of the dif- ferent liquids or dissolved substances) are complicated with those of imbibition or capillarity, and of chemical affinity. The adhesive or other force which the septum is able to exert upon the liquid molecules supervenes upon the mere diffusive tendency, and the movements may suffer remarkable modifications. If we should separate pure water and a solution of common salt by a membrane upon whose substance these liquids could exert no action, the diffusion would pro- ceed to the same result as were the membrane absent. Molecules of water would penetrate the membrane on one side and molecules of salt on the other, until the liquid should become alike on both. Should the water move faster than the salt, the volume of the brine would increase, and that of the water would correspondingly diminish. Were the membrane fixed in its place, a change of level of the liquids would occur. Graham has observed that common salt actually diffuses into water, through a thin membrane of ox-bladder deprived of its. outer muscular coating, at very nearly the same rate as when no membrane is interposed. Dutrochet was the first to study the phenomena of membrane diffusion. He took a glass funnel with a long and slender neck, tied a piece of bladder over the wide opening, inverted it, poured in brine until the funnel was filled to the neck, and immersed the bladder in a * From a Greefc word meaning impulsion. 394 HOW CROPS GROW. vessel of water. He saw the liquid rise in the narrow tube and fall in the outer vessel. He designated the passage of water into the funnel as endosmose, or inward propulsion. At the same time he found the water sur- rounding the funnel to acquire the taste of salt. The outward transfer of salt was his exosmose. The more general word, Osmose, expresses hoth phenomena ; we may, however, employ Dutrochet's terms to designate the direction of osmose. Osmometer. When the apparatus employed by Dutrochet is so con- structed that the diameter of the nar- row tube has a known relation to, is, for example, exactly one-tenth that of the membrane, and the narrow tube itself is provided with a millimeter scale, we have the Osmometer of Grah- am, Fig G7. The ascent or descent of the liquid in the tube gives a measure of the amount of osmose, provided the hydrostatic pressure is counterpoised by making the level of the liquid with- in and without equal, for which pur- pose water is poured into or removed from the outer ves- sel. Graham designates the increase of volume in the osmometer as 'positive osmose, or simply osmose, and dis- tinguishes the fall of liquid in the narrow tube as nega- tive osmose. In the figure, the external vessel is intended for the reception of water. The funnel-shaped interior vessel is closed below with mem- brane, and stands upon a shelf of perforated zinc for support. The graduated tube fits the neck of the funnel by a ground joint. Action of the Membrane. When an attraction exists the membrane itself and one or more of the substances between which it is interposed, then the rate, amount, and even direction, of diffusion may be greatly changed. Fig. 67. CAUSES OF THE MOTION OF JUICES. 395 Water is imbibed by the membrane of bladder much more freely than alcohol ; on the other hand, a film of collodion (cellulose nitrate left from the evaporation of its solution in ether) is penetrated much more easily by alcohol than by water. If, now, these liquids be sepa- rated by bladder, the apparent flow will be towards the alcohol ; but if a membrane of collodion divide them, the more rapid motion will be into the water. When a vigorous chemical action is exerted upon the membrane by the liquid or the dissolved matters, osmose is greatly heightened. In experiments with a septum of porous earthenware (porcelain biscuit), Graham found that in case of neutral organic bodies, as sugar and alco- hol, or neutral salts, like the alkali-chlorides and nitrates, very little osmose is exhibited, i. e., the diffusion is not perceptibly greater than it would be in absence of the porous diaphragm. The acids, oxalic, nitric, and hydrochloric, mani- fest a sensible but still moderate osmose. Sulphuric and phosphoric acids, and salts having a decided alka- line or acid reaction, viz., acid potassium oxalate, sodi- um phosphate, and carbonates of potassium and sodium, exhibit a still more vigorous osmose. For example, a solution of one part of potassium carbonate in 1,000 parts of water gains volume rapidly, and to one part of the salt that passes into the water 500 parts of water enter the solution. In all cases where diffusion is greatly modified by a membrane, the membrane itself is strongly attacked and altered, or dissolved, by the liquids. When animal membrane is used, it constantly undergoes decomposi- tion and its osmotic action is exhaustible. In case earthenware is employed as a diaphragm, portions of its calcium and aluminium are always attacked and dis- solved by the solutions upon which it exerts osmose. Graham asserts that to induce osmose in bladder, the 396 HOW CHOPS GBOW. chemical action on the membrane must be different on the two sides, and apparently not in degree only, but also in kind, viz., an alkaline action on the albuminoid substance of the membrane on the one side, and an acid action on the other. The water appears always to accu- mulate on the alkaline or basic side of the membrane. Hence, with an alkaline salt, like potassium carbonate, in the osmometer, and water outside, the flow is inwards ; but with an acid in the osmometer, there is negative osmose, or the flow is outwards, the liquid then falling in the tube. Osmotic activity is most highly manifested in such salts as easily admit of decomposition with the setting free of a part of their acid, or alkali. Hydration of the membrane. It is remarkable that the rapid osmose of potassium carbonate and other alkali-salts is greatly interfered with by common salt, is, in fact, reduced to almost nothing by an equal quantity of this substance. In this case it is probable that the physical effect of the salt, in diminishing the power of the membrane to imbibe water (p. 393), operates in a sense inverse to, and neutralizes the chemical action of, the carbonate. In fact, the osmose of the carbonate, as well as of all other salts, acid or alkaline, may be due to their effect in modifying the hydration,* or power of the membrane, to imbibe the liquid, which is the vehicle of their motion. Graham suggests this view as an explana- tion of the osmotic influence of colloid membranes, and it is not unlikely that in case of earthenware, the chem- ical action may exert its effect indirectly, viz., by pro- ducing hydrated silicates from the burned clay, which are truly colloid and analogous to animal membranes in respect of imbibition. Graham has shown a connection between the hydrating effect of acids and alkalies OB colloid membranes and their osmotic rate. * In case water is employed as the liquid. CAUSES OF THE MOTION OF JUICES. 397 "It is well known that fibrin, albumin, and animal membrane swell much more in very dilute acids and alkalies than in pure water. On the other hand, when the proportion of acid or alkali is carried beyond a point peculiar to each substance, contraction of the colloid takes place. The colloids just named acquire the power of combining with an increased proportion of water and of forming higher gelatinous hydrates in conse- quence of contact with dilute acid or alkaline reagents. Even parchment-paper is more elongated in an alkaline solution than in pure water. When thus hydrated and dilated, the colloids present an extreme osmotic sensibility." An illustration of membrane-diffusion which is highly instructive and easy to produce, is the following : A cavity is scooped out in a carrot, as in Fig. 68, so that the sides remain inch or so thick, and a quantity of dry, crushed sugar is introduced ; after some time, the previ- ously dry sugar will be converted into a syrup by withdrawing water from the flesh of the carrot. At the same time the latter will visibly shrink from the loss of a por- tion of its liquid contents. In this case Fig. 68. foe small portions of juice moistening the cavity form a strong solution with the sugar in contact with them, into which water diffuses from the adjoining cells. Doubtless, also, sugar penetrates the parenchyma of the carrot. In the same manner, sugar, when sprinkled over thin- skinned fruits, shortly forms a syrup with the water which it thus withdraws from them, and salt packed with fresh meat runs to brine by the exosmose of the juices of the flesh. In these cases the fruit and the meat shrink as a result of the loss of water. Graham observed gum tragacanth, which is insoluble 398 HOW CROPS GROW. in water, to cause a rapid passage of water through a membrane in the same manner from its power of imbibi- tion, although here there could be no exosmose or out- ward movement. The application of these facts and principles to explain- ing the movements of the liquids of the plant is obvious. The cells and the tissues composed of cells furnish pre- cisely the conditions for the manifestation of motion by the imbibition of liquids and by simple diffusion, as well as by osmose. The disturbances needful to maintain motion are to be found in the chemical changes that accompany the processes of nutrition. The substances that normally exist in the vegetable cells are numerous, and they suffer remarkable transformations, both in chemical constitution and in physical properties. The rapidly-diffusible salts that are presented to the plant by the soil, and the equally diffusible sugar and organic acids that are generated in the leaf-cells, are, in part, converted into the sluggish, soluble colloids, soluble starch, dextrin, albumin, etc., or are deposited as solid matters in the cells or upon their walls. Thus the dif- fusible contents of the plant not only, but the mem- branes which occasion and direct osmose, are subject to perpetual alterations in their nature. More than this, the plant grows ; new cells, new membranes, new pro- portions of soluble and diffusible matters, are unceas- ingly brought into existence. Imbibition in the cell- membranes and their solid, colloid contents, Diffusion in the liquid contents of the individual cells, and Osmose between the liquids and dissolved matters and the mem- branes, or colloid contents of the cells, must unavoid- ably take place. That we cannot follow the details of these kinds of action in the plant does not invalidate the fact of their operation. The plant is so complicated and presents such a number and variety of changes in its growth, CAtTSES OF THE MOTIOH OF JUICES. 399 that we can never expect to understand all its mysteries. From what has been briefly explained, we can compre- hend some of the more striking or obvious movements that proceed in the vegetable organism. Absorption and Osmose in Germination. The absorption of water by the seed is the first step in Ger- mination. The coats of the dry seed, when put into the moist soil, imbibe this liquid which follows the cell-walls, from cell to cell, until these membranes are saturated and swollen. At the same time these membranes occa- sion or permit osmose into the cell-cavities, which, dry before, become distended with liquid. The soluble con- tents of the cells, or the soluble results of the transforma- tion of their organized matters, diffuse from cell to cell in their passage to the expanding embryo. The quantity of water imbibed by the air-dry seed commonly amounts to 50 and may exceed 100 per cent. R. Hoffmann has made observations on this subject (Vs. St., VII, p. 50). The absorption was usually complete in 48 or 72 hours, and was as follows in case of certain agricultural plants: Per cent. Per cent. Mustard 8.0 Millet 25.0 Maize 44.0 Wheat 45.5 Buckwheat 46.8 Barley 48.2 Turnip 51 .0 Rye 57.7 Oats 59.8 Hemp 60.0 Kidney Bean 96.1 Horse Bean 104.0 Pea 106.8 Clover 117.5 Beet 120.5 White Clover 126.7 Root-Action Absorption at the roots is unquestion- ably an osmotic action exercised by the membrane that bounds the young rootlets and root-hairs externally. In principle it does not differ from the absorption of water by the seed. The mode in which it occasions the sur- prising phenomena of bleeding or rapid flow of sap from a wound on the trunk or larger roots is doubtless essen- tially as Hofmeister first elucidated by experiment. This flow proceeds in the ducts and wood-cells. Between these and the soil intervenes loose cell-tissue 400 HOW CEOPS GROW. surrounded by a compacter epidermis. Osmose takes place in the epidermis with such energy as not only to distend to its utmost the cell-tissue, but to cause the water of the cells to filter through their walls, and thus gain access to the ducts. The latter are formed in young cambial tissue, and, when new, are very delicate in their walls. Fig. 69 represents a simple apparatus by Sachs for imitating the supposed mechanism and process of Eoot- action. In the Fig., g g represents a short, wide, open A glass tube ; at a, the tube is tied over and se- curely closed by a piece of pig's bladder ; it is then filled with solution of sugar, and the other end, b, is closed in similar manner by a piece of parch- ment-paper (p. 59). Finally a cap of India-rub- ber, K, into whose neck a narrow, bent glass tube, r, is fixed, is tied on over b. (These join- ings must be made very carefully and firmly.) The space within r K is left empty of liquid, and r the combination is placed in a vessel of water, as in the figure. C represents a root-cell whose exterior wall (cuticle), a, is less penetrable under pressure than its interior, b; r corres- ponds to a duct of vas- cular tissue, and the surrounding water takes the place of that Fig. 69. existing in the pores of the soil. The water shortly penetrates the cell, C, dis- tends the previously flabby membranes, under the accu- mulating tension filters through b into r, and rises in the tube ; where in Sachs's experiment it attained a height of 4 or 5 inches in 24 to 48 hours, the tube, r, being about 5 millimeters wide and the area of J, 700 sq. CAUSES OP THE MOTION OP JUICES. 401 mm. When we consider the vast root-surface exposed to the soil, in case of a vine, and that myriads of root- lets and root-hairs unite their action in the compara- tively narrow stem, we must admit that the apparatus above figured gives us a very satisfactory glance into the causes of bleeding. Motion of Nutritive or Dissolved Matters; Se- lective Power of the Plant. The motion of the sub- stances that enter the plant from the soil in a state of solution, and of those organized within the plant is, to a great degree, separate from and independent of that which the water itself takes. At the same time that water is passing upwards through the plant to make good the waste by evaporation from the foliage, sugar or other carbhydrate generated in the leaves is diffusing against the water, and finding its way down to the very root-tips. This diffusion takes place mostly i i the cell- tissue, and is undoubtedly greatly aided by osmose, i. e., by the action of the membranes themselves. The very thickening of the cell- walls by the deposition of cellulose would indicate an attraction for the material from which cellulose is organized. The same transfer goes on sim- ultaneously in all directions, not only into roots and stem, but into the new buds, into flowers and fruit. We have considered the tendency to equalization between two masses of liquid separated from each other by pen- etrable membranes. This tendency makes valid for the organism of the plant the law that demand creates sup- ply. In two contiguous cells, one of which contains solution of sugar, and the other solution of potassium nitrate, these substances must diffuse until they are mingled equally, unless, indeed, the membranes or some other substance present exerts an opposing and prepon- derating attraction. In the simplest phases of diffusion each substance is, to a certain degree, independent of every other. Any 402 HOW CEOPS GEOW. salt dissolved in the water of the soil must diffuse into the root-cells of a plant, if it be absent from the sap of this root-cell and the membrane permit its passage. "When the root-cell has acquired a certain proportion of the salt, a proportion equal to that in the soil-water, more cannot enter it. So soon as a molecule of the salt has gone on into another cell or been removed from the sap by any chemical transformation, then a molecule may and must enter from without. Silica is much more abundant in grasses and cereals than in leguminous plants. In the former it exists to the extent of about 25 parts in 1,000 of the air-dry foli- age, while the leaves and stems of the latter contain but 3 parts. When these crops grow side by side, their roots are equally bathed by the same soil- water. Silica enters both alike, and, so far as regards itself, brings the cell-contents to the same state of saturation that exists in the soil. The cereals are able to dispose of silica by giving it a place in the cuticular cells ; the leguminous crops, on the other hand, cannot remove it from their juices ; the latter remain saturated, and thus further diffusion of silica from without becomes impos- sible except as room is made by new growth. It is in this way that we have a rational and adequate explana- tion of the selective power of the plant, as manifested in its deportment towards the medium that invests its roots. The same principles govern the transfer of mat- ters from cell to cell, or from organ to organ, within the plant. Wherever there is unlike composition of two miscible juices, diffusion is thereby set up, and proceeds as long as the cause of disturbance lasts, provided im- penetrable membranes do not intervene. The rapid movement of water goes on because there is great loss of this liquid ; the slow motion of silica is a consequence of the little use that arises for it in the plant. Strong chemical affinities may be overcome by help of CAUSES Of ffiE MOflOtf OF JUICES. 403 osmose. Graham long ago observed the decomposition of alum (sulphate of aluminium and potassium) by mere diffusion ; its potassium sulphate having a higher diffu- sive rate than its aluminium sulphate. In the same manner acid potassium sulphate, put in contact with water, separates into neutral potassium sulphate and Zree sulphuric acid.* We have seen (pp. 170-1) that the plant, when veg- etating in solutions of salts, is able to decompose them. It separates the components of potassium nitrate appro- priating the acid and leaving the base to accumulate in the liquid. It resolves chloride of ammonium, taking up ammonia and rejecting the hydrochloric acid. The action in these cases we cannot definitely explain, but our analogies leave no doubt as to the general nature of the agencies that cooperate to such results. The albuminoids in their usual form are colloid bodies, and very slow of diffusion through liquids. They pass a collodion membrane somewhat (Schu- macher), but can scarcely penetrate parchment-paper (Graham). In the plant they are found chiefly in the sieve-cells and adjoining parts of the cambium. Since for their production they must ordinarily require the concourse of a carbhydrate and a nitrate, they are not unlikely generated in the cambium itself, for here the descending carbhydrates from the foliage come in con- tact with the nitrates as they rise from the soil. On the yfcher hand, the albuminoids become more diffusible in gome of their combinations. Schumacher asserts that carbonates and phosphates of the alkalies considerably increase the osmose of albumin through collodion mem- branes (PhysiJc der Pflanzen, p. 128). It is probable that those combinations or modifications of the albuminoids *Tlie decomposition of these salts is begun by the water in which they are dissolved, and is carried on by osmose, because the latter secures separation of the reacting substances. 404 fiow CROPS GftOW. which occur in the soluble crystalloids of aleurone (p. 105) and haemoglobin (p. 97) are highly diffusible, as certainly is the case with the peptones. Gaseous bodies, especially the carbonic acid and oxy- gen of the atmosphere, which have free access to the intercellular cavities of the foliage, and which are for the most part the only contents of the larger ducts, may be distributed throughout the plant by osmose after having been dissolved in the sap or otherwise absorbed by the cell-contents. Influence of the Membranes. The sharp separa- tion of unlike juices and soluble matters in the plant indicates the existence of a remarkable variety and range of adhesive attractions. In orange-colored flowers we see upon microscopic examination that this tint is pro- duced by the united effect of yellow and red pigments which are contained in the cells of the petals. One cell is filled with yellow pigment, and the adjoining one with red, but these two colors are never contained in the same cell. In fruits we have coloring matters of great tinctorial power and freely soluble in water, but they never forsake the cells where they appear, never wander into the contiguous parts of the plant. In the stems and leaves of the dandelion, lettuce, and many other plants, a white, milky, and bitter juice is contained, but it is strictly confined to certain special channels and never visibly passes beyond them. The loosely disposed cells of the interior of leaves contain grains of chloro- phyl, but this substance does not appear in the epidermal cells, those of the stomata excepted. Sachs found that solution of indigo quickly entered the roots of a seedling bean, but required a considerable time to penetrate the stem. Hallier, in his experiments on the absorption of colored liquids by plants, noticed, in all cases when leaves or green stems were immersed in solution of indigo, or black-cherry juice, that these dyes readily passed into CAUSES OP THE MOTION OF JUICES. 405 and colored the epidermis, the vascular and cambial tis- sue, and the parenchyma of the leaf-veins, keeping strictly to the cell-walls, but in no instance communi- cated any color to the cells containing chlorophyl. (Phytopathologie, Leipzig, 1868, p. 67.) We must infer that the coloring matters either cannot penetrate the cells that are occupied with chlorophyl, or else are chem- ically transformed into colorless substances on entering them. Sachs has shown in numerous instances that the juices of the sieve-cells and cambial tissue are alkaline, while those of the adjoining cell-tissue are acid when examined by test-paper. (Exp. Phys. der Pflanzen, p. 394.) When young and active cells are moistened with solu- tion of iodine, this. substance penetrates the cellulose without producing visible change, but when it acts upon the protoplasm, the latter separates from the outer cell- wall and collapses towards the center of the cavity, as if its contents passed out, without a corresponding endos- mose being possible (p. 224). We may conclude from these facts that the membranes of the cells are capable of effecting and maintaining the separation of substances which have considerable attrac- tions for each other, and obviously accomplish this result by exerting their superior attractive or repulsive force. The influence of the membrane must vary in character with those alterations in its chemical and structural con- stitution which result from growth or any other cause. It is thus, in part, that the assimilation of external food by the plant is directed, now more to one class of proximate ingredients, as the carbhydrates, and now to another, as the albuminoids, although the supplies of food presented are uniform both in total and relative quantity. If a slice of red-beet be washed and put into water, the pigment which gives it color does not readily dissolve 406 HOW CHOPS GfitOTft and diffuse out of the cells, but the water remains coloi, less for several days. The pigment is, however, soluble in water, as is seen at once by crushing the beet, where- by the cells are forcibly broken open and their contents displaced. The cell-membranes of the uninjured root are thus apparently able to withstand the solvent power of water upon the pigment and to restrain the latter from diffusive motion. Upon subjecting the slice of beet to cold until it is thoroughly frozen, and then plac- ing it in warm water so that it quickly thaws, the latter is immediately and deeply tinged with red. The sudden thawing of the water within the pores of the cell-mem- brane has in fact so altered them, that they can no longer prevent the diffusive tendency of the pigment. (Sachs.) MECHANICAL EFFECTS OF OSMOSE OK THE PLANT. The osmose of water from without into the cells of the plant, whether occurring on the root-surface, in the buds, or at any intermediate point where chemical changes are going on, cannot fail to exercise a great me- chanical influence on the phenomena of growth. Boot- action, for example, being, as we have seen, often suffi- cient to overcome a considerable hydrostatic pressure, might naturally be expected to accelerate the develop- ment of buds and young foliage, especially since, as com- mon observation shows, it operates in perennial plants, as the maple and grape-vine, most energetically at the season when the issue of foliage takes place. Experi- ment demonstrates this to be the fact. If a twig be cut from a tree in winter and be placed in a room having a summer temperature, the buds, before dor- MECHANICAL EFFECT OF OSMOSE ON PLAKTS. 407 mant, shortly exhibit signs of growth, and if the cut end be immersed in wa- ter, the buds will enlarge quite after the normal manner, as long as the nu- trient matters of the twig last, or until the tissues at the cut begin to decay. It is the summer temperature which excites the chemical changes that re- sult in growth. Water is needful to occupy the expanding and new-form- ing cells, and to be the vehicle for the translocation of nutrient matters from the wood to the buds. Water enters the cut stem by imbibition or capillar- ity, not merely enough to replace loss by exhalation, but is also sucked in by osmose acting in the growing cells. Under the same conditions as to tem- perature, the twigs which are connected with active roots expand earlier and more rapidly than cuttings. Artificial pressure on the water which is pre- sented to the latter acts with an effect similar to that which the natural stress caused by the root-power exerts. This fact was demonstrated by Boehm (Sitzungsberichte der Wiener ATcad., 1863), in an experiment which may be made as illustrated by the cut, Fig. 70. A twig with buds is secured by means of a perforated cork into one end of a short, wide glass tube, which is closed below by another cork through which passes a narrow syphon-tube, B. The cut end of the twig is immersed in water, W, which is put under pressure by pouring mercury into the upper 408 HOW CEOPS GBOW. extremity of the syphon-tube. Horse-chestnut and grape twigs cut in February and March and thus treated the pressure of mercury being equal to six to eight inches above the level, M after four to six weeks, unfolded their buds with normal vigor, while twigs similarly cir- cumstanced but without pressure opened four to eight days later and with less appearance of strength. Fr. Schulz (Karsten's Bot. Unters., Berlin, II, 143) found that cuttings of twigs in the leaf, from the horse- chestnut, locust, willow and rose, subjected to hydro- static pressure in the same way, remained longer turges- cent and advanced much further in development of leaves and flowers than twigs simply immersed in water. The amount of water in the soil influences both the absolute and relative quantity of this ingredient in the plant. It is a common observation that rainy spring weather causes a rank growth of grass and straw, while the yield of hay and grain is not correspondingly in- creased. The root-action must operate with greater effect, other things being equal, in a nearly saturated soil than in one which is less moist, and the young cells of a plant situated in the former must be subjected to greater internal stress than those of one growing in the latter must, as a consequence, attain greater dimen- sions. It is not uncommon to find fleshy roots, espec- ially radishes which have grown in hot-beds, split apart lengthwise, and Hallier mentions the fact of a sound root of petersilia splitting open after immersion in water for two or three days. (Phytopathologie, p. 87.) This mechanical effect is indeed commonly conjoined with others resulting from abundant nutrition, but increased bulk of a plant without corresponding increase of dry matter is doubtless in great part the consequence of large supplies of water to the roots and its vigorous osmose into the expanding plant. APPENDIX. COMPOSITION OF VARIOUS AGRICULTURAL PRODUCTS giving the Aver- age quantities of Water, Nitrogen, Ash, and Ash-ingredients in 1,000 parts of fresh or air-dry substances. According to Prof. E. von WOLFF, 1880. Water. Nitrogen. SO ! Potash. OS t! do OJ 3 Magnesia. Phosphor- ic Acid. Sulphuric Acid. Silica. Chlorine. GRASSES. Rich pasture grass, Young grass and after- math, 782 800 700 700 700 8GO 820 800 740 820 S05 <8() 850 870 )20 815 >: 71)3 7(57 81)0 -iOO 750 8no 100 Mil 5< ; 140 )33 HI3 888 143 140 144 HO 143 143 143 144 145 143 7.2 5.6 5.7 5.4 6.0 5.3 4.8 7.2 5.3 5.6 1.8 2.2 2.1 1.8 1.6 1.9 5.4 4.3 2.7 3.2 3.4 2.4 3.0 4.0 1.6 3.2 4.9 4.7 17.6 20.3 16.0 20.5 16.0 20.8 16.0 17.6 21.1 18.1 17.8 20.4 20.5 14.0 14.7 13.7 19.2 8.6 14.3 9.1 8.2 7.5 6.4 7.1 4.9 10.0 19.7 7.4 9.8 9.5 15.6 9.6 8.0 5.8 8.1 5.0 16.0 10.0 26.7 29.5 12.4 16.0 18.3 22.3 18.0 16.8 17.0 17.9 8.1 5.3 5.9 7.1 7.1 5.1 5.5 4.4 4.5 2.4 3.1 4.8 3.0 3.5 2.9 3.8 1.6 5.4 7.7 2.5 4.7 5.8 5.8 4.3 3.6 2.4 3.7 1.2. 2.7 5.1 4.8 3.3 3.7 3.3 5.6 4.7 6.2 5.2 2.8 5.8 0.3 0.7 0.8 0.7 0.4 0.3 0.3 0.3 0.3 0.3 1.0 1.5 1.7 0.4 0.6 0.6 1.0 0.2 0.4 0.2 1.0 0.3 1.5 0.8 0.5 0.6 0.8 0.9 5.7 0.2 0.4 0.4 0.1 0.5 0.3 0.5 0.3 0.3 0.7 0.3 2.6 2.5 1.1 1.5 1.7 3.9 4.5 4.8 8.5 2.9 4.3 0.3 0.9 0.9 0.7 0.4 0.7 1.1 2.0 1.6 0.3 0.3 2.8 1.2 0.5 0.4 0.5 0.6 1.9 0.1 1.0 0.2 0.3 0.2 0.5 0.6 0.5 0.1 0.5 1.2 1.2 0.5 0.4 0.7 1.3 1.6 1.5 0.9 1.1 1.4 0.4 0.4 0.3 0.2' 0.6 0.2 0.6 0.4 0.3 0.3 0.5 0.6 0.4 0.3 0.2 0.2 0.2 1.0 0.3 1.9 2.8 1.9 2.4 2.2 2.0 2.2 2.0 2.1 2.0 1.9 1.4 1.3 2.2 2.4 1.7 1.5 1.3 1.6 0.9 1.8 0.8 1.1 1.1 0.8 0.9 0.5 1.9 2.0 1.3 1.4 1.6 1.4 1.1 1.6 1.2 0.7 0.9 1.6 3.4 6.8 6.5 5.7 8.1 9.0 7.8 9.2 7.9 5.6 8.5 0.7 1.0 0.5 0.8 0.6 0.3 0.4 0.4 1.1 0.4 1.1 0.3 0.5 0.7 0.7 0.3 0.3 0.5 4.9 0.4 0.6 0.6 2.4 1.3 1.0 0.4 0.3 0.3 1.1 0.4 0.5 0.1 0.1 0.2 0.4 0.1 0.5 0.2 4.1 4.6 5.9 6.5 6.6 0.4 0.4 0.4 1.8 0.3 0.6 0.2 0.2 0.1 0.1 0.2 0.2 1.5 0.7 0.2 0.2 0.1 0.1 0.3 0.5 1.3 05 0.7 0.1 10.5 15.6 0.3 1.2 0.3 5.8 0.2 0.3 4.9 0,3 1 2.1 1.1 1.3 2.1 1.1 0.6 0.5 0.5 0.6 0.5 0.6 0.9 0.4 0.5 0.3 0.3 0.5 0.4 0.3 0.2 0.4 0.3 1.3 0.5 0.3 0.4 0.4 0.3 1.0 0.1 0.3 0.1 0.2 0.1 0.2 0.1 0,1 Orchard grass, Rye grass, Timothy, CLOVERS AND LEGUMES. Red clover, young, Red clover in bud, Red clover in flower, . . . Lucern or Alfalfa, in early bloom, Alsike clover, White clover in flower, ROOTS, TUBERS, BULBS. Beets, Carrots, Rutabagas, Turnips, Sugar-beets, Radish, Parsnip, Horseradish, Onion Artichoke, Helianthus, . Potato, "VEGETABLES." Cabbage, loose outer leaves, Cabbage, heart, Cauliflower, heart, Cucumber, fruit, Lettuce, Asparagus, sprouts, Spinage, Mushrooms, edible, SEEDS OF CEREALS. Oats, Millet, Maize, Sorghum, Spring Wheat, Spring Barley, Spring Rve, Winter Wheat, Winter Barley, Winter live, 409 410 HOW CROPS GKOTV. COMPOSITION OF VARIOUS AGRICULTURAL PRODUCTS. [Continued.] Water. Nitrogen. en ^ Potash. A - 5 00 Lime. Magnesia. Phosphor- Acid. c d P O3 Silica. Chlorine. 1 SEEDS OF LEGUMES AND CLOVERS. Horse bean, Vicia, Garden bean, Phaseolus, 145 150 100 143 150 150 77 122 us i:;o K\\ S31 SL>5 s;is 830 150 150 160 150 14.'! 167 165 160 15(1 165 160 160 143 143 150 143 143 143 160 160 143 113 143 140 ISO ISO 120 10S 140 112 I'".' 40.8 39.0 53.4 35.8 30.5 36.5 26.1 32.8 0.6 0.6 1.7 18.5 25.5 19.1 16.3 35.5 24.5 19.7 12.5 23.2 24.0 23.0 5.6 6.4 4.8 5.6 4.8 4.0 13.0 10.4 6.4 5.8 7.2 2.3 34.8 24.6 25.0 62.1 47.2 31.0 27.4 28.3 23.4 38.3 33.8 33.8 46.3 32.6 36.5 2.2 3.3 3.9 2.9 8.8 29.7 82.4 76.0 59.4 58.2 82.3 68.4 57.6 44.7 61.1 40.0 62.0 61.6 45.9 45.3 38.1 46.0 38.2 51.7 43.1 71.2 82.7 92.0 4.5 140.7 64.7 31.1 31.7 72.9 66.4 51.3 12.9 12.1 12.6 10.1 13.5 12.3 10.9 9.4 10.0 5.9 0.8 1.8 2.0 1.7 5.0 7.7 31.6 22.3 19.3 20.2 29.7 25.3 18.6 10.0 13.1 11.1 14.6 16.3 10.7 16.4 11.0 6.3 8.6 24.2 9.9 4.5 5.2 8.4 2.3 40.9 2H.2 9.7 5.5 17.9 15.8 12.5 0.3 0.1 0.3 0.2 0.4 0.2 2.3 0.4 0.7 2.0 0.6 0.3 0.1 0.1 0.4 1.3 3.0 1.0 2.0 1.9 1.4 1.1 1.4 4,1 1.1' 1.1 2.0 1.6 0.5 1.0 0.6 0.7 1.1 1.8 2.9 0.3 1.7 0.1 4.5 6.6 2.5 0.6 1.9 o.s 1.5 1.5 1.7 1.1 2.5 2.5 1.9 10.9 2.6 7.0 0.1 0.3 0.3 0.3 1.0 7.1 10.1 10.4 3.4 4.3 23.5 20.7 20.1 15.8 18.4 13.6 25.2 4.3 3.3 4.9 2.6 2.7 3.1 9.5 15.9 4.0 3.5 1.7 0.2 50.7 12.4 6.9 16.8 19.7 2.9 4.3 2.2 2.1 2.5 1.9 4.9 3.9 5.6 2.6 4.7 3.7 0.2 0.2 0.2 0.2 0.4 2.4 4.6 5.1 1.7 1.3 7.6 6.3 6.9 5.8 5.0 3.1 ?:i 2.6 0.9 1.1 1.2 1.9 3.5 1.5 1.1 1.2 0.2 10.4 0.5 2.0 2.1 7.0 10.1 8.1 12.1 9.7 10.4 8.4 14.5 11.6 10.5 16.9 13.5 14.6 0.3 0.5 0.6 0.4 1.4 2.7 7.4 5.9 5.6 6.2 10.0 6.9 5.6 4.4 7.8 4.1 5.3 2.8 1.9 3.8 2.0 2.2 2.5 6.1 3.5 1.3 5.6 4.0 0.2 6.6 9.2 4.2 2.1 5.8 30.5 16.2 1.1 1.1 0.8 0.8 0.9 1.6 0.7 0.1 0.8 1.8 0.1 0.2 0.2 0.1 0.5 1.4 2.7 4.1 1.5 2.3 1.8 1.7 1.9 1.4 4.5 1.6 3.6 2.0 1.8 2.4 1.2 1.1 1.6 2.7 2.7 3.5 0.1 e.i 8.5 2.2 2.0 0.6 2.9 0.8 1.7 0.2 0.2 0.2 0.5 0.8 0.1 5.5 0.4 0.9 0.1 0.1 0.4 0.1 0.3 7.2 15.9 19.4 24.7 18.5 2.5 1.8 1.6 3.0 2.7 1.6 5.9 28.8 23.4 13.1 18.2 31.0 18.8 2.9 2.9 50.4 66.4 74.7 1.3 8.1 1.6 1.7 3.1 13.3 5.5 6.4 0.5 0.3 0.1 0.4 0.5 0.5 0.5 0.2 0.1 0.1 0.7 8.4 4.5 2.3 6.1 3.3 2.4 2.2 1.3 2.6 2.2 1.9 2.7 1.5 0.6 0.8 0.8 0.8 4.1 2.3 0.8 0.4 0.2 9.4 2.4 1.3 0.6 3.7 0.4 Pea Red Clover, White Clover OIL SEEDS. Cotton Flax FRUITS. Apple, entire fruit, Pear, entire fruit, Cherry, entire fruit, Plum entire fruit, Grape, entire fruit, HAY. Alpine hay, From very young grass, From young grass and aftermath, From cereals cut in English rye grass, Red Clover, young, .... Red Clover in bud,.. .. Red Clover in flower .. Red Clover, ripe, White Clover in flower, Alsike Clover, Lucern (Alfalfa) early STRAW. Oat \ Barley, Maize, Spring Wheat, Winter Wheat, Winter Rye, Buckwheat, Pea, CHAFF, ETC. Oat Chaff, Rye Chaff, Wheat Chaff MISCELLANEOUS. Tobacco leaves, Tobacco stems, Flax stalks, Hops, entire plant, INDEX. Absorption by the root, 260, 269, 272 Access of air to Interior of Plant, 313 Aestic Acid 76 Acetamide, 115 Acids, Definition of ..... 81 Acids, Test for 82 Acid elements 127 Acid-proteids, 99 Adhesion, 9,388 Agriculture, Art of 1 Agricultural products, Compo- sition'in 1,000 parts, ... 409 Agricultural Science, Scope of . 7 Air-passages in plant, .... 313 Air-roots, 273 Akene, 331 Albumin, 89 Albuminates, 99 Albuminoids, Characters and composition, ... 87, 104, 106 Albuminoids in animal nutrit- ion, 108 Albuminoids, Diffusion of . . .403 Albuminoids in oat-plant, . . 234 Albuminoids, Mutual relations of 107 Albuminoids, Proportion of, in vegetable products, . . . 114 Albumose 101 Alburnum, 305 Aleurone, 110 Alkali-earths 81, 139 Alkali-earths, Metals of . . .139 Alkali-metals 138 Alkalies, 81,138 Alkali-proteids, 99 Alkaloids, 120 Allylsulphocyanate, 129 Alumina, 143 Aluminium, 143 Aluminium phosphate 28 Amides, 114,118 Amido-acids, 114, 118 Amidoacetic acid, 115 Amidocaproic acid, 116 Amid* (valeric acid, .... .116 Amidulin 52 Amines, .119 Ammonium Carbonate, ... 33 Ammonium Salts In plant, 82, 113 A my Luii,. ..'...,,, 62 411 Amyloid, 43 Amylodextrin, 63 Amyloses, 39, 40 Anhydrous phosphoric acid, . 132 Anhydrous sulphuric acid, . .130 Anther, 318 Apatite, 148 Arabic acid, 58 Arabin, 58 Arabinose, 65 Arrow root, 48 Arsenic in plants, . . . 137, 210 Ash-ingredients, .... 126, 161 Ash-ingredients, Excess of . .201 Ash-ingredients, Excess of, how disposed of 203 Ash-ingredients, Function of in plant, 210 Ash-ingredients, State of, in plant, 207 Ash of plants ' 13, 126 Ash of plants, Analyses, Tables of 164 Ash of plants, Composition of, normal, 177 Ash of plants, Composition of, variations in 151 Ash, Proportions of, Tables, . .152 Asparagin, 116 Assimilation, 364 Atmosphere, Offices of . . . .367 Atoms, ..30 Atomic weight, 31 Avenin 120 Bark, 291, 207 Barium in plants, 210 Bases, Definition of 81 Bast-cells, Bast-tissue, 293, 295, 297 Bean, Leaf, Section of ... .308 Bean, Seed 334 Berry, 331 Betaln 116 Biology, 10 Bleeding of vine, .... 271,371 Blood-fibrin, 91 Bone-black, 15 Boron, Boric acid, 210 Buds, Structure of 283 Buds, Development under pres- sure, 406 Bulbs, .289 Butyric acid, ........ 70 412 CROPS GROW. Caesium, Action on oat, . . .209 Caffein, 117 Calcium, 139, 214 Calcium, carbonate, 145 Calcium, hydroxide, .... 143 Calcium, oxide, 139 Calcium, phosphate, . . .28, 148 Calcium, sulphate 146 Callous, 382 Calyx 317 Cambium, 294, 295, 299 Cane-sugar, 65 Capillary attraction, .... 389 Carbamide, 115 Carbhydrates, 39 Carbhydrates, Composition . . 72 Carbhydrates, Transformations of . 70 Carbon, Properties of .... 14 Carbon in ash, 128 Carbon dioxide, 128 Carbonates, 128, 144 Carbonate of lime, 145 Carbonate of potash, 144 Carbonate of soda, 144 Carbonic acid, 19, 128 Carbonic acid as food of plant, 328 Carbonic acid in ash-analyses, 149 Carboxyl, 75, 77 Casein, 84 Caseose 101 Cassava, 51 Causes of motion of juices, . .385 Cell-contents, 249 Cell-multiplication, 252 Cell, Structure of . . . . . .245 Cells, Forms of 247 Cellular plants, 243 Cellular tissue, 255 Cellulose, 40 Cellulose, Composition .... 44 Cellulose, Estimation .... 45 Cellulose nitrates, 43 Cullulose sulphates, 43 Cellulose, Test for 44 Cellulose, Quantity of, in plants, 46 Chemical affinity, 29 Chemical affinity overcome by osmose, 403 Chemical combination, ... 29 Chemical decomposition, ... 30 Chemistry, 10 Chlorides 133, 149 Chloride of ammonium, decom- posed by plant 184 Chlorine, 132 Chlorine essential to crops ? . .194 Chlorine, function in plant, . 218 Chlorine in strand plants, . .191 Chlorophyl, 124, 307, 308 Chlorophyl requires iron, . . 220 Chlorophyllan, 125 Choline, 119 Circulation of sap, 369 Citric acid, 80 Citrates, 80, 149 Classes of plants, 329 Classification botanical, . . .329 Clover, washed by rain, . . . 204 Colloids, 392 Con-''utin, 95,97 Combustion, 18 Composite plants, 330 Concentration of plant-food, .185 Concretions in plant, .... 205 Coniferous plants, 330 Copper in plants, ...... 210 Cork, 298 Corm, . 288 Corolla 317 Cotyledon, .290, 333 Coniferous plants, ..... .330 Cryptogams, 315, 329 Crystalloid aleurone, . . . .111 Crystalloids, 392 Crystals in plant, 206 Culms, 284 Cyanides, 127, 129 Cyanogen, 129 Definite proportions, Law of . .30 Density of seeds, 339 Depth of sowing, ...... .355 Dextrin, 53 Dextrose, 63 Diastase, ...... 67, 103, 360 Diffusion of liquids, 390 Dioecious plants, 318 Drains stopped by roots, . . .276 Drupe, 331 Dry weather, Effect of, on plants 157 Ducts, 255,294 Dulcite, 74 Dundonald's treatise on Agri- cultural Chemistry, ... 4 Elements of Matter, 8 Embryo, 333 Endogens, 259, 290, 334 Endosmose, 394 Endosperm, 332 Enzymes, 103 Epidermis, ........ .291 Epidermis of leaf, 308 Eremacausis, . 20 Excretions from roots, .... 280 Exhalation of water from foli- age, 309 Exogens, .... 239, 293, 296, 334 Exosmose, 394 Exudation of ash-ingredients, 203 Eyes of potato, . 28 Families, 328 Fatty acids, 75 Fats, 83 Fats converted into starch, . . 358 Fat in oat crop, 230 Fat in Vegetable Products, . . 87 Ferments, ........ .102 Ferric oxide, ........ 142 Ferric hydroxide, 142 Ferric salts, 142 Ferrous oxide, ...... .141 Ferrous hydroxide, ..... 141 Ferrous salts, ....... .142 Fertilization, .319 Fibrin, .,,.,.,. .91,9* INDEX. 413 Flbrinogen, . 91, 96 Flax fiber, Fig., .... 'L., 41, 248 Flax seed mucilage, . . . 58, 62 Flesh fibrin, 92 Flower, 317 Flow of sap, 371 Fluorine in plants, 209 Foliage, Offices of 314 Food of Plant, 366 Formative layer, 245 Formulas, Chemical, . . . 33, 73 Fructification, 319 Fructose, 63 Fruit, 330 Galactin, 61 Galactose, 65 Gases, how distributed through- out the plant, 404 Gelatinous Silica, 136 Genus ; Genera, 328 Germ, 333 Germination, 349 Germination, Conditions of . . 351 Germination, Chemical Physi- ology of 357 Girdling, 383 Glauber's Salt, 146 Gliadin, 92 Globulin, 96 Glucoses, 39, 63 Glucosides, 69 Glutamin 116 Gluten, 92 Gluten-Casein, 93, 95 Glycerin, 86 Glycogen 56 Glyco^oll, 116 Glycollic acid, 77 Gourd fruits 331 Grains, 331 Grape Sugar, 63 Growth, 252 Growtli of roots, 256 Gum, Amount of, in plants, . . 62 Gum Arabic, 57 Gum Tragacanth, 57 Gun Cotton 43 Gypsum 147 Haemetin, 110 Haemoglobin, 109 Hallett's pedigree wheat, .158, 344 Hybrid, Hybrfdizing, 324 Hydration of membranes, . . 396 Hydrochloric acid, .... 23, 133 Hydrocyanic acid, 129 Hydrogen, 22, 112 Hydrogen chloride, 23 Hydrogen sulphide, ... 26, 129 Imbibition 386 Imides, 117 Inorganic matter, 12 Internodes, 284 Inniiii. 55 Invertin, 103 Iodine in plants, .... 134, 210 Iodine, Solution of 44 Iron 141,192 Iron, Function pf . , , . . .2.J9 Isomerism, 73 Juices of the Plant, 369 Lactic Acid, 77 Lactose, 68 Latent buds, 285 Latex, 304 Layers, 286 Lead in plants, 210 Leaf pores 309 Leaves, Structure of ... 306, 308 Leaves, office in nutrition, . . 328 Lecithin, 122 Legume, 332 Legumin, . .* 95 Leguminous plants, 332 Leucin, 116 Levulin, 56 Levulose, 63 Lignin, 41 Lime, 139 Liquid Diffusion, 390 Lithia, Lithium, in plants, . .209 Lupanin, Lupinin, Lupinidin, 120 Magnesia, 140 Magnesium, 140, 215 Magnesium hydroxide 141 Magnesium oxide, 140 Maize fibrin, 93 Malates, 149 Malic acid, 79 Malonic acid, 79 Malt, Chemistry of 358 Maltose, 67 Manganese, 142, 193 Mannite, 74 Mannose, . 65 Margarin, 85 Medullary rays, 299 Membrane-diffusion, . . 393, 397 Membranes, Influence on mo- tion of juices, 404 Metals, Metallic elements, . .138 Metapectic acid, 59 Metarabin, 59 Milk ducts, 304 Miik Sugar 68 Molecules, Molecular Weights, 32 Monaecious plants, 319 Motion caused by adhesion, . .389 Mucedin, 92, 321 Multiple Proportions, .... 32 Muriate of potash, 149 Muriatic acid, 133 Myosin, 97, 98 Nectar, Nectaries 319 Neurin, 120 Nicotin, ". .120 Niter, Nitrate of potassium, . . 149 Nitrates in plants, .... 113, 149 Nitric Acid in plant, 113 Nitrogen, Properties of . . . .20 Nitrogen in ash, 127 Nodes, 284 Non-metals, 127 Notation, Chemical . . ..... .33 Nuclein, 122 Nucleus 300 Nut, , , . . t . ,331 414 HOW CROPS GROW. Nutrient matters In plant, Mo- tion of 401 Nutrition of seedling 357 Nutrition of plant, 366 Oat plant, Composition and growth of 223 Oats, weight per bushel, . . .176 Oil in seeds, etc., 83 Oil of vitriol, 26, 130 Oils, Properties of 83 Oleic acid 86 Olein, 85 Orders, 328 Organic matter, 12 Organism, Organs 243 Osmose, 393 Osmose, mechanical effects on plant, 406 Osmometer, 394 Ovaries 318 Ovules, 318 Oxalates 78, 149 Oxalic acid, 78 Oxides, 19, 20 Oxides of iron, described, . 19, 141 Oxides of manganese, described 142 Oxyfatty acids, 77 Oxygen, Properties of .... 16 Oxygen occurrence in ash, . .128 Oxygen in Assimilation, . . . 364 Oxygen in Germination, . . .353 Palmitic acid, 86 Palmitin, 85 Papain 104 Parenchyma, 255 Papilionaceous plants, . . . 330 Pappus, 331 Pararabin, 59 Paraglobulin, 96, 99 Paragalactin, 61 Pectic acid, 74 Pectin bodies, 58, 59, 74 Pectosic acid, 74 Pectose, 58, 61, 74 Pedigree wheat, 158, 344 Pepsin, 104 Peptones 100 Permeability of cells, .... 253 Petals, 318 Phanerogams, Phaenogams,316, 329 Phloridzin, 69 Phosphate of lime, 148 Phosphate of soda, 148 Phosphate of potash, .... 147 Phosphates, 28, 132, 147 Phosphates function in plants, 211 Phosphates relation to albu- minoids, 221 Phosphoric acid, 27, 132 Phosphorite, 148 Phosphorized substances, . . 122 Phosphorus, 27 Phosphorus pentoxide, . . 27, 132 Physics, 10 Physiology, 10 Piperin, 121 Pistils 318 nt u, ,.,,,,,,.. .aw: Pith rays, 299 Plastic Elements of Nutrition, 109 Plumule, 333 Pollarding, 286 Pollen, 318 Polygonum convolvulus, Fertil- ization of, Fig., 295 Pome, 331 Porosity of vegetable tissues, .385 Potato leaf, Pores of, Fig., . . 309 Potato stem, Section of, Fig., .304 Potato tuber, Structure and Sec- tion of, Fig., 300 Potash, 138, 144 Potash lye 139 Potassium, 138,211 Potassium carbonate, . . . J44 Potassium Chloride, ..... 149 Potassium hydroxide, ... .139 Potassium oxide, ...... 138 Potassium phosphate, ... .147 Potassium silicate, ..... 134 Potassium sulphate, .... .146 Prosenchyma, ....... 255 Protagon, ........ .123 Proteoses, 100 Protoplasm, .245 Protein bodies, or Proteids, . . 87 Proximate Principles, .... 37 Quack grass, ........ 287 Quantitative relations among ingredients of plant, . . . 220 Quartz, .134 Quince seed mucilage, .... 62 Radicle, 333 Rafflnose, 68 Reproductive Organs, . . 243, 315 Rhizome, 287 Rind, 297 Rock Crystal, 134 Root-action, imitated, . . . .400 Root-action, Osmose in ... 399 Root cap, .257 Root distinguished from stem, 258 Root excretions 280 Root hairs, 265 Root, Seat of absorptive force In, 270,399 Root stock, 287 Rootlets, 260 Roots, Growth of 256 Roots contact with soil, . . . 2ftf Roots going down for water, . .276 Roots, Search of food by . . .263 Roots, Quantity of 263 Rubidium action on oat, . . .209 Rxinners, , 286 Saccharose, 60 Saccharose, Amount of, in plants 66 Sago, -51 Salicin, 69 Salicornia, 191 Sal-soda, 145 Sal sola, 191 Salts, Definition of 81 Salts, in ash of plants, . . . .143 Saltwort, ......... m INDEX. 415 Samphire, . 191 Sap, 369 Sap, Acid and alkaline . . . .378 Sap ascending, 379, 384 Sap descending, 382 Sap, Composition of 376 Sap of sunflower, 378 Sap, Spring flow of . . . , . 370 Sap wood, .305 Saponification, 85 Saxifraya crustata, 206 Seed, 332 Seed vessel, 330 Seed, Ancestry of 346 Seeds, constancy of composition!45 Seeds, Density of 339 Seeds, Weight of 340 Seeds, Water imbibed by . . .399 Selective power of plant, . . .401 Seminose, 65 Sepals, 317 Sieve-cells, 303 Sieve-cells In pith, . . . . 343, 345 Silica, 134 Silica entrance into plant, . .402 Silica, Function of, in plant, . 216 Silica in ash, 197 Silica in textile materials, . . 200 Silica unessential to plants, . .197 Silicates, 134 Silicate of potassium, ... .134 Silicic acids, 135 Silicon, 134 Silicon, Dioxide 134 Silk of maize, 319 Silver-grain 299 Sinapin, 120 Soaps, 93 Sodium, 139 Sodium carbonate, 144 Sodium essential to ag. plants? 186 Sodium hydroxide, 139 Sodium in strand and marine plants, .191 Sodium oxide, 139 Sodium sulphate, 146 Sodium, Variations of, in field- crops, 188 Sodium Chloride 149 Soil. Offices of 368 Solanin, 121 Solution of starch in Germina- tion, 358, 361 Soluble silica, 135 Soluble starch, 52 Species, 326 Spirits of salt, 133 Spongioles, 257 Spores, 316 Sports, 327 Stamens, 318 Starch, amount in plants, . . 51 Starch-cellulose, 50 Starch estimation, 52 Starch in wood, 373, 376 Starch, Properties of .... 47 Starch, Test for 49 Stearicacid, 86 Stearin, .......... K r > Stem, Endogenous ..... 290 Stem, Exogenous 296 Stem, Structure of 289 Stems, 282 Stigma, 318 Stomata, .309 Stool, 287 Suckers, 287 Sucroses, 39, 65 Sugar, Estimation of . . . . .66 Sugar, in cereals, 69 Sugar in Sap, .377 Sugar of milk, 68 Sulphate of lime, 146 Sulphate of potash 146 Sulphate of soda 146 Sulphates, 26, 131, 146 Sulphates, Function of ... .210 Sulphates reduced by plant, . 208 Sulphides, .26, 130 Sulphide of potassium, ... .130 Sulphites, 129 Sulphur, 25, 129 Sulphur in oat, 208 Sulphur dioxide, 25, 130 Sulphureted hydrogen, . .26, 115 Sulphurets 26 Sulphuric acid, 26, 130 Sulphuric acid in oat, ... .208 Sulphuric oxide (SO S ), .... 209 Sulphur trioxide (SOg), . . .25,130 Sulphurous acid, 25, 129 Symbols, Chemical ..... 31 Tao-foo 96 Tapioca, ..........51 Tap-roots, 259 Tartaric acid, 80 Tartrates, 80 Tassels of maize, ..... .319 Theobromin, 118 Tillering, .287 Titanic acid 137 Titanium, 137, 209 Translocation of substances In plant, 237 Trypsin, 104 Tubers, .273, 288 Tuscan hat-wheat, ..... 158 Tyrosin, 116 Ultimate Composition of Vege- table Matters, 13, 29 Umbelliferous plants, .... 330 ' Unripe seed, Plants from . . .338 Urea, 115 Valence, 35 Varieties, 158,326,327 Vascular bundle of maize stalk, 291,293 Vascular-tissue, 255 Vegetable acids, ...... 75 Vegetable albumin, ..... 90 Vegetable casein 94 Vegetable cell, ...... .243 Vegetable fibrin, 92 Vegetable globulins, 97 Vegetable mucilage,. .... 57 Vegetable myosina, 98 416 HOW CROPS GROW. Vegetable parchment, .... 44 Vegetable tissue, 246 Vegetative organs 243 Vernin, 118 Vicin, 120 Vitality of roots, 282 Vitality of seeds 335 Vitellin, 96 "Water, Composition of .... 37 Water, Estimation of .... 39 Water, Formation of .... 24 "Water in air-dry plants .... 39 Water in fresh plants, .... 38 Water in vegetation, Free ... 39 Water in vegetation, Hygro- scopic, 39 "Water-oven, 88 Water-culture, 181 Water-glass, 135 Water Boots, 273 Wax, 83 Wood, 41,305 Wood cells 293 Wood cells of conifers, . . . .301 Woody stems, 305 Woody tissue, 255 Xylin, 61 Xylose, 62 Yeast 103 Zanthophyl, 125 Zein, 93 Zinc M * ^ . . . . . , . The Cereals in America By THOMAS F. HUNT, M.S., D.Agrl, Professor of Agron- omy, Cornell University. If you raise five acres of any kind of grain you cannot afford to be without this book. It is in every way the best book on the subject that has ever been written. It treats of the cultivation and improvement of every grain crop raised in America in a thoroughly practical and accurate manner. The subject-matter includes a comprehensive and succinct treatise of wheat, maize, oats, barley, rye, rice, sorghum (kafir corn) and buckwheat, as related particularly to American conditions. First-hand knowledge has been the policy of the author in his work, and every crop treated 13 presented in the light of individual study of the plant. If you have this book you have the latest and best that has been written upon the subject. Illustrated. 450 pages. 5J^ x 8 inches. Cloth $1.75 The Forage and Fiber Crops in America By THOMAS F. HUNT. This book is exactly what its title indicates. It is indispensable to the farmer, student and teacher who wishes all the latest and most important information on the subject of forage and fiber crops. 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Bound in cloth, with gold stamp- ing. It is unquestionably the handsomest agricultural reference book that has ever been issued. Price, postpaid . . . $2.00 Clean Milk By S. D. BELCHER, M.D. In this book the author sets forth practical methods for the exclusion of bacteria from milk, and how to prevent contamination of milk from the stable to the consumer. Illustrated. 5x7 inches. 146 pages. Cloth. . 4 . . * 4 4 ,* * . _ $1.00 Bean Culture By GLENN C SFV*.Y, B.S. A practical treatise on the pro- duction and marketing of beans. It includes the manner of growth, soils and fertilizers adapted, best varieties, seed selec- tion and breeding, planting, harvesting, insects and fungous pests, composition and feeding value; with a special chapter on markets by Albert W. Fulton. A practical book for the grower and student alike. Illustrated. 144 pages. 5x7 inches. Cloth $0.50 Celery Culture By W. R. BEATTIE. 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Part 1 By J. E. MORSE, the well-known Michigan trucker and originator of the now famous and extremely profitable new methods of dark forcing and field culture. Part II Compiled by G. B. FISKE. Other methods practiced by the most experi- enced market gardeners, greenhouse men and experimenters in all parts of America. Illustrated. 130 pages. 5x7 inches. Cloth. $0.50 Alfalfa By F. D. COBURN. Its growth, uses and feeding value. The fact that alfalfa thrives in almost any soil; that without reseeding it goes on yielding two, three, four and sometimes five cuttings annually for five, ten or perhaps 100 years; and that either green or cured it is one of the most nutritious forage plants known, makes reliable information upon its pro- duction and uses of unusual interest. Such information is given in this volume for every part of America, by the highest authority. Illustrated. 164 pages. 5x7 inches. Cloth. $0.50 Ginseng, Its Cultivation, Harvesting, Market ing and Market Value By MAURICE G. KAINS, with a short account of its histonr and botany. It discusses in a practical way how to begin with either seed or roots, soil, climate and location, preparation, planting and maintenance of the beds, artificial propagation, manures, enemies, selection for market and for improvement, preparation for sale, and the profits that may be expected. This booklet is concisely written, well and profusely illus- trated, and should be in the hands of all who expect to grow this drug to supply the export trade, and to add a new and profitable industry to their farms and gardens without inter- fering with the regular work. New edition. Revised and en- larged. Illustrated. 5x7 inches. Cloth. . . . $0.50 Landscape Gardening By F. A. WAUGH, professor of horticulture, University of Vermont. A treatise on the general principles governing outdoor art ; with sundry suggestions for their application in the ccmmoner problems of gardening. 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A practical handbook on the most approved methods in growing, harvesting, curing and sellir/g hops, and on the use and manufacture of hops. The result of years of research and observation, it is a volume destined to be an authority on this crop for many years to come. It takes up every detail from preparing the soil and laying out the yard to curing and selling the crop. Every line represents the ripest judgment and experience of experts. Size, 5x8; pages, 300; illustrations, nearly 150; bound in cloth and gold; price, postpaid, $1-50 ) Tobacco Leaf By J. B. KILLEBREW and HERBERT MYRICK. Its Culture 1 and Cure, Marketing and Manufacture. A practical hand- book on the most approved methods in growing, harvesting, curing, packing and selling tobacco, with an account of the operations in every department of tobacco manufacture. The contents of this book are based on actual experiments in field, curing barn, packing house, factory and laboratory. 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A practical guide to the culti- vation and propagation of Fruits, written from the standpoint of the practical fruit gro\ver who is striving to make his business profitable by growing the best fruit possible and at the least cost. It is up-to-date in every particular, and covers the entire practice of fruit culture, harvesting, storing, mar- keting, forcing, best varieties, etc., etc. It deals with principles first and with the practice afterwards, as the foundation, prin- ciples of plant growth and nourishment must always remain the same, while practice will vary according to the fruit grower's immediate conditions and environments. Illustrated. 265 pages. 5x7 inches. Cloth $1.00 Plums and Plum Culture By F. A. WAUGH. A complete manual for fruit growers, nurserymen, farmers and gardeners, on all known varieties of plums and their successful management. This book mark? an epoch in the horticultural literature of America. It is a complete monograph of the plums cultivated in and indigenous to North America. It will be found indispensable to the scientist seeking the most recent and authoritative informa- tion concerning this group, to the nurseryman who wishes to handle his varieties accurately and intelligently, and to the cultivator who would like to grow plums successfully. Illus- trated. 391 pages. 5x7 inches. Cloth. . . . $1.50 r ruit Harvesting, Storing, Marketing By F. A. WAUGH. A practical guide to the picking, stor- ing, shipping and marketing of fruit. The principal subjects covered are the fruit market, fruit picking, sorting and pack- ing, the fruit storage, evaporating, canning, statistics of the fruit trade, fruit package laws, commission dealers and dealing, cold storage, etc., etc. No progressive fruit grower can afford to be without this most valuable book. Illustrated. 232 pages. 5x7 inches. Cloth $1.00 Systematic Pomology By F. A. 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A complete exposition of important facts concerning the relation of bacteria to various problems related to milk. A book for the class- room, laboratory, factory and farm. Equally useful to the teacher, student, factory man and practical dairyman. Fully illustrated with 83 original pictures. 340 pages. Cloth. 5'/ 2 x 8 inches $1.25 Modern Methods of Testing Milk and Milk Products By L. L. VANSLYKE. This is a clear and concise discussion of the approved methods of testing milk and milk products. All the questions involved in the various methods of testing milk and cream are handled with rare skill and yet in so plain a manner that they can be fully understood by all. The book should be in the hands of every dairyman, teacher-or student. Illustrated. 214 pages. 5x7 inches f . $0,75 Farmer's Cyclopedia of Agriculture A Compendium of Agricultural Science and Practice on Farm, Orchard and Garden Crops, and the Feeding and Diseases of Farm Animals