l|f i. 1. m\n TXtbrarg ^nrtli (Carolina ^tatf (Enllpg^ QK178 K4 ^TURAL RESOURCES UBKAKV I.e. STATE UNIVERSITY D.H. HILL LIBRARY S00218871 R THIS BOOK IS DUE ON THE DATE INDICATED BELOW AND IS SUB- JECT TO AN OVERDUE FINE AS POSTED AT THE CIRCULATION LIBRARY 1992 JUL 3 200b 5M/7-87-871457 U. S. DEPARTMENT OF AGRICULTURE. DIVISION OF BOTANY. CONTRIBUTIONS THE U. S. NATIONAL HERBARIUM. Vol. V, No. 5. ISSTJED ^TJ&XJST 1, 1900. THE PLANT COVERING OF OCRACOKE ISLAND; A STUDY IN THE ECOLOGY OF THE NORTH CARO- LINA STRAND VEGETATION. THOMAS H. KEARNEY. JR. OK 178 K4 WASHINGTON: GOVERNMENT PRINTING OFFICE. 1900. m]t ^, ;i. ^tll %xhnxvn QKI78 K4 U. S. DEPARTMENT OF AGRICULTURE. DIVISION OF BOTANY. CONTRIBUTIONS THE U. S. NATIONAL HERBARIUM. Vol. V, No. 5. iswtjp:i:> ^vuc^us'r i, looo. THE PLANT COVERING OF OCRACOKE ISLAND; A STUDY IN THE ECOLOGY OF THE NORTH CARO- LINA STRAND VEGETATION. THOMAS PI. KEAKNKY. JR. WASHINGTON: GOVERNMENT PRINTING OFFICE. 190 0. LETTER OF TRANSMITTAL U. S. Department of Agriculture, Division of Botany, Washington, D. C, Fehruary 38, 1900. Sir: I have the honor to transmit herewith, for i^ublication as Volume Y, No. 5, Contributions from the United States National Her- barium, a manuscript b}^ Mr. T. H. Kearney, jr., assistant botanist, entitled The Plant Covering of Ocracoke Island. ResiDectfully, Frederick V. Coville, Botanist. Hon. James Wilson, Secretary of AgricuUiire. II CONTENTS. Page. Introduction 261 Climate 262 Temperature - 262 Sunshine - - 264 Atmospheric humidity.... 264 Precipitation _ 265 Wind - 266 Physiography 266 Geology and soils. 267 The plant formations, their composition and physiognoijiy 260 Sand-strand vegetation 270 Treeless, open formations 270 Beach formation 270 Dune formation 270 Evergreen tree and shrub formations 271 Tree formation : 271 Thicket formation 272 Salt-marsh vegetation _ _ , 272 Creek- marsh formation 272 Spartiua stricia association 272 Jiincus roemerianus association 273 Dune-marsh formation 274 Tidal flat formation 274 Pasture and ruderal plants _. 275 Cultivated plants 275 Ecological forms and adaptations to environment . . 275 Adaptations to the mechanical action of the wind and the instability of the soil ^ 276 Adaptations for protecting the supply of water 277 Anatomy . 280 Species of the sand strand 285 Panicum amarutn 285 Mnhlenbergia filipes 285 Spartina patens 288 Spartina stricta. . 289 Chloris petraea 290 Uniola paniculata 292 Yucca aloif olia 298 Yucca gloriosa. '. 293 Myrica carolinensis 294 Myrica cerif era 294 Quercus virgini ana ... 294 Zanthoxylnni clava-herculis 295 Croton maritimus _ - 296 III :V CONTENTS. Anatomy — Continued. Page. Species of the sand strand — Continued. Ilex vomitoria ..- 296 Oenothera humifusa 297 Teucrium nashii 297 Physalis viscosa 298 Salt-marsh species . - 301 Triglochin striata 301 Spartina stricta 301 Juncus roemerianus .-. T^^ Sesuvium maritimum i/ Tissa marina r02 Kosteletzkya virginica 303 Ammania koehnei ?03 Vincetoxicum palustre. c - j Lippia nodiflora c04 Monniera monniera ^)5 Solidago sempervirens £05 Aster tenuif olius 306 Aster subulatus ._ 306 Baccharis halimifolia 307 Iva frutescens 508 Borrichia frutescens 309 Geographical affinities of the flora - 312 List of plants collected and observed. 314 Bibliography 319 ILLUSTRATIONS. Fig. 33. JIuhlenbergia filipes — transverse section of leaf 286 34. Muhlenhergia filipes — ventral epidermis of leaf 286 35. Mulilenhergia filipes — dorsal part of leaf blade ^ 286 36. Muhlenhergia filipes— xtortion of mestome bundle 287 37. Chloris p>etraea — leaf blade. . . . 290 38. Chloris petraea — ventral portion of leaf blade 291 39. Chloris petraea — large mestome bundle from leaf blade. 291 40. Chloris petraea— thx^e small mestome bundles from the blade 292 41 . Yucca aloifolia — leaf surface 293 42. Yucca aloifolia — a stoma - 293 43. Quercus virgi^iiau a— stellate hair from dorsal leaf surface 295 44. Croton maritimus — hair from dorsal leaf surface 296 45. Physalis v/scosjf— branched hair from leaf , 298 46. Tissa ??iari?ia— glandular hair from leaf margin 302 47. Lippia nodi/fora— stomata and hairs . „ 304 48. Iva frutescens — hair from ventral leaf surface 308 49. Borrichia frutescens — leaf section 309 50. Borrichia frutescens — leaf hairs 309 THE PLANT COVERIXG OF OCRACOKE ISLAND: A STUDY IN THE ECOLOGY OF THE NORTH CAROLINA STRAND VEGETATION. By Thomas H. Kearney, Jr. INTRODUCTION. In October, 1898, in the course of field work for the United States Department of Agriculture, the writer spent five days upon Ocracoke Ishmd, North Carolina. Owing to its limited size, it was possible, even in that short time, to explore somewhat thoroughly a considei*- able part of the island. It is to be regretted that visits were not made to the localit}^ earlier in the season, so that the plienologieal develoj)ment of the vegetation could be studied. However, as most of the characteristic plants of our southern Atlantic strand are rather late in maturing, it is probable that a better season for a single visit could not have been chosen. It was of course impossil)le to make any valuable observations upon fecundation and dissemination, important as these subjects are to the study of the geographical dis- tribution of plants. AVliat is said here of Ocracoke will doubtless apply, in a general Avay, to the other sandy reefs of the Xoi-tli Caro- lina coast. The object of this paper is a study of the ecology and geography of the vegetation of the island, the several divisions of the suliject ))eiiig presented in the following order: (1) Climate; (2) physiography; (3) geology and soils; (4) the plant formations, their composition and physiognomy; (5) ecological foinis — adaptations to environment; (G) anatomy; (7) phytogeograplnCal affinities of the flora. The nomenclature used is mainly that followed in Hrittoii and Brown's Illustrated Flora of the Northern United States and Canada, but, in order that those who are interested in ecological work and are not familiar with this nomenclature maj'find no difficulty in recognizing the species described, the names used in the later works of Gray and of Chapman are quoted in parentheses. A full list of all plants collected or observed upon the island is appended, and here, again, familiar syno- nj^ms are cited in parentheses. A list of the works quoted, Avith their full titles, is given at the end of the paper. In the i^reparation of the anatomical portion of the pap<'r, Mr. 261 -t!'J THE PLANT COVERING OF OCRACOKE ISLAND. 1 heodor Holm has rendered valuable assistance, and lie has kindly furnished the drawings for figures Nos. 1 to 8, 17, and IS. The other figures were drawn from nature hy the author. CLIMATE. The following data have been obligingly furnished ])y the United States Weather Bureau. The observations were made at the Hatteras Station, only a few miles northeast of Oeracoke. TEMPERATURE. Readings were taken in the shade.' The observations at Hatteras cover a period of about twenty years. The average number of days per annum with a temperature exceeding 6° C. (43° F.) is 365, Avhile at Norfolk, Ya., the number is only 295. The sum total of temperatures above 6° C. during the year averages 3,740.4:° C. (0,740° F.), which is notably higher than the Norfolk figure of 3,359.4° C. (6,047.0° F.). The normal mean temperature during the six consecutive hottest weeks of summer is 25.0° C. (78.6° F.), as compared with the slightly higher mean of 26.3° C. (79.3° F.) at Norfolk. The normal annual temperature is 16.3° C. (61.4 F.), as comimred with 14.8° C. (58.7° F.) at Cape Henry, Virginia, 15.0° C. (59.0° F.) at Norfolk, Va., and 17.2° C. (63.0° F.) at Wilmington, N. C. The normal monthly temperatures are as follows: January . February March April May June Degrees C. Degrees F. 7.6 1 45.7 1 8.1 46.6 10.0 50.1 1 u.o 57.2 , 19.1 66.4 ; 3:13 74.0 ' .1 Degrees C. , Degrees P. July August . .. September October . . November December 25. 5 77.9 2.5. 2 77.4 2:3.2 7u. 7 18.0 64.5 13.1 55.6 9.0 48.2 The normal daily range of temperature for the whole year amounts to 6.3° C. (11.3° F.),as compared with 8.2° C. (14.7° F.) atCapellenry, 8.8° C. (15.8° F.) at Norfolk, and 9.6° C. (17.3° F.) at Wilmington. The normal dail}^ ranges for each month are as follows : January . February March April May June Degrees C. Degrees F.jj 7.0 12.7 7.1 12.8 7.2 12.9 6.9 12.5 6.4 ^ 11.5 5.7 1 1 10.3 Degrees C. Degrees F. July August September October . . . November December . 5.1 5. 3 10.0 9.3 9.6 10.2 11.3 12.8 ' Consequently they do not represent the temperature to which most of the vege- tation is actually exposed, being subject to insolation during the hours of sun- shine. They are chiefly valuable for purposes of comparison with other climates. TEMPERATURE CONDITIONS. 263 The absolute maximum temperature observed was 38. 8° C. (102° F ) as compared with 39.4° C. (103° F.) at Cape Henry, 38.8° C. (102° F ) at Norfolk, and 39.4° C. (103° F.) at Wilmington. The absolute minimum temperature observed w as 13. 3° C. (8. 0° F ) ascomparedwith — 15.0° C. (5.0° F.) at Cape Henry, — 1G.G° C (2 0^ F.) at Norfolk, and — 12.8° C. (9.0° F.) at AVilmington. The absolute monthly maxima and minima are as follows: Month. Maxi mum. Minimum. Degrees C. Degrees F. Degrees C. Degrees F. Jamxary 26.1 22.8 29.4 30.0 33.9 38.8 37.2 36.1 a5.o 32.2 26.1 22.8 79 73 85 86 93 102 99 97 95 90 79 73 -10.0 -11.7 - 3.3 - 0.6 6.1 12. 8 16.1 16.6 10.0 5.5 -13.3 February. U March... 11 April.. 26 May... 31 June 43 July 55 August 61 September _ 62 October 50 November 43 December 28 8 The average date of the latest killing frost in spring is February 25, as compared with March 19 at Cape Henry, March 2G at Norfolk, and March 15 at Wilmington. The latest recorded was April 5, as compared with April 19 at Cape Henry, April 26 at Norfolk, and April 20 at Wilmington. The average date of earliest killing frost in autumn is December 13, as compared with November 14 at Norfolk and Cape Henry and November 12 at Wilmington. The earliest killing frost recorded was on November 12, as compared with November 14 at Cape Henry, Octo- ber 15 at Norfolk, and October 13 at Wilmington. From the above data the temperature may be characterized as fol- lows: Warm, but not excessive, with a considerable sum total of effective temperatures during the growing season, and usually mild temperatures during the very brief dormant period. The normal temperature is at least (j.5° C. above freezing point during every month of the year. The normal amount of daily variation of tem- perature is, according to the season, from 5° to 7° C, a relatively very small range. The period between the average dates of the earliest killing frost in autumn and of the latest in spring, which may be taken as very roughly coinciding Avith the dormant period of most of the vegetation, covers only seventy-four days. 264 THE PLANT COVERING OF OCRACOKE ISLAND. SUNSHINE. The observations cover a period of nearly thirty years. Normal annual sunshine,^ stated in percentages of possible sunshine, 54, as compared with 52 at Cape Henry, 51 at Norfolk, and 52 at Wilming- ton. The monthly percentages are as follows: Month. January February March .. April Per cent. Month. May — June . . , July... August Per cent. Month. Per cent. September October... November December Normal annual sunshine, stated in Irours, 2,392.2, as compared with 2,314.G at Cape Henry, 2,270.1 at Norfolk, and 2,312.7 at Wilmington. The normal monthly number of hours of sunshine are: Month. Hours. Month. Hours. Month. Hours. 144.7 143.7 193.4 216.0 Mav 256.2 September 208.3 February March AT»ril 238.9 October... 203.0 July 243.1 November 167.4 August - 216.9 j December 160.6 1 These records yield the result that the normal annual percentage of sunshine is low compared with that in much of the territory of the United States, especially west of the Mississippi River; but it is not much less than that prevailing in other parts of the Southeastern States, while it exceeds the percentages given for the northern portion of the Atlantic slope. ATMOSPHERIC HUMIDITY. This is stated in percentages of possible saturation, which of course varies at different seasons with the temperature, etc. Annual (for a period of seven years), 81.4 as compared with 74 at Cape Henry, and 73 (during nine years) at Norfolk and Wilmington. Monthly, as follows : Month. Per cent. January . February March — April Month. Per cent. Month. May — June ... July.... August September. October November. December . Per cent. The annual percentage thus shown is greater than that recorded for any other station in the United States, excepting those in the ' These figures only approximate the real values. They are derived from statis- tics of cloudiness. RAINFALL. 265 Puget Sound region, and even there the excess over the Hatteras figure is not great. Moreover, this humiditj^ is distributed throughout the months of the year with remarkable uniformity, the variation between any two months amounting to not more than o per cent. PRECIPITATION. This is stated in centimeters and inclies. Annual, 159.4 centimeters {66.41 inches), as compared with 125.6 centimeters (52.34 inches) at Cape Henrj^, 125.0 centimeters (52.1 inches) at Norfolk, and 130.4 centimeters (54.34 inches) at Wilmington. Monthlj^, as follows: Month. January. February March . . . April Cen- time- ters. 14.3 10.7 14.6 11.3 Inch es. 5.91 4.47 6.10 4.73 Month. May ... June... July... August Cen- time- ters. 11.0 10.9 15.4 15.3 Inch- es. 4.60 4.57 6.43 6.a5 Month. September October . . . November December . Cen- time- ters. Inch- 15. 4 14.8 13.4 13.1 ti.44 6.17 5.18 5.47 The average annual number of rainy days is 123.8, as compared with 125 at Cape Henry, 131.3 at Norfolk, and 128.8 at Wilmington. The average monthl}^ number of raiu}^ days is as follows : Month. Days. Month. Days. 1 Month. Days. January , 15.9 10.3 11.9 8.4 May June 10.0 9.6 10.3 10.3 September 13.7 February October 7.5 July November 6.7 April August December 9.5 At Hatteras the precipitation consists almost entirely of rain. Rain- bearing storms usually approach from a westerl}' direction. AVinter and spring rains are usuallj^ of light intensity and long duration, while those of the summer and fall are more often brief and torrential in character. The results viewed comparatively are as follows: Tlie normal annual rainfall is remarkably heavy, exceeding that at the nearest station, Wilmington, by 30 centimeters. Only on the coast of Wash- ington and Oregon does the total rainfall within tlie limits of tlie United States notably exceed that of Hatteras. The normal varia- tion between the month of least and that of greatest rainfall does not exceed 5 centimeters, so that in ordinary seasons periods of drought do not occur. The heaviest rainfall occurs in tlie months from July to October. The average number of rainy days is large, about one-third of the days of the year, and is distributed with relatively great uniformity, varying from 6.7 days in the montli of least to 15.9 in the month of greatest number of rainy days. Of dewfall no statistics could be obtained. 266 THE PLANT COVERING OF OCRACOKE ISLAND. WIND. The average annual maximum velocity of the wind is 21.4 kilome- ters (13.3 miles) per hour, as compared with 23.2 kilometers at Cape Henry, 15.1 at Norfolk, and 15.4 at Wilmington. The average monthly maximum velocities, stated in kilometers and miles, are as follows: Month. January. February March . . . April Kilo- me- ters. Miles 25.0 15.5 24.5 15.2 25.2 15.6 24.2 15.0 Month. May ... June . . . July... August Kilo- me- ters. Miles 20.3 12.6 21.3 13.2 18.5 11.5 19.7 12.2 Month. September October . . . November December. Kilo- me- ters. 17.2 18.4 19.8 24.0 Miles 10.7 11.4 12.3 14.9 In regard to direction, the winds of midwinter are usually from the north, while those of midsummer are usually from a little west of south. As thus shown, the average velocity of the wind is considerable, and the amount of its variation from month to month is remarkably" slight. The highest average of course prevails in winter and early spring. In midwinter, when the winds are normally strongest and therefore most affect the perennial, especially the woody vegetation, their prevailing direction is almost due south (from the north), hence, in the case of Ocracoke, from tlie mainland. In regard to temperature, rainfall, and atmospheric humidity the climate of Ocracoke and Hatteras is suitable for a vigorous forest growth. But the exposure to strong winds, and the peculiar soil con- ditions, neutralize these favorable factors and give it a typical strand vegetation, which much resembles that of deserts. In the neighbor- hood of Norfolk and of Wilmington, where conditions of temxjerature and of humidity are really somewhat less suitable than at Hatteras to the most luxuriant develo]3ment of j^lants, the virgin growth is almost eveiywhere dense forest, because there the inimical conditions are absent. PHYSIOGRAPHY. Ocracoke Island is part of that long chain of narrow sand reefs which fringes the southern Atlantic Coast of the United States, and which forms the eastern bariier to a series of almost land-locked bays and sounds. Ocracoke lies in longitude 76° west and latitude 35° 10' north, and is therefore somewhat south of the center of the North Carolina coast. It is separated from Hatteras Reef by the 0.8 kilo- meter (one-half mile) wide strait known as Hatteras Inlet, and from Portsmouth, the next island below, by Ocracoke Inlet, 3 kilometers (nearly 2 miles) wide. Ocracoke itself is about 26 kilometers (16 miles) in length, and extends from that great bulge of the coast line GEOLOGY OF THE ISLAND. 267 known as Cape Ilatteras, in a southwesterly direction. Tlio islancrs greatest width near its lower end falls short of 3 kilometers; the aver- age width is only 1 kilometer, while in places it is even narrower. Outside rolls the Atlantic, while between island and mainland stretch the waters of Pamlico Sound, here from 30 to 45 kilometers (18 to 27 miles) wide. Pamlico differs from the shallower Albemarle Sound 1o the north in the important respect that its water is always salt, while Albemarle is normally fresh. Near the so tith western extremity of the island a broad expanse of tidal flat separates the higher land of the village of Ocracoke from the Atlantic beach. One and one-half kilometers or so toward the northeast this lagoon disappears, and dry land extends from the flat sandy beach and the salt marshes which border the Sound to the dunes which front the ocean. Into these marshes penetrate tiny ci'eeks, whose ramifications cut the lower part of the island in all directions. Almost the whole area is divided between sand strand and tidal mai'sh. Much of it is only 1 meter or less above normal high tide and subject to overflow when strong easterly gales a re blow- ing, or when stiff breezes from the opposite quarter mass the waters of Pamlico Sound against the western shore of the island. The high- est land on Ocracoke is rex^resented by sand dunes often 3, sometimes 8 meters high. These are usually regular in form and fairly well fixed by the vegetation. Those that abut upon the outer beacli or rise amid the mud flats are particularly regular and dome-shaped. GEOLOGY AND SOILS. Of the geology of Ocracoke and its neighbor Ilatteras, we have comparatively little knowledge. Shaler^ has jidvanced the theory that these reefs were built up from the detritus which resulted from the glacial excavation of Delaware and Chesapeake bays. Kerr- describes Ilatteras as a "sort of delta." "The action," he says, "of the tides and ocean ctirrents, the Gulf stream and Arctic current meeting at this i^oint, accumulates upon Ilatteras tlie river silt wliieh reaches the sea by way of the Chesapeake as well as that of tin' rivers which discharge their burdens through the inlets about this point ami southward. * * * Ilatteras is not a modern phenomenon. It is at least as old as the Cretaceous; tlie Quaternary as well as tlie Ter- tiary of this coast region of North Carolina are laid down ui)on an eroded surface of Cretaceous rock." From measnrements elsewhere made, the probable depth beneath the surface of the Cretaceons for- mation on Ilatteras and (Ocracoke would be somewliere between I'on and 300 meters. lam not aware that borings of any <'onsiderabhMleptJi 1 Proc. Bost. Soc. Nat. Hist., vol. 14, pp. 110 to 121. 1872. •^Bul. Wash. Phil, boc, vol. (5, pp. '-38 to :JU. 1884. 268 THE PLANT COVERING OF OCRACOKE ISLAND. have been made upon these islands.^ Kerr further states that * ' the reef is increasing in continuity and breadth." But this is not the gen- eral opinion, for it is said that there is to-daj' water of considerable depth where houses stood upon Ocracoke within the memory of living men, and it is stated^ that "a fine fig orchard and many peach trees, with a fine potato patch and garden," occupied earlier what is now Hatteras Inlet. That the present tendency of this whole coast line is one of subsidence can hardly be disputed. Beneath the superficial Recent deposits of dune sands and salt- marsh silt which cover the greater part of the island lie the sands and clays of the Columbia formation, which extend to a considerable but unascertained depth. This and the Recent accumulations are the onh^ geological formations of this part of the coastal plain which need be considered in relation to the existing plant covering. Excepting the areas occupied by creeks and salt marsh, the soil of Ocracoke is a fine white marine sand, almost everywhere devoid of any considerable admixture of humus. Only in the live-oak groves is there enough A^egetable matter present to give the sand a gray color. There is doubtless some quantity of calcium carbonate in the soil, owing to the presence of small particles of shells washed up by the waves and scattered b}^ the wind.-^ As much of the island is subject to occasional inundation and to the deposition of spray by the winds, the soil content of sodium chlo- rid must be considerably greater at times than in ordinary inland soils.^ There is no lack of moisture in this sandy substratum. Even in the driest looking beach sand, water usually stands at a depth of only 15 to 30 centimeters (6 to 12 inches) from the surface. The superficial layer of the sand acquires a great amount of heat on sunny days and becomes thoroughly desiccated, in which condition it is subject to being blown about by the wind, its degree of coherenc}^ depending upon the character of the vegetation. At night, however, sand gives up its heat rapidly and absorbs much dew, if conditions are favorable.'^ The soil of the salt marsh, which appears to be usually a thin sheet ' The succession of strata in the North Carolina coastal plain, where exposed in the valleys of the Neuse and Cape Fear rivers, is given as follows, beginning with the oldest: (1) Potomac gravel, sands, and clays. (2) Cretaceous sands and clays. (3) Tertiary (Eocene and Miocene) marls and clays. (4) Lafayette (yellowish and brownish sands and loams). (5) Columbia sands, gravels, and clays. 2W. L. Welch, Bui. Essex Inst., vol. 17, pp. 87 to 42. 1886. ■^According to Contejean (Geogr. Bot.),the proportion of calcium carbonate thus supplied to the strand soils is insignificant except near the wave limit, the particles being soon dissolved by the carbon dioxide contained in rain water and then washed down through the readily permeable soil. ^Sea water contains from 2.7 to 3.2 per cent of NaCl. ^Warming, Lehrbuch, p. 66. ECOLOGICAL CROUPS. 269 of fine, brown silt overlying a stiff, bluish ehiy, contains orj^^anic mat- ter in considerable quantity and is therefore capable of supporting a denser plant growth than is found upon the sands. It is of course saturated with salt or brackish water. There is no outcrop of any kind of rock on tlic island. THE PLANT FORMATIONS, THEIR COMPOSITION AND PHYSIOG- NOMY. The various assemblages of species and individuals which make up the plant covering of Ocracoke Island may be classified as follows:* L Sand-strand vegetation. 1. Treeless (open). (a) Beach formation: Croton-Physalis association. (b) Dune formation: * Uniola-Yucca association. 3. Evergreen trees and shrubs. (a) Tree formation: Quercus virginiana association. (6) Thicket formation: Ilex vomitoria association. II. Salt-marsh vegetation. 1. Creek-marsh (closed) formation. (a) Spartina stricta association. (b) Juncus roemerianus association. 3. Dune-marsh formation; Lippia-Monniera association. 3. Tidal flat (open) formation: Sesuvium-Tissa association. III. Pastures and ruderal plants. IV. Cultivated plants. It is not to be supposed that the severial groups are always or even commonly sharply defined. On the contrary the transition from one to another is almost always gradual, so that iDortions of the plant covering are difficult to classify. Nevertheless, the formations and associations are distinct features of the landscape, easily recognizable by any observer. ' It has seemed best to use the word ''formation *' in the same sense as employed by the German and most other plant geo-raphers— i. e., to designate ihe larger assemblages. For more restricted groups, whether composed of one or many species, the term ''association'' is to be preferred. The nearly ejuivalent German word "Verein"' is used as a translation of the Danish "Sanifuud" in one of the most important works on the subject (Warming, Lehrbuch) for the larger assemblages or formations; but, in the want of a better English word it has been thought expedient to employ '' association *' for the more restricted assem- blages, which are peculiar to each biogeographical area. While the ft^rmations are purely ecological elements which recur in the strand vegetation of other regions, being for the most part closely dependent upon topographical features, the asso- ciations are often quite local; and owe much of their character to the particular groups of species which compose them. ' It is not possible to distinguish here several dune formations, such as occur, for example, on the coast of Virginia. _^70 THE PLANT COVERING OF OCUACOKE ISLAND. SAND-STRAND VEGETATION. TREELESS, OPEN FORMATIONS. BEACH FORMATION. This forination occurs along Pamlico Sound, occupj'ing the flat or gently sloping sandy beach, especially toward the lower end of the island. The species are almost all herbaceous and usually form an open vegetation, leaving much of the soil uncovered. The most abundant is Croton maritimus, which sometimes grows rather closely, excluding other species. By reason of its silvery-gray color, due to a close, stellate, scale-like pubescence, it is one of the most conspicuous plants of the island. It is usually stout and often much-branched. Another noteworthy plant is Physalis viscosa, a perennial herb, Avith slender roots, sometimes 1.5 meters long, creeping near the surface of the sand, and sending up at intervals short leaf}' shoots. Its color varies from green to gray with the density of its covering of branched hairs. An interesting feature of this formation is the occurrence in places of diminutive thickets onl}" 1 to 3 decimeters high, composed chiefly of Ilex vomHoria {I. cassine of. authors), Zanthoxylon cJara- herculiSy Juniperus virginiana, with leaves only of the spreading form, and Opuntia pes-corvi, with its long spines. Among other species belonging to the beach formation, there are of annual herbs En- pliorhia polygonifoUa, Triplasis purpurea, a canescent form of Sola- num nigrum,, a large-fruited Xanthium, and Salsola kali, the last being the most abundant; of perennial herbs Teucrium imsliii, with slender stolons and white-tomentous lower leaf surface, Chloris petraea, with decumbent culms, rooting at the nodes, Panicum neu- ranthum, and occasional!}' CaprioJa dactylon {Cynodon dadylon Pers.); of woody plants Buhus trivial is and Smilax boua-iwx oecnr here and there, with prickly stems trailing over the sand. DUNE FORMATION. Open dunes are occupied chieflj^ b}' the handsome sea oats, Uniola paniculata, the most characteristic strand plant of the Southeastern States. The low, rounded dunes Avhich rise from a bare pebbly shingle on the ocean side of the island, and here and there in the tiiidst of the tidal flats, support no other vegetation. The leafy shoots of this grass are iDroduced in great abundance, but flowering branches are much less numerous.^ Mulilenhergia filipes is abundant on and among the dunes, its delicate purplish panicles, swaj-ing with the lightest breath of air, ]3resenting a most beautiful appearance. It is almost the only cespitose plant of the island, and grows in tufts that are sometimes 3 decimeters in diameter. Rather small ' In this respect the Uniola resembles Ammophila arenaria, which takes its place farther north. TREE FORMATION. 271 plants of Yucca gloriosa, with fleshy rootstocks often exposed by the shifting of the sands, are frequent on the lesser dunes. The sinjjjle specimen of Yucca aloifolia observed was over 2 meters high, with stem branched several times above the ground. Botli species have exceedingly hard and sharp spinous leaf tips. On some of the liiglier dunes depauperate plants of the shrubby il/?/rica caroVniensiii^ mostly onl}^ 3 to 6 decimeters high, associate with the Uniola. Of secondary importance in this association are two perennial grasses, Paniruyyi amarurn minus and Spartina patens (juncea); as well as a probably biennial thistle, Carduus spinosissimus (Cnicus horridulus) ; and several other herbs, among them the white-sericeous Oeuothera humi- fusa and Croton maritimus. EVERGREEN TREE AND SHRUB FORMATIONS. TREE FORMATION. Scattered over the island, but preferring the higher dunes which occupy its inner side, are small groves of live oak, Quercus virgin tana (Q. virens), either in pure association or mixed with some other trees. The oaks are usually 6 to 9 meters high and 3 (rarely 7^) decimeters in diameter. Those on the northern edges of the groves have trunks strongly inclined toward the south, and, as a consequence of the deiUi- dation of the branches on the windward side, the whole crown of foliage lies to leeward of the axis. One could not desire a better indication of the prevailing direction of strong winds in the region.^ The branches, gnarled and twisted, are clad with numerous lichens, chiefly Usnea barbata, and with occasional small wisps of Spanish moss {Tillandsia usneoides), which evidently maintains but a precari- ous foothold on the trees of this wind-exposed island. Altogether the aspect of the groves is rather weird and somber. Often associated with the oaks are small trees of Mijrica cerifera, Zan- ihoxyluin clava-Jierculis and Ilex vomitoria, all of about the same maxi- mum size (G meters high and 2 decimeters in diameter), and occasionally Ju7iiperus virgimana, which rarelj" attains a height of *J meters and a diameter of 3 decimeters. Lianas are sparingly represented by S)n ila.v hona-nox, Vitis aestivalis, and Rhus radicans, all three species some- times attaining considerable size and climbing to the tree tops. The last is, however, usuall}^ of the creeping form, with the main stem under- ground. The herbaceous members of this association are, in the smaller groves, chiefly plants characteristic of the open strand, Cldoris 'All the specimens of live oak seen were apparently of considerable a2re. Seed- lings were few or none, and no acorns were observed. It is probable that instead of increasing, the oak is here holding its ground with difficulty. So highly are the trees valued as wind-breaks by the inhabitants that none are felled, all fuel being brought from the mainland. The rounded shrubby form of this plant, common elsewhere on the coast, was not observed on Ocracoke. 272 THE PLANT COVERING OF OCRACOKE ISLAND. petraea, Physalis viscosa, Diodia teres, etc., and the difference in soil and light is not sufficiently great to cause any apparent modification in the plants. In larger groves, where the light is more diffused and some humus collects, Oplismeniis setarius ^ covers the ground with its creeping stems, associated with such normally shade-loving species 8is Sanicula sp.y Aspleniuni platyneuron {A. ebenoides), Uniola laxa (U. gracilis), Panicinn laxiflorurn and two mosses, growing on the ground, Brymn argenteum and Rhynchostegium serrulatuni. THICKET FORMATION. Thickets of I/ex vomitoria, by far the most abundant woody plant of Ocracoke Island, often cover the low dunes, especially near the inner side of the island. The plants are here usually 10 to 20 deci- meters high, with short, rigid, thorn-like branches, light-gray bark, thick evergreen leaves and bright scarlet berries. The branches are often shaggy with lichens, notably Ramcdina montagnei. Occasion- ally the Ilex gives place to small, dense thickets of Myrica carolinen- sis, sometimes 4^ meters high. This formation corresponds in a measure to the "Maquis" or "Garrigues" of the western Mediter- ranean region.^ The herbaceous species that have established them- selves among these shrubs are chiefly such as are most abundant on the beach and open dunes. Two thin-leaved, shade-loving herbs are occasional, Fariefaria dehilis with weak, much-branched stems, and Melotliria pendida, with twining stems. SALT-MARSH VEGETATION. CREEK-MARSH FORMATION. Salt marshes fringe all the small creeks and ditches that intersect the lower part of the island, and sometimes cover broader tracts imme- diately bordering the sound Avith a growth that is almost everywhere dense and reed-like. 'I'wo rather sharply defined belts are distinguish- able along the larger creeks, an outer, covered chiefly with Spartlna stricta, and an inner, where Juncus, roemerianus predominates. The latter alone occupies the small creeks and ditches which are farthest from the beach. SPARTINA STRICTA ASSOCIATION. The Spartina prefers the edge of open water, where it is in large part submerged at high tide. It has a light, yellow-green color dur- ing the growing season, but is brown and discolored much of the year. The stems are usually about 6 decimeters high. Scdicornia herbacea, often bright red and conspicuous, grows rather abundantly with the ' In southern Mississippi, also, I found this species growing only in the shade of Qiiercus virginiana. 2 Compare Grisebach, Veg, der Erde, vol. 1, pp. 294, 328, etc. SALT-MARSH VEGETATION. 273 grass.^ Distichlis spicata {D. maritima) usually accompanies this association, but is not of primary importance. JUNCUS ROEMERIANUS ASSOCIATION. The Juncus roemerianns association occupies mucli more ccround than that of Spartina, and comprises a much larger number of species. It is best developed on land that is merely wet a great part of the time, and covered with, at most, only a few centimeters of water at high tide. The Juncus is of a dark-green color, and usually reaches a height of about 1 meter, making a dense growth of stiff, sharp- pointed stems and leaves. Among the secondary members of tliis association certain grass-like plants occur locally in some quantity. Notable are Chaetochloa iniberhis perennis, with weak, slender culms from short, knotted rootstocks, preferring the borders of the niarsli, and Tijplia laiifolia^ usually standing in water of some depth. Spar- tina patens {8. juncea) is occasional, the salt-marsh form being smaller and more slender than that which grows upon the sand strand. Pas- palum distichum and Distichlis spicata are also met with in more open places among the Juncus. Compositae, with mostly rather succulent leaves, are conspicuous, especially near the margin of this association. Aster tenuifolius, a slender rush-like perennial species whose few branches terminate in solitary, rather large heads with showy white rays, is less abundant than the related Aster subukitus, a much-branched, often rather stout annual Avith numerous inconspicuous'heads. SoTidago sempervirens and Baccliaris halimifolia s^re most at home on the edge of the Juncus growth. Both are showy plants, the latter with bright white pappus, the former with a golden-yellow panicle. Borrichia fridescens, one of the most characteristic i^lants of the strand, ]3refers comparatively open spots where the ground is merely wet. It has a stout stem, usualh^ 3 to 6 decimeters high, thick whitish leaves, and yellow sun- flower-like heads. Iva fridescens is the most abundant composite of the marshes, almost always associating with the Juncus. Two climl)- ing plants, Galactia volid)ilis {G. pilosa) ii\\(\ Vincetoxicum palustre, a glabrous, narrow-leaved asclepiad, occur near the edges of the marsli, twining around the stems of the rushes and other plants. Atriplej- hastata is occasional in similar situations. Even Ilex voniitoria some- times strays into the marsh, growing among the Juncus as a hnv straggling shrub. Somewhat different is the assemblage of species about the small pools that frequently interrupt the growth of Juncus roemerianus. 'Likewise in southwestern France, Spartina stricfa and Salicornia herhacea form the outermost association in soil that is submerged at high tide. (Conte- jean, Geogr. Eot., p. 56.) According to Warming (Lehrlmch. p. 307) Salworuia herhacea grows unmixed with other species as the outermost embryophylic vegeta- tion on the eastern shores of the North Sea. S2)artina atrieta does not range so far north in Europe. 2965 2 274 THE PLANT COVERING OF OCRACOKE ISLAND. Their borders are the favorite habitat of a characteristic malvaceous plant, Kosteletzhya virginica, which has rather thin, pubescent leaves and large rose-colored flowers. AVith it grow a species of Rnmex, Ipomoea sagittata, Solidago semper virens, Cladium effusum (a stout sedge with sharply saw-edged leaves), Panicum ivalteri, and, very conspicuous where it occurs, Andropogon glomeratus {A. macrourus). In the shallow water of these pools grows Monniera monniera {Her- pestis monniera H. B. K.) in its aquatic, partially submerged form with elongated stems, as well as Ammannia hoehnei, Phichea ccnn- pliorata, and a species of Eleocharis. DUNE-MARSH FORMATION. A low, rather scanty vegetation covers limited areas of wet sand which fringe the reed marsh, separating it from the dry strand, and also occurs here and there in depressions among the dunes. The most characteristic species are the terrestrial form of Monniera vion- nier a ^yith short internodes, and Lippia nodiflora, both having repent stems rooting at frequent intervals and leaves usually appressed to the ground. In the case of Lippia, however, the leaves are sometimes nearly vertical in strong sunlight, giving the plant a peculiar appear- ance. Each of these species sometimes occupies small tracts to the exclusion of other vegetation. They usually grow together, however, and in association with Hydrocotyle umhellata, Centella asiatica, and Diodia virginiana, all small plants with creeping or prostrate stems. Among the dunes Lippia and Herpestis sometimes play a less impor- tant part, and an assemblage of species, some of which are not nor- mally halophilous, covers the ground. Of these Juncus dichoiomus, J. scirpoides, Scirpus americanus {S. piingens), Trigloch in striata, and Mikania scandens are more at home in saline soils, while Ludwigia 7nicrocarpa, L. alata, Cynoctouuni mitreola {Mitreola petiolata), and Dicliromena colorata (D. leucocepliala) are character plants of the fresh- water marshes of the region. Such commingling is perhaps to be explained by the fact that these hollows among the dunes derive their moisture largely from the rainfall, while, on the other hand, siDray-laden winds contribute a certain amount of salt to the soil. TIDAL FLAT FORMATION. This is an open formation, occupying the margins of the shallow lagoon at the lower end of the island, which is under water at flood tide. The soil is a mixture of silt and sand. A sparse growth of Sesurium maritimuni (S. pentandrum), Tissa marina {Lepigonum salinum), and Scirpus americanus forms a characteristic association. Faspalum disticlimn, with prostrate culms, sometimes 2 meters long, rooting at the nodes, as well as scattered erect tufts of Fimbristylis spadicea, were the only other species observed in this formation. ECOLOGICAL FORMS. 275 PASTURE AND RUDERAL PLANTS. A oonsidenible area towards tlie lower end of Ocraeoke, (^specially in and near the village, is covered with a fine turf composed almost entire!}" of Capriola dactylon, closely grazed by horses, cattle, and sheep. Here and there over these pastures are scattered groups of various weeds, notably Cassia occidentalism Sporoholus indicus, and Solarium carolinense, as well as a species of Xanihium, Bidens hipin- nata, Chenopodium antlielmiidicum, Ambrosia artimisiaefolia^ Ver- hascum fliapsus^ etc., all of which have undoubtedly l)een importeaniculata, as well as many of the salt-marsh plants, notably Juncus roemerianus, Typlw Jafifolia, and Spartina stricta, whose strong, creeping rhizomes form a dense sod in the loose mud. In Uniola paniculat a the rootstock is stout and descends obliquely or almost vertically deep into the sand. Pliy sails viscosa has a long, slender, branching root, Avhich creeps horizontally often a distance of a meter or more near the surface, and originates at intervals erect, leaf 3^ and flowering branches. Teucriurn nasliii i)ossesses thickish stolons, which arise in the axils of the scale- like, lowest leaves. Other species growing on the sands have prostrate stem branches, which do not root after leaving the main axis. These may be long and trailing, as in the woody Rubus trivialis, or short and radiating in all directions from the primary axis as in certain annuals, Diodia teres, D. virginiana, Jlollugo verticillata, and Eupliorhia polygon if olia, as well as the biennial Oenothera humifusa. This radiant form,^ as we may term it, is not so abundant and characteristic here as at other points along the Atlantic coast of the United States. The cespitose form is apparentlj^ not well adapted to conditions upon Ocracoke, for it is well developed only in Mulilenhergia filipes. The shrubs and trees of the island show the effect of much exposure to high wind in their short gnarled branches and in the often one- sided position of their crown of foliage, the last peculiarity being especially noticeable in the live oak. Here, however, w^e have to do rather with the direct mechanical effect of the wind than with a pro- tective modification. As further adaptations against the coast winds, whose destructive- ness to tender vegetation must be greatly increased by the quantity of sand they carry, should be cited the great development of mechan- ical tissue in the leaves of many species — e. g., Uniola panicuUda, Juncus Toemerianus, Quercus virginiana — and the strong thickening of the outer cell walls of, the epidermis, to which is due the hard pol- ' Schimper, Indo-Mal. Strand-flora, p. 78. ■' Schimper (Strand-flora, p. 81 ) describes this form as occurring in the East Iiidian strand vegetation. ; t:^'^>. ^ .»^. COLLECTION AND STORAGE OF WATER. 277 ished surface exhibited hy the larger grass-like plants and by the evergreen leaves of Quercus and Ilex. This last peculiarity is, how- ever, doubtless primarily induced by the necessity foiricliia, which is one of the most xerophytic in structure of all the salt-marsh species, this tissue is best developed. It is also well exemplified in 'Tissa marina. In the 3 salt-marsh inhabiting monocotyledons examined — Triylo- cliin striata, Sjoartina stricta, and Juncus roemerianus — each mes- ' Halofyt-Stndier, p. S50. 284 THE PLANT COVERING OF OCRACOKE ISLAND. tome bundle is i)rovided with a well-marked mestome sheath and, outside that, a parenchyma sheath. When Ave compare the species belonging to the two formation classes, sand-strand and salt-marsh, we find that a majority of both have several characters in common, all of which are distincth' xero- phytic and are usually interpreted as protecting the leaf against excessive transpiration as well as the effects of too intense light. These are : Thickened leaves, thickened cuticle, and development of the chlorophyll tissue as compact palisade on the most exposed sur- face or surfaces. More numerous, however, are the differential characters. The leaves of the sand-strand species are usually bifacial, with stomata only on the dorsal surface or, if on both surfaces, protected by a hairy covering or lying in deej) furrows; and the palisade is situated on the more exposed upper or ventral side of the leaf. The salt-marsh species, on the other hand, have mostly isolateral leaves, vertical or nearly vertical in i^osition, with stomata and i)alisade on both sur- faces, and (with one exception) lacking the dense hairy covering. Conformably, the most common grass of the salt marsh, Spartina stricta, otherwise so similar in leaf structure to the dune form of >S'. patens, has no hairs lining its stomatal furrows. The cuticle is wrinkled or warty in many more salt-marsh than sand-strand species. AVater-storage i3arenchyma, which is notably developed in the sand- strand vegetation onl^^ in the monocotyledons, is present in a majority of the salt-marsh plants of the most diverse relationship. Corresponding to their growth in usually open formation, and con- sequently greater exposure to the wind, the sand-strand plants show a much stronger development of stereome than do the salt-marsh species. On the other hand, the latter are better i^rovided with hypo- dermal collenchyma, or coUenchymatic tissue, opposite the veins; but this ma}^ be more imiDortant as a protection against loss of water than as a mechanical strengthening tissue. It should be emphasized that not onl}^ the peculiarities common to plants of the two formation classes, but likewise most of their respec- tive differential characters, are really of a xerophytic nature.^ In some cases, however, a different means has been employed by sand- strand species on the one hand and by salt-marsh species on the other to secure the same end — protection against excessive transpi- ration and the harmful action of too intense light. ' In his most recent paper on the subject. Warming (Halofyt-Studier, p. 235) writes: "It is not possible, from the investigations here described, to draw any clear distinction between characters which are truly xerophj^tic and such a 3 are truly halopliytic, if any really exist." Schimper (Pflanzengeogr., p. 99) also holds that halophytes can not be distinguished as a class from xerophytes, since the principal object'of the peculiarities of structure observable in plants growing in saline soil, however moist, is the reduction of transpiration, just as it is in plants snrrounded by a physically very dry soil and atmosphere. ANATOMY OF SAND-STRAND SPECIES. 285 SPECIES OF THE SAND STRAND. Panicum AMARUM Ell.^ Leaf bifacial, strongly involute when dry, midrib not prominent on the dorsal surface and not much so on the ventral surface, shjillow furrows (deepest each side of the midrib), with broad and rounded intervening ridges on the ventral surface, corresponding to very slight depressions on the dorsal surface. Epidermis: Ventral, similar to the dorsal, but willi iliinner outer cell walls; stomata at each side of the group of 3 thick-\vall(Ml 1) uni- form cells at the bottom of each furrow; hairs none. Dorsal with very thick, porous outer cell walls, 1 or sometimes 2 short cells alternating with long ones, except in the rows containing stomata; stomata lying in the shallow furrows, with walls of the guard cells much thickened; hairs none. Subepidermal stereome in large groups above and below the midrib, that above separated from the hadrome by several layers of thickish- walled, colorless parenchyma; smaller groups above and below the other nerves; strongly developed in the margins. Chlorophyll tissue (palisade) arranged radially in a single layer about each mestome bundle, almost completely encircling the smaller nerves, interrupted above and below the larger ones, each 2 neighbor- ing rows of palisade separated by a single layer of colorless paren- chyma; chloroi)hyll likewise occurring in the cells of the parenchyma sheath which adjoin the palisade. Mestome bundles surrounded each by a mestome sheath wliich, in the larger veins, has all, or nearly all, of its cells with walls (especially the inner) strongly thickened ; mestome sheath in turn surrounded by a large celled i^arenchyma sheath; mestome parenchjnna in a single layer of thick-walled cells sei^arating the hadrome from the leptome. MUHLENBERGIA FILIPE8 M. A. Curtis." Z/ea/(fig. 33)condui)licate without power to unfold, appearing as if terete, slightly asymmetrical, margins almost meeting al)ove the mid- nerve, and hence only the dorsal surface exposed. From ihe sliuhi opening between the margins to the uiidrib extends a narrow iissui-e, with lateral furrows between the larger nerves reaching more than halfway to the dorsal surface of the leaf. The ridges al)ove the mestome bundles between these furrows arc broad and rounded at apex, except that of the midnerve, which is narrowed outward (hence conical in cross section). On the dorsal (outer) surface are narrow, 'The typical form of this species was not observed upon Ocracoke JslaTid. but the leaf of var. mi)iiLs Vasey & Scribner, which was collected there, c-orrespon«ls in every detail to that of the type. - Compare Volkens's figure and description of .lr/.s//f/ p. ?2 u 13 s «2 2 H s p 3 o s -:; c c ^^J-^^ z> a-^^ P < Q « ^•-^ S ffl ffl ^ 02 ^ ,^ Cai3illaris X X X X X X X X X ■ 1 X Trichopodes X X 1 X X X X I ' Compare the figure of S. versicolor in Duval- Jouve, Etude Anat., ^>/. lC,jhj. ANATOMY OF SPARTIXA. 289 fill-rows, which aw L'-clcrt at l)<)ll(nii hy Ili<' low i-idges of lli«* siiiallc nerves. EpiderDiis: Ventral willi cells much smallrr and riiinn<'r-wallc liigli as on the dorsal surface, the walls as in .S'. jxdcns^ except that the outer wall of each cell is covered with silicilied papillae; stomata on eacli side of tlu^ bottom of the furrows; hairs none; typical bulliform <'ells none, but 1 to 3 epidermal cells at bottom of each Ncntral furrow somewhat larger than the others and probably functioning as bulli- ' Although this species belon-^'s to the salt marsh, it is described liere for the sake of convenient comparison with theoth rGram neae. Compare Duval-.Touve, Histotaxie, pi. .18, jig. r>. The Ocr icoke plant is nearly o£ the typical form. 2965 3 290 THE PLANT COVERING OF OCRACOKE ISLAND. form cells. Dorsal as in S. patens, the short cells iisuall}' single, here and there rounded, with strongly thickened walls, almost form- ing papillae; stomata none; hairs none. Hypoclermial colorless parenchyma in a single la^^er beneath the dorsal epidermis,^ interrupted hy subepidermal stereome. Stereome not strongly developed, a small subepidermal group on the dorsal side of each mestome bundle; flattened supporting strands (1 or 2 la^^ers) at the summit of each ventral ridge, not decurrent along its sides; also in the leaf margins. ChloreiicJiyma consisting of small palisade cells in a single laj^er, radially arranged on each side of each mestome bundle and extend- ing immediately beneath the epidermis to the stereome at the summit of each ventral ridge ; each 2 neighboring laA^ers of palisade, between each two nerves, either adjoining or separated by a few, large, color- less iDarenchyma cells; chlorophyll also in most of the cells of the parenchyma sheath. Mestome bundles with mestome sheath and mestome parenchyma much as in S. p)atens. Parenchyma sheath (around the mestome sheath) of large cells, those adjoining the palisade laj^er containing chloroi)hyll, the sheath occasionally interrupted on the dorsal side of the bundle by a few cells of the subepider- mal stereome. Large parenchj^ma cells, in 2 or 3 laj^ers, occup3dng the thickness of the ventral ridges and ap- pearing to be an exten- sion of the paren- chyma sheath; when in 3 layers, the middle one colorless.^ YiQ.^l.—Chloris 2^etraea—\ea,f. blade. Transverse section. show- ing the midrib in the keel, covered by layers of colorless tis- sue and a group of buUiform cells (BC) on the ventral sur- face; be, a small group of bulliform cells between two mestome bundles. The mestome bundles are indicated by their paren- chyma sheaths and by the stereome, which forms small sub- epidermal groups. The thick walled mestome sheath is drawn only in the two large bundles. Scale 84. Chlorispetraea Sw.^ Leaf (fig. 37) becom- ing conduplicate AAiien ^The specimen figured by Duval-Jouve. loc.cit., ha.s 3 or 3 layers. '-Spartina stricfa mariiima (Walt.) Scribn., the common form elsewhere along our Atlantic coast, is prat^tically identical in leaf anatomy with S. strictd from Ocracoke, except in the following particulars: The epidermis cell walls on the dorsal surface are thinner and less porous and show less of the wavy thicken- ing: the short cells are more often in pairs, and, when single, are more often papilliform; stereome is somewhat more strongly developed, as would be expected from the larger size of the plant and the greater length of the leaves. The mate- rial examined was from Lynnhaven Bay, Virginia. 'Figured by Duval-Jouve, Histotaxie, p. 35o, pi. IS, f. 1. For an example of similar leaf structure compare the same nuthor's paper. "Etude histotaxifjue des Cyperus de France," Mem. de I'Acad. de Montpellier, tome 1 pL 22, f. 6. 1874, ANATOMY OF CHLORIS PETKAEA. 291 us md slii(litly inii)ivssed veii- mestome bundle nt tho aj)ox keel. Hairs none. hiilliforin cells in a iaih(M' -5"*.. Fig. d8.—Chlnris])etruea— ventral portion of leaf blade. Transverse section, showing epidermis (£/>) and subepidermal stereome (St); at M the me.stome sheath of a bundle, bordering on layers of colorless parenchyma. Scale 240. dry, strongly keeled on tiie dorsal face trally opposite the niidvein, with a large of and 3 smaller ones on each side of th( Epidermis: Ventral, differentiated wide band above the keel and in 2 small groups of al)Out 4 cells each, 1 between the first pair of nerves on each side of the keel; elsewhere plurieellu- lar (3 or 4 layers) and occu- pying more than one-half of the thickness of the leaf, ex- cept above the larger nerves, thin-walled (excei^t the outer wall of the outermost layer) and large (except the single outermost la3^er where it lies above the subepidermal groups of stereome) ; stomata none. Dorsal epidermis one-layered, with cells all small, the outer wall and cuticle much thickened, radial walls thin, undulate, one row of short cells with strongly silicified walls alternating with several rows of long ones, many of the cells developed into rounded, not silicified, papillae; stomata in the strips of epi- dermis which lie between the nerves, level with the epidermal surface. Subepidermal stereome (fig. 38) in flattened sup- ports above and 1)elow the mestome bundles, that on the ventral side in 1 or 2 layers above the lai-ger nerves, reduced to small groups (sometimes only 2 cells) above the smaller ones; on the dorsal side supports stronger, some- times 3-layered; also in the leaf margins. Chlorencli y /// a , pa 1 i sade, arranged radially in a sin- gle row of cells on each side of each mestome l)undle, with a "l)ri(lge" of small-celle i a i 0, H o 1 Pauicum amarum X X X X X X X X X X X X X X X X X X X X X X X X X X x X X Muhlenbergia tilipes Spartina patens Spartina stricta^ X Chloris petraea X X Uniola paniculata X X X X Yucca aloif olia X X Yucca gloriosa Myrica carolinensis X X X X X X X X X My rica cerif era Quercus virginiana X X Zanthoxylum clava-herculis X Croton maritimus ± Ilex vomitoria X X X X Oenothera humif usa Teucrium nashii ± X Physalis viscosa X Epide rmis. Stomata. Species. i OQ 1 > 1 "a 1 a a s. I a t a 1 si I i n .11 Panicum amarum X X X X X X X X X X X X X X X Muhlenbergia filipes Spartina patens Spartina stricta X Chloris petraea X X Uniola paniculata X X X X Yucca aloifolia X X Yucca gloriosa X X X Myrica carolinensis X X X X X X X X Myrica cerifera. Quercus virginiana.. Zanthoxylum clava-herculis Croton maritimus X X Ilex vomitoria X X Oenothera humifusa X X X X X Teucrium nashii X X Physalis viscosa X 1 1 1 Belongs to the Salt Marsh, but is inserted here for convenience of comparison with other Gramiueae. 300 THE PLANT COVERING OF OCRACOKE ISLAND. Leaf anatomy of sand-strand species — Continued. Epidermis. Hypoder- mal colleu- chyma or collencby- matic tissue. Hairs. Species. r in 1- 1 3 6 a 1 1 1 111 II 2 1 T*nnir>mTi amaTiTm Mulilenbergia filipes . . . X X X X X X OViloritj ■nptrflPfl X X X Viirr-n nlnifnlia 1 Myrica carolinensis Myrica cerifera X X X X X X X X X ^( X X X X X X X Zanthoxylum clava- herculis X X X X X X X X X X X X TIptt vnmitoria X X X X X X X X X Tf^nnvinm TintiViii X Physalis viscosa X Stereome. Chlorenchyma. Water par- enchyma. Mestome bundles. Species. 1 1 1 i 1 a q-l 1 a o tn a^ ^§ .a-Q :o < § Oi a 1 1 s f il ii Is il r il ill 111 IP III 1 .a=^ a . ®| Q i 2 0) 1 g X X X X X X X X X X X X X X X X X X X X X X X X X Muhlenbergia fllipes . . . Spartina patens Spartina stricta Chloris petraea . Uniola paniculata Yucca aloif olia X X X X X X X _ X X X X X X X X X X X X X X X X X Mvrica carolinensis X X X X X X X X X X X X X X Zanthoxylum clava- herculis Ilex vomitoria X X Teucrium nashii X V + ! V ANATOMY OF TRIGLOCHIN AND JUNCUS. 301 SALT MARSH SPECIES. TRIGLOCHIN STRIATA Ruiz tfc PaV. iea/ isolaterul, thickish. Epidermis cells with noimndulMte walls, the? outer strongly lliick- ened; cuticle thick, granular; stoniata in rows parallel to the nerves, level with the surface, each bordered by 4 epidermal cells, of which 2 are subsidiary and resemble the guard cells; hairs ncjiie. Stereome none. Chlorenchyma: Two outer layers compact, continftous on l)oth sur- faces, not imlisadic excei)t at the leaf margins, where o layers of i)ali- sade occnr; parenchyma of the interior of the leaf containing little chlorophyll, interrnpted by lacunes. Mestome hundles imbedded in the interioi- x^arenchyma, each sur- rounded by a small-celled mestome sheath, whose inner walls are excessively thickened and layered ; this surrounded by a sheath of large-celled, colorless parenchj^ma. Spartina stricta (Ait.) Roth. Treated for comparison among sand-strand grasses, page 289. JuNCUS ROEMERIANUS Scheele. J/er// vertical, terete, sharp-pointed, stem-like. Epidermis cells all small, quadrangular (superficially), regular, without alternation of long and short cells; smaller and thicker- walled over the bands of chlorenchyma than over those of subepidermal stereome, the outer walls much thickened and porous; stomata^ with guard cells level with the oilier epidermal cells; hairs none. Stereome (subepidermal) alternating with the chlorenchyma in strong groups, which in cross section are I-shaped.'^ Cldorencliyma of typical long, narrow palisade cells, mostl}" in 5 or 6 layers. Mestome hundles arranged in several concentric circles, com- pletely surrounded hy stereome (which is particularly strong on thc^ two sides parallel to the leaf surface), the whole enveloi^ed by a beautifully i-egular, large-celled parenchyma sheath. Within the stereome the bundle is encircled by a mestome sheath of small, thick walled* cells. The outer mestome bundles, with the colorless pareii- ch3"ma between, form a continuous ring, unbroken by lacunes. The inner bundles lie in tliin longitudinal plates of parenchyma, wliich separate large lacunes. Small bundles of stereome, each surrounded by a i)arencli3nna sheath, also occur in tlie interior of the leaf. Stem differing but little from the leaf; difference consisting cliiefly in the presence of a cortex of some thickness, and in llie less elon- gated chlorenchyma cells. 'Of the type common in Jnncaceae, Cyperaceae, and Gramineae. 2 '* I-formige Trager "' of fecliweudener. 302 THE PLANT COVERING OF OCRACOKE ISLAND. Sesuvium maritimum (Walt.) B.S.P.^ Z/ea/ isolateral, somewhat succulent. Epidermis cells with non undulate, radial walls, the outer some- what thickened, some of the cells much larger and probably serving for water storage; cuticle smooth; stomata Ij^ing in all directions, guard cells level with the epidermis, each stoma bordered by 3 to (usually 4 or 5) undifferentiated epidermis cells; hairs none. Stereome none. Chlorenchyma homogeneous and occupying the entire thickness of the leaf, interrupted by large intercellular spaces, which lie beneath the large (water- storage) epidermal cells. Mestome bundles with a small group of collenchyma on the leptome side. Stein: Epidermis with cell walls, especially the outer, strongly thickened. Stereome none. Collenchyma in small groups above the leptome of the primary mestome bundles. Cells containing crystal masses in the pith and a few in the cortex. TissA MARINA (L.) Britton.^ Leaf isolateral, hemicylindric, furrowed, margins sparsely ciliate, especially toward base. Epidermis with cells somewhat elongated parallel to the leaf axis, the radial walls strongly undulate, the outer walls slightly thickened; stomata always parallel to the leaf axis, guard cells slightly prominent, lying usu- ally between 2 ordinary epidermis cells and at right angles to their dividing wall, but sometimes bordered b}^ 3 cells; hairs (on the margins) glandular (fig. 46), capitate, with a 3 or 4 celled stalk. FIG. m.-Tissa mar- Stereome none. ^■na— glandular hair CMorenchyma compact, its cells not elongated. Scale 240^ margin. Colovless parenchyma (water tissue) constituting the interior mesophyll. MesUyme bundle of the midvein small, lying deep in the water tissue, with a small group of collench3ana outside the leptome. Stem: Epidermis with thick outer cell walls and wrinkled cuticle. Outer cortex separated from the inner by an unbroken, 2-la3^ered ring of stereome, with cell walls (especially of the inner layer) compara- tively thin. ^ Sesuvium pentandr} nil Ell. — Compare Warming's description and figure of ^. portulacastrum, Halofj^t Studier. pp. 180, 211. ■^ Spergularia salina J. and C. Presl. ANATOMY OF VINCETOXICLM PALUSTRE. 303 KOSTELETZKYA VIRGINIC'A (L.) A. (4r{iy. Ledfhi'Oixd and flat, bifacial, stellate-pubescent on l)(>th surfaces. Ejjide/Diis cells with iioiiundulate, thin walls, except above and beh)\v the larger veins, wliere the cuticle is rather thick and layered; stomata witli guard cells sliglitly proiiiin(^nt, more numerous on tlie dorsal surface; hairs stellate, consisting of 5 to 8 acute unicellular arms with thick, smooth cuticle, separate nearly or quite to the l)ase, each from a narrow foot cell in the epidermal plane. Hypoderrtial colleiichyma strongly developed above and below the larger veins. Chlorerichyriia: Palisade 1-layered; pneumatic tissue with numer- ous small intercellular spaces; mucilage cavities distribut(Ml in the chlorenchyma. Mestome bundles almost completely surrounded by a thin, inter- rupted sheath of stereome, which is most strongly developed outside the leptome. Ammania koehnei Britton. Leaf ^at, rather thin, aijproximately isolateral. Epidermis: Cells with radial walls strongl}^ undulate ; all the walls thin, except above and below the larger veins, where the outer walls are considerably thickened; cuticle smooth; hairs none; stomata chiefly parallel with the veins, but some irregular; guard cells slightly prominent, each stoma bordered by usually 4 undifferentiated epi- dermal cells. Collencliyma none. Stereome none. Chlorenchyma homogeneous, not imlisadic. ViNCETOXicUM PALUSTRE (Pursh) .\. Gray.^ Leaves narrow, sharply reflexed and hanging almost vertically, imperfectly isolateral. Epidermis: Cell walls rather thick, not undulate; cuticle wrinkled, especially above and below the veins; stomata more numerous on the ventral surface, level with the epidermis, each bordered by 4 or (more often) 5 ordinary epidermis cells, generally parallel with the leaf axis on the ventral surface, very irregularly disposed, often at right angles to the axis on the dorsal surface; hairs none. Hypoderni a single, narrow layer, only above the midrib. Collenchyma none. Stereome none. Chlorenchyma not palisadic, homogeneous through IIh' l«'af. bnl the interior containing less chlorophyll. Cells contain iiKj masses of crystals (calcium oxalate) scattcicd in the chlorenchj^ma. Stem: Epidermis as in the leaf. ' Seutera inaritima Decsne. 304 THE PLANT COVERING OF OCRACOKE ISLAND. Hypoderm continuous, 1-Ui3'ered. Outer cortex with rather thick- walled cells, containing chlorophyll; inner cortex gradually becoming thinner- walled and colorless. Stereome in a concentric band of isolated groups, lying Inside the middle of the cortex. Lactiferous ducts few, Ijang just outside the mestome bundles. Mestows hundles bicoUateral, perileptomatic, the leptome most strongly developed on the outer l^eriphery of the hadrome. LiPPIA NODIFLORA Mx. Leaf^ imperfectly bifacial, usu- ally horizontal, but sometimes vertical. Epidermis alike on both sur- faces, cell walls thick, not undu- late; cuticle wrinkled; stomata (fig. 47) lying in all directions, guard cells almost level with the ventral surface, slightly depressed on the dorsal surface, each stoma bordered by 2 crescent-shaped, chlorophyll - holding, subsidiary cells which are usually at right angles to but often nearly or quite parallel to the guard cells, and of which one is usuallj^ considerably larger than the other; hairs abun- dant on both faces, iDarallel to the veins, appressed, lying in slight grooves of the epidermis, each attached b}^ its middle (hence 2-armed) to a short cylindrical foot cell, which is bordered by several wedge- shaped (as seen from above) radiallj^ arranged epidermis cells, the free cell with a very thick, warty cuticle. Hypodermal collenchynla (not very typical), in 1 or 2 layers above and 3 or 4 below the principal veins, intermitting the chlorenchyma in full-grown leaves. Chlorencliyma: Palisade 2-layered, the cells rather short; pneu- matic tissue rather compact, not well differentiated from the palisade, but its cells more nearly isodiametric and containing less chlorophyll. Mestome hundles (of larger veins), with some stereome below the leptome and a small group of collenchj^ma above the hadrome, which finall}^ becomes continuous with the subepidermal group of col- lenchj^ma. Fig. 47.—Li2ypia nodiflora— stomata and hairs, a, Stomata on leaf; t», hair and stoma on ventral leaf surface; c, hair on dorsal surface. Scale 240. ' Compare Warming. Halofyt-Studier, p. 3oo, and Solereder, Syst. Anat.,p. 713, ANATOMY OF MONNIERA AND SOLIDAGO. 305 MONNIERA MONNIERA (L.) BRITTOX.' Occurs in 2 forms; one in shallow pools, largely submersed, willi long stems, elongatcnl internodes, and larger loaves; the other terres- trial, in wet sand, with short, creeping stems, contracted internodes and smaller leaves. (a) Aquatic form. Structure that of a partially submersed hydro- phyte, with thin- walled tissues, much reduced mestome system, no mechanical tissue, etc. Leaf isolateral. Epidermis: Cells with undulate lateral walls, the walls thin except the outer, which is somewhat thickened; cuticle delicately wrinkled; stomata more numerous on the dorsal surface, guard cells about level with the epidermis, bordered by 2 to 4 ordinary epidermal cells; hairs none. Chlorenchynia homogeneous, palisade none. Mestome bundles immediately bordered by chlorenchyma, not rein- forced by stereome or collenchyma. Stem: Epidermis as in the leaf. Cortical parenchyma in 1 or 2 continuous layers just beneath the epidermis and. around the central cylinder, elsewhere in 1-layered plates, separating the large lacunes. Mestome cylinder composed of several bundles, inclosing a small quantity of pith. (6) Terrestrial form. The only tangible differences from the aquatic form are: Stomata about equally numerous on both leaf surfaces; mestome bundles somewhat more developed and walls of the vessels more lignified; mesophyll somewhat more compact. Solid AGO sempervirens L.^ Leaf somewhat fleshy, vertical or nearly so, apjjroximately isolat- eral. Epidermis: Cells with nonundulate radial walls, only the outer strongly thickened, except above and below the larger veins; cuticle strongly wrinkled; stomata numerous on both faces with guard cells level with the surface, bordered by usually 4 ordinary epidermal cells; hairs none. Hypodermal collenchyma in only 1 or 2 narrow layers above and 3 or 4 wide layers below the larger veins. CJdorenchyma homogeneous, none of it typical palisade, frequently interrupted, especially opposite the mestome bundles, b}' plates of colorless, thin- walled parenchyma (water tissue), which extend froni the ventral to the dorsal epidermis, and ultimately break down into large lacunes close beneath the epidermis. ^ Herpestis mouuiera H. B. K. Th( 2965- 306 THE PLANT COVERING OF OCRACOKE ISLAND. Ducts (probablj^ resiniferous) numerous, especially near the dorsal surface, a^iparently always Ij^ing in the lilates of Avater tissue, one below the leptome of the mid vein. Mestome bundles of the larger veins with a narrow (in transA'erse section crescent-shaped) group of comparatively thin- walled stereome above the hadrome.^ Aster tenuifolius L. Leaves narrow, almost vertical, isolateral, thick, with a deep groove on the dorsal surface on each side of the midvein, margins slightly incurved. Epidermis: Cells comi)aratively large, walls not undulate, the outer greatly thickened; cuticle wrinkled and with slight furrows corre- sponding to the radial walls of the epidermal cells ; stomata rather few and large, the guard cells slightly sunken, mostly somewhat deflected in direction from that of the leaf axis, bordered by usually 3 ordinary epidermis cells; hairs none. ♦ Hypodermal collenchyma in a few narrow layers above and rather wide layers below the midvein. CMorenchyma consisting of palisade with high, narrow cells, in about 2 layers on both faces, strongly converging toward the mid- vein, especially on the ventral side. Colorless parenchyma (water- storage tissue) occupying the interior of the leaf in small quantity, and surrounding the midvein, where it replaces the palisade. Mestome bundles not reinforced by stereome. Aster subulatus Michx. Leaves wider and thinner than in the preceding, almost vertical, isolateral, flat, impressed above the midvein, which below is i^romi- nent, with a furroA^^ on each side of it. Epidermis: Cell Avails not undulate, thick, the outer A^er}^ thick, the inner collenchymatic-thickened A\^here hypodermal collenchyma occurs; cuticle wrinkled; stomata, with guard cells lying parallel to the leaf axis, level Avith the surface; hairs none. Hypodermal collencliyma above and below the A^eins (about 4 laj^ers betAveen the leptome of the midA^ein and the dorsal epidermis) and in the marginal angles. CMorenchyma, of compact palisade, occupying i^ractically the entire thickness of the leaf except Avhere collenchyma occurs and about the midA^ein. 'The leaves of nonmaritime species of Solidago (e. g., S. petiolaris, S. neglecta, and S. erecta) exhibit some interesting differences from S. sempervirens. All three have bifacial leaves with compact palisade and open pneumatic tissue (chloren- chyma least differentiated in S. petiolaris). Stomata few {S. erecta, S. neglecta) or none {S. petiolaris) on the ventral surface, guard cells slightly prominent on the dorsal surface. Hairs along the veins, especially on the dorsal face in S. petio- laris, 3 or 4 celled sharp-pointed, bent. ANATOMY OF BACCHARIS HALIMIFOLIA. 307 Colorless parejicliynia (water-stonige tissue) above and on each side of the mid vein. Mestome bundles without stereome supports, but with a small irreg- ular group of collenehynia lying outside the hadrome.^ BaCCHARIS HALIMIFOLIA L, Leaves thickish, nearly vertical, isolateral. Epidermis: Cell walls not undulate, thickened, the outer ones greatly so; cuticle warty, especiall}^ on the dorsal surface; stomata mostly parallel to the veins, but many somewhat deflected, guard cells slightly prominent, each stoma radially bordered by 4 or o small epidermis cells. Colleyicliyma (hypodermal) replacing chlorenchyma above and below the larger veins (0 or 7 layers below the leptome of the midvein), containing no ducts. ^ Chlorenchyma: Palisade occupying the whole thickness of the leaf between the veins, rather open, especiall}^ that in the interior of the leaf (but typical pneumatic tissue none), converging toward the midvein on the dorsal side; large, deep air chambers underneath the stomata. Colorless parenchyma (water tissue) in 2 layers on each side of the midvein (cells circular in cross section), in a single layer entirely sur- rounding the smaller bundles. ' Three nonmaritime species of Aster were selected for comparison with the two salt-marsh species: A. puniceuH, a broad-leaved plant of boggy ground, and .1. dumosus and A. ericoides, narrow-leaved species of dry, sandy soil. A. ericoides has a practically isolateral leaf, epidermis alike on both faces, with undulate radial and thickened outer walls, finely wrinkled cuticle, guard cells of the stomata level with the ventral surface, slightly prominent on the dorsal sur- face; chlorenchyma near both surfaces compact and small-celled, more open and larger-celled in the interior of the leaf; hypodermal collenchyma in '2 layers above and below the midvein; water parenchyma none. ^4. dumosus has a distinctly bifacial leaf, epidermis much as in .1. ericoides, but the 2 surfaces more differentiated, the ventral with radial cell walls less undulate and outer walls less thickened than in ^4. ericoides, cells larger and stomata much fewer on the ventral surface, the dorsal with radial walls more strongly undu- late, and scattered, slender, pointed, few-celled hairs along the veins: ])alisade com- pact, pneumatic tissue open: veins supported by hypodermal collenchymatic tissue. A. puniceus shows, of course, the greatest amount of difference from the salt- marsh forms. It has a flat, approximately horizontal, bifacial leaf. The ventral surface is rough with thick- walled, prickle-like, 1-celled hairs, mixed ^vith scat- tered, longer, more slender, and thinner-walled hairs: the stomata lie in all direc- tions in and have their guard cells level with the dorsal surface, but are wanting on the ventral face: the cuticle is smooth; the chlorenchyma is differentiatealisade on tlie dorsal side and extending to the epidermis. Ducts (on the ventral side) frequent just beneath these extensions. Mestome bundles of the veins (fig. 49) lying deep in the water-storage tissue; reinforced on the leptome side b}' a strong group of very thick- walled stereome, on the hadroine side by a smaller group; leptome and its elements beautifully differentiated, the sieve tubes each witli water-storage tissue in the interior of the leaf and the absence of hairs— just the converse of what one would expect as the differential characters between a dune and a salt-marsh species. ' The apical cells are easily broken off, so that in older leaves the covering appears to consist of rounded, usually biceliular papillae. 310 THE PLANT COVERING OF OCRACOKE ISLAND. a companion cell and a band of four or five cribrile parenchyma cells. 1 Leaf anatomy of salt-marsh species. [The sign x indicates presence of character; ± Its imperf ect development.] Leaf. Epidermis. Cuticle. Ul Species. i t 2 1 -2 Relatively thick. Thick. 1 ■S H it X X ■ X X X X X X X Titjcifl marina X X Kosteletzkya virginica X ± Vincetoxicum palustre X X X X X X X X X Lippia nodiflora ± X I X X X ± Iva frutescens X X X X X X X X Aster tenuifollus Baccharis halimifolia X X X Characters given under species of the "sand strand," page 1 Borrichia arhorescens (compare Warming, Halofyt-Studier, p. 212) is a very- similar but larger plant of the tropical American strand. It differs from B. frutes- cens in the following particulars, the characters being taken from material col- lected in South Florida and Porto Rico: Hairs much thicker-walled, entirely disappearing in old (more than 1 year old?) leaves; stomata on both surfaces, with guard cells slightly prominent on the ventral face, less numerous and with guard cells slightly sunken on the dorsal face; epidermal cell walls, especially the outer, thick; palisade interrupted both above and below by extensions of the water-storage tissue, which on the ventral side ultimately disorganize and form large lacunes; hypodermal coUenchyma occurring where the palisade is interrupted on the ventral side; coUenchyma taking the place of stereome as supports of the veins, especially strong on the lep- tome side. From Warming's description and figure of B. arhorescens my specimens showed important differences: (1) The presence of hairs (elsewhere in the same paper Warming mentions their occurrence in this species) ; (2) stomata with guard cells slightly prominent on the ventral surface (Warming writes "stomata sunken""); (3) coUenchyma present and strongly developed; (4) mestome bundles in three planes (one according to Warming) , some small ones being situated near the upper and the lower epidermis, while the midvein is central in the water-storage tissue. ANATOMICAL SUMMARY OF SALT-MAKSH SPECIES. 311 Leaf anatomy of salt-inarsh .s^«'c/V.s — ( ontiuned. [The sign x indicates presence of character; ± its imperfect development.] . Epidermis. Stomata. Species. 1 1 • •if 1 1 . ^1 cc ^ . 1 i 1 . ■>-' Cfi i •a ! u 1 Triglochin striata X X X X Spartina stricta ' J uncus roemerianus . X X X i X Tissa marina X X X X Kosteletzkya virginica X X X X X X X X X X Ammania Ivoehuei ± Vincetoxicum palustre . . . X Lipi)ia nodiflora -.. ± X Monniera monniera X Iva f rutescens - - X X Solidago sempervirens X Aster tenuif olius X X i Aster subulatus. X Baccharis halimifolia X Borrichia f rutescens X Epidermis. Hypoder- mal collen chyma or collenchy- matic tissue. Hairs. Species. eg U Is f 1 1 1 IS 1 cc c 1 i "O U o 3 1 la a O 2 Triglochin striata Spartina stricta ' Juncus roemerianus . . Sesuvium maritimum. . 1 Tissa marina X X X X Kosteletzkya virginica >^' X X Ammania koehnei- . Vincetoxicum palustre Lippia nodiflora X X X X Monniera monniera Iva f rutescens... X X X X X X X Solidago sempervirens Aster tenuifolius Aster subulatus Baccharis halimifolia .. X Borrichia frutescens. . . X X X X ■ 1 ^ 1 1 Characters given under sjiecies of tlio "sand strand." page 312 THE PLANT COVERING OF OCKACOKE ISLAND. Leaf anatomy of salt-marsh spec/'e.s— Continued, ♦ [The si^a x indicates presence of character; ± its imperfect development.] Stereome. Water Chlorenchyma. paren- chyma. Mestome bundles. Species. 1 1 05 1 . t I o W t (D 4i H ll II be .S II 1 it 5 . a® 1 2 03 ft"' X X 1 X Sioartina stricta^ Juncus roemerianais... X X X X X X X X X X X X X X X X X Kosteletzkya virginica. X X X Vincetoxicum palustre X ± X X X X X X X X Solidago sempervirens. X X X X X X X X X X X X 1 1 Characters given under species of the "sand strand," p. 389. GEOGRAPHICAL AFFINITIES OF THE FLORA. According to its geographic position, Ocracoke Island lies well within the Anstro riparian area of the Lower Austral life zone in North America.^ For two reasons, however, this relationship of its flora is somewhat obscured: (1) By the large proportion of strand species, many of which have a very extensive geographic range; and (2) by the absence of many of the most characteristic species of the Austro- riparian area, due to the peculiar physical environment. Of the total number of species of embryophytes (about 135) collected or observed upon Ocracoke Island, between one-fourth and one-third may be designated as maritime, i. e., normally occurring only in the salt marshes or on the sand strand bordering the ocean. These may be segregated into 4 groups, according to geographical range : 1. Species occurring also on the coasts of tropical America. A prefixed asterisk (*) indicates that the species does not extend north of the mouth of Chesapeake Bay; a prefixed dagger (f) that the northern limit is in North Carolina, probably not far from Ocra- coke. Triglochin striata and Monniera monniera extend north to eastern Maryland. 'Merriam, Geogr. Distrib. p. 211: Life Zones p. 45, map. GEOGRAPHICAL AFFINITIES OF THE FLORA. 313 Triglochin striata R. & P. \ Yucca aloifolia L. *Qaercus vir-ginianaLi.^ * Physalis viacosa ^L. \Chloris petraea Sw. Monniera monniera H, B. K. * Uniola xKinicuUda L. *Borrichia frutescena L. ^Fimbristylis spadicea Vahl. \Ipomoea sagittata Cav. 2. Species mostly or entirely confined to the seacoast of the Austro- riparian area: Zdidhoxyluni dava-lievculis and, X)ossibly, Ilex roini- toria extend northward to Virginia, while the rest attain their northern limit in North Carolina. Miihlenbergia filipes M. A. Curtis. Ilex vomitoria Ait. Yucca gloriosa L. Opuntia pes-corvi Le Conte. Croton maritimus Walt. Vincetoxicum palustre (Pursh) A. Gray. Zanthoocylum clava-herculis L. 3. Species confined to the Atlantic seacoast of North America and ranging north of the Austroriparian area. The northern limit of each is cited as given in Britton & Brown's Illustrated Flora. Panicum amarum minus Vasey & Oenothera humifusa Nutt. (New Jer- Scribn. (Connecticut). sey). Spartina patens (Ait.) Muhl. (Nova Limonium earolinianum (Muhl.) Brit- Scotia), ton (Labrador). Distichlis spicata (L. ) Greene - (Maine) . Iva frutescens L. (Massachusetts) . Juncus roemerianus Scheele (New Jer- Solidago sempervirens L. (New Bruns- sey). wick). Sesuvium maritimum (Walt.) B. S. P. Aster tenuifolius h. (Massachusetts). (New York). Aster siibidat us Michx. (New Hamp- Euphorbia polygonifolia L. (Rhode shire). Island). Baccharis halimifolia L. (Massachu- Kosteletzkya virginica L. (New York). setts). Ammania fcoe/mei Britton (New Jersey). 4. Species occurring also on the seacoast of the northern hemisphere in the Old World. Spartina stricta (Ait. ) Roth. Salsola kali L. Atriplex hastata Ij. Tissa marina {Ij.) Britton. Salicornia herbacea L. Of the nonmaritime species of the island, fifteen are introduced and are chiefiy weeds of American origin. The remainder (about two-thirds of the total flora) includes several mainly tropical species, such as Lippia nodiflora Michx., Centella asiatica (L.) Urban, Parietn- ria deb His For St., and Tillandsla tts?ieoidesL., which, while hardly mari- time, are found usually near the seacoast in the Austrorix)arian area. Finally, after excluding all the preceding categories except the second of strand plants, we have a list of species among which the Austro- riparian element is sufficiently predominant to leave no question as to the general affinity of the flora. As previously remarked, however, many of the plants most cliar- ' Normally a strand plant in Virgfinia and North Carolina. -The typical form. 314 THE PLANT COVERING OF OCKACOKE ISLAND. acteristic of the whole Austroriparian area, and abundant on the mainland, scarcely 30 kilometers distant, are wanting upon Ocracoke Island. Notable among these absentees are the pines {Pin uspalustris^ P. taeda), the gums (Xyssa spp.), the bald cypress {Taxodiuin dis- tichum), the deciduous oaks, the cane (Arundinaria macrosperma), species of Erianthus, Carex verrucosa, Smilax laurifolla, and Bei^- chemia scandens. Hardly less striking is the nonoccurrence of most of the bright- flowered herbs that abound in the pine forests on the west shore of Pamlico Sound. Such are species of Coreopsis, Helianthus, Lacinaria (Liatris), Eupatorium, Solidago, Rhexia, Gerardia, H3^i3er- icum, Sarracenia, Habenaria, and Polygala. The unfavorable environ- ment is doubtless responsible for the absence of many of these plants, conditions ui)on the island being suitable only to tlie hardiest species. Scarcity of shade, of humus, and of fresh water accounts in like man- ner for the poverty of the flora in most of the lower forms, such as fresh-water algae, fungi, hepaticae, mosses, and ferns. The numerous arrangements b}^ which many of the higher plants are protected against excessive loss of water maj^ also serve in some measure for protection against parasitic leaf fungi, and may partly account for the com- parative scarcity of the latter. The general aspect of the j)lant covering is not attractive. Bright green foliage and flowers of brilliant coloring are too scarce to make much impression, while, except in the salt marshes, the plants are usually so scattered that it is the soil which gives tone to the land- scape. Furthermore, the trees and shrubs are mostly characterized by gnarled trunks, many dead branches, and ragged foliage, as a result of exposure to sand-laden winds. Altogether, the picture is one of somber monotony. LIST OF PLANTS COLLECTED AND OBSERVED. [The prefixed asterisk denotes that the plant is introduced.] LICHENES. Usnea barbata L. Ramalina tnontagnei De Not. MUSCI. Bryum argenteum L. Rhynchostegium serrulatum Hedw. POLYPODIACEAE. Aspleniuin platyneuron (L.) Oakes. {A. ebeneumA.it.) PINACEAE. Juniper us virginiana L. TYPHACEAE. Typha latifolia L. SCHEUCHZERIACEAE, Triglochin striata Ruiz & Pav. LIST OF SPECIES. 315 POACEAE. Aridrojjogou glomeratus (Walt.) B. S. P. (A. laacronriis Michx. ; Paspalum ciliatifoUmn Michx. PaHpalam distichum L. Paspalum laeve JNlichx. Syntlierisviafiinbriata (Smith) Nash. (Digitaria Jivihr'tafa Smith.) PauicKiii ainarum minus Vasey & Scribner. Pauicuiii lattuginosum Ell. (?) Panicuiu laxijlorum Lam. Panicum neuranthum Griseb. Panic um walteri Pursh. OjjI is menus setarius (Lam.) Roem. & Schult. Chaetochloa imherbis pereiinis (Hall) Scribn. & Merrill. (C. versicolor Bicknell.) Homalocenchrus virginicus (Willd.) Britton. ( Leers ia virginica Willd.) MuhlenhcrgiafilijjesM. A. Curtis. "^Sporobolus indicus (L.) R. Br. *Capriola dactylon (L.) Kuntze. {Cynodon dacftjlonPeia.) Spartina patens {Ait.) Muhl. {S. jancea'EAl.) Spartina stricta (Ait.) Roth. Chloris p>etraea Sw. *Eleusine indica (L.) Gaertn. Triplasis purpurea (Walt.) Chapm. Eragrostis nitida (Ell.) Chapm. Uniola laxa (L.) B. S. P. {U. gracilis Michx.) Uniola paniculata L. Distichlis spicata (L.) Greene. (D. maritima Raf.) CYPERACEAE. Cyperus cylindricus (Ell.) Britton. (C. torreyi Britton.) Cyperus echinatus (Ell.) Wood. (C haldwinii Torr.) Cyperus nuttallii Eddy. Cyperus speciosus Vahl. Eleocliaris sp. Dickromena colorata (L.) A. S. Hitchcock. (7). leucocephala Michx.) Fimbristylis spadicea (L.) Vahl. Scir2)us americanus Pers. {S. pungens Vahl.) Scltria verticillata Muhl. Cladium effusiwi Torr. ARACEAE. Acorus calamus L. Tillandsia usyieoides L. BROMELIACEAE. JUNCACEAE. Juncus dichotomus Ell. Juncus roeinerianus Scheele. Juncus scirpoides Lam. LILIACEAE. Yucca aloi folia L. Yucca gloriosa L. SMILACEAE. Smilax bona-no,v h. (S. tamnoidoi A. Gray.) 31(J THE PLANT COVERING OF OCRACOKE ISLAND. MYRICACEAE. Myrica ca^'olinensis Mill. Myrica cerifera L. FAGACEAE. Quercus virginiana L. {Q. virens Ait.) MORACEAE. * Ficus carica L. * Brousso7ietia pajyyrifera (L.) Vent. URTICACEAE. Parietaria debilis Forst. POLYGONACEAE. Polygonum punctatum Ell. Rumex sp. CHENOPODIACEAE. * Chenopodium anthelminticum L. Atriplex hastata L. Salicornia herbacea L. Salsola kali L. PHYTOLACCACEAE. Phytolacca decandra L. AIZOACEAE. Sesuvium maritimiim (Walt.) B. S. P. {S. pentandrum Ell.) Mollugo verticillata L. ALSINACEAE. Tissa marina (L.) Britton. (Spergularia salina J. & C. Presl.) ROSACEAE. Ruhus trivialis Michx. CAESALPINACEAE. * Cassia occidentalis L. VICIACEAE. Aeschynomene virginica (L.) B. S. P. {A. Iiispida Willd.) Meihomia paniculata (L.) Kuntze. (Desmodium paniculatum DC) Oalactia volubilis (L.) Britton. {G. pilosa Ell.) LINACEAE. Linum medium (Planch. ) Britton. RUTACEAE. Zanthoxylum clava-hercidis L. EUPHORBIACEAE. Croton maritimus Walt. Acalypha gracilens A. Gray. Euphorbia polygonifolia L. ANACARDIACEAE. Rhus radicans L. LIST OF SPECIES. 317 ILICACEAE. Ilex glabra (L. ) A. Gray. Ilex opaca Ait. Ilex vomitoria Ait. (/. cassine Walt.) VITACEAE. Vitis aestivalis Michx. MALVACEAE. Kosteletzky a virgin! ca (L. ) A. GJ-ray. Hibiscus moscheutos L. * Gossypium herhaceurn L. HYPERICACEAE. Ascyrum hypericoides L. CISTACEAE. Lechea villosa EW. {L. major Michx.) CACTACEAE. Opuntia pes-corvi Le Conte. LYTHRACEAE. Ammania koehnei Britt. ONAGRACEAE. Ludwigia alata Ell. Ludwigia microcarpa Michx. Oenothera huinifusa Nutt. APIACEAE. Sanicula sp. Hydrocotyle umbellata, L. Centella asiaticc (L.) Urban. PRIMULACEAE. Samolus florihundus H. B. K. PLUMBAGINACEAE. Limonium carolinianum (Walt.) Britton. {Statice limonium var. carolini- aniun A. Gray. ) LOGANIACEAE. Cynoctonum mwreola (L. ) Britton. {Mitreola petiolata Torr. & Gr.) Polypremum procumbens L. ASCLEPIADACEAE. Vincetoxicum palustre (Pursh) A. Gray. {Seiitera maritima Decne.) CONVOLVULACEAE. Ipomoea sagittata Cav. VERBENACEAE, Lippia nodiflora Michx. Callicarpa americana L. 61 ri THE PLANT COVEKING OF OCRACOKE ISLAND. NEPETACEAE. Teucrimn nashii Kearney. Monarda punctata L. SOLANACEAE. Physalis viscosa L. Solanum caroUnense L. * Solarium nigrum L. . * Lycopersicum esculentum L. * Datura tatula L. SCROPHULARIACEAE. *Verbascum thapsusJj. Monniera monniera (L. ) Britton. {Herpestis monniera H. B. K.) Gerardia maritima Raf . RUBIACEAE. Oldenlandia uniflora L. (O. glomerata Michx.) Diodia teres Walt. Diodia virginiana L. Galium sp. (probably G. tinctorium L. or G. claytoni Michx.). CUCURBITACEAE. * Citrullus vulgaris Schrad. Melothria pendula L. CICHORIACEAE. Hier actum gronovii L. CARDUACEAE. Elephantopus nudatus A. Gray. Mikania scaudeiis (L.) Willd. SoUdago sempervirens L. Euthamia caroliniana (L.) Greene. {SoUdago tenuifolia Pursh.) Aster salicifolius Lam. var. Aster subidatus Michx. Aster tenuifoliris L. Erigeron canadensis L. Baccharis halimifolia L. Pluchea camphorata (h.) DC. Phichea foetida (L.) B. S. P. (P. bifrons DC.) Gnaphalium purpureum L. Ambrosia artemisiaefolia L. Iva frutescens L. Xanthium sp. Xantliium sp. Borrichia frutescens L. ^Bidens bipinnata L. Ereclitites liieracifolia (L.) Raf. Carduus spinosissimus Walt. {Cnicus horridulus Pursh.) Library N. estate College WORKS REFERRED TO. 319 BIBLIOGRAPHY. Britton, N. L., and Brown, A. Illustrated Flora of the northern United States, Canada, and the British possessions. 181)0 to 189b. Contejean, C. Geo^raphie Botaniqiie. . 1881. Diels, L. Stoffwechsel und Structur der Halophyten. Jahrbiicher fiir wissen- schaf tliche Botanik. 23 : J309 to 322. 1898. Duval-Jouve, M. J. 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