ELEMENTARY BOTANY

BY

GEORGE FRANCIS ATKINSON, PH.B.

Professor of Botany in Cornell University

NEW YORK
HENRY HOLT AND COMPANY

1898

Copyright, 1898,

BY

HENRY HOLT & CO.

ROBERT DRUMMOND, PRINTER, NEW YORK.

PREFACE.

UNTIL recent years the prevalent method of teaching botany
in the secondary schools, and in the first courses in many col-
leges, has been based on the "analysis" of flowers. The
method had its impetus in the study of systematic botany pur-
sued with such vigor by the pioneers of the science in America.
The great progress in our knowledge of the morphology and
physiology of plants during the last quarter of this century has
changed the whole problem of elementary instruction in botany,
and led to almost universal dissatisfaction with the old method
of secondary instruction in this subject. It is now generally
recognized that a study of the lower plants, like the algae, fungi,
liverworts, mosses, and ferns should form a part of a course of
secondary education in botany.

To meet this end a number of books have sprung into exist-
ence during the past few years. If the need for some guid-
ance in the selection of topics, and an outline of the character
of the study, could be met by number alone of books, this want
would be fully met in the new treatises recently published, and
there would be no place for the present book. But a judicious
selection of a few forms to illustrate function, process, and
relationship throughout the wide range of plant life, and the
training in logical methods of induction, and accuracy of draw-
ing conclusions, is vastly more important in its influence on
the character of the pupil, even though he forget all about the
plants studied, than the handling of a great variety of objects,
and the drawing of haphazard conclusions, which are left to the
pupil in a large number of cases by the methods pursued in
many of the recent elementary works,

iii

IV PREFACE.

For several years the author has been deeply interested in the
teaching of elementary botany, and has had an opportunity to
study methods in a practical way, in having charge of the in-
struction of a large class of beginners, the majority of whom
had never studied the subject before. One of the great diffi-
culties encountered in attempting to introduce the study of the
lower plants is the fact that these plants are in most cases en-
tirely unknown to the pupil. The difficulty does not lie in the
attempt to introduce the study of unknown objects. But it lies
rather in the attempt to study the lower plants, at the outset, in
a more or less thorough manner, to learn their characters, rela-
tionships, etc., in order to group them into their natural orders.
This is attempting too much for the young beginner, to whom
these plants are totally unfamiliar objects.

The method followed in this book has been thoroughly tested
in practical work. It is to first study some of the life processes
of plants, especially those which illustrate the fundamental prin-
ciples of nutrition, assimilation, growth, and irritability. In
studying each one of these topics, plants are chosen, so far as
possible, from several of the great groups. Members of the
lower plants as well as of the higher plants are employed, in order
to show that the process is fundamentally the same in all plants.
Then another process is studied in a similar way, using so far as
possible, especially where the lower plants are concerned, the
same plant/ In this way the mind is centered on this process,
and the discovery to the pupil that it is fundamentally the same
in such widely different plants arouses a keen interest not only
in the plants themselves, but in the method which attends the
discovery of this general principle. In the study of the life
processes, the topics can be arranged so that they show progres-
sion of function.

At the same time it is well for the teacher to select for this
study of the life processes those plants which represent well the
great groups, and show gradual progression of form and struc-
ture, and also those which are easily obtained.

A second period of the session can then be devoted to study-

PREFACE. V

ing a few representatives of the different groups of the algae,
fungi, liverworts, mosses, ferns, and the higher plants. This
should be done with special reference to form, reproduction,
general classification, progression, and retrogression of parts or
organs, in passing from the lower to the higher plants. In
taking up this study of representative forms now, if a wise selec-
tion has been made in dealing with the life processes, the same
plant can be used here in most cases. These plants now are
familiar to the pupil, and the mind can be centered on form,
organs, reproduction, relationship, etc. In this study of gen-
eral morphology it is very important that a careful study be
made of some of the lower plants, and of the ferns. Here the
sexual organs are well formed, and the processes of reproduc-
tion can be more easily observed. In the higher plants the
sexual organs are very much reduced, and the processes more
difficult to observe. It is only through a study of the lower
plants that we are able to properly interpret the floral structures,
and the sexual organs of the spermatophytes, and to rid our-
selves of the erroneous conceptions which the prevalent method
of elementary instruction has fixed so firmly on the lay mind.

A third period of the elementary course may be employed in
studying special morphology of the higher plants. Even here
it seems to the author wise that the "analysis" of plants
should be deferred until after a general notion of the characters
and habit of several of the important families has been obtained.
The pupil may be told the names of the several plants used as
examples, and emphasis can be laid on ordinal and generic
characters, which can then be recognized in many plants with-
out resort to a key. The matter of determining the names of
plants by the old method can, if desired, be pursued to greater
advantage after this critical study of relationships has been made,
even though the pupil may pursue it independently at a later time.

In the study of plants one should not lose sight of the value
of observing plants in their natural surroundings. If judiciously
pursued it forms at once a means of healthful recreation, of com-
munion with the very soul of nature, and of becoming ac-

VI PREFA CE.

quainted with the haunts, the lives, the successes and failures of
plants; the influences of soil, moisture, and other environ-
mental conditions upon plants, and, what is also important, the
influence which plants exert upon their environment. Classes
may be taken into the field, at different seasons of the year, to
observe flower and bud formation, pollenation, seed production,
seed distribution, germination of seeds and nutrition of the
embryo, protection of plants against foes and extremes of
weather ; the relationships of plants in colonies, and their dis-
tribution in plant formations, etc. In all this study a knowl-
edge of some of the lower plants is important.

It is not intended that the matter in the book should be mem-
orized for the purpose of recitations. It should be used as a
guide to the practical work, and as a reference book. The para-
graphs arranged in coarse print are intended in general to indi-
cate the studies which will serve as the basis for the practical
work by the student. In most cases the material for these
studies can be quite easily obtained and the laboratory work is
not difficult. The paragraphs in fine print are intended to fur-
ther illustrate the subject by discussion and illustration of the
more difficult phases of each topic. Some of these can be made
the basis for demonstrations by the teacher before the class, and
all will serve as a convenient means of getting at the important
reference matter by the student in a single book. Suggestions
on the study and the taking of notes, etc., by the student are
given in the appendix.

Acknowledgments. — The author desires here to express his
gratefulness to his associates in the botanical department of Cor-
nell University who have read the manuscript and have made
useful suggestions (Messrs. E. J. Durand, B. M. Duggar, K. M.
Wilgand, and Professor W. W. Rowlee). Valuable suggestions
were also given by Dr. J. C. Arthur, of Purdue University, who
kindly read the chapters on physiology, and by Professor W. F.
Ganong, of Smith College, who read some of the chapters on
ecology and the tables on the homologies of the gymnosperms
and angiosperms.

PREFACE. vil

Illustrations. — The large majority of the illustrations are new,
and were made with especial reference to the method of treatment
followed in the text. Most of the photographs were made by
the author. Others were contributed by Professor P. H. Mell,
of the Alabama Polytechnic Institute, Auburn, Ala.; Professor
Rowlee, Cornell University ; Mr. H. J. Webber, Washington,
B.C.; by the New Jersey Geological Survey through the courtesy
of Mr. Gifford Pinchot, of New York ; by Mr. B. M. Duggar,
Cornell University, and Mr. Herman von Schrenk, of the Mis-
souri Botanical Garden.

Many of the drawings, especially those of microscopic objects,
were made by the author ; others by Mr. H. Hasselbring, Cor-
nell University, and Dr. Bertha Stoneman, now professor of
botany in the Huguenot College, Wellington, Cape Colony,
South Africa. The drawings to illustrate the gross characters of
plants were made by Mr. W. G. Holdsworth, Michigan Agri-
cultural College; Mr. Joseph Bridgham, Providence, R. I.;
Messrs. W, C. Furlong and W. C. Baker, Cornell University ;
and a few by Miss Edna Porter, Buffalo, N. Y., and by Mrs. E. L.
Nichols and Mrs. J. G. Needham, Cornell University. Pro-
fessor Chas. A. Davis kindly furnished the sketches from which
the drawings of the transformed trillium flower were made.

Other illustrations have been obtained from the following
sources : from the author's Study of the Biology of Ferns,
through the courtesy of the Macmillan Co.; and from the
Annals of Botany, Jahrbucher fur wissenschaftliche Botanik,
Flora, Botanical Gazette, Vines' Student's Text Book of Botany,
and Warming's Botany.

Above all the author is under great obligations to Professors
Ikeno and Hi rase, of the Imperial University of Japan, Tokio,
for their unparalleled courtesy in sending drawings of the sperma-
tozoids, and of fertilization, in cycas and gingko, in advance of
their publication.

CORNELL UNIVERSITY, June, 1898.

CONTENTS.

(References are to paragraphs.)
CHAPTER I.

PROTOPLASM.

The plant spirogyra, 4. Chlorophyll bands in spirogyra, 5.
The spirogyra thread consists of cylindrical threads end to
end, 6. Protoplasm, 7. Cell-sap in spirogyra, 8. Reaction
of protoplasm to certain reagents, 9. Earlier use of the
term protoplasm, n. Protoplasm in mucor, 12. Mycelium
of mucor, 13. Appearance of the protoplasm, 14. Move-
ment of the protoplasm in mucor, 15. Test for protoplasm,
16. Protoplasm in nitella, 17. Form of nitella, 18. Inter-
node of nitella, 19. Cyclosis in nitella, 20. Test for proto-
plasm, 21. Protoplasm in one of the higher plants, 22.
Movement of protoplasm in the higher plants, 23. Move-
ment of protoplasm in cells of staminal hair of spiderwort,
24. Cold retards the movement, 25. Protoplasm occurs in
the living parts of all plants, 26 page I

CHAPTER II.

ABSORPTION, DIFFUSION, OSMOSE.

Osmose in spirogyra, 30. Turgescence, 31. Experiment with
beet in salt and sugar solutions, 32. Osmose in the cells of
the beet, 34. The coloring matter in the cell-sap does not
readily escape from the living protoplasm of the beet, 35.
The coloring matter escapes from dead protoplasm, 36.
Osmose experiments with leaves, 37. Absorption by root-
hairs, 39. Cell-sap a solution of certain substances, 40.
Diffusion through an animal membrane, 41. Importance of
these physical processes in plants, 44 page 13

X CONTENTS.

CHAPTER III.

ABSORPTION OF LIQUID NUTRIMENT.

Formula for solution of nutrient materials, 46. Plants take
liquid food from the soil, 50. How food solutions are car-
ried into the plant, 51. How the root-hairs get the watery
solutions from the soil, 52. Plants cannot remove all the
moisture from the soil, 53. Acidity of root-hairs, 56. . .page 22

CHAPTER IV.

TURGESCENCE.

Turgidity of plant parts, 58. Restoration of turgidity in shoots,
59. Tissue tensions, 61. Longitudinal tissue tension, 62.
Transverse tissue tension, 65 page 28

CHAPTER V.

ROOT PRESSURE.

Root pressure may be measured, 67. Experiment to demon-
strate root pressure, 68 page 31

CHAPTER VI.

, TRANS PI RATION.

Loss of water from excised leaves, 71. Loss of water from
growing plants, 72. Water escapes trom the surfaces of
living leaves in the form of water vapor, 73. Experiment
to compare loss of water in a dry and a humid atmosphere,
74. The loss of water is greater in a dry than in a humid
atmosphere, 75. How transpiration takes place, 76. Struc-
ture of a leaf, 79. Epidermis of the leaf, 80. Soft tissue
of the leaf, 81. Stomata, 82. The living protoplasm re-
tards the evaporation of water from the leaf, 83. Action of
the stomata, 84. Transpiration may be in excess of root
pressure, 85. Negative pressure, 86. Lifting power of
transpiration, 87. Root pressure may exceed transpiration,
88. Injuries caused by excessive root pressure, 89. Dem-
onstration of stomates and intercellular spaces, 92 page 33

CONTENTS. XI

CHAPTER VII.

PATH OF MOVEMENT OF LIQUIDS IN PLANTS.

Place the cut ends of leafy shoots in a solution of some red dye,
94. These solutions color the tracts in the stem and leaves
through which they flow, 95. Structure of the fibro-vascu-
lar bundles, 98. Woody portion of the bundle, 99. Bast
portion of the bundle, 100. Cambium region of the bundle,
101. Longitudinal section of the bundle, 102. Vessels or
ducts, 103. Sieve tubes, 105. Fibro-vascular bundle in In-
dian corn, 107. Rise of water in the vessels, 108. Synopsis
of tissues, no page 42

CHAPTER VIII.

DIFFUSION OF GASES.

Gas given off by green plants in the sunlight, in. What this
gas is, 117. Oxygen given off by green land plants also,
118. Absorption of carbon dioxide, 119. The gases are
exchanged in the plants, 122. A chemical change of the
gas takes place within the plant cell, 123. Gases as well as
water can diffuse through the protoplasmic membrane, 124

page 49

CHAPTER IX.

RESPIRATION.

Oxygen from the air consumed during germination of seed, 127.
Carbon dioxide given off during germination, 128. Respi-
ration is necessary for growth, 130. Energy set free during
respiration, 132. Respiration in a leafy plant, 133. Respi-
ration in fungi, 134. Respiration in plants in general, 135-
Respiration a breaking-down process, 136. Detailed result
of the above experiment, 137. Another way of performing
the experiment, 138. Intramolecular respiration, 139.. page 54

CHAPTER X.

THE CARBON FOOD OF PLANTS.

Starch formed as a result of carbon conversion, 141. Iodine
used as a test for starch, 142. Schimper's method of testing

xil CONTENTS.

for the presence of starch, 143. Green parts of plants form
starch when exposed to the light, 147. Starch is formed
only in the green parts of plants, 148. Translocation of
starch, 149. Starch in other parts of plants than the leaves,
• 151. Form of starch grains, 153 page 59

CHAPTER XL

CHLOROPHYLL AND FORMATION OF STARCH.

Fungi cannot form starch, 155. Etiolated plants cannot convert
carbon, 156. Chlorophyll and chloroplasts, 157. Form of
the chlorophyll bodies, 158. Chlorophyll is a pigment which
resides in the chloroplast, 159. Chlorophyll absorbs energy
from sunlight for carbon conversion, 160. Rays of light
concerned in carbon conversion, 161. Starch grains formed
in the chloroplasts, 162. Carbon conversion in other than
green plants, 164. Influence of light on the movement of
chlorophyll bodies, 165 page 65

CHAPTER XII.
NUTRITION; MEMBERS OF THE PLANT BODY.

Nutrition of liverworts, 167. Riccia, 167. Marchantia, 168.
Frullania, 169. Nutrition in the mosses, 170. The plant
body, 171. Members of the plant body, 172. Stem series,
173. Leaf series, 174. The root, 175 page 70

CHAPTER XIII.

GROWTH.

Growth in mucor, 177. Formation of the gonidia, 178. The
gonidia absorb water and increase in size before germinat-
ing, 179. How the gonidia germinate, 180. The germ tube
branches and forms the mycelium, 181. Growth in length
takes place only at the end of the thread, 182. Proto-
plasm increases by assimilation of nutrient substances, 183.
Growth of roots, 184. Roots of the pumpkin, 185. The
region of elongation, 186. Movement of the region of the
greatest elongation, 187. Formative region, 188. Growth
of the stem, 189. Force exerted by growth, 190. Grand
period of growth, 191. Energy of growth, 193. Nutation,
194 page 75

CONTENTS. Xlii

CHAPTER XIV.

IRRITABILITY.

Influence of the earth on the direction of growth, 197. Influ-
ence of light on growth, 199. Influence of light on the di-
rection of growth, 200. Diaheliotropism, 201. Epinasty
and hyponastv, 202. Leaves with a fixed diurnal position,
203. Importance of these movements, 204. Influence of
light on the structure of the leaf, 205. Movement influ-
enced by contact, 206. Sensitive plants, 207. Movement in
response to stimuli, 208. Transmission of the stimulus, 209.
Cause of the movement, 210. Paraheliotropism of the
leaves of the sensitive plant, 211. Sensitiveness of insec-
tivorous plants, 212. Hydrotropism, 213. Temperature,
214 page 82

PART II.

MORPHOLOGY.

CHAPTER XV.

SPIROGYRA.

Form of spirogyra, 220. Multiplication of the threads, 221.
How some of the threads break, 222. Conjugation of spiro-
gyra, 223. How the threads conjugate or join, 225. How
the protoplasm moves from one cell to another, 226. The
zygospores, 227. Life cycle, 228. Fertilization, 229. Sim-
plicity of the process, 230. Position of the plant spirogyra,
231 page 93

CHAPTER XVI.

CEDOGONIUM.

Form of oedogonium, 235. Fruiting stage of oedogonium, 236.
Sexual organs of oedogonium; oogonium and egg, 237.
Dwarf male plants, 238. Antheridium, 239. Zoospore
stage of oedogonium, 240. Asexual reproduction, 241. Sex-
ual reproduction, 242. Antheridia, 242. Oogonia, 243.
CEdogonium compared with spirogyra, 244. Position of
oedogonium, 245. Relatives of oedogonium, 246 page 99

XIV CONTENTS.

CHAPTER XVII.

VAUCHERIA.

Zoogonidia of vaucheria, 248. Sexual reproduction in vau-
cheria, 249. Vaucheria sessilis, the sessile vaucheria, 250.
Sexual organs of vaucheria, Antheridium, 251. Oogonium,
252. Fertilization, 253. The twin vaucheria (V. geminata),
254. Vaucheria compared with spirogyra, 255 ......... page 109

CHAPTER XVIII.

COLEOCH^TE.

The shield-shaped coleochaete, 257. Fruiting stage of coleo-
chaete, 258. Zoospore stage, 259. Asexual reproduction,
260. Sexual reproduction, oogonium, 261; antheridium,
262. Sporocarp, 263. Comparative table for spirogyra,
vaucheria, cedogonium, and coleochaete, 264 ........... page no

CHAPTER XIX.

BROWN AND RED

Brown algae (phaeophyceae), 266. Form and occurrence of fucus,
267. Structure of the conceptacles, 268. Fertilization, 269.
The red algae, 270. Gracillaria, 271. Rhabdonia, 272.
Principal groups of algae, 273 ......................... page 115

CHAPTER XX.
FUNGI; MOULDS; WATER MOULDS; DOWNY MILDEWS.

Mucor, 275. Asexual reproduction, 276. Sexual stage, 277.
Gemmae, 278. Water moulds (saprolegnia), 279. Appear-
ance of the saprolegnia, 280. Sporangia of saprolegnia,
281. Zoogonidia of saprolegnia, 282. Sexual reproduction
of saprolegnia, 283. Downy mildews, 285 ............. page 120

CHAPTER XXI.
FUNGI (continued)\ RUSTS; ASCOMYCETES.

Wheat rust (Puccinia graminis), 289. Teleutospores of the
black-rust form, 290. Uredospores of the red-rust form,
291. Cluster-cup form on the barberry, 292. Spermagonia,

CONTENTS. XV

293. How the cluster-cup stage was found to be a part of
the wheat rust, 2930. Uredospores can produce successive
crops, 294. Teleutospores the last stage in the season, 295.
How the fungus gets back from the wheat to the barberry,
296. Synopsis of life history of wheat rust, 297. Sac fungi,
299. Fruit bodies of the willow mildew, 300. Asci and
ascospores, 301. The sac fungi or ascomycetes, 302. Clas-
sification of the fungi, 304 page 129

CHAPTER XXII.

LIVERWORTS.

Riccia, 307. Form of the floating riccia (R. fluitans), 307. Form
of the circular riccia (R. crystallina), 308. Sexual organs,
309. Archegonia, 310. Antheridia, 311. Embryo, 312.
Sporogonium of riccia, 313. A new phase in plant life, 314.
Riccia compared with coleochaete, cedogonium, etc., 315.
Marchantia, 316. Antheridial plants, 317. Archegonial
plants, 319 page 140

CHAPTER XXIII.

LIVERWORTS (continued}.

Sporogonium of marchantia, 320. Spores and elaters, 321.
Sporophyte of marchantia compared with riccia, 322.
Sporophyte dependent on the gametophyte for its nourish-
ment, 323. Development of the Sporogonium, 324. Em-
bryo, 325. How marchantia multiplies, 326. Buds or
gemmae of marchantia, 327. Leafy-stemmed liverworts,
328. Frullania, 329. Porella, 330. Sporogonium of a foliose
liverwort, 331 • • • • page 149

CHAPTER XXIV.

MOSSES.

Mnium, 334. The fruiting moss plant, 336. The male and fe-
male moss plants, 337. Sporogonium, 338. Structure of
the moss capsule, 339. Development of the Sporogonium,
342. Protonema of the moss, 343. Table showing relation
of gametophyte and Sporophyte in the liverworts and
mosses, 344 page 158

XVI CONTENTS.

CHAPTER XXV.

FERNS.

The Christmas fern, 346. Fruit dots, 347. Sporangia, 348.
Structure of a sporangium, 349. Opening of the sporan-
gium and dispersion of the spores, 351. How does the
opening and snapping of the sporangium take place? 352.
The movement of the sporangium can take place in old and
dried material, 354. The common polopody, 356. Other
ferns, 357. Opening of the leaves of ferns, 358. Longevity
of ferns, 359. Budding of ferns, 360. The fern plant is a
sporophyte, 363. Is there a gametophyte phase in ferns?
364 page 165

CHAPTER XXVI.

FERNS (concluded}.

Gametophyte of ferns, 365. Sexual stage of ferns, 365. Spores,
367. Germination of the spores, 368. Protonema, 369.
Prothallium, 370. Sexual organs of ferns, 371. Antheridia,
372. Archegonia, 373. Sporophyte, 374. Embryo, 374.
Comparison of ferns with liverworts and mosses, 375 ..page 176

CHAPTER XXVII.

HORSETAILS.

The field equisetum, 380. Fertile shoot, 380. Sporangia, 381.
Spores, 382. Sterile shoot of the common horsetail, 383.
The scouring rush or shave grass, 384. Gametophyte of
equisetum, 385 page 187

CHAPTER XXVIII.

CLUB MOSSES.

The clavate lycopodium, 387. Fruiting spike of Lycopodium
clavatum, 388. Lycopodium lucidulum, 389. Bulbils on
Lycopodium lucidulum, 390. The little club mosses, 392.
Sporangia, macrospores and microspores, 393. Male pro-
thallia, 394. Female prothallia, 395. Embryo, 396 page 191

CONTENTS. xvii

CHAPTER XXIX.

QUILLWORTS.

Sporangia of isoetes, 398. Male prothallia, 401. Female pro-

thallia, 402. Embryo, 403 page 196

CHAPTER XXX.

COMPARISON OF FERNS AND THEIR RELATIONS.

Comparison of selaginella and isoetes with the ferns, 404. Gen-
eral classification of ferns, 407. Table showing relation of
gametophyte and sporophyte in the pteridophyta, 408. . page 199

CHAPTER XXXI.

GYMNOSPERMS.

The white pine, 409. General aspect of the white pine, 409.
The long shoots of the pine 410. The dwarf shoots of the
pine, 411. Spore-bearing leaves of the pine, 412. Male
cones or male flowers, 413. Microspores of the pine, or
pollen grains, 414. Form of the mature female cone, 415.
Form of a scale of the female flower, 417. Ovules or macro-
sporangia of the pine, 418. Pollenation, 419. Female pro-
thallium of the pine, 422. Archegonia, 423. Male prothal-
lia, 424. Farther growth of the male prothallium, 425.
Fertilization, 426. Homology of the parts of the female
cone, 427 page 202

CHAPTER XXXII.

FARTHER STUDIES ON GYMNOSPERMS.

Cycas, 428. Female prothallium of cycas, 429. Microspores or
pollen of cycas, 431. The gingko tree, 432. Spermatozoids
in some gymnosperms, 434. The sporophyte in the gymno-
sperms, 435. The gametophyte has become dependent on
the sporophyte, 436. Gymnosperms are naked seed plants,
437. Classification of gymnosperms, 438. Table showing
homologies of sporophyte and gametophyte in the pine,
439 PaSe 2I4

xviii CONTENTS.

CHAPTER XXXIII.

MORPHOLOGY OF THE ANGIOSPERMS. TRILLIUM; DENTARIA.

Trillium, 440. General appearance, 440. Parts of the flower,
calyx, 441. Corolla, 442. Andrcecium, 443. The stamen a
sporophyll, 444. Gynoecium, 445. Transformation of the
flower of trillium, 446. Dentaria, 447. General appear-
ance, 447. Parts of the flower, 448 page 221

CHAPTER XXXIV.

GAMETOPHYTE AND SPOROPHYTE OF ANGIOSPERMS.

Male prothaltium of angiosperms, 450. Macrospore and em-
bryo-sac, 453. Embryo-sac is the young female prothal-
lium, 445. Fertilization, 456. Fertilization in plants is
fundamentally the same as in animals, 457. Embryo, 458.
Endosperm the mature female prothallium, 459. Seed, 460.
Perisperm, 461. Presence or absence of endosperm in the
seed, 462. Sporophyte is prominent and highly developed,
463. The gametophyte once prominent has become degen-
erate, 464. Synopsis of members of the sporophyte in
angiosperms, 467. Table showing homologies of sporo-
phyte and gametophyte in angiosperms, 468 page 228

CHAPTER XXXV.

MORPHOLOGY OF THE NUCLEUS AND SIGNIFICANCE OF
GAMETOPHYTE AND SPOROPHYTE.

Direct division of the nucleus, 470. Indirect division of the nu-
cleus, 471. Chromatin and linin of the nucleus, 472. The
chromatin skein, 473. Chromosomes, nuclear plate, and
nuclear spindle, 474. The number of chromosomes usually
the same in a given species throughout one phase of the
plant, 474«. When fertilization takes place the number of
chromosomes is doubled in the embryo, 474^. Reduction of
the number of chromosomes in the nucleus, 475. Signifi-
cance of karyokinesis and reduction, 476. The gametophyte
may develop directly from the tissue of the sporophyte, 477.
The sporophyte may develop directly from the tissue of the
gametophyte, 478. Perhaps there is not a fundamental dif-
ference between the gametophyte and sporophyte, 479. page 239

CONTENTS. xix

LESSONS ON PLANT FAMILIES.
CHAPTER XXXVI.

RELATIONSHIPS SHOWN BY FLOWER AND FRUIT.

Importance of the flower in showing kinships among the higher
plants, 480. Arrangement of flowers, 482. The fruit, 485

page 247

CHAPTER XXXVII.

MONOCOTYLEDONS.

(For lessons and topics see synopsis at close of the lessons.)
Classification, 486. Species, 486. Genus, 487. Genus trillium,
488. Genus erythronium, 489. Genus lilium, 490. Family
liliaceae, 491. Floral formula, 492. Cohesion and adhe-
sion, 493. Floral diagram, 494 page 251

CHAPTER XXXVIII.
MONOCOTYLEDONS (concluded} 258

CHAPTER XXXIX.

DICOTYLEDONS 2&2

CHAPTER XL.
DICOTYLEDONS (continued ) 265

CHAPTER XLI.
DICOTYLEDONS (continued} 273

CHAPTER XLII.
DICOTYLEDONS (concluded} 283

CHAPTER XLIII.

OUTLINE OF TWENTY LESSONS IN THE ANGIOSPERMS 294

XX CONTENTS.

PART III.
ECOLOGY.

INTRODUCTION. page 300

CHAPTER XLIV.

WINTER BUDS; GROWTH OF WOODY SHOOTS; LEAF ARRANGEMENT.

Winter buds and how the young leaves are protected, 564.
Twigs and buds of the horse-chestnut, 565. Leaf scars, 566.
Lateral buds, 567. Bud leaves, 568. Opening of the buds
in the spring, 569. Growth in thickness of woody stems,
571. Difference in the firmness of the woody rings, 575.
Annual rings in woody stems. 576. Phyllotaxy or arrange-
ment of leaves, 579 Page 3°2

CHAPTER XLV.

SEEDLINGS.

The common garden bean, 584. The castor-oil bean, 585. How
the embryo gets out of a pumpkin seed, 586. Arisama
triphyllum^ 588. Germination of the seed of " jack-in-the-
pulpit," 588. How the embryo backs out of the seed, 589.
How the first leaf appears, 591. The first leaf of " jack-in-
the-pulpit " is a simple one, 592 page 307

CHAPTER XLVI.

FURTHER STUDIES ON NUTRITION.

Nutrition in lemna, 594. Spirodela polyrrhiza, 595. Nutrition
in wolffia, 596. Nutrition in lichens, 597. Nitrogen
gatherers, 599. How clovers, peas, and other legumes
gather nitrogen, 599. A fungal or bacterial organism in
these root tubercles, 600. How the organism gets in the
roots of the legumes, 601. The root organism assimilates
free nitrogen for its host, 602. Mycorhiza, 603. Nutrition
of the dodder, 605. Carnivorous plants, 606. Nutrition of
bacteria, 607 page 314

CONTENTS. xxi

CHAPTER XLVII.

FURTHER STUDIES ON NUTRITION (concluded}.

Nutrition of moulds, 608. Nutrition of parasitic fungi, 609.
Nutrition of the larger fungi, 610. Studies of mushrooms,
613. Form of the mushroom, 613. Fruiting surface of the
mushroom, 614. How the mushroom is formed, 615. Be-
ware of the poisonous mushrooms, 617. Wood-destroying
fungi, 619 page 322

CHAPTER XLVIII.

DIMORPHISM OF FERNS.

Dimorphism in the leaves of ferns, 624. The sensitive fern,
625. Transformation of the fertile leaves of onoclea to
sterile ones, 626. The sporangia decrease as the fertile leaf
expands, 628. The ostrich fern, 629. Dimorphism in tropi-
cal ferns, 630 page 340

CHAPTER XLIX.

FORMATION OF EARLY SPRING FLOWERS.

Trillium, 631. The adder tongue (erythronium), 633. Indian

turnip, 634 page 347

CHAPTER L.

HETEROSPORY. POLLENATION.

Origin of heterospory and the necessity for pollenation, 639.
Both kinds of sexual organisms on the same prothallium,
639. Cross fertilization in monoecious prothallia, 640. Ten-
dency toward dioecious prothallia, 641. The two kinds of
sexual organs on different prothallia, 642. Permanent sep-
aration of the sexes by different amounts of nutriment
supplied the spore, 643. Heterospory, 644. In the pterido-
phytes water serves as the medium for conveying the
sperm cell to the female organ; 645. In the higher plants a
modification of the prothallium is necessary, 646. Pollena-
lion, 649. Self pollenation or close pollenation, 649. Wind
pollenation, 650 Pollenation by insects, 651. Pollenation
of the bluet, 653. Pollenation of the primrose, 654. Pol-

XX11 CONTENTS.

lenation of the skunk's cabbage, 655. Spiders have discov-
ered this curious relation of the flowers and insects, 657.
Pollenation of jack-in-the-pulpit, 658. Pollenation of or-
chids, 660. Pollenation of canna, 664 page 351

CHAPTER LI.

SEED DISTRIBUTION.

Means for dissemination of seed, 672. The prickly lettuce, 676.
The wild lettuce, 677. The milk-weed or silk-weed, 678.
The virgin's bower, 680 page 368

CHAPTER LII.

STRUGGLE FOR OCCUPATION OF LAND.

Retention of made soil, 681. Vegetation of sand dunes, 683.

Reforestation of lands, 684. Beauty of old fields, 689. .page 374

CHAPTER LIII.

SOIL FORMATION IN ROCKY REGIONS AND IN MOORS.

Lichens, 690. Lichens are among the pioneers in soil forma-
tion, 691. Other plants of rocky regions, 692. Filling of
ponds by plants, 694. A plant atoll, 695. Topography of
the atoll moor, 696. A floating inner zone, 698. How was
the atoll formed? 700. A black-spruce moor, 703. Fall of
the trees of the marginal zone when the windbreak was
removed, 704. Dying of the spruce of the central area, 705.
Other mbrainic moors, 708. The bald cypress (taxodium),
711 page 381

CHAPTER LIV.

ZONAL DISTRIBUTION OF PLANTS.

On the margins of lakes and ponds, 712. On the banks of a

stream, 716 page 400

CHAPTER LV.
PLANT COMMUNITIES; SEASONAL CHANGES.

Plants of widely different groups may exist in the same com-
munity, 720. Seasonal succession in plant communities,

CONTENTS. xxiii

722. The landscape a changing panorama, 725. Refoliation
of bare forests in the spring, 726. The summer tints are
more subdued, 728. Autumn colors, 729. Fall of the leaf,
730 page 410

CHAPTER LVI.

ADAPTATION OF PLANTS TO CLIMATE.

Some characteristics of desert vegetation. 731. Some plants of
temperate regions possess characters of desert vegetation,
735. Alpine plants with desert characters, 737. Low stat-
ure of alpine plants a protection against wind and cold, 738.
Some plants of swamps and moors present characters of
arctic or desert vegetation, 739. Hairs on young leaves
protect against cold, 740 page 419

BOTANY.

CHAPTER I.

PROTOPLASM.*

1. In the study of plant life and growth, it will be found
convenient first to inquire into the nature of the substance
which we call the living material of plants. For plant growth,
as well as some of the other processes of plant life, are at bottom
dependent on this living matter. This living matter is called in
general protoplasm.

2. In most cases protoplasm cannot be seen without the
help of a microscope, and it will be necessary for us here to em-
ploy one if we wish to see protoplasm, and to satisfy ourselves
by examination that the substance we are dealing with is
protoplasm.

3. We will find it convenient first to examine protoplasm in
some of the simpler plants; plants which from their minute size
and simple structure are so transparent that when examined with
the microscope the interior can be seen.

For our first study we will take a plant known as spirogyra,
though there are a number of others which would serve the pur-
pose quite as well, and may quite as easily be obtained for
study.

*For apparatus, reagents, collection and preservation of material, etc., see
Appendix.

PHYSIOLOGY.

Protoplasm in spirogyra.

4. The plant spirogyra. — This plant is found in the water
of pools, ditches, ponds, or in streams of. slow-running water.
It is green in color, and occurs in loose mats, usually floating
near the surface. The name " pond-scum" is sometimes given
to this plant, along with others which are more or less closely
related. It is an alga, and belongs to a group of plants known
as algcz. If we lift a portion of it from the water, we see that
the mat is made up of a great tangle of green silky threads.
Each one of these threads is a plant, so that the number con-
tained in one of these floating mats is very great.

Let us place a bit of this thread tangle on a glass slip, and
examine with the microscope and we will see certain things about
the plant which are peculiar to it, and which enable us to dis-
tinguish it from other minute green water plants. We shall
also wish to learn what these peculiar parts of the plant are, in
order to demonstrate the protoplasm in the plant.*

5. Chlorophyll bands in spirogyra. — We first observe the
presence of bands ; green in color, the edges of which are
usually very irregularly notched. These bands course along in
a spiral manner near the surface of the thread. There may be
one or several of these spirals, according to the species which
we happen to select for study. This green coloring matter of
the band is chlorophyll, and this substance, which also occurs in
the higher green plants, will be considered in a later chapter.
At quite regular intervals in the chlorophyll band are small
starch grains, grouped in a rounded mass enclosing a minute
body, the pyrenoid, which is peculiar to many algae.

6. The spirogyra thread consists of cylindrical cells end to
end. — Another thing which attracts our attention, as we examine
a thread of spirogyra under the microscope, is that the thread is

* If spirogyra is forming fruit some of the threads will be lying parallel in
pairs, and connected with short tubes. In some of the cells there will be
found rounded or oval bodies known as zygospores. These may be seen in
fig. 86, and will be described in another part of the book.

PROTOPLASM.

3

made up of cylindrical segments or compartments placed end to
end. We can see a distinct separating line be-
tween the ends. Each one of these segments or
compartments of the thread is a cell, and the
boundary wall is in the form of a cylinder with
closed ends.

7. Protoplasm. — Having distinguished these
parts of the plant we can look for the protoplasm.
It occurs within the cells. It is colorless (i.e.,
hyaline) and consequently requires close observa-
tion. Near the center of the cell can be seen a
rather dense granular body of an elliptical or
irregular form, with its long diameter transverse
to the axis of the cell in some species ; or trian-
gular, or quadrate in others. This is the nucleus.
Around the nucleus is a granular layer from which
delicate threads of a shiny granular substance
radiate in a starlike manner, and terminate in the
chlorophyll band at one of the pyrenoids. A
granular layer of the same substance lines the
inside of the cell wall, and can be seen through
the microscope if it is properly focussed. This
granular substance in the cell is protoplasm.

8. Cell-sap in spirogyra. — The greater part of
the interior space of the cell, that between the
radiating strands of protoplasm, is occupied by
a watery fluid, the " cell-sap."

9. Reaction of protoplasm to certain reagents.
— We can employ certain tests to demonstrate
that this granular substance which we have seen
is protoplasm, for it has been found, by repeated

. . , J . , Thread of spiro-

expenments with a great many kinds of plants, gym, showing lone

. . cells, chlorophyll

that protoplasm gives a definite reaction in re- band, nucleus,

strands of proto-

sponse to treatment with certain substances called plasm, and the

granular wall layer

reagents. Let us mount a few threads of the of protoplasm
spirogyra in a drop of a solution of iodine, and observe the

PHYSIOLOGY.

results with the aid of the microscope. The iodine gives a
yellowish-brown color to the protoplasm, and it can be more
distinctly seen. The nucleus is also much more prominent
since it colors deeply, and we can perceive within the nucleus
one small rounded body, sometimes more, the nudeolus. The
iodine here has stained the living protoplasm. The proto-
plasm, however, in a living condition will resist for a time some

other reagents,
as we shall see
if we attempt
to stain it with
a one per cent
aqueous solu-
tion of a dye
known as eosin.
Let us mount a
few living
threads in such
a solution of
eosin, and after
a time wash off
the stain.

Fig. 2.

Fig- 3-

Cell of spirogyra before treat- Cell of spirogyra after treatment
ment with iodine. with alcohol and iodine.

protoplasm remains uncolored. Now let us place these threads
for a short time, two or three minutes, in strong alcohol, which
kills the protoplasm. Then mount them in the eosin solution.
The protoplasm now takes the eosin stain. After the proto-
plasm has been killed we note that the nucleus is no longer
elliptical or angular in outline, but is rounded. The strands of
protoplasm are no longer in tension as they were when alive.

10. Let us now take some fresh living threads and mount
them in water. Place a small drop of dilute glycerine on the
slip at one side of the cover glass, and with a bit of filter paper
at the other side draw out the water. The glycerine will flow
under the cover glass and come in contact with the spirogyra
threads. Glycerine absorbs water promptly. Being in contact
with the threads it draws water out of the cell cavity, thus caus-

PROTOPLASM.

ing the layer of protoplasm which lines the inside of the cell
wall to collapse, and separate from the wall, drawing the
chlorophyll band
inward toward the
center also. The
wall layer of proto-
plasm can now be
more distinctly
seen and its gran-
ular character ob-
served.

We have thus
employed three
tests to demon-
strate that this sub-
stance with which
we are dealing
shows the reac-
tions which we
know by experi-
ence tO be given treatment'with 'glycerine.

by protoplasm. We therefore conclude that this colorless and
partly granular, slimy substance in the spirogyra cell is proto-
plasm, and that when we have performed these experiments,
and noted carefully the results, we have seen protoplasm.

11. Earlier use of the term protoplasm. — Early students of the living
matter in the cell considered it to be alike in substance, but differing in
density; so the term protoplasm was applied to all of this living matter. The
nucleus was looked upon as simply a denser portion of the protoplasm, and
the nucleolus as a still denser portion. Now it is believed that the nucleus is
a distinct substance, and a permanent organ of the cell. The remaining por-
tion of the protoplasm is now usually spoken of as the cytoplasm.

In spirogyra then the cytoplasm in each cell consists of a layer which lines
the inside of the cell wall, a nuclear layer, which surrounds the nucleus, and
radiating strands which connect the nucleus and wall layers, thus suspending
the nucleus near the center of the cell. But it seems best in this elementary
study to use the term protoplasm in its general sense.

Fig. 4.
Cell of spirogyra before

Fig- 5-

Cells of spirogyra after treatment
with glycerine.

PHYSIOLOGY.

Protoplasm in mucor.

12. Let us now examine in a similar way another of the
simple plants with the special object in view of demonstrating
the protoplasm. For this purpose we may take one of the plants
belonging to the group of fungi. These plants possess no
chlorophyll. Ono of several species of mucor, a common
mould, is readily obtainable, and very suitable for this study.*

13. Mycelium of mucor. — A few days after sowing in some
gelatinous culture medium we find slender, hyaline threads, which
are very much branched, and, radiating from a central point, form
circular colonies, if the plant has not been too thickly sown, as
shown in fig. 6. These threads of the fungus form the myce-
lium. From these characters of the plant, which we can readily
see without the aid of a microscope, we note how different it is
from spirogyra.

To examine for protoplasm let us lift carefully a thin block of
gelatine containing the mucor threads, and mount it in water on
a glass slip. Under the microscope we see only a small portion
of the branched threads. In addition to the absence of chlo-
rophyll, which we have already noted, we see that the myce-
lium is not divided at short intervals into cells, but appears
like a delicate tube with branches, which become successively
smaller toward the ends.

14. Appearance of the protoplasm. — Within the tube-like
thread now note the protoplasm. It has the same general ap-
pearance as that which we noted in spirogyra. It is slimy, or
semi-fluid, partly hyaline, and partly granular, the granules con-
sisting of minute particles (the microsomes). While in mucor the
protoplasm has the same general appearance as in spirogyra, its
arrangement is very different. In the first place it is plainly

* The most suitable preparations of mucor for study are made by growing
the plant in a nutrient substance which largely consists of gelatine, or, better,
agar-agar, a gelatinous preparation of certain seaweeds. This, after the
plant is sown in it, should be poured into sterilized shallow glass plates,
called Petrie dishes.

PROTOPLASM.

continuous throughout the tube. We do not see the prominent
radiations of strands around a large nucleus, but still the proto-

Fig 6.
Colonies of mucor.

plasm does not fill the interior of the threads. Here and there
are rounded clear spaces termed vacuoles, which are filled with
the watery fluid, cell-sap. The nuclei in mucor are very mi-
nute, and cannot be seen except after careful treatment with
special reagents.

15 Movement of the protoplasm in mucor. — While exam-
ining the protoplasm in mucor we are likely to note streaming
movements. Often a current is seen flowing slowly down one
side of the thread, and another flowing back on the other side,
or it may all stream along in the same direction.

16. Test for protoplasm. — Now let us treat the threads with
a solution of iodine. The yellowish-brown color appears which
is characteristic of protoplasm when subject to this reagent.

PHYSIOLOG Y.

If we attempt to stain the living protoplasm with a one per
cent aqueous solution of eosin it resists it for a time, but if we
first kill the protoplasm with strong alcohol, it reacts quickly to
the application of the eosin. If we treat the living threads
with glycerine the protoplasm is contracted away from the wall,
as we found to be the case with spirogyra. While the color,

Fig. 7.
Thread of mucor, showing protoplasm and vacuoles.

form and structure of the plant mucor is different from spiro-
gyra, and the arrangement of the protoplasm within the plant
is also quite different, the reactions when treated by certain re-
agents are the same. We are justified then in concluding that
the two plants possess in common a substance which we call
protoplasm.

Protoplasm in nitella.

17. One of the most interesting plants for the study of one remarkable
peculiarity of protoplasm is Nitella. This plant belongs to a small group
known as stoneworts. They possess chlorophyll, and, while they are still
quite simple as compared with the higher plants, they are much higher in the
scale than spirogyra or mucor.

18. Form of nitella — A common species of nitella is Nitella flexilis.
It grows in quiet pools of water. The plant consists of a main axis, in the
form of a cylinder. At quite regular intervals are whorls of several smaller
thread-like outgrowths, which, because of their position, are termed " leaves,"
though they are not true leaves. These are branched in a characteristic fash-
ion at the tip. The main axis also branches, these branches arising in the axil
of a whorl, usually singly. The portions of the axis where the whorls arise
are the nodes. Each node is made up of a number of small cells definitely
arranged. The portion ot the axis between two adjacent whorls is an inter-

PROTOPLASM.

node. These internodes are peculiar. They consist of but a single " cell,"
and are cylindrical, with closed ends. They are sometimes 5-10 cm. long.

19. Internode of nitella.— For the study of an internode of nitella, a
small one, near the end, or the ends of one of the " leaves " is best suited,
since it is more transparent. A small \

portion of the plant should be placed
on the glass slip in water with the
cover glass over a tuft of the branches
near the growing end. Examined with
the microscope the green chlorophyll bodies, which
form oval or oblong discs, are seen to be very numer-
ous. They lie quite closely side by side and form in
perfect rows along the inner surface of the wall. One
peculiar feature of the arrangement of the chlorophyll
bodies is that there are two lines, extending from one
end of the internode to the other on opposite sides,
where the chlorophyll bodies are wanting. These are
known as neutral lines. They run parallel with the
axis of the internode, or in a more or less spiral
manner as shown in fig. 9.

20. Cyclosis in nitella. — The chlorophyll bodies
are stationary on the inner surface of the wall, but
if the microscope be properly focussed just beneath
this layer we notice a rotary motion of particles in
the protoplasm. There are small granules and quite
large masses of granular matter which glide slowly
along in one direction on a given side of the neutral
line. If now we examine the protoplasm on the other
side of the neutral line, we see that the movement is
in the opposite direction. If we examine this move-
ment at the end of an internode the particles are seen

to glide around the end from one side of the neutral line to the other. So
that when conditions are favorable, such as temperature, healthy state of the
plant, etc., this gliding of the particles or apparent streaming of the proto-
plasm down one side of the " cell," and back upon the other, continues in
an uninterrupted rotation, or cydosis. There are many nuclei in an internode
of nitella, and they move also.

21. Test for protoplasm. — If we treat the plant with a solution of iodine
we get the same reaction as in the case of spirogyra and mucor. The proto-
plasm becomes yellowish brown.

22. Protoplasm in one of the higher plants. — We now wish
to examine, and test for, protoplasm in one of the higher plants.

Fig.
Portion of plant nitella.

10 PHYSIOLOGY.

Young or growing parts of any one of various plants — the petioles
of young leaves, or young stems of growing plants — are suitable
for study. Tissue from the pith of corn (Zea mays) in young

shoots just back of the
growing point or quite
near the joints of older but
growing corn stalks fur-
Fig 9 nishes excellent material.

Cyclosis in nitella. If we should place part

of the stem of this plant under the microscope we should find
it too opaque for observation of the interior of the cells. This
is one striking difference which we note as we pass from the low
and simple plants to the higher and more complex ones ; not
only in general is there an increase of size, but also in general
an increase in thickness of the parts. The cells, instead of lying
end to end or side by side, are massed together so that the parts
are quite opaque. In order to study the interior of the plant
we have selected it must be cut into such thin layers that the
light will pass readily through, them.

For this purpose we section the tissue selected by making with
a razor, or other very sharp knife, very thin slices of it. These
are mounted in water in the usual way for microscopic study. In
this section we notice that the cells are polygonal in form.
This is brought about by mutual pressure of all the cells. The
granular protoplasm is seen to form a layer just inside the wall,
which is connected with the nuclear layer by radiating strands
of the same substance. The nucleus does not always lie at the
middle of the cell, but often is near one side. If we now kill
with alcohol and treat with iodine the characteristic yellowish-
brown color appears. So we conclude here also that this sub-
stance is identical with the living matter in the other very differ-
ent plants which we have studied.

23. Movement of protoplasm in the higher plants. — Cer-
tain parts of the higher plants are suitable objects for the study
of the so-called streaming movement of protoplasm, especially
the delicate hairs, or thread-like outgrowths, such as the silk of

PROTOPLASM. II

corn, or the delicate staminal hairs of some plants, like those of
the common spiderwort, tradescantia, or of the tradescantias
grown for ornament in greenhouses and plant conservatories.

Sometimes even in the living cells of the corn plant which we
have just studied, slow streaming or gliding movements of the
granules are seen along the strands of protoplasm where they
radiate from the nucleus.

24. Movement of protoplasm in cells of the staminal hair of
" spiderwort." — A cell of one of these hairs from a stamen of a
tradescantia grown in glass houses is shown in fig. 10. The

Fig. 10.
Cell from stamen hair of tradescantia showing movement of the protoplasm.

nucleus is quite prominent, and its location in the cell varies con-
siderably in different cells and at different times. There is a
layer of protoplasm all around the nucleus, and from this the
strands of protoplasm extend outward to the wall layer. The
large spaces between the strands are, as we have found in other
cases, filled with the cell-sap.

An entire stamen, or a portion of the stamen, having several hairs attached,
should be carefully mounted in water. Care should be taken that the room be
not cold, and if the weather is cold the water in which the preparation is
mounted should be warm. With these precautions there should be little diffi-
culty in observing the streaming movement.

The movement is detected by observing the gliding of the
granules. These move down one of the strands from the nucleus
along the wall layer, and in towards the nucleus in another
strand. After a little the direction of the movement in any one
portion may be reversed.

25. Cold retards the movement. — While the protoplasm is
moving, if we rest the glass slip on a block of ice, the move-
ment will become slower, or will cease altogether. Then if we

12 PHYSIOLOGY.

warm the slip gently, the movement becomes normal again. We
may now apply here the usual tests for protoplasm. The result
is the same as*n the former cases.

26. Protoplasm occurs in the living parts of all plants. —
In these plants representing such widely different groups, we find
a substance which is essentially alike in all. Though its arrange-
ment in the cell or plant body may differ in the different plants
or in different parts of the same plant, its general appearance
is the same. Though in the different plants it presents, while
alive, varying phenomena, as regards mobility, yet when killed '
and subjected to well known reagents the reaction is in general
identical. Knowing by the experience of various investigators
that protoplasm exhibits these reactions under given conditions,
we have demonstrated to our satisfaction that we have seen proto-
plasm in the simple alga, spirogyra, in the common mould,
mucor, in the more complex stonewort, nitella, and in the cells
of tissues of the highest plants.

27. By this simple process of induction of these facts concerning
this substance in these different plants, we have learned an im-
portant method in science study. Though these facts and deduc-
tions are well known, the repetition of the methods by which they
are obtained on the part of each student helps to form habits of
scientific carefulness and patience, and trains the mind to logical
processes in the search for knowledge.

28. While we have by no means exhausted the study of protoplasm, we can,
from this study, draw certain conclusions as to its occurrence and appearance
in plants. Protoplasm is found in the living and growing parts of all plants.
It is a semi-fluid, or slimy, granular, substance ; in some plants, or parts of
plants, the protoplasm exhibits a streaming or gliding movement of the gran-
ules. It is irritable. In the living condition it resists more or less for some
time the absorption of certain coloring substances. The water may be with-
drawn by glycerine. The protoplasm may be killed by alcohol. When
treated with iodine it becomes a yellowish-brown color.

CHAPTER II.

ABSORPTION, DIFFUSION, OSMOSE.

29. We may next endeavor to learn how plants absorb
water or nutrient substances in solution. There are several
very instructive experiments, which can be easily performed,
and here again some of the lower plants will be found useful.

30. Osmose in spirogyra. — Let us mount a few threads of
this plant in water for microscopic examination, and then draw
under the cover glass a five per cent solution of ordinary table
salt (NaCl) with the aid of filter paper. We shall soon see
that the result is similar to that which was obtained when glycer-
ine was used to extract the water from the cell-sap, and to con-
tract the protoplasmic membrane from the cell wall. But the
process goes on evenly and the plant is not injured. The proto-
plasmic layer contracts slowly from the cell wall, and the move-
ment of the membrane can be watched by looking through the
microscope. The membrane contracts in such a way that all
the contents of the cell are finally collected into a rounded or
oval mass which occupies the center of the cell.

If we now add fresh water and draw off the salt solution,
we can see the protoplasmic membrane expand again, or move
out in all directions, and occupy its former position against the
inner surface of the cell wall. This would indicate that there is
some pressure from within while this process of absorption is
going on, which causes the membrane to move out against the
cell wall.

The salt solution draws water from the cell-sap. There
is thus a tendency to form a vacuum in the cell, and the
pressure on the outside of the protoplasmic membrane causes it

13

PHYSIOLOGY.

to move toward the center of the cell. When the salt solution
is removed and the thread of spirogyra is again bathed with
water, the movement of the water is inward in
the cell. This would suggest that there is some
substance dissolved in the cell-sap which does not
readily filter out through the membrane, but draws
on the water outside. It is this which produces
the pressure from within and crowds the mem-
brane out against the cell wall again.

Fig. ii.

Spirogyra before
placing in salt solu-

Spirogyra from salt
solution into water.

Fig. 12.
Spirogyra in $% salt solution.

31. Turgescence. — Were it not for the resistance which the
cell wall offers to the pressure from within, the delicate proto-

ABSORPTION, DIFFUSION, OSMOSE.

plasmic membrane would stretch to such an extent that it would
be ruptured, and the protoplasm therefore would be killed. If
we examine the cells at the ends of the
threads of spirogyra we will see in most
cases that the cell wall at the free end is
arched outward.
This is brought
about by the press-

Fig. 16.

From salt solution placed in water.
Figs. 14-16. — Osmosis in threads of mucor.

Fig. 14.

Before treatment with salt
solution.

lire from within
upon the proto- After
plasmic m e m -
brane which itself presses against
the cell wall, and causes it to
arch outward. This is beauti-
fully shown in the case of threads
which are recently broken. The cell wall is therefore elastic;
it yields to a certain extent to the pressure from within, but a
point is soon reached beyond which it will not stretch, and an
equilibrium then exists between the pressure from within on the
protoplasmic membrane, and the pressure from without by the
elastic cell wall. This state of equilibrium in a cell is turges-
cettce, or such a cell is said to be turgescent, or turgid.

32. Experiment with beet in salt and sugar solutions. —
We may now test the effect of a five per cent salt solution on a
portion of the tissues of a beet or carrot. Let us cut several
slices of equal size and about $mm in thickness. Immerse a
few slices in water, a few in a five per cent salt solution and a
few in a strong sugar solution. It should be first noted that all
the slices are quite rigid when an attempt is made to bend them
between the fingers. In the course of one or two hours or less,

i6

PHYSIOLOGY.

if we examine the slices we will find that those in water remain,
as at first, quite rigid, while those in the salt and sugar solutions
are more or less flaccid or limp, and will readily bend by pres-

Fig. 17. Fig. 1 8. Fig. 19.

Before treatment with salt After treatment with salt From salt solution into water
solution. solution. again.

Figs. 17-19. — Osmosis in cells of Indian corn.

sure between the fingers, the specimens in the salt solution,
perhaps, being more flaccid than those in the sugar solution.
The salt solution, we judge after our experiment with spirogyra,

Fig. 20.

Fig. 21.

Fig. 22.

Rigid condition of fresh beet Limp condition after lying in Rigid again after lying again

section. salt solution. in water.

Figs. 20-22. — Turgor and osmosis in slices of beet.

withdraws some of the water from the cell-sap, the cells thus
losing their turgidity and the tissues becoming limp or flaccid
from the loss of water.

ABSORPTION, DIFFUSION, OSMOSE. IJ

33. Let us now remove some of the slices of the beet from
the sugar and salt solutions, wash them with water and then im-
merse them in fresh water. In the course of thirty minutes to
one hour, if we examine them again, they will be found to have
regained, partly or completely, their rigidity. Here again we
infer from the former experiment with spirogyra that the sub-
stances in the cell-sap now draw water inward ; that is, the
diffusion current is inward through the cell walls and the proto-
plasmic membrane, and the tissue becomes turgid again.

34. Osmose in the cells of the beet.— We should now make a section of the
fresh tissue of a red colored beet for examination with the microscope, and
treat this section with the salt solution. Here we can see that the effect of the
salt solution is to draw water out of the cell, so that the protoplasmic mem-

salt

F'g. 25.
Later stage ot the same.

Fig. 23. Fig. 24.

Before treatment with salt After treatment with

solution. solution.

Figs. 23-25. — Cells from beet treated with salt solution to show osmosis and movement of
the protoplasmic membrane.

brane can be seen to move inward from the cell wall just as was observed in
the case of spirogyra.* Now treating the section with water and removing
the salt solution, the diffusion current is in the opposite direction, that is in-

* We should note that the coloring matter of the beet reside? in the cell-
sap. It is in these colored cells that we can best see the movement take
place, since the red color serves to differentiate well the moving mass from the
cell wall. The protoplasmic membrane at several points usually clings tena-
ciously so that at several places the membrane is arched strongly away from
the cell wall as shown in fig. 24. While water is removed from the cell-sap,
we note that the coloring matter does not escape through the protoplasmic
membrane.

1 8 PHYSIOLOGY.

ward through the protoplasmic membrane, so that the latter is pressed outward
until it comes in contact with the cell wall again, which by its elasticity soon
resists the pressure and the cells again become turgid.

35. The coloring matter in the cell- sap does not readily escape from the
living protoplasm of the beet. — The reel coloring matter, as seen in the sec-
tion under the microscope, does not escape from the cell-sap through the pro-
toplasmic membrane . When the slices are placed in water, the water is not
colored thereby. The same is true when the slices are placed in the salt or
sugar solutions. Although water is withdrawn from the cell-sap, this coloring
substance does not escape, or if it does it escapes slowly and after a consider-
able time.

36. The coloring matter escapes from dead protoplasm. — If, however, we
heat the water containing a slice of beet up to a point which is sufficient to
kill the protoplasm, the red coloring matter in the cell-sap filters out through
the protoplasmic membrane and colors the water. If we heat a preparation
made for study under the microscope up to the thermal death point we can
see here that the red coloring matter escapes through the membrane into the
water outside. This teaches that certain substances cannot readily filter
through the living membrane of protoplasm, but that they can filter through
when the protoplasm is dead. A very important condition, then, for the suc-
cessful operation of some of the physical processes connected with absorption
in plants is that the protoplasm should be in a living condition.

37. Osmose experiments with leaves. — We may next take the leaves of
certain plants like the geranium, coleus or other plant, and place them in
shallow vessels containing water, salt, and sugar solutions respectively. The
leaves should be immersed, but the petioles should project out of the water or
solutions. Seedlings of corn or beans, especially the latter, may also be
placed in these solutions, so that the leafy ends are immersed. After one or
two hours an examination will show that the specimens in the water are still
turgid. But if we lift a leaf or a bean plant from the salt or sugar solution,
it will be found to be flaccid and limp. The blade, or lamina, of the leaf
droops as if wilted, though it is still wet. The bean seedling also is flaccid,
the succulent stem bending nearly double as the lower part of the stem is held
upright. This loss of turgidity is brought about by the loss of water from the
tissues, and judging from the experiments on spirogyra and the beet, we con-
clude that the loss of turgidity is caused by the withdrawal of some of the
water from the cell-sap by the strong salt solution.

38. Now if we wash carefully these leaves and seedlings, which have been
in the salt and sugar solutions, with water, and then immerse them in fresh
water for a few hours, they will regain their turgidity. Here again we are led
to infer that the diffusion current is now inward through the protoplasmic
membranes of all the living cells of the leaf, and that the resulting turgidity
of the individual cells causes the turgidity of the leaf or stem.

ABSORPTION, DIFFUSION, OSMOSE.

39. Absorption by root hairs. — If we examine seedlings,
which have been grown in a germinator or in the folds of paper
or cloths so that the roots will be free from particles of soil, we
will see near the growing point of the roots that the surface is
covered with numerous slender, delicate, thread-
like bodies, the root hairs. Let us place a portion
of a small root containing some of these root
hairs in water on a glass slip, and prepare it for
examination with the microscope. We will see
that each thread, or root hair, is a continuous
tube, or in other words it is a single cell which
has become very much elongated. The proto-
plasmic membrane lines the wall, and strands of
protoplasm extend across at irregular intervals, the
interspaces being occupied by the cell -sap.

We should now draw under the cover glass
some of the five per cent salt solution. The
protoplasmic membrane moves away from the cell
wall at certain points, showing that plasmolysis is
taking place, that is, the diffusion current is out-
ward so that the cell-sap loses some of its water,
and the pressure from the outside moves the
membrane inward. We should not allow the salt
solution to work on the root hairs long. It should
be very soon removed by drawing in fresh water
before the protoplasmic membrane has been
broken at intervals, as is
apt to be the case by the
strong diffusion current
and the consequent
strong pressure from
without. The membrane Seedlins of
of protoplasm now moves

outward as the diffusion current is inward, and soon regains its
former position next the inner side of the cell wall. The
root hairs then, like other parts of the plant which we have

Fig. 27.

Root hair of corn
before and after
root treatment with $%

2O PHYSIOLOGY.

investigated, have the power of taking up water under press-
ure.

40. Cell-sap a solution of certain substances. — From these experiments we
are led to believe that certain substances reside in the cell-sap of plants, which
behave very much like the salt solution when separated from water by the
protoplasmic membrane. Let us attempt to interpret these phenomena by
recourse to diffusion experiments, where an animal membrane separates two
liquids of different concentration.

41. Diffusion through an animal membrane. — For this experiment we
may use a thistle tube, across the larger end of which should be stretched and
tied tightly a piece of a bladder membrane. A strong sugar solution (three
parts sugar to one part water) is now placed in the tube so that the bulb is
rilled and the liquid extends part way in the neck of the tube. This is im-
mersed in water within a wide-mouth bottle, the neck of the tube being sup-
ported in a perforated cork in such a way that the sugar solution in the tube is
on a level with the water in the bottle or jar. In a short while the liquid
begins to rise in the thistle tube, in the course of several hours having risen
several centimeters. The diffusion current is thus stronger through the mem-
brane in the direction of the sugar solution, so that this gains more water than
it loses.

42. We have here two liquids separated by an animal membrane, water on
the one hand which diffuses readily through the membrane, while on the other
is a solution of sugar which diffuses through the animal membrane with diffi-
culty. The sugar solution is also what is called a concentrated solution, i.e.,
it is more highly concentrated than water. The water, therefore, according
to a general law which has been found to obtain in such cases, diffuses more
readily through the membrane into the sugar solution, which thus increases in
volume, and also becomes more dilute. The bladder membrane is what is
sometimes called a diffusion membrane, since the diffusion currents travel
through it.

43. In this experiment then the bulk of the sugar solution is increased, and
the liquid rises in the tube by this pressure above the level of the water in the
jar outside of the thistle tube. The diffusion of liquids through a membrane
is osmosis, and the membrane, since it permits one liquid to pass in one direc-
tion more rapidly than in the other, is sometimes called a semipermeable
membrane.

44. Importance of these physical processes in plants. — Now if we recur
to our experiment with spirogyra we find that exactly the same processes take
place. The protoplasmic membrane is the diffusion membrane, or semiperme-
able membrane, through which the diffusion takes place. The salt solution
which is first used to bathe the threads.of the plant is a more highly concen-
trated solution than that of the cell-sap within the cell. Water therefore is

ABSORPTION, DIFFUSION, OSMOSE. 21

drawn out of the cell-sap, but the substances in solution in the cell-sap do not
readily move out. As the bulk of the cell-sap diminishes the pressure from
the outside pushes the protoplasmic membrane away from the wall. Now
when we remove the salt solution and bathe the thread with water again, the
cell-sap, being a more highly concentrated solution than water, diffuses
with more difficulty and the diffusion current is inward, while the protoplasmic
membrane moves out against the cell wall, and turgidity again results. Also
in the experiments with salt and sugar solutions on the leaves of geranium, on
the leaves and stems of the seedlings, on the tissues and cells of the beet and
carrot, and on the root hairs of the seedlings, the same processes take place.

These experiments not only teach us that in the protoplasmic membrane, the
cell wall, and the cell-sap of plants do we have structures which are capable of
performing these physical processes, but they also show that these processes are
of the utmost importance to the plant ; not only in giving the plant the power
to take up solutions of nutriment from the soil, but they serve also other pur-
poses, as we shall see later.

CHAPTER III.

ABSORPTION OF LIQUID NUTRIMENT.

45. We are now ready to inquire how plants obtain food
from the soil . or water. Chemical analysis shows that certain
mineral substances are common constituents of plants. By
growing plants in different solutions of these various substances it
has been possible to determine what ones are necessary constitu-
ents of plant food. While the proportion of the mineral ele-
ments which enter into the composition of plant food may vary
considerably within certain limits, the concentration of the solu-
tions should not exceed certain limits. A very useful solution is
one recommended by Sachs, and is as follows :

46. Formula for solution of nutrient materials :

Water 1000 cc.

Potassium nitrate o. 5 gr.

Sodium chloride 0.5 "

Calcium sulphate o. <J "

Magnesium sulphate o. 5 "

Calcium phosphate o. 5 "

The calcium phosphate is only partly soluble. The solution which is not
in use should be kept in a dark cool place to prevent the growth of minute
algae.

47. Several different plants are useful for experiments in water cultures, as
peas, corn, beans, buckwheat, etc. The seeds of these plants may be germi-
nated, after soaking them for several hours in warm water, by placing them
between the folds of wet paper on shallow trays, or in the folds of wet cloth.
The seeds should not be kept immersed in water after they have imbibed
enough to thoroughly soak and swell them. At the same time that the seeds
are placed in damp paper or cloth for germination, one lot of the soaked seeds

22

ABSORPTION NUTRIMENT. 2$

should be planted in good soil and kept under the same temperature condi-
tions, for control. When the plants have germinated one series should be
grown in distilled water, which possesses no plant food; another in the nutrient
solution, and still another in the nutrient solution to which has been added a
few drops of a solution of iron chloride or ferrous sulphate. There would
then be four series of cultures which should be carried out with the same kind
of seed in each series so that the comparisons can be made on the same species
under the different conditions. The series should be numbered and recorded
as follows :

No. I, soil.

No. 2, distilled water.

No. 3, nutrient solution.

No. 4, nutrient solution with a few drops of iron solution added.

48. Small jars or wide-mouth bottles, or crockery jars, can be used for the
water cultures, and the cultures are set up as follows : A cork which will just
fit in the mouth of the bottle, or which can be supported by pins, is perforated
so that there is room to insert the seedling,

with the root projecting below into the liquid.
The seed can be fastened in position by insert-
ing a pin through one side, if it is a large one,
or in the case of small seeds a cloth of a coarse
mesh can be tied over the mouth of the bottle
instead of using the cork. After properly set-
ting up the experiments the cultures should be
arranged in a suitable place, and observed from
time to time during several weeks. In order to
obtain more satisfactory results several dupli-
cate series should be set up to guard against the
error which might arise from variation in indi-
vidual plants and from accident. Where there
are several students in a class, a single series
set up by several will act as checks upon one
another. If glass jars are used for the liquid Fig. 28.

cultures they should be wrapped with black Culture cylinder to show position of

' corn seedling < Hansen).

paper or cloth to exclude the light from the

liquid, otherwise numerous minute algae are apt to grow and interfere with the
experiment. Or the jars may be sunk in pots of earth to serve the same
purpose. If crockery jars are used they will not need covering.

49. For some time all the plants grow equally well, until the nutriment
stored in the seed is exhausted. The numbers I, 3 and 4, in soil and nutri-
ent solutions, should outstrip number 2, the plants in the distilled water.
No. 4 in the nutrient solution with iron, having a perfect food, compares favor-
ably with the plants in the soil.

24 PHYSIOLOGY.

50. Plants take liquid food from the soil. — From these ex-
periments then we judge that such plants take up the food they
receive from the soil in the form of a liquid, the elements being
in solution in water.

If we recur now to the experiments which were performed with
the salt solution in producing plasmolysis in the cells of spirogyra,
in the cells of the beet or corn, and in the root hairs of the corn
and bean seedlings, and the way in which these cells become tur-
gid again when the salt solution is removed and they are again
bathed with water, we will have an explanation of the way in
which plants take up nutrient solutions of food material through
their roots.

51. How food solutions are carried into the plant. — We can

Fig. 29.
Section of corn root, showing rhizoids formed from elongated epidermal cells.

see how the root hairs are able to take up solutions of plant food,
and we must next turn our attention to the way in which these

ABSORPTION NUTRIMENT. 2$

solutions are carried farther into the plant. We should make a
section across the root of a seedling in the region of the root
hairs and examine it with the aid of a microscope. We here see
that the root hairs are formed by the elongation of certain of the
surface cells of the root. These cells elongate perpendicularly to
the root, and become $mm to 6mm long. They are flexuous or
irregular in outline and cylindrical, as shown in fig. 29. The
end of the hair next the root fits in between the adjacent superfi-
cial cells of the root and joins closely to the next deeper layer of
cells. In studying the section of the young root we see that the
root is made up of cells which lie closely side by side, each with
its wall, its protoplasm and cell-sap, the protoplasmic membrane
lying on the inside of each cell wall.

52. In the absorption of the watery solutions of plant food by the root
hairs, the cell-sap, being a more concentrated solution, gains some of the
former, since the liquid of less concentration flows through the protoplasmic
membrane into the more concentrated cell-sap, increasing the bulk of the lat-
ter. This makes the root hairs turgid, and at the same time dilutes the cell-
sap so that the concentration is not so great. The cells of the root lying in-
side and close to the base of the root hairs have a cell-sap which is now more
concentrated than the diluted cell-sap of the hairs, and consequently gain
some of the food solutions from the latter, which tends to lessen the content
of the root hairs and also to increase the concentration of the cell-sap of the
same. This makes it possible for the root hairs to draw on the soil for more
of the food solutions, and thus, by a variation in the concentration of the sub-
stances in solution in the cell-sap of the different cells, the food solutions are
carried along until they reach the vascular bundles, through which the solu-
tions are carried to distant parts of the plant. Some believe that there is a
rhythmic action of the elastic cell walls in these cells between the root hairs and
the vascular bundles. This occurs in such a way that, after the cell becomes
turgid, it contracts, thus reducing the size of the cell and forcing some of the
food solutions into the adjacent cells, when by absorption of more food solu-
tions, or water, the cell increases in turgidity again. This rhythmic action of
the cells, if it does take place, would act as a pump to force the solutions
along, and would form one of the causes of root pressure.

53. How the root hairs get the watery solutions from the soil. — If we
examine the root hairs of a number of seedlings which are growing in the soil
under normal conditions, we shall see that a large quantity of soil readily
clings to the roots. We should note also that unless the soil has been recently
watered there is no free water in. it ; the soil is only moist. We are curious

26

PHYSIOLOGY.

to know how plants can obtain water from soil which is not wet. If we at-
tempt to wash off the soil from the roots, being careful not to break away the

Fig. 30.
Root hairs of corn seedling with soil particles adhering closely.

root hairs, we find that small particles cling so tenaciously to
the root hairs that they are not removed. Placing a few such

root hairs under the microscope it appears as if here and there the root hairs

were glued to the minute soil particles.

54. If now we take some of the soil which is only moist, weigh it, and
then permit it to become quite dry on exposure to dry air, and weigh again,
we will find that it loses weight in drying. Moisture has been given off.
This moisture, it has been found, forms an exceedingly thin film on the sur-
face of the minute soil particles. Where these soil particles lie closely to-
gether, as they usually do when massed together in the pot or elsewhere, this
thin film of moisture is continuous from the surface of one particle to that of an-
other. Thus the soil particles which are so closely attached to the root hairs
connect the surface of the root hairs with this film of moisture. As the cell-
sap of the root hairs draws on the moisture film with which they are in con-
tact, the tension of this film is sufficient to draw moisture from distant parti-
cles. Tn this way the roots are supplied with water in soil which is only
moist.

55. Plants cannot remove all the moisture from the soil. — If we now take
a potted plant, or a pot containing a number of seedlings, place it in a moder-
ately dry room, and do not add water to the soil it will be found in a few days
that the plant is wilting. The soil if examined will appear quite dry to the
sense of touch. Let us weigh some of this soil, then dry it by artificial

ABSORP7^ION NUTRIMENT. 2J

heat, and weigh again. It has lost in weight. This has been brought about
by driving off the moisture which still remained in the soil after the plant
began to wilt. This teaches that while plants can obtain water from soil
which is only moist or which is even rather dry, they are not able to withdraw
all the moisture from the soil.

56. Acidity of root hairs. — If we take a seedling which has
been grown in a germinator, or in the folds of cloths or paper,
so that the roots are free from the soil, and touch the moist root
hairs to blue litmus paper, the paper becomes red in color where
the root hairs have come in contact. This is the reaction for
the presence of an acid substance, and indicates that the root
hairs excrete certain acids. This acid property of the root hairs
serves a very important function in the preparation of certain
of the elements of plant food in the soil. Certain of the
chemical compounds of potash, phosphoric acid, etc., become
deposited on the soil particles, and are not soluble in water.
The acid of the root hairs dissolves some of these compounds
where the particles of soil are in close contact with them, and
the solutions can then be taken up by the roots.

57. This corrosive action of the roots can be shown by the well-known
experiment of growing a plant on a marble plate which is covered by soil.
After a few weeks, if the soil be washed from the marble where the roots
have been in close contact, there will be an outline of this part of the root
system. Several different acid substances are excreted from the roots of plants
which have been found to redden blue litmus paper by contact. Experiments
by Czapek, however, show that it is carbonic acid which has the power of
dissolving these compounds, while the other acids excreted by the roots do
not have this power.

CHAPTER IV.
TURGESCENCE.

58. Turgidity of plant parts. — As we have seen by the
experiments on the leaves, turgescence of the cells is one of the
conditions which enables the leaves to stand out from the stem,
and the lamina of the leaves to remain in an expanded position,
so that they are better exposed to the light, and to the currents
of air. Were it not for this turgidity the leaves would hang
down close against the stem.

59. Restoration of turgidity in shoots. — If we cut off a
living stem of geranium, coleus, tomato, or " balsam," and allow
the leaves to partly wilt so that the shoot loses its turgidity, it is
possible for this shoot to regain turgidity. The end may be
freshly cut again, placed in a vessel of water, covered with a bell

jar and kept in a room where the temperature
is suitable for the growth of the plant. The
shoot will usually become turgid again from
the water which is absorbed through the cut
end of the stem and is carried into the leaves
where the individual cells become turgid, and
the leaves are again expanded. Such shoots,
and the excised leaves also, may often be made
turgid again by simply immersing them in
water, as one of the experiments with the salt
solution would teach.

Fig. 3 i.
Restoration of turg'dity go. Turgidity may be restored more certainly and

quickly in a partially wilted shoot in another way.

The cut end of the shoot may be inserted in all tube as shown in fig. 31, the
end of the tube around the stem of the plant being made air-tight. The arm

28

TURGESCENCE. 2Q

of the tube in which the stem is inserted is filled with water and the water is
allowed to partly fill the other arm. Into this other arm is then poured
mercury. The greater weight of the mercury causes such pressure upon the
water that it is pushed into the stem, where it passes up through the vessels
in the stems and leaves, and is brought more quickly and surely to the cells
which contain the protoplasm and cell-sap, so that turgidity is more quickly
and certainly attained.

61. Tissue tensions. — Besides the turgescence of the cells of
the leaves and shoots there are certain tissue tensions without
which certain tender and succulent shoots, etc., would be limp,
and would droop. There are a number of plants usually accessi-
ble, some at one season and some at others, which may be used
to illustrate tissue tension.

62. Longitudinal tissue tension. — For this in early summer
one may use the young and succulent shoots of the elder
(sambucus); or the petioles of rhubarb during the summer and
early autumn ; or the petioles of richardia. Petioles of cala-
dium are excellent for this purpose, and these may be had at
almost any season of the year from the greenhouses, and are
thus especially advantageous for work during late autumn or
winter. The tension is so strong that a portion of such a
petiole 10— i$cm long is ample to demonstrate it. As we grasp
the lower end of the petiole of a caladium, or rhubarb leaf, we
observe how rigid it is, and how well it supports the heavy
expanded lamina of the leaf.

63. The ends of a portion of such a petiole or other object
which may be used are cut off squarely. With a knife a strip
from z—ynm in thickness is removed from one side the full
length of the object. This strip will now be found to be shorter
than the larger part from which it was removed. The outer
tissue then exerts a tension upon the petiole which tends to
shorten it. Let us remove another strip lying next this one,
and another, and so on until the outer tissues remain only upon
one side. The object will now bend toward that side. Now
remove this strip and compare the length of the strips removed
with the central portion. They will be found to be much

3O PHY SID LOG V.

shorter now. In other words there is also a tension in the tissue
of the central portion of the petiole, the direction of which is
opposite to that of the superficial tissue. The parts of the petiole
now are not rigid, and they easily bend. These two longitudi-
nal tissue tensions acting in opposition to each other therefore
give rigidity to the succulent shoot. It is only when the indi-
vidual cells of such shoots or petioles are turgid that these tissue
tensions in succulent shoots manifest themselves or are promi-
nent.

64. To demonstrate the efficiency of this tension in giving support, let us
take a long petiole of caladium or of rhubarb. Hold it by one end in a hori-
zontal position. It is firm and rigid, and does not droop, or but little. Re-
move all of the outer portion of the tissues, as described above, leaving only
the central portion. Now attempt to hold it in a horizontal position by one
end. It is flabby and droops downward because the longitudinal tension is
removed.

65. Transverse tissue tension. — To illustrate this one may
take a willow shoot $-$cm in diameter and saw off sections
about 2cm long. Cut through the bark on one side and peel it
off in a single strip. Now attempt to replace it. The bark will
not quite cover the wood again, since the ends will not meet. It
must then have been held in transverse tension by the woody
part of the shoot.

CHAPTER V.

ROOT PRESSURE.

66. It is a very common thing to note, when certain shrubs
or vines are pruned in the spring, the exudation of a watery
fluid from the cut surfaces. In the case of the grape vine this
has been known to continue for a number of days, and in some
cases the amount of liquid, called " sap," which escapes is con-
siderable. In many cases it is directly traceable to the activity
of the roots, or root hairs, in the absorption of water from the
soil. For this reason the term root pressure is used to denote
the force exerted in supplying the water from the soil.

67. Boot pressure may be measured. — It is possible to
measure not only the amount of water which the roots will raise
in a given time, but also to measure the force exerted by the
roots during root pressure. It has been found that root pressure
in the case of the nettle is sufficient to hold a column of water
about 4.5 meters(i5 ft.) high (Vines), while the root pressure of the
vine (Hales, 1721) will hold a column of water about 10 meters
(36.5 ft.) high, and the birch (Betula lutea) (Clark, 1873) has a
root pressure sufficient to hold a column of water about 25 meters
(84. 7 ft.) high.

68. Experiment to demonstrate root pressure. — By a very simple method
this power of root pressure may be demonstrated. During the summer season
plants in the open may be used if it is preferred, but plants grown in pots are
also very serviceable, and one may use a potted begonia or balsam, the latter
being especially useful. The plants are usually convenient to obtain from the
greenhouses, to illustrate this phenomenon. The stem is cut off rather close to
the soil and a long glass tube is attached to the cut end of the stem, still con-
nected with the roots, by tne use of rubber tubing as shown in figure 32, and a

31

PHYSIOLOGY.

very small quantity of water may be poured in to moisten the cut end of the
stem. In a few minutes the water begins to rise in the glass tube. In some
cases it rises quite rapidly, so that the column of water can
readily be seen to extend higher and higher up in the tube when
observed at quite short intervals. The height of this column
of water is a measure of the force exerted by the roots. The
pressure force of the roots may be measured also by deter-
mining the height to which it will raise a column of mercury.

69. In either case where the experiment is con-
tinued for several days it is noticed that the column
of water or of mercury rises and falls at different
times during the same day, that is, the column stands
at varying heights; or in other words the root
pressure varies during the day. With some plants
it has been found that the pressure is greatest at
certain times of the day, or at certain seasons of the
Fig 32 year. Such variation of root pressure exhibits what
Experiment to is termed a periodicity, and in the case of some

show root press-
ure (Detmer). plants there is a daily periodicity; while in others

there is in addition an annual periodicity. With the grape vine
the root pressure is greatest in the forenoon, and decreases from
12-6 P.M., while with the sunflower it is greatest before 10
A.M., when it begins to decrease. Temperature of the soil is
one of the most important external conditions affecting the
activity of root pressure.

CHAPTER VI.

TRANSPIRATION.

70. We should now inquire if all the water which is taken up
in excess of that which actually suffices for turgjdity is used in the
elaboration of new materials of construction. We notice when a
leaf or shoot is cut away from a plant, unless it is kept in quite
a moist condition, or in a damp, cool place, that it becomes flac-
cid, and droops. It wilts, as we say. The leaves and shoot
lose their turgidity. This fact suggests that there has been a
loss of water from the shoot or leaf. It can be readily seen that
this loss is not in the form of drops of water which issue from the
cut end of the shoot or petiole. What then becomes of the water
in the cut leaf or shoot ?

71. Loss of water from excised leaves. — Let us take a hand-
ful of fresh, green, rather succulent leaves, which are free from
water on the surface, and place them under a glass bell jar, which
is tightly closed below but which contains no water. Now we
will place this in a brightly lighted window, or in sunlight. In
the course of fifteen to thirty minutes we notice that a thin film
of moisture is accumulating on the inner surface of the glass jar.
After an hour or more the moisture has accumulated so that it
appears in the form of small drops of condensed water. We
should set up at the same time a bell jar in exactly the same way
but which contains no leaves. In this jar there will be no con-
densed moisture on the inner surface. We thus are justified in
concluding that the moisture in the former jar comes from the
leaves. Since there is no visible water on the surfaces of the
leaves, or at the cut ends, before it may have condensed there,

33

34

we infer that the water escapes from the leaves in the form of
wafer vapor, and that this water vapor, when it comes in contact
with the surface of the cold glass, condenses and forms the mois-
ture film, and later the drops of water. The leaves of these cut
shoots therefore lose water in the form of water vapor, and thus
a loss of turgidity results.

72. Loss of water from growing plants. — Suppose we now
take a small and actively growing plant in a pot, and cover the
pot and the soil with a sheet of rubber cloth which fits tightly
around the stem of the plant (or the pot and soil may be enclosed
in a hermetically sealed vessel) so that the moisture from the soil
cannot escape. Then place a bell jar over the plant, and set in
a brightly lighted place, at a temperature suitable for growth.
In the course of a few minutes on a dry day a moisture film forms
on the inner surface of the glass, just as it did in the case of the
glass jar containing the cut shoots and leaves. Later the mois-
ture has condensed so that it is in the form of drops. If we have
the same leaf surface here as we had with the cut shoots, we will
probably find that a larger amount of water accumulates on the
surface of the jar from the plant that is still attached to its
roots.

73. Water escapes from the surfaces of living leaves in the
form of water vapor. — This living plant then has lost water,
which also escapes in the form of water vapor. Since here there
are no cut places on the shoots or leaves, we infer that the loss
of water vapor takes place from the surfaces of the leaves and
from the shoots. It is also to be noted that, while this plant is
losing water from the surfaces of the leaves, it does not wilt or
lose its turgidity. The roots by their activity and pressure sup-
ply water to take the place of that which is given off in the form
of water vapor. This loss of water in the form of water vapor by
plants is transpiration.

74. Experiment to compare loss of water in a dry and a
humid atmosphere. — We should now compare the escape of
water from the leaves of a plant covered by a bell jar, as in the
last experiment, with that which takes place when the plant is

TRA NSP1RA TION. 3 5

exposed in a normal way in the air of the room or in the open.
To do this we should select two plants of the same kind growing
in pots, and of approximately the same leaf surface. The potted
plants are placed one each on the arms of a scale. One of the
plants is covered in this position with a bell jar.^ With weights
placed on the pan of the other arm the two sides are balanced.
In the course of an hour, if the.air of the room is dry, moisture
has probably accumulated on the inner surface of the glass jar
which is used to cover one of the plants. This indicates that
there has here been a loss of water. But there is no escape of
water vapor into the surrounding air so that the weight on this
arm is practically the same as at the beginning of the experiment.
We see, however, that the other arm of the balance has risen.
We infer that this is the result of the loss of water vapor from the
plant on that arm. Now let us remove the bell jar from the other
plant, and with a cloth wipe off all the moisture from the inner
surface, and replace the jar over the plant. We note that the
end of the scale which holds this plant is still lower than the
other end.

75. The loss of water is greater in a dry than in a humid
atmosphere. — This teaches us that while water vapor escaped
from the plant under the bell jar, the air in this receiver soon
became saturated with the moisture, and thus the farther escape
of moisture from the leaves was checked. It also teaches us an-
other very important fact, viz. , that plants lose water more rapidly
through their leaves in a dry air than in a humid or moist atmos-
phere, We can now understand why it is that during the very
hot and dry part of certain days plants often wilt, while at night-
fall, when the atmosphere is more humid, they revive. They lose
more water through their leaves during the dry part of the day,
other things being equal, than at other times.

76. How transpiration takes place. — Since the water of
transpiration passes off in the form of water vapor we are led to
inquire if this process is simply evaporation of water through the
surface of the leaves, or whether it is controlled to any appreci-
able extent by any condition of the living plant. An experiment

36 PHYSIOLOGY.

which is instructive in this respect we will find in a comparison
between the transpiration of water from the leaves of a cut shoot,
allowed to lie unprotected in a dry room, and a similar cut shoot
the leaves of which have been killed.

77. Almost any plant will answer for the experiment. For this purpose I
have used the following method. Small branches of the locust (Robinia
pseudacacia), of sweet clover (Melilotus alba), and of a heliopsis were
selected. One set of the shoots was immersed for a moment in hot water near
the boiling point to kill them. The other set was immersed for the same
length of time in cold water, so that the surfaces of the leaves might be well
wetted, and thus the two sets" of leaves at the beginning of the experiment
would be similar, so far as the amount of water on their surfaces is con-
cerned. All the shoots were then spread out on a table in a dry room, the
leaves of the killed shoots being separated where they are inclined to cling
together. In a short while all the water has evaporated from the surface of
the living leaves, while the leaves of the dead shoots are still wet on the sur-
face. In six hours the leaves of the dead shoots from which the surface
water had now evaporated were beginning to dry up, while the leaves of the
living plants were only becoming flaccid. In twenty-four hours the leaves
of the dead shoots were crisp and brittle, while those of the living shoots were
only wilted. In twenty-four hours more the leaves of the sweet clover and
of the heliopsis were still soft and flexible, showing that they still contained
more water than the killed shoots which had been crisp for more than a
day.

78. It must be then that during what is termed transpiration the living
plant is capable of holding back the water to some extent, which in a dead
plant would escape more rapidly by evaporation. It is also known that a
body of water with a surface equal to that of a given leaf surface of a plant
loses more water by evaporation during the same length of time than the
plant loses by transpiration.

79. Structure of a leaf. — We are now led to inquire why it is
that a living leaf loses water less rapidly than dead ones, and
why less water escapes from a given leaf surface than from an
equal surface of water. To understand this it will be necessary
to examine the minute structure of a leaf. For this purpose we
will select the leaf of an ivy, though many other leaves will
answer equally well. From a portion of the leaf we should make
very thin cross sections with a razor or other sharp instrument.
These sections should be perpendicular to the surface of the leaf

TRANSPIRA, TION.

37

and should be then mounted in water for microscopic examina-
tion.*

80. Epidermis of the leaf. — In this section we see that the
green part of the leaf is bordered on what are its upper and
lower surfaces by a row of cells which

possess no green color. The walls of
the cells of each row have nearly par-
allel sides, and the cross walls are per-
pendicular. These cells form a single
layer over both surfaces of the leaf and
are termed the epidermis. Their walls
are quite stout and the outer walls are
cuticularized.

81. Soft tissue of the leaf.— The
cells which contain the green chloro-
phyll bodies are arranged in two dif- , Flg: 3.3' ,

Section through ivy leaf showing

ferent Ways. Those On the Upper side communication between stomateand
•> the large intercellular spaces of the

of the leaf are usually long and pris- leaf ; stoma closed-
matic in form and lie closely parallel to each other. Because of
this arrangement of these cells they are termed the palisade cells,
and form what is called the palisade layer. The other green

cells, lying below,
vary greatly in size in
different plants and to
some extent also in the
same plant. Here we
notice that they are
elongated, or oval, or
somewhat irregular in
form. The most striking peculiarity, however, in their arrange-
ment is that they are not usually packed closely together, but each
cell touches the other adjacent cells only at certain points. This
arrangement of these cells forms quite large spaces between them,
the intercellular spaces. If we should examine such a section of
a leaf before it is mounted in water we would see that the inter-
* Demonstrations may be made with prepared sections of leaves.

Fig. 34- Fig- 35-

Stoma open. Stoma closed.

Figs. 34, 35.— Section through stomata of ivy leaf.

3 PHYSIOLOGY.

cellular spaces are not filled with water or cell-sap, but are filled
with air or some gas. Within the cells, on the other hand, we
find the cell-sap and the protoplasm.

82. Stomata. — If we examine carefully the row of epidermal
cells on the under surface of the leaf, we will find here and there
a peculiar arrangement of cells shown at figs. 33—35. This

opening
through the
e pi dermal
layer is a
sloma. The
cells which
immediately
surround the
op en ings -are

the guard
Fig. 36. *

Portion of epidermis of ivy, showing irregular epidermal cells, stoma C€llS.

and guard cells. /• r ii

form of the

guard cells can be better seen if we tear a leaf in such a way as
to strip off a short piece of the lower epidermis, and mount this
in water. The guard cells are nearly crescent shaped, and the
stoma is elliptical in outline. The epidermal cells are very
irregular in outline in this view. We should also note that while
the epidermal cells contain no chlorophyll, the guard cells do.

83. The living protoplasm retards the evaporation of water from the
leaf. — If we now take into consideration a few facts which we have learned
in a previous chapter, with reference to the physical properties of the living
cell, we will be able to give a partial explanation of the comparative slowness
with which the water escapes from the leaves. The inner surfaces of the cell
walls are lined with the membrane of protoplasm, and within this is the cell-
sap. These cells have become turgid by the absorption of the water which
has passed up to them from the roots. While the protoplasmic membrane of
the cells does not readily permit the water to filter through, yet it is saturated
with water, and the elastic cell wall with which it is in contact is also
saturated. From the cell wall the water evaporates into the intercellular
spaces. But the water is given up slowly through the protoplasmic mem-
brane so that the water vapor cannot be given off as rapidly from the cell
walls as it could if the protoplasm were dead. The living protoplasmic

TRANSPIKA TION.

39

membrane then which is only slowly permeable to the water of the cell-sap
is here a very important factor in checking the too rapid loss of water from
the leaves.

By an examination of our leaf section we see that the intercellular spaces
are all connected, and that the stomata, where they occur, open also into
intercellular spaces. There is here an opportunity for the water vapor in
the intercellular spaces to escape when the stomata are open.

84. Action of the stomata. — Besides permitting the escape of the water
vapor when the stomata are open they serve a very important office in regu-
lating the amount of transpiration. During normal transpiration the stomata
remain open, that is, when the amount of transpiration from the leaf is not
in excess of the supply of water to the leaves. But when the transpiration
from the leaves is in excess, as often lurppens, and the air becomes very dry,
the stomata close and thus the rapid transpiration is checked.

85. Transpiration may be in excess of root pressure. — If the supply of
water from the roots was always equal to that transpired from the leaves
during hot, dry days the leaves would not become flaccid and droop. But
during the hot and dry part of the day it often happens that the trans-
piration is in excess of the amount of water supplied the plant by root
pressure.

86. Negative pressure. — This is not only indicated by the drooping of
the leaves, but may be determined in another way. If the shoot of such a
plant be cut underneath mercury, or underneath a strong solution of eosin, it
will be found that some of the mercury or eosin, as the

case may be, will be forcibly drawn up into the stem
toward the roots. This is seen on quickly splitting the
cut end of the stem. When plants in the open cannot
be obtained in this condition, one may take a plant
like a balsam plant from the greenhouse, or some other
potted plant, knock it out of the pot, free the roots from
the soil and allow to partly wilt. The stem may then
be held under the eosin solution and cut.

87. Lifting power of transpiration.— Not only does
transpiration go on quite independently of root pressure,
as we have discovered from other experiments, but
transpiration is capable of exerting a lifting power on
the water in the plant. This may be demonstrated in
the following way: Place the cut end of a leafy shoot in
one end of a U tube and fit it water-tight. Partly
fill this arm of the U tube with water, and add mercury
to the other arm until it stands at a level in the two

arms as in fig. 37. In a short time we note that the mercury is rising in
the tube,

Fig. 37-

Experiment to show
lifting power of trans-
piration.

PHYSIOLOGY.

88. Boot pressure may exceed transpiration. — If we cover small actively
growing plants, such as the pea, corn, wheat, bean, etc., with a bell jar, and
place in the sunlight where the temperature is suitable for growth, in a few
hours, if conditions are favorable, we will see that there are drops of water
standing out on the margins of the leaves. These drops of
water have exuded through the ordinary stomata, or in other
cases what are called water stomata, through the influence of
root pressure. The plant being
1 ' covered by the glass jar, the air

Fig. 38.

soon becomes saturated with mois-

Estimation of the amount of ture and transpiration is checked.

SPiw±»a,eT,ha»db,esS K R«" P«*sure still goes on, how-
water transpires from the leaf ever, and the result is shown in
surface its movement in the tube
from a to /> can be measured, the exuding drops. Root pressure

is here in excess of transpiration.
This phenomenon is often to be observed during the summer season in the case
of low-growing plants. During the bright warm day transpiration equals,
or may be in excess of, root pressure, and the leaves are consequently
flaccid. As nightfall comes
on the air becomes more
moist, and the conditions
of light are such also that
transpiration is lessened.
Root pressure, however, is
still active because the soil
is still warm. In these cases
drops of water may be seen
exuding from the margins ol
the leaves due to the excess •[
of root pressure over trans- ^
piration. Were it not for I
this provision for the escape
of the excess of water raised
by root pressure, serious in-
jury by lesions, as a result
of the great pressure, might
result. The plant is thus to
some extent a self-regulatory
piece of apparatus so far as Fig. 39.

root pressure and transpira- Guttation of tomato plants after connecting the stems by
tion are concerned means of rubber tubes with the hydrant.

89. Injuries caused by excessive root pressure. — Some varieties of to-
matoes when grown in poorly lighted and poorly ventilated greenhouses suffer

TRA NSPTRA TION. 4 1

serious injury through lesions of the tissues. This is brought about by the
cells at certain parts becoming charged so full with water through the activity
of root pressure and lessened transpiration, assisted also probably by an ac-
cumulation of certain acids in the cell-sap which cannot be got rid of by
transpiration. Under these conditions some of the cells here swell out
forming extensive cushions, and the cell walls become so weakened that they
burst. It is possible to imitate the excess of root pressure in the case of some
plants by connecting the stems with a system of water pressure, when very
quickly the drops of water will begin to exude from the margins of the leaves.

90. It should be stated that in reality there is no difference between trans-
piration and evaporation, if we bear in mind that evaporation takes place
more slowly from living plants than from dead ones, or from an equal surface
of water.

91. The escape of water vapor is not the only function of the stomata.
The exchange of gases takes place through them as we shall later see. A
large number of experiments show that normally the stomata are open when
the leaves are turgid. But when plants lose excessive quantities of water on
dry and hot days, so that the leaves become flaccid, the guard cells automat-
ically close the stomata to check the escape of water vapor. Some water
escapes through the epidermis of many plants, though the circularized mem-
brane of the epidermis largely prevents evaporation. In arid regions plants
are usually provided with an epidermis of several layers of cells to more
securely prevent evaporation there. In such cases the guard cells are often
protected by being sunk deeply in the epidermal layer.

92. Demonstration of stomates and intercellular air spaces.— A good
demonstration of the presence of stomates in leaves, as well as the presence
and intercommunication of the intercellular spaces, can be made by blowing
into the cut end of the petiole of the leaf of a calla lily, the lamina being
immersed in water. The air is forced out through the stomata and rises as
bubbles to the surface of the water. At the close of the experiment some of
the air bubbles will still be in contact with the leaf surface at the opening of the
stomata. The pressure of the water gradually forces this back into the leaf.
Other plants will answer for the experiment, but some are more suitable than
others.

CHAPTER VII.
PATH OF MOVEMENT OF LIQUIDS IN PLANTS.

93. In our study of root pressure and transpiration we have
seen that large quantities of water or solutions move upward
through the stems of plants. We are now led to inquire
through what part of the stems the liquid passes in this upward
movement, or in other words, what is the path of the "sap" as
it rises in the stem. This we can readily see by the following
trial.

94. Place the cut ends of leafy shoots in a solution of some
of the red dyes. — We may cut off leafy shoots of various plants
and insert the cut ends in a vessel of water to which have been
added a few crystals of the dye known as fuchsin to make a deep
red color (other red dyes may be used, but this one is especially
good). If the study is made during the summer, the "touch-
me-not" (impatiens) will be found a very useful plant, or the
garden -balsam, which may also be had in the winter from con-
servatories. Almost any plant will do, however, but we should
also select one like the corn plant (zea mays) if in the summer,
or the petioles of a plant like caladium, which can be obtained
from the conservatory. If seedlings of the castor-oil bean are at
hand we may cut off some shoots which are 8— 10 inches high,
and place them in the solution also.

95. These solutions color the tracts in the stem and leaves
through which they flow. — After a few hours in the case of the
impatiens, or the more tender plants, we can see through the
stem that certain tracts are colored red by the solution, and
after 12 to 24 hours there may be seen a red coloration of the

42

PATH OF MOVEMENT. 43

leaves of some of the plants used. After the shoots have been
standing in the solution for a few hours, if we cut them at
various places we will note that there are several points in the
section where the tissues are colored red. In the impatiens
perhaps from four to five, in the sunflower a larger number. In
these plants the colored areas on a cross section of the stem are
situated in a concentric ring which separates more or less com-
pletely an outer ring of the stem from the central portion. If
we now split portions of the stem lengthwise we see that these
colored areas continue throughout the length of the stem, in some
cases even up to the leaves and into them.

96. If we cut across the stem of a corn plant which has been
in the solution, we see that instead of the colored areas being in
a concentric ring they are irregularly scattered, and on splitting

Fig. 40.
Broken corn stalk, showing nbro-vascular bundles.

the stem we see here also that these colored areas extend for long
distances through the stem. If we take a corn stem which is
mature, or an old and dead one, cut around through the outer
hard tissues, and then break the stem at this point, from the
softer tissue long strings of tissue will pull out as shown in fig.
40. These strings of denser tissue correspond to the areas
which are colored by the dye. They are in the form of minute
bundles, and are called vascular bundles.

44

PHYSIOLOG V.

97. We thus see that instead of the liquids passing through
the entire stem they are confined to definite courses. Now that
we have discovered the path of the upward movement of water
in the stem, we are curious to see what the structure of these
definite portions of the stem is.

98. Structure of the fibro-vascular bundles. — We should now make quite
thin cross sections, either free hand and mount in water for microscopic
examination, or they may be made with a microtome and mounted in Canada
balsam, and in this condition will answer for future study. To illustrate the
structure of the bundle in one type we may take the stem of the castor-oil
bean. On examining these cross sections we see that there are groups of
cells which are denser than the ground tissue. These groups correspond to
the colored areas in the former experiments, and are the vascular bundles

Xylem portion of bundle.

Fig. 41.

ime. Cambium portion of bundle.

Section of vascular bundle of sunflower stei

Bast portion of bundle.

cut across. These groups are somewhat oval in outline, with the pointed
end directed toward the center of the stem. If we look at the section as a
whole we will see that there is a narrow continuous ring * of small cells

* This ring and the bundles separate the stem into two regions, an outer
one composed of large cells with thin walls, known as the cortical cells, or
collectively the cortex. The inner portion, corresponding to what is called
the pith, is made up of the same kind of cells and is called the medulla, or
pith. When the cells of the cortex/as well as of the pith, remain thin walled
the tissue is called parenchyma. Parenchyma belongs to the group of
tissues called fundamental.

PATH OF MOVEMENT. 45

situated at the same distance from the center of the stem as the middle part
of the bundles, and that it divides the bundles into two groups of cells.

99. Woody portion of the bundle. — In that portion of the bundle on the
inside' of the ring, i.e., toward the "pith," we note large, circular, or angu-
lar cavities. The walls of these cells are quite thick and woody. They are
therefore called wood cells, and because they are continuous with cells above
and below them in the stem in such a way that long tubes are formed, they
are called woody vessels. Mixed in with these are smaller cells, some of
which also have thick walls and are wood cells. Some of these cells may
have thin walls. This is the case with all when they are young, and they
are then classed with the fundamental tissue or soft tissue (parenchyma).
This part of the bundle, since it contains woody vessels and fibres, is the
wood portion of the bundle, or technically the xylem.

100. Bast portion of the bundle. — If our section is through a part of the
stem which is not too young, the tissues of the outer part of the bundle will
show either one or several groups of cells which have white and shiny walls,
that are thickened as much or more than those of the wood vessels. These
cells are bast cells, and for this reason this part of the bundle is the bast por-
tion, or the phloem. Intermingled with these, cells may often be found which
have thin walls, unless the bundle is very old. Nearer the center of the
bundle and still within the bast portion are cells with thin walls, angular and
irregularly arranged. This is the softer portion of the bast, and some of
these cells are what are called sieve tubes, which can be better seen and
studied in a longitudinal section of the stem.

101. Cambium region of the bundle. — Extending across the center of the
bundle are several rows of small cells, the smallest of the bundle, and we can
see that they are more regularly arranged, usually in quite regular rows,
like bricks piled upon one another. These cells have thinner walls than any
others of the bundle, and they usually take a deeper stain when treated
with a solution of some of the dyes. This is because they are younger, and
are therefore richer in protoplasmic contents. This zone of young cells
across the bundle is the cambium. Its cells grow and divide, and thus increase
the size of the bundle. By this increase in the number of the cells of the
cambium layer, the outermost cells on either side are continually passing
over into the phloem, on the one hand, and into the wood portion of the
bundle, on the other hand.

102. Longitudinal section of the bundle. — If we make thin longisections of
the vascular bundle of the castor-oil seedling (or other dicotyledon) so that we
have thin ones running through a bundle radially, as shown in fig. 42, we
can see the structure of these parts of the bundle in side view. We see here
that the form of the cells is very different from what is presented in a cross
section of the same. The walls of the various ducts have peculiar markings
on them. These markings are caused by the walls being thicker in some

PHYSIO LOG Y.

places than in others, and this thickening takes place so regularly in some
instances as to form regular spiral thickenings. Others have the thickenings

9

)
* ,

>ife

9 K

Fig. 42.

Longitudinal section of vascular bundle of sunflower stem ; spiral, scalariform and pitted
vessels at left ; next are wood fibers with oblique cross walls ; in middle are cambium cells
with straight cross walls, next two sieve tubes, then phloem or bast cells.

in the form of the rounds of a ladder, while still others have pitted walls or the
thickenings are in the form of rings.

103. Vessels or ducts. — One way in which the cells in side view differ
greatly from an end view, in a cross section in the bundle, is that they are
much longer in the direction of the axis of the stem. The cells have become
elongated greatly. If we search for the place where two of these large cells
with spiral, or ladder-like, markings meet end to end, we will see that the
wall which formerly separated the cells has nearly or quite disappeared. In
other words the two cells have now an open communication at the ends.
This is so for long distances in the stem, so that long columns of these large
cells form 'tubes or vessels through which the water rises in the stems of
plants.

104. In the bast portion of the bundle we detect the cells of the bast fibers
by their thick walls. They are very much elongated and the ends taper out to
thin points so that they overlap. In this way they serve to strengthen the stem-

105. Sieve tubes. — Lying near the bast cells, usually toward the cambium,
are elongated cells standing end to end, with delicate markings on their cross
walls which appear like finely punctured plates or sieves. The protoplasm
in such cells is usually quite distinct, and sometimes contracted away from
the side walls, but attached to the cross walls, and this aids in the detection
of the sieve tubes (fig. 42.) The granular appearance which these plates pre-
sent is caused by minute perforations through the wall so that there is a com-
munication between the cells. The tubes thus formed are therefore called
sieve tubes and they extend for long distances through the tube so that there

PATH OF MOVEMENT.

47

is communication throughout the entire length of the stem. (The function of
the sieve tubes is supposed to be that for the downward transportation of sub-
stances elaborated in the leaves.)

106. If we section in like manner the stem of the sunflower we shall see simi-
lar bundles, but the number is greater than eight. In the garden balsam the
number is from four to six in an ordinary stem ^-\mm diameter. Here we
can see quite well the origin of the vascular bundle. Between the larger
bundles we can see especially in free-hand sections of stems through which
a colored solution has been lifted by transpiration, as in our former experi-
ments, small groups of the minute cells in the cambial ring which are colored.
These groups of cells which form strands running through the stem are pro-
cambium strands. The cells divide and increase just like the cambium cells,
and the older ones thrown off on either side change, those toward the center
of the stem to wood vessels and fibers, and those on the outer side to bast
cells and sieve tubes.

107. Fibrovascular bundles in the Indian corn. — We should now make
a thin transection of a portion of the center of the stem of Indian corn, in
order to compare the structure of the

bundle with that of the plants which we
have just examined. In fig. 43 is repre-
sented a fibrovascular bundle of the stem
of the Indian corn. The large cells are
those of the spiral and reticulated and
annular vessels. This is the woody por-
tion of the bundle or xylem. Opposite
this is the bast portion or phloem, marked
by the lighter colored tissue at i. The
larger of these cells are the sieve tubes,
and intermingled with them are smaller
cells with thin walls. Surrounding the
entire bundle are small cells with thick
walls. These are elongated and the taper-
ing ends overlap. They are thus slender
and long and form fibers. In such a

bundle all of the cambium has passed vessel ;"r annular vessel; /, air cavity

r . formed by breaking apart of the cells ; /,

over into permanent tissue and is said to £0ft bast, a form of sieve tissue ; /, thin-
, , , walled parenchyma. (Sachs.)

108. Eise of water in the vessels. — During the movement of the water or
nutrient solutions upward in the stem the vessels of the wood portion of the
bundle in certain plants are nearly or quite filled, if root pressure is active
and transpiration is not very rapid. If, however, on dry days transpiration
is in excess of root pressure, as often happens, the vessels are not filled with
the water, but are partly filled with certain gases because the air or other

Fig. 43-

Transection of fibrovascular bundle of
Indian corn. a, toward periphery of
stem ; g, large pitted vessels ; s, spiral

48

PHYSIOLOGY.

gases in the plant become rarefied as a result of the excessive loss of water.
There are then successive rows of air or gas bubbles in the vessels separated
by films of water which also line the walls of the vessels. The condition of
the vessel is much like that of a glass tube through which one might pass the
"froth " \vhich is formed on the surface of soapy water. This forms a chain
of bubbles in the vessels. This chain has been called Jamin's chain because
of the discoverer.

109 Why water or food solutions can be raised by the plant to the height
attained by some trees has never been satisfactorily explained. There are
several theories propounded which cannot be discussed here. It is probably
a very complex process. Root pressure and transpiration both play a part,
or at least can be shown, as we have seen, to be capable of lifting water to a
considerable height. In addition to this, the walls of the vessels absorb water
by diffusion, and in the small vessels capillarity comes also into play, as
well as osmosis.

110. Synopsis of tissues.
Epidermis.

Epidermal
system.

Trichomes
(hairs).

Fibrovascular
system.

Xylem.

Phloem.

Fundamental
system.

Simple hairs.
Many-celled hairs.
Branched hairs, often stellate.
Clustered, tufted hairs.
Glandular hairs.
Root hairs.
Guard cells of stomates.
Spiral vessels.
Pitted vessels.
Scalariform vessels.
Annular vessels.
Wood fibers.
Wood parenchyma.
Cambium (fascicular).
f Sieve tubes.
Bast fibers.
Bast parenchyma.
Cork.
Parenchyma.

Ground tissue.
Interfascicular cambium.
Medullary rays.
Bundle sheath.

Schlerenchyma (thick-walled cells, in nuts. etc). Collen-
chyma (thick-angled cells, under epidermis of succulent
stems).

CHAPTER VIII.

DIFFUSION OF GASES.

111. Gas given off by* green plants in the sunlight. — Let

us take some green alga, like spirogyra, which is in a fresh con-
dition, and place one lot in a beaker or tall glass vessel of water
and set this in the direct sunlight or in a well lighted place. At
the same time cover a similar vessel
with spirogyra with black cloth so that
it will be in the dark, or at least in
very weak light.

112. In a short time we note that in
the first vessel small bubbles of gas are
accumulating on the surface of the
threads of the spirogyra, and now and
then some free themselves and rise to
the surface of the water. Where there
is quite a tangle of the threads the gas
is apt to become caught and held back
in larger bubbles, which on agitation of

the vessel are freed. Fig. 44.

If we now examine the Second vessel Oxygen gas given off by spirogyra.

we see that there are no bubbles, or only a very few of them.
We are led to believe then that sunlight has had something to
do with the setting free of this gas from the plant.

113. We may now take another alga like vaucheria and per-
form the experiment in the same way, or to save time the
two may be set up at once. In fact if we take any of the green

49

50 PHYSIO LOG Y.

algae and treat them as described above gas will be given off in a
similar manner.

114. We may now take one of the higher green plants, an
aquatic plant like elodea, callitriche, etc. Place the plant in
the water with the cut end of the stem uppermost,
but still immersed, the plant being weighted down
by a glass rod or other suitable object. If we
place the vessel ot water containing these leafy
stems in the bright sunlight, in a short time bub-
bles of gas will pass off quite rapidly from the cut
end of the stem. If in the same vessel we
place another stem? from which the leaves
have been cut, the number of bubbles of gas

Bubble*^ oxygen gas &Ve* °ff WU1 bC ^^ few' Tm'S indicatCS that

p!SI!nc? frofm stSSilh" a large part of the gas is furnisned by the
<0ela-) ' ' leaves.

115. Another vessel fitted up in the same way should be placed in the
dark or shaded by covering with a box or black cloth. It will be seen here,
as in the case of spirogyra, that very few or no bubbles of gas will be set
free. Sunlight here also is necessary for the rapid escape of the gas.

116. We may easily compare the rapidity with which light of varying
intensity effects the setting free of this gas. After cutting the end of the stem
let us plunge the cut surface several times in melted paraffine, or spread
over the cut surface a coat of varnish. Then prick with a needle a small
hole through the paraffine or varnish. Immerse the plant in water and
place in sunlight as before. The gas now comes from the puncture through
the coating of the cut end, and the number of bubbles given off during a
given period can be ascertained by counting. If we duplicate this experi-
ment by placing one plant in weak light or diffused sunlight, and another in
the shade, we can easily compare the rapidity of the escape of the gas under
the different conditions, which represent varying intensities of light. We
see then that not only is sunlight necessary for the setting free of this gas, but
that in diffused light or in the shade the activity of the plant in this respect
is less than in direct sunlight.

117. What this gas is. — If we take quite a quantity of the
plants of elodea and place them under an inverted funnel
which is immersed in water, the gas will be given off in quite
large quantities and will rise into the narrow exitoi the funnel.

DIFFUSION OF GASES. 51

The funnel should be one with a short tube, or the vessel one
which is quite deep so that a small test tube which is filled with
water may in this condition be inverted over the
opening of the funnel tube. With this arrange-
ment of the experiment the gas will rise in the
inverted test tube, slowly displace a portion of
the water, and become collected in a sufficient
quantity to afford us a test. When a consider-
able quantity has accumulated in the test tube, we
may close the end of the tube in the water with
the thumb, lift it from the water and invert. Fig- 46-

Apparatus for col-

The gas will rise against the thumb. A dry lecting quantity of

oxygen from elodea.

soft pine splinter should be then lighted, and (Detmer.)
after it has burned a short time, extinguish the flame by blowing
upon it, when the still burning end of the splinter should be
brought to the mouth of the tube as the thumb is quickly moved
to one side. The glowing of the splinter shows that the gas is
oxygen.

118. Oxygen given off by green land plants also. — If we should extend
our experiments to land plants we would find that oxygen is given off by
them under these conditions of light. Land plants, however, will not do
this when they are immersed in water, but it is necessary to set up rather
complicated apparatus and to make analyses of the gases at the beginning
and at the close of the experiments. This has been done, however, in a suffi-
ciently large number of cases so that we know that all green plants in the
sunlight, if temperature and other conditions are favorable, give off oxygen.

119. Absorption of carbon dioxide. — We have next to inquire
where the oxygen comes from which is given off by green plants
when exposed to the sunlight, and also to learn something more
of the conditions necessary for the process. We know that
water which has been for some time exposed to the air and soil,
and has been agitated, like running water of streams, or the
water of springs, has mixed with it a considerable quantity of
oxygen and carbon dioxide.

120. If we boil spring water or hydrant water which comes
from a stream containing oxygen and carbon dioxide, for about 20

52 PHYSIOLOGY.

minutes, these gases are driven off. We should set this aside
where it will not be agitated, until it has cooled sufficiently to
receive plants without injury. Let us now place some spirogyra
or vaucheria, and elodea, or other green water plant, in this
boiled water and set the vessel in the bright sunlight under the
same conditions which were employed in the experiments for the
evolution of oxygen. No oxygen is given off.

121. Can it be that this is because the oxygen was driven
from the water in boiling ? We will see. Let us take the vessel
containing the water, or some other boiled water, and agitate it
so that the air will be thoroughly mixed with it. In this way
oxygen is again mixed with the water. Now place the plant
again in the water, set in the sunlight, and in several minutes
observe the result. No oxygen is given off. There must be
then some other requisite for the evolution of the oxygen.

122. The gases are interchanged in the plants. — We will
now introduce carbon dioxide again in the water. This can be
done by blowing into the water through a glass tube in such a
manner as to violently agitate the water for some time, when the
carbon dioxide from the "breath" will become mixed with the
water. Now if we place the plant in the water and set the vessel
in the sunlight, in a few minutes the oxygen is given off rapidly.

123. A chemical change of the gas takes place within the
plant cell. — This leads us to believe then that CO2 is in some
way necessary for the plant in this process. Since oxygen is
given off while carbon dioxide, a different gas, is necessary, it
would seem that a chemical change takes place in the gases
within the plant. Since the process takes place in such simple
plants as spirogyra as well as in the more bulky and higher
plants, it appears that the changes go on within the cell, in fact
within the protoplasm.

124. Gases as well as water can diffuse through the proto-
plasmic membrane. — Carbon dioxide then is absorbed by the
plant while oxygen is given off. We see therefore that gases as
well as water can diffuse through the protoplasmic membrane of
plants under certain conditions.

DIFFUSION OF GASES. 53

125. Note. If we kill the plant, for example, by placing it for a short time in
nearly boiling water, oxygen will not be given off when the plant is placed in
the sunlight in water. In other words the plant must be alive. Farther, if
we introduce CO2 in the water by blowing into it and have not introduced
oxygen, oxygen will not be evolved. Not only must the plant be alive, it
must have access to oxygen, which we will see later is very essential to the
continuance of one of the important life processes.

CHAPTER IX.

RESPI RATION.

126. One of the life processes in plants which is extremely
interesting, and which is exactly the same as one of the life pro-
cesses of animals, is easily demonstrated in several ways.

127. Oxygen from the air consumed during germination of
seeds. — Let us take a half pint or a pint of peas, tie them in a

bag or loose cloth, soak them in warm water
for 10 or 12 hours, or in cool water for about
24 hours. Drain off the surplus water and lower
the cloth with the peas in a tall glass cylinder
which holds i to 2 liters. This should be
covered with a glass plate after vaseline has
been smeared on the edges of the cylinder to
make the vessel air tight. Set aside in a warm
room for about 12 hours. Now lower alighted
taper or short candle into the vessel after having
carefully removed the cover. The flame is
Fig- 47- extinguished. This indicates that there is no

lest for presence of

carbon dioxide in vessel OXygen in the Vessel,
with germinating peas. J &

128. Carbon dioxide given off during ger-
mination.— Now let us lower a small vessel containing lime water
into it. Very soon, almost immediately, there is formed on the
surface of the lime water a film. The film formed under these
conditions is known to be carbonate of lime, which is formed by
the union of carbon dioxide in the vessel with the iime in the
water. (Note. Where there are a number of students and large
vessels are not at hand, bottles of a pint capacity and a smaller
number of peas will answer. )

54

R ESP IRA riON. 5 5

129. If we now take some of the lime water and blow our
"breath " upon it the same film will be formed. The carbon
dioxide which we exhale unites with the lime in the water, and
forms carbonate of lime, just as in the case of the peas. In the
case of animals the process by which oxygen is taken into the
body and carbon dioxide is given off is respiration. The process
in plants which we are now studying is the same, and also is
respiration. The oxygen in the vessel was used up in the proc-
ess, and carbon dioxide was given off. (It will be seen that
this process is exactly the opposite of that which takes place in
carbon conversion. )

130. Inspiration is necessary for growth. — After we have performed this
experiment, if the vessel has not been open too long so that oxygen has en-
tered, we may use the vessel for another experiment, or set up a new one to
be used in the course of 12 to 24 hours, after all the oxygen has been con-
sumed. Place some folded damp filter paper on the germinating peas in the
jar. Upon this place one-half dozen peas which have just been germinated,
and in which the roots are about 20-25 mm long. The vessel should be cov-
ered tightly again and set aside in a warm room.

A second jar with water in the bottom instead
of the germinating peas should be set up as a
check. Damp folded filter paper should be sup-
ported above the water, and on this should be
placed one-half dozen peas with roots of the
same length as those in the jar containing carbon
dioxide.

131. In 24 hours examine and note how much Fig. 48.

growth has taken place. It will be seen that the Pea seedlings; the one

at the left had no oxygen
roots have elongated but very little or none in the and little growth took

first jar, while in the second one we see that the

roots have elongated considerably, if the experi- evident.

ment has been carried on carefully. Therefore

in an atmosphere devoid of oxygen very little growth will take place, which

shows that normal respiration with access of oxygen is necessary for growth.

132. Energy set free during respiration. — From what we have learned of
the exchange of gases during respiration we infer that the plant loses carbon
during this process. If the process of respiration is of any benefit to the
plant, there must be some gain in some direction to compensate the plant for
the loss of carbon which takes place.

It can be shown by an experiment that during respiration there is a
slight elevation of the temperature in the plant tissues. The plant then

56 PHYSIGLOG v.

gains some heat during respiration. We have also seen in the attempt to
grow seedlings in the absence of oxygen that very little growth takes place.
But when oxygen is admitted growth takes place rapidly. The process of
respiration, then, also sets free energy which is manifested in one direction,
by growth.

133. Respiration in a leafy plant. — We may take a potted plant which
has a well-developed leaf surface and place it under a tightly fitting bell jar.

Under the bell jar there also should be placed a
small vessel containing lime water. A similar ap-
paratus should be set up, but with no plant, to serve
as a check. The experiment must be set up in a
room which is not frequented by persons, or the
carbon dioxide in the room from respiration will
vitiate the experiment. The bell jar containing the
plant should be covered with a black cloth to pre-
vent carbon assimilation. In the course of ten or

twelve hours, if everything has worked properly, the
Test for liberation of car-
bon dioxide from leafy plant lime water under the jar with the plant will show the
during respiration. Baryta r, f , £ ,. , ., ., , ...

water in smaller vessel. «'m °* carbonate of lime, while the other one will

(Sachs.) show none. Respiration, therefore, takes place in

a leafy plant as well as in germinating seeds.

134. Respiration in fungi. — If several large actively growing mushrooms
are accessible, place them in a tall glass jar as described for determining
respiration in germinating peas. In the course of twelve hours test with the
lighted taper and the lime water. Respiration takes place in fungi as well
as in green plants.

135. Respiration in plants in general. — Respiration is general in all
plants, though not universal. There are some exceptions in the lower plants,
notably in certain of the bacteria, which can only grow and thrive in the ab-
sence of oxygen.

136. Respiration a breaking-down process. — We have seen that in res-
piration the plant absorbs oxygen and gives off carbon dioxide. We should
endeavor to note some of the effects of respiration on the plant. Let us
take, say, two dozen dry peas, weigh them, soak for 12-24 hours in water,
and, in the folds of a cloth kept moist by covering with wet paper or sphag-
num, germinate them. When well germinated and before the green color
appears dry well in the sun, or with artificial heat, being careful not to burn
or scorch them. The aim should be to get them about as dry as the seed
were before germination. Now weigh. The germinated seeds weigh less
than the dry peas. There has then been a loss of plant substance during
respiration.

137. Detailed result of the above experiment to show that respiration is
necessary for growth. — The experiment was started at 9.30 A.M. on July

R ESP IRA TION.

57

8, and the roots measured 20-25 ww. At 3 P.M. on the following day,
29 hours after the experiment was started, the roots were examined. Those
in the CO2 gas had not grown perceptibly, while those in the jar containing
air had increased in length lo-zomm. In fig. 48 arc represented two of the
peas, drawn at the close of the experiment, a represents the one from the
CO3 jar which had the longest root, b represents one of the longer ones from
the jar with air. Here we have also a good comparison with the peas
grown in the mercury tubes, since those in the tube which contained some
air were checked in growth to a considerable extent, by the accumulation of
carbon dioxide in the small space in the tube, and did not represent a fair
comparison of root growth in air and in CO..

138. Another way of performing the experiment. — If we wish we may
use the following experiment instead of the simple one indicated above. Soak
a handful of peas in water for 12-24
hours, and germinate so that twelve
with the radicles 2Q-2$mm long
may be selected. Fill a test tube
with mercury and carefully invert
it in a vessel of mercury so that
there will be no air in the upper end
(there may be a small vacuum).
Now nearly fill another tube and
invert in the same way. In the
latter there will be some air. Re-
move the outer coats from the peas
so that no air will be introduced in
the tube filled with the mercury,
and insert them one at a time under
the edge of the tube beneath the
mercury, six in each tube, having
first measured the length of the
radicles. Place in a warm room.
In 24 hours measure the roots.
Those in the air will have grown
considerably, while those in the

other tube will
little or none.

Fig. 50.

Experiment to show that growth takes place
more rapidly in presence of oxygen than in ab-
sence of oxygen. At the beginning of the experi-
ment the two tubes in the vessel represent the
condition at the beginning of the experiment.
At the close the roots in the tube at the left were
longer than those in the tube filled at the start

have grown but with mercury. The tube outside of the vessel
represents the condition of things where the peas
grew in absence of oxygen ; the carbon dioxide

.-P., eiven off has displaced a portion of the mercury.

The apparatus to demonstrate ^^Q ^intramolecular respiration.

this was set up at 10 A.M. on July

8, 1897. The tube filled with mercury was supported by a clamp, while
the tube which was only partly filled was stable enough to support itself
until by the accumulation of gas nearly all the mercury moved out, when
it was weighted clown,

5& PHYSIOLOGY.

The twelve peas were selected so that six for each lot showed the same
length of root, which varied from 15 to 25 mm long. Fig. 50 shows the
apparatus just after the experiment was started. The. peas in tube a (the
right-hand tube) are nearly hidden by the mercury.

At 2 P.M. the accumulation of gas had caused the lowering of the
mercury in this tube so that the upper pea was entirely uncovered. At 4
P.M. another pea was uncovered. By this time it was evident that the roots
of the peas in tube b (left-hand one) were elongating, while no increase could
be detected in the roots of the peas in a. At 6 P.M. three peas in a were
uncovered. At 10 P.M. all six peas were uncovered. The roots of the peas
in b were still longer than when noted at 4 P.M., but in a no elongation was
perceptible at that time. At 9 A.M. on the following day the mercury had
lowered so that it was nearly level with the mercury in the dish, while that
in tube b was below the level of that in the dish. There was no perceptible
elongation of the roots in a, while the roots in b measured about 5 mm
longer than when the experiment was started.

139. Intramolecular respiration. — The last experiment is also an excel-
lent one to show what is called intramolecular respiration. In the tube filled
with mercury so that when inverted there will be no air, it will be seen after
24 hours that a gas has accumulated in the tube which has crowded out some
of the mercury. With a wash bottle which has an exit tube properly curved,
some water may be introduced in the tube. Then insert underneath a small
stick of caustic potash. This will form a solution of potash and the gas will
be partly or completely absorbed. This shows that the gas was carbon
dioxide. This evolution of carbon dioxide by living plants when there is no
access of oxygen is called intramolecular respiration. It occurs markedly in
oily seeds and especially in the yeast plant.

CHAPTER X.

THE CARBON FOOD OF PLANTS.

140. We came to the conclusion in a former chapter that
some chemical change took place within the protoplasm of the
green cells of plants during the absorption of carbon dioxide
and the giving off of oxygen. We should examine some of the
green parts of those plants used in the experiments, or if they are
not at hand we should set up others in order to make this ex-
amination.

141. Starch formed as a result of carbon conversion. — We
may take spirogyra which has been standing in water in the
bright sunlight for several hours. A few of the threads should
be placed in alcohol for a short time to kill the protoplasm.
From the alcohol we transfer the threads to a solution of iodine
in potassium iodide. We will find that at certain points in the
chlorophyll band a bluish tinge, or color, is imparted to the ring
or sphere which surrounds the pyrenoid. In our first study of
the spirogyra cell we noted this sphere as being composed of
numerous small grains of starch which surround the pyrenoid.

142. Iodine used as a test for starch. — This color reaction
which we have obtained in treating the threads with iodine is
the well-known reaction, or test, for starch. We have demon-
strated then that starch is present in spirogyra threads which
have stood in the sunlight with free access to carbon dioxide.

If we examine in the same way some threads which have stood in
the dark for a day we will get no reaction for starch, or at best
only a slight reaction. This gives us some evidence that a
chemical change does take place during this process (absorption

59

60 PHYSIOLOGY.

of CO, and giving off of oxygen), and that starch is a product of
that chemical change.

143. Schimper's method of testing for the presence of starch.

— Another convenient and quick method of testing for the pres-
ence of starch is what is known as Schimper's method. A
strong solution of chloral hydrate is made by taking 8 grams of
chloral hydrate for every $cc of water. To this solution is
added a little of an alcholic tincture of iodine. The threads of
spirogyra may be placed directly in this solution, and -in a few
moments mounted in water on the glass slip and examined with
the microscope. The reaction is strong and easily seen.

144. We may test vaucheria which has been grown under like
conditions in the same way. We find here also that the starch
is present in the threads which have been exposed to the sun-
light, while it is absent from those which have been for a suffi-
ciently long time in the dark.

145. We should also examine the leaves of elodea, or one of
the higher green plants which has been for some time in the
sunlight. We may use here Schimper's method by placing the
leaves directly in the solution of chloral hydrate and iodine.
The leaves are made transparent by the chloral hydrate so that
the starch reaction from the iodine is easily detected.

146 If we wish to use the potassium iodide of iodine the leaves should be
first boiled for a short time in water, then heated for some time in alcohol, or
the alcohol changed several times. The green color is extracted slowly by
this process, and will be hastened if the preparation is placed in the sunlight.
(If care is used the leaves may be boiled in alcohol.) After the leaves are
decolorized they should be immersed in the potassium iodide of iodine.

147. Green parts of plants form starch when exposed to
light. — Thus we find that in the case of all the green plants we
have examined, starch is present in the green cells of those which
have been standing for some time in the sunlight where the proc-
ess of the absorption of COa and the giving off of oxygen can
go on, and that in the case of plants grown in the dark, or in
leaves of plants which have stood for some time in the dark,
starch is absent. We reason from this that starch is the product

CARBON FOOD OF PLANTS. 6 1

of the chemical change which takes place in the green cells
under these conditions. Because CO2 is absorbed during this
process, and because of the chemical changes which take place
in the formation of starch, by means of which the carbon is
changed from its attraction in the molecule of carbon dioxide to
its attraction in the molecule of starch, the process may be
termed carbon conversion.

This process has been termed carbon assimilation, but since it is not truly
an assimilatory process, and because sunlight is necessary in the first step
of the conversion, it has also been recently termed photosyntax, or photo-
synthesis. These terms, however, seem inappropriate, since the synthetic
part of the process is not known to be due to the action of light. In the
presence of chlorophyll light reduces the carbon dioxide, while the synthetic
part of the process may not be influenced by light. Since the process is
similar to that which chemists call conversion, and since the carbon is the
important food element derived from the air, for popular treatment the term
carbon conversion seems more appropriate.

148. Starch is formed only in the green parts of variegated
leaves. — If we test for starch in variegated leaves like the leaf of
a coleus plant, we shall have an interesting demonstration of the
fact that the green parts of plants only form starch. We may
take a leaf which is partly green and partly white, from a plant
which has been standing for some time in bright light. Fig. 51 is
from a photograph of such a leaf. We should first boil it in
alcohol to remove the green color. Now immerse it in the
potassium iodide of iodine solution for a short time. The parts
which were formerly green are now dark blue or nearly black,
showing the presence of starch in those portions of the leaf,
while the white part of the leaf is still uncolored. This is well
shown in fig. 52, which is from a photograph of another coleus
leaf treated with the iodine solution.

149. Translocation of starch. — It has been found that leaves of green
plants grown in the sunlight contain starch when examined after being in the
sunlight for several hours. But when the plants are left in the dark for a
day or two the leaves contain no starch, or a much smaller amount. This sug-
gests that starch after it has been formed may be transferred from the leaves,
or from those areas of the leaves where it has been formed.

62

PHYSIOLOGY.

150. To test this let us perform an experiment which is often made. We
tnay take a plant such as a garden tropaeolum or a clover plant, or other land

Leaf of coleus showing green and white
areas, before treatment with iodine.

Similar leaf treated with iodine, the starch re-
action only showing where the leaf was green.

plant in which it is easy to test for the presence of starch. Pin a piece of
circular cork, which is smaller than the area of the leaf, on either side of the

leaf, as in fig. 53. Place the
plant where it will be in the
sunlight. On the afternoon
of the following day, if the sun
has been shining, we may
remove the corks and test for
starch, using the entire leaf,
by Schimper's method. Or
the method described in 146

Fig" 53> c Fig" 54: . may be employed. The part

Leaf of tropaeolum Leaf of tropaeolum treated

with portion covered with iodine after removal of covered by the cork Will not
with corks to prevent cork, to show that starch is re- . , ,

theformation of starch, moved from the leaf during the give the reaction for starch,
(After Detmer.) night. as snOwn by the absence of the

bluish color, while the other parts of the leaf will show it. The starch
which was in that part of the leaf the day before was dissolved and removed

CARBON FOOD OF PLANTS. 63

during the night, and then during the following day, the parts being cov-
ered from the light, no starch was formed in them.

151. Starch in other parts of plants than the leaves. — We

may use the iodine test to search for starch in other parts of
plants than the leaves. If we cut a potato tuber, scrape some of
the cut surface into a pulp, and apply the iodine test, we obtain
a beautiful and distinct reaction showing the presence of starch.
Now we have learned that starch is only formed in the parts
containing chlorophyll. We have also learned that the starch
which has been formed in the leaves disappears from the leaf or
is transferred from the leaf. We judge therefore that the starch
which we have found in the tuber of the potato was formed first
in the green leaves of the plant, as a result of carbon assimila-
tion. From the leaves it is transferred in solution to the under-
ground stems, and stored in the tubers. The starch is stored
here by the plant to provide food for the growth of new plants
from the tubers, which are thus much more vigorous than the
plants would be if grown from the seed.

152. The potato is only one example of a great many cases where starch
is stored up as a reserve material by plants, but not always in the form of
tubers. In the sweet potato and some other plants it is stored in the roots,
certain ones of the roots becoming very much thickened; in the onion it is
stored in certain leaves which form the onion bulb.

153. Form of starch grains. — Where starch is stored as a reserve material
it occurs in grains which usually have certain characters peculiar to the
species of plant in which they are found. They vary in size in many
different plants, and to some extent in form also. If we scrape some of the
cut surface of the potato tuber into a pulp and mount a small quantity in
water, or make a thin section for microscopic examination, we will find
large starch grains of a beautiful structure. The grains are oval in
form and more or less irregular in outline. But the striking peculiarity is
the presence of what seem to be alternating dark and light lines in the starch
grain. We note that the lines form irregular rings, which are smaller
and smaller until we come to the small central spot termed the "hilum " of
the starch grain. It is supposed that these apparent lines in the starch
grain are caused by the starch substance being deposited in alternating dense
and dilute layers, the dilute layers containing more water than the dense
ones; others think that the successive layers from the hilum outward are

64 PHYSIO LOG Y.

regularly of diminishing density, and that this gives the appearance of alter-
nating lines. The starch formed by plants is one of the organic substances
which are manufactured by plants, and it is the basis for the formation of
other organic substances in the plant. Without carbon food green plants
cannot make any appreciable increase of plant substance, though a consider-
able increase in size of the plant may take place.

CHAPTER XL

CHLOROPHYLL AND THE FORMATION OF STARCH.

154. In our experiments thus far in treating of the absorption
of carbon dioxide and the evolution of oxygen, with the accom-
panying formation of starch, we have used green plants.

155. Fungi cannot form starch. — If we should extend our
experiments to the fungi, which lack the green color so charac-
teristic of the majority of plants, we should find that carbon con-
version does not take place even though the plants are exposed
to direct sunlight. These plants cannot then form starch, but
obtain carbohydrates for food from other sources.

156. Etiolated plants cannot convert carbon. — Moreover
carbon assimilation is usually confined to the green plants, and
if by any means one of the ordinary green plants loses its green
color carbon conversion cannot take place in that plant, even
when brought into the sunlight, until the green color has
appeared under the influence of light.

This may be very easily demonstrated by growing seedlings
of the bean, squash, corn, pea, etc. (pine seedlings are green even
when grown in the dark), in a dark room, or in a dark receiver
of some kind which will shut out the rays of light. The room
or receiver must be quite dark. As the seedlings are "coming
up," and as long as they remain in the dark chamber, they will
present some other color than green; usually they are somewhat
yellowed. Such plants are said to be etiolated. If they are
brought into the sunlight now for a few hours and then tested
for the presence of starch the result will be negative. But if the
plant is left in the light, in a few days the leaves begin to take

65

66

PHYS1OLOG Y.

on a green color, and then we find that carbon conversion
begins.

157. Chlorophyll and chloroplasts. — The green substance in
plants is then one of the important factors in this complicated
process of forming starch. This green substance is chlorophyll,
and it usually occurs in definite bodies, the chlorophyll bodies,
or chloroplasts.

The material for new growth of plants grown in the dark is derived from
the seed. Plants grown in the dark consist largely of water and protoplasm,
the walls being very thin.

158. Form of the chlorophyll bodies. — Chlorophyll bodies
vary in form in some different plants, especially in some of the
lower plants. This we have already seen in the case of
spirogyra, where the chlorophyll body is in the form of a very
irregular band, which courses around the inner side of the cell
wall in a spiral manner. In zygnema, which is related to
spirogyra, the chlorophyll bodies are star-shaped. In the
desmids the form varies greatly. In oedogonium, another of
the thread-like algae, illustrated in fig. 95, the chlorophyll bodies

Fig- 55-

Section of ivy leaf, palisade cells above, loose parenchyma, with large intercellular spaces
in center. Epidermal cells on either edge, with no chlorophyll bodies.

are more or less flattened oval disks. In vaucheria, too, a
branched thread-like alga shown in fig. 106, the chlorophyll
bodies are oval in outline. These two plants, oedogonium and

CHLOROPHYLL; STARCH. 67

vaucheria, should be examined here if possible, in order to be-
come familiar with their form, since they will be studied later
under morphology (see chapters on oedogonium and vaucheria,
for the occurrence and form of these plants). The form of the
chlorophyll body found in cedogonium and vaucheria is that
which is common to many of the green algae, and also occurs in
the mosses, liverworts, ferns, and the higher plants. It is a
more or less rounded, oval, flattened disk.

159. Chlorophyll is a pigment which resides in the chloroplast. — That
the chlorophyll is a coloring substance which resides in the chloroplastid,
and does not form the body itself, can be demonstrated by dissolving out the
chlorophyll when the framework of the chloroplastid is apparent. The
green parts of plants which have been placed for some time in alcohol lose
their green color. The alcohol at the same time becomes tinged with green.
In sectioning such plant tissue we find that the chlorophyll bodies, -or chloro-
plastids as they are more properly called, are still intact, though the green
color is absent. From this we know that chlorophyll is a substance distinct
from that of the chloroplastid.

160. Chlorophyll absorbs energy from sunlight for carbon conversion.-— It
has been found by analysis with the spectrum that chlorophyll absorbs cer-
tain of the rays of the sunlight. The energy which is thus obtained from
the sun, called kinetic energy, is supposed to act on the molecules of CO2 and
H2O, separating them into other molecules of C, H, and O, and that after a
series of complicated chemical changes starch is formed by the union of mole-
cules of carbon, oxygen, and hydrogen, the hydrogen and some of the oxygen
at least coming from the water in the cells of the plant. In this process of
the reduction of the CO8 and the formation of starch there is a surplus of
oxygen, which accounts for the giving off of oxygen during the process.

161. Rays of light concerned in carbon conversion. — If a solution of
chlorophyll be made, and light be passed through it, and this light be
examined with the spectrum, there appear what are called absorption bands.
These are dark bands which lie across certain portions of the spectrum.
These bands lie in the red, orange, yellow, green, blue, and violet, but the
bands are stronger in the red, which shows that chlorophyll absorbs more of
the red rays of light than of the other rays. These are the rays of low
refrangibility. The kinetic energy derived by the absorption of these rays
of light is transferred into potential energy. That is, the molecule of CO3 is
broken up, and then by a different combination of certain elements starch is
formed.*

* In the formation of starch during carbon conversion the separated mole-
cules from the carbon dioxide and water unite in such a way that carbon,

68 PHYSIOLOGY.

162. Starch grains formed in the chloroplasts. — During carbon conver-
sion the starch formed is deposited generally in small grains within the green
chloroplast in the leaf. We can see this easily by examining the leaves of
some moss like funaria which has been in the light, or in the chloroplasts
of the prothallia of ferns, etc. Starch grains may also be formed in the
chloroplasts from starch which was formed in some other part of the plant,
but which has passed in solution. Thus the functions of the chloroplast are
twofold, that of the conversion of carbon and the formation of starch grains.

163- In the translocation of starch when it becomes stored up in various
parts of the plant, it passes from the state of solution into starch grains in
connection with plastids similar to the chloroplasts, but which are not green.
The green ones are sometimes called chromoplasts, while the colorless ones
are termed leucoplasts.

164. Carbon conversion in other than green plants. — While organic com-
pounds are usually only formed by green plants, there are some exceptions.
Apparent exceptions are found in the blue-green algae like oscillatoria,
nostoc, or in the brown and red sea weeds like fucus, rhabdonia, etc. These
plants, however, possess chlorophyll, but it is disguised by another pigment or
color. There are plants, however, which do not have chlorophyll and yet
form organic substance with evolution of oxygen in the presence of light, as
for example a purple bacterium, in which the purple coloring substance
absorbs light, though the rays absorbed most energetically are not the red.

165. Influence of light on the movement of chlorophyll bodies. — In fern
prothallia. — If we place fern prothallia in weak light for a few hours, and
then examine them under the microscope, we find that the most of the chloro-
phyll bodies in the cells are arranged along the inner surface of the
horizontal wall. If now the same prothallia are placed in a brightly lighted
place for a short time most of the chlorophyll bodies move so that they are
arranged along the surfaces of the perpendicular walls, and instead of having
the flattened surfaces exposed to the light as in the former case, the edges
of the chlorophyll bodies are now turned toward the light. (See figs.
56, 57.) The same phenomenon has been observed in many plants. Light
then has an influence on chlorophyll bodies, to some extent determining their
position. In weak light they are arranged so that the flattened surfaces are
exposed to the incidence of the rays of light, so that the chlorophyll will
absorb as great an amount as possible of kinetic energy; but intense light is

hydrogen, and oxygen are united into a molecule of starch. This result is
usually represented by the following equation: CO2 -f- H2O = CH2O -f O2.
Then by polymerization 6(CH2O) = C6Hi2O6 = grape sugar. Then
C6H12Ofl — H2O = C6H10O6 = starch. It is believed, however, that the
process is much more complicated than this, and that several different com-
pounds are formed before starch finally appears.

CHLOROPHYLL; STARCH. 69

stronger than necessary, and the chlorophyll bodies move so that their edges
are exposed to the incidence of the rays. This movement of the chlorophyll
bodies is different from that which takes place in some water plants like

Fig. 56. Fig. 57.

Ceil exposed to weak diffused light show- Same cell exposed to strong light, showing

ing chlorophyll bodies along the horizontal chlorophyll bodies have moved to perpen-
walls. dicular walls.

Figs. 56, 57. — Cell of prothallium of fern.

elodea. The chlorophyll bodies in elodea are free in the protoplasm. The
protoplasm in the cells of elodea streams around the inside of the cell wall
much as it does in nitella and the chlorophyll bodies are carried along in the
currents, while in nitella they are stationary.

CHAPTER XII.

NUTRITION AND MEMBERS OF THE PLANT BODY.

166. In connection with the study of the means for obtaining nutriment
from the soil or water by the green plants it will be found convenient to
observe carefully the various forms of the plant. Without going into detail
here the suggestion is made that simple thread forms like spirogyra, cedogo-
nium, and vaucheria; expanded masses of cells as are found in the thalloid
liverworts, the duckweed, etc. , be compared with those liverworts, and with the
mosses, where leaf-like expansions of a central axis have been differentiated,
and how this differentiation, from the physiological standpoint, has been
carried farther in the higher land plants.

167. Nutrition of liverworts. — In many of the plants termed liverworts
the vegetative part of the plant is a thin, flattened, more or less elongated
green body known as a thallus.

Ricda. — One of these, belonging to the genus riccia, is shown in fig.
58. Its shape is somewhat like that of a minute ribbon which is forked at

intervals in a dichotomous man-
ner, the characteristic kind of
branching found in these thalloid
liverworts. This riccia (known
as R. lutescens) occurs on damp
soil; long, slender, hair-like
processes grow out from the
under surface of the thallus,
which resemble root hairs and
serve the same purpose in the
processes of nutrition. Another
species of riccia (R. crystallina)
is shown in fig. 171. This plant
is quite circular in outline and
occurs on muddy flats. Some
species float on the water.

168. Marchantia. — One of the larger and coarser liverworts
is figured at 59. This is a very common liverwort, growing in

70

Fig. 58.
Thallus of riccia lutescens.

NUTRU^ION; MEMBERS PLANT BODY. /I

very damp and muddy places and also along the margins of
streams, on the mud or upon the surfaces of rocks which are
bathed with the water. This is known as Marchantia polymorpha.
If we examine the under surface of the marchantia we see
numerous hair-like processes which attach the plant to the soil.
Under the microscope we see that some of these are exactly like
the root hairs of the seedlings which we have been studying,
and they here serve the same purpose. Since, however, there are
no roots on the marchantia plant, these hair-like outgrowths are

Fig. 59-
Marchantia plant with cupules and gemmae ; rhizoids below.

usually termed here rhizoids. In marchantia they are of two
kinds, one kind the simple ones with smooth walls, and the
other kind in which the inner surfaces of the walls are roughened
by processes which extend inward in the form of irregular tooth-
like points. Besides the hairs on the under side of the thallus
we note especially near the growing end that there are two rows
of leaf-like scales, those at the end of the thallus curving up
over the growing end, and thus serve to protect the delicate
tissues at the growing point.

PHYSIOLOGY.

169. Frullania. — In fig. 60 is shown another liverwort,
which differs greatly in form from the ones we have just been
studying in that there is a well-defined axis with
lateral leaf- like outgrowths. Such liverworts
are called foliose liverworts. Besides these two
quite prominent rows of leaves there is a third
row of poorly developed leaves on the under
surface. Also from the under surface of the axis

we see here
and there
slender out-
growths, the
r h izo i d s,
through
which much
of the liquid

Fig. 62.

Fig. 60.
Portion of plant of
Frullania, a foliose
liverwort.

Fig. 61.
Portion of same
more highly magni-
fied, showing over-
lapping leaves.

Under side

showing forked nutriment is

under row of

leaves and lobes absorbed.

of lateral leaves.

170. Nutrition of the mosses. — Among the mosses which
are usually common in moist and shaded situations, examples
are abundant which are suitable for the study of the organs of
absorption. If we take for example a plant of Mnium (M. affine)
which is illustrated in fig. 64, we note that it consists of a slender
axis with thin flat, green, leaf-like expansions. Examin-
ing with the microscope the lower end of the axis, which is
attached to the substratum, there are seen numerous brown
colored threads more or less branched. (For nutrition of
moulds, mushrooms, parasitic fungi, dodder, carnivorous plants,
lichens, aquatic plants, etc., see Part III. Ecology.)

171. The plant body. — In the simpler forms of plant life, as in spirogyra
and many of the algae and fungi, the plant body is not differentiated into
parts. In many other cases the only differentiation is between the growing
part and the fruiting part. In the algae and fungi there is no differentiation
into stem and leaf, though there is an approach to it in some of the higher
forms. Where this simple plant body is flattened, as in the sea-wrack, or
ulva, it is a frond. The Latin word for frond is thallus, and this name is

NUTRITION; MEMBERS PLANT BODY. 73

applied to the plant body of all the lower plants, the algae and fungi. The
algae and fungi together are sometimes called the thallophytes, or thallus

plants. The word thallus is also sometimes
applied to the flattened body of the liver-
worts. In the foliose liverworts and mosses
there is an axis with leaf-like expansions.
These are believed by some to represent
true stems and leaves, by others to represent
a flattened thallus in which the margins are
deeply and regularly divided, or in which
the expansion has only taken place at regular
intervals.

Fig. 63.
Foliose liverwort vBazzania) showing dichotomous branching and overlapping leaves.

172. Members of the plant body. — In the higher plants there is usually
great differentiation of the plant body, though in many forms, as in the duck-
weeds, it is a frond. While there is great variation in the form and func-
tion of the members of the plant body, they are reducible to a few fundamental
members. Some reduce these forms to three, the root, stem, and leaf, while
others to two, the root and shoot, which is perhaps the better arrangement.
Here the shoot is farther divided into stem and leaf, the leaf being a lateral
outgrowth of the stem. The different forms of the members are usually des-
ignated by special names, but it is convenient to group them in the single
series. Examples are as follows:

173. Stem series.

Tubers, underground thickened stems, bearing buds and scale leaves; ex.,
Irish potato.

Root-stocks, underground, usually elongated, bearing scales or bracts, and
a leafy shoot; ex., trillium, mandrake, etc. Root-stocks of the ferns bear
expanded, green leaves.

Runners, slender, trailing, bearing bracts, and leafy stems as branches;
ex., strawberry vines.

Conns, underground, short, thick, leaf bearing and scale bearing; ex., In-
dian turnip.

PHYSIOLOGY.

Bulbs, usually underground, short, conic, leaf and scale bearing; ex.,
lily.

Thorns, stout, thick, poorly developed bran-
ches with rudiments of leaves (scales); ex.,
hawthorn.

Tendrils, slender reduced stems.

Flower axes (see morphology of the angio-
sperms).

174. Leaf series. — Besides the foliage leaves,
the following are some of their modifications:

Flower parts (see morphology of the angio-
sperms).

tracts and scales, small, the former usually
green (flower bracts), the latter usually chloro-
phylless. Bud scales are sometimes green.

Tendrils, modifications of the entire leaf
(tendrils of the squash where the branched
tendril shows the principal veins of the leaf),
modification of the terminal pinnae of the leaf
(vetch), etc.

Spines (examples are found in the cacti,
where the stem is enlarged and green, function-
ing as a leaf).

Other modifications occur as in the pitcher
plant, insectivorous plants, etc.

175. The root shows less modification. Be-
sides normal roots, which are fibrous in most
small plants and stout in the larger ones, some
of the modifications are found in fleshy roots,
where nourishment is stored (ex., dahlia,

Fig. 64. sweet potato, etc.), aerial roots (ex., poison

Female plant (gametophyte) of ivy the twining form), aerial orchids, etc. For
a moss (mmum), showing rhizoids "'
below, and the tuft of leaves above, modifications of roots due to symbiotic fungi,

see chapter on Nutrition in Part III.

which protect the archegonia.

CHAPTER XIII.

GROWTH. .

176. By growth is usually meant an increase in the bulk of
the plant accompanied generally by an increase in plant sub-
stance. Among the lower plants growth is easily studied in
some of the fungi.

177. Growth in mucor. — Some of the gonidia (often called
spores) may be sown in nutrient gelatine or agar, or even in
prune juice. If the culture has been placed in a warm room, in
the course of 24 hours, or even less, the preparation will be ready
for study.

178. Form of the gonidia. — It will be instructive if we first
examine some of the gonidia which have not been sown in the cul-
ture medium. We should note their rounded or globose form, as
well as their markings if they belong to one of the species with
spiny walls. Particularly should we note the size, and if possible
measure them with the micrometer, though this would not be
absolutely necessary for a comparison, if the comparison can be
made immediately. Now examine some of the gonidia which
were sown in the nutrient medium. If they have not already
germinated we will note at once that they are much larger than
those which have not been immersed in a moist medium.

179. The gonidia absorb water and increase in size before
germinating. — From our study of the absorption of water or
watery solutions of nutriment by living cells, we will easily un-
derstand the cause of this enlargement of the gonidium of the
mucor when surrounded by the moist nutrient medium. The
cell-sap in the spore takes up more water than it loses by diffu-

75

76

PHYSIOLOGY.

sion, thus drawing water forcibly through the protoplasmic mem-
brane. Since it does not filter out readily, the increase in

Fig. 65.
Spores of mucor, and different stages of germination.

quantity of the water in the cell produces a pressure from within
which stretches the membrane, and the elastic cell wall yields.
Thus the gonidium becomes larger.

180. How the gonidia germinate. — We should find at this
time many of the gonidia extended on one side into a tube-like
process the length of which varies according to time and tempera-
ture. The short process thus begun continues to elongate. This
elongation of the plant is growth, or, more properly speaking, one
of the phenomena of growth.

181. The germ tube branches and forms the mycelium. —
In the course of a day or so branches from the tube will appear.
This branched form of the threads of the fungus is, as we will
remember, the mycelium. We can still see the point where
growth started from the gonidium. Perhaps by this time several
tubes have grown from a single one. The threads of the myce-
lium near the gonidium, that is, the older portions of them, have
increased in diameter as they have elongated, though this increase
in diameter is by no means so great as the increase in length.
After increasing to a certain extent in diameter, growth in this
direction ceases, while apical growth is practically unlimited,
being limited only by the supply of nutriment.

182 Growth in length takes place only at the end of the
thread. — If there were any branches on the mycelium when the

GROWTH. 77

culture was first examined, we can now see that they remain
practically the same distance from the gonidium as when they
were first formed. That is, the older portions of the mycelium
do not elongate. Growth in length of the mycelium is confined
to the ends of the threads.

183. Protoplasm increases by assimilation of nutrient
substances. — As the plant increases in bulk we note that there
is an increase in the protoplasm, for the protoplasm is very
easily detected in these cultures of mucor. This increase in the
quantity of the protoplasm has come about by the assimilation
of the nutrient substance, which the plant has absorbed. The
increase in the protoplasm, or the formation of additional plant
substance, is another phenomenon of growth quite different from
that of elongation, or increase in bulk.

184. Growth of roots. — For the study of the growth of roots
we may take any one of many different plants. The seedlings of
such plants as peas, beans, corn, squash, pumpkin, etc., serve
excellently for this purpose.

185. Roots of the pumpkin. — The seeds, a handful or so, are
soaked in water for about 12 hours, and then placed between
layers of paper or between the folds of cloth, which must be kept
quite moist but not very wet, and should be kept in a warm place.
A shallow crockery plate, with the seeds lying on wet filter paper,
and covered with additional filter paper, or with a bell jar, an-
swers the purpose well. .

The primary or first root (radicle) of the embryo pushes its way
out between the seed coats at the small end. When. the seeds are
well germinated, select several which have the root ^-$cm long.
With a crow-quill pen we may now mark the terminal portion of •
the root off into very short sections as in fig. 66. The first mark
should be not more than imm from the tip, and the others not
more than imm apart. Now place the seedlings down on damp
filter paper, and cover with a bell jar so that they will re-
main moist, and if the season is cold place them in a warm room.
At intervals of 8 or 10 hours, if convenient, observe them and
note the farther growth of the root.

78 PHYSIO LOG Y.

186. The region of elongation. — While the root has elon-
gated, the region of elongation is not at the tip of the root. It lies
a little distance back from the tip, beginning at
about 2mm from the tip and extending over
an area represented by from 4-5 of the milli-
meter marks. The
root shown in fig. 66
was marked at IOA.M.
on July 5. At 6 P.M.
of the same day, 8

Fig. 66.

Root of germinating pumpkin, showing region of
elongation just back of the tip.

hours later, growth had taken place as shown in the middle
figure. At 9 A.M. on the following day, 15 hours later, the
growth is represented in the lower one. Similar experiments
upon a number of seedlings gives the same result : the region of
elongation in the growth of the root is situated a little distance
back from the tip. Farther back very little or no elongation
takes place, but growth in diameter continues for some time, as
we should discover if we examined the roots of growing pump-
kins, or other plants,- at different periods.

187. Movement of region of greatest elongation. — In the
region of elongation the areas marked off do not all elongate
equally at the same time. The middle spaces elongate most
rapidly and the spaces marked off by the 6, 7, and 8 mm marks
elongate slowly, those farthest from the tip more slowly than the
others, since elongation has nearly ceased here. The spaces.
marked off between the z-^mm marks also elongate slowly, but
soon begin to elongate more rapidly, since that region is becom-
ing the region of greatest elongation. Thus the region of greatest
elongation moves forward as the root grows, and remains ap-
proximately at the same distance behind the tip.

188. Formative region. — If we make a longitudinal section of the tip of a
growing root of the pumpkin or other seedling, and examine it with the mi-

GROWTH. 79

Croscope, we will see that there is a great difference in the character of the
cells of the tip and those in the region of elongation of the root. First there
is in the section a V-shaped cap of loose cells which are constantly being
sloughed off. Just back of this tip the cells are quite regularly isodiametric,
that is, of equal diameter in all directions. They are also very rich in pro-
toplasm, and have thin walls. This is the region of the root where new cells
are formed by division. It is Reformative region. The cells on the outside
of this area are the older, and pass over into the older parts of the root and root
cap. If we examine successively the cells back from this formative region
we find that they become more and more elongated in the direction of the
axis of the root. The elongation of the cells in this older portion of the root
explains then why it is that this region of the root elongates more rapidly
than the tip.

189. Growth of he stem. — We may use a bean seedling
growing in the soil. At the junction of the leaves with the stem
there are enlargements. These are the nodes, and the spaces on
the stem between successive nodes are the internodes. We should
mark off several of these internodes, especially the younger ones,
into sections about $mm long. Now observe these at several
times for two or three days, or more. The region of elongation
is greater than in the case of the roots, and extends back farther
from the end of the stem. In some young garden bean plants
the region of elongation extended over an area of ^omm in one
internode.

190. Force exerted by growth. — One of the marvelous things connected
with the growth of plants is the force which is exerted by various members of
the plant under certain conditions. Observations on seedlings as they are
pushing their way through the soil to the air often show us that considerable
force is required to lift the hard soil and turn it to one side. A very striking
illustration may be had in the case of mushrooms which sometimes make
their way through the hard and packed soil of walks or roads. That succu-
lent and tender plants should be capable of lifting such comparatively heavy
weights seems incredible until we have witnessed it. Very striking illustra-
tions of the force of roots are seen in the case of trees which grow in rocky
situations, where rocks of considerable weight are lifted, or small rifts in
large rocks are widened by the lateral pressure exerted by the growth of a
root, which entered when it was small and wedged its way in.

191. Grand period of growth. — Great variation exists in the rapidity of
growth even when not influenced by outside conditions. In our study of the
elongation of the root we found that the cells just back of the formative region

8o

PHYSIOLOGY.

elongated slowly at first. The rapidity of the elongation of these cells in-
creases until it reaches the maximum. Then the rapidity of elongation les-
sens as the cells come to lie farther from the tip. The period of maximum
elongation here is the grand period of growth of these cells.

192. Just as the cells exhibit a grand period of growth, so the members of
the plant exhibit a similar grand period of growth. In the case of leaves,
when they are young the rapidity of growth is comparatively slow, then it
increases, and finally diminishes in rapidity again. So it is with the stem.
When the plant is young the growth is not so rapid; as it approaches middle
age the rapidity of growth increases; then it declines in rapidity at the close
of the season.

193. Energy of growth. — Closely related to the grand period of growth is
what is termed the energy of growth. This is manifested in the compara-
tive size of the members of a given plant.
To take the sunflower for example, the
lower and first leaves are comparatively
small. As the plant grows larger the
leaves are larger, and this increase in
size of the leaves increases up to a maxi-
mum period, when the size decreases
until we reach the small leaves at the top
of the stem. The grand period of growth
of the leaves corresponds with the maxi-
mum size of the leaves on the stem.
The rapidity and energy of growth of the
stem is also correlated with that of the

leaves, and the grand period
of growth is coincident with
that of the leaves. It would
be instructive to note it
in the case of other plants
and also in the case of
fruits.

194. Nutation. — During the growth of the stem all of the cells of a given
section of the stem do not elongate simultaneously. For example the cells
at a given moment on the south side are elongating more rapidly than the
cells on the other side. This will cause the stem to bend slightly to the
north. In a few moments later the cells on the west side are elongating more
rapidly, and the stem is turned to the east; and so on, groups of cells in suc-
cession around the stem elongate more rapidly than the others. This causes
the stem to describe a circle or ellipse about a central point. Since the re-
gion of greatest elongation of the cells of the stem is gradually moving toward
the apex of the growing stem, this line of elongation of the cells which is

Fig. 67.

Lever auxanometer (Oels) for measuring elongation of
the stem during growth.

GROWTH. 8 1

traveling around the stem does so in a spiral manner. In the same way,
while the end of the stem is moving upward by the elongation of the cells,
and at the same time is slowly moved around, the line which the end of the
stem describes must be a spiral one. This movement of the stem, which is
common to all stems, leaves, and roots, is nutation,

195. The importance oi nutation to twining stems in their search for a
place of support, as well as for the tendrils on leaves or stems, will be seen.
In the case of the root it is of the utmost importance, as the root makes its
way through the soil, since the particles of soil are more easily thrust aside.
The same is also true in the case of many stems before they emerge from the
soil.

CHAPTER XIV.

IRRITABILITY.

196. We should now examine more carefully certain move-
ments which the members of the plants exhibit. By this
time we have probably observed that the direction which the
root and stem take upon germination of the seed is not due to
the position in which the seed happens to lie. Under normal
conditions we have seen that the root grows downward and the
stem upward.

197. Influence of the earth on the direction of growth. —
When the stem and root have been growing in these directions
for a short time let us place the seedling in a horizontal position,
so that the end of the root extends over an object of support in
such a way that it will be free to go in any direction. It should
be placed under a bell jar so as to prevent drying, or a germi-
nated pea may be pinned to the lower side of a cork, which is
then placed in the mouth of a bottle containing a little water.
In the course of twelve to twenty- four hours the root which was
formerly horizontal has turned the tip downward again. If we
should mark off millimeter spaces beginning at the tip of the
root, we should find that the motor zone, or region of curvature,
lies in the same region as that of the elongation of the root.

It was found by Knight, as a result of experiments, that the
force which causes the roots to take the downward direction is
gravity. This force is geotropism, which means a turning in-
fluenced by the earth, and is applied to the growth movements
of plants influenced by the earth, with regard to the direction
of growth. Growth toward the earth is also termed progeotro •

82

IRRITABILITY.

pism. So the lateral growth of the secondary roots is termed
diageotropism.

The stem, on the other hand, which was placed in a horizontal
position has become again erect. This turning of the stem in

Fig. 68. Fig. 69.

Germinating pea placed in a hori-
zontal position.

Figs. 68, 69. — Progeotropism of the pea root.

In 24 hours gravity has caused the root to
turn downward.

the upward direction takes place in the dark as well as in the
light, as we can see if we start the experiment at nightfall, or
place the plant in the dark. This up-
ward growth of the stem is also influ-
enced by the earth, and therefore is a
case of geotropism. The special desig-
nation in the case of upright stems is
negative geotropism, or apogeotropism, or
the stems are said
to be apogeotropic.

Fig. 70.

Pumpkin seedling showing apogeotropism. Seedling at the left placed hori-
zontally, in 24 hours the stem has become erect. „

If we place a rapidly growing potted plant in a horizontal

position by laying the pot on its side, the ends of the shoots

will soon turn upward again when placed in a horizontal

position. Young bean plants growing in a pot began within
two hours to turn the ends of the shoots upward.

PHYSIOLOGY.

Horizontal leaves and shoots can be shown to be subject to
the same influence, and are therefore diageotropic.

198. Influence of light. — Not only is light a very important
factor for plants during carbon conversion, it exerts great influ-
ence on plant growth and movement.

199. Retarding influence of light on growth. — We have
only to return to the experiments performed in growing plants in
the dark to see

one of the influ-
ences which light
exerts on plants.
The plants grown
in the dark were
longer and more
slender than those
grown in the light.
Light then has a
retarding influ-
ence on the elong-
ation of the stem.

200. Influence

Fig. 7

f -i - -U j. j • Radish seedlings grown in the

01 llgnt On QireC- dark, long, slender, not green.

tion of growth. — While we are growing

seedlings, the pots or boxes of some of them

should be 'placed so that the plants will Fi

have a one-sided illumination. This can Radish seedlings grown in

the light, shorter, stouter, and

be done by placing them near an open green in color. Growth re-

. , . b . , . , , .„ tarded by light.

window, in a room with a one-sided illu-
mination, or they may be placed in a box closed on all sides
but one which is facing the window or light. In 12-24 hours,
or even in a much shorter time in some cases, the stems of the
seedlings will be directed toward the source of light. This
influence exerted by the rays of light is heliotropism, a turning
influenced by the sun or sunlight.

201. Diaheliotropism. — Horizontal leaves and shoots are
diaheliotropic as well as diageotropic. The general direction

IRRITABILITY.

which leaves assume under this influence is that of placing them
with the upper surface perpendicular to the rays of light which
fall upon them. Leaves, then, exposed to
the brightly lighted sky are, in general,
horizontal. This position is taken in direct
response to the
stimulus of light.
The leaves of plants
with a one-sided illu-
mination,
as can be
seen by
trial, are
turned with

Seedling of castor-oil bean, before and after

a one-sided illumination. SUrfaCCS tO-

ward the

source of light, or perpendicular to the in-
cidence of the light rays. In this way
light overcomes for the time being the
direction which growth gives to the leaves.
The so-called "sleep" of plants is of
course not sleep, though the leaves " nod,"
or hang downward, in many cases. There
are many plants in which we can note
this drooping of the leaves at nightfall, and in order to prove
that it is not determined by the time of day we can resort to
a well-known ex-
periment to induce
this condition dur-
ing the day. The
plant which has
been used to illus-
trate this is the sun-
flower. Some of

these plants, which

Fig. 74-

Dark chamber with opening at one side to show heliotropism.
(After Schleichert.)

86

PHYSIOLOGY.

were grown in a box, when they were about 3$cm high were
covered for nearly two days, so that the light was excluded.
At midday on the second day the box was removed, and the
leaves on the covered plants are well represented by fig. 75, which
was made from one of them. The leaves of the other plants
in the box which were not covered were horizontal, as shown
by fig. 76. Now on leaving these plants, which. had exhibited

Fig. 76.

Sunflower plant removed from
darkness, leaves extending under
influence of light (diahejiotro-
pism.)

induced ' ' sleep ' ' move-
ments, exposed to the light
they gradually assumed
the horizontal position again.

202. Epinasty and hyponasty. — During
the early stages of growth of many leaves,
as in the sunflower plant, the direction of
growth is different from what it is at a later
period. The under surface of the young
leaves grows more rapidly in a longitudinal
direction than the upper side, so that the
leaves are held upward close against the
bud at the end of the stem. This is termed
hyponasty, or the leaves are said to be
hyponaslic. Later the growth is more rapid
on the upper side and the leaves turn downward or away from the bud.
This is termed epinasty, or the leaves are said to be epinastic. This is shown
by the night position of the leaves, or in the induced "sleep "of the sun-

Fig- 75-

Sunflower plant. Epinastic con-
dition of leaves induced during the
day in darkness.

IRRITABILITY. 87

flower plant in the experiment detailed above. The day position of the
leaves on the other hand, which is more or less horizontal, is induced because
of their irritability under the influence of light, the inherent downward or
epinastic growth is overcome for the time. Then at nightfall or in darkness,
the stimulus of light being removed, the leaves assume the position induced
by the direction of growth.

In the case of the cotyledons of some plants it would seem that the growth
was hyponastic even after they have opened. The day position of the coty-

Fig. 77. Fig. 78.

Squash seedling. Position of cotyledons in Squash seedling. Position of cotyledons in
light. the dark.

ledons of the pumpkin is more or less horizontal, as shown in fig. 77. At
night, or if we darken the plant by covering with a tight box, the leaves
assume the position shown in fig. 78.

While the horizontal position is the general one which is assumed by
plants under the influence of light, their position is dependent to a certain
extent on the intensity of the light as well as on the incidence of the light
rays. Some plants are so strongly heliotr%>pic that they change their posi-
tions all during the day.

203. Leaves with a fixed diurnal position. — Leaves of some plants when
they are developed have a fixed diurnal position and are not subject to

88

PHYSIOLOGY.

variation. Such leaves tend to arrange themselves in a vertical or para-
heliotropic position, in which the surfaces are not exposed to the incidence
of light of the greatest intensity, but to the incidence of the rays of diffused
light. Interesting cases of the fixed position of leaves are found in the so-
called compass plants (like Silphium laciniatum, Lactuca scariola, etc.). In
these the horizontal leaves arrange themselves with the surfaces vertical, and
also pointing north and south, so that the surfaces face east and west.

204. Importance of these movements. — Not only are the leaves placed in
a position favorable for the absorption of the rays of light which are con-
cerned in making carbon available for food, but they derive other forms of
energy from the light, as heat, which is absorbed during the day. Then
with the nocturnal position, the leaves being drooped down toward the stem,
or with the margin toward the sky, or with the cotyledons as in the pump-
kin, castor -oil bean, etc., clasped upward together, the loss of heat by
radiation is less than it would be if the upper surfaces of the leaves were
exposed to the sky.

205. Influence of light on the structure of the leaf. — In our study of the
structure of a leaf we found that in the ivy leaf the palisade cells were on

the upper surface. This is the case with a
great many leaves, and is the normal arrange-
ment of " dorsi ventral " leaves which are dia-
heliotropic. Leaves which are paraheliotropic
tend to have palisade cells on both surfaces.
The palisade layer of cells as we have seen is
made up of cells lying very close together, and
they thus prevent rapid evaporation. They
also check to some extent the entrance of the
rays of light, at least more so than the loose
spongy parenchyma cells do. Leaves developed
in the shade have looser palisade and paren-
chyma cells. In the case of some plants, if
we turn over a very young leaf, so that the
under side will be uppermost, this side will
develop the palisade layer. This shows that
light has a great influence on the structure of
the leaf.

206. Movement influenced by contact. — In
the case of tendrils, twining leaves, or stems,
the irritability to contact is shown in a move-
Fig. 79. ment of the tendril, etc., toward the object in
Coiling tendril of bryony. touch. This causes the tendril or stem to coil
around the object for suppc.rt. The stimulus is also extended down the part
of the tendril below the point of contact (see fig. 79), and that part coils.

B

IRRI TABILITY.

89

up like a wire coil spring, thus drawing the leaf or branch from which the
tendril grows closer to the object of support. This coil between the object
of support and the plant is also very important in easing up the plant when
subject to violent gusts of wind which might tear the plant from its support
were it not for the yielding and springing motion of this coil.

-These plants are remarkable for the
Mimosa pudica is an excellent plant

207. Sensitive plants,
rapid response to stimuli.
to study for this purpose.

208. Movement in response to stimuli. — If we pinch with
the forceps one of the terminal leaflets, or tap it with a pencil,
the two end leaflets fold above the " vein" of the pinna. This

is immediately followed
by the movement of the
next pair, and so on as
shown in fig. 81, until all
the leaflets on this pinna
are closed, then the stimu-
lus travels down the
other pinnae in a simi-
lar manner, and

Fig. So.

Sensitive-plant leaf
in normal position.

Fig.Si.
Pinnae fold-
ing up after
stimulus.

soon the pinnae approximate each other and
the leaf then drops downward as shown in

Later aJl the pinnae

fig. 82. The normal position of the leaf is folded and leaf drooped,
shown in fig. 80. If we jar the plant by striking it or by jarring
the pot in which it is grown all the leaves quickly collapse into
the position shown in fig. 82. If we examine the leaf now we
will see minute cushions at the base of each leaflet, at the
junction of the pinnae with the petiole, and a larger one at the
junction of the petiole with the stem. We will also note that
the movement resides in these cushions.

9O PH YSIOLOG Y.

209. Transmission of the stimulus. — The transmission of
the stimulus in this mimosa from one part of the plant has been
found to be along the cells of the bast.

210. Cause of the movement. — The movement is caused by
a sudden loss of turgidity on the part of the cells in one portion
of the pulvinus, as the cushion is called. In the case of the
large pulvinus at the base of the petiole this loss of turgidity is
in the cells of the lower surface. There is a sudden change in
the condition of the protoplasm of the cells here so that they
lose a large part of their water. This can be seen if with a sharp
knife we cut off the petiole just above the pulvinus before move-
ment takes place. A drop of liquid exudes from the cells of the
lower side.

211. Paraheliotropism of the leaves of the sensitive plant. — If the mimosa
plant is placed in very intense light the leaflets will turn their edges toward
the incidence of the rays of light. This is also true of other plants in
intense light, and \sparaheliotropism. Transpiration is thus lessened, and
chlorophyll is protected from too intense light.

We thus see that variations in the intensity of light have an important
influence in modifying movements. Variations in temperature also exert

a considerable influence, rapid
elevation of temperature causing
certain flowers to open, and
falling temperature causing
them to close.

212. Sensitiveness of insec-
tivorous plants. — The Venus
fly-trap (Dionsea muscipula)and
the sundew (drosera) are in-
teresting examples of sensitive
plants, since the leaves close in
response to the stimulus from
insects.

Fig. 83.
Leaf of Venus

fly

trap (Dionaea musci-
pula). showing win

petiole
lobes

and toot!

Fig. 84.
Leaf of Drosera ro-
tundifolia, some of the
glandular hairs folding
inward as a result of a
stimulus.

213. Hydrotropism. —

Roots are sensitive to mois-
ture. They will turn toward moisture. This is of the greatest
importance for the well-being of the plant, since the roots will seek
those placcb in the soil where suitable moisture is present. On

IRRITA BILIT Y. 9 1

the other hand, if the soil is too wet there is a tendency for the
roots to grow away from the soil which is saturated with water.
In such cases roots are often seen growing upon the surface of
the soil so that they may obtain oxygen, which is important for
the root in the processes of absorption and growth. Plants then
may be injured by an excess of water as well as by a lack of
water in the soil.

214. Temperature. — In the experiments which have thus far been carried
on it will probably l;ave been noted that the temperature has much to do
with the length of time taken for seeds to germinate. It also influences the
rate of growth. The effect of different temperatures on the germination of
seed can be very well noted by attempting to germinate some in rooms at
various temperatures. It will be found, other conditions being equal, that
in a moderately warm room, or even in one quite warm, 25-30 degrees cen-
tigrade, germination and growth goes on more rapidly than in a cool room,
and here more rapidly than in one which is decidedly cold. In the case of
most plants in temperate climates, growth may go on at a temperature but
little above freezing, but few will thrive at this temperature.

215. If we place dry peas or beans in a temperature of about 70° C. for 15
minutes they will not be killed, but if they have been thoroughly soaked in
water and then placed at this temperature they will be killed, or even at a
somewhat lower temperature. The same seeds in the dry condition will
withstand a temperature of IO° C. below, but if they are first soaked in water
this low temperature will kill them.

216. In order to see the effect of freezing we may thoroughly freeze a sec-
tion of a beet root, and after thawing it out place it in water. The water is
colored by the cell-sap which escapes from the cells, just as we have seen it
does as a result of a high temperature, while a section of an unfrozen beet
placed in water will not color it if it was previously washed.

If the slice of the beet is placed at about 60° C. in a shallow glass vessel,
and covered, ice will be formed over the surface. If we examine it with the
microscope ice crystals will be seen formed on the outside, and these will
not be colored. The water for the formation of the crystals came from the
cell-sap, but the concentrated solutions in the sap were not withdrawn by
the freezing over the surface.

217. If too much water is not withdrawn from the cells of many plants in
freezing, and they are thawed out slowly, the water which was withdrawn
from the cells will be absorbed again and the plant will not be killed. But
if the plant is thawed out quickly the water will not be absorbed, but will
remain on the surface and evaporate. Some will also remain in the inter-
cellular spaces, and the plant will die. Some plants, however, no matter how

92 PHYSIOLOGY.

slowly they are thawed out, are killed after freezing, as the leaves of the
pumpkin, dahlia, or the tubers of the potato.

218. It has been found that as a general rule when plants, or plant parts,
contain little moisture they will withstand quite high degrees of tempera-
ture, as well as quite low degrees, but when the parts are filled with sap or
water they are much more easily killed. For this reason dry seeds and the
winter buds of trees, and other plants, because they contain but little water,
are better able to resist the cold of winters. But when growth begins in the
spring, and the tissues of these same parts become turgid and filled with
water, they are quite easily killed by frosts. It should be borne in mind,
however, that there is great individual variation in plants in this respect,
some being more susceptible to cold than others. There is also great varia-
tion in plants as to their resistance to the cold of winters, and of arctic
climates, the plants of the latter regions being able to resist very low tem-
peratures. We have examples also in the arctic plants, and those which
grow in arctic climates on high mountains, of plants which are able to carry
on all the life functions at temperatures but little above freezing.

MORPHOLOGY AND LIFE HISTORY OF REPRE-
SENTATIVE PLANTS.

CHAPTER XV.

SPIROGYRA.

219. In our study of protoplasm and some of the processes of
plant life we became acquainted with the general appearance of
the plant spirogyra. It is now a familiar object to us. And in
taking up the study of representative plants of the different
groups, we shall find that in knowing some of these lower plants
the difficulties of understanding methods of reproduction and
relationship are not so great as they would be if we were entire-
ly ignorant of any members of the lower groups.

220. Form of spirogyra. — We have found that the plant
spirogyra consists of simple threads, with cylindrical cells
attached end to end. We have also noted that each cell of the
thread is exactly alike, with the exception of certain "hold-
fasts " on some of the species. If we should examine threads in
different stages of growth we should find that each cell is capable
of growth and division, just as it is capable of performing all the
functions of nutrition and assimilation. The cells of spirogyra
then multiply by division. Not simply the cells at the ends of
the threads but any and all of the cells divide as they grow, and
in this way the threads increase in length.

221. Multiplication of the threads. — In studying living material of this
plant we have probably noted that the threads often become broken by two of
the adjacent cells of a thread becoming separated. This may be and is accom-

93

94

MORPHOLOG V.

plished in many cases without any injury to the cells. In this manner the
threads or plants of spirogyra, if we choose to call a thread a
plant, multiply, or increase. In this breaking of a thread the
cell wall which separates any two cells splits. If we should
examine several species of spirogyra we would probably find
threads which present two types as regards the character of
the walls at the ends of the cells. In fig. 85 we see that the
ends are plain, that is, the cross walls are all straight. But
in some other species the inner wall of the cells presents a
peculiar appearance. This inner wall at the end of the
cell is at first straight across. But it soon becomes folded
back into the interior of its cell, just as the end of an
empty glove finger may be pushed in. Then the infolded
end is pushed partly out again, so that a peculiar figure is
the result.

222. How some of the threads break. — In the separation
of the cells of a thread this peculiarity is often of advan-
tage to the plant. The cell-sap within the protoplasmic
membrane absorbs water and the pressure pushes on the
ends of the infolded cell walls. The inner wall being so
much longer than the outer wall, a pull is exerted on the
latter at the junction of the cells. Being weaker at this
point the outer wall is ruptured. The turgidity of the two
cells causes these infolded inner walls to push out suddenly
as the outer wall is ruptured, and the thread is snapped
apart as quickly as a pipe-stem may be broken.

223. Conjugation of spirogyra. — Under cer-
tain conditions, when vegetative growth and
multiplication cease, a process of reproduction
takes place which is of a kind termed sexual repro-
duction. If we select mats of spirogyra which
have lost their deep green color, we are likely to
find different stages of this sexual process, which
in the case of spirogyra and related plants is called
conjugation. A few threads of such a mat we

gyra, showing long should examine with the microscope. If the

cells, chlorophyll

band, nucleus, material is in the right condition we will see in

strands of proto-
plasm, and the certain of the cells an oval or elliptical body.

granular wall layer

of protoplasm. If we note carefully the cells in which these oval
bodies are situated, there will be seen a tube at one side which con-

Fig. 85.

Thread of spinr

SPIROC YRA.

95

nects with an empty cell of a thread which lies near as shown in

fig. 86. If we search through the material we may see other threads

connected in this ladder fashion, in which

the contents of the cells are in various stages

of collapse from what we have seen in the

growing cell. In some the protoplasm and

chlorophyll band have moved but little from

the wall \ in others it forms a mass near the

center of the cell, and again in others we

will see that the contents of the cell of one

of the threads has moved partly through the

tube into the cell of the thread with which it

is connected.

224. This suggests to us that the
oval bodies found in the cells of one
thread of the ladder, while the cells
of the other thread were empty, are
formed by the union of the contents
of the two cells. In fact that is what
does take place. This kind of union
of the contents of two similar or nearly
similar cells is conjugation. The oval
bodies which are the result of this
conjugation are zygotes, or zygospores.
When we are examining living ma-
terial of spirogyra in this stage it is /
possible to watch this process of con-
jugation. Fig. 87 represents the differ- Fig. 86.

ent stages of conjugation of spirogyra. Zygospores of spirogyra.

225. How the threads conjugate, or join. — The cells of two
threads lying parallel put out short processes. The tubes from
two opposite cells meet and join. The walls separating the con-
tents of the two tubes dissolve so that there is an open communi-
cation between the two cells. The contents of each one of these
cells which take part in the conjugation is a gamete. The one
which passes through the tube to the receiving cell is the supply-

QO MO RP HO LOG Y.

mg gamete, while that of the receiving cell is the receiving
gamete.

226. How the protoplasm moves from one cell to another. — Before any
movement of the protoplasm of the supplying cell takes place we can see

Fig. 87.

Conjugation in spirogyra ; from left to right beginning in the upper row is shown the
gradual passage of the protoplasm from the supplying gamete to the receiving gamete.

that there is great activity in its protoplasm. Rounded vacuoles appear
which increase in size, are filled with a watery fluid, and swell up like a
vesicle, and then suddenly contract and disappear. As the vacuole disap-
pears it cause s a sudden movement or contraction of the protoplasm around
it to take its place. Simultaneously with the disappearance of the vacuole
the membrane of the protoplasm is separated from a part of the wall. This
is probably brought about by a sudden loss of some of the water in the cell-
sap. These activities go on, and the protoplasmic membrane continues to
slip away from the wall. Every now and then there is a movement by
which the protoplasm is moved a short distance. It is moved toward the
tube and finally a portion of it with one end of the chlorophyll band begins
to move into the tube. Alx>ut this time the vacuoles can be seen in an
active condition in the receptive cell. At short intervals movement con-

SPIROGYRA.

97

tinues until the content of the supplying cell has passed over into that of the
receptive cell. The protoplasm of this one is now slipping away from the
cell wall, until finally the two masses round up into the one zygospore.

227. The zygospore. — This zygospore now acquires a thick wall which
eventually becomes brown in color. The chlorophyll color fades out, and a
large part of the protoplasm passes into an oily substance which makes it
more resistant to conditions which would be fatal to the vegetative threads.
The zygospores are capable therefore of enduring extremes of cold and dry-
ness which would destroy the threads. They pass through a "resting"
period, in which the water in the pond may be frozen, or dried, and with the
oncoming of favorable conditions for growth in the spring or in the autumn
they germinate and produce the green thread again.

228. Life cycle. — The growth of the spirogyra thread, the conjugation of
the gametes and formation of the zygospore, and the growth of the thread
from the zygospore again, makes what is called a complete life cycle.

229. Fertilization. — While conjugation results in the fusion of the two
masses of protoplasm, fertilization is accomplished when the nuclei of the
two cells come together in the zygospore and fuse into a single nucleus. The

Fertilization in spirogyra ; shows different stages of fusion of the two nuclei, with mature
zygospore at right. (After Overton.)

different stages in the fusion of the two nuclei of a recently formed zygospore
are shown in figure 88.

In the conjugation of the two cells, the chlorophyll band of the supplying
cell is said to degenerate, so that in the new plant the number of chlorophyll
bands in a cell is not increased by the union of the two cells.

230. Simplicity of the process. — In spirogyra any cell of the thread
may form a gamete (excepting the holdfasts of some species). Since all of
the cells of a thread are practically alike, there is no structural difference
between a vegetative cell and a cell about to conjugate. The difference is a
physiological one. All the cells are capable of conjugation if the physiolog-
ical conditions are present. All the cells therefore are potential gametes.
(Strictly speaking the wall of the cell is the gametangiwn, while the contents
make the gamete.)

While there is sometimes a slight difference in size between the conjugat

98

MORPHOLOG Y.

ing cells, and the supplying cell may be the smaller, this is not general. We
say, therefore, that there is no differentiation among the gametes, so that
usually before the protoplasm begins to move one cannot say which is to be
the supplying and which the receiving gamete.

231. Position of the plant spirogyra. — From our study then we see that
there is practically no differentiation among the vegetative cells, except
where holdfasts grow out from some of the cells for support. They are all
alike in form, in capacity for growth, division, or multiplication of the
threads. Each cell is practically an independent plant. There is no differ-
entiation between vegetative cell and conjugating cell. All the cells are
potential gametes. Finally there is no structural differentiation between the
gametes. This indicates then a simple condition of things, a low grade of
organization.

232. The alga spirogyra is one of the representatives of the lower algae
belonging to the group called Conjugatce. Zygnema with star-shaped chloro-
plasts, mougeotia with straight or sometimes twisted chlorophyll bands, be-
long to the same group. In the latter genus only a portion of the protoplasm
of each cell unites to form the zygospore, which is located in the tube between
the cells.

Fig. 90.
Micrasterias.

Fig. 91.
Xanthidium.

Fig. 89.
Closterium.

Fig. 92-
Staurastrum.

Fig. 94.
Cosmarium.

233. The desmids also belong to the same group. The desmids usually live
as separate cells. Many of them are beautiful in form. They grow entangled
among other algae, or on the surface of aquatic plants, or on wet soil. Sev-
eral genera are illustrated in figures 89-94.

CHAPTER XVI.

CEDOGONIUM.

234. CEdogonium is also an alga. The plant is sometimes
associated with spirogyra, and occurs in similar situations. Our
attention was called to it in the study of chlorophyll bodies.
These we recollect are, in this plant, small oval disks, and thus
differ from those in spirogyra.

235. Form of redogonium. — Like spirogyra, cedogonium
forms simple threads which are made up of cylindrical cells
placed end to end. But the plant is very different from any
member of the group to which spirogyra belongs. In the first
place each cell is not the equivalent of an individual plant as in
spirogyra. Growth is localized or confined to certain cells of
the thread which divide at one end in such a way as to leave a
peculiar overlapping of the cell walls in the form of a series of
shallow caps or vessels (fig. 95), and this is one of the character-
istics of this genus. Other differences we find in the manner of
reproduction.

236. Fruiting stage of oedogonium. — Material in the fruiting
stage is quite easily obtainable, and may be preserved for study
in formalin if there is any doubt about obtaining it at the time
we need it for study. This condition of the plant is easily de-
tected because of the swollen condition of some of the cells, or
by the presence of brown bodies with a thick wall in some of the
cells.

237. Sexual organs of oedogonium. Oogonium and egg.—
The enlarged cell is the oogonium, the wall of the cell being the
wall of the oogonium. (See fig. 96. ) The protoplasm inside, before

99

100

MO RP HO LOG Y.

fertilization, is the egg cell. In those cases where the brown body
with a thick wall is present fertilization has taken place, and this
body is \hz fertilized egg , oroospore. It contains
large quantities of an oily substance, and, like

Fig. 95- '

Portion o f
thread of cedo-
gonium, show-
ing chlorophyll
grains, and pe-
culiar cap cell
walls.

1'ig. 96.

CEdogonium undulatum, with oogonia and dwarf males;
the upper oogonium at the right has a mature oospore.

the fertilized egg of spirogyra and vaucheria, is able to with-
stand greater changes in temperature than the vegetative stage,
and can endure drying and freezing for some time without
injury.

In the oogonium wall there can frequently be seen a rift near
the middle of one side, or near the upper end. This is the

(EDOGONIUM.

101

opening through which the spermatozoid entered to fecundate
the egg.

238. Dwarf male plants. — In some species there will also be
seen peculiar club-shaped dwarf plants attached to the side of the
oogonium, or near it, and in many cases the end of this dwarf
plant has an open lid on the end.

239. Antheridium. — The end cell of the dwarf male in such
species is the antheridium. In other species the spermatozoids
are developed in different cells (antheridia) of the same thread
which bears the oogonium, or on a different thread.

240. Zoospore stage of oedogonium. — The egg after a period of rest starts
into active life again. In doing so it does not develop the thread-like plant
directly as in the case of vaucheria and spirogyra. It first divides into four
zoospores which are exactly like the zoogonidia in form. (See fig. 103.)
These germinate and develop the thread form again. This is a quite re-
markable peculiarity of oedogonium when compared with either vaucheria
or spirogyra. It is the introduction of an intermediate stage between the
fertilized egg and that form of the plant which bears the sexual organs, and
should be kept well in mind.

241. Asexual reproduction. — Material for the study of this stage of oedo-
gonium is not readily obtainable just when we wish it for study. But fresh
plants brought in and placed in a

quantity of fresh water may yield
suitable material, and it should be
examined at intervals for several
days. This kind of reproduction
takes place by the formation of
zoogonidia. The entire contents
of a cell round off into an oval

Fig. 97.

Zoogonidia of osdogonium escaping.
At the right one is germinating and
forming the holdfasts, by means of which
these algae attach themselves to objects
for support. (After Pringsheim.)

body, the wall of the cell breaks,

and the zoogonidium escapes. It

has a clear space at the small

end, and around this clear space

is a row or crown of cilia as shown in fig. 97. By the vibration of these cilia

the zoogonidium swims around for a time, then settles down on some object of

support, and several slender holdfasts grow out in the form of short rhizoids

which attach the young plant.

242. Sexual reproduction. Antheridia. — The antheridia are short cells
which are formed by one of the ordinary cells dividing into a number of
disk-shaped ones as shown in fig. 98. The protoplasm in each antheridium

102

MO RP HO LOG Y.

forms two spermatozoids (sometimes only one) which are of the same form as
the zoogonidia but smaller, and yellowish instead of green. In some species

a motile body intermedi-
ate in size and color be-
tween the spermatozoids
and zoogonidia is first
formed, which after
swimming around comes
to rest on the oogonium,
or near it, and develops
what is called a " dwarf
male plant " from which
the real spermatozoid is
produced.

Portionof'hSadof cedo- ^ Oogonia. - The
gonium showing upper half oogonia are formed di-
' :gg open, and a sperma- ,, r
)id ready to enter. (After rectl7 from one of the
vegetative cells. In most
species this cell first enlarges in diameter, so that it is easily detected. The
protoplasm inside is the egg cell. The oogonium wall opens, a bit of the
protoplasm is emitted, and the spermatozoid then' enters and fertilizes it
(fig. 99). Now a hard brown wall is formed around it, and, just as in spirogyra

Fig. 98.

Portion of thread
o f oedogonium
showing antheridia

of eg
tozoi
Oltmans).

Fig. 100.

Male nucleus Just entering
egg at left side.

Fig. 101.

Male nucleus fusing with
female nucleus.

Fig. 102.

The two nuclei fused, and
fertilization complete.

Figs. 100-102. — Fertilization in cedogonium. (After OltmansK

a.nd vaucheria, it passes through a resting period. At the time of germination
it does not produce the thread-like plant again directly, but first forms four
zoospores exactly like the zoogonidia (fig. 103). These zoospores then
germinate and form the plant.

244. (Edogonium compared with spirogyra. — Now if we compare oedo-
gonium with spirogyra, as we did in the case of vaucheria, we will find here
also that there is an advance upon the simple condition which exists in spiro-
gyra. Growth and division of the thread is limited to certain portions. The
sexual organs are differentiated. They usually differ in form and size from
the vegetative cells, though the oogonium is simply a changed vegetative

(EDOGONIUM.

I03

cell. The sexual organs are differentiated among themselves, the antheridium
is small, and the oogonium large. The gametes are also differentiated in
size, and the male gamete is motile, and carries in its body the nucleus
which fuses with the nucleus of the egg cell.

But a more striking advance. is the fact that the fertilized egg does not

Fig. 103.

Fertilized egg of oedogonium after a period of rest escaping from the wall of the oogonium,
and dividing into the four zoospores. (After Juranyi.)

produce the vegetative thread of oedogonium directly, but first forms four

zoospores, each of which is then capable of developing into the thread. On

the other hand we found

that in spirogyra the zygo-

spore develops directly

into the thread form of the

plant.

245. Position of oado-
gonium. — CEdogonium is
one of the true thread-like
algae, green in color, and
the threads are divided
into distinct cells. It,
along with many relatives,
was once placed in the old

genus conferva. These are all now placed in the group
Confervoidea, that is, the conferva-like alga. pig I05

246. Kelatives of redogonium. — Many other genera Portion of chastophora
* , j , j . c -j.r-1 showing branching.

are related to oedogonium. Some consist of simple

threads, and others of branched threads. An example of the branched
forms is found in choetophora, represented in figures 104, 105. This plant
grows in quiet pools or in slow-running water. It is attached to sticks, rocks,
or to larger aquatic plants. Many threads spring from the same point of
attachment and radiate in all directions. This, together with the branching
of the threads, makes a small, compact, greenish, rounded mass, which is

Fig. 104.
Tuft of chaeto-
phora, natural
size.

104 MORPHOLOG Y.

held firmly together by a gelatinous substance. The masses in this species
are about the size of a small pea, or smaller. Growth takes place in chae-
tophora at the ends of the threads and branches. That is, growth is api-
cal. This, together with the branched threads and the tendency to form
cell masses, is a great advance of the vegetative condition of the plant upon
that which we find in the simple threads of cedogonium.

CHAPTER XVII.

VAUCHERIA.

247. The plant vaucheria we will remember from our study
in an earlier chapter. It usually occurs in dense mats floating
on the water or lying on damp soil. The texture and feeling of
these mats remind one of "felt,"

and the species are sometimes called
the " green felts." The branched
threads are continuous, that is there
are no cross walls in the vegetative
threads. This plant multiplies it-
self in several ways which would
be too tedious to detail here. But
when fresh bright green mats can be
obtained they should be placed in
a large vessel of water and set in
a cool place. Only a small amount
of the alga should be placed in a
vessel, since decay
will set in more
rapidly with a large
quantity. For

several days one
should look for

small green bodies which may be floating at the side of the vessel
next the lighted window.

248. Zoogonidia of vaucheria. — If these minute floating green bodies are
found, a small drop of water containing them should be mounted for exami-

105

Fig. 106.
Portion of branched thread of vaucheria.

IO6 MORPHOLOGY.

nation. If they are rounded, with slender hair-like appendages over the
surface, which vibrate and cause motion, they very likely are one of the
kinds of reproductive bodies of vaucheria. The hair-like appendages are
cilia, and they occur in pairs, several of them distributed over the surface.
These rounded bodies are gonidia, and because they are motile they are
called zoogonidia.

By examining some of the threads in the vessel where they occurred we
may have perhaps an opportunity to see how they are produced. Short
branches are formed on the threads, and the contents are separated from
those of the main thread by a septum. The protoplasm and other contents of
this branch separate from the wall, round up into a mass, and escape through
an opening which is formed in the end. Here they swim around in the
water for a time, then come to rest, and germinate by growing out into a
tube which forms another vaucheria plant. It will be observed that this
kind of reproduction is not the result of the union of two different parts of
the plant. It thus differs from that which is termed sexual reproduction. A
small part of the plant simply becomes separated from it as a special body,
and then grows into a new plant, a sort of multiplication. This kind of re-
production has been termed asexual reproduction.

249. Sexual reproduction in vaucheria. — The organs which are concerned
in sexual reproduction in vaucheria are very readily obtained for study if
one collects the material at the right season. They are found quite readily
during the spring and autumn, and may be preserved in formalin for study
at any season, if the material cannot be collected fresh at the time it is
desired for study. Fine material for study often occurs on the soil of pots in

greenhouses during the winter.
While the zoogonidia are more
apt to be found in material
which is quite green and fresh-
ly growing, the sexual organs
are usually more abundant
when the threads appear some-
what ye' owish, or yellow
green.

250. Vaucheria sessi-
Fig- I07 lis ; the sessile vauche-

Young antheridium and oogonium of Vaucheria ses- . T , . , ,

silis, before separation from contents of thread by a Tia. In tniS plant me

sexual organs are sessile,

that is they are not borne on a stalk as in some other species.
The sexual organs usually occur several in a group. Fig. 107
represents a portion of a fruiting plant.

VAUCHERIA.

107

251. Sexual organs of vaucheria. Antheridium. — The

antheridia are short, slender, curved branches from a main
thread. A septum is formed which separates an end portion
from the stalk. This end cell is the antheridium. Frequently it
is collapsed or empty as shown in fig. 108. The protoplasm in

Fig 108.
Vaucheria sessilis, one antheridium between two oogonia.

the antheridium forms numerous small oval bodies each with two
slender lashes, the cilia. When these are formed the antherid-
ium opens at the end and they escape. It is after the escape
of these spermatozoids that the antheridium is collapsed. Each
spermatozoid is a male gamete.

252. Oogonium. — The oogonia are short branches also, but
they become large and , »

somewhat oval. The / *

septum which separates the
protoplasm from that of
the main thread is as we
see near the junction of
the branch with the main
thread. The oogonium,
as shown in the figure, is
j usually turned somewhat
to one side. When mature the pointed end opens and a bit of the
protoplasm escapes. The remaining protoplasm forms the large
rounded egg cell which fills the wall of the oogonium. In some
of the oogonia which we examine this egg is surrounded by a
thick brown wall, with starchy and oily contents. This is the

Fig. 109.

Vaucheria sessilis ; oogonium opening and emit-
ting a bit of protoplasm; spermatozoids; sperma-
tozoids entering oogonium. (After Pringsheim and
Goebel.)

loS

MORPHOLOG

fertilized egg (sometimes called here the oospore). It is freed
from the oogonium by the disintegration of the latter, sinks into

Fertilization in vaucheria. »««, male nucleus ; ./«, female nucleus. Male nucleus entering
the egg and approaching the female nucleus. (After Oltmans.)

the mud, and remains here until the following autumn or spring,
when it grows directly into a new plant.

253. Fertilization. — Fertilization is accomplished by the
spermatozoids swimming in at the open end of the oogonium,

Fig. in.

Fertilization of vaucheria. fn, female nucleus; mn, male nucleus. The different figures
show various stages in the fusion of the nuclei.

when one of them makes its way down into the egg and fuses
with the nucleus of the egg.

254. The twin vaucheria (V. geminata). — Another species of vaucheria
is the twin vaucheria. This is also a common one, and may be used for
study instead of the sessile vaucheria if the latter cannot be obtained. The
sexual organs are borne at the end of a club-shaped branch. There are
usually two oogonia, and one antheridium between them which terminates
the branch. In a closely related species, instead of the two oogonia there is
a whorl of them with the antheridium in the center.

255. Vaucheria compared with spirogyra.— In vaucheria we have a plant
which is very interesting to compare with spirogyra in several respects.

VAUCHERIA. IC>9

Growth takes place, not in all parts of the thread, but is localized at the ends
of the thread and its branches. This represents a distinct advance on such
a plant as spirogyra. Again, only specialized parts of the plant in vaucheria
form the sexual organs. These are short branches. Farther there is a great
difference in the size of the two organs, and especially in the size of the
gametes, the supplying gametes (spermatozoids) being very minute,
while the receptive gamete is large and contains all the nutriment for the
fertilized egg. In spirogyra, on the other hand, there is usually no differ-
ence in size of the gametes, as we have seen, and each contributes equally in
the matter of nutriment for the fertilized egg. Vaucheria, therefore, rep-
resents a distinct advance, not only in the vegetative condition of the plant,
but in the specialization of the sexual organs. Vaucheria, with other related
algae, belongs to a group known as the Siphonece, so called because the plants
are tube-like or sihon-like.

CHAPTER XVIII.

COLEOCH^TE.

256. Among the green algae coleochaete is one of the most
interesting. Several species are known in this country. One
of these at least should be examined if it is possible to obtain it.
It occurs in the water of fresh lakes and ponds, attached to
aquatic plants.

257. The shield-shaped coleochsete. — This plant (C. scutata)

Fig. 112.

Stem o f
aquatic plant
showing co-
leo cha? t e,
natural size.

Fig. 113.
Thallus of Coleochaete scutata.

is in the form of a flattened, circular, green plate, as shown in
fig. 112. It is attached near the center on one side to rushes

no

COLEOCHMTE.

Ill

and other plants, and has been found quite abundantly for sev-
eral years in the waters of Cayuga Lake at its southern extremity.
As will be seen it consists of a single layer of green cells which
radiate from the center in branched rows to the outside, the cells
lying so close together as to form a continuous plate. The plant
started its growth from a single cell at the central point, and grew
at the margin in all directions. Sometimes they are quite irregu-
lar in outline, when they lie quite closely side by side and inter-
fere with one another by pressure. If the surface is examined
carefully there will be found long hairs, the base of which is en-
closed in a narrow sheath. It is from this character that the
genus takes its name of coleochsete (sheathed hair).

258. Fruiting stage of coleochaete. — It is possible at some
seasons of the year to find rounded masses of cells situated near
the margin of this green disk. These have developed from a
fertilized egg which remained attached to the plant, and prob-
ably by this time the parent plant has lost its color.

259. Zoospore stage. — This mass of tissue does not develop
directly into the circular green disk, but each of the cells forms
a zoospore. Here then, as

in cedogonium, we have an-
other stage of the plant in-
terpolated between the fer-
tilized egg and that stage
of the plant which bears the
gametes. But in coleochaete
we have a distinct advance in
this stage upon what is pres-
ent in cedogonium, for in
^coleochaete the fertilized
egg develops first into a

several-celled mass of tissue Pringsheim.) Pringsheim.)

before the zoospores are formed, while in cedogonium only four
zoospores, are formed directly from the egg.

260. Asexual reproduction. — In asexual reproduction any of the green
cells on the plant may form zoogonida.

Portion of thallus
of Coleochaete
scutata, showing
four antheridia
formed from one
thallus cell ; a sin-
gle spermatozoidat
the right. (After

The contents of a cell round off and

112

MORPHOLOGY.

form a single zoogonidium which has two cilia at the smaller end of the oval
body, fig. 114. After swimming around for a time they come to rest, ger-
minate, and produce another plant.

261. Sexual reproduction. — Oogonium. — The oogonium is formed by the
enlargement of a cell at the end of one of the threads, and then the end of the

Oog—

Coleochaste soluta ; at left branch bearing oogonium (oog) ; antheridia (ant); egg in
oogonium and surrounded by enveloping threads ; at center three antherMia open, and one
spermatozoid ; at right sporocarp, mature egg inside sporocarp wall.

cell elongates into a slender tube which opens at the end to form a channel
through which the spermatozoid may pass down to the egg. The egg is
formed of the contents of the cell (fig. 116). Several oogonia are formed on

one plant, and in such a
plant as C. scutata they are
formed in a ring near the
margin of the disk.

262. Antheridia.— In C.
scutata certain of the cells
of the plant divide into four
smaller cells, and each one
of these becomes an antheri-
dium. In C. soluta the an-
theridia grow out from the
end of terminal cells in the
Figs. 117, 118, C. scutata. form of short flasks, some-

times four in number or less (fig. 116). A single spermatozoid is formed
from the contents. It is oval and possesses two long cilia. After swim-

Fig. 117.

Two sporocarps still
surrounded by thallus.
Thallus finally decays and
sets sporocarp free.

Fig. 118.

Spororarp ruptured b }
growth of egg to form cefl
mass. Cells of this sporo-
phyte forming zoospores.

COLEOCH& TE. 1 1 3

ming around it passes down the tube of the oogonium and fertilizes the

egg-

263. Sporocarp. — After the egg is fertilized the cells of the threads near
the egg grow up around it and form a firm covering one cell in thickness.
This envelope becomes brown and hard, and serves to protect the egg. This
is the "fruit" of the coleochaete, and is sometimes called a sporocarp
(spore fruit). The development of the cell mass and the zoospores from the
egg has been described above.

Some of the species of coleochsete consist of branched threads, while others
form circular cushions several layers in thickness. These forms together
with the form of our plant C. scutata make an interesting series of transi-
tional forms from filamentous structures to aii expanded plant body formed
of a mass of cells.

114

MOKPHOLOG Y.

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CHAPTER XIX.

BROWN AND RED ALGvE.

265. If it is desired to extend the study of the algge to other groups,
especially to some of the marine forms, examples of the brown algae and of
the red algge may be obtained. These are accessible at the seashore, and
for inland laboratories material may be preserved in formalin (2%%).

266 The brown algae (Phaeophyceae).* — A good representative of one
division of the brown algae and one often used for study is the genus fitctts.

267. Form and occurrence of fucus. — This plant is a more or less
branched and flattened thallus or "frond." One of them, illustrated in fig.
119, measures i^-^ocm (6-12 inches) in length. It is attached to rocks
and stones which are more or less exposed at low tide. From the base of the
plant are developed several short and more or less branched expansions
called "holdfasts," which, as their name implies, are organs of attachment.
Some species (F. vesiculosus) have vesicular swellings in the thallus.

The fruiting portions are somewhat thickened as shown in the figure.
Within these portions are numerous oval cavities opening by a circular pore,
which gives a punctate appearance to these fruiting cushions. Tufts of hairs
frequently project through them.

268. Structure of the conceptacles. — On making sections of the fruiting
portions one finds the walls of the cavities covered with outgrowths. Some
of these are short branches which bear a large rounded terminal sac, the
oogonium, at maturity containing eight egg cells. More slender and much
branched threads bear narrowly oval antheridia. In these are developed
several two-ciliated spermatozoids.

269. Fertilization. — At maturity the spermatozoids and egg cells float out-
side of the oval cavities where fertilization takes place. The spermatozoid
sinks into the protoplasm of the egg cell, makes its way to the nucleus of
the egg, and fuses with it as shown in fig. 125. The fertilized egg then
grows into a new plant. Nearly all the brown algae are marine.

* The members of the group possess chlorophyll, but it is obscured by a
brown pigment.

i6

MORPHOLOG Y.

270. The red algae (Rhodophyceae). — The larger number of the so-called
red algse occur in salt water, though a few genera occur in fresh water.

Fig. u9.

Portion of plant of fucus showing
conceptacles in enlarged ends ; and
below the vesicles (Fucus vescicu-
losus).

Fig. 120.

Section of conceptacle of fucus, showing
oogonia, and tufts of antheridia.

(Lemanea grows only in winter in turbulent water of quite large streams.
Batrachospermum grows in rather slow-running water of smaller streams.
Both of these inhabit fresh water.) The plants of the group possess chloro-
phyll, but it is usually obscured by a reddish or purple pigment.

271. Gracillaria — Gracillaria is one of the marine forms, and one species
is illustrated in fig. 126. It measures i$-2Ocm or more long, and is pro-
fusely branched in a palmate manner. The parts of the thallus are more or
less flattened. The fruit is a cystocarp, which is characteristic of the rhodo-

BROWN AND RED ALG&.

117

phyceae (floridese). In gracillaria these fruit bodies occur scattered over
the thallus. They are somewhat flask-shaped, are partly sunk in the

Fig. 122. Fig. 123. Fig. 124.

Antheridia of fucus, on Antheridia of fucus with Egg of fucus surrounded
branched threads. escaping spermatozoids. by spermatozoids.

thallus, and the conical end projects strongly above the surface. The car-
pospores are grouped in radiating threads within the oval c- vity of the

Fig. 125.

Fertilization in fucus ; fn, female nucleus ; mn, male nucleus; n, nucleolus. In the left
figure the male nucleus is shown moving down through the cytoplasm of the egg ; in the
remaining figures the cytoplasm of the egg is omitted. (After Strasburger.)

cystocarp. These cystocarps are developed as a result of fertilization.
Other plants bear gonidia in groups of four, the so-called tetraspores.

272. Rhabdonia. — This plant is about the same size as the gracillaria,
though it possesses more filiform branches. The cystocarps form prominent
elevations, while the carpospores lie in separated groups around the periph-
ery of a sterile tissue within the cavity. (See figs. 128, 129.) Gonidia in
the form of tetraspores are also developed in rhabdonia.

u8

MORPHOLOGY.

Fig. 126. Fig. 127.

Gracillaria, portion of frond, Gracillaria, section of cystocarp

showing position of cysto- showing spores,
carps.

273. The principal groups of the algae are the following :

Chlorophycea.
Green algae.

Protococcoideae (the protococcus (Pleurococ-

cus vulgaris); the red-snow plant (Sphaerella

nivalis), etc.
Conjugateae (spirogyra, zygnema, mougeotia,

desmids, etc.).
Siphoneae (vaucheria).
Confervoideae (cedogonium, chaetophora, cole-

ochaete).

Cyanophycece (nostoc, oscillatoria, etc.). The blue-green algae.
Phceophycece, (fucus, etc.). The brown algae.

BROWN AND RED

Rhodophycece (rhabdonia, gracillaria, callithamnion, champia,

etc.). The red algae.

274. Some of the protococcoideae are believed to lie very near

some of the lower animals like the flagellates. They are mostly
single-celled plants ; some of them are
motile during the vegetative stage, and
others are not motile, while others are

Fig. I28.

Rhabdonia, branched
portion of frond show-

Fig. 129.

Section of cystocarp of rhabdonia, showing
spores.

ing cystocarps.

motile during certain stages. The red-snow plant
may be obtained by scraping the red-looking
matter out of the bottom of dry shallow basins in
the rocks, close by fresh-water streams or lakes.
By placing some of this material in a vessel of
water for a few days the motile stage may be pk J*cc'u3s0-(pro_

obtained. The protococcus, or Pleurococcus vul- tococcus)
garis, may be obtained on the north side of trees, rocks, 'and
walls, in damp places.

CHAPTER XX.

FUNGI : MUCOR AND SAPROLEGNIA.

Mucor.

275. In the chapter on growth, and in our study of proto-
plasm, we have become familiar with the vegetative condition of
mucor. We now wish to learn how the plant multiplies and re-
produces itself. For this study we may take one of the mucors.
Any one of several species will answer. This plant may be grown
by placing partially decayed fruits, lemons, or oranges, from which
the greater part of the juice has been removed, in a moist cham-
ber ; or often it occurs on animal excrement when placed under
similar conditions. In growing the mucor in this way we are
likely to obtain Mucor mucedo, or another plant sometimes
known as Mucor stolonifer, or Rhizopus nigricans, which is illus-
trated in fig. 132. This latter one is sometimes very injurious to
stored fruits or vegetables, especially sweet potatoes or rutaba-
gas. Fig. 131 is from a photograph of this fungus on a banana.

276. Asexual reproduction. — On the decaying surface of the
vegetable matter where the mucor is growing there will be seen
numerous small rounded bodies borne on very slender stalks.
These heads contain the gonidia, and if we sow some of them in
nutrient gelatine or agar in a Petrie dish the material can be
taken out very readily for examination under the microscope.
Or we may place glass slips close to the growing fungus in the
moist chamber, so that the fungus will develop on them, though
cultures in a nutrient medium are much better. Or we may take
the material directly from the substance on which it is growing.

FUNGI: MUCOR.

121

After mounting a small quantity of the mycelium bearing these
heads, if we have been careful to take it where the heads appear
quite young, it may be possible to study the early stages of their

Fig, 131.
Portion of banana with a mould (Rhizopus nigricans) growing on one end.

development. We will probably note at once that the stalks or
upright threads which support the heads are stouter than the
threads of the mycelium.

These upright threads soon have formed near the end a cross
wall which separates the protoplasm in the end from the remain-
der. This end cell now enlarges into a vesicle of considerable
size, the head as it appears, but to which is applied the name of
sporangium (sometimes called gonidangium), because it encloses
the gonidia.

At the same time that this end cell is enlarging the cross wall
is arching up into the interior. This forms the columella. All
the protoplasm in the sporangium now divides into gonidia.
These are small rounded or oval bodies. The wall of the spo-

1 2 2 MORPHOLOG Y.

rangium becomes dissolved, except a small collar around the
stalk which remains attached below the columella (fig. 133).

Fig. 132.

Group of sporangia of a mucor (Rhizopus nigricans) showing rhizoids and the stolon extend-
ing from an older group.

By this means the gonidia are freed. These gonidia germinate
and produce the mycelium again.
i

277. Sexual stage. — This stage is not so frequently found, but may some-
times be obtained by growing the fungus on bread.

Conjugation takes place in this way. Two threads of the mycelium which
lie near each other put out each a short branch which is clavate in form.
The ends of these branches meet, and in each a septum is formed which cuts
off a portion of the protoplasm in the end from that of the rest of the my-
celium. The meeting walls of the branches now dissolve and the protoplasm
of each gamete fuses into one mass. A thick wall is now formed around this
mass, and the outer layer becomes rough and brown. This is the zygote or
zygospore. The mycelium dies and it becomes free often with the suspensors,
as the stalks of these sexual'branches are called, still attached. This zygo-
spore passes through a period of rest, when with the entrance of favorable
conditions of growth it germinates, and usually produces directly a sporan-
gium with gonidia. This completes the normal life cycle of the plant.

278. Gemmae. — Gemmae, as they are sometimes called, are often formed on
the mycelium. A short cell with a stout wall is formed on the side of a

FUNGI : SA PROLEGNIA .

123

thread of the mycelium. In other cases large portions of the threads of the
mycelium may separate into chains of cells.. Both these kinds of cells are

A mucor (Rhizopus nigricans) ; at left nearly mature sporangium with columella showing
within; in the middle is ruptured sporangium with some of the gonidia clinging to the colu-
mella ; at right two ruptured sporangia with everted columella.

capable of growing and forming the mycelium again,
called chlamy do spores.

They are sometimes

Water Moulds (Saprolegnia).

279. The water moulds are very interesting plants to study
because they are so easy to obtain, and it is so easy to observe a
type of gonidium here to which we have referred in our studies
ofthealgae, the motile gonidium, or zoogonidium. (See appen-
dix for directions for cultivating this mould.)

280. Appearance of the saprolegnia. — In the course of a
few days we are quite certain to see in some of the cultures deli-
cate whitish threads, radiating outward from the body of the fly
in the water. A few threads should be examined from day to
day to determine the stage of the fungus.

281. Sporangia of saprolegnia. — The sporangia of saprolegnia
can be easily detected because they are much stouter than the

124

MORPHOLOGY.

ordinary threads of the mycelium. Some of the threads should
be mounted in fresh water, Search for some of those which

Fig. 134-

Sporangia of saprolegnia, one showing the escape of the zoogo-
» nidia.

show that the protoplasm is divided up into a great number of
small areas, as shown in fig. 134.

With the low power we should watch some of the older ap-
pearing ones, and if after a few minutes they do not open, other
preparations should be made.

282. Zoogonidia of saprolegnia. — The sporangium opens at

Fig. 135-
Branch of saprolegnia showing oogonia with oospores, eggs matured parthenogenetically.

the end, and the zoogonidia swirl out and swim around for a
short time, when they come to rest. With a good magnifying

FUNGI : SA PROLEGNIA .

125

Fig. 136.

Fertilization in saprolegnia, tube of antheridium carrying
n the right-hand figure a smaller
egg. (After Humphrey and Trow.)

the nucleus of the sperm cell

, e

to the egg. In the right-hand figure a smaller sperm nucleus is about to fuse with the
nucleus of the e

Fig. 137-
Branching hypha of Peronospora alsin

Fig. 138.

Branched hypha of downy mildew
of grape showing peculiar branching
(Plasmopara viticola).

126

MORPHOLOG V.

power the two cilia on the end may be seen, or we may make
them more distinct by treatment with Schultz's solution, draw-
ing some under the cover glass. The zoogonidium is oval and
the cilia are at the pointed end. After they have been at rest

Fig. 139-

Downy mildew of grape (Plasmopora viti-
cola), showing tuft of gonidiophpres bearing
gonidia, also intercellular mycelium. (After
Millardet.)

Fig. 140.

Phytophthora infestans showing pe-
culiar branches ; gonidia below.

for some time they often slip out of the thin wall, and swim
again, this time with the two cilia on the side, and then the
zoogonidium is this time more or less bean-shaped or reniform.

283 Sexual reproduction of saprolegnia. — When such cultures are older
we often see large rounded bodies either at the end of a thread, or of a
branch, which contain several smaller rounded bodies as shown in fig. 135.
These are the oogonia (unless the plant is attacked by a parasite), and the
round bodies inside are the egg cells, if before fertilization, or the eggs, if

FUNGI : SA PROLEGNIA .

127

after this process has taken place. Sometimes the slender antheridium can
be seen coiled partly around the oogonium, and one end entering to come in
contact with the egg cell. But in some species the antheridium is not
present, and that is the case with the species figured at 135. In this case

B

Fig. 141. Fig. 142.

Gonidiophores and gonidia of potato blight (Phytophthora in- Gonidia of potato

festans). />, an older stage showing how the branch enlarges where blight forming zoogo-

it grows beyond the older gonidium. (After de Bary.) nidia. vAfter de Bary.)

the eggs mature without fertilization. This maturity of the egg without
fertilization is called parthenogenesis, which occurs in other plants also, but
is a rather rare phenomenon.

284. In fig. 136 is shown the oogonium and an antheridium, and the
antheridium is carrying in the male nucleus to the egg cell. Spermatozoids

Fig. 143-

Fertilization in Peronospora alsinearum ; tube from antheridium carrying in the sperm
nucleus in figure at the left, female nucleus near ; fusion of the two nuclei shown in the two
other figures. (After Berlese.)

are not developed here, but a nucleus in the antheridium reaches the egg
cell. It sinks in the protoplasm of the egg, comes in contact with the nu-
cleus of the egg, and fuses witji )t, Thus fertilization is accomplished.

128

MOXPHOLOG Y.

Downy Mildews.

285. The downy mildews make up a group of plants which are closely
related to the water moulds, but they are parasitic on land plants, and some
species produce very serious diseases. The mycelium grows between the
cells of the leaves, stems, etc., of their hosts, and sends haustoria into the
cells to take up nutriment. Gonidia are formed on threads which grow
through the stomates to the outside and branch as shown in tigs. 137-140.

The gonidia are borne on the tips
of the branches. The kind of
branching bears some relation to
the different genera. Fig. 137 is
from Peronospora alsinearum on
leaves of cerastium; figs. 138
and 139 are Plasmopara viticola,
the grape mildew, while figs. 140
and 141 are from Phytophthora
infestans, which causes a disease
known as potato blight. The
gonidia of peronospora germinate
by a germ tube, those of plasmop-
ara first form zoogonidia, while
in phytophthora the gonidium
may either germinate forming a
thread, or each gonidium may
first form several zoogonidia as shown in fig. 142.

286. In sexual reproduction oogonia and antheridia are developed on the
mycelium within the tissues. Fig. 143 represents the antheridium entering
the oogonium, and the male nucleus fusing with the female nucleus in fertili-
zation. T^he sexual organs of Phytophthora infestans are not known.

287. Mucor, saprolegnia, peronospora, and their relatives have few or
no septa in the mycelium. In this respect they resemble certain of the algae
like vaucheria, but they lack chlorophyll. They are sometimes called the
alga-like fungi and belong to a large group called Phy corny cetes.

Fig. 144-
Ripe oospore of Peronospora alsinearum.

CHAPTER XXI.

FUNGI CONTINUED (RUSTS AND SAC FUNGI).

•' Rusts" (Uredineae).

288. The fungi known as "rusts" are very important ones
to study, since all the species are parasitic, and many produce
serious injuries to crops.

289. Wheat rust (Puccinia graminis). — The wheat rust is
one of the best known of these fungi, since a great deal of study
has been given to it. One form of the plant occurs in long

Fig- 145-

Wheat leaf with red
rust, natural size.

Fig. 146.
Portion of leaf
enlarged to show
sori.

Fig. 147.
Natural size.

Fig. 148.
Enlarged.

Fig. 149.
Single

Figs. 145, 146. — Puccinia graminis, red-rust stage (uredo stage).
Figs. 147-149. — Black rust of wheat, showing sori of teleutospores.

reddish-brown or reddish pustules, and is known as the " red
rust" (figs. 145, 146). Another form occurs in elongated black
pustules, and this form is the one known as, the ' ' black rust ' '

129

1 3o

MOJRPHOLOGY.

(figs. 147-150). These two forms occur on the stems, blades,
etc., of the wheat, also on oats, rye, and some of the grasses.

290. Teleutospores of the black-rust form. — If we scrape off
some portion of one of the black pustules (sori), tease it out

Fig. 151.

Teleutospores of wheat rust,
showing two cells and the pedicel.

150.

Head of wheat showing black rust spots
on the chaff and awns.

Fig. 152.

Uredospores of wheat rust, one
showing remnants of the pedicel.

in water on a slide, and examine with a microscope, we will see
numerous gonidia, composed of two cells, and having thick,
brownish walls as shown in fig. 151. Usually there is a slender
brownish stalk on one end. These gonidia are called teleuto-
spores. They are somewhat oblong or elliptical, a little con-
stricted where the septum separates the two cells, and the end
cell varies from ovate to rounded. The mycelium of the fungus

FUNGI: RUSTS.

courses between the cells, just as is found in the case ot the
carnation rust, which belongs to the same family (see Part III).
291. Uredospores of the red-rust form. — If we make a simi-
lar preparation from the pustules of the red-rust form we will see
that instead of two-celled gonidia they are one-celled. The
walls are thinner and not so dark in color, and they are covered
with minute spines. They have also short stalks, but these fall
away very easily. These one-celled gonidia of the red-rust form
are called "uredospores." The uredospores and teleutospores
are sometimes found in the same pustule.

It was once supposed that these two kinds of gonidia belonged
to different plants, but now it is known that the one-celled
form, the uredospores, is a form developed
earlier in the season than the teleutospores.
292. Cluster-cup form on the barberry.
— On the barberry is found still another
form of the wheat rust, the ' ' cluster cup ' '
stage. The pustules on the under side of
the barberry leaf are cup-shaped, the cups
being partly sunk in the tissue of the leaf,
while the rim is more or less curved back-
ward against
the leaf, and
split at several
places. These
cups occur in
clusters on the
affected spots
of the barberry
leaf as shown
154-

Fig. 154-
Single spot
showing cluster
cups enlarged.

Fig. 155-

Two cluster in fig.
cups more en-
larged, showing Within the

Fig. 153-

Barberry leaf with two
diseased spots, natural
size.

split margin.

Figs. 153-155.— Cluster-cup stage of wheat rust. CUpS numbers

of one-celled gonidia (orange in color, called aecidiospores) are
borne in chains from short branches of the mycelium, which
• fill the base of the cup, In fact the wall of the cup (peridium)

132

MO KP HO LOG Y.

is formed of similar rows of cells, which, instead of separating
into gonidia, remain united to form a wall. These cups are
usually borne on the under side of the leaf.

293. Spermagonia. — Upon the upper side of the leaves in the same spot
occur small, orange-colored pustules which are flask-shaped. They bear
inside, minute, rod-like bodies on the ends of slender threads, which ooze

Fig. 156.
Section of an secidium (cluster cup; from barberry leaf". (After Marshall-Ward.)

out on the surface of the leaf. These flask-shaped pustules are called
spermagonia, and the minute bodies within them sperniatia, since they were
once supposed to be the male element of the fungus. Their function is not
known. They appear in the spots at an earlier time than the cluster cups.

293a. How the cluster-cup stage was found to be a part of the wheat rust.
— The cluster-cup stage of the wheat rust was once supposed also to be a dif-
ferent plant, and the genus was called acidium. The occurrence of wheat
rust in great abundance on the leeward side of affected barberry bushes in
England suggested to the farmers that wheat rust was caused by barberry
rust. It was later found that the secidiospores of the barberry, when sown
on wheat, germinate and the thread of mycelium enters the tissues of the
wheat, forming mycelrum between the cells. This mycelium then bears
the uredospores, and later the teleutospores.

FUNGI: RUSTS.

'33

294. Uredospores can produce successive crops of uredospores. — Tiie uredo-
spores are carried by the wind to other wheat or grass plants, germinate,

Fig. i57.

Section through leaf of barberry at point affected with the cluster-cup stage of the wheat
rust; spermagonia above, aicidia below. (After Marshall-Ward.)

form mycelium in the tissues, and later the pustules with a second crop of
uredospores. Several successive crops of uredospores may be developed in

B

Fig. 158.

A , section through sorus of black rust of wheat, showing teleutospores. /?, mycelium
bearing both teleutospores and uredospores. (After de Bary.)

one season, so this is the form in which the fungus is greatly multiplied and
widely distributed.

134

MORPHOLOG Y.

295. Teleutcspores the last stage of the fungus in the season. — The teleu-
tospores are developed late in the season, or late in the development of the

host plant (in this case the
wheat is the host). They
then rest during the winter.
In the spring under favor-
able conditions each cell of
the teleutospore germi-
nates, producing a short
mycelium called a promy-
celium, as shown in figs.
161, 162. This promy-
celium is usually divided
into four cells. From each
cell
cess

' ' sterigma. " Through this
the protoplasm moves and
forms a small gonidium on

wheat rust. "(After Marshall- leaf through a sternal the end, sometimes called

Ward-) a sporidium.

296. How the fungus gets from the wheat back to the barberry. — If these
sporidia from the teleutospores are carried by the wind so that they lodge on

a short, pointed pro-
is formed called a

Fig. 159

Germinating uredospore of
(After Marshall-

Germ tube entering the
leaf through a stoma.

. 101. Fig. 162. Fig. 163.

Teleutospore germi- Promycelium of ger- Germinating sporidia entering leaf
nating, forming promy- minating teleutospore, of barberry by mycelium,
celium. forming sporidia.

Figs. 161-163. — Puccinia graminis (wheat rust). (After Marshall-Ward.)

FUNGI: RUSTS. 135

the leaves of the barberry, they germinate and produce the cluster cup again.
The plant has thus a very complex life history. Because of the presence of
several different forms in the life cyle, it is called a polymorphic fungus.

The presence of the barberry does not seem necessary in all cases for the
development of the fungus from one year to another.

297. Synopsis of life history of wheat rust.

Cluster -cup stage on leaf of barberry.

Mycelium between cells of leaf in affected spots.
Spermagonia (sing, spermagonium), small flask-shnped bodies

sunk in upper side of leaf; contain " spermatia."
yEcidia (sing, aecidium), cup-shaped bodies in under side of

leaf.
Wall or peridium, made up of outer layer of fungus threads

which are divided into short cells but remain united.
At maturity bursts through epidermis of leaf; margin of
cup curves outward and downward toward surface of leaf.
Central threads of the bundle are closely packed, but free.
Threads divide into short angular cells which separate
and become aecidiospores, with orange-colored content.
^Ecidiospores carried by the wind to wheat, oats, grasses,
etc. Here they germinate, mycelium enters at stomate,
and forms mycelium between cells of the host.

Uredo stage (red rust) on wheat, oats, grasses, etc.
Mycelium between cells of host.
Bears uredospores (i -celled) in masses under epidermis, which

is later ruptured and uredospores set free.
Uredospores carried by wind to other individual hosts, and

new crops of uredospores formed.

Teleutospore stage (black rust], also on wheat, etc.

Mycelium between cells of host.

Bears teleutospores (2 -celled) in masses (sori) under epidermis,
which is later ruptured.

Teleutospores rest during winter. In spring each cell germi-
nates and produces a promycelimn, a short thread, divided
into four cells.

1 36 MORPHOLOG Y.

Promycelium bears four sterigmata and four gonidia (or spo-
ridia), which in favorable conditions pass back to the bar-
berry, germinate, the tube enters between cells into the
intercellular spaces of the host to produce the cluster cup
again, and thus the life cycle is completed.

298. Higher fungi divided into two series. — Of the higher fungi there
are two large series. One of these is represented by the mushrooms, a good
example of which is the common mushroom (Agaricus campestris).
(For the study of the mushrooms see Part III, Ecology.)
The large group of fungi to which the mushroom belongs is called the
basidiomycetes because in all of them a structure resembling a club, or basid-
ium, is present, and bears a limited number of spores, usually four, though
in some genera the number is variable. Some place the rusts (uredineae) in
the same series (basidium series) because of the short promycelium, and
four sporidia developed from each cell of the teleutospore.

Sac Fungi.

299. The other large series of the higher fungi may be rep-
resented by what are popularly called the "powdery mildews."
Fig. 164 is from a photograph of two willow leaves affected by
one of these mildews. The leaves are first partly covered with a
whitish growth of mycelium, and numerous chains of colorless
gonidia are borne on short erect threads. The masses of gonidia
give the leaf a powdery appearance. The mycelium lives on the
outer surface of the leaf, but sends short haustoria into the epi-
dermal cells.

300. Fruit bodies of the willow mildew. — On this same
mycelium there appear later numerous black specks scattered
over the affected places of the leaf. These are the fruit bodies
(perithecia). If we scrape some of these from the leaf, and
mount them in water for microscopic examination, we shall be
able to see their structure. Examining these first with a low
power of the microscope, each one is seen to be a rounded body,
from which radiate numerous filaments, the appendages. Each
one of these appendages is coiled at the end into the form of a
little hook. Because of these hooked appendages this genus is
called uncinula. This rounded body is the perilhecium.

FUNGI: SAC FUNGI.

137

301. Asci and ascospores. — While we are looking at a few of
these through the microscope with the low power, we should

Fig. 164.

Leaves of willow showing willow mildew. The black dots are the fruit bodies (perithecia)
seated on the white mycelium.

press on the cover glass with a needle until we see a few of the
perithecia rupture. If this is done carefully we will see several
small ovate sacs issue, each containing a number of spores, as
shown in fig. 166. Such a sac is an ascus, and the spores are

ascospores*

138

MORPHOLOG F.

302. The sac fungi or ascomycetes. — The large group of fungi to which
this uncinula belongs is known as the sac fungi, or ascomycetes. While

Fig. 165.

Willow mildew; bit
of mycelium with
erect conidiophores,

Fig- '66. Fig. 167.

Fruit of willow mildew, showing hooked ap- Fruit body of an-

pendages. Genus uncinula. other mildew with

Figs. 166, 167.— Perithecia (perithecium) of dichotomousappen-

bearing chain of two powdery mildews, showing escape of asci dages. Genus

gonidia ; gonidium at containing the spores from the crushed fruit microsphasra.
left germinating. bodies.

many of the powdery mildews have a variable number of spores in an ascus,
a large majority of the ascomycetes have just 8 spores in an ascus, while

Fig. 168. Fig. 169.

Contactofan- Disappear-

theridium and ance of contact

carpogonium walls of anthe-

(carpogonium ridium and rig. 170.

the larger cell); carpogonium, Fertilized egg surrounded by

the beginning and fusion of the enveloping threads which

of fertilization. the two nuclei. grow up around it.
Figs. 168-170.— Fertilization in sphaerotheca ; one of the powdery mildews. (After Harper.)

some have 4, others 16, and some an indefinite number. The complex struc-
ture of the fruit body, as well as the usually definite and limited number of

FUNGI : CLA SSI PICA TION.

spores in an ascus, places these fungi on a higher scale than the mucors,
saprolegnias, and their relatives, where the number of gonidia in a sporangium
is always indefinite.

303. Leaf curl of the peach, black knot of the plum and cherry, ergot of
the rye and grasses, and many other fungi are members of the ascomycetes.
The majority of the lichens are ascomycetes, while a few are basidiomycetes.

304. Classification of the fungi. — Those who believe that the fungi repre-
sent a natural group of plants arrange them in three large series related to
each other somewhat as follows:

The Gonidium Type or Series. The
number of gonidia in the sporangium
is indefinite and variable. It may be
very large or very small, or even only -i
one in a sporangium. To this serie
belong the lower fungi; ex., mucor
saprolegnia, peronospora, etc.

The Basidium Type or Series.
The number of gonidia on a basi-
dium is limited. and definite, and
the basidium is a characteristic
structure; ex. uredineae (rusts),
mushrooms, etc.

The Ascus Type or Series. The
number of spores in an ascus is
limited and definite, and the ascus
is a characteristic structure; ex.
leaf curl of peach (exoascus), pow-
dery mildews, black knot of plum,
black rot of grapes, etc.

305. Others believe that the fungi do not represent a natural group, but
that they have developed off from different groups of the algae by becoming
parasitic. As parasites they no longer needed chlorophyll, and consequently
lost it. They thus derive their carbohydrates from organic material manu-
factured by the green plants.

According to this view the lower fungi have developed off from the lower
algae (saprolegnias, mucors, peronosporas, etc., being developed off from
siphonaceous algae like vaucheria), and the higher fungi being developed off
from the higher algae (the ascomycetes perhaps from the rhodophyceae).

CHAPTER XXII.

LIVERWORTS (HEPATIC/E).

306. We come now to the study of representatives of another
group of plants, a few of which we examined in studying the organs
of assimilation and nutrition. I refer to what are called the liver-
worts. Two of these liverworts belonging to the genus riccia
are illustrated in figs. 58, 171.

Riccia.

307. Form of the floating riccia (R. fluitans).— The gen-
eral form of floating riccia is that of a narrow, irregular, flattened,
ribbon-like object, which forks repeatedly, in a dichotomous
manner, so that there are several lobes to a single plant. It
receives its name from the fact that at certain seasons of the year
it may be found floating on the water of pools or lakes. When
the water lowers it comes to rest on the damp soil, and rhizoids
are developed from the under side. Now the sexual organs, and
later the fruit capsule, are developed.

308. Form of the circular riccia (R. crystallina). — The
circular riccia is shown in fig. 171. The form of this one is quite
different from the floating one, but the manner of growth is much
the same. The branching is more compact and even, so that a cir-
cular plant is the result. This riccia inhabits muddy banks,
lying flat on the wet surface, and deriving its soluble food by
means of the little rootlets (rhizoids) which grow out from the
under surface.

Here and there on the margin are narrow slits, which extend

140

LIVER WOR TS : RICCIA.

141

Fig. 171.
Thallus of Riccia crystallina.

nearly to the central point. They are not real slits, however, for
they were formed there as the plant grew. Each one of these
V-shaped portions of the thal-
lus is a lobe, and they were
formed in the young condition
of the plant by a branching
in a forked manner. Since
giowth took place in all direc-
tions radially the plant be-
came circular in form. These
large lobes we can see are
forked once or twice again,
as shown by the seeming
shorter slits in the margin.

309. Sexual organs. — In

order to study the sexual organs we must make thin sections
through one of these lobes lengthwise and perpendicular to the
thallus surface. These sections are mounted for examination
with the microscope.

310. Archegonia. — We are apt to find the organs in various stages of de-
velopment, but we will select one of the flask-shaped structures shown in fig.
172 for study. This flask-shaped body we see is entirely sunk in the tissue
of the thallus. This structure is the female organ, and is what we term in
these plants the archegonium. It is more complicated in structure than the
oogonium. The lower portion is enlarged and bellied out, and is the venter
of the archegonium, while the narrow portion is the neck. We here see it in
section. The wall is one cell layer in thickness. In the neck is a canal,
and in the base of the venter we see a large rounded cell with a distinct
and large nucleus. This cell is the egg cell.

311. Antheridia. — The antheridia are also borne in cavities sunk in the
tissue of the thallus. There is here no illustration of the antheridium of this
riccia, but fig. 178 represents an antheridium of another liverwort, and there
is not a great difference between the two kinds. Each one of those little rect-
angular sperm mother cells in the antheridium changes into a swiftly moving
body like a little club with two long lashes attached to the smaller end By
the violent lashing of these organs the spermatozoid is moved through the water,
or moisture which is on the surface of the thallus. It moves through the canal
of the archegonium neck and into the egg, where it fuses with the nucleus of
the egg, and thus fertilization is effected.

142

MORPHOLOG Y.

312. Embryo. — In the plants which we have selected thus far for study,
the egg, immediately after fecundation, we recollect, passed into a resting
state, and was enclosed by a thick protecting wall. But in riccia, and in the
other plants of the group which we are now studying, this is not the case.

Fig. 172.

Arche^onium of riccia, showing neck,
venter, and the egg; archegonium is partly
surrounded by the tissue of the thallus.
(Riccia crystallina.)

Fig. 173-

Young embryo (sporogoni-
um) of riccia, within the venter
of the archegonium ; the latter
has now two layers of cells.
(Riccia crystallina.)

The egg, on the other hand, after acquiring a thin wall, swells up and fills
the cavity of the venter. Then it divides by a cross wall into two cells.
These two grow, and divide again, and so on until there is formed a quite
large mass of cells rounded in form and still contained in the venter of the
archegonium, which itself increases in size by the growth of the cells of the
wall.

313. Sporogonium of riccia. — The fruit of riccia, which is
developed from the fertilized egg in the archegonium, forms a
rounded capsule still enclosed in the venter of the archegonium,
which grows also to provide space for it. Therefore a section
through the plant at this time, as described for the study
of the archegonium, should show this capsule. The capsule
then is a rounded mass of cells developed from the egg. A sin-
gle outer layer of cells forms the wall, and therefore is sterile. ,

LIVER WOK TS : RtCCTA .

'43

All the inner cells, which are richer in protoplasm, divide into
four cells each. Each of these cells becomes a spore with a thick
wall, and is shaped like a triangular pyramid whose sides are of
the same extent as the base (tetrahedral). These cells formed in

B

Fig. 174.

Nearly mature sporogonium of Riccia crystallina ;
mature spore at the right.

Fig. 175-

Riccia glauca ; archegonium
containing nearly mature spo-
rogonium. s&, spore-producing
cells surrounded by single layer
of sterile cells, the wall of the
sporogonium.

fours are the spores. At this time the wall of the spore-case dis-
solves, the spores separate from each other and fill the now en-
larged venter of the archegonium. When the thallus dies they
are liberated, or escape between the loosely arranged cells of
the upper surface.

314. A new phase in plant life. — Thus we have here in the
sporogonium of riccia a very interesting phase of plant life, in
which the egg, after fertilization, instead of developing directly
into the same phase of the plant on which it was formed,
grows into a quite new phase, the sole function of which is the
development of spores. Since the form of the plant on which the
sexual organs are developed is called the gametophyte, this new
phase in which the spores are developed is termed the sporo-
phyte.

Now the spores, when they germinate, develop the gameto-
phyte, or thallus, again. So we have this very interesting condi-

144 MORPHOLOGY.

tion of things, the thalltis (gametophyte) bears the sexual organs
and the unfertilized egg. The fertilized egg, starting as it does
from a single-celled stage, develops the sporogonium (sporo-
phyte). Here the single-cell stage is again reached in the spore,
which now develops the thallus.

315. Riccia compared with coleochaete, cedogonium, etc. — We have said
that in the sporogonium of riccia we have formed a new phase in plant life.
If we recur to our study of coleochaete we may see that there is here possibly
a state of things which presages, as we say, this new phase which is so well
formed in riccia. We recollect that after the fertilized egg passed the period
of rest it formed a small rounded mass of cells, each of which now forms a
zoospore. The zoospore in turn develops the normal thallus (gametophyte)
of the coleochaete again. In coleochaete then we have two phases of the
plant, each having its origin in a one-celled stage. Then if we go back to
cedogonium, we will remember that the fertilized egg, before it developed
into the cedogonium plant again (which is the gametophyte), at first divides
into four cells which become zoospores. These then develop the cedogonium
plant.

Note. Too much importance should not be attached to this seeming ho-
mology of the sporophyte of cedogonium, coleochaete, and ricciay for the nu-
clear phenomena in the formation of the zoospores of oedogonium/and coleo-
chaete are not known. They form, however, a very suggestive series.

Marchantia.

316. The marchantia (M. polymorpha) has been chosen for
study because it is such a common and easily obtained plant, and
also for the reason that with comparative ease all stages of
development can be obtained. It illustrates also very well cer-
tain features of the structure of the liverworts.

The plants are of two kinds, male and female. The two dif-
ferent organs, then, are developed on different plants. In
appearance, however, before the beginning of the structures
which bear the sexual organs they are practically the same. The
thallus is flattened like nearly all of the thalloid forms, and
branches in a forked manner. The color is dark green, and
through the middle line of the thallus the texture is different
from that of the margins, so that it possesses what we term a

LIVER WOK TS : MA KCHA N TIA .

midrib, as shown in figs. 176, 180. The growing point of the
thallus is situated in the little depression at the free end. If we
examine the upper surface with a hand
lens we see diamond-shaped areas, and
at the center of each of these areas are
the openings known as the stomates.

317. Antheridial plants. — One of
the male plants is figured at 176. It
bears curious structures,
each held aloft by a short
stalk. These are the an-
theridial recep-
tacles (or male
gametophores).
Each one is cir-
cular, thick, and
shaped some- Fig. 176.

what like a bi- Male plant of marchantia bearing antheridiophores.

convex lens. The upper surface is marked by radiating fur-
rows, and the margin is crenate. Then we note, on careful
examination of the upper surface, that there are numerous minute
openings. If we make a thin section of this structure perpen-

Fig. 177-

Section of antheridial receptacle from male plant of Marchantia polymorpha, showing
cavities where the antheridia are borne.

dicular to its surface we shall be able to unravel the mystery of
its interior. Here we see, as shown in fig. 177, that each one
of these little openings on the surface is an entrance to quite

146

MORPHOLOG Y.

a large cavity. Within each cavity there is an oval or ellip-
tical body, supported from the base of the cavity on a short
stalk. This is an antheridium, and one of them is shown still
more enlarged in fig. 178. This shows the structure of the
antheridium, and that there are within several angular areas,
which are divided by numerous straight cross-lines into countless
tiny cuboidal cells, the sperm mother cells. Each of these, as
stated in the former chapter, changes into a swiftly moving body
resembling a serpent with two long lashes attached to its tail.

318. The way in which one of these sperm mother cells changes into this
spermatozoid is very curious. We first note that a coiled spiral body is appear-

Fig. 178.

Section of antheridium of mar-
chantia, showing the groups of
sperm mother cells.

Fig. 179.

Spermatozoids of marchantia,
uncoiling and one extended, show-
ing the two cilia.

ing within the thin wall of the cell, one end of the coil larger than the other.
The other end terminates in a slender hair-like outgrowth with a delicate vesi-
cle attached to its free end. This vesicle becomes more and more extended
until it finally breaks and forms two long lashes which are clubbed at their
free ends as shown in fig. 179.

319. Archegonial plants. — In fig. 180 we see one of the
female plants of marchantia. Upon this there are also very
curious structures, which remind one of miniature umbrellas.
The general plan of the archegonial receptacle (or female

LIVERWORTS: MARCHANTIA. \tf

gametophore), for this is what these structures are, is similar to
that of the antheridial receptacle, but the rays are more pro-
nounced, and the details of structure are quite different, as we
shall see. Underneath the arms there hang down delicate
fringed curtains. If we make sections of this in the same direc-

Fig. 180.
Marchantia polymorpha, female plants bearing archegoniophores.

tion as we did of the antheridial receptacle, we will be able to
find what is secreted behind these curtains. Such a section is
figured at 184. Here we find the archegonia, but instead of
being sunk in cavities their bases are attached to the under

H MORPHOLOG Y.

surface, while the delicate, pendulous fringes afford them pro-
tection from drying. An archegonium we see is not essentially
different in marchantia from what it is in riccia, and it will be
interesting to learn whether the sporogonium is essentially dif-
ferent from what we find in riccia.

CHAPTER XXIII.

LIVERWORTS CONTINUED.

320. Sporogonium of marchantia. — If we examine the plant
shown in fig. 181 we will see oval bodies which stand out be-

Fig. 181.

Archegonial receptacles of marchantia bearing ripe sporogonia The
capsule of the sporogonium projects outside, while the stalk is attached to
the receptacle underneath the curtain. In the left figure two of the
capsules have burst and the elaters and spores are escaping.

tween the rays of the female Receptacle, supported
on short stalks. These are the sporogonia, or
spore-cases. We judge at once that they are quite
different from those which we have studied in
riccia, since those were not stalked. We can see
that some of the spore-cases have opened, the wall
splitting down from the apex in several lines. This
is caused by the drying of the wall. These tooth-
like divisions of the wall now curl backward, and
we can see the yellowish mass of the spores in slow motion,

149

150

MORPHOLOG Y.

falling here and there. It appears also as if there were twisting
threads which aided the spores in becoming freed from the
capsule.

Fig. 182.

Section of archegpnial receptacle of Marcliantia polymorpha; ripe
sporogonia One is open, scattering spores and elaters; two are
still enclosed in the wall of the archegonium. The junction of the
stalk of the sporogonium with the receptacle is the point of attach-
ment of the sporophyte of marchantia with the gametophyte.

321. Spores and elaters. — If we take a bit
of this mass of spores and mount it in water
for examination with the microscope, we will
see that, besides the spores, there are very
peculiar thread-like bodies,

the markings of which remind
one of a twisted rope. These
are very long cells from the
inner part of the spore-case,
and their walls
are marked by spi-
ral thickenings.
This causes them
in drying,and also
when they absorb

1 . Fig. 183.

moisture, tO tWISt Elater and spore of marchantia. sp, spore ; we, mother-cell of
, , , , spores, showing partly formed spores.

and curl in all*

sorts of ways. They thus aid in pushing the spores out of the

capsule as it is drying.

322. Sporophyte of marchantia compared with riccia. —

We must recollect that the sporogonium in marchantia is larger
than in riccia, and that it is also not lying in the tissue of the
thallus, but is only attached to it at one side by a slender stalk,

LIVERWORTS: MARCHANTIA. !$!

This shows us an increase in the size and complex structure of
this new phase of the plant, the sporophyte. This is one of the
very interesting things which we have to note as we go on in the
study of the higher plants.

Fig. 184.

Marchantia pplymorpha, archegonium at the left with egg : archegonium at the right with
young sporogonium ; /, curtain which hangs down around the archegonia ; e, egg ; v, venter
of archegonium ; «, neck of archegonium ; sj>, young sporogonium.

323. Sporophyte dependent on the gametophyte for its nutri-
ment.— We thus see that at no time during the development of the
sporogonium is it independent from the gametophyte. This new
phase of plants then, the sporophyte, has not yet become an in-
dependent plant, but must rely on the earlier phase for sustenance.

324. Development of the sporogonium. — It will be interesting to note
briefly how the development of the marchantia sporogonium differs from that
of riccia. The first division of the fertilized egg is the same as in riccia, that
is a wall which runs crosswise of the axis of the archegonium divides it
into two cells. In marchantia the cell' at the base develops the stalk, so
that here there is a radical difference. The outer cell forms the capsule.
But here after the wall is formed the inner tissue does not all go to make
spores, as is the case with riccia. But some of it forms the elaters. While
in riccia only the outside layer of cells of the sporogonium remained sterile,
in marchantia the basal half of the egg remains completely sterile and

152

MORPHOLOG F.

develops the stalk, ana in the outer half the part which is formed from some
of the inner tissue is also sterile.

Fig. 185.

Section of developing sporogonia of marchantia ; nt, nutritive tissue of gametophyte ; sf,
sterile tissue of sporophyte ; sjf>, fertile part of sporophyte ; va, enlarged venter of arche-
gonium.

325. Embryo. — In the development of the embryo we can see all the way
through this division line between the basal half, which is completely sterile,
and the outer half, which is the fertile part. In fig. 185 we see a young
embryo, and it is nearly circular in section although it is composed of
numerous cells. The basal half is attached to the base of the inner surface
of the archegonium, and at this time the archegonium still surrounds it. The
archegonium continues to grow then as the embryo grows, and we can see
the remains of the shrivelled neck. The portion of the embryo attached to
the base of the archegonium is the sterile part and is called the " foot," and
later develops the stalk. The sporogonium during all the stages of its
development derives its nourishment from the gametophyte at this point of

LIVER WOR TS : MARCHANTIA.

153

attachment at the base of the archegonium. Soon, as shown in fig. 185 at
the right, the outer portion of the sporogonium begins to differentiate into
the cells which form the elaters and those which form spores. These lie in
radiating lines side by side, and form what is termed the archesporium. Each
fertile cell forms four spores just as in riccia. They are thus called the
mother cells of the spores, or spore mother cells.

326. How marchantia multiplies. — New plants of marchantia are formed
by the germination of the spores, and growth of the same to the thallus.
The plants may also be multiplied by parts of the old ones breaking away
by the action of strong currents of water, and when they lodge in suitable
places grow into well-formed plants. As the thallus lives from year to year
and continues to grow and branch the older portions die off, and thus sepa-
rate plants may be formed from a former single one.

327. Buds, or gemmae, of marchantia. — But there is another way in which
marchantia multiplies itself. If we examine the upper surface of such a

Fig. 186.
Marchantia plant with cupules and gemmae ; rhizoids below.

plant as that shown in fig. 186, we will see that there are minute cup-
shaped or saucer-shaped vessels, and within them minute green bodies.
If we examine a few of these minute bodies with the microscope we will see
that they are flattened, biconvex, and at two opposite points on the margin
there is an indentation similar to that which appears at the growing end of
the old marchantia thallus. These are the growing points of these little
buds. When they free themselves from the cups they come to lie on one

154

MORPHOLOG Y.

side. It does not matter on what side they lie, for whichever side it is, that
will develop into the lower side of the thallus, and forms rhizoids, while the
upper surface will develop the stomates.

Leafy-stemmed liverworts.

328. We should now examine more carefully than we have
done formerly a few of the leafy-stemmed liverworts (called
foliose liverworts).

329. Frullania (Fig. 60). — This plant grows on the bark of
logs, as well as on the bark of standing trees. It lives in quite

dry situations.
If we examine
the leaves we
will see how it is
able to do this.
We note that
there are two
rows of lateral
leaves, which
are very close
together, so
close in fact that
they overlap
like the shingles
on a roof.
Then, as the

B, through the marginal portion ; /, colorless layer ; chl, chlorophyll Creeping Stems

layer; s/>, stomate ; h, rhizoids; b, leaf-like outgrowths on under

side (Goebel). lie very close to

the bark of the tree, these overlapping leaves, which also
hug close to the stem and bark, serve to retain moisture
which trickles down the bark during rains. If we examine
these leaves from the under side as shown in fig. 62, we see
that the lower or basal part of each one is produced into a
peculiar lobe which is more or less cup-shaped. This catches
water and holds it during dry weather, and it also holds moisture
which the plant absorbs during the night and in damp days.

Fig. 187.
Section of thallus of marchantia. A, through the middle portion ;

FOLIO SE LIVERWORTS.

155

There is so much moisture in these little pockets of the under
side of the leaf that minute animals have found them good places
to live in, and one frequently discovers them in this retreat.
There is here also a third row of poorly developed leaves on the
under side of the stem.

330. Porella. — Growing in similar situations is the plant known as
porella. Sometimes there are a few plants

in a group, and at other times large mats
occur on the bark of a trunk. This plant,
porella, also has closely overlapping leaves
in rows on opposite sides of the stem, and
the lower margin of each leaf is curved
under somewhat as
in frullania, though
the pocket is not so
well formed.

The larger plants
are female, that is
they bear archego-
nia, while the male
plants, those whLh
bear antheridia, are
smaller and the an-
theridia are borne
on small lateral
branches. The an-
theridia are borne
in the axils of the
leaves. Others of
the leafy-stemmed
liverworts live in
damp situations.
Some of these, as
Cephalozia, grow on damp rotten logs. Cephalozia is much more delicate,
and the leaves are farther apart. It could not live in such dry situations
where the frullania is sometimes found. If possible the two plants should be
compared in order to see the adaptation in the structure and form to their
environment.

331. Sporogonium of a foliose liverwort. — The sporogonium
of the leafy-stemmed liverworts is well represented by that of
several genera. We may take for this study the one illustrated

Fig. 188.

Thallus of a thalloid liverwort (blasia) showing lobed
margin of the frond, intermediate between thalloid and
foliose plant.

156

MO RP HO LOG Y.

in fig. 192, but another will serve the purpose just as well. We
note here that it consists of a rounded capsule borne aloft on a
long stalk, the stalk being much longer proportionately than in
marchantia. At maturity the capsule splits down into four

Fig. 190.

Antheridium of a foliose liverwort ( jun-
germannia).

Foliose liverwort, male plant showing anthe-
ridia in axils of the leaves (a jungermannia).

Fig. 191.

Foliose liverwort, female plant with
rhizoids.

quadrants, the wall forming four valves, which spread apart from
the unequal drying of the cells, so that the spores are set free, as
shown in fig. 194. Some of the cells inside of the capsule de-
velop elaters here also as well as spores. These are illustrated
in fig. 196.

332, In this plant we see that the sporophyte remains attached

FOLtOSZ

to the gametophyte, and thus is dependent on it for sustenance.
This is true of all the plants of this
group. The sporophyte never becomes
capable of an independent existence,
and yet we see that it is becoming
larger and more highly differentiated
than in the simple riccia.

Fig. 193- .

Opening capsule
showing escape of
spores and elaters.

Fig. 194.

Capsule parted down
to the stalk.

Fig. 192.

Fruiting plant of a foliose liver-
wort (jungermannia). Leafy part
is the gametophyte ; stalk and cap- Four spores from Elaters, at left showing the two
sule is the sporophyte (sporogonium mother cell held in spiral marks, at right a branched
in the bryophytes). a group. elater.

Figs. 193-196. — Sporogonium of liverwort (jungermannia) opening by splitting into four
parts, showing details of elaters and spores.

CHAPTER XXIV.

MOSSES (MUSCI).

333. We are now ready to take up the more careful study of
the moss plant. There are a great many kinds of mosses, and
they differ greatly from each other in the finer details of struc-
ture. Yet there are certain general resemblances which make it
convenient to take for study almost any one of the common
species in a neighborhood, which forms abundant fruit. Some,
however, are more suited to a first study than others. (Polytri-
chium and funaria are good mosses to study.)

334. Mnium. — We will select here the plant shown in fig. 197 .
This is known as a mnium (M. afrine), and one or another of the
species of mnium can be obtained without much difficulty.
The mosses, as we have already learned, possess an axis
(stem) and leaf-like expansions, so that they are leafy-stemmed
plants also. Certain of the branches of the mnium stand upright,
or nearly so, and the leaves are all of the same size at any given
point on the stem, as seen in the figure. There are three rows
of these leaves, and this is true of most of the mosses.

335. The mnium plants usually form quite extensive and pretty
mats of green in shady moist woods or ravines. Here and there
among the erect stems are prostrate ones, with two rows of promi-
nent leaves so arranged that it reminds one of some of the leafy-
stemmed liverworts. If we examine some of the leaves of the
mnium we will see that the greater part of the leaf consists of a
single layer of green cells, just as is the case in the leafy-stemmed
liverworts. But along the middle line is a thicker layer, so that
it forms a distinct midrib. This is characteristic of the leaves

158

MOSSES.

159

of mosses, and is one way in which they are separated from the
leafy-stemmed liverworts, the latter never having a midrib.

336. The fruiting moss plant. — In fig. 197 is amoss plant "in
fruit," as we say. Above the leafy stem a slender stalk bears

the capsule, ancl in this capsule are borne
the spores. The capsule then belongs to
the sporophyte phase of the moss plant, and
we should inquire whether the entire plant
as we see it here is the sporophyte, or
whether part of it is gametophyte. If
a part of it is gametophyte and a part
sporophyte, then where does the one end
and the other begin ? If we strip off the
leaves at the end of the leafy stem, and
make a longisection in the middle line, we
should find that the stalk which bears the
capsule is simply stuck into the end of the

Fig. 197.

Portion of moss plant of Mnium affine, showing two
sporogonia from one branch. Capsule at left has just shed
the cap or operculum ; capsule at right is shedding spores,
and the teeth are bristling at the mouth. Next to the right
is a young capsule with calyptra still attached ; next are
two spores enlarged.

leafy stem, and is not organically connected with it. This is
the dividing line, then, between the gametophyte and the sporo-
phyte. We shall find that here the archegonium containing

i6o

MORPtfOLOG Y.

the egg is borne, which is a surer way of determining the limits
of the two phases of the plant.

337. The male and female moss plants. — The two plants of mnium shown in
figs. 198, 199 are quite different, as one can easily see, and yet they belong
to the same species. One is a female plant, while the other is a male plant.

The sexual organs then in mnium, as
in many others of the mosses, are borne
on separate plants. The archegonia
are borne at the end of the stem, and are
protected by somewhat narrower leaves
which closely overlap and are wrapped
together. They are similar to the
archegonia of the liverworts.

Fig. 198.

Female plant (gametophyte) of a moss
(mnium), showing rhizoids below, and the
tuft of leaves above which protect the arche-
gonia.

Fig. 199.

Male plant (gametophyte) of a moss
(mnium) showing rhizoids below and the
antheridia at the center above surrounded by
the rosette of leaves.

The male plants of mnium are easily selected, since the leaves at the end
of the stem form a broad rosette with the antheridia, and some sterile threads
packed closely together in the center. The ends of the mass of antheridia
can be seen with the naked eye, as shown in fig. 199. When the antheridia

161

are ripe, if we make a section through a cluster, or if we merely tease out
some from the end with a needle in a drop of water on the slide, then prepare
for examination with the microscope, we will see the form of the antheridia.
They are somewhat clavate or elliptical in outline, as seen in fig. 201. Be-
tween them there stand short threads composed of several cells containing
chlorophyll grains. These are sterile threads (paraphyses).

338. Sporogonium. — In fig. 197 we see illustrated a sporogonium of mnium,
which is of course developed from the fertilized egg cell of the archegonium.
There is a nearly cylindrical capsule, bent downward, and supported on a long

Fig. 201.

Fig. 200. Antheridium of mnium

Section through end of stem of female plant of mnium, show- with jointed paraphysis
ing archegonia at the center. One archegonium -shows the egg. at the left ; spermato-
On the sides are sections of the protecting leaves. zoids at the right.

slender stalk. Upon the capsule is a peculiar cap,* shaped like a ladle or
spatula. This is the remnant of the old archegonium, which, for a time sur-
rounded and protected the young embryo of the sporogonium, just as takes
place in the liverworts. In most of the mosses this old remnant of the arche-
gonium is borne .aloft on the capsule as a cap, while in the liverworts it is
thrown to one side as the sporogonium elongates.
339. Structure of the moss capsule. — At the free end on the moss capsule

* Called the calyptra.

1 62

MORPHOLOG Y.

as shown in the case of mnium in Fig. 197, after the remnant of the arche-
gonium falls away, there is seen a conical lid which fits closely over the end.
When the capsule is ripe this lid easily falls away, and can be brushed off
so that it is necessary to handle the plants with care if it is
desired to preserve this for study.

340. When the lid is brushed away as the capsule dries
more we see that the end of the capsule covered by the lid
appears " frazzled." If we examine this end with the micro-
scope we will see that the tissue of the capsule here is torn
with great regularity, so that there are two rows of narrow,
sharp teeth which project outward in a ring around the
opening. If we blow our "breath" upon these teeth they
will be seen to move, and as the
moisture disappears and reappears
in the teeth, they close and open
the mouth of the capsule, so sensi-
tive are they to the changes in the
humidity of the air. In this way
all of the spores are prevented to
some extent from escaping from
the capsule at one time.

341. Note. If we make a sec-
tion longitudinal of the capsule of
mriium, or some other moss, we find
that the tissue which develops the
spores is much more restricted
than in the capsule of the liver-
worts which we have studied. The
spore-bearing tissue is confined to
a single layer which extends around
the capsule some distance from the
Fig. 202. outside of the wall, so that a central

Two different stages of young sporogonium of cylinder is left of sterile tissue,
a moss, still within the archegonium and wedg- This is t]ie columella, and is pres-
ing their way into the tissue of the end of the stem. r

h, neck of archegonium ; /, young sporogonium. ent in nearly all the mosses. Each
This shows well the connection of the sporophyte _ . „ _ , - .. ,

with the gametophyte. of the cells of the fertile layer

divides into four spores.

342. Development or the sporogonium.— The egg cell after fertilization
divides by a wall crosswise to the axis of the archegonium. Each of these
cells continues to divide for a time, so that a cylinder pointed at both ends is
formed. The lower end of this cylinder of tissue wedges its way down
through the base of the archegonium into the tissue of the end of the moss
stem as. shown in fig. 202. This forms the foot through which the nutrient

MOSSES.

I63

materials are passed from the gametophyte to the sporogonium. The upper
part continues to grow, and finally the upper end differentiates into the mature
capsule.

343. Protonema of the moss. — When the spores of a moss germinate they
form a thread-like body, with chlorophyll. This thread becomes branched,
and sometimes quite extended tangles of these threads are formed. This is
called the protonema, thatisyfr.tf thread. The older threads become finally
brown, while the later ones are green. From this protonema at certain
points buds appear which divide by close oblique walls. From these buds
the leafy stem of the moss plant grows. Threads similar to these protonemal
threads now grow out from the leafy stem, to form the rhizoids. These
supply the moss plant with nutriment, and now the protonema usually dies,
though in some few species it persists for long periods.

164

MORPHOLOG Y.

CHAPTER XXV.

FERNS.

345. In taking up the study of the ferns we find plants which
are very beautiful objects of nature and thus have always attracted
the interest of those who love the beauties of nature. But they
are also very interesting to the student, because of certain re-
markable peculiarities of the structure of the fruit bodies, and
especially because of the intermediate position which they occupy
within the plant kingdom, representing in the two phases of
their development the primitive type of plant life on the one
hand, and on the other the modern type. We will begin our
study of the ferns by taking that form which is the more promi-
nent, the fern plant itself.

346. The Christmas fern. — One of the ferns which is very
common in the Northern States, and occurs in rocky banks and
woods, is the well-known Christmas fern (Aspidium acrostichoides)
shown in fig. 203. The leaves are the most prominent part of the
plant, as is the case with most if not all our native ferns. The
stem is very short and for the most part under the surface of the
ground, while the leaves arise very close together, and thus form
a rosette as they rise and gracefully bend outward. The leaf is
elongate and reminds one somewhat of a plume with the pinnae
extending in two rows on opposite sides of the midrib. These
pinnae alternate with one another, and at the base of each pinna
is a little spur which projects upward from the upper edge.
Such a leaf is said to be pinnate. While all the leaves have the
same general outline, we notice that certain ones, especially those
toward the center of the rosette, are much narrower from the

165

1 66

MORPHOLOG Y.

middle portion toward the end. This is because of the shorter
pinnae here.

347. Fruit "dots" (sorus, indusium). — If we examine the
under side of such short pinnae of the Christmas fern we see that
there are two rows of small circular dots, one row on either side of
the pinna. These are called the "fruit
dots," or sori (a single one is a sorus). If
we examine it with a low power of the mi-
croscope,
or with a
pocket
lens, we
will see that
there is a
c i r c u 1 a r
disk which
c o v e r s
more or
less com-
pletelyvery
minute objects, usual-
ly the ends of the
latter projecting just be-
yond the edge if they are
mature. This circular disk
is what is called the indu-
sium, and it is a special
outgrowth of the epidermis
of the leaf here for the
protection of the spore-
cases. These minute ob-
jects underneath are the
fruit bodies, which in the
case of the ferns and their allies are called sporangia. This
indusium in the case of the Christmas fern, and also in some
Others, is attached to the leaf by means of a short slender stalk

Fig. 203.
Christmas fern (Adiantum acrostichoides).

FEANS.

i67

which is fastened to the middle of the under side of this shield,

as seen in cross section in fig. 209.

348. Sporangia.— If we section through the leaf at one of the

fruit dots, or if we tease off some of the sporangia so that the

stalks are still attached, and
examine them with the mi-
croscope, we can see the
form and structure of these
peculiar bodies. Different
views of a sporangium are
shown in fig. 210. The
slender portion is the stalk,
and the larger part is the
spore-case proper. We
should examine the structure
of this spore-case quite care-
fully, since it will help us to
understand better than we
otherwise could the remark-
able operations which it
performs in scattering the
spores.

349. Structure of a spo-
rangium. — If we examine
one of the sporangia in side
view as shown in fig. 210,
Fig. 204. we note a prominent row of

Rhizome with bases of leaves, and roots of the cells which extend around
Christmas fern.

the margin of the dorsal

edge from near the attachment of the stalk to the upper front
angle. The cells are prominent because of the thick inner
walls, and the thick radial walls which are perpendicular to the
inner walls. The walls on the back of this row and on its
sides are very thin and membranous. We should make this
out carefully, for the structure of these cells is especially adapt-
ed to a special function which they perform. This row of cells

1 68 MORPHOL OGY,

is termed the annulus, which means a little ring. While this
is not a complete ring, in some other ferns the ring is nearly
complete.

350. In the front of the sporangium is another peculiar group

Fig. 205.
Rhizome of sensitive fern (Onoclea sensibilis).

of cells. Two of the longer ones resemble the lips of some crea-
ture, and since the sporangium opens between them they are
sometimes termed the lip cells. These lip cells are connected with
the upper end of the annulus on one
side and with the upper end of the stalk
on the other side by thin-walled cells,
which may be termed connective cells,
since they hold each lip cell to its part
of the opening sporangium. The cells
on. the side of the sporangium are also
thin -walled. If we now examine a
F. 2o6 sporangium from the back, or dorsal

Under side of pinna of Aspidium edge as we say, it will appear as in the

spinulosum showing fruit dots . - . , .,

(sori). left-hand figure. Here we can see

how very prominent the annulus is. It projects beyond the
surface of the other cells of the sporangium. The spores are
contained inside this case.

FEKNS.

169

351. Opening of the sporangium and dispersion of the
spores. — If we take some fresh fruiting leaves of the Christmas
fern, or of any one of many of the species of the true ferns just
at the ripening of the spores, and place a portion of it on apiece
of white paper in a dry room, in a very short time we will see
that the paper is being dusted with minute brown objects which
fly out from the leaf. Now if we take a portion of the same leaf
and place it under the low power of the microscope, so that the
full rounded sporangia can be seen, in a short time we will note
that the sporangium opens, the upper half curls backward as

Fig. 207.
Four pinnae of adiantum, showing recurved margins which cover the sporangia.

shown in fig. 211, and soon it snaps quickly, to near its former
position, and the spores are at the same time thrown for a consid-
erable distance. This movement can sometimes be seen with the
aid of a good hand lens.

352. How does this opening and snapping of the sporan-
gium take place ? — We are now more curious than ever to see
just how this opening and snapping of the sporangium takes place,
We should now mount some of the fresh sporangia in water and
cover with a cover glass for microscopic examination. A drop
of glycerine should be placed at one side of the cover glass on the
slip so that the edge of the glycerine will come in touch with the
water. Now as one looks through the microscope to watch the

MO RP HO LOG Y.

sporangia, the water should be drawn from under the cover glass
with the aid of some bibulous paper, like filter paper, placed at the

edge of the cover glass on
the opposite side from the
glycerine. As the glycer-
ine takes the place of the
water around the sporangia
it draws the water out of
the cells of the annulus,
just as it took the water
out of the cells of the
spirogyra as we learned
some time ago. As the
water is drawn out of these
cells there is produced a
pressure from without, the
atmospheric pressure upon
the glycerine. This causes
the walls of these cells of
the annulus to bend in-
ward, because, as we have
Fig 2o8 already learned, the glycer-

Section through sorus of Polypodium vulgare jne does not paSS through
showing different stages of sporangium, and one
multicellular capitate hair. the walls nearly SO fast

as the waiter comes out.

353. Now the structure of the cells of this annulus, as we
have seen, is such that the inner walls and the perpendicular

Fig. 209.
Section through sorus and shield-shaped indusium of aspidium.

walls are stout, and consequently they do not bend or collapse
when this pressure is brought to bear on the outside of the cells.

FEKNS. IJI

The tli in membranous walls on the back (dorsal walls) and on
the sides of the annulus, however, yield readily to the pressure
and bend inward. This, as we can readily see, pulls on the ends
of each of the perpendicular walls drawing them closer together.
This shortens the outer surface of the annulus and causes it to
first assume a nearly straight position, then curve backward until
it quite or nearly becomes doubled on itself. The sporangium

f »

Fig. 210.
Rear, side, and front views of fern sporangium. </, e, annulus; it, lip cells.

opens between the lip cells on the front and the lateral walls of
the sporangium are torn directly across. The greater mass of
spores are thus held in the upper end of the open sporangium,
and when the annulus has nearly doubled on itself it suddenly
snaps back again in position. While treating with the glycerine
we can see all this movement take place. Each cell of the
annulus acts independently, but often they all act in concert.
When they do not all act in concert, some of them snap sooner
than others, and this causes the annulus to snap in segments.

354. The movements of the sporangium can take place in
old and dried material. — If we have no fresh material to study

172

MORPHOLOGY.

the sporangium with, we can use dried material, for the move-
ments of the sporangia can be well seen in dried material, pro-
vided it was collected at about the time the sporangia are mature,
that is at maturity, or soon afterward. We take some of the
dry sporangia (or we may wash the glycerine off those which we
have just studied) and mount them in water, and quickly examine

Fig. 211.

Dispersion of spores from sporangium of Aspidium acrostichoides, showing different
stages in the opening and snapping of the annulus.

them with a microscope. We notice that in each cell of the
annulus there is a small sphere of some gas. The water which
bathes the walls of the annulus is absorbed by some substance
inside these cells. This we can see because of the fact that this
sphere of gas becomes smaller and smaller until it is only a mere

FEfiNS. 1 73

dot, when it disappears in a twinkling. The water has been taken
in under such pressure that it has absorbed all the gas, and the
farther pressure in most cases closes the partly opened sporangium
more completely.

355. Now we should add glycerine again and draw out the
water, watching the sporangia at the same time. We see that
the sporangia which have opened and snapped once will do it
again. And so they may be made to go through this operation
several times in succession. We should now note carefully the
annulus, that is after the sporangia have opened by the use of
glycerine. So soon as they have snapped in the glycerine we can
see those minute spheres of gas again, and since there was no air
on the outside of the sporangia, but only glycerine, this gas must,
it is reasoned, have been given up by the water before it was all
drawn out of the cells.

356. The common polypody. — We may now take up a few other ferns for
study. Another common fern is the polypody, one or more species of which
have a very wide distribution. The stem of this fern is also not usually seen,
but is covered with the leaves, except in the case of those species which grow
on the surface of rocks. The stem is slender and prostrate, and is covered
with numerous brown scales. The leaves are pinnate in this fern also, but we
find no difference between the fertile and sterile leaves (except in some rare
cases). The fruit-dots occupy much the same positions on the under side of the
leaf that they do in the Christmas fern, but we cannot find any indusium. In
the place of an indusium are club-shaped hairs as shown in fig. 208. The en-
larged ends of these clubs reaching beyond the sporangia give some protection
to them when they are young.

357. Other ferns. — We might examine a series of ferns to see how different
they are in respect to the position which the fruit dots occupy on the leaf. The
common brake, which sometimes covers extensive areas and becomes a trouble-
some weed, has a stout and smooth underground stem (rhizome) which is often
12 to 20 cm beneath the surface of the soil. There is a long leaf stalk, which
bears the lamina, the latter being several times pinnate. The margins of the
fertile pinnae are inrolled, and the sporangia are found protected underneath
in this long sori along the margin of the pinna. The beautiful maidenhair fern
and its relatives have obovate pinnae, and the sori are situated in the same posi-
tions as in the brake. In other ferns, as the walking fern, the sori are borne
along by the side of the veins of the leaf.

358. Opening of the leaves of ferns. — The leaves of ferns open in a peculiar
manner. The tip of the leaf is the last portion developed, and the growing

174

MORPIfOLOG Y.

leaf appears as if it was rolled up as in fig. 204 of the Christmas fern. As the
leaf elongates this portion unrolls.

359. Longevity of ferns. — Most ferns live from year to year, by growth
adding to the advance of the stem, while by decay of the older parts the stem
shortens up behind. The leaves are short-lived, usually dying down each
year, and a new set arising from the growing end of the stem. Often one can
see just back or below the new leaves the old dead ones of the past season,
and farther back the remains of the petioles of still older leaves.

360. Budding of ferns. — A few
ferns produce what are called bulbils
or bulblets on the leaves. One of
these, which is found throughout the
greater part of the eastern United
States, is the bladder fern (Cystop-
teris bulbifera), which grows in shady
rocky places. The long graceful
delicate leaves form in the axils of
the pinnae, especially near the end of
the leaf, small oval bulbs as shown
in fig. 212. If we examine one of
these bladder-like bulbs we see that
the bulk of it is made up of short
thick fleshy leaves, smaller ones ap-
pearing between the outer ones at the
smaller end of the bulb. This bulb
contains a stem, young root, and
several pairs of these fleshy leaves.
They easily fall to the ground or
rocks, where, with the abundant
moisture usually present in localities
where the fern is found, the bulb
grows until the roots attach the plant
to the soil or in the crevices of the
rocks. A young plant growing from
one of these bulbils is shown in fig. 212.

361. Greenhouse ferns. — Some of the ferns grown in conservatories have
similar bulblets. Fig. 213 represents one of these which is found abundantly
on the leaves of Asplenium bulbiferum. These bulbils have leaves which are
very similar to the ordinary leaf except that they are smaller. The
bulbs are also much more firmly attached to the leaf, so that they do not
readily fall away.

362. Plant conservatories usually furnish a number of very interesting
ferns, and one should attempt to make the acquaintance of some of them, for

Fig. 212.

Cystopteris bulbifera, young plant growing
from bulb. At right is young bulb in axil oi
pinna of leaf.

FERWS.

'75

here one has an opportunity during the winter season not only to observe these
interesting plants, but also to obtain material for study. In the tree ferns
which often are seen growing in such places we see examples of the massive
trunks and leaves of some of the tropical species.

363. The fern plant is a sporophyte. — We have now studied
the fern plant, as we call it, and we have found it to represent
the spore-bearing phase of the plant, that is the sporophyte (cor-
responding to the sporogonimn of the liverworts and mosses).

364. Is there a ga-
in etophyte phase in
ferns ? — But in the spor-
ophyte of the fern, which
we should not forget is
the fern plant, we have
a striking advance upon
the sporophyte of the
liverworts and mosses.
In the latter plants the
sporophyte remained
attached to the gameto-
phyte, and derived its
nourishment from it.
In the ferns, as we see,
the sporophyte has a
root of its own, and is
attached to the soil.
Through the aid of root

hairs of its own it takes up mineral solutions. It possesses also
a true stem, and true leaves in which carbon conversion takes
place. It is able to live independently, then. Does a gametophyte
phase exist among the ferns ? Or has it been lost ? If it does
exist, what is it like, and where does it grow ? From what we
have already learned we should expect to find the gametophyte
begin with the germination of the spores which are developed
on the sporophyte, that is on the fern plant itself. We should
investigate this and see.

Fig. 213.
Bulbil growing from leaf of asplenium (A , bulbiferum).

CHAPTER XXVI.

FERNS CONTINUED.
Gametophyte of ferns.

365. Sexual stage of ferns. — We now wish to see what the
sexual stage of the ferns is like. Judging from what we have
found to take place in the liverworts and mosses we would infer

Fig. 7.14.

Prothallium of fern, under side, showing rhizoids, antheridia scattered among and near
them, and the archegonia near the sinus.

that the form of the plant which bears the sexual organs is de-
veloped from the spores. This is true, and if we should examine
old decaying logs, or decaying wood in damp places in the near

176

1 77

Fig. 2,5.

Spore of Pteris serru-
lata showing the three-
rayed elevation along
the side of which the
spore wall cracks during
germination.

vicinity of ferns, we would probably find tiny, green, thin, heart-
shaped growths, lying close to the substratum. These are also
found quite frequently on the soil of pots in plant conservatories
where ferns are grown. Gardeners also in conservatories usually
sow fern spores to raise new fern plants,
and usually one can find these heart-shaped
growths on the surface of the soil where
they have sown the spores. We may call
the gardener to our aid in finding them in
conservatories, or even in growing them for
us if we cannot find them outside. In some
cases they may be grown in an ordinary room
by keeping the surfaces where they are
growing moist, and the air also moist, by
placing a glass bell jar over them.

366. In fig. 214 is shown one of these growths enlarged.
Upon the under side we see numerous thread-like outgrowths,
the rhizoids, which attach the plant to the substratum, and which
act as organs for the absorption of nourishment. The sexual

organs are
borne on the
under side also,
and we will
study them
later. This
heart-shaped,
flattened, thin,
green plant is
the prothallium

of ferns, and we should now give it more careful study, be-
ginning with the germination of the spores.

367. Spores. — We can easily obtain material for the study of
the spores of ferns. The spores vary in shape to some extent.
Many of them are shaped like a three-sided pyramid. One of
these is shown in fig. 215. The outer wall is roughened, and
on one end are three elevated ridges which radiate from a given

Fig. 216.

Spore of Adiantum
acrostichoides with
winged exospore.

Fig. 217.

Spore crushed to remove exospore and
show endospore.

I78

MORPHOLOG Y.

Fig. 218.

Spores of asplenium ; exospore re-
moved from the one at the right.

point. A spore of the Christmas fern is shown in fig. 216. The
outer wall here is more or less winged. At fig. 217 is a spore

of the same species from which the
outer wall has been crushed, showing
that there is an inner wall also. If
possible we should study the germi-
nation of the spores of some fern.

368. Germination of the spores.
— After the spores have been sown for
about one week to ten days we should
mount a few in water for examination
with the microscope in order to study
the early stages. If germination has begun, we will find that here
and there are short slender green threads, in many cases attached

to brownish bits, the old
walls of the spores.
Often one will sow the
sporangia along with the
spores, and in such cases
there may be found a
number of spores still
within the old sporan-
gium wall that are ger-
minating, when they will
appear as in fig. 219.

369. Protonema.—
These short green threads
are called protonemal threads, or protonema,
which means a first thread, and it here
signifies that this short thread only pre-
cedes a larger growth of the same object.
In figs. 219, 220 are shown several stages of
germination of different spores. Soon after
of the short germ tube emerges from the
n the crack in the spore wall, it divides by the

FEKNS. I /9

formation of a cross wall, and as it increases in length other
cross walls are formed. But very early in its growth we see that
a slender outgrowth takes place from the cell nearest the old
spore wall. This slender thread
is colorless, and is not divided
into cells. It is the first rhizoid,
and serves both as an organ of
attachment for the thread, and for
taking up nutriment.

370. Prothallium. — Very soon,
if the sowing has not been so
crowded as to prevent the young
plants from obtaining nutriment
sufficient, we will see that the end
of this protonema is broadening,
as shown in fig. 220. This is done
by the formation of the cell walls
in different directions. It now
continues to grow in this way, the
end becoming broader and broader,
and new rhizoids are formed from
the under suriace of the cells. The
growing point remains at the mid-
dle of the advancing margin, and
the cells which are cut off from
either side, as they become old,

widen out. In this way the Young prothau£*Hi a fern (nipho-

" wings," or margins of the bolus)-

little, green, flattened body, are in advance of the growing

point, and the object is more or less heart-shaped, as shown

in fig. 214. Thus we see how the prothallium of ferns is

formed.

371. Sexual organs of ferns. — If we take one of the prothal-
lia of ferns which have grown from the sowings of fern spores,
or one of those which may be often found growing on the soil

i8o

MORPHOLOG Y.

of pots in conservatories, mount it in water on a slip, with
the under side uppermost, we can then examine it for the

Male prothallium of a fern (niphobolus), in form of an alga or protonema. Spermato-
zoids escaping from antheridia.

sexual organs, for these are borne in most cases on the under
side.

372. Antheridia. — If we search among the rhizoids we will
see small rounded elevations as shown in fig. 214 or 222 scat-

Fig. 222.

Male prothallium of fern (niphobolus), showing opened and unopened antheridia ; 39, sec-
tion of unopened antheridium; 40, spermatozoids escaping ; 41, spermatozoids which did not
escape from the antheridium.

FERNS.

181

These are the an-

tered over this portion of the prothallium.

theridia. Ifthepro-

thallia have not been

watered for a day or

so, we may have an

opportunity of see-
ing the spermato-

zoids coming out of

the antheridium, for

when the prothallia o£ antheridia sh^3sperm cellSj and spermato.

are freshly placed in «>ids in the one at the right.

water the cells of the antheridium ab-
sorb water. This presses on the con-
tents of the antheridium and bursts the
cap cell if the antheridium is ripe, and
all the spermatozoids are shot out.
We can see here that each one is
shaped like a screw, with the coils at
matozoids; first close. But as the spermatozoid

motion (Adiantum concinnSin)44' '" begins tO lllOVC this coil Opens SOme-

what and by the vibration of
the long cilia which are on the
smaller end it whirls away. In
such preparations one may often
see them spinning around for a
long while, and it is only when
they gradually come to rest
that one can make out their
form.

373. Archegonia. — If we now
examine closely on the thicker
part of the under surface of the
prothallium, just back of the

" sinUS," We may See longer venter'is Ae* egg1, next' is 7he*ventral canal

cell, and in the canal of the neck are two
StOUt projections from the Surface nuclei of the canal cell.

of the prothallium. These are shown in fig. 214, They are

Fig. 224.

Different views of s
42, 43, in a quiet c

Fig. 225.
Archegonium of fern. Large cell in the

182

MORPHOLOGY.

the archegonia. One of them in longisection is shown in fig.
225. It is flask-shaped, and the broader portion is sunk in the

.sp

Fig. 226.

Mature and open archegonium of fern (Adiantum cuneatum) with spermatozoids making
their way down through the slime to the egg.

tissue of the prothallium. The egg is in the larger part. The
spermatozoids when they are swimming
around over the under surface of the pro-
thallium come near the neck, and here they
are caught in the viscid substance which
has oozed out of the canal of the arche-
gonium. From here they slowly swim
down the canal, and finally one sinks into
the egg, fuses with the nucleus of the latter,
and the egg is then fertilized. It is now
ready to grow and develop into the fern
plant. This brings us back to the sporo-

Fig. 227.

Fertilization in a fern
i Marattia). s/>, spermato-

CampbelL

phyte, which begins with the fertilized egg.

Sporophyte.

374. Embryo. — The egg first divides into two cells as shown in fig. 228, then
into four. Now from each one of these quandrants of the embryo a definite
part of the plant develops, from one the first leaf, from one the stem, from
one the root, and from the other the organ which is called the foot, and which

FERNS. 183

attaches the embryo to the prothallium, and transports nourishment for the
embryo until it can become attached to the soil and lead an independent ex-
istence. During this time the wall of the archegonium grows somewhat to
accommodate the increase in size of the embryo, as shown in figs. 229, 230.
But soon the wall of the archegonium is ruptured and the embryo emerges,
the root attaches itself to the soil, and soon the prothallium dies.

The embryo is first on the under side of the prothallium, and the first leaf

Fig. 22*

Two-celled embryo of Pteris serrulata. Remnant of archegonium neck below.

and the stem curves upward between the lobes of the heart-shaped body, and
then grows upright as shown in fig. 231. Usually only one embryo is formed
on a single prothallium, but in one case I found a prothallium with two well-
formed embryos, which are figured in 232.

375. Comparison of ferns with liverworts and mosses. — In the ferns then
we have reached a remarkable condition of things as compared with that
which we found in the mosses and liverworts. In the mosses and liverworts

1 84

MORPHOLOG Y.

the sexual phase of the plant (gametophyte) was the prominent one,
and consisted of either a thallus or a leafy axis, but in either case it bore the
sexual organs and led an independent existence; that is it was capable of ob-
taining its nourishment from the soil or water by means of organs of absorp-
tion belonging to itself, and it also performed the office of carbon conversion.
376. The spore-bearing phase (sporophyte) of the liverworts and mosses,
on the other hand, is quite small as compared with the sexual stage, and it is

F

li-

Fig. 229.

Young embryo of fern (Adiantum concinnum) in enlarged venter of the archegonium. S,
stem ; L, first leaf or cotyledon ; R, root ; F, foot.

completely dependent on the sexual stage for its nourishment, remaining at-
tached permanently throughout all its development, by means of the organ
called a foot, and it dies after the spores are mature.

377. Now in the ferns we see several striking differences. In the first
place, as we have already observed, the spore-bearing phase (sporophyte) of

FERNS.

I85

the plant is the prominent one, and that which characterizes the plant. It
also leads an independent existence, and, with the exception of a few cases,
does not die after the development of the spores, but lives from year to year
and develops successive crops of spores. There is a distinct advance here in
the size, complexity, and permanency of this phase of the plant.

378. On the other hand the sexual phase of the ferns (gametophyte), while
it still is capable of leading an independent existence, is short-lived (with verv
few exceptions). It is also much smaller than most of the liverworts and

Embryo of fern (Adiantum concinnum) still surrounded by the archegonium, which has
grown in size, forming the " calyptra." L, leaf ; S, stem ; A', root ; F, foot.

mosses, especially as compared with the size of the spore-bearing phase.
The gametophyte phase or stage of the plants, then, is decreasing in size and
durance as the sporophyte stage is increasing. We shall be interested to see
if this holds good of the fern allies, that is of the plants which belong to the
same group as the ferns. And as we come later to take up the study of the
higher plants we must bear in mind to carry on this comparison, and see if
this progression on the one hand of the sporophyte continues, and if the
retrogression of the gametophyte continues also.

1 86

MORPHOLOG

Fig. 231.

Young plant of Pteris serrulata still
attached to prothallium.

Fig. 232.

Two embryos from one prothallium of
Adiantum cuneatum.

CHAPTER XXVII.

HORSETAILS.

379. Among the relatives of the ferns are the
horsetails, so called because of the supposed resem-
blance of the branched stems of some of the species
to a horse's tail, as one might infer from the plant
shown in fig. 239. They do not bear the least re-
semblance to the ferns which we have been study-
ing. But then relationship in plants does not depend
on mere resemblance of outward form, or of the promi-
nent part of the plant.

380. The field equisetum. Fertile shoots. — Fig.
2 33 represents the common horsetail (Equisetum ar-
vense). It grows in moist sandy or gravelly places,
and the fruiting portion of the plant (for this species
is dimorphic), that is the portion which bears the
spores, appears above the ground early in the spring.
It is one of the first things to peep out of the recently
frozen ground. This fertile shoot of the plant does
not form its growth this early in the spring. Its
development takes place under the ground in the
autumn, so that with the advent of spring it pushes
up without delay. This shoot is from 10 to 20
cm high, and at quite regular intervals there are
slight enlargements, the nodes of the stem. The
cylindrical portions between the nodes are the
internodes. If we examine the region of the inter-
nodes carefully we note that there are thin mem- j
branous scales, more or less triangular in outline, and
connected at their bases into a ring around the stem.

187

1 88 MORPHOLOG Y.

Curious as it may seem, these are the leaves of the horsetail.
The stem, if we examine it farther, will be seen to possess numer-
ous ridges which extend lengthwise and which alternate with
furrows. Farther, the ridges of one node alternate with those
of the internode both above and below. Likewise the leaves
of one node alternate with those of the nodes both above and
below.

381. Sporangia. — The end of this fertile shoot we see pos-
sesses a cylindrical to conic enlargement. This is the fertile

spike, and we note that its surface is marked off
into regular areas if the spores have not yet been
disseminated. If we dissect off a few of these por-
tions of the fertile spike, and examine one of them
with a low magnifying power, it will appear like the
fig. 234. We see here that the angular area is a
Fig. 234. disk-shaped body, with a stalk attached to its inner
phyf/ crfequfsetum surface, and with several long sacs projecting from
!ngesporangfaTn its inner face parallel with the stalk and surrounding
the same. These elongated sacs are the sporangia,
and the disk which bears them, together with the stalk which
attaches it to the stem axis, is the sporophyll, and thus belongs to
the leaf series. These sporophylls are borne in close whorls on
the axis.

382. Spores. — When the spores are ripe the tissue of the
sporangium becomes dry, and it cracks open and the spores fall
out. If we look at fig. 235 we will see that the spore is covered
with a very singular coil which lies close to the wall. When the
spore dries this uncoils and thus rolls the spore about. Merely
breathing upon these spores is sufficient to make them perform
very curious evolutions by the twisting of these four coils which
are attached to one place of the wall. They are formed by the
splitting up of an outer wall of the spore.

383. Sterile shoot of the common horsetail. — When the
spores are ripe they are soon scattered, and then the fertile
shoot dies down. Soon afterward, or even while some of the
fertile shoots are still in good condition, sterile shoots of the

HORSETAILS.

I89

plant begin to appear above the ground. One of these is shown
in fig. 237. This has a much more slender stem and is pro-

Fig. 236.

Spore of equisetum with elaters un-
coiled.

Fig. 235.

Spore of equisetum
with elaters coiled up.

vided with numerous branches. If we ex-
amine the stem of this shoot, and of the
branches, we will see that the same kind of
leaves are present and that the markings on
the stem are similar. Since the leaves of
the horsetail are membranous and not green,
the stem is green in color, and this per-
forms the function of carbon conversion.
These green shoots live for a great part of
the season, building up material which is
carried down into the underground stems,
where it goes to supply the forming fertile
shoots in the fall. On digging up some of
these plants we see that the underground
stems are often of great extent, and that
both fertile and sterile shoots are attached
to one and the same.

384. The scouring rush, or shave grass.
—Another common species of horsetail in
the Northern States grows on wet banks,
or in sandy soil which contains moisture
along railroad embankments. It is
the scouring rush (E. hyemale), so
called because it was once used for
polishing purposes. This plant like
all the species of the horsetails has

Fig. 237.
Sterile plant of horsetail (Equi-

MORPHOLOGY.

underground stems. But unlike the common horsetail, there is
but one kind of aerial shoot, which is green in color and fertile.
The shoots range as high as one meter or more, and are quite
stout. The new shoots which come up for the year are un-
branched, and bear the fertile spike at the apex. When the
spores are ripe the apex of the shoot dies, and the next season
small branches may form from a number of the nodes.

385. Gametophyte of equisetum. — The spores of equisetum have chloro-
phyll when they are mature, and they are capable of germinating as soon as
mature. The spores are all of the same kind as regards size, just as we
found in the case of the ferns. But they develop prothallia of different
sizes, according to the amount of nutriment which they obtain. Those
which obtain but little nutriment are smaller and develop only antheridia,
while those which obtain more nutriment become larger, more or less
branched, and develop archegonia. This character of an independent pro-
thallium (gametophyte) with the characteristic sexual organs, and the also
independent sporophyte, with spores, shows the relationship of the horsetails
with the ferns. We thus see that these characters of the reproductive
organs, and the phases and fruiting of the plant, are more essential in deter-
mining relationships of plants than the mere outward appearances.

CHAPTER XXVIII.

CLUB MOSSES.

386. What are called the "club mosses" make up another
group of interesting plants which rank as allies of the ferns.
They are not of course true mosses, but the general habit of
some of the smaller species, and especially the

form and size of the leaves, suggest a resem-
blance to the larger of the moss plants.

387. The clavate lycopodium. — Here is one
of the club mosses (fig. 238) which has a wide
distribution and which is well entitled to hold
the name of club because of the form of the up-
right club-shaped branches. As will be seen
from the illustration, it has a prostrate stem.
This stem runs for considerable distances on
the surface of the ground, often partly buried in
the leaves, and sometimes even buried beneath
the soil. The leaves are quite small, are flat-
tened-awl-shaped, and stand thickly over the
stem, arranged in a spiral manner, which is the
usual arrangement of the leaves of the club
mosses. Here and there are upright branches
which are forked several times. The end of
one or more of these branches becomes pro-
duced into a slender upright stem which is
nearly leafless, the leaves being reduced to
mere scales. The end of this leafless branch
then terminates in one or several cylindrical
heads which form the club.

191

sP°renearlt-

1 92 MO RP HO LOG Y.

388, Fruiting spike of Lycopodium clavatum. — This club is
the fruiting spike or head (sometimes termed a strobilus). Here
the leaves are larger again and broader, but still not so large as
the leaves on the creeping shoots, and they are paler. If we bend
down some of the leaves, or tear off a few, we will see that in the
axil of the leaf, where it joins the stem, there is a somewhat
rounded, kidney -shaped body. This, is the spore -case or spo-
rangium, as we can see by an examination of its contents. There
is but a single spore-case for each of the fertile leaves (sporophyll).
When it is mature, it opens by a crosswise slit as seen in fig. 238.
When we consider the number of spore -cases in one of these club-
shaped fruit bodies we see that the number of spores developed
in a large plant is immense. In mass the spores make a very fine,
soft powder, which is used for some
kinds of pyrotechnic material, and for
various toilet purposes.

389. Lycopodium lucidulum. — Another com-
mon species is figured at 239. This is Lycopo-
dium lucidulum. The habit of the plant is quite
different. It grows in damp ravines, woods, and
moors. The older parts of the stem are prostrate,
while the branches are more • or less ascending.
It branches in a forked manner. The leaves are
larger than in the former species, and they are
all of the same size, there being no appreciable
difference between the sterile and
fertile ones. The characteristic
club is not present here, but the
spore-cases occupy certain regions of
the stem, as shown at 239. In a
single season one region of the stem
may bear spore-cases, and then a
sterile portion of the same stem is

c developed, which later bears another
Lycopodium lucidulum, bulbils in axils of

leaves near the top, sporangia in axils of leaves series of spore-cases higher up.
below them. At right is a bulbil enlarged. nnn -,•,•.., -r •,•

390. Bulbils on Lycopodium

lucidulum. — There is one curious way in which this club moss multiplies.
One may see frequently among the upper leaves small wedge-shaped or heart-
shaped green bodies but little larger than the ordinary leaves. These are little

LITTLE CLUB MOSSES. 193

buds which contain rudimentary shoot and root and several thick green leaves.
When they fall to the ground they grow into new lycopodium plants, just as
the bulbils of cystopteris do which were described in the chapter on ferns.

391. Note. — The prothallia of the species of lycopodium which have been
studied are singular objects. In L. cernuum a cylindrical body sunk in the
earth is formed, and from the upper surface there are green lobes. In L.
phlegmaria and some others slender branched, colorless bodies are formed
which according to Treub grow as a saphrophyte in decayed bark of trees.
Many of the prothallia examined have a fungus growing in their tissue which
is supposed to play some part in the nutrition of the prothallium.

The little club mosses (selaginella).

392. Closely related to the club mosses are the selaginellas.
These plants resemble closely the general habit of the club mosses,
but are generally smaller and the leaves more delicate. Some
species are grown in conservatories for ornament, the leaves of

Fig. 240. Fig. 241. Fig. 242. Fig. 243.

Selaginella with Fruiting spike Large spo- Small spo-

three fruiting spikes, showing large and rangium. rangium.

(.Selaginella apus.) small sporangia.

such usually having a beautiful metallic lustre. The leaves of some
are arranged as in lycopodium, but many species have the leaves
in four to six rows. Fig. 240 represents a part of a selaginella
plant (S. apus). The fruiting spike possesses similar leaves, but
they are shorter, and their arrangement gives to the spike a four-
sided appearance.

1 94 MORPHO LOGY,

393. Sporangia. — On examining the fruiting spike, we find
as in lycopodium that there is but a single sporangium in the
axil of a fertile leaf. But we see that they are of two different
kinds, small ones in the axils of the upper leaves, and large ones
in the axils of a few of the lower leaves of the spike. The micro-
spores are borne in the smaller spore-cases and the macrospores
in the larger ones. Figures 241-243 give the details. There
are many microspores in a single small spore-case, but 3-4 ma-
crospores in a large spore-case.

394. Male prothallia. — The prothallia of selaginella are much
reduced structures. The microspores when mature are already
divided into two cells. When they grow into the mature pro-
thallium a few more cells are formed, and some of the inner ones
form the spermatozoids, as seen in fig. 244. Here we see that

Fig. 244.

Details of microspore and male prothallium of selaginella ; ist, microspore : 2d, wall re-
moved to show small prothallial cell below ; 3d, mature male prothallium still within the
wall ; 4th, small cell below is the prothallial cell, the remainder is antheridium with wall and
three sperm cells within ; 5th spermatozoid. After Beliaieff and Pfeffer.

the antheridium itself is larger than the prothallia. Only an-
theridia are developed on the prothallia formed from the
microspores, and for this reason the prothallia are called male
prothallia. In fact a male prothallium of selaginella is nearly
all antheridium, so reduced has the gametophyte become here.

395. Female prothallia. — The female prothallia are devel-
oped from the macrospores. The macrospores when mature have
a rough, thick, hard wall. The female prothallium begins to
develop inside of the macrospore before it leaves the sporangium.
The protoplasm is richer near the wall of the spore and at the

LITTLE CLUB MOSSES.

195

upper end. Here the nucleus divides a great many times, and
finally cell walls are formed, so that a tissue of considerable ex-
tent is formed inside the wall of the spore, which is very
different from what takes place in the ferns we have
studied. As the prothallium matures the spore is cracked
at the point where the three angles meet, as shown in
fig. 246. The archegonia are developed in this exposed
surface, and several can be seen in the illustration.

396. Embyro. — After fertilization the egg divides in such a way
that a long cell called a suspensor is cut off from the upper side,

Fig. 245-
Section of mature macrospore

Fig. 246.
Mature female prothallium of

of selagmella, showing female selaginella, just bursting open
archegonia. the wall of macrospore, exposing

prothallium and
After Pfeffer.

archegonia. After Pfeffer.

Fig. 247.

Seedling of sela-
ginella still attached
to the macrospore.
After Campbell.

which elongates and pushes the developing embyro down into the center of
the spore, or what is now the female prothallium. Here it derives nourish-
ment from the tissues of the prothallium, and eventually the root and stem
emerge, while a process called the " foot " is still attached to the prothallium.
When the root takes hold on the soil the embyro becomes free.

CHAPTER XXIX.

QUILLWORTS (ISOETES).

397. The quillworts, as they
are popularly called, are very
curious plants. They grow in
wet marshy places. They receive
their name from the supposed
resemblance of the leaf to a quill.
Fig. 248 represents one of these
quillworts (Isoetes engelmannii).
The leaves are the prominent
part of the plant, and they are
about all that can be seen except
the roots, without removing the
leaves. Each leaf, it will be
seen, is long and needle-like, ex-
cept the basal part, which is
expanded, not very unlike, in out-
line, a scale of an onion. These
expanded basal portions of the
leaves closely overlap each other,
and the very short stem is com-
pletely covered at all times. Fig.
250 is from a longitudinal sec-
tion of a quillwort. It shows
the form of the leaves from this
view (side view), and also the

Isoetes, mature plant, sporophyte stage, general outline of the short Stem,

which is triangular. The stem is therefore a very short object.

196

248.

QUILLWORTS.

197

398. Sporangia of isoetes. — If we pull off some of the
leaves of the plant we see that they are somewhat spoon-shaped
as in fig. 249. In the inner surface of the expanded base we
note a circular depression which seems to be of a different text-

Fig. 249.

Base of leaf of isoetes,
showing sporangium with
macrospores. (Isoetes en-
gelmannii.)

Fig. 250.

Section of plant of Isoetes engelmanii, showing cup-
shaped stem, and longitudinal sections of the sporan-
gia in the thickened bases of the leaves.

ure from the other portions of the leaf. This is a sporangium.
Beside the spores on the inside of the sporangium, there are
strands of sterile tissue which extend across the cavity. This is
peculiar to isoetes of all the members of the class of plants to
which the ferns belong, but it will be remembered that sterile
strands of tissue are found in some of the liverworts in the form
of elaters.

399. The spores of isoetes are of two kinds, small ones
(microspores) and large ones (macrospores), so that in this
respect it agrees with selaginella, though it is so very different in
other respects. When one kind of spore is borne in a sporan-

1 98 MORPHOL OGY.

gium usually all in that sporangium are of the same kind, so that
certain sporangia bear microspores, and others bear macrospores.
But it is not uncommon to find both kinds in the same sporan-
gium. When a sporangium bears only microspores the number
is much greater than when one bears only macrospores.

400. If we examine some of the microspores of isoetes we see that they are
shaped like the quarters of an apple, that is they are of the bilateral type as
seen in some of the ferns (asplenium).

401. Male prothallia. — In isoetes, as in selaginella, the microspores de-
velop only male prothallia, and these are very rudimentary, one division of
the spore having taken place before the spore is mature, just as in selagi-
nella.

402. Female prothallia. — These are developed from the macrospores. The
latter are of the tetrahedral type. The development of the female prothal-
lium takes place in much the same way as in selaginella, the entire prothal-
lium being enclosed in the macrospore, though the cell divisions take place
after it has left the sporangium. When the archegonia begin to develop
the macrospore cracks at the three angles and the surface bearing the arche-
gonia projects slightly as in selaginella.

403. Embryo. — The embryo lies well immersed in the tissue of the pro-
thallium, though there is no suspensor developed as in selaginella.

CHAPTER XXX.

COMPARISON OF FERNS AND THEIR RELATIVES.

404. Comparison of selaginella and isoetes with the ferns. — On compar-
ing selaginella and isoetes with the ferns, we see that the sporophyte is, as
in the ferns, the prominent part of the plant. It possesses root, stem, and
leaves. While these plants are not so large in size as some of the ferns,
still we see that there has been a great advance in the sporophyte of selagi-
nella and isoetes upon what exists in the ferns. There is a division of labor
between the sporophylls, in which some of them bear microsporangia with
microspores, and some bear macrosporangia with only macrospores. In the
ferns and horsetails there is only one kind of sporophyll, sporangium, and
spore in a species. By this division of labor, or differentiation, between the
sporophylls, one kind of spore, the microspore, is compelled to form a male
prothallium, while the other kind of spore, the macrospore, is compelled to
form a female prothallium. This represents a progression of the sporophyte
of a very important nature.

405. On comparing the gametophyte of selaginella and isoetes with that
of the ferns, we see that there has been a still farther retrogression in size
from that which we found in the independent and large gametophyte of the
liverworts and mosses. In the ferns, while it is reduced, it still forms
rhizoids, and leads an independent life, absorbing its own nutrient materials,
and assimilating carbon. In selaginella and isoetes the gametophyte does
not escape from the spore, nor does it form absorbing organs, nor develop
assimilative tissue. The reduced prothallium develops at the expense of
food stored by the sporophyte while the spore is developing. Thus, while
the gametophyte is separate from the sporophyte in selaginella and isoetes,
it is really dependent on it for support or nourishment.

406. The important general characters possessed by the ferns and their
so-called allies, as we have found, are as follows: The spore-bearing part,
which is the fern plant, leads an independent existence from the prothallium.
and forms root, stem, and leaves. The spores are borne in sporangia on
the leaves. The prothallium also leads an independent existence, though in
isoetes and selaginella it has become almost entirely dependent on the sporo-

199

200

MORPHOLOG Y.

phyte. The prothallium bears also well -developed antheridia and arche-
gonia. The root, stem, and leaves of the sporophyte possess vascular
tissue. All the ferns and their allies agree in the possession of these char-
acters. The mosses and liverworts have well-developed antheridia and
archegonia, and the higher plants have vascular tissue. But no plant of
either of these groups possesses the combined characters which we find in
the ferns and their relatives. The latter are. therefore, the fern-like plants,
QT pteridophyla. The living forms of the pteridophyta are classified as fol-
lows into families or orders.

407.

Class I. Filicales.

Pteridophyta.

1 Homosporous. \ Ophioglossace*.
Eusporangiatae — -I ( Marattiaceae.

( ? Heterosporous (Isoetaceae (Isoetes).
[ Osmundaceae.
! Schizaeaceae.
Gleicheniaceae.
Hymenophyl-

laceae.
Homosporous. j Cyatheacea.

Polypodiaceae.

Leptosporangiatae. -

Polypodium, Ono-
clea, Aspidium,
etc.

C,assII.Eqaisetale,|E^rt:m)

;terosporous.j— -— ;
Homosporous. J ^^^^T^

Class III. Lycopodiales.

[ Heterosporous. (Selaginellaceae (Selaginella).

COMPARISON OF PTERIDOPHYTA.

201

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CHAPTER XXXI.

GYM NOSPERMS.
The white pine.

409. General aspect of the white pine. — The white pine
(Pinus strobus) is found in the Eastern United States. In
favorable situations in the forest it reaches a height of about 50
meters (about 160 feet), and the trunk a diameter of over i
meter. In well-formed trees the trunk is straight and towering;
the branches where the sunlight has access and the trees are not
crowded, or are young, reaching out in graceful arms, form a
pyramidal outline to the tree. In old and dense forests the lower
branches, because of lack of sunlight, have died away, leaving
tall, bare trunks for a considerable height.

410. The long shoots of the pine. — The branches are of two kinds. Those
which we readily recognize are the long branches, so called because the
growth in length each year is considerable. The terminal bud of the long
branches, as well as of the main stem, continues each year the growth of the
main branch or shoot; while the lateral long branches arise each year from
buds which are crowded close together around the base of the terminal bud.
The lateral long branches of each year thus appear to be in a whorl. The
distance between each false whorl of branches, then, represents one year's
growth in length of the main stem or long branch.

411. The dwarf shoots of the pine. — The dwarf branches are all lateral
on the long branches, or shoots. They are scattered over the year's growth,
and each bears a cluster of five long, needle-shaped, green leaves, which
remain on the tree for several years. At the base of the green leaves are
a number of chaff-like scales, the previous bud scales. While the dwarf
branches thus bear green leaves, and scales, the long branches bear only
thin scale-like leaves which are not green.

202

GYMNOSPERMS : WHITE PINE.

203

412. Spore-bearing leaves of the pine. — The two kinds of
spore -bearing leaves of the pine, and their close relatives, are
so different from anything which we have yet studied, and are
so unlike the green leaves of the pine, that we would scarcely
recognize them as belonging to this category. Indeed there is
great uncertainty regarding their origin.

413. Male cones, or male flowers. — The male cones are borne
in clusters as shown in fig. 251. Each compact, nearly cylindri-

Fig. 251.
Spray of white pine showing cluster of male cones just before the scattering of the pollen.

cal, or conical mass is termed a cone, or flower, and each arises
in place of a long lateral branch. One of these cones is shown

2O4

MORPHOLOG Y.

considerably enlarged in fig. 252. The central axis of each
cone is a lateral branch, and belongs to the stem series. The
stem axis of the cone can be seen in fig. 253. It is completely
covered by stout, thick, scale-like outgrowths. These scales
are obovate in outline, and at the inner angle of the upper end

Fig. 252. Fig. 253. Fig. 254.

Staminate cone of white Section of staminate Two sporo-
pine, with bud scales re- cone, showing sporangia, phylls removed,
moved on one side. showing open-

ing of sporangia.

there are several rough, short spines. They are attached by
their inner lower angle, which forms a short stalk or petiole,
and continues through the inner face of the scale as a "mid-
rib." What corresponds to the lamina of the scale-like leaf
bulges out on each side below and makes the bulk of the scale.
These prominences on the under side are the sporangia (micro-
sporangia). There are thus two sporangia on a sporophyll
(microsporophyll). When the spores (microspores), which
here are usually called pollen grains, are mature each sporangium,

or anther locule, splits down the middle as

shown in fig. 254, and the spores are set free.
414. Microspores of the pine, or pollen

grains. — A mature pollen grain of the pine is
f shown in fig. 255. It is a queer-looking object,

possessing on two sides an air sac, formed by the
upheaval of the outer coat of the spore at these two points.

Fig. 255.
Pollen grain
white pine.

GYMNOSPERMS: WHITE PINE.

205

When the pollen is mature, the moisture dries out of the scale
(or stamen, as it is often called here) while
it ripens. When a limb, bearing a cluster
of male cones, is jarred by the hand, or by
currents of air, the split suddenly opens, and
a cloud of pollen bursts out from the numer-
ous anther locules. The pollen is
thus borne on the wind and some of

it falls on the

female flowers.

Fig. 256.

White pine, branch with cluster of
mature cones shedding the seed. A
few young cones four months old
are shown on branch at the left.
Drawn from photograph.

415. Form of the ma-
ture female cone. — A

cluster of the white-
pine cones is shown in
fig. 256. These are
mature, and the scales
have spread as they do when mature and becoming dry, in
order that the seeds may be set at liberty. The general out-

g. 257-

Mature cone of white pine
at time of scattering of the
seed, nearly natural size.

206 MORPHOLOG Y.

line of the cone is lanceolate, or long oval, and somewhat
curved. It measures about 10-15^ long. If we remove one

Fig. 258. Fig. 259. Fig. 260. Fig. 261. Fig. 262.

Sterile scale. Scale with Seeds have Back of scale Winged
Seeds undevel- well- developed split off from with small cover seed free from
oped. seeds. scale. scale. scale.

P'igs. 258-262. — White pine showing details of mature scales and seed.

of the scales, just as they are beginning to spread, or before the
seeds have scattered, we shall find the seeds at-
tached to the upper surface at the lower end.
There are two seeds on each scale, one at each
lower angle. They are ovate in outline, and
shaped somewhat like a biconvex lens. At this
time the seeds easily fall away, and may be
freed by jarring the cone. As the seed is
detached from the scale a strip of tissue from
the latter is peeled off. This forms a " wing "
for the seed. It is attached to one end and is
shaped something like a knife blade. On the
back of the scale is a small appendage known
as the cover scale.

416. Formation of the female pine cone. — The female
flowers begin their development rather late in the spring
of the year. They are formed from terminal buds of
the higher branches of the tree. In this way the cone
may terminate the main shoot of a branch, or of the
Fig. 263. lateral shoots in a whorl. After growth has proceeded

Female cones of the for some time in the spring, the terminal portion begins
pine at time of pollina-
tion, about natural size, to assume the appearance of a young female cone or

GYMNOSPERMS: WHITE PINE.

2O7

flower. These young female cones, at about the time that the pollen is
escaping from the anthers, are long ovate, measuring alxmt 6-iomm long.
They stand upright as shown in fig. 263.

417. Form of a " scale " of the female flower. — If we remove
one of the scales from the cone at this stage we can better study
it in detail. It is flattened, and oval in
outline, with a stout " rib," if it may be so
called, running through the middle line and
terminating in a point. The scale is in
two parts as shown in fig. 266, which is a
view of the under side. The small "out-
growth ' ' which appears as an appendage is
the cover scale, for while it is smaller in the
pine than the other portion, in some of
the relatives of the pine it is larger than its
mate, and being on the outside, covers it.
(The inner scale is sometimes called the ovu-
liferous scale, because it bears the ovules. )

418. Ovules, or macrosporangia, of the
pine. — At each of the lower angles of the

Fig. 264.

Section of female cone
of white pine, showing
young ovules (macrospo-
rangia ) at base of the ovu-
liferous scales.

Fig. 265.

Scale of white pine with the
two ovules at base of ovulif-
erous scale.

Fig. 266.

Scale of white pine seen
from the outside, showing the
cover scale.

scale is a curious oval body with two curved, forceps-like pro-
cesses at the lower and smaller end. These are the macro-
sporangia, or, as they are called in the higher plants, the ovules.
These ovules, as we see, are in the positions of the seeds on the

208

MORPHOLOG Y.

mature cones. In fact the wall of the ovule forms the outer coat
of the seed, as we will later see.

419. Pollination. — At the time when the pollen is mature the
female cones are still erect on the branches, and the scales, which
during the earlier stages of growth were closely pressed against
one another around the axis, are now
spread apart. As the clouds of pollen
burst from the clusters of the male cones,
some of it is wafted by the wind to the
female cones. It is here caught in the
open scales, and rolls down to their bases,
where some of it falls between these
forceps-like processes at the
lower end of the ovule. At

Branch of white pine showing young female cones at time of pollination on the ends of

" ili/al

Fig. 267.
^ :emale co
the branches, and one-year-old cones below, near the time of fertilization.

this time the ovule has exuded a drop of a sticky fluid in this
depression between the curved processes at its lower end. The
pollen sticks to this, and later, as this viscid substance dries up,
it pulls the pollen close up in the depression against the lower

GYMNOSPERMS: WHITE PINE.

209

end of the ovule. This depression is thus known as the pollen
chamber.

420. Now the open scales on the young female cone close up
again, so tightly that water from rains is excluded. What is also
very curious, the cones, which up to this

time have been standing erect, so that
the open scale could catch the pollen,
now turn so that they hang downward.
This more certainly excludes the rains,
since the overlapping of the scales forms
a shingled surface. Quantities of resin
are also formed in the scales, which
exudes and makes the cone practically
impervious to water.

421. The female cone now slowly
grows during the summer and autumn,
increasing but little in size during this
time. During the winter it rests, that
is, ceases to grow. With the coming of
spring, growth commences again and
at an accelerated rate. The increase in
size is more rapid. The cone reaches
maturity in September. We thus see
that nearly eighteen months elapse from

the beginning of the female flower to the maturity of the
cone, and about fifteen months from the time that pollination
takes place.

422. Female prothallium of the pine. — To study this we must make careful
longitudinal sections through the ovule (better made with the aid of a micro-
tome). Such a section is shown in fig. 269. The outer layer of tissue, which
at the upper end (point where the scale is attached to the axis of the cone)
stands free, is the ovular coat, or integument. Within this integument, near
the upper end, there is a cone-shaped mass of tissue, which farther down
continues along next the integument in a thinner strip. This mass of tissue
is the nucellus, or the macro sporangium proper. The elliptical mass of tissue
within this, shown in fig. 271 is the female prothallium. or what is usually
here called the endosperm. The conical portion of the nucellus fits over the

Fig. 268,

Macrosporangium of pine
(ovule), int, integument ; «, nu-
cellus; ;«, macrospore. (After
Hoffmeister.)

2IO

MORPHOLOGY.

prothallium, and is called the nucellar cap. Only one end of the endosperm

(prothallium) is shown in fig. 271.

423. Archegonia. — In the upper end of the endosperm (prothallium) are

several archegonia, and they aid us in determining what portion is the female

prothallium. The nucellus is of
course formed before the prothallium.
The latter arises from a cell (macro-
spore) near the center of the nucellus.
This cell is larger, and has a larger
nucleus than its fellows (see fig. 268).
The prothallium here is formed much
in the same way as in selaginella,
where we recollect it begins to de-
velop before the macrospore has

Fig. 269. Fig. 270.

Section of ovule of white pine, int, integ- Upper portion of nucellus of white pine,

ument; f>c, pollen chamber; ft, pollen tube; A', pollen-grain remains ; spc, sperm cells;

n, nucellus; /«, macrospore cavity. vn, vegetative nucleus; pt, pollen tube.

reached its full size, and where the archegonia begin to form before it leaves
the macrosporangium.

421. Male prcthallia. — By the time the pollen is mature the male pro-
thallum is already partly formed. In fig. 255 we can see two well-formed
cells. Other cells are said to be formed earlier, but they become so flattened
that it is difficult to make them out when the pollen grain is mature. At this
stage of development the pollen grain is lodged at the mouth of the ovule,
and is drawn up into the pollen chamber.

425. Farther growth of the male prothallium. — During the summer and
autumn the male prothallium makes some farther growth, but this is slow.
The larger cell, called the vegetative cell, elongates by the formation of a
tube, forming a sac, known as the pollen tube. It is either simple or branched.
Jnside Qf this sac the cells of the prothallium are protected, and farther

GYMNOSPERMS: WHITE PINE.

211

division of the cells takes place here, just as the female prothallium develops
in the cavity of the nucellus, from the macrospore. The nucleus of the vege-
tative cell passes down the cavity of this
tubular sac. The antherid cell, which is the
smaller cell of the pollen grain, in the pine,
divides by a cross wall into a so-called stalk
cell, and a mother sperm cell, the latter
corresponding to the central cell of the an-

Fig. 271.

Section through upper part of nucellus and
endosperm of white pine, showing upper por-
tion of archegonium, the entering sperm cells,
and track of pollen tube ; nc, nucellus : pt,
pollen tube ; spc, sperm cells.

ArcK

Fig. 272.

Last division of the egg in the white
pine cutting off the ventral canal cell
at the apex of the archegonium. End,
endosperm; Arch, archegonium.

theridium, there being no wall formed. The sperm mother cell also passes
down the tubular sac, and divides again into two sperm cells, as shown in
fig. 270. About this time, or rather a little earlier, with the pollen tube part
way through the nucellar cap, winter overtakes it, and all growth ceases
until the following spring.

426. Fertilization. — In the spring the advance of the pollen tube con-
tinues, and it finally passes through the nucellar cap about the time that the
archegonia are formed and the egg cell is mature, as shown in fig. 271. The
pollen tube now opens and the sperm cells escape into the archegonium, and
later one of them fuses with the egg nucleus. The fertilized egg is now
ready to develop into the embryo pine.

427. Homology of the parts of the female cone. — Opinions are divided as
to the homology of the parts of the female cone of the pine. Some consider
the entire cone to be homologous with a flower of the angiosperms. The en.-

212

MORPHOLOG V.

tire scale according to this view is a carpel, or sporophyll, which is divided
into the cover scale and the ovuliferous scale. This division of the sporophyll
is considered similar to that which we have in isoetes, where the sporophyll

Fig. 273. Fig. 274. Fig. 275. Fig. 276.

Archegonium of Picea Archegonium of Picea Embryo of Pine seedling just
vuigaris, sperm cell ap- vulgaris showing fusion white pine re- emerging from the
preaching the nucleus of of sperm nucleus with moved from ground,
egg cell. egg nucleus. seed, showing

several coty-
ledons.

Figs. 273, 274.— Fertilization in picea. (After Strasburger.)

has a ligule above the sporangium, or as in ophioglossum, where the leaf is
divided into a fertile and a sterile portion.

A more' recent view regards each cone scale as a flower, the ovuliferous
scale composed of three united carpels arising in the axil of a leaf, the cover
scale. Two of the carpels are reduced to ovules, and the outer integument
is expanded into the lateral portion of the scale, while the central carpel is
sterile and ends in the point or mucro of the scale.

GYMNOSPERMS: WHITE PINE. 213

Fig. 277.
White-pine seedling casting seed coats.

CHAPTER XXXII.

FURTHER STUDIES ON GYMNOSPERMS.
Cycas.

428. In such gymnosperms as cycas, illustrated in the front-
ispiece, there is a close resemblance to the members of the fern

group, especially the ferns themselves.
This is at once suggested by the form of
the leaves. The stem is short and thick.
The leaves have a stout midrib and
numerous narrow pinnae. In the center
of this rosette of leaves are numerous
smaller leaves, closely overlapping like
bud scales. If we remove one of these
at the time the fruit is forming we see that
in general it conforms to the plan of the
large leaves. There are a midrib and a
number of narrow pinnae near the free
end, the entire leaf being covered with
woolly hairs. But at the lower end, in
place of the pinnae, we see oval bodies.

Macrosporophyll of Cycas r

revoiuta. These are the macrosporangia (ovules)

of cycas, and correspond to the macrosporangia of selaginella,
and the leaf is the macrosporophyll.

429. Female prothallium of cycas. — In figs. 279, 280 are
shown mature ovules, or macrosporangia, of cycas. In 280, which
is aroentgen-ray photograph of 279, the oval prothallium can be
seen. So in cycas, as in selaginella, the female prothallium is

214

FURTHER STUDIES ON GYMNOSPERMS.

21$

developed entirely inside of the macrosporangium, and derives
the nutriment for its growth from the cycas plant, which is the

Fig. 279.
Macrosporangium of Cycas revoluta

Fig. 280.
tograph

ing female prothalhum.

Archegonia are developed in this internal mass of

Roentgen photograph of same, show-
jrothalliu

sporophyte.

cells. This aids us in deter-
mining that it is the prothal-
lium. In cycas it is also called
endosperm, just as in the
pines.

430. If we cut open one of the
mature ovules, we can see the en-
dosperm (prothallium) as a whitish
mass of tissue. Immediately sur-
rounding it at maturity is a thin,
papery tissue, the remains of the
nucellus (macrosporangium), and
outside of this are the coats of the
ovule, an outer fleshy one and an
inner stony one.

431. Microspores, or pollen, of
cycas. — The cycas plant illustrated

in the frontispiece is a female plant. l<ig. 28!.

Male plants also exist which have A sporophyll (stamen) of cycas; sporangia in
,, , , groups on the under side. f>, group of sporangia;

small leaves in the center that bear * open sporangia. (From Warming.)

216

MORPHOLOG V.

only microsporangia. These leaves, while they resemble the ordinary leaves,
are smaller and correspond to the stamens. Upon
the under side, as shown in fig. 281, the microspo-
rangia are borne in groups of three or four, and these
contain the microspores, or pollen grains. The ar-
rangement of these microsporangia on the under side
of the cycas leaves bears a strong resemblance to the
arrangement of the sporangia on the under side of
the leaves of some ferns.

432. The gingko tree is
another very interesting plant
belonging to this same group.
It is a relic of a genus which

n g thick
stem, fern-like
leaves, and
cone of male
flowers.

flourished in the remote
past, and it is interesting
also because of the re-
semblance of the leaves
to some of the ferns like
adiantum, which sug-
gests that this form of
the leaf in gingko has
been inherited from some
fern-like ancestor.

433. While the resem-
blance of the leaves of
someof the gy mnosperms
to those of the ferns sug-
gests fern-like ancestors
for the members of this
group, there is stronger
evidence of such ances-
try in the fact that a pro-
thallium can well be de-
(After termined in the ovules.
The endosperm with its

well-formed archegonia is to be considered a prothallium.

434. Spermatozoils in some gymnosperms. — But within the past two

years it has been discovered in gingko, cycas, and zamia, all belonging to this

Fi 28

Two spermatozoids in end of pollen tu
drawing by Hirase and Ikeno.)

be of cycas.

FURTHER STUDIES ON GYMNOSPERMS. 217

group, that the sperm cells are well-formed spermatozoids. In zamia each
one is shaped somewhat like the half of a biconvex lens, and around the con-
vex surface are several coils of cilia. After the
pollen tube has grown down through the nucellus,
and has reached a depression at the end of the
prothallium (endosperm) where the archegonia
are formed, the spermatozoids are set free from
the pollen tube, swim around in a liquid in this
depression, and later fuse with the egg. In
gingko and cycas these spermatozoids were first
discovered by Ikeno and Hirase in Japan, and
later in zamia by Webber in this country. In
figs. 283-286 the details of the male prothallia
and of fertilization are shown.

435. The sporophyte in the gymnosperms. —
In the pollen grains of the gymnosperms we
easily recognize the characters belonging to the

spores in the ferns and their allies, as well as in Fig. 284.

the liverworts and mosses. They belong to the fertilization in cycas, small

spermatozoid fusing with the

same series of organs, are borne on the same larger female nucleus of the egg.

,-,11 The egg protoplasm fills the

phase or generation of the plant, and are practi- archegonium. (From drawings

cally formed in the same general way, the by Hirase and Ikeno-)
variations between the different groups not being greater than those within
a single group. These spores we have recognized as being the product of
the sporophyte. We are able then to identify the sporophyte as that phase or
generation of the plant formed from the fertilized
egg and bearing ultimately the spores. We see
from this that the sporophyte in the gymnosperms
is the prominent part of the plant, just as we
found it to be in the ferns. The pine tree, then,
Fig., 285. as well as the gingko, cycas, yew, hemlock-

Spermatozoid of gingko, show- spruce, black spruce, the giant redwood of Cali-
ing cilia at one end and tail at
the other (After drawings by tornia, etc., are sporophytes.

While the sporangia (anther sacs) of the male

flowers open and permit the spores (pollen) to be scattered, the sporangia of the
female flowers of the gymnosperms rarely open. The macrospore is developed
within sporangium (nucellus) to form the female prothallium (endosperm).

436. The gametophyte has become dependent on the sporophyte.— In this
respect the gymnosperms differ widely from the pteridophytes, though we see
suggestions of this condition of things in isoetes and selaginella, where the

-"female prothallium is developed within the macrospore, and even in sela-
ginella begins, and nearly completes, its development while still in the spo-
rangium.

218

MORPHOLOG Y.

In comparing the female prothallium of the gymnosperms with that of the
fern group we see a remarkable change has taken place. The female pro-
thallium of the gymno-
Ex ^ r> sperms is very much

A I ! reduced in size. Espe-

Ei >

dally, it no longer leads

an independent existence
from the sporophyte, as
is the case with nearly
all the fern group. It
remains enclosed within
the macrosporangium (in
cycas if not fertilized it
sometimes grows outside
of the macrosporangium
and becomes green), and
derives its nourishment
through it from the sporo-
phyte, to which the latter
remains organically con-
nected. This condition
of the female prothallium
of the gymnosperms
necessitated a special
adaptation of the male
Pr<>thallium in order that
the sperm cells may reach
and fertilize the egg cell.

Fig. 2

Gingko biloba. A, mature pollen grain; /?, germinating
pollen grain, the branched tube entering among the cells
of the nucellus; Ex, exine (qjjter wall of spore); Plt pro-
thallial cell ; T^, antheridial cell (divides later to form stalk
cell and generative cell) ; f\, vegetative cell ; l^a, vacuoles ;
Nc, nucellus. (After drawings by Hirase and Ikeno.)

Fig. 287.

Gingko biloba, diagrammatic representation of the relation of pollen tube to the arche-
gonium in the end of the nucellus. pt, pollen tube ; 0, archegonium. (After drawing by
Hirase and Ikeno.)

437. Gymnosperms are naked seed plants. — The pine, as we have seen,
has naked seeds. That is, the seeds are not enclosed within the carpel, but

FURTHER STUDIES ON GYMNOSPERMS.

2I9

are exposed on the outer surface. All the plants of the great group to

which the pine belongs have

naked seeds. For this reason

the name " gymnosperms "

has been given to this great

group.

438. Classification of gymno-
sperms.— The gingko tree has
until recently been placed with
the pines, yew, etc., in the class
conifers, but the discovery of
the spermatozoids in the pollen
tube suggests that it is not
closely allied with the coniferae,
and that it represents a class
coordinate with them. Engler arranges the living gymnosperms as follows :

Fig. 2

Spermatozoids of
zamia in pollen tube
PSi pollen grain; a, a,
spermatozoids. (After
Webber.)

Fig. 289.
Spermatozoidof zamia
showing spiral row of
cilia. (After Webber.)

Class I. Cycadales ; family Cycadacese. Cycas, zamia, etc.
Class 2. Gingkoales ; family Gingkoaceae. Gingko.

Class 3. Coniferse ; family I. Taxaceae. Taxus, the common yew in the
eastern United States, and Torreya, in the
western United States, are examples,
family 2. Pinaceas. Araucaria (redwood of California),

firs, spruces, pines, cedars, cypress, etc.

Class 4. Gnetales. Welwitschia mirabilis, deserts of southwest Africa ;
Ephedra, deserts of the Mediterranean and of West
Asia. Gnetum, climbers (Lianas), from tropical Asia
and America.

22O

MORPHOLOG Y.

H

2

w

s
P

W

s

•<
O

C

x

M

s

p^
c

x
O

C/2

W

3

CHAPTER XXXIII.

MORPHOLOGY OF THE ANGIOSPERMS : TRILLIUM;
DENTARIA.

Trillium.

440. General appearance. — As one of the plants to illustrate
this group we may take the wake-robin, as it is sometimes called,
or trillium. There are several species of this genus in the
United States; the commonest one in the eastern part is the
"white wake-robin" (Trillium grandiflorum). This occurs in
or near the woods. A picture of the plant is shown in fig. 290.
There is a thick, fleshy, underground stem, or rhizome as it is
usually called. This rhizome is perennial, and is marked by
ridges and scars. The roots are quite stout and possess coarse
wrinkles. From the growing end of the rhizome each year the
leafy, flowering stem arises. This is 20-30^ (8-12 inches) in
height. Near the upper end is a whorl of three ovate leaves,
and from the center of this rosette rises the flower stalk, bearing
the flower at its summit.

441. Parts of the flower. Calyx. — Now if we examine the
flower we will see that there are several leaf-like structures.
These are arranged also in threes just as are the leaves. First
there is a whorl of three, pointed, lanceolate, green, leaf-like
members, which make up the calyx in the higher plants, and the
parts of the calyx are sepals, that is, each leaf-like member is a
sepal But while the sepals are part of the flower, so called, we
easily recognize them as belonging to the leaf series.

221

222 MOKPHOLOG Y.

442. Corolla. — Next above the calyx is a whorl of white or

VI

pinkish members, in
are also leaf-like in form,
being usually somewhat
make up what is the
and each member of the
they are parts of the
their form and posi-
also belong to the leaf
443. Androecium. —
tion of the corolla is
of members which do not
form. They are known
As seen in fig. 291 each
ament), and extending
greater part of the length
side. This part of the
ridges form the anther
Soon after the flower is
ther sacs open also by a
along the edge of the
time we see quantities of
or dust escaping from the

Trillium grandiflorum, which
and broader than the sepals,
broader at the free end. These
corolla in the higher plants,
corolla is a petal. But while
flower, and are not green,
tion would suggest that they
series.

Within and above the inser-
found another tier, or whorl,
at first sight resemble leaves in
in the higher plants as stamens.
stamen possesses a stalk ( = fil-
along on either side for the
are four ridges, two on each
stamen is the anther, and the
sacs, or lobes,
opened, these an-
split in the wall
ridge. At this
Fig 29o yellowish powder

Trillium grandiflorum. ruptured anther

locules. If we place some of this under the microscope we see

ANGIOSPERMS: TRILLIUM.

223

that it is made up of minute bodies which resemble spores ; they
are rounded in form, and the outer wall is spiny. They are in fact

spores,

the

microspores

of the trillium, and here,
as in the gymnosperms,
are better known as pollen.

Fig. 291.

Sepal, petal, stamen, and pistil of Trillium
grandiflorum.

444. The stamen a sporo-
phyll. — Since these pollen
grains are the spores, we would
infer, from what we have
learned of the ferns and gym-
nosperms, that this member of

the flower which bears them is a sporophyll ;

and this is the case. It is in fact what is called

the microsporophyll. Then we see also that the

anther sacs, since they enclose the spores, would

be the sporangia (microsporangia). From

it is now quite clear that the stamens

belong also to the leaf series. They

are just six in number, twice the number

found in a whorl of leaves, or sepals,

or corolla. It is believed, therefore,

that there are two whorls of stamens in the flower of trillium.

445. Gynoecium. — Next above the stamens and at the center
of the flower is a stout, angular, ovate body which terminates in
three long, slender, curved points. This is the pistil, and at

Trillium gran-
diflorum, with
the compound
pistil expanded
into three leaf-
like members.
At the right
these three are
shown in detail.

224

MOKPHOLOG Y.

present the only suggestion which it gives of belonging to the
leaf series is the fact that the end is divided into three parts, the
number of parts in each successive whorl of members of the
flower. If we cut across the body of this pistil and examine it
with a low power we see that there are three chambers or cavi-
ties, and at the junction of each
the walls suggest to us that this
body may have been formed by the
infolding of the margins of three
leaf-like members, the places of
contact having then become grown
together. We see also that from
the incurved
margins of each
division of the
pistil there stand

out in the cavity oval bodies.
These are the ovules. Now the
ovules we have learned from our
study of the gymnosperms are the
sporangia (here the macrosporangia).
It is now more evident that this curious body, the pistil, is made up
of three leaf-like members which have fused together, each mem-
ber being the equivalent of a sporophyll (here the macrosporo-
phyll). This must be a fascinating observation, that
'plants of such widely different groups and of such
different grades of complexity should have members
formed on the same plan and belonging to the same
series of members, devoted to similar functions, and
yet carried out with such great modifications that at
first we do not see this common meeting ground
Fig 294. which a comparative study brings out so clearly.
sta!nrenSo°frTriid 446. Transformations of the flower oftrillium.-
antherSlioSinef If anything more were needed to make it clear that
on the margin. the ^arts of the flower of trillium belong to the leaf

series we could obtain evidence from the transformations which

ANGIOSPERMS: DENT ARIA. 22$

the flower of trillium sometimes presents. In fig. 293 is a sketch
of a flower of trillium, made from a photograph. One set of
the stamens has expanded into petal-like organs, with the anther
sacs on the margin. In fig. 292 is shown a plant of Trillium
grandiflorum in which the pistil has separated into three distinct
and expanded leaf-like structures, all green except portions of
the margin.

Dentaria.

447. General appearance. — For another study we may take
a plant which belongs to another division of the higher plants,
the common "pepper root," or " toothwort " (Dentaria
diphylla) as it is sometimes called. This plant occurs in moist
woods during the month of May, and is well distributed in the
northeastern United States. A plant is shown in fig. 295. It
has a creeping underground rhizome, whitish in color, fleshy,
and with a few scales. Each spring the annual flower-bearing
stem rises from one of the buds of the rhizome, and after the
ripening of the seeds, dies down.

The leaves are situated a little above the middle point of the
stem. They are opposite and the number is two, each one
being divided into three dentate lobes, making what is called a
compound leaf.

448. Parts of the flower. — The flowers are several, and they
are borne on quite long stalks (pedicels) scattered over the ter-
minal portion of the stem. We should now examine the parts
of the flower beginning with the calyx. This we can see, look-
ing at the under side of some of the flowers, possesses four scale-
like sepals, which easily fall away after the opening of the flower.
They do not resemble leaves so much as the sepals of trillium,
but they belong to the leaf series, and there are two pairs in the
set of four. The corolla also possesses four petals, which are more
expanded than the sepals and are whitish in color. The sta-
mens are six in number, one pair lower than the others, and also

226 •;- MORPHOLOGY.

shorter. The filament is long in proportion to the anther, the

latter consisting of two
lobes or sacs, instead of
four as in trillium. The
pistil is composed of two
carpels, or leaves fused
together. So we find in
the case of the pepper
root that the parts of the
flower are in twos, or
multiples of two. Thus
they agree in this respect
with the leaves ; and
while we do not see
such a strong resem-
blance between the
parts of the flower
here and the leaves,
yet from the pres-
ence of the pollen

Fig. 296.

Flower of the toothwort (Dentaria
diphylla).

Fig. 295.
Toothwort (Dentaria diphylla).

ANGIOSPERMS: DENT ART A. 22/

(microspores) in the anther sacs (microsporangia) and of ovules
(macrosporangia) on the margins of each half of the pistil, we
are, from our previous studies, able to recognize here that all the
members of the flower belong to the leaf series.

449. In trillium and in the pepper root we have seen that the
parts of the flower in each apparent whorl are either of the same
number as the leaves in a whorl, or some multiple of that num-
ber. This is true of a large number of other plants, but it is not
true of all. A glance at the spring beauty (Claytonia virginiana,
fig. 349) and at the anemone (or Isopyrum biternatum, fig. 355)
will serve to show that the number of the different members of
the flower may vary. The trillium and the dentaria were selected
as being good examples to study first, to make it very clear that
the members of the flower are fundamentally leaf structures, or
rather that they belong to the same series of members as do the
leaves of the plant.

CHAPTER XXXIV.

GAMETOPHYTE AND SPOROPHYTE OF ANGIO-
SPERMS.

450. Male prothallium of angiosperms. — The first division
which takes place in the nucleus of the pollen grain occurs, in
the case of trillium and many others of the angio-
sperms, before the pollen grain is mature. In the
case of some specimens of T. grandiflorum in
which the pollen was formed during the month
Fi 297 °^ Oct°ber of the year before flowering, the divi-

Neariy mature sion of the nucleus into two nuclei took place

pollen grain of tril-

Hum. The smaller soon after the formation of the four cells from

cell is the genera-

tiveceii. the mother cell. Ihe nucleus divided in the

young pollen grain is shown in fig. 297. After this takes
place the wall of the pollen grain becomes stouter, and minute
spiny projections are formed.

451. The larger cell is the vegetative cell
of the prothallium, while the smaller one, since
it later forms the sperm cells, is the generative
cell. This generative cell then corresponds
to the central cell of the antheridium, and the
vegetative cell perhaps corresponds to a wall
cell of the antheridium. If this is so, then the
male prothallium of angiosperms has become
reduced to a very simple antheridium. The
farther growth takes place after fertilization.
In some plants the generative cell divides into "£\; eath'nelr
the two sperm cells at the maturity of the pollen grain,
pollen grain. In other cases the generative cell divides in the pollen tube
after the germination of the pollen grain. For study of the pollen tube the
pollen may be germinated in a weak solution of sugar, or on the cut surface

283

Germinal

general

:d, in other divided
>rm the two sperm

GAMETOPHYTE AND SPOROPHYTE.

229

of pear fruit, the latter being kept in a moist chamber to prevent drying
the surface.

452. In the spring after flowering the pollen escapes from the anther sacs,
and as a result of pollination is brought to rest on the stigma of the pistil.
Here it germinates, as we say, that is it develops a long tube which makes
its way down through the
style, and in through the
micropyle to the embryo sac,
where, in accordance with
what takes place in other
plants examined, one of the
sperm cells unites with the
egg, and fertilization of the
egg is the result.

453. Macrospore and embyro sac.
three pistils or carpels are united into
taria the two carpels are also united
carpel. Simple carpels are found in
example in the ranunculacese, the
bine, etc. These simple carpels bear a

Fig. 299.

Section of pistil of trillium, Fig- 300.

showing position of ovules Mandrake (Podo
(macrosporangia*. phyllum peltatum).

— In trillium the
one, and in den-
into one compound
many plants, for
buttercups, colum-
greater resemblance
to a leaf, the mar-
gins of which are
folded around so
that they meet and
enclose the ovules
or sporangia.

454. If we cut
across the com-
pound pistil of tril-
lium we find that
the infoldingsof the
three pistils meet to
form three partial
partitions which
extend nearly to the center, dividing off three spaces. In
these spaces are the ovules which are attached to the infolded
margins. If we make cross sections of a pistil of the May-

230

MORPHOLOG Y.

apple (podophyllum) and through the ovules when they are
quite young, we will find that the ovule has a structure like that
shown in fig. 301. At m is a cell much larger than the surround-
ing ones. This is the macrospore. The tissue surrounding it
is called here the nucellus, but because it contains the macrospore
it must be the macrosporangium. The two coats or integuments of
the ovule are yet short and have not grown out over the end of
the nucellus. This macrospore increases in size, forming first a
cavity or sac in the nucellus, the embryo sac. The nucleus divides

Fig. 301.

Young ovule (macrosporangium) of podophyllum. n, nucellus containing the one-celled
stage of the macrospore ; i.int, inner integument ; o.int, outer integument.

several times until eight are formed, four in the micropylar end
of the embryo sac and four in the opposite end. In some plants
it has been found that one nucleus from each group of four
moves toward the middle of the embryo sac. Here they fuse to-
gether to form one nucleus, the endosperm nucleus or definitive
nucleus shown in fig. 302. One of the nuclei at the micropylar
end is the egg, while the t Vo smaller ones nearer the end are the

GAMETOPHYTE AND SPOROPHYTE.

231

synergids. The egg cell is all that remains of the archegonium
in this reduced prothallium. The three nuclei at the lower end
are the antipodal cells.

Fig. 302.

ynergids and egg at

Podophyllum peltatum, ovule containing mature embryo sac ; two s
left, endosperm nucleus in center, three antipodal cells at right.

455. Embryo sac is the young female prothallium. — In

figures 303, 305 are shown the different stages in the develop-
ment of the embryo sac in lilium.
The embryo sac at this stage is
the young female prothallium, and
the egg is the only remnant of the
female sexual organ, the arche-
gonium, in this reduced gameto-
phyte.

456. Fertilization. — Before
fertilization can take place the /
pollen must be conveyed from
the anther to the stigma. (For

the different methods of pollination see Part III.) When the
pollen tube has reached the embryo sac, it opens and the sperm
cell is emptied into the embryo sac near the egg. The sperm
nucleus now enters the protoplasm surrounding the egg nucleus.
The male nucleus is usually smaller than the female nucleus, and
sometimes, as in the cotton plant, it grows to near or quite the

Fig. 303-
Macrospore (one-celled stage) of lilium.

232

MORPHOLOGY.

size of the female nucleus before the fusion of the two takes place.
In figs. 306 and 307 are shown the entering pollen tube with
the sperm nucleus, and the fusion of the male and female nuclei.
457. Fertilization in plants is fundamentally the same as
in animals. — In all the great groups of plants as represented by
spirogyra, cedogonium, vaucheria, peronospora, ferns, gymno-

Fig. 304.

Two- and four-celled stage of embryo-sac of lilium. The middle one shows division of
nuclei to form the four-celled stage. (Easter lily.)

sperms, and in the angiosperms, fertilization, as we have seen,
consists in the fusion of a male nucleus with a female nucleus.
Fertilization, then, in plants is identical with that which takes
place in animals.

458. Embryo. — After fertilization the egg develops into a
short row of cells, the suspensor of the embryo. At the free end
the embyro develops. In figs. 309 and 310 is a young embryo
of trillium.

459. Endosperm, the mature female prothallium. — During
the development of the embryo the endosperm nucleus divides

GAMEl^OPHYTE AND SPOROPHYTE.

233

into a great many nuclei in a mass of protoplasm, and cell walls
are formed separating them into cells. This mass of cells is the
endosperm, and it surrounds the
embryo. It is the mature female
prothallium, belated in its growth
in the angios perms, usually de-
veloping only when fertilization
takes place, and its use has been
assured.

460. Seed. — As the embryo

-pn

Fig. 305.

Mature embryo sac (young pro-
thallium) of lilium. in, micropylar

end; -S, synergids; /•-', egg; >«, , _,.___„._,

polar nuclei; Ant, antipodals. the end. (Duggar.)
(Easter lily.)

Fig. 306.

Section through nucellus and upper part of embryo
sac of cotton at time of entrance of pc.llen tube. £,
egg; A', synergids; P, pollen tube with sperm cell in

234

MORPHOLOG Y.

is developing it derives its nourishment from the endosperm (or
in some cases perhaps from the nucellus). At the same time

Fertilization of cotton, pt,
pollen tube ; Sn, synergids ; £,
u egg, with male and female nu-

cleus fusing. (Duggar.)

the integuments increase
in extent and harden as
the seed is formed.

461. Perisperm. — In
most plants the nucellus is av
all consumed in the devel-
opment of the endosperm,
so that only minute frag-
ments of disorganized cell
walls remain next the in-
ner integument. In some
plants, however, (the water-
lily family, the pepper Fig. 308.

' J Diagrammatic section of ovary and ovule at time

family, etc. , ) a portion Of of fertilization in angiosperm. /, funicle of ovule ;

«, nucellus; m, micropyle ; f>, antipodal cells of
the nucellus remains in- embryo jsac ; e, endosperm nucleus ; X-egg cell and

synergids ; az, outer integument of ovule ; zz, inner
tact in the mature Seed, integument. The track of the pollen tube is shown

down through the style, walls of the ovary to the
In SUCh Seeds the remain- micropylar end of the embryo sac.

ing portion of the nucellus is the perisperm.

462. Presence or absence of endosperm in the seed. — In

many of the angiosperms all of the endosperm is consumed by
the embryo during its growth in the formation of the seed. This
is the case in the rose family, crucifers, composites, willows, oaks,
legumes, etc., as in the acorn, the bean, pea and others. In
some, as in the bean, a large part of the nutrient substance pass-

GAMETOPHYTE AND SPOROPHYTE.

235

ing from the endosperm into the embryo is stored in the cotyle-
dons for use during germination. In other plants the endosperm

Fig. 309. Fig. 310.

Section of one end of ovule of trillium, showing Embryo e n -

young embryo in endosperm. larged.

is not all consumed by the time the seed is mature. Examples of
this kind are found in the buttercup family, the violet, lily, palm,

Fig. 3*'-

Seed of violet, external view, and
section. The section shows the embryo
lying in the endosperm.

PC

Fig. 312.

Section of fruit of pepper (Piper
nigrum), showing small embryo lying
in a small quantity of whitish endo-
sperm at one end, the perisperm oc-
cupying the larger part of the interior,
surrounded by pericarp.

jack-in-the-pulpit, etc. Here the remaining endosperm in the
seed is used as food by the embryo during germination.

463. Sporophyte is prominent and highly developed. — In the angiosperms
then, as we have seen from the plants already studied, the trillium, dentaria,

MORPHOLOGY.

etc., are sporophytes, that is they represent the spore-bearing, or sporophytic,
stage. Just as we found in the case of the gymnosperms and ferns, this stage
is the prominent one, and the one by which we characterize and recognize the
plant. We see also that the plants of this group are still more highly special-
ized and complex than the gymnosperms, just as they were more specialized
and complex than the members of the fern group. From the very simple
condition in which we possibly find the sporophyte in some of the algae like
spirogyra, vaucheria, and coleochsete, there has been a gradual increase in
size, specialization of parts, and complexity of structure through the bryo-
phytes, pteridophytes, and gymnosperms, up to the highest types of plant
structure found in the angiosperms. Not only do we find that these changes
have taken place, but we see that, from a condition of complete dependence of
the spore-bearing stage on the sexual stage (gametophyte), as we find it in the
liverworts and mosses, it first becomes free from the gametophyte in the mem-
bers of the fern group, and is here able to lead an independent existence.
The sporophyte, then, might be regarded as the modern phase of plant life,
since it is that which has become and remains the prominent one in later
times.

464. The gametophyte once prominent has become degenerate. — On the
other hand we can see that just as remarkable changes have cotne upon the
other phase of plunt life, the sexual stage, or gametophyte. There is reason
to believe that the gametophyte was the stage of plant life which in early
times existed almost to the exclusion of the sporophyte, since the characteristic
thallus of the algae is better adapted to an aquatic life than is the spore-bearing
state of planto. At least, we now find in the plants of this group as well as in
the liverworts, that the gametophyte is the prominent stage. When we reach the
members of the fern group, and the sporophyte becomes independent, we find
that the gametophyte is decreasing in size, in the higher members of the pteri-
dophytes, the male prothallium consisting of only a few cells, while the fe-
male prothallium completes its development still within the spore wall. And
in selaginella it is entirely dependent on the sporophyte for nourishment.

465. As we pass through the gymnosperms we find that the condition of
things which existed in the bryophytes has been reversed, and the gameto-
phyte is now entirely dependent on the sporophyte for its nourishment, the
female prothallium not even becoming free from the sporangium, which remains
attached to the sporophyte, while the remnant of a male prothallium, during
the stage of its growth, receives nourishment from the tissues of the nucellus
through which it bores its way to the egg-cell.

466. In the angiosperms this gradual degradation of the male and female
prothallia has reached a climax in a one-celled male prothallium with two
sperm-cells, and in the embryo-sac with no clearly recognizable traces of an
archegonium to identify it as a female prothallium. The development of the
endosperm subsequent, in most cases, to fertilization, providing nourishment

GAMETOPHYTE AND SPOROPHYTE.

237

for the sporophytic embryo at one stage or another, is believed to be the last
remnant of the female prothallium in plants.
467. Synopsis of members of the sporophyte in angiosperms.

Higher plant.
Sporophyte phase

(or modern phase). \ j j ^

Foliage leaves.
Perianth leaves.
Spore-bearing leaves

with sporangia.
(Sporangia sometimes

on shoot.)

Flower.

MORPffOLOG Y.

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CHAPTER XXXV.

MORPHOLOGY OF THE NUCLEUS AND SIGNIFI-
CANCE OF GAMETOPHYTE AND SPOROPHYTE.

469. In the development of the spores of the liverworts,
mosses, ferns, and their allies, as well as in the development of
the microspores of the gymnosperms and angiosperms, we have

observed that four spores are formed
from a single mother cell. These

Fig. 313-

Forming spores in mother
cells (Polypodium vulgare).

Fig. 314-

Spores just mature and wall of
mother cell broken (Asplenium bul-
biferum).

mother 'cells are formed as a last division of the fertile
tissue (archesporium) of the sporangium. In ordinary cell di-
vision the nucleus always divides prior to the division of the cell.
In many cases it is directly connected with the laying down of
the dividing cell wall.

470. Direct division of the nucleus. — The nucleus divides in
two different ways. On the one hand the process is very simple.
The nucleus simply fragments, or cuts itself in two. This is
direct division.

471. Indirect division of the nucleus. — On the other hand
very complicated phenomena precede and attend the division of

239 •

240

MORPHOLOG Y.

the nucleus, giving rise to a succession of nuclear figures presented
by a definite but variable series of evolutions on the part of the
nuclear substance. This is indirect division of the nucleus, or
karyokinesis. Indirect division of the nucleus is the usual method,
and it occurs in the normal growth and division of the cell. The
nuclear figures which are formed in the division of the mother
cell into the four spores are somewhat different from those
occurring in vegetative division, but their study will serve to show
the general character of the process.

472. Chromatin and linin of the nucleus. — In figure 315
is represented a pollen mother cell of the May-apple (podophyl-

Fig. 315. Fig. 316. Fig. 317.

Pollen mother cell Spirem stage of nucleus. Forming spindle,

of podophyllum, rest- nu, nuclear cavity ; n, nu- threads from proto-

ing nucleus. Chroma- cleolus ; Sp, spirem. plasm with several

tin forming a net- poles, roping the

work. chromosomes up to

(Figures 315-317 after Mottier.) nuclear plate.

lum). The nucleus is in the resting stage. There is a network
consisting of very delicate threads, the linin network. Upon
this network are numerous small granules, and at the junction of
the threads are distinct knots. The nucleolus is quite large and
prominent. The numerous small granules upon the linin stain
very deeply when treated with certain dyes used in differentiating
the nuclear structure. This deeply staining substance is the
chroma/in of the nucleus.

GAMETOPHYl^E AND SPOROPHYTE.

24I

473. The chromatin skein. — One of the first nuclear figures
in the preparatory stages of division is the chromatin skein or
spirem. The chromatin substance unites to form this. The
spirem is in the form of a narrow continuous ribbon, or band,
woven into an irregular skein, or gnarl, as shown in figure 316.
This band splits longitudinally into two narrow ones, and then
each divides into a definite number of segments, about eight in
the case of podophyllum. Sometimes the longitudinal splitting of
the band appears to take place after the separation into the chro-
matin segments. The segments remain in pairs until they separate
at the nuclear plate.

474. Chromosomes, nuclear plate, and nuclear spindle.—
Each one of these rod-like chromatin segments is a chromosome.

Fig. 318.

Karyokinesis in pollen mother cells of podophyllum. At the left the spindle with the
chromosomes separating at the nuclear plate ; in the middle figure the chromosomes have
reached the poles of the spindle, and at the right the chromosomes are forming the daughter
nuclei. (After Mottier.)

The pairs of chromosomes arrange themselves in a median plane
of the nucleus, radiating somewhat in a stellate fashion, forming
the nuclear plate, or monaster. At the same time threads of the
protoplasm (kinoplasm) become arranged in the form of a spindle,
the axis of which is perpendicular to the nuclear plate of chromo-
somes, as shown in figure 318, at left. Each pair of chromosomes
now separate in the line of the division of the original spirem,
one chromosome of each pair going to one pole of the spindle,

242

MORPHOLOG Y.

while the other chromosome of each pair goes to the opposite
pole. The chromosomes here unite to form the daughter nuclei.

Each of these nuclei now
divide as shown in figure

W$& ^i?\ M&!\ 320 (whether the chromo-

somes in this second divi-
nH "'lUf sion in the mother cell split
longitudinally or divide
transversely has not been
Fig. 319. definitely settled), and four

Different stages in the separation of divided rmrlf»i arp fnrm^rl in tho
U-shaped chromosomes at the nuclear plate. (After ] LC1C1 aF6 1OrmeCl m tnC

Mottier) in podophyllum. pollen mother cell. The

protoplasm about each one of these four nuclei now surrounds
itself with a wall and the spores are formed.

The number of chromosomes usually the same in a given
species throughout one phase of the plant. — In those plants
which have been carefully studied, the number of chromosomes
in the dividing nucleus has been found to be fairly constant in a
given species, through all the divisions in that stage or phase
of the plant, especially in the embryonic, or young growing
parts. For example, in the
prothallium, or gameto-
phyte, of certain ferns, as
osmunda, the number of
chromosomes in the divid-
ing nucleus is always twelve.
So in the development of
the pollen of lilium from
the mother cells, and in the
divisions of the antherid
cell to form the generative

cells or sperm cells, there

second division of

Fig. 321.
Chromosomes uniting

are always twelve chromo- nuc\e} in pollen mother at pok* to form the

cell oi podophyllum, nuclei of the four spores.
SOmeS SO far as has been chromosomes at poles. (After Mottier.)

found. In the development of the egg of lilium from the
macrospore there are also twelve chromosomes.

GAMETOPHYTE AND SPOROPHYTE.

243

When fertilization takes place the number of chromosomes
is doubled in the embryo. — In the spermatozoid of osmunda
then, as well as in the egg, since these are developed on the game-
tophyte, there are twelve chromosomes each. The same is true
in the sperm-cell (generative cell) of lilium, and also in the egg-
cell. When these nuclei unite, as they do in fertilization, the
paternal nucleus with the maternal nucleus, the number of chro-
mosomes in the fertilized egg, if we take lilium as an example,
is twenty -four instead of twelve; the number is doubled. The
fertilized egg is the beginning of the sporophyte, as we have seen.
Curiously throughout all the divisions of the nucleus in the em-
bryonic tissues of the sporophyte, so far as has been determined,
up to the formation of the mother cells of the spores, the number
of chromosomes is usually the same

475. Reduction of the number of chromosomes in the nu-
cleus.— If there were no reduction in the number of chromosomes

Fig. 322.

Karyokinesis in sporophyte cells of podophyllum (twice the number of chromosomes
here that are found in the dividing spore mother cells).

at any point in the life cycle of plants, the number would thus
become infinitely large. A reduction, however, does take place.

244 MORPHOLOGY.

This usually occurs, either in the mother cell of the spores or in
the divisions of its nucleus, at the time the spores are formed. In
the mother cells a sort of pseudo-reduction is effected by the
chromatin band separating into one half the usual number of nu-
clear segments. So that in lilium during the first division of the
nucleus of the mother cell the chromatin band divides into twelve
segments, instead of twenty-four as it has done throughout the
sporophyte stage. So in podophyllum during the first division in
the mother cell it separates into eight instead of into sixteen.
Whether a qualitative reduction by transverse division of the
spirem band, unaccompanied by a longitudinal splitting, takes
place during the first or second karyokinesis is still in doubt.

476. Significance of karyokinesis and reduction. — The pre-
cision with which the chromatin substance of the nucleus is di-
vided, when in the spirem stage, and later the halves of the
chromosomes are distributed to the daughter nuclei, has led to the
belief that this substance bears the hereditary qualities of the
organism, and that these qualities are thus transmitted with cer-
tainty to the offspring. In reduction not only is the original
number of chromosomes restored, it is believed by some that
there is also a qualitative reduction of the chromatin, i.e. that
each of the four spores possesses different qualitative elements of
the chromatin as a result of the reducing division of the nucleus
during their formation.

The increase in number of chromosomes in the nucleus occurs
with the beginning of the sporophyte, and the numerical reduc-
tion occurs at the beginning of the gametophyte stage. The
full import of karyokinesis and reduction is perhaps not yet
known, but there is little doubt that a profound significance is to
be attached to these interesting phenomena in plant life.

377. The gametophyte may develop directly from the tissue
of the sporophyte. — If portions of the sporophyte of certain of
the mosses, as sections of a growing seta, or of the growing
capsule, be placed on a moist substratum, under favorable condi-
tions some of the external cells will grow directly into protonemal
threads. In some of the ferns, as in the sensitive fern (onoclea),

GAMETOPHYTE AND SPOROPHYTE.

245

when the fertile leaves are expanding into the sterile ones, proto-
nemal outgrowths occur among the aborted sporangia on the
leaves of the sporophyte. Similar rudimentary protonemal
growths sometimes occur on the leaves of the common brake
(pteris) among the sporangia, and some of the rudimentary spo-
rangia become changed into the protonema. In some other
ferns, as in asplenium(A. nlix-foemina, var. clarissima), prothallia
are borne among the aborted sporangia, which bear antheridia
and archegonia. In these cases the gametophyte develops from
the tissue of the sporophyte without the intervention or necessity
of the spores. This is apospory.

478. The sporophyte may develop directly from the tissue
of the gametophyte. — In some of the ferns, Pteris cretica for
example, the embryo fern sporophyte arises directly from the tissue
of the prothallium, without

the intervention of sexual
organs, and in some cases
no sexual organs are de-
veloped on such prothallia.
Sexual organs, then, and
the fusion of the spermato-
zoid and egg nucleus are
not here necessary for the
development of the spo-
rophyte. This is apogamy.
Apogamy occurs in some
other species of ferns, and
in other groups of plants as well, though it is in general a rare
occurrence except in certain species, where it may be the general
rule.

479. Perhaps there is not a fundamental difference between
gametophyte and sporophyte. — This development of sporo-
phyte, or leafy-stemmed plant of the fern, from the tissue of the
gametophyte is taken by some to indicate that there is not such a
great difference between the gametophyte and sporophyte of plants
as others contend. In accordance with this view it has been

Fig. 323-
Apogamy in Pteris cretica.

246 MORPHOL OGY.

suggested that the leafy-stemmed moss plant, as well as the leafy-
stem of the liverworts, is homologous with the sporophyte or
leafy stem of the fern plant; that it arises by budding from the
protenema; and that the sexual organs are borne then on the
sporophyte.

LESSONS ON PLANT FAMILIES.

CHAPTER XXXVI.

RELATIONSHIPS SHOWN BY FLOWER AND FRUIT.

480. Importance of the flower in showing kinships among
the higher plants. — In the seed-bearing plants which we are now
studying \ve cannot fail to be impressed with the general pres-
ence of what is called the flower, and that the flower has its culmi-
nating series in the spore-bearing members of the plant (stamens
and carpels). Aside from the very interesting comparison of the
changes which have taken place in passing from the simple and
generalized sporophyte of the liverworts and mosses to the com-
plex and specialized sporophyte of the higher plants, we should
now seek to interpret the various kinds of aggregations of the
spore-bearing members, here termed stamens and carpels. In
the part of the book which deals with ecology we shall see how
the grouping of these members of the plant is an advantage to it
in the performance of those functions necessary for fruition.

481. While the spore-bearing members, as well as the floral
envelopes, are thus grouped into " flowers," there is a great
diversity in the number, arrangement, and interrelation of these
members, as is suggested by our study of trillium and dentaria.
And a farther examination of the flowers of different plants would
reveal a surprising variety of plans. Nevertheless, if we com-
pare the flower of trillium with that of a lily for example, or the
flower 01 dentaria with that of the bitter-cress (cardamine), we
shall at once be struck with the similarity in the plan of the

24?

248 MORPHO LOGY.

flower, and in the number and arrangement of its members.
This suggests to us that there may be some kinship, or rela-
tionship between the lily and trillium, and between the bitter-
cress and toothwort. In fact it is through the interpretation of
these different plans that we are able to read in the book of
nature of the relationship of these plants. As we found in the
case of the ferns that the most important characters of rela-
tionship among genera and species are found among the spore-
bearing leaves, so here the characters pertaining to the stamens
and carpels are the principal guide posts, though the floral en-
velopes are only second in importance, and leaves also frequently
demand attention.

Bearing these facts in mind, we can inquire of the plants
themselves about some of the attributes of their families and
tribes.

NOTE FOR REFERENCE.

482. Arrangement of flowers. — The arrangement of the flowers (inflores-
cence) on the stem is important in showing kinships. The flowers may be
scattered and distant from each other on the plant, or they may be crowded
close together in spikes, catkins, heads, etc. Many of the flower arrangements
are dependent on the manner of the branching of the stem. Some of the
systems of branching are as follows:

483. I. DICHOTOMOUS BRANCHING. — True dichotomy (forking) does not
occur in the shoots of flowering plants, but it does occur in some of the flower
clusters.

484. II. LATERAL BRANCHING. — Two main types.

Monopodial branching. — This occurs where the main shoot continues to
grow more vigorously than the lateral branches which arise in succes-
sion around the main stem. Examples in shoots, horse-chestnut, pines
(see chapter on pine). Examples in flower clusters (from indetermi-
nate inflorescence).
Raceme; lateral axes unbranched, youngest flowers near the terminal

portion of long main axis; ex. choke-cherry, currant, etc.
Spike; main axis long, lateral unbranched axes with sessile and often
crowded flowers; ex. plantain. Where the main axis is fleshy the
spike forms a spadix, as in skunk's cabbage, Indian turnip, etc.; if
the spike falls away after maturity of the flower or fruit it is a cat-
kin or ament (willows, oaks, etc.).

LESSONS ON PL AN T FAMILIES. 249

Umbel; the main axis is shortened, and the stalked flowers appear to

form terminal clusters or whorls, as in the parsley, carrot, parsnip,

etc.
Head, or capitulum; the main axis is shortened and broadened, and

bears sessile flowers, as in the sunflower, button-bush, etc.
Panicle; when the raceme has the lateral axes branched it forms a

panicle, as in the oat. When the panicle is flattened it forms a

corymb.

Sympodial branching or cymose branching. — The branches, or lateral
axes, grow more vigorously than the main axis, and form for the
' time false axes (form cymes).

1. Monochasium; only one lateral branch is produced from each rela-
tive or false axis.

Helicoid cyme; when the successive lateral branches always ariseon
the same side of the false axis, as in flower clusters of the forget-
me-not.

Scorpioid cyme; when the lateral branches arise alternately on op-
posite sides of the false axis.

2. Dichasium; each relative, or false, axis produces two branches*
often forming a false dichotomy. Examples in shoots are found in
the lilac, where the shoot appears to have a dichotomous branch-
ing, though it is a false dichotomy.

Forking cyme; flower cluster of chickweed.
j. Pleiochasium; each relative, or false, axis produces more than two

branches.

485. The fruit. — The fruit of the angiosperms varies greatly, and often is
greatly complicated. When the gynoecium is apocarpous (that is when the
carpels are from the first distinct] the ripe carpels are separate, and each is a
fruit. In the syncarpous gyncecium (when the carpels are united) the fruit is
more complicated, and still more so when other parts of the flower than
the gynoecium remain united with it in the fruit.

Pericarp; this is the part of the fruit which envelops the seed, and may
consist of the carpels alone, or of the carpels and the adherent part of
the receptacle, or calyx ; it forms the wall of the fruit.
Endocarp and exocarp. If the pericarp shows two different layers, or
zones, of tissue, the outer is the exocarp, and the inner the endocarp,
as in the cherry, peach, etc.

Mesocarp; where there is an intermediate zone it is the mesocarp.
I. CAPSULE (dry fruits). The capsule has a dry pericarp which opens
(dehisces) at maturity. When the capsule is syncarpous the carpels may
separate along the line of their union with each other longitudinally
(septicidal dehiscence}; or each carpel may split down the middle line

250 MORPHOLOGY.

(loculiddal dehiscence] as in fruit of iris; or the carpels may open by

pores (poricidal dehiscence], as in the poppy.

Follicle; a capsule with a single carpel which dehisces along the ventral,

or upper, suture (larkspur, peony}.
Legume or pod; a capsule with a single carpel which dehisces along both

sutures (pea, bean, etc.).
Silique; a capsule of two carpels, which separate at maturity, leaving

the partition wall persistent (toothwort, shepherd's-purse, and most

others of the mustard family); when short it is a silicic or pouch.
Pyxidium or pyxis; the capsule opens with a lid (plantain).

II. DRY INDEHISCENT FRUITS; do not dehisce or separate into distinct
carpels.

Nuts; with a dry, hard pericarp.

Caryopsis; with one seed and a dry leathery pericarp (grasses).
Achene; with pericarp adherent to the seed (sunflower and other com-
posites.

III. SCHIZOCARP; a dry, several-loculed fruit, in which the carpels separate
from each other at maturity but do not dehisce (umbelliferse, mallow).

IV. BERRY; endocarp and mesocarp both juicy (grape).

V. POME; mesocarp and outer portion of endocarp soft and juicy, inner
portion of endocarp papery (apple).

VI. DRUPE, OR STONE FRUIT ; endocarp hard and stony, exocarp soft and
generally juicy (cherry, walnut); in the cocoanut the exocarp is soft
and spongy.

CHAPTER XXXVII.

MONOCOTYLEDONS.

Topic I : Monocotyledons with conspicuous petals
(Petaloidese).

LESSON I. LILY FAMILY

CLASSIFICATION.

486. Species. — It is not necessary for one to be a botanist in
order to recognize, during a stroll in the woods where the tril-
lium is flowering, that
there are many individual
plants very like each
other. They may vary
in size, and the parts
may differ a little in
form. When the flowers
first open they are usually
white, and in age they
generally become pinkish. In some in-
dividuals they are pinkish when they
first open. Even with these variations,
which are trifling in comparison with
the points of close agreement, we recog-
nize the individuals to be of the same
kind, just as we recognize
the corn plants grown
from the seed of an ear of *»*
corn as of the same kind.
Individuals of the same
kind, in this sense, form a species. The white wake-robin, then,
is a species.

251

Fig. 324-
Trillium erec-
tum (purple form),
two plants from
one root-stock.

MONO CO 7' Y LE D ONS.

But there are other trilliums which differ greatly from this one.
The purple trillium (T. erectum) shown in fig. 324 is very dif-
ferent from it. So are a number of others. But the purple
trillium is a species. It is made up of individuals variable, yet
very like one another, more so than any one of them is like the
white wake-robin.

487. Genus. — Yet if we study all parts of the plant, the per-
ennial root stock, the annual shoot, and the parts of the flower,
we find a great resemblance. In this respect we find that there
are several species which possess the same general characters.
In other words, there is a relationship between these different
species, a relationship which includes more than the individuals
of one kind. It includes several kinds. Obviously, then, this
is a relationship with broader limits, and of a higher grade,
than that of the individuals of a species. The grade next higher
than species we call genus. Trillium, then, is a genus. Briefly
the characters of the genus trillium are as follows.

488. Genus trillium. — Perianth of six parts : sepals 3, her-
baceous, persistent ; petals colored. Stamens 6 (in two whorls),
anthers opening inward. Ovary 3-loculed, 3-6-angled ; stig-
mas 3, slender, spreading. Herbs with a stout perennial root-
stock with fleshy scale-like leaves, from which the low annual
shoot arises bearing a terminal flower, and 3 large netted-veined
leaves in a whorl.

Note. — In speaking of the genus the present usage is to say
trillium, but two words are usually employed in speaking of the
species, as Trillium grandiflorum, T. erectum, etc.

489. Genus erythronium. — The yellow adder-tongue, or
dog-tooth violet (Erythronium americanum), shown in fig. 325,
is quite different from any species of trillium. It differs more
from any of the species of trillium than they do from each other.
The perianth is of six parts, light yellow, often spotted near the
base. Stamens are 6. The ovary is obovate, tapering at the
base, 3-valved, seeds rather numerous, and the style is elongated.
The flower stem, or scape, arises from a scaly bulb deep in the
soil, and is sheathed by two elliptical-lanceolate, mottled leaves.

PLANT FAMILIES: LtLIACEJE.

253

The smaller plants have no flower and but one leaf, while the
bulb is nearer the
surface. Each year
new bulbs are form-
ed at the end of run-
ners from a parent
bulb. These run-
ners penetrate each
year deeper in the
soil. The deeper
bulbs bear the flow-
er stems.

490. Genus lili-
um. — While the lily
differs from either
the trillium or ery-
thronium, yet we
recognize a rela-
tionship when we
compare the peri-
anth of six colored
parts, the 6 stamens,
and the 3 -sided and Fis- 325-

Adder-tongue (erythronium). At left below pistil, and three

3 - locilled stamens opposite three parts of the perianth. Bulb at the
right.

long
ovary.

491. Family liliaceae. — The relationship between genera, as
between trillium, erythronium, and lilium, brings us to a still
higher order of relationship where the limits are broader than in
the genus. Genera which are thus related make up \hefamily.
In the case of these genera the family has been named after the
lily, and is the lily family, or Liliacece. This grouping of plants
into species, genera, families, etc., according to characters and
relationships is classification y or taxonomy.

The lily family is a large one. Another example is found in
the " Solomon' s-seal," with its elongated, perennial root-stock,
the scars formed by the falling away of each annual shoot resem-

254 MONOCOTYLEDONS.

bling a seal. The onion, smilax, asparagus, lily of the valley,
etc., are members of the lily family. The parts of the flower
are usually in threes, though there is an exception in the genus
Umfolium, where the parts are in twos. A remarkable excep-
tion occurs sometimes in Trillium grandiflorum, where the flower
is abnormal and the parts are in twos.

492. Floral formula. — A formula is sometimes written to show at a glance
the general points of agreement in the flower among the members of a
family or group. The floral formula of the lily family is written as follows :
Calyx 3, Corolla 3, Androecium 6(3-3), Gynoecium 3. The formula may be
abbreviated thus: Ca3,Co3,A3,G3.

493. Adhesion and cohesion. — In the lily family all the sets, or whorls of
parts, are free ; ,that is, no floral set is adherent to another. Farther, the
parts of the calyx, corolla, and androecium are distinct. But the parts of the
gynoecium are coherent, i.e. the three carpels are united into a single com-
pound pistil. In the floral formula this cohesion of the parts of a set is
represented by a small bracket over the figure, as in the gynoecium of the
lily family.

494. Floral diagram. — The relation of the parts of the flower on the axis
are often represented by a diagram, as shown in fig. 326 for the water-
plantain family.

495. Note. — In the following lessons on plant families practical exercises
may be conducted, employing representative plants in the several important

families. Sketches should be made of the form of the
leaves, their relation to the stem ; stipules ; parts of
the flower, and other salient and important characters.
Floral formulas and diagrams may be made. Brief
notes and descriptions, made from the specimens them-
selves and not from the books, should be appended.
The plants chosen here need not be insisted upon, for
others equally good may be found. The studies

Diagram of alisma presented are offered as suggestions to indicate the
flower. (Vines.)

way m which relationships may be detected, and a

familiarity with the characters of the families may be obtained. Several of
these lessons are chosen among the monocotyledons, to which- the lily family
also belongs.

496. Water-plantain family (alismaceae). — If we wish to begin with a
more simple and primitive family, the water-plantain family will serve the
purpose. The common water plantain (Alisma plantago) is an example. It
occurs in ditches and muddy shores of streams and lakes. The flowers are
in a loose panicle and are inconspicuous. The leaves resemble those of the

PLANT FAMILIES: OR CHI DA CE^.

255

plantain, hence the common name of water-plantain. The flower is regular
(all parts of a set are alike), and all the parts are distinct and free. This
represents a simpler and more primitive condition than exists in the lily
family, where the carpels are united. The floral formula is as follows :
Ca3,Co3,A6,G6 — ao ; i.e. the parts are in threes or multiples of three. The
stamens are in pairs in front of the sepals, and really represent but three sta-
mens, since it is believed each one has divided, thus making three pairs. No
stamens stand in front of the petals in the water plantain, but in the
European genus Biilomus one stamen in addition stands in front of each
sepal.

497. The arrow leaf (genus sagittaria) occurs in wet ground, or on the
margins of streams and ponds. The leaves are very variable, and this seems
to depend to some extent on the depth of the water. Several forms of this
plant are shown in figs. 493—495. The flowers are monoecious or dioecious.

498. The orchid family (orchidaceae). — Among the orchids are found the
most striking departures from the arrangement of the flower which we found
in the simpler monocoty-
ledons. An example of

this is seen in the lady-
slipper (cypripedium,
shown in fig. 464). The
ovary appears to be below
the calyx and corolla. This
is brought about by the
adhesion of the lower part
of the calyx to the wall
of the ovary. The ovary
then is inferior, while
the calyx and corolla are
epigynous. The stamens
are united with the style
by adhesion, two lateral
perfect ones and one upper
imperfect one. The stamens are thus gynandrous. The sepals and petals
are each three in number. One of the petals, the "slipper," is large,
nearly horizontal, and forms the " lip" or " labellum " of the orchid flower.
The labellum is the platform or landing place for the insect in cross polli-
nation (see Part III, Pollination). Above the labellum stands one of the
sepals more showy than the others, the "banner." The two lateral
"strings" of the slipper are the two other petals. The stamens are still
more reduced in some other genera, while in several tropical orchids three
normal stamens are present.

499. There are thus four striking modifications of the orchid flower: 1st,

Fig. 327.

Flower of an orchid (epipactis), the inferior ovary
twisted as in all orchids so as to bring the upper part of
the flower below.

256

MONO CO T YLED ONS.

the flower is irregular (the parts of a set are different in size and shape) ; 2d,
adnation of all parts with the pistil; 3d, reduction and suppression of the
stamens; 4th, the ovary is twisted halfway around so that the posterior side
of the flower becomes anterior. Floral diagrams in fig. 328 show the posi-

Fig. 328.

Diagrams of orchid flowers. A , the usual
type ; />', of cypripedium. (Vines.)

Fig. 329.
Diagram of flower

of canna.

tion of the stamens in two distinct types. The number of orchid species is
very large, and the majority are found in tropical countries.

500. Related to the orchids are the iris family, in which the stigma is ex-
panded into the form of a petal, and the canna family. In the canna the
flower is irregular (see figs. 467, 468) and the ovary is inferior. (See chap-
ter on pollination, Part III, for description of the canna flower.)

CHAPTER XXXVIII.

MONOCOTYLEDONS CONCLUDED.

Topic II : Monocotyledons with flowers on a spadix
(Spadiciflorae).

501. Lesson II. The arum family (araceae). — This family
is well represented by several plants. The skunk's cabbage
(Spathyema fcetida) illustrated in figs. 455—457 is an interest-
ing example. The flowers are closely crowded around a thick
stem axis. Such an arrangement of flowers forms a ' ' spadix. ' '
The spadix is partly enclosed in a large bract, the " spathe"
The sepals and stamens are four in number, and the pistil has a
four-angled style. The corolla is wanting. (See chapter on
pollination, Part III, for farther characters of the flower. )

502. The " jack-in-the-pulpit," also called " Indian turnip "
(Arisaema triphyllum), shown in fig. 458, the water arum (Calla
palustris), and the sweet flag (Acorus calamus) are members of
this family, as also are the callas and caladiums grown in con-
servatories. The parts of several of the species of this family,
especially the corm of the Indian turnip, are very acrid to the
taste. The floral parts are more or less reduced.

503. Related to the arum family are the ''duckweeds."
Among the members of this family are the most diminutive of
the flowering plants, as well as the most reduced floral structures.
(For description and illustration of three of these duckweeds,
see chapter on nutrition in Part III.)

Other related families are the cat-tails and palms. In the
latter the spathe and spadix are of enormous size. The cocoa-
nut is the fruit of the cocoanut palm.

257

258

MONO CO T YLED ONS.

Topic III: Monocotyledons with a glume subtending
the flower (Glumiflorae).

504. Lesson III. Grass family (gramineae). Oat. — As a

representative of the grass family (gramineae) one may take the
oat plant, which is widely cultivated, and also can be grown
readily in gardens, or perhaps in small quantities in greenhouses
in order to have material in a fresh condition for study. Or we
may have recourse to material preserved in alcohol for the dis-

Fig. 330.
Spikelet of

Fig. 331-
One glume re-

Fig. 332.
Flower opened

Fig. 334-
Flower of
Fig. 333- oat, show-

Section show- ingthe upper

oat showing moved showing showing two palets, ing ground plan palet behind,
two glumes. fertile flower. three stamens, and of flower, a, axis, and the two

two lodicules at base
of pistil.

lodicules in
front.

section of the flower. The plants grow usually in stools ; the
stem is cylindrical, and marked by distinct nodes as in the corn
plant. The leaves possess a sheath and blade. The flowers
form a loose head of a type known as a panicle. Each little
cluster as shown in fig. 330 is what is a spikelet, and consists
usually here of one or two fertile flowers below and one or two
undeveloped flowers above. We see that there are several
series of overlapping scales. The two lower ones are "glumes,"

PLANT FAMILIES: GRAMINE^.

259

and because they bear no flower in their axils are empty glumes.
Within these empty glumes and a little higher on the axis of the
spike is seen a boat -shaped body, formed of a scale, the margins
of which are folded around the flowers within, and the edges
inrolled in a peculiar manner when mature. From the back of
this glume is borne usually an awn. If we carefully remove
this scale, the "flower glume," we find that there is another
scale on the opposite (inner) side, and much smaller. This is
the "palet."

505. Next above this we have the flower, and the most prom-
inent part of the flower, as we see, is the short pistil with the two
plume-like styles, and the three stamens at fig. 332. But if we
are careful in the dissection

of the parts we will see, on
looking close below the pistil
on the side of the flowering
glume, that there are two
minute scales (fig. 334).
These are what are termed
the lodicules, considered by
some to be merely bracts,
by others to represent a- pe-
rianth, that is two of the
sepals, the third sepal hav-
ing entirely aborted. Ru-
diments of this third sepal Fis- 335-

.. , Diagram of oat spikelet. Cl, glumes ; B, palets;

are present in some ot the A, abortive flower,
gramineae.

506. To the gramineae belong also the wheat, barley, corn,
the grasses, etc. The gramineae, while belonging to the class
monocotyledons, are less closely allied to the other families of
the class than these families are to each other. For this reason
they are regarded as a very natural group.

507. The sedge family (cyperaceae). Carex. — As a representative of the
sedges a species of the genus carex may be studied. If plants of Carex
lupulina are taken from the soil carefully we will find that there is an under-

26o

MONO CO T YLED ONS.

ground stem or root-stock which each year grows a few inches, forms new
attachments by roots to the soil, and thus the plant may spread from year
to year. This underground stem, as seen, has only scaly leaves. The
upright stems reach a height of two to three feet, and are prominently

three-angled, as are most of
the species of this large genus.
The leaves are three-ranked,
and consist of a long sheathing
base and a long narrow blade.
The flowers, as we see, are
clustered at the end of the
stem, or sometimes additional
ones arise in the axils of the
leaves lower down on the stem.
The staminate flowers form a
slender, short spike, terminat-
ing the stem, while the pistil-

late flowers
spikes arising

form several
as branches.

Fig. 336.

Flowers of Carex lupulina; staminate flower spike above, three
pistillate flower spikes below. Details of pistillate and staminate
flowers shown at the right.

The flowers are very much reduced here, and each of the pistillate flowers
consists of one pistil which is surrounded by a flask-shaped scale, the/m-
gynium. These perigynia can be distinctly seen upon the spike. At the
apex of the perigynia the three styles emerge. Just below each perigynium

PLANT FAMILIES: CYPERACE&.

26l

is a slender scale, the primary bract, from the axil of which the pistillate
flower arises.

Fig. 337-
Two carex flowers.

Fig. 338.
Pistil of carex.

Fig. 339-
Section of pistil.

For the study of the flowers one must select material at the time the male
flowers are in bloom. In fig. 340 is represented a portion of the staminate
spike of Carex laxiflora. As
seen here each staminate flower
consists of three stamens. These
stamens arise in the axil of a
bract. Figure 337 represents
a portion of the pistillate spike
of the same species at the time
of flowering. The fact that the
parts, or members, of the flower
are in threes suggests that there
may be some relationship be-
tween the carex and the monoco-
tyledons already studied, even
though each flower has become
so reduced in the number of its
members.

508. In the bulrush (scirpus),
another genus of this family, the

flowers are perfect and complete Fig. 340.

(having all parts of the flower), Two male flowers of Carex laxiflora-

with the parts in threes or some multiple of three. Here there is a more
obvious resemblance to the monocotyledenous type.

CHAPTER XXXIX.

DICOTYLEDONS.

Topic IV: Dicotyledons with distinct petals, flowers
in catkins, or aments ; often degenerate.

509. Lesson IV. The willow family (salicaceae).— The wil-
lows represent a very interesting group of plants in which the

Fig- 34
Spray of willow leaves, pistillate and staminate catkins (Salix discolor).

flowers are greatly reduced. The flowers are crowded on a
more or less elongated axis forming a catkin, or ament. The
ament is characteristic of several other families also. The
willows are dioecious, the male and female catkins being borne

262

PLANT FAMILIES : CUPULIFER&. 263

on different plants. The catkins appear like great masses of
either stamens or pistils. But if we dissect off several of the
flowers from the axis, we find that there are many flowers, each
one subtended by a small bract. In the male or " sterile " cat-
kins the flower consists of two to eight stamens, while in the
female or "fertile " catkins the flower consists of a single pistil.
The poplars and willows make up the willow family.

510. Lesson V. The oak family (cupuliferse). — A small
branch of the red oak (Quercus rubra^ is illustrated in fig. 342.

Fig. 342-

Spray of oak leaves and flowers. Below at right is staminate flower, at left pistillate
flower.

This is one of the rarer oaks, and is difficult for the beginner to
distinguish from the scarlet oak. The white oak is perhaps in

264

DICOTYLEDONS.

some localities a more convenient species to study. But for the
general description here the red oak will serve the purpose. Just

as the leaves are expand-
ing in the spring, the deli-
cate sprays
of pendulous
male catkins
form beauti-
ful objects.
The petals
are wanting
in the flower,
and the sepals
form a united

Fig. 343-

Branch of the butter-
nut. Cluster of female
flowers at the top, show-
ing the two styles of each
pistil, catkins below.

calyx, with several lobes, that is, the parts of the

calyx are coherent. In the male flowers the calyx

is bell -shaped and deeply lobed. The pendent

stamens, variable in number, just reach below its

margin. The pistillate or female flowers are not

borne in catkins, but stand on short stalks, either singly or a few

in a cluster. The calyx here is urn-shaped with short lobes.

The ovary consists of three united (coherent) carpels, and there

are three stigmas. Only one seed is developed in the ovary,

and the fruit is an acorn. The numerous scales at the base of

the ovary form a scaly involucre, the cup.

511. The beech, chestnut, and oak are members of the oak
family.

512. The following additional families among the ament
bearers are represented in this country : the birch family (birch,
alder), the hazelnut family (hazelnut, hornbeam, etc.), walnut
family (hickory, walnut), and the sweet-gale family (niyrica).

CHAPTER XL.

DICOTYLEDONS CONTINUED.

Topic V:

Dicotyledons with distinct petals and
hypogynous flowers.

URTICIFLORyE.

513. The nettle family (urticaceee). — The nettle family receives its name
from the members of one genus in which the stinging nettles are found
(urtica). The dioecious nettle (U. dioica) has opposite, petioled leaves,
which are ovate, with a heart-shaped base. The margins of the leaves are

Fig. 345-

Urtica, diagram of
male flower.

Fig. 344-

The dioecious nettle (Urtica dioica),
showing leaves, flower clusters, and
below staminate flower at the right
and pistillate flower at left.

Fig. 346.

Urtica, diagram of
female flower.

deeply serrate, and the lower surface is downy. The stems and petioles of
the leaves are armed with stinging hairs.

514. The greenish flowers are borne in dense clusters in the form of
branched racemes which arise from the axils of the leaves. The staminate

265

266

DICOTYLEDONS.

flowers have four small sepals and four stamens. The fertile flowers (pistil-
late) have also four sepals. The pistil has a two-loculed ovary; one of the
locules is the smaller, and later disappears, so that the fruit is a one-seeded
achene. The parts of the flower are in twos, since the four sepals are in two
pairs.

515. Lesson VI. The elm family (ulmaceae). — The elm tree
belongs to this family. The leaves of our American elm (Ulmus
americana) are ovate, pointed, deeply serrate, and with an ob-
lique base as shown in fig. 347. The narrow stipules which are

Fig- 347-

Spray of leaves and flowers of the American elm ; at the left above is section of flower,
next is winged seed (a samara).

present when the leaves first come from the bud soon fall away.
The flowers are in lateral clusters, which arise from the axils of
the leaves, and appear in the spring before the leaves. They
hang by long pedicels, and the petals are absent. The calyx is
bell-shaped, and 4-9-cleft on the margin. The stamens vary also
in number in about the same proportion. A section of the
flower in fig. 347 shows the arrangement of the parts, the ovary
in the center. The ovary has either one or two locules, and two
styles. The mature fruit has one locule, and is margined with
two winged expansions as shown in the figure. This kind of
a seed is a samara.

PLANT FAMILIES: POLYCONLFLORJS.

267

POLYGONIFLORy€.

516. Buckwheat family (polygonaceae). — Besides the common buckwheat,
from which this
family gets i t s
name, the knot-
weeds are good
representatives.
Fig. 348 is of the
arrow-leaved knot-
weed, or arrow-
leaved tear-thumb,
so called because
of the arrow-shaped
leaves and from the
prominent recurved
prickles on the four-
angled stem. The
plant occurs in low
grounds often i n
large clumps, and
the slender branch-
ed stem is support-
ed to some extent by
neighboring plants.
The flowers are in

Fig. 348.

Polygonum sagittatum, portion
of plant.

Fig. 349.
Spring beauty (Claytonia virginiana).

268 D ICO T YLED ONS.

oval clusters borne on slender, long peduncles which arise from the axils of
the leaves. Petals are wanting, and the calyx is usually five-parted, with
the margin colored. The stamens are mostly eight, and the styles three on
the compound ovary. There is a single seed developed in the ovary which
in ripening forms a three-angled achene like a buckwheat grain. The
species of dock, and of field, or sheep, sorrel (rumex) also belong to this
family.

CURVEMBRY^E.

517. The purslane family (portulacaceee). — The little spring beauty (Clay-
tonia virginica), shown in fig. 349, is a member of this family. It occurs
in moist places. The stem arises from a deeply buried tuber, and bears,
about midway, two long, narrow, fleshy, thick leaves. The upper part of
the stem bears a raceme of pretty rose -colored flowers. The sepals are two.
The petals are five in number, and the stamens of the same number are
inserted on little claws at the base of the petals. The ovary has a long
style, three-cleft at the apex, and in fruit it forms a three-valved pod. The
ovule in claytonia and other members of the family is curved, and conse-
quently the embryo is curved.

518. In some other related families, like the goosefoot family, the embryo

Fig- 35°.
Curved embryos of Russian thistle (Salsola soda). (Warming.)

is also curved. In fig. 350 is shown the embryo of the Russian thistle
(Salsola kali), a member of this family.

POLYCARPIC>€.

519. Lesson VII. The crowfoot family (ranunculaceae). —

The marsh-marigold (Caltha palustris) is a member of this family.
The leaves are heart-shaped or kidney-shaped, and the edge is
crenate. The bright golden -yellow flowers have a single whorl
of petal-like envelopes, and according to custom in such cases
they are called sepals. The number is not definite, varying from

PLANT FAMILIES: RANUNCULACE&.

269

five to nine usually. The stamens are more numerous, as is the

general rule in the members of
the family, but the number of
the pistils is small. Each one is
and forms a little pod
when the seed is ripe. The marsh-
marigold, as its
name implies, oc-
curs in marshy or
wet places and
along the muddy
banks of streams.
It is one of the
common flowers in April and
May.

520. Many of the crowfoots
or buttercups (ranunculus) with
bright yellow flowers grow in
similar situations. The "wood
anemone" (anemone), small
plants with white flowers, and the rue-
anemone (anemonella), which resembles
it, both flower in woods in early spring. The common virgin's
bower (Clematis virginiana) occurs along streams or on hill-
sides, climbing over shrubs or fences.
The vine is somewhat woody. The
leaves are opposite, petioled, and are
composed of three leaflets, which are
ovate, three-lobed, and usually
strongly toothed, and somewhat
heart-shaped at the base. The
flower clusters are borne in the axils
of the leaves, and therefore may also
be opposite. The clusters are much
branched, forming a convex mass of
beautiful whitish flowers. The sepals are colored and the petals

Fig. 35'-

Caltha palustris, marsh-mari
gold.

Fig. 352-

Diagram of marsh marigold
flower.

Fig. 353-
Diagram of aquilegia flower. (Vines.)

270

DICOTYLEDONS.

may be absent, or are very small. The stamens are numerous,

as in the members of the crowfoot family.

The pistils are also numerous, and the

achenes in fruit are tipped with the long

plumose style, which aids them in floating

in the air.

Fig. 354-

Clematis virginiana ; below at right are pis-
tillate and staminate flowers.

355-
Isopyrum biternatum.

521. Some of the characters of the ranunculaceae we recognize
to be the following : The plants are mostly herbs, the petals are
separate, and when the corolla is absent the sepals are colored,
like a corolla. The stamens are numerous, and the pistils are
either numerous or few, but they are always separate from each
other, that is they are not fused into a single pistil (though some-
times there is but one pistil). All the parts of the flower are
separate from each other, and make up successive whorls, the
pistils terminating the series. When the seeds are ripe the fruit
is formed, and may be in the form of a pod, or achene, or in the
form of a berry, as in the baneberry (actaea).

PLANT FAMILIES: RANUNCULACE&.

271

522. The following families are related to the crowfoot family. The water-
lily family, the magnolia family, and the barberry family with the May-apple
as an example (see figure
300). In all there is a
relationship shown by the
separate and usually
numerous carpels. To-
gether they form a large
group, the polycarpicoe.

Fig. 357-
Squirrel-corn (Dicentra canadensis).

RHCEADIN/E.

523. The poppy family (papaveraceae).
— One of the commonest of the members
of this family in the eastern United States
is the bloodroot (Sanguinaria canadensis).
It occurs in open woods in April and May.
It derives its name from the abundant red
juice (latex) in the perennial root-stock.
The low annual shoot bears usually a
single white flower, and one leaf, some-
Details ot times more. The floral formula is as fol-
lows: Ca2,Co8(or io),Aoo .G2.
524. The fumitory family (fumariaceae).— To this family belong the singu-
lar plants, " dutchman's breeches " and " squirrel -corn " (dicentra). They
occur in rich woods in April and May. In the squirrel-corn (D. canaden-
sis) there is a slender underground stem which bears here and there, as shown

Bloodroot (sanguinaria).
flower at left.

2/2

DICOTYLEDONS.

in fig. 357, small yellow tubers resembling grains of corn. The leaves ai£
compound, and the lobes are finely dissected. The flower scape bears a
slender raceme of curious pendulous, greenish-white flowers, sometimes tinged
with rose color. The details are shown in the figure. The stamens are six
in number, arranged in two groups of three (being in two groups they are
diadelphotis).

525. Lesson VIII. The mustard family (cruciferae). — This
is well represented by the toothwort
(dentaria), which we studied in a former
chapter.

These three families (poppy, fumitory,
and mustard) are closely related as shown
by the regular flowers, which are usually in
twos (dimerous) or in fours (tetramerous).

Fig. 358.

Diagram of cruciferous
flower.

GRUINALES.

527. Lesson IX. The gera-
nium family (geraniaceae).

— The wild cranesbill has a
perennial underground root-
stock. From this in the
spring arises the branched,

Branch of cranesbill (Geranium maculatum)
hairy Stem. ihe leaves are showing upper leaves, flowers, and pods.

deeply parted into about five wedge-shaped lobes, which are
again cut. The peduncles bear several purple flowers (fig. 359).
The floral formula is as follows : Ca5,Co5,Aio,G5. The wood-
sorrel (oxalis), the balsam or jewelweed (impatiens), sometimes
called " touch-me-not," are members of the same family.

359-

CHAPTER XLI.
DICOTYLEDONS CONTINUED.

Topic VI : Dicotyledons with distinct petals and

perigynous or epigynous flowers.

Many trees and shrubs.

528. Lesson X. The maple family (aceraceae). — Figure 360
represents a spray of the leaves and flowers of the sugar maple

Fig. 360^.
Spray of leaves and flowers of the sugar maple.

(Acer saccharinum), a large and handsome tree. The leaves are
opposite, somewhat ovate and heart-shaped, with three to five

273

274

DICOTYLEDONS

lobes, which are again notched. The clusters of flowers are pen-
dulous on long hairy pedicels. The petals are wanting. The

Fig. 360.4.

Seeds and flowers of sugar maple. At the right is
a pistillate flower, in the middle a staminate flower,
and at the left the two seeds lorming a samara.

calyx is bell-shaped and several times
lobed, usually five times. The sta-
mens are variable in number. The
ovary is two-lobed and the
deeply forked. The fruit forms
two seeds, each with a long
wing-like expansion as shown
in the figure. The flowers of
the maple are polygamo-dice-
cious, that is the male members (sta-
mens) and female members (carpels)
may be in the same flower or in dif-
ferent flowers.

SAXIFRAGINyC.

529. The saxifrage family (sax-
ifragacese). — The early saxifrage
(Saxifraga virginiensis) is a small
plant io—2$cm high, and grows on
rocky and dry hillsides (fig. 16 1).

Hg. 361.
The OVate Or heart-shaped leaves Early saxifrage (Saxifraga virginiensis).

have crenate margins, and are clustered near the ground. The
scape bears a branched cluster of flowers at the summit. Floral
formula Ca5,Co5,Aio,G2.

PLANT FAMILIES : ROSIFLOR^K.

275

ROSIFLOR/E.

530. Lesson XI. — The rose-like flowers are an interesting and
important group. In all the members the receptacle (the end of
the stem which bears the parts of the flower) is an important part
of the flower. It is most often widened, and either cup-shaped or
urn-shaped, or the center is elevated. The carpels are borne in the
center in the depression, or on the elevated central part where
the receptacle takes on this form. The calyx, corolla, and the
stamens are usually borne on the margin of the widened recep-
tacle, and where this is on the margin of a cup-shaped or urn-
shaped receptacle they

are said to be pengvnous ,
that is, around the gyn-
cecium. The calyx and
corolla are usually in
fives. There are three
families, as follows.

531. The rose, fam-
ily (rosaceae). — In this
family there are five

types, represented by the following plants and illustrations:
ist. In spiraea (fig. 362) the receptacle is cup-shaped. There

are five carpels, united at the
base, but free at the ends.
2d. In the strawberry the re-
ceptacle is conic and bears the
carpels (fig. 363). The conic
receptacle becomes the fleshy
fruit, with the seeds in little pits

r lower of r ragaria vesca with columnar

receptacle t From Warming.) OVCr the Surface. 3d. The rasp-

berries, blackberries, etc., represented here by the flowering
raspberry (Rubus odoratus), fig. 364. 4th. This is represented
by the roses. The receptacle is urn-shaped and constricted

Fig. 362.
lirasa (S
irming.)

Perigynous flower of spirasa (S. lanceolata*
War

(From

276

DICOTYLEDONS.

toward the upper portion,
with the carpels enclosed
in the base (fig. 365).
5th. Here the receptacle is
cup-shaped or bell-shaped
and nearly closed at the
mouth as in the agrimony.

Fig. 364. Fig. 365.

Flowering raspberry (Rubus odoratus). Perigynous flower of rosa, with

contracted receptacle. (From
Warming.)

532. Lesson XII. The almond or plum family (amygdala-
ceae). — The members of this family are trees or shrubs. The
common choke-cherry (fig. 366) will serve to represent one of
the types. The flowers of this species are borne in racemes.
The receptacle is cup-shaped. Only one seed in the single
carpel (sometimes two carpels) matures as the calyx falls away.
The outer portions of the ovary become the fleshy fruit, while
the inner portion becomes the hard stone with the seed in the
center. Such a fruit is a drupe.

The floral formula for this family is as follows:

Ca5,Co5,Ai5-2o or 30, Gi.

533. Lesson XIII. The apple family (pomacese). — This fam-
ily is represented by the apples, pears, quinces, june-berries, haw-
thorns, etc. The members are trees or shrubs. The receptacle is
somewhat cup-shaped and hollow. The perianth and stamens

PLANT FAMILIES: POMACES. 277

are at first perigynous, but become epigynous (upon the gynoe-
cium) by the fusion of the receptacle with the carpels. The floral

Fig. 366.

Choke-cherry (Prunus virginiana). Leaves,
flower raceme, and section of flower at right.

formula is thus Ca5, Co 5, A 10-5-5 or IO~I °-5»Gi-5. The carpels

Fig. 367.
Flower of pear. (After Warming.)

are united, but the styles are free. In fruit the united carpels fuse
more or less with the receptacle.

DICOTYLEDONS.

LEGUMINOSyt.

534. Lesson XIV. The pea family (papilionacese). — This
family is well represented by the common pea. The flower is

Fig. 368.

Details of pea flower; section of flower, perianth removed to show the diadelphous
stamens, one single one, and nine in the other group. (From Warming.)

butterfly-like or papilionaceous, and the showy part is made up of
the five .petals. The petals have received distinct names here
because of the position and form in the
flower. At fig. 369 the petals are separated
and shown in their corresponding posi-
tions, and the names are there given. The
flower is irregular and the parts are in fives,
except the ^carpel, which is single. The
calyx is gamosepalous (coherent), the
corolla polypetalous (distinct). The ten
stamens are in two groups, one separate
stamen and nine united ; they are thus
diadelphous (two brotherhoods). The
fruit forms a pod or legume, and at petals forming"
maturity splits along both edges.

535. There are three families in the legume-bearing plants :
ist, including the locusts, cassias, etc.; 2d, the pea family, in-
cluding peas, beans, clovers, ground-nuts, or peanuts, vetches,
desmodium, etc.; 3d, including the sensitive plants like mimosa.

Fig. 369-
Corolla of pea. S, stand-

ard ;

A', two

PLANT FAMILIES: ONOGRACE&. 2/9

Fig. 370.

Evening primrose (CEnothera. bienms) showing flower buds, flowers, and seed pods.
(From Kenier and Oliver.)

280 DICOTYLEDONS.

Topic VII: Dicotyledons with distinct petals and
epigynous flowers.

MYRTIFLOR^t.

536. Lesson XV. The evening -primrose family (onogra-

ceae). — In the evening primrose (cenothera) the flowers are ar-
ranged in a loose spike along
the end of the stem, each one
situated in the axil of a leaf-
like bract. The flowers of the
family are very characteristic, as
shown here. They are sessile
in the axil of the bract, and the
calyx forms a long tube by the
union of the sepals, only the end
of the tube being divided into
the individual parts, showing
four lobes. On the edge of the
open end of the calyx tube are
seated the four, somewhat heart-
shaped, yellowish petals, and
here are also seated the eight
stamens. The four carpels are
united into a single pistil within
the base of the calyx tube and
united with' it, so that the calyx
tube seems to be on the end of
the pistil. The flowers soon

fade and fall away from the pistil, /*'/ Fig 37I<

and this grows into an elongated jj^F ofllSheni fl°wer

four-angled pod. Since the
lower flowers on the stem are the older, we find nearly mature
fruit and fresh flowers, with all intermediate grades, on the
same plant.

The plants grow by roadsides and in old fields. They are from
locm to a meter or more high (one to five feet). The leaves are

PLANT FAMILIES: ONOGRACE&.

281

lanceolate or oblong, toothed and repand on the margin. In
many of the species of the family the parts of the flower are in

fours as in
variable.

the evening primrose, but in others the number is

UMBELLIFLOR^E.

537. The parsley family (umbelliferee). — The wild carot (Daucus carota) is
common by roadsides and in old fields during August and September. The
leaves are deeply divided and the lobes are notched (pinnately decompound).
The flowers form umbels, since the pedicels are all of about the same length,
and many of them radiate from the same point. In the carrot, and in most of

282 D ICO T YL ED ONS.

the parsley family, the umbel is a compound one, as shown in the illustration.
The calyx is firmly united with the walls of the ovary, which is formed of two
united carpels. The five white petals as well as the five stamens arise from the

Fig. 373-
Single umbel of the wild carrot.

margin of the ovary around the two styles. No portion of the calyx is free in
the wild carrot, though in some other members of the family there are small

Fig. 374- Fig. 375. Fig. 376.

Flower of wild carrot. Section of flower. Seed of wild carrot.

calyx teeth. The fruit is bristly and the surface of the umbel becomes con-
cave in age. The floral formula is as follows: Ca5,Q>5,A5,G2.

The cornel or dogwood family and the aralia family both have the flowers
in umbels, and are thus related to the parsley family.

CHAPTER XLII.

DICOTYLEDONS CONCLUDED.
SYM PETALS.

538. In the remaining families the corolla is gamopetalous,
that is, the petals are coherent into a more or less well-formed
tube, though they may be free at the end. For this reason they
are known as the sympetalce.

Topic VIII: Dicotyledons with united petals, flower
parts in five whorls.

BICORNES.

539. The pyrola family (pyrolaceae). — The shin-leaf or wintergreen (Py-
rola elliptica), not the aromatic wintergreen,

is figured at 377. The oval or elliptical leaves
are clustered at the base. The flower scape
is 15-30 cm high and bears a raceme at the
summit. The flowers hang singly from the
axils of colorless bracts. The floral formula
is as follows : Ca5,Co5, A 10,05. The Indian-
pipe (monotropa) is also a member of the pyrola
family.

540. Lesson XVI. The whortle-
berry family (vacciniaceae). — The
common whortleberry, or huckleberry
(Gaylussacia resinosa), flowers in May
and June. The shrubs are from ^ocm
to i meter (1-3 feet) high, and are
much branched. The leaves are ovate,
and when young are more or less
clammy from numerous resinous dots,
from which the plant gets its specific
name (resinosa). The flowers are borne on separate shoots from

283

Fig. 377-
Pyroia elliptica.

284

DICOTYLEDONS.

the leaves of the same season, and hang in one-sided short ra-
cemes as shown in fig. 378. The calyx is short, five-lobed,
and adheres to the ovary. The corolla
is tubular, at length cylindrical with
five short lobes, and is whitish in color.
The stamens are ten in
number, and the com-
pound ovary has a sin-
gle style. The fruit is
a rounded black, edi-
ble berry or drupe,

With ten Seeds. Diagram of Erica.

(Vines.)
541. The family ericacese

contains the trailing arbutus, cassandra, andro-
meda, cassiope, etc. The rhododendron family
contains the rhododendrons, azaleas, kalmias,
etc. These with the pyrola and whortleberry

families are closely related and make up the order heaths, or Bicornes as they

are sometimes termed, because the anther frequently

has two horn-like appendages.

PRIMULINyE.

542. The primrose family (primulaceae). — The
primroses (primula) represent well this family. In fig.
453 is represented the flower of the primrose grown
in conservatories. It is gamosepalous and gamopeta-
lous. There are five stamens, each one inserted on flower. (Vines.")
the tube of the corolla and opposite the lobe. (P'or a description of the flower
see chapter on pollination, Part III.) The floral formula is Ca5,Co5,A5,G5.

Fig. 378.
Whortleberry (Gaylussacia re-

Fig. 380.
Diagram of primula

Topic IX: Dicotyledons with united petals, flower
parts in four whorls.

TUBIFLOR^E.

543. The morning-glory or bindweed family (convolvulaceae). — The
hedge bindweed (Convolvulvus sepium) occurs in moist soil along streams.
The stem is twining as in most of the members of the family. The leaves are

PLANT FAMILIES: PERSONATE.

285

Fig. 381.

Morning-glory (Convol-
vulus sepium).

arrow- or halberd-shaped, and the gamopetal-
ous corolla is white or rose color. The corolla
forms a broad funnel-shaped tube, and is
twisted or convolute in the
bud, as in all the mem-
bers of the family. Floral
formula : Ca5,Co5,A5,G2.
The five sepals are covered
by two large bracts. Other
members of this family are
the morning-glory, sweet potato,
cypress vine, the parasitic dodder,
etc.

PERSONATyE.

544. The nightshade family
(solanaceae). — Fig. 382 represents
the ground- cherry (physalis),a mem-
ber of this family. The formula
for the flower is Ca5,Co5,A5,G2.
The calyx becomes enlarged and
inflated, enclosing the edible berry.
The potato, egg-plant, tomato, to-

bacco, etc., are members of the
nightshade family.

545. The fig wort family (scro-
phulariaceae). — The mullein (ver-
bascum), toad-flax (linaria), turtle-
head (chelone), etc , are members of
the figwort family. The plants are
mostly herbs. The stamens are
usually didynamous (four in two
pairs, one pair shorter than the
other) or diandrous (two stamens).
The stamens are inserted on the
two lipped corolla tube, which is
more or less irregular. In some
genera there are five stamens, as in
verbascum.

546. The borage family (boragi-
nacese). — The pretty little forget-

Fig. 382.
Ground-cherry (Physalis pennsylvanica).

286

DICO 71 YLEDONS.

me-not belongs to this family. The flowers are borne in a curved and more or
less one-sided (helicoid) cyme as shown in fig. 383.
The plant grows in wet low ground. The flower
stalks are forked, and continue to grow and
blossom all through the summer. The corolla
is rotate (wheel-shaped), the spreading blue
lobes with a yellow scale on each at the throat of
the tube. Alternating with these scales are the
five short stamens. The ovary is four-divided,
and in fruit forms four nutlets.

Fig- 383-
Forget-me-not.

NUCULIFER^E.

547. Lesson XVII. The mint
family (labiatae). — The mint
family contains a large number
of genera and takes its common
name from the mints, of which
there are several species belong-
ing to the genus mentha. In the figure of the " dead-nettle "
(Lamium amplexicaule), which is also one of the members of
this family, we see that the lobes of the irregular corolla are
arranged in such a manner as to suggest two lips, an upper and
a lower one. From this character of the corolla, which obtains
in nearly all the members, the family receives its name of
Labiates. The calyx is five-lobed. The stamens, four in number,
arise from the tube of the corolla, and converge in pairs. The
ovary is divided into four lobes, and at the maturity of the seed

Fig. 384.

Spray of dead-nettle (Lamium am-
plexicaule), leaves and flowers.

PLANT FAMILIES: LABlATsE.

287

these form four nutlets. The leaves are rounded, crenate on the
margins, the lower ones petioled and heart-
shaped, and the upper ones sessile and clasp-
ing around the stem beneath the flower clusters.
From the clasping character of the upper leaves
the plant derives its specific name of amplexi-
caule. The plant occurs in waste places and is
rather common.

Fig. 385-

Diagram of lamium
flower.

CONTORTS.

548. The gentian family (gentianaceae). — The gentians usually appear
late in the summer or autumn. The fringed gentian (fig. 386) lingers often

Fig. 386.
Gentian (G. crinita).

Fig. 387-
The bluet (Houstonia coerulea).

288

DICOTYLEDONS.

until the snow arrives. The flower is gamosepalous and gamopetalous.
The corolla is bell-shaped, with four lobes. The lobes are blue in color,
somewhat spreading, and beautifully fringed on the margin. The members
of the gentian family have opposite, simple leaves, and no stipules. The
ovary has a single cavity, but is formed of two united carpels as shown by
the two stigmas, and usually two placentae.

RUBIALES.

549. Lesson XVIII. The honeysuckle family (caprifoli-

. — The members of this family are mostly shrubs (a few
herbs) with opposite leaves. Flowers are gamosepalous and
gamopetalous. The ovary is 2-5 -celled, and coherent with the

Fig. 388.
Partridge-berry (Mitchella repens).

Fig. 389-
Wild honeysuckle (Lonicera ciliata).

tube of the calyx. The corolla is tubular, or wheel-shaped, and
the stamens are inserted on its tube. The fly-honeysuckle (Loni-
cera ciliata), shown in fig. 389, is an example, with a tubular or
funnel-shaped, nearly regular corolla. The corolla has a small
spur at the base, and the flowers are in pairs.

550. The twin flower (Linnsea borealis) occurs in cold situa-

PLANT FAMILIES: DIPSACACE^E.

289

Fig. 390.
Twin flower (Linnsa borealis).

tions in moors or damp woods, and blossoms in June. The
stems are creeping and slender,
the leaves rounded and crenate
on the margin, tapering abrupt-
ly into short petioles. From the
prostrate stems the flowering
shoots arise 8— locm, leafy be-
low, and above forking into two
slender pedicels, each bearing a
bell-shaped, purple and whitish
flower. The calyx is coherent
with the ovary, which has three
locules. The five lobes of the
calyx fall away as the flower
dies. The corolla is five-lobed.
Four stamens, two of them shorter than the other two, are at-
tached to the tube of the corolla.

551. Lesson XIX. The teasel family (dipsacacese). — This
family is represented by the common fuller's teasel. The flowers
are collected in a " head." They are separated from one an-
other, however, by a small cup-shaped " epicalyx " which sur-
rounds the inferior ovary. The limb of the calyx is short, and
in some members of the family shows the five divisions. In the
teasel there are four lobes on the limb of the corolla, which is
unsymmetric and bilabiate (zygomorphic), two of the five parts
of the corolla being completely united into one lobe, forming the
upper lip. The stamens are not united by their anthers. (The
distinct stamens and the presence of the epicalyx separating the
flowers of the head are the most prominent characters separating
the dipsacales from the aggregate. )

CAMPANULINvE.

552. The bell-flower family (campanulacese). — The bell-flower (cam-
panula) is illustrated in figure 458. The floral formula is as follows :
Ca5,Co5, A5,G2. The stamens are usually united by their anthers closely
around the style. The style is provided with a brush of hairs, and in

290

DICOTYLEDONS.

pushing its way up between the anthers brushes off some of the pollen and
bears it aloft, where it becomes attached to visiting insects.

The lobelia family is related to the bell-flower family, and contains the
cardinal-flower, great lobelia, and others.

AGGREGATE.

553. Lesson XX. The composite family (composite). — In

all the composites, the flowers
are grouped (aggregated) into
"heads," as in the sunflower,
where each head is made up of
a great many flowers crowded
closely together on a widened
receptacle. The family is a
large one, and is divided into
several sections according to
the kinds of flowers and the
different ways in which they
are combined in the head. In
the asters there is one common
type illustrated in fig. 391 by
the Aster novce-anglice . In the
aster, as is well shown in the
figures, the head is composed
of two kinds of flowers, the

Fig- 39'-
Aster novae-angliae.

Fig. 392.
Head of flowers of Aster novae-anglue.

PLANT FAMILIES: COMPOSITE.

29I

tubular flowers and the ray flowers. In the tubular flowers
the corolla is united to form a slender tube, which is five-notched
at the end, representing the five petals. In the ray flowers the
corolla is extended on one side into a strap-shaped expansion.
Together these strap-shaped corollas form the "rays" of the
head. The corolla is split down on one side, which permits
the end ^ then to expand and form the "strap." This is a

Fig. 393- Fig- 394- Fig. 395. Fig. 396.

Ray flower of Aster novas" Tubular flower Tubular flower Syngenecious
anglise. of aster. opened to show syn- stamens opened to

genecious stamens. show style and two
stigmas.

ligula, or more correctly speaking a false ligula. In fact the ray
flower is bilabiate. By counting the "teeth" of the false ligula
there are found only three, which indicates that the strap here
is made up of only three parts of the 5-merous corolla. The
two other limbs of the corolla are rudimentary, or suppressed,
on the opposite side of the tube. True ligulate flowers are
found in the chicory, dandelion, or in the hieracium, where the
five points are present on the end of the ligula.

554. The calyx tube in the aster, as in all of the composites,
is united with the ovary, while the limb is free. In the aster, as
in many others, the limb is divided into slender bristles, the
pappus. (In some of the composites the pappus is in the form 01

292

DICO T YLED ONS.

scales. ) The stamens are united by their anthers into a tube
(syngenecious) which closely surrounds the style. (In am-
brosia the anthers are sometimes distinct. ) The style in pushing
through brushes out some of the pollen from the anthers and
bears it aloft as in the bell-flower, but the stigmatic surface is
not yet mature and expanded, so that close pollination cannot
take place. There are usually no stamens in the ray-flowers.
The ovary is composed of two carpels, as is
shown by the two styles, but there is only one
locule, containing an erect, anatropous, ovule.

The floral formula for the composite family1
then is as follows: Ca5, €05, AS, G2.

555. The rattlesnake- weed (Hieracium veno-
sum) is an example of another type, with only Flg' 397'

* Diagram or composite

one kind of flower in the head, the true ligu- flower- (vines.)

late flower. The hawkweed, or devil's
paint-brush (H. aurantiacum) is a re-
lated species, which is a troublesome
weed. The dandelion and prickly
lettuce are also members of the ligulate-
flowered composites. A number of
the composites have only tubular
flowers, as in the thoroughwort (eu-
patorium) and everlasting (anten-
naria).

556. The extent to which the union of the
parts of the flower has been carried in the
composites, and the close aggregation of the
flowers in a head, represent the highest stage
of evolution reached by the flowers of the
angiosperms. The composites stand just
above the bell-flowers and lobelias, at the
termination of a series. The teasels show
a relationship to the composites in the aggre-
gation of the flowers in a head. But the con-
solidation of the parts of the flower has not been carried so far, and the
flowers are each separated by an "epicalyx " in the form of a minute cup-
shaped involucre. The teasels stand at the termination of another series in

Fig. 398.

Rattlesnake-weed (Hieracium ve-
nosum).

PLANT FAMILIES: COMPOSITE. 293

which are the lonicera and valerian families. The gyncecium of the com-
posites presents a highly specialized structure. The ovary is plainly made
up of two carpels, as shown by the two styles and the internal structure,
but it becomes reduced to a one-seeded achene. From the five carpels in
the pyrolas to the composites there is a gradual tendency toward reduction
in number of the carpels to two, and in the composites the highest speciali-
zation is reached in the consolidation of these into one achene in fruit.

CHAPTER XLIII.

OUTLINE OF TWENTY LESSONS IN THE
ANGIOSPERMS.

557. As a minimum study of the plant families in the angio-
sperms, the following twenty lessons are suggested to represent
nine topics.

MONOCOTYLEDONS.

TOPIC I : Monocotyledons with conspicuous petals.

Lesson I : Liliacese, lily family.
TOPIC II : Monocotyledons with flowers on a spadix.

Lesson 2: Araceae, arum family.

TOPIC III: Monocotyledons with a glume subtending the
flower.

Lesson j: Gramineae, grass family.

DICOTYLEDONS.

TOPIC IV : Dicotyledons with distinct petals, flowers in catkins

or aments, often degenerate.
Lesson 4: Salicacese, willow family.
Lesson 5.- Cupuliferae, oak family.
TOPIC V : Dicotyledons with distinct petals, and hypogynous

flowers, not in true catkins.
Lesson 6: Ulmaceae, elm family.
Lesson 7 : Ranunculaceae, crowfoot family.

294

OUTLINE Of TWENTY LESSONS.

Lesson 8 : Cruciferae, mustard family.
Lesson p.- Geraniaceae, geranium family.
TOPIC VI : Dicotyledons with distinct petals, and perigynous

or epigynous flowers. Many trees and shrubs.
Lesson 10: Aceraceae, maple family.
Lesson n : Rosaceae, rose family.
Lesson 12 : Amygdalaceae, almond family.
Lesson ij: Pomaceae, apple family.
Lesson 14: Papilionaceae, pulse family.
TOPIC VII : Dicotyledons with distinct petals and epigynous

flowers.
Lesson 15: Onograceae, evening primrose family; or Um-

belli ferae, parsley family.
TOPIC VIII : Dicotyledons with united petals, flower parts in

five whorls.

Lesson 16 : Vaccineacese, whortleberry family.
TOPIC IX : Dicotyledons with united petals, flower parts in

four whorls.

Lesson 17 : Labiatae, mint family.
Lesson 18 : Caprifoliaceae, honeysuckle family.
Lesson 19: Dipsacaceae, teasel family.
Lesson 20: Compositae, composite family.

558. Synopsis of families studied in the angiosperms.—
The following synopsis of the families of the angiosperms is in-
tended for reference in grouping the studies in order that the
relationships of the families may be graphically represented.
The tables therefore should not be memorized.

559. Table of families of monocotyledons studied.— In the
monocotyledons there is a single cotyledon on the embryo ; the
leaves are parallel-veined ; the parts of the flower are generally
in threes, and endosperm is usually present in the seed. There
are a few exceptions to all these characters. Thus a single
character is not sufficient to show relationship in groups, but one
must use the sum of several important characters.

The families of monocotyledons can be grouped into three
large divisions as follows :

296 ANGIOSPERMS.

MONOCOTYLEDONS.

PETALOIDE^E: Conspicuous petals (or perianth) are the charac
teristic feature.

Alismacece ; water-plaintain family, alisma, etc.

Liliacece ; lily family, trillium, lily, etc.

Cannacece ; canna family.

Orchidacece ; orchid family.
SPADICIFLOR^ : The spadix and spathe are characteristic.

Aracece ; arum family, skunk's cabbage, jack-in-the-pulpit, etc.

Lemnacece ; duckweed family, lemna, wolffia, etc.

Palmacece ; palm family.

GLUMIFLORAE : The subtending bract (glume) at the base of
the flower is characteristic.

Graminece ; grass family.

Cyperacece ; sedge family.

560. Table of families of dicotyledons studied (a few other
families are introduced in the scheme). In the dicotyledons
there are two cotyledons on the embryo ; the venation of
the leaves is reticulate; the endosperm is usually absent, and
the parts of the flower are frequently in fives. There are
exceptions to all the above characters, and the sum of the
characters must be considered, just as in the monocotyledons.

DICOTYLEDONS.
I. CHORIPETAIJE ; the petals are distinct.

*. Amentiferce, ament- or catkin-bearing plants.
SALICIFLOR^ : Both kinds of flowers in catkins.

Salicacece ; willow family, poplars and willows.
QUERCIFLOR/E : Pistillate flowers in acorns or cones.

Betulacece ; birch family, birch, alder, etc.

Corylacecz ; hazelnut family, hazelnut, hornbeam, etc.

Cupuliferce ; oak family, oak, chestnut, beech.
JUGLANDIFLOR^E : Pistillate flowers form nuts in fruit.

Juglandacece ; walnut family.

**. Choripetalce proper, flower not degenerate.

OUTLINE OF TWENTY LESSONS.

i. Flowers hypogynous.

URTICIFLOR^ : Flowers not in true aments.

Urticacecz ; nettle family.

Ulmacece ; elm family.
POLYGONIFLOR^E : Fruit a triangular or lenticular achene.

Polygonacece ; knotweed family, knotweed, buckwheat.
CURVEMBRY^E : Embryo curved in the seed.

Porlulacacece ; pursley family, claytonia (spring beauty).

Caryophyllacece ; pink family, carnation, corn-cockle, etc.

Chenopodiacea ; pigweed family, pigweed, beet, Russian

thistle, etc.
POLYCARPIC^E : Carpels usually numerous and always distinct.

Ranunculacece ; buttercup family (crowfoot family), butter-
cups, marsh-marigold, clematis, etc.

Nympheacea ; water-lily family.

Berberidacea ; barberry family, mandrake, etc.
RHCEADIN^E : The flowers are dimerous or tetramerous.

Papaveracecz ; poppy family, bloodroot, etc.

Fumariacea ; fumitory family, squirrel-corn, dutchman's-
breeches.

Cruciferce ; mustard family, toothwort, cabbage, turnip, etc.

Droseracece ; sundew family, sundew, venus-flytrap, etc.

Violacece ; violet family.

Sarraceniacece ; pitcher-plant family.
GRUINALES : Carpels united, styles prolonged into a beak.

Oxalidacece ; oxalis family.

Linacecz ; flax family.

Geraniacece ; geranium family, cranesbill, etc.
COLUMNIFER^E : Stamens usually united by their filaments into
a column.

Malvacece ; mallow family, hollyhock, cotton, etc.

2. Flowers perigynous or epigynous.

Stamens arising from a glandular disk, trees or
shrubs,

298 ANGIOSPERMS.

Sapindacece ; soap-berry family, horse-chestnut, etc.
Aceracece ; maple family.

FRANGULIN/E : Includes the holly family, vine family, etc.
SAXIFRAGIN^E : Flower generally perfect and regular, stamens

5 or 10, carpels few (2-5).
Saxifragacecc ; saxifrage family; also currant, witch-hazel,

and sycamore families.
ROSIFLOR^: : Flowers regular, stamens and carpels usually

numerous, trees and shrubs mostly.

Rosacea ; rose family, strawberry, blackberry, rose, etc.
Amygdalacece ; almond family, peach, apricot, plum, cherry,

etc.
Pomacece ; apple family, apple, quince, pear, hawthorn, june-

berry, etc.
LEGUMINOS^: : Flower papilionaceous, carpel single, forming a

pod or legume.

Papilionacea ; pulse family, pea, bean, vetch, etc.
Mimosacea ; mimosa family, sensitive plants.

j. Flowers epigynou

PASSIFLORIN^E : Fruit of three carpels, but with one locule and
three parietal placentae. Here belong the passion-flower,
begonia, and cucurbit families.
MYRTIFLOR^E: Calyx usually prolonged beyond the inferior

ovary, flowers usually 4-merous.
Onagracea ; evening-primrose family.

UMBELLIFLOR./E : Flowers in umbels, sepals and petals small.
Cornacece ; dogwood family.
UmbellifercK ; parsley family.

II. SYMPETAL^E. Petals coherent (gamopetalous).

i. Flowers pentacy die, that is, parts in five whorls (stamens in

two whorls).

BICORNES : Mostly shrubs, flowers usually 4-5-merous, stamens
frequently with two-horned anthers.

OUTLINE OF TWENTY LESSONS. 299

Pyrolaceee ; pyrola family, pyrola, Indian-pipe, etc.
Ericacea ; heath family. (Also rhododendron and whortle-
berry families.)
PRIMULINTE : One -celled ovary, seeds on a central column,

corolla salver-form.
Primulacece ; primrose family.

2. Flowers tetr acyclic, that is, the parts in four whorls.
TUBIFLOR/E : Gamope talous corolla not split, the five parts in-
dicated by a slight unevenness of the margin, corolla twisted
in bud.
Convolvulace<e ; bindweed family, morning-glory, dodder,

etc.
PERSONATE : Flowers frequently bilabiate (the nightshade

family represents this group).

NUCULIFER/E : Calyx gamosepalous ; gamopetalous corolla usu-
ally bilabiate, carpels usually two, forming four nutlets.
Boraginacetz ; borage family, forget-me-not, etc.
Labiate ; mint family, dead-nettle, catnip, etc.
CONTORT/E : The corolla is twisted in the bud, but is split into

five lobes.

Gentianacecc. ; gentian family.

RUBIALES : Leaves opposite with stipules, or veiticillate.
Rubiacece ; madder family, bluet.
Caprifoliacecc ; honeysuckle family, lonicera, etc.
DIPSACALES : Flowers in a head (in one family), no stipules,

anthers distinct.
Valerianacecz ; valerian family.
Dipsacacecc ; teasel family.
CAMPANULIN^E : Flowers not in heads, anthers united.

Campanulacece ; bellflower family.
COMPOSITE : Flowers in heads, anthers united.

Composite ; composite family, aster, solidago, sunflower,
dandelion, etc.

ECOLOGY.
INTRODUCTION.

561. While we are engaged with the study of the life pro-
cesses concerned in nutrition and growth of plants, with the
details of form, structure, and systematic relationship, we should
not overlook the mutual relationships which exist among plants
in their natural habitat, and the phenomena of growth recurring
with the seasons, and influenced by environment, or due to
inherent qualities. By a study of the life histories of plants,
their habits and behavior under different conditions of environ-
ment, we shall broaden our concept of nature and cultivate our
aesthetic, observational, and reasoning faculties. The subject is
too large for full treatment within the limits of a part of an
elementary book. The way here can only be pointed out, and
the few examples and illustrations, it is hoped, will serve to open
the book of nature to the young student, and lead him to study
some of the problems which are presented by every region.
This study of plants, in their mutual and environmental relation-
ships, is ecology.

562. For beginning classes, where only a small part of the
time is available, excursions can be made from time to time dur-
ing the year for this purpose, taking certain subjects for each ex-
cursion. For example, in the autumn one may study means for
the dissemination of seeds, protection of seeds, plant formations,
zonal distribution of plants, formation of early spring flowers,
etc. ; in the winter, twigs and buds, protection of plants against
the cold ; and in the spring, opening of the buds and flowers,
pollenation, etc. , and farther studies on plant societies, relation
of plants to soil, topography, etc.

300

ECOLOGY. SO1

563. In carrying on studies of this kind one should bear in
mind the factors which influence plants in these relationships,
that is, what are called the ecologic factors ; in other words,
those agencies which make up the environmental conditions of
plants, all of which play a greater or lesser role in the habit or
status of the plant concerned, and which, acting on all plants
concerned, give the peculiar color or physiognomy to the plants
of a region or of a more restricted community.

Such factors are climate, with its modifying meteorological
conditions ; texture, chemistry, moisture content, covering, to-
pography, exposure, etc. , of the soil ; influence of light and
heat ; of animals, of plants themselves, and so on.

CHAPTER XLIV.

WINTER BUDS, SHOOTS, ETC.

564. Winter buds and how the young leaves are protected. — In plants
like the pea, bean, corn, etc., which we have been studying, when the plant
is mature it ripens its seed, and then dies. It grows only for one season,
and the plants of the next season are obtained from the seed again. Such
plants are annual. In woody plants like trees and shrubs which grow from
year to year, the young growing ends, where the elongation of the shoot or '
branch will take place the coming year, are usually provided with a special
armature for protection during the cold of the winter, or through the resting
period. This growing end is the bud. One of the very common means of
protection of the buds through the rigor of the winter is by means of bud
scales, which are formed at the close of the season's growth, and which
overlap and closely hide the young and tender bud leaves within. Atten-
tion is called to a few of these buds here, and there will be no difficulty for
the student to obtain quantities of material of several different kinds of trees
and shrubs which it may be desirable to study, and which need not be men-
tioned here.

565. Twigs and buds of the horse-chestnut. — In fig. 399 is illustrated a
shoot of the horse-chestnut. At the end of the shoot there is a large termi-
nal bud, and at its base are two lateral buds. The terminal bud is broader
than the diameter of the shoot, and is ovate in form. We notice that there
are a number of scales which overlap each other somewhat as shingles do on
a roof, only they are turned in the opposite direction. If we begin at the
base of the bud, we can see that the two lowest scales are opposite each
other, and that the two next higher ones are also opposite each other, and
set at right angles to the position of the lower pair. In the same manner
successive pairs of scales alternate, so that the third, fifth, seventh, etc., are
exactly over the first, and the fourth, sixth, etc., are exactly over the second.
Aside from the fact that these brown scales fit closely together over the bud,
we notice that they are covered with a sticky substance which helps to keep
out the surface water. Thus a very complete armature is provided for the
protection of the young leaves inside.

566. Leaf scars. — The number of leaves developed during one season's

302

WINTER BUDS, SffOOTS, ETC.

growth in length of the shoot can be determined by count-
ing the broad whitish scars which are situated just below
each pair of lateral buds. Near the margin of these scars
in the horse-chestnut are seen prominent pits arranged in
a row. These little pits in the leaf scar are formed by
the breaking away of the fibrovascular bundles (which
run into the petiole of the leaf) as the leaf falls in the
autumn.

567. Lateral buds. — The lateral buds, it is noticed,
arise in the axils of the leaves. Each one of these by
growth the next year, unless they remain dormant, will
develop a shoot or branch. Just above the junction of the
upper pair of branches we notice scars which rim around
the shoot in the form of slender rings, several quite close
together. These are the scars of the bud scales of the
previous year. By observing the location of these ring
scars on the stem, the age of the 'branch may be deter-
mined, as well as the growth in length each year. Small
buds may be frequently seen arising in the axils of the bud
scales, that is after the scales have fallen, so that four to
ten small buds may be counted sometimes on these very
narrow zones of the shoot.

568. Bud leaves. — On removing the brown scales of the
bud there is seen a pair of thin membranous scales which
are nearly colorless. Underneath these are young leaves ;
successive pairs lie farther in the bud, in outline similar to
the mature leaves, and each pair smaller than the one just
below it. They are very hairy, with long white woolly
fibres. These woolly fibres serve also to protect the young
leaves from the cold or from sudden changes in the tem-
perature, since they hold the air in their meshes very
securely.

569. Opening of the buds in the spiing. — As the buds
"swell" in the spring of the year, when the growth of
the young leaves and of the shoot begins, the bud scales
are thrown backward and soon fall away as the leaves
unfold, thus leaving the "ring scar" which marks the
start of the new year's growth in length of the shoot.

570. A study of a number of different kinds of woody

Fig. 399-

shoots would serve to show us a series of very interesting 0fT™"0rST- chtstmu8

variations in the color, surface markings, outline of the showing buds and leaf

scars. (A twig with
branch, arrangement of the leaves and consequently dif- a terminal bud should

ferent modes of branching, variations in the leaf scars, the

304

ECO LOG Y.

form, size, color, and armature of the buds, as well as great variations in
the character of the bud scales. There are striking differences between the
buds of different genera, and with careful study differences can also be seen
in the members of a genus.

571. Growth in thickness of woody stems. — In the growth of woody per-
ennial shoots, the shoot increases in length each year at the end. The

shoot also increases in diameter each
year, though portions of the shoot one
year or more old do not increase in
length. We can find where this
growth in diameter of the stem takes
place by making a thin cross section
of a young shoot or branch of one of
the woody plants. If we take the
white ash, for example, in a cross
section of a one-year-old shoot we
Observe the following zones : A cen-
tral one of whitish tissue the cells of
which have thin walls. This makes
a cylindrical column of tissue through
the shoot which we call the pith or
medulla. Just outside of this pith
is a ring of firmer tissue. The inner
portion of this ring shows many
woody vessels or ducts, and the outer
portion smaller ducts, and a great
many thick-walled woody cells or
fibres. This then is a woody zone,
or the zone of xylem.

572. The outer ring is made up of
the bark, as we call it. In this part
are the bast cells. Between the bark
and the woody zone is a ring of small
cells with thin and delicate walls, and
«* ^ ™ ™^™ Protoplasm.
If the section is stained, these cells
are apt to show a deeper color than either the wood zone or the bast zone.
This is, as we will recollect from our study of the bundle in stems, the cam-
bium zone, or the growing part of the older portions of the stem.

573. We may wish to know why these portions of the bundle here form a
continuous or apparently a continuous ring in the stem of a woody plant. In
the study of the sunflower stem, and also of impatiens, attention was called
to the increase in the number of the bundles as the stem increased in age,

Fig. 400.

rings.

WINTER BUDS, SHOOTS, ETC.

If we happened to examine quite old portions of these stems, we would have
observed that a large part or the entire portion of the thin-walled tissue, sep-
arating the woody portions of adjacent bundles, had changed to thick-walled
or woody tissue, so that there is here in the older portions of the sunflower
plant a continuous ring of xylem. This is the case also to some extent with
the bast tissue. We already have noticed that the cambium ring in these
stems is a continuous one, although the cambium between the bundles of the
sunflower plant was not so active as that in the bundle proper. There is,
however, a difference between the tissue lying between adjacent bundles and
that of the bundle itself.

574. The bundles in the ash stem and in other woody stems lie very
closely side by side, so that at first it might appear as if they were continu-
ous. We note, however, that there are radiating lines which extend from the
pith out toward the bast. These run between the bundles. These radiat-
ing lines are formed by the tissue lying between the bundles becoming
squeezed into thin plates, which extend up and down between the bundles.
They are termed the medullary rays,* since they radiate from the pith or
medulla. These are shown well in a section of an oak stem.

575. Difference in the firmness of the woody ring. — We have already
noted that the inner portion of the wood zone contains more and larger ducts
than the outer zone, and that in the outer portion of the same zone the woody
fibres predominate. The ducts are formed during the early spring growth,
and later in the season the development of the fibres predominates.

576. Annual rings in woody stems. — If we now cut across a shoot of the
ash which is several years old, we will note, as shown in fig. 40x3, that there
are successive rings which have a similar appearance to the woody ring in
the one-year-old stem. This can well be seen without any magnification.
The larger size of the woody ducts which are developed each spring, and
the preponderance of the fibres at the close of each season's growth, mark
well the growth in diameter which takes place each year.

577. While the thickened walls of all the cells give strength to the wood,
the different kinds of cells vary in the percentage of strength which they
give. Thus the bast cells which have very thick walls are yet more flexible
than the wood fibres, as can be seen if one strips off some of the bark of the
basswood tree. Again, the woody fibres give more strength to wood than
the same diameter of wood vessels, because they are much more firmly
bound together, and the ends are long and tapering, and are spliced over
each other where cells below and above meet. In the case of the wood
vessels the ends do not taper out so much, or in some cases they meet ad-
jacent cells below or above squarely.

578. Wood then which has a large number of wood vessels compared with
the fibres, or in which the size of the vessels is great, is not so strong as

* Rays, or radiating plates, of tissue appear also in the bundle.

306 ECOLOG Y.

wood which has a large percentage of fibrous elements, and in which the
ducts are comparatively small. Wood with numerous large vessels is also
more spongy, and therefore lighter than woods with a close fibrous struc-
ture. We should find it an exceedingly interesting study if we made a
comparative examination of the growth and strength of the different woods.

579. Phyllotaxy, or arrangement of leaves. — In our study of the organs
which utilize carbon for food, and in examining buds on the winter shoots of
woody plants, we could not fail to be impressed with some peculiarities in the
arrangement of these members on the stem of the plant. Even in the liver-
worts and mosses we note that where there is any indication of leaf-like
expansions on a central axis there is a general plan of arrangement of these
leaf-like structures over successive zones of the axis.

In the horse-chestnut, as we have already observed, the leaves are in pairs,
each one of the pair standing opposite its partner, while the pair just below or
above stand across the stem at right angles to the position of the former pair.
In other cases (the common bed straw) the leaves are in whorls, that is several
stand at the same level on the axis, distributed around the stem. By far the
larger number of plants have their leaves arranged alternately. A simple ex-
ample of alternate leaves is presented by the elm (fig. 347), where the leaves
stand successively on alternate sides of the stem, so that the distance from one
leaf to the next, as one would measure around the stem, is exactly one half
the distance around the stem. This arrangement is 1/2, or the angle of diver-
gence of one leaf from the next is 1/2. In the case of the sedges the angle of
divergence is less, that is 1/3.

By far the larger number of those plants which have the alternate arrangement
have the leaves set at an angle of divergence represented by the fraction 2/5.

580. Other angles of divergence have been discovered, and much stress has
been laid on what is termed a law in the growth of the stem with reference to
the position which the leaves occupy. There are, however, numerous excep-
tions to this regular arrangement, which have caused some to question the
importance of any theory like that of the ' ' spiral theory ' ' of growth propounded
by Goethe and others of his time.

581. As a result, however, of one arrangement or another we see a beauti-
ful adaptation of the plant parts to environment, or the influence which envi-
ronment, especially light, has had on the arrangement of the leaves and
branches of the plant. Access to light and air are of the greatest importance
to green plants, and one cannot fail to be profoundly impressed with the work-
ings of the natural laws in obedience to which the great variety of plants have
worked out this adaptation in manifold ways.

CHAPTER XLV.

SEEDLINGS.

582. An interesting period in the life of plants is during germination, when
the embryo plant comes out of the seed and lifts its leaves and stem above the
ground. In the germinating corn plant the young leaves are wrapped around
one another and enclose the stem, form-
ing a long, slender, pointed sheath, if it

may be so called. As this pushes its way
through the soil it stands erect, with the
pointed end uppermost. Because of its
form and the compactness with which the
leaves are wrapped together, it easily
wedges its way through the soil, with no
harm to the tender leaves and stem.

583. The pea seedling comes out of
the ground in a very different way. By
the swelling of the two thick cotyledons
the outer coat of the' seed is cast partly
off, the root emerges on one side, and the
short stem is curved between

the cotyledons in the form of
an arch. The cotyledons re-
main in the soil, while the
arched stem, as it elongates,
pushes its way
through the soil.
The leaves of

Fig. 401.

How the garden bean comes out of the ground. First the looped hypocotyl, then the
cotyledons pulled out, next casting off the seed coat, last the plant erect, bearing thick
cotyledons, the expanding leaves, and the plumule between them.

307

ECOLOG Y.

the pea are broader and shorter than the leaves of the corn, and cannot well
form a long pointed covering for the stem. If the stem remained straight
the friction of the leaves against the soil would tear them while they are so
tender. But lifted out as they are, suspended from the bent stem, they are
unharmed.

584. The common garden bean. — The bean also in swelling cracks open
the outer coat, the root emerges from underneath the coat in the region of the
scar (hilum) on the concave side, while the minute plumule lies curved between
the edges of the cotyledons near one end. In the case of the bean, the part
of the stem between the cotyledons and the root (called the hypocotyl in all
seedlings) elongates, so that the cotyledons are lifted from the soil. The hypo-
cotyl is the part of the stem here which becomes strongly curved, and the large
cotyledons are dragged out of the soil as shown in fig. 401. The outer coat
becomes loosened, and at last slips off com-
pletely. The plumule (the young part of the
stem with the leaves) is now pushing out from
between the cotyledons. As the cotyledons
are coming out of the ground the first pair of
leaves rapidly enlarge, so that before the stem
has straightened up there is a considerable leaf
surface for the purpose of car-
bon conversion. The leaves
are at first clasped together,
but as the stem becomes erect

Fig. 402.
Germination of castor-oil bean.

they are gradually parted and come to stand out nearly in a horizontal posi-
tion. Fig. 401 shows the different positions, and we see that the same pro-
vision for the protection of the leaves is afforded as in the case of the pea.
As the cotyledons become exposed to the light they assume a green color.
Some of the stored food in them goes to nourish the embryo during germina-
tion, and they therefore become smaller, shrivel somewhat, and at last fall off.
585. The castor-oil bean. — This is not a true bean since it belongs to a
very different family of plants (euphorbiaceae). In the germination of this
seed a very interesting comparison can be made with that of the garden bean.
As the " bean" swells the very hard outer coat generally breaks open at the

SEEDLINGS.

309

free end and slips off at the stem end. The next coat within, which is also
hard and shining black, splits open at the opposite end, that is at the stem
end. It usually splits open in the form of three ribs. Next within the inner
coat is a very thin, whitish film (the remains of the nucellus, and correspond-
ing to the perisperm) which shrivels up and loosens from the white mass, the
endosperm, within. In the castor-oil bean, then, the endosperm is not all
absorbed by the embryo during the formation of the seed. As the plant
becomes older we should note that the fleshy endosperm becomes thinner and
thinner, and at last there is nothing but a thin whitish film covering the green
faces of the cotyledons. The endosperm has been gradually absorbed by the
germinating plant through its cotyledons and used for food.

586. How the embryo gets out of a pumpkin seed. — We should not fail
to germinate some seeds of a pumpkin or squash. Some of the seeds should

Fig. 403.

Seedlings of castor-oil bean casting the seed coats, and showing papery remnant of the
endosperm.

be sown in the soil, and some on damp sphagnum covered with moist paper,
or between the folds of a damp cloth, first soaking them for ten to twelve

3TO

ECO LOG Y.

hours. The pumpkin seed is the one we have selected for this study. It
will be instructive first to examine those which have been germinated in the

Fig. 404.

Germinating seed of pumpkin, showing how the heel or "peg " catches on the seed coat
to cast it off.

folds of moist cloth and paper, so that they can readily be observed at all
stages, without digging them up from the soil.

587. The root pushes its
way out from between the
stout seed coats at the
smaller end, and then turns
downward unless prevented
from so doing by a hard
surface. After the root is
long, and the two
halves of the seed coats
have begun to be pried
apart, if we look in this rift
at the junction of the root
and stem,
we will
see that
one end

of the seed coat is caught
against a heel, or "peg,"
which has grown out from
the stem for this purpose.
Now if we examine one
which is a little more ad-
vanced, we will see this
heel more distinctly, and
also that the stem (hypo-
Fig. 405. cotyl) is arching out away
Escape of the pumpkin seedling from the seed coats. from the seed coats, AS

SEEDLINGS. 311

the stem arches up its back in this way it pries with the cotyledons against
the upper seed coat, but the lower seed coat is caught against this heel, and
the two are pulled gradually apart. In this way
the embryo plant pulls itself out from between
the seed coats. In the case of seed which are
planted deeply in the soil we do not see this con-
trivance unless we dig down into the earth. The
stem of the seedling arches through the soil, pull-
ing the cotyledons up at one end. Then it
straightens up, the green cotyledons part, and
open out their inner faces to the sunlight, as
shown in fig. 406. If we dig into the soil we
will see that this
same heel is formed
on the stem, and
that the seed coats
are cast off into the
soil.

— — ••• r f ,fc" _j m* - " ' ' — • "^

Fig. 406.
Pumpkin seedling rising from the ground.

Arisaema triphyllum.

588. Germination of seeds of jack-in-the-pulpit. — The ovaries of jack-in-
the-pulpit form large, bright red berries with a soft pulp enclosing one to

Fig. 407.

Seedlings of jack-in-the-pul-
pit ; embryo backing out of the
seed.

Fig. 408.

Section of germinating embryos of
iack-in-the-pulpit, showing young
leaves inside the petiole of the coty-
ledon. At the left cotyledon shown
surrounded by the endosperm in the
seed ; at right endosperm removed to
show the club-shaped cotyledon.

several large seeds. The seeds are oval in form. Their germination is inter-
esting, and illustrates one type of germination of seeds common among

312

ECO LOG Y.

monocotyledonous plants. If the seed are covered with sand, and kept in a
moist place, they will germinate readily.

589. How the embryo backs out of the seed. — The embryo lies within the
mass of the endosperm ; the root end, near the smaller end of the seed. The
club-shaped cotyledon lies near the middle of the seed, surrounded firmly on
all sides by the endosperm. The stalk, or
petiole, of the cotyledon, like the lower
part of the petiole of the leaves, is a hollow
cylinder, and contains the younger leaves,
and the growing end of the stem or bud.
When germination begins, the stalk, or
petiole, of the cotyledon elongates. This
pushes the root end of the embryo out at
the small end of the
seed. The free end
of the embryo now
enlarges somewhat,

Fig. 409.

Fig. 4.

Seedlings of jack-in-the- Embryos of jack-in-the-pulpit

Fig. 4'
Seedling of jack-in-

pulpit, first leaf arching out attached to the endosperm In seed the-pulpit; section of
of the petiole of the coty coats, and showing the simple first the endosperm and
ledon. leaf. cotyledon.

as seen in the figures, and becomes the bulb, or corm, of the baby jack. At
first no roots are visible, but in a short time one, two, or more roots appear on
the enlarged end.

SEEDLINGS. 313

590. If we make a longisection of the embryo and seed at this time we can
see how the club-shaped cotyledon is closely surrounded by the endosperm.
Through the cotyledon, then, the nourishment from the endosperm is readily
passed over to the growing embryo. In the hollow part of the petiole near
the bulb can be seen the first leaf.

591. How the first leaf appears. — As the embryo backs out of the seed,
it turns downward into the soil, unless the seed is so lying that it pushes
straight downward. On the upper side of the arch thus formed, in the
petiole of the cotyledon, a slit appears, and through this opening the first leaf
arches its way out. The loop of the petiole comes out first, and the leaf later,
as shown in fig. 409. The petiole now gradually straightens up, and as it
elongates the leaf expands.

592. The first leaf of the jack-in-the-pulpit is a simple one. — The first leaf
of the embryo jack-in-the-pulpit is very different in form from the leaves which
we are accustomed to see on mature plants. If we did not know that it
came from the seed of this plant we would not recognize it. It is simple,
that is it consists of one lamina or blade, and not of three leaflets as in the
compound leaf of the mature plant. The simple leaf is ovate and with a
broad heart-shaped base. The jack-in-the-pulpit, then, as trillium, and some
other monocotyledonous plants which have compound leaves on the mature
plants, have simple leaves during embryonic development. The ancestral
monocotyledons are supposed to have had simple leaves. Thus there is in
the embryonic development of the jack-in-the-pulpit, and others with com-
pound leaves, a sort of recapitulation of the evolutionary history of the leaf in
these forms.

CHAPTER XLVI.

FURTHER STUDIES ON NUTRITION.

593. In our former studies on nutrition we found that such
plants as the corn, pea, bean, etc., obtain their liquid food
through the medium of root hairs. The liverworts and mosses
obtain theirs largely through similar outgrowths, the rhizoids,
while a majority of the algae, being bathed on all sides by water,
absorb liquid food through any part of the surface. We will find
it instructive to study some of the different ways in which diverse
plants obtain their liquid food.

594. Nutrition in lemna. — A water plant is illustrated in fig. 412. This
is the common duckweed, Lemna trisulca. It is very peculiar in form and in

Tig. 412.
Fronds of the duckweed (Lemna trisulca).

its mode of growth. Each one of the lateral leaf-like expansions extends out-
wards by the elongation of the basal part, which becomes long and slender.
Next, two new lateral expansions are formed on these by prolification from near

NUTRITION: WOLFFIA.

the base, and thus the plant continues to extend. The plant occurs in ponds
and ditches and is sometimes very common and abundant. It floats on the
surface of the water. While the flattened part of the plant resembles a leaf
it is really the stem, no leaves being present. This expanded green body is
usually termed a "frond." A single rootlet grows out from the under side
and is destitute of root hairs. Absorption of nutriment therefore takes place
through this rootlet and
through the under side
of the "frond."

595. Spirodela polyr-
rhiza. — This is a very
curious plant, closely re-
lated to the lemna and
sometimes placed in the
same genus

Fig- 413-
Spirodela polyrrhiza.

It occurs

in similar situations, and

is very readily grown in aquaria. It reminds
one of a little insect as seen in fig. 413. There
are several rootlets on the under side of the
frond. Absorption of nutriment takes place
here in the same way as in lemna.

596. Nutrition in wolffia. — Perhaps the most curious of these modified
water plants is the little wolffia, which contains the smallest specimens of the

Fig. 414.

Young frond of wolffia
growing out of older one.

Fig. 415. Fig. 416.

Young frond of wolffia Another species o f
separating fromolder one. wolffia, the two fronds
still connected.

flowering plants. Two species of this genus are shown in figs. 414-416.
The plant body is reduced to nothing but a, rounded or oval green body, which

ECO LOG Y.

represents the stem. No leaves or roots are present. The plants multiply
by " prolification," the new fronds growing out from a depression on the under
side of one end.

597. Nutrition of lichens. — Lichens are very curious plants which grow
on rocks, on the trunks and branches of trees, and on the soil. They form
leaf-like expansions more or less green in color, or brownish, or gray, or they
occur in the form of threads, or small tree-like formations. Sometimes the
plant fits so closely to the rock on which it grows that it seems merely to
paint the rock a slightly different color, and in the case of many which occur on
trees there appears to be to the eye only a very slight discoloration of the bark
of the trunk, with here and there the darker colored points where fruit todies

Fig. 417.
Frond of lichen (peltigera), showing rhizoids.

are formed. ' The most curious thing about them is, however, that while they
form plant bodies of various form, these bodies are of a "dual nature" as
regards the organisms composing them. The plant bodies, in other words, are
formed of two different organisms which, woven together, exist apparently
as one. A fungus on the one hand grows around and encloses in the
meshes of its mycelium the cells or threads of an alga, as the case may be.

If we take one of the leaf-like forms known as peltigera, which grows on
damp soil or on the surfaces of badly decayed logs, we see that the plant
body is flattened, thin, crumpled, and irregularly lobed. The color is dull
greenish on the upper side, while the under side is white or light gray, and
mottled with brown, especially the older portions. Here and there on the
under surface are quite long slender blackish strands. These are composed
entirely of fungus threads and serve as organs of attachment or holdfasts,
and for the purpose of supplying the plant body with mineral substances

NUTRITION: LICHENS.

317

which are in solution in the water of the soil. If we make a thin section of
the leaf-like portion of a lichen as shown in fig. 418, we shall see that it is
composed of a mesh of colorless threads which in certain definite portions
contain entangled green cells. The colorless threads are those of the fungus,
while the green cells are those of the alga. These green cells of the alga per-
form the function of chlorophyll bodies for the dual organism, while the threads
of the fungus provide the mineral constituents of plant food. The alga,
while it is not killed in the embrace of the fungus, does not reach the per-

Fig-4

Lichen (peltigera), section of thallus ; dark zone of rounded bodies made up largely of the
algal cells. Fungus cells above, and threads beneath and among the algal cells.

feet state of development which it attains when not in connection with the
fungus. On the other hand the fungus profits more than the alga by this
association. It forms fruit bodies, and perfects spores in the special fruit
bodies, which are so very distinct in the case of so many of the species of
the lichens. These plants have lived for so long a time in this close associa-
tion that the fungi are rarely found separate from the algse in nature, but in
a number of cases they have been induced to grow in artificial cultures sep-
arate from the alga. This fact, and also the fact that the algae are often
found to occur separate from the fungus in nature, is regarded by many as an
indication that the plant body of the lichens is composed of two distinct or-
ganisms, and that the fungus is parasitic on the alga.

ECO LOG Y.

598. Others regard the lichens as autonomous plants, that is, the two or-
ganisms have by this long-continued community of existence become unified
into an individualized organism, which possesses a habit and mode of life

Fig. 419.

Section of fruit body or apothecium of lichen (parmelia), showing asci and spores of the
fungus.

distinct from that of either of the organisms forming the component parts.
This community of existence between two different organisms is called by
some mutualism, or symbiosis.

Nitrogen gatherers.

599. How clovers, peas, and other legumes gather nitrogen. — It has long
been known that clover plants, peas, beans, and
many other leguminous plants are often able to
thrive in soil where the cereals do but poorly.
Soil poor in nitrogenous plant food becomes richer
in this substance where clovers, peas, etc., are
grown, and they are often planted for the purpose
of enriching the soil. Leguminous plants, espe-
cially in poor soil, are almost certain to have en-
largements, in the form of nodules, or "root
tubercles." A root of the common vetch with
some of these root tubercles is shown in fig. 420.

600. A fungal or bacterial organism in these
root tubercles. — If we cut one of these root tuber-
cles open, and mount a small portion of the in-
terior in water for examination with the micro-
scope, we will find small rod-shaped bodies,

Fig. 420.

Root of the common vetch
showing root tubercles.

NUTRITION: NITROGEN GATHERERS. 319

some of which resemble bacteria, while others are more or less forked into
forms like the letter Y, as shown in fig. 421. These bodies are rich in
nitrogenous substances, or proteids. They are portions of a minute organism,
of a fungus or bacterial nature, which attacks the roots of leguminous plants

Fig. 421. Fig. 422.

Root-tubercle organism from vetch, old con- Root-tubercle organism from Medicago
dition. denticulata.

and causes these nodular outgrowths. The organism (Phytomyxa legumi-
nosarum) exists in the soil and is widely distributed where legumes grow.

601. How the organism gets into the roots of the legumes. — This minute
organism in the soil makes its way through the wall of a root hair near the
end. It then grows down the interior of the root hair in the form of a
thread. When it reaches the cell walls it makes a minute perforation,
through which it grows to enter the adjacent cell, when it enlarges again.
In this way it passes from the root hair to the cells of the root and down to
near the center of the root. As soon as it begins to enter the cells of the
root it stimulates the cells of that portion to greater activity. So the root
here develops a large lateral nodule, or "root tubercle." As this "root
tubercle" increases in size, the fungus threads branch in all directions,
entering many cells. The threads are very irregular in form, and from cer-
tain enlargements it appears that the rod-like bodies are formed, or the
thread later breaks into myriads of these small " bacteroids. "

602. The root organism assimilates free nitrogen for its host. — This
organism assimilates the free nitrogen from the air in the soil, to make the
proteid substance which is found stored in the bacteroids in large quantities.
Some of the bacteroids, rich in proteids, are dissolved, and the proteid sub-
stance is made use of by the clover or pea, as the case may be. This is why
such plants can thrive in soil with a poor nitrogen content. Later in the
season some of the root tubercles die and decay. In this way some of the
proteid substance is set free in the soil. The soil thus becomes richer in
nitrogenous plant food.

The forms of the bacteroids vary. In some of the clovers they are oval,
in vetch they are rod-like or forked, and other forms occur in some of the
other genera.

320

ECO LOG Y.

Mycorhiza.

603. Many others of the higher plants have fungi associated with their
roots. Such roots are mycorhiza. In some genera of the orchids the roots
form a compact mass resembling coral growth, as in the coral-root orchid.
The curious Indian-pipe (monotropa) has roots which form a large closely
branched mass of thickened short roots. In these cases the fungus lives in

Fig. 423.
Dodder.

the cells of the root and some of the threads of the fungus extend to the
outside into the soil, and perhaps partly serve as absorbent organs since the
root hairs are very rare or altogether absent on such roots. The Indian-
pipe plant possesses no chlorophyll, the fungus in its roots probably assimi-
lates carbonaceous food from decaying organic matter in the soil, and gives
it up to its host.

604. Mycorhiza with the fungus in the roots are endotropic mycorhiza.
The root tubercles of the legumes also belong to this class. Ectotropic my-

NUTRITION: MYCORttlZA. 321

corhiza have the fungus on the outside of the roots. These often occur on
the roots of the oak, beech, hornbeam, etc., in forests where there is a great
deal of humus from the decaying leaves and other vegetation. The young
growing roots of the oak, beech, hornbeam, etc., become closely covered
with a thick felt of the mycelium, so that no root hairs can develop. The
root is also thickened. The fungus serves here as the absorbent organ for
the tree. It also acts on the humus, converting it into available plant food
and transferring it over to the tree.

605. Nutrition of the dodder. — The dodder (cuscuta) is an example of one
of the higher plants that is parasitic. The stem twines around the stems of
other plants, sending haustoria in their tissues. By means of these the nutri-
ment is absorbed.

606. Carnivorous plants. — Examples of these are me well-known venus
fly-trap and the common sundew.

607. Nutrition of bacteria. — Bacteria are very minute plants, in the
form of short rods, which are either straight or spiral, while some are
minute spheres. They are widely distributed ; some cause diseases of plants
and animals, others cause decay of organic matter, while still others play an
important role in converting certain nitrogen compounds into an available
form for plant food. They absorb their food through the surface of their
body. They may be obtained in abundance for study in infusions of plants
or of meats. 3

fo

CHAPTER XLVII.

FURTHER STUDIES ON NUTRITION CONCLUDED.

608. Nutrition of moulds. — In our study of mucor, as we have seen, the

growing or vegetative part
of the plant, the mycelium,
lies within the substratum,
which contains the food
materials in solution, and the
slender threads are thus
bathed on all sides by them.
The mycelium absorbs the
watery solutions throughout
the entire system of ramifica-
tions. When the upright
fruiting threads are devel-
oped they derive the materials
for their growth directly from
the mycelium with which
they are in connection. The
moulds which grow on de-
caying fruit or on other
organic matter derive their
nutrient materials in the same
way. The portion of the
mould which we usually see
on the surface of these sub-
stances is in general the fruit-
ing part. The larger part
of the mycelium lies hidden
within the subtratum.

609. Nutrition of para-
Fig 424.

Carnation rust on leaf and flower stem. From photo- sitic fungi.- Certain of the
graph. fungi grow on or within the

higher plants and derive their food materials from them and at their ex-
pense. Such a fungus is called a parasite, and there are a large number

322

NUTRITION : FUNGI.

323

of these plants which are known as parasitic fungi. The plant at whose
expense they grow is called the "host."

One of these parasitic fungi, which it is quite easy to obtain in green-
houses or conservatories during the autumn and winter, is the carnation
rust (Uromyces caryophyllinus}, since it breaks out in rusty dark brown
patches on the leaves and stems of the carnation (see fig. 424). If we make
thin cross sections through one of these spots on a leaf, and place them for a

Fig. 425.
Several teleutospores, showing the variations in form.

few minutes in a solution of chloral hydrate, portions of the tissues of the
leaf will be dissolved. After a few minutes we wash the sections in water on
a glass slip, and stain them with a solution of eosin. If the sections were care-

Fig. 426.

Cells from the stem of a rusted carnation, showing the intercellular mycelium and haustoria.
Object magnified 30 times more than the scale.

fully made, and thin, the threads of the mycelium will be seen coursing be-
tween the cells of the leaf as slender threads. Here and there will be seen
short branches of these threads which penetrate the cell wall of the host and
project into the interior of the cell in the form of an irregular knob. Such
a branch is a haustorium. By means of this haustorium, which is here

ECOL&C V.

only a short branch of the' mycelium, nutritive substances are taken by the
fungus from the protoplasm or cell-sap of the carnation. From here it
passes to the threads of the mycelium. These in turn supply food material
for the development of the dark brown gonidia, which we see form the dark-
looking powder on the spots. Many other fungi form haustoria, which take
up nutrient matters in the way described for the carnation rust. In the case

Fig. 427. Fig. 428.

Cell from carnation leaf, showing Intercellular mycelium with haustoria entering

haustorium of rust mycelium grasping the cells. A , of Cystopus candidus (white rust) ;

the nucleus of the host, h, haustori- B, of Peronospora calotheca. (De Bary.)
um ; «, nucleus of host.

of other parasitic fungi the threads of the mycelium themselves penetrate
the cells of the host, while in still others the mycelium courses only between
the cells of the host (fungus of peach leaf-curl for example) and derives food
materials from the protoplasm or cell-sap of the host by the process of
osmosis.

610. Nutrition of the larger fungi. — If we select some one
of the larger fungi, the majority of which belong to the mush-
room family and its relatives, which is growing on a decaying log
or in the soil, we shall see on tearing open the log, or on remov-
ing the bark or part of the soil, as the case may be, that the
stem of the plant, if it have one, is connected with whitish
strands. During the spring, summer, or autumn months, exam-
ples of the mushrooms connected with these strands may usually
be found readily in the fields or woods, but during the winter and

NUTRITION: FUNGI.

325

colder parts of the year often they may be seen in forcing houses,
especially those cellars devoted to the propagation of the mush-
room of commerce.

611. These strands are made up of numerous threads of the
mycelium which are closely twisted and interwoven into a cord
or strand, which is called a mycelium strand, or rhizomorph.
These are well shown in fig. 434, which is from a photograph of
the mycelium strands, or "spawn " as the grower of mushrooms
calls it, of Agaricus campestris. The little knobs or enlargements
on the strands are the young fruit bodies, or ' ' buttons. ' '

612. While these threads or strands of the mycelium in the
decaying wood or in the decaying organic matter of the soil are

Fig. 429.

Sterile mycelium on wood props in coal mine, 400 feet below surface. (Photographed by
the author.)

326 ECOLOG Y.

not true roots, they function as roots, or root hairs, in the ab-
sorption of food materials. In old cellars and on damp soil in
moist places we sometimes see fine examples of this vegetative
part of the fungi, the mycelium. But most magnificent examples
are to be seen in abandoned mines where timber has been taken
down into the tunnels far below the surface of the ground to
support the rock roof above the mining operations. I have
visited some of the coal mines at Wilkesbarre, Pa. , and here on
the wood props and doors, several hundred feet below the surface,
and in blackest darkness, in an atmosphere almost completely
saturated at all times, the mycelium of some of the wood-destroy-
ing fungi grows in a profusion and magnificence which is almost
beyond belief. Fig. 429 is from a flash-light photograph of a
beautiful example 400 feet below the surface of the ground.
This was growing ov£r the surface of a wood prop or post, and
the picture is much reduced. On the doors in the mine one can
see the strands of the mycelium which radiate in fan-like figures
at certain places near the margin of growth, and farther back the
delicate tassels of mycelium which hang down in fantastic figures,
all in spotless white and rivalling the most beautiful fabric in the
exquisiteness of its construction.

Studies of mushrooms.

'-'• 4" -• '<&.•"

613. Form of the mushroom. — A good example for this
study is the common mushroom (Agaricus campestris).

This occurs from July to November in lawns and grassy fields.
The plant is somewhat umbrella-shaped, as shown in fig. 430,
and possesses a cylindrical stem attached to the under side of the
convex cap or pileus. On the under side of the pileus are thin
radiating plates, shaped somewhat like a knife blade. These are
the gills, or lamellae, and toward the stem they are rounded on
the lower angle and are not attached to the stem. The longer
ones extend from near the stem to the margin of the pileus, and
the V-shaped spaces between them are occupied by successively

NUTRITION: MUSHROOMS.

327

Agaricus campestris.

Fig. 430.
View of under side showing stem, annulus, gills, and margin of pileus.

Fig. 431.

Agaricus campestris. Longitudinal section through stem and pileus. a, pileus; b, portion
of veil on margin of pileus ; c, gill ; /) fragment of aunulus ; e, stipe.

328

ECO LOG Y.

shorter ones. Around the stem a little below the gills is a collar,
termed the ring or annulus.

614. Fruiting surface of the mushroom. — The surface of
these gills is the fruiting surface of the mushroom, and bears the
gonidia of the mushroom, which are dark purplish brown when
mature, and thus the gills when old are dark in color. If we make
a thin section across a few of the gills, we see that each side of
the gill, is covered with closely crowded club-shaped bodies, each
one of which is a basidium. In fig. 432 a few of these are en-
larged, so that the
structure of the gill
can be seen. Each
basidium of the com-
mon mushroom has

Fig. 432.

Portion of section of lamella of Agaricus campestris.
tr, trama; sA, subhymenium ; 6, basidium; st, sterigma
(//. sterigmata) ; g-, gonidium.

Fig. 433-

Portion of hymenium of Co-
prinus micaceus, showing large
cystidium in the hymenium.

two spinous processes at the free end. Each one is a sierig'ma
(plural slerig' matd) , and bears a gonidium. In a majority of the
members of the mushroom family each basidium bears four gonidia.
When mature these gonidia easily fall away, and a mass of them
gives a purplish -black color to objects on which they fall, so that
a print of the under surface of the cap showing the arrangement
of the gills can be obtained by cutting off the stem, and placing
the pileus on white paper for a time.
615, How the mushroom is formed, — The mycelium of the

NUTRITION: MUSHROOMS.

329

330

ECOLOGY.

mushroom lives in the ground, and grows here for several months
or even years, and at the proper seasons develops the mature
mushroom plant. The mycelium lives on decaying organic mat-
ter, and a large number of the threads grow closely together form-
ing strands, or cords, of mycelium, which are quite prominent
if they are uncovered by removing the soil, as shown in fig. 434.
616. From these strands the buttons arise by numerous threads
growing side by side in a vertical direction, each thread growing
independently at the end, but all lying very closely side by

Fig. 435-

Agaricus campestris; sections of "buttons" of different sizes, showing formation of gills
and veil covering them.

side. When the buttons are quite small the gills begin to form
on the under margin of the knob. They are formed by certain
of the threads growing downward in radiating ridges, just as many
of these ridges being started as there are to be gills formed. At
the same time, threads of the stem grow upward to meet those at
the margin of the button in such a manner that they cover up
the forming gills, and thus enclose the gills in a minute cavity.
Sections of buttons at different ages will show this, as is seen
in fig. 435. This curtain of mycelium which is thus stretched
across the gill cavity is the veil. As the cap expands more
and more this is stretched into a thin and delicate texture as

NUTRITION: MUSHROOMS. 33!

shown in fig. 436. Finally, as shown in fig. 437, this veil is
ruptured by the expansion of the pileus, and it either clings

Fig. 436.

Agaricus campestris ; nearly mature plants, showing veil still stretched across the gill
cavity.

Fig- 437-

Agaricus campestris ; under view of two plants just after rupture of veil, fragments of the
latter clinging both to margin of pileus and to stem.

332

ECOLOG V.

Fig. 438.

Agaricus campestris ; plant in natural position just after rupture of veil, showing tendency
to double annulus on the stem. Portions of the veil also dripping from margin of pileus.

Fig. 439-
Agaricus cai ipestris ; spore print.

NUTRITION: MUSHROOMS.

333

334 ECOLOGY.

to the stem as a collar, or a portion of it remains clinging to
the margin of the cap. When the buttons are very young
the gills are white, but they soon become pink in color, and

Fig. 441-
Amanita phalloides ; white form, showing pileus, stipe, annulus, and volva.

very soon after the veil breaks the gonidia mature, and then
the gills are dark brown.

617. Beware of the poisonous mushroom. — The number of
species of mushrooms, or toadstools as they are often called, is
very great. Besides the common mushroom (Agaricus campes-

NUTRITION ' : MUSHROOMS.

335

tris) there are a large number of other edible species. But
one should be very familiar with any species which is gathered
for food, unless collected by one who certainly knows what the
plant is, since carelessness in this respect sometimes results fatally
from eating poisonous ones.

618. A plant very similar in structure to the Agaricus campes-
tris is the Lepiota naucina, but the spores are white, and thus the
gills are white, except that in age they become a dirty pink.
This plant occurs in grassy fields and lawns often along with the

Fig. 442.

Amanita phalloides ; plant turned to one side, after having been placed in a horizontal
position, by the directive force of gravity.

common mushroom. Great care should be exercised in collect-
ing and noting the characters of these plants, for a very deadly
poisonous species, the deadly amanita (Amanita phalloides) is
perfectly white, has white spores, a ring, and grows usually in
wooded places, but also sometimes occurs in the margins of lawns.
In this plant the base of the stem is seated in a cup-shaped struc-
ture, the volva, shown in fig. 441. One should dig up the stem
carefully so as not to tear off this volva if it is present, for with
the absence of this structure the plant might easily be mistaken
for the lepiota, and serious consequences would result,

33^ ECOLOGY.

619. Wood-destroying fungi. — Several thousand different
species of mushrooms are known in different countries. A large
number of them grow in the soil, deriving their nutriment from
decaying organic matter in the soil. Others grow in decaying
logs and plant parts. Still quite a large number of the mush-
rooms and their relatives are able to grow in the woody portions
of the trunks of living trees, causing decay of the trunks. Still
others are parasitic. The wood-destroying fungi not only do
great damage in destroying the usefulness of some timber trees
for lumber, but they often so weaken the tree trunk or roots of
the tree that the trees are broken down during gales.

620. The mycelium enters the tree at wounds in the trunk,
limbs, or roots. A limb of a tree broken during a heavy wind,
or by falling trees, or by the weight of snow, makes an infection
court for the mycelium. A falli-ng tree may bruise and knock off
the bark from a sound standing tree and thus open a way for the
entrance of the wood-destroying mycelium. The roots of trees
are sometimes injured by the wheels of passing vehicles. In some
cases I have known fungi to enter through such injuries. Shade
trees are also similarly injured as well by the gnawing of animals
when allowed to stand near them. Severe pruning of many large
limbs of trees often renders them liable to injury from the attacks
of wood-destroying fungi, since the small amount of leaf surface
remaining is too little for the manufacture of the necessary plant
food for repair of the wounds. A few limbs should be taken off
in a single season when necessary to prune, and extend the proc-
ess over several seasons, rather than to prune so severely in a
single season.

621. From our studies on the growth in thickness of woody
stems we know that the living and growing part of a tree trunk
is confined to a layer just underneath the bark. So when a
bruise or break passes through this layer (cambium) and exposes
the wood within, the mycelium of the wood-destroying fungi can
easily enter. From this point it spreads for long distances in the
interior of the tree, causing decay. Trees thus often become
" hollow." Some of the topmost branches die. The mycelium

NUTRITION : MUSHROOMS.

337

Fig- 443-

Wood-destroying fungus (Hydnum septentrionale on living maple, reduced 1/15. (PhotQ-
graph by the author.)

338 ECOLOG Y.

eventually makes its way to the outside of the tree trunk in
places, where large fruit bodies characteristic of the species are
found. Figure 443 represents a large sugar-maple tree which is
attacked by one of the wood-destroying fungi. The fruit bodies
here are of the shelving form and overlap. The fruiting surface
of this plant on the sugar maple is in the form of spines, instead
of gills, and belongs to the genus hydnum. A number of large
maple trees in the grove where this one stood were injured by
wood-destroying fungi, and many of them were so weakened
thereby that they were blown over during a southeast gale.
Some shelving fungi possess gills like agaricus. Others have
the under surface honeycombed as in polyporus.

622. The roots of trees are often attacked by a mushroom, the
honey agaric (Agaricus melleus). The mycelium here forms
long black strands underneath the bark of the root. These often
extend from the roots up into the interior of the trunk of the
tree, causing decay. The roots are sometimes so weakened by
the fungus that they die and easily break when heavy winds arise.
Figure 444 shows such a tree uprooted. Further, it is broken
about midway of the trunk, because the trunk was weakened
by the mycelium inside. Other trees weakened by fungi, and
broken over during the same gale, are shown in the same figure.

NUTRITION: MUSHROOMS.

339

V;

CHAPTER XLVIII.

DIMORPHISM OF FERNS.

623. In comparing the different members of the leaf series
there are often striking illustrations of the transition from one
form to another, as we have noted in the case of the trillium
flower. This occurs in many other flowers, and in some, as in
the water lily, these transformations are always present, here
showing a transition from the petals to the stamens. In the bud
scales of many plants, as in the butternut, walnut, currant, etc. ,
there are striking gradations between the form of the simple bud
scales and the form of the leaf. Some of the most interesting of
these transformations are found in the dimorphic ferns.

624. Dimorphism in the leaves of ferns. — In the common
polypody fern, the maidenhair, and in many other ferns, all the
leaves are of the same form. That is, there is no difference be-
tween the fertile leaf and the sterile leaf. On the other hand, in
the case of the Christmas fern we have seen that the fertile
leaves are slightly different from the sterile leaves, the former
having shorter pinnae on the upper half of the leaf. The fertile
pinnae are here the shorter ones, and perform but little of the
function of carbon conversion. This function is chiefly per-
formed by the sterile leaves and by the sterile portions of the
fertile leaves. This is a short step toward the division of labor
between the two kinds of leaves, one performing chiefly the labor
of carbon conversion, the other chiefly the labor of bearing the
fruit.

625. The sensitive fern. — This division of labor is carried to
an extreme extent in the case of some ferns. Some of our native

340

DIMORPHISM OF FERNS.

341

ferns are examples of this interesting relation between the leaves
like the common sensitive fern (Onoclea sensibilis) and the
ostrich fern (O. struthiopteris) and the cinnamon fern (Osmunda
cinnamomea). The sensitive fern is here shown in fig. 445.
The sterile leaves are large, broadly expanded, and pinnate, the

Fig. 445-
Sensitive fern ; normal condition of vegetative leaves and sporophylls.

pinnae being quite large. The fertile leaves are shown also in
the figure, and at first one would not take them for leaves at all.
But if we examine them carefully we see that the general plan
of the leaf is the same : the two rows of pinnae which are here
much shorter than in the sterile leaf, and the pinnules, or smaller

342

ECOLOG

divisions of the pinnae, are inrolled into little spherical masses
which lie close on the side of the pinnae. If we unroll one of
these pinnules we find that there are several fruit dots within
protected by this roll. In fact when the spores are mature these

Fig. 446.
Sensitive fern ; one fertile leaf nearly changed to vegetative leaf.

pinnules open somewhat, so that the spores may be dissemi-
nated.

There is very little green color in these fertile leaves, and
what green surface there is is very small compared with that of
the broad expanse of the sterile leaves. So here there is practi-
cally a complete division of labor between these two kinds of

DIMORPHISM OF FERNS.

343

leaves, the general plan of which is the same, and we recognize
each as being a leaf.

626. Transformation of the fertile leaves of onoclea to
sterile ones. — It is not a very rare thing to find plants of the
sensitive fern which show intermediate conditions of the sterile
and the fertile leaf. A number of years ago it was thought by
some that this represented a different species, but now it is known

Fig. 447.
Sensitive fern, showing one vegetative leaf and two sporophylls completely transformed.

that these intermediate forms are partly transformed fertile leaves.
It is a very easy matter in the case of the sensitive fern to pro-
duce these transformations by experiment. If one in the spring,
when the sterile leaves attain a height of 12 to 16 cm (8-10
inches), cuts them away, and again when they have a second
time reached the same height, some of the fruiting leaves which
develop later will be transformed. A few years ago I cut off the

344

ECO LOG Y.

sterile leaves from quite a large patch of the sensitive fern, once
in May, and again in June. In July, when the fertile leaves
were appearing above the ground, many of them were changed
partly or completely into sterile leaves. In all some thirty plants

Fig. 448.
Normal and transformed sporophyll of sensitive fern.

showed these transformations, so that every conceivable gradation
was obtained between the two kinds of leaves.

627. It is quite interesting to note the form of these changed
leaves carefully, to see how this change has affected the pinnje
and the sporangia. We note that the tip of the leaf as well as
the tips of all the pinrue are more expanded than the basal por-

DIMORPHISM OF FERNS. 345

tions of the same. This is due to the fact that the tip of the
leaf develops later than the basal portions. At the time the
stimulus, to the change in the development of the fertile leaves
reached them they were partly formed, that is the basal parts of
the fertile leaves were more or less developed and fixed and
could not change. Those portions of the leaf, however, which
were not yet completely formed, under this stimulus, or through
correlation of growth, are incited to vegetative growth, and ex-
pand more or less completely into vegetative leaves.

628. The sporangia decrease as the fertile leaf expands.—
If we now examine the sporangia on the successive pinnae of a
partly transformed leaf we find that in case the lower pinnae are
not changed at all, the sporangia are normal. But as we pass to
the pinnae which show increasing changes, that is those which are
more and more expanded, we see that the number of sporangia
decrease, and many of them are sterile, that is they bear no
spores. Farther up there are only rudiments of sporangia, until
on the more expanded pinnae sporangia are no longer formed,
but one may still see traces of the indusium. On some of the
changed leaves the only evidences that the leaf began once to
form a fertile leaf are the traces of these indusia. In some of
these cases the transformed leaf was even larger than the sterile
leaf.

629. The ostrich fern. — Similar changes were also produced
in the case of the ostrich fern, and in fig. 448 is shown at the
left a normal fertile leaf, then one partly changed, and at the
right one completely transformed.

630. Dimorphism in tropical ferns. — Very interesting forms
of dimorphism are seen in some of the tropical ferns. One of
these is often seen growing in plant conservatories, and is known
as the staghorn fern (Platy cerium alcicorne). This in nature
grows attached to the trunks of quite large trees at considerable
elevations on the tree, sometimes surrounding the tree with a
massive growth. One kind of leaf, which may be either fertile
or sterile, is narrow, and branched in a peculiar manner, so that
it resembles somewhat the branching of the horn of a stag

346

ECOLOG Y.

Below these are other leaves which are different in form and
sterile. These leaves are broad and hug closely around the roots
and bases of the other leaves. Here they serve to catch and

Fig. 449.

Ostrich fern, showing one normal sporophyll, one partly transformed, and one completely
transformed.

retain moisture, and they also catch leaves and other vegetable
matter which falls from the trees. In this position the leaves
decay and then serve as food for tfie fern.

CHAPTER XLIX.

FORMATION OF EARLY SPRING FLOWERS.

631. Trillium. — As this white flower with its setting of green
sepals is glinting to us out of copses and woodland like so many
new fairies, few of us realize the long task which it has already
begun in the silent depths of the soil in order that it may suddenly
blossom again in season, when springtime returns. If we re-
move the old scales where the flowering stem joins the root-stock,
we will see a pointed, conical, white bud, which is to develop
into the next season's leafy plant and blossom. From June to
August the new leaves and flower are slowly forming, protected
by several overlapping, thick, whitish, soft scales, which form a
conical roof to keep out water, and to protect against too sudden
changes in cold during the autumn and winter season. In Sep-
tember we find that leaves and sepals are well formed and green,
the petals are already white, and within are the six stamens and
the angular pistil, all well formed. Where the sun reaches these
copses and warms the soil well in autumn, sometimes the stamens
are yellowish as early as September or October from the already
formed pollen. In the cooler shades the pollen is not yet formed
and the stamens remain whitish in color. But with the first onset
of warm weather in the spring, or on warm days in the winter,
before the flower bud lifts its head from its long winter sleep,
snugly ensconced among the fallen leaves or spongy humus, the
pollen quickly forms. Now all the plant has to do is to erect
its standard, bearing aloft the opening blossom.

632. The ovules, begun in the autumn, are now being com-
pleted, pollenation takes place, and later fertilization, and the
embryo begins to form in June. The pure white flowers soon

347

348

ECO LOG Y.

EARLY SPRING FLOWERS. 349

change to pinkish, the first evidence of decline. Finally they
wither, and during the summer the fruit and seed are formed on
the old flower stem, while the secret formative processes of the
new blossoms are going on anew.

633. The adder-tongue (erythronium) comes out early in
the spring to catch the sunlight gleaming through rifts in the
woodland. It is not so forbidding as its name or its " darting"
style would suggest. The rich color of its curved petals nodding
from the fork of the variegated leaves lends cheer and brightness
to the gray carpet of forest leaves. We are apt to associate the
formation of the flower with the early springtime. But after the
flower perishes, the bulb, deep in the soil, slowly builds the next
season's flower, which is kept through the autumn and winter,
much of the time encased in ice, waiting for springtime that it
may rise and unfold.

634. Indian-turnip. — The "Indian-turnip," or " jack-in-the-
pulpit" (Arisaema triphyllum), loves the cool, shady, rich, allu-
vial soil of low grounds, or along streams, or on moist hillsides.
A group of the jacks is shown in figure 45 7 as they occur in the
rich soil on dripping rocks in one of our glens. At their feet is
a carpet of moss. Often the violet sits humbly underneath its
spreading three-parted leaves. The thin, strap-shaped spathe,
unfolded at its base, bends gracefully over the spadix, the sterile
end of which stands solitary in the pulpit thus formed. The
flowers are very much reduced, and the plants are " dimorphic "
usually.

635. Female plants. — The large plants usually bear the pistil-
late flowers, which are clustered around the base of the spadix,
each flower consisting of a single pistil, oval in form, terminat-
ing in a brush-like stigma. The stigma consists of numerous
spreading, delicate hairs. The open cavity of the short style is
hairy also, and a brush of hairs extends into the cavity of the ovary.
Into this brush of internal hairs the necks of the several ovules
crowd their way to the base of the style near its opening. Even
when the stigma is not pollenated the ovary continues to grow in
size, and the stigmatic brush remains fresh for a long time.

35° ECOLOGY.

636. Male plants. — Excepting some of the intermediate sizes,
one can usually select on sight the male and female plants. The
smaller ones which have a spathe are nearly all male and bear a
single leaf, though a few have two leaves. The male flowers are
also clustered at the base of the spadix, and are very much
reduced. Each flower consists only of stamens, and singularly
the stamens of each flower are joined into one compound stamen,
the anther-sacs forming rounded lobes at the end of the short
consolidated filaments.

637. In some plants both male and female flowers occur on a
single spadix, the lower flowers being female, while the upper
ones are male. The larger plants are nearly all female, and many,
though not all, bear two leaves. In this dimorphism of the plant
there is a division of labor apportioned to the destiny and needs
of each, and in direct correspondence with the capacity to supply
nutriment. The staminate flowers, being short-lived, need com-
paratively a small amount of nutriment, and after the escape of
the pollen (dehiscence of the anthers) the spathe dies, while the
leaf remains green to assimilate food for growth of the fleshy short
stem (corm), where also is stored nutriment for the growth in the
autumn and spring when the leaf is dead. The female plants
have more work to do in providing for the growth of the embryo
and seed, in addition to the growth of the corm and next season's
flower. The smaller female j)lants thus sometimes exhaust them-
selves so in seed bearing that the corm becomes small, and the
following season the plant is reduced to a male one.

638. The new roots each year arise from the upper part of the
corm. The stored substances in the base of the corm are used
in the early season's growth, and the old tissue sloughs off as the
new corm is formed above upon its remains.

CHAPTER L.

POLLENATION.

Origin of heterospory, and the necessity for
pollenation.

639. Both kinds of sexual organs on the same prothallium. — In the ferns, as
we have seen, the sexual organs are borne on the prothallium, a small, leaf-like,
heart-shaped body growing in moist situations. In a great many cases both
kinds of sexual organs are borne on the same prothallium. While it is per-
haps not uncommon, in some species, that the egg cell in an archegonium
may be fertilized by a spermatozoid from an antheridium on the same pro-
thallium, it happens many times that it is fertilized by a spermatozoid from
another prothallium. This may be accomplished in several ways. In the
first place antheridia are usually found much earlier on the prothallium than
are the archegonia. When these antheridia are ripe, the spermatozoids es-
cape before the archegonia on the same prothallium are mature.

640. Cross fertilization in monoecious prothallia. — By swimming about in
the water or drops of moisture which are at times present in these moist situa-
tions, these spermatozoids may reach and fertilize an egg which is ripe
in an archegonium borne on another and older prothallium. In this way
what is termed cross fertilization is brought about nearly as effectually as if
the prothallia were dioecious, i.e. if the antheridia and archegonia were all
borne on separate prothallia.

641. Tendency toward dioecious prothallia.— In other cases some fern pro-
thallia bear chiefly archegonia, while others bear only antheridia. In these
cases cross fertilization is enforced because of this separation of the sexual
organs on different prothallia. These different prothallia, the male and
female, are largely due to a difference in food supply, as has been clearly
proven by experiment.

612. The two kinds of sexual organs on different prothallia. — In the horse-
tails (equisetum) the separation of the sexual organs on different prothallia has
become quite constant. Although all the spores are alike, so far as we can
determine, some produce small male plants exclusively, while others produce

351

352 ECOLOGY.

large female plants, though in some cases the latter bear also antheridia. It
has been found that when the spores are given but little nutriment they form
male prothallia, and the spores supplied with abundant nutriment form
female prothallia.

643. Permanent separation of sexes by different amounts of nutriment sup-
plied the spores. — This separation of the sexual organs of different prothallia,
which in most of the ferns, and in equisetum, is dependent on the chance
supply of nutriment to the germinating spores, is made certain when we come
to such plants as isoetes and selaginella. Here certain of the spores receive
more nutriment while they are forming than others. In the large sporangia
(macrosporangia) only a few of the cells of the spore-producing tissue form
spores, the remaining cells being dissolved to nourish the growing macro-
spores, which are few in number. In the small sporangia (microsporangia)
all the cells of the spore-producing tissue form spores. Consequently each
one has a less amount of nutriment, and it is very much smaller, a micro-
spore. The sexual nature of the prothallium in selaginella and isoetes, then, is
predetermined in the spores while they are forming on the sporophyte. The
microspores are to produce male prothallia, while the macrospores are to
produce female prothallia.

644. Heterospory. — This production of two kinds of spores by isoetes,
selaginella, and some of the other fern plants is heterospory, or such plants
are said to be hcterosporotis, Heterospory, then, so far as we know from liv-
ing forms, has originated in the fern group. In all the higher plants, in the
gymnospermsandangiosperms, it has been perpetuated, the microspores being
represented by the pollen, while the macrospores are represented by the em.
bryo sac; the male organ of the gymnosperms and angiosperms being the
antherid cell in the pollen or pollen tube, or in some cases perhaps the pollen
grain itself, and the female organ in the angiosperms perhaps reduced to
the egg cell of the embryo sac.

645. In the pteridophytes water serves as the medium for conveying the
sperm cell to the female organ. — In the ferns and their allies, as well as in
the liverworts and mosses, surface water is a necessary medium through
which the generative or sperm cell of the male organ, the spennatozoid, may
reach the germ cell of the female organ. The sperm cell is here motile.
This is true in a large number of cases in the algae, which are mostly aquatic
plants, while in other cases currents of water float the sperm cell to the
female organ.

646. In the higher plants a modification of the prothallium is necessary.
— As we pass to the gymnosperms and angiosperms, however, where the
primitive phase (the gametophyte) of the plants has become dependent solely
on the modern phase (the sporophyte) of the plant, surface water no longer
serves as the medium through which a motile sperm cell re-aches the egg cell
to fertilize it The female prothallium, or macrospore, is, in nearly all

POLLEN A TION : HETEROSPORY. 353

cases, permanently enclosed within the sporangium, so that if there were
motile sperm cells on the outside of the ovary, they could never reach the
egg to fertilize it.

647. But a modification of the microspore, the pollen tube, enables the
sperm cell to reach the egg cell. The tube grows through the nucellus,
or first through the tissues of the ovary, deriving nutriment therefrom.

648. But here an important consideration should not escape us. The pol-
len grains (microspores) must in nearly all cases first reach the pistil, in
order that in the growth of this tube a channel may be formed through which
the generative cell can make its way to the egg cell. The pollen passes from
the anther locule, then, to the stigma of the ovary. This process is termed
pollenation.

Pollenation.

649. Self pollenation, or close pollenation. — Perhaps very few of the ad-
mirers of the pretty blue violet have ever noticed that there are other flowers
than those which appeal to us through the beautiful colors of the petals.
How many have observed that the brightly colored flowers of the blue violet
rarely " set fruit" ? Underneath the soil or debris at the foot of the plant
are smaller flowers on shorter, curved stalks, which do not open. When the
anthers dehisce, they are lying close upon the stigma of the ovary, and the
pollen is deposited directly upon the stigma of the same flower. This
method of pollenation is self pollenation, or close pollenaliori. These small,
closed flowers of the violet have been termed " cleistogamous, " because they
are pollenated while the flower is closed, and fertilization takes place as a
result.

But self pollenation takes place in the case of some open flowers. In some
cases it takes place by chance, and in other cases by such movements of the
stamens, or of the flower at the time of the dehiscence of the pollen, that it
is quite certainly deposited upon the stigma of the same flower.

650. Wind pollenation. — The pine is an example of wind pollenated flowers.
Since the pollen floats in the air or is carried by the "wind," such flowers
are anemophilous . Other anemophilous flowers are found in other conifers,
in grasses, sedges, many of the ament-bearing trees, and other dicotyledons.
Such plants produce an abundance of pollen and always in the form of
"dust," so that the particles readily separate and are borne on the wind.

651. Pollenation by insects. — A large number of the plants which we have
noted as being anemophilous are monoecious or dioecious, i.e. the stamens
and pistils are borne in separate flowers. The two kinds of flowers thus formed,
the male and the female, are borne either on the same individual (monoe-
cious) or on different individuals (dioecious). In such cases cross pollenation,

354

ECOLOG F.

i.e. the pollenation of the pistil of one flower by pollen from another, is
sure to take place, if it is pollenated at all. Even in monrecious plants cross
pollenation often takes place between flowers of different individuals, so that

Fig. 451-

Viola cucullata; blue flowers above, cleistogamous flowers smaller and curved below.
Section of pistil at right.

more widely different stocks are united in the fertilized egg, and the strain
is kept more vigorous than if very close or identical strains were united.

652. But there are many flowers in which both stamens and pistils are pres-
ent, and yet in which cross pollenation is accomplished through the agency of
insects.

653. Pollenation of the bluet. — In the pretty bluet the stamens and
styles of the flowers are of different length as shown in figures 452, 453.
The stamens of the long-styled flower are at about the same level as the
stigma of the short-styled flower, while the stamens of the latter are on

POLLEN A TION : HE TEKOSPOR Y.

355

about the same level as the stigma of the former. What does this interesting
relation of the stamens and pistils in the two different flowers mean ? As the
butterfly thrusts its " tongue" down into the tube of the long-styled flower

Fig. 452.
Dichogamous flower of the bluet (Houstonia coerulea), the long-styled form.

for the nectar, some of the pollen will be rubbed off and adhere to it. When
now the butterfly visits a short-styled flower this pollen will be in the right
position to be rubbed off onto the stigma of the short style. The positions of

Fig. 453-
Dichogamous flower of bluet (Houstonia coerulea), the short-styled form.

the long stamens and long style are such that a similar cross pollenation will
be effected.

654. Pollenation of the primrose. — In the primroses, of which we have
examples growing in conservatories, that blossom during the winter, we
have almost identical examples of the beautiful adaptations for cross polle-
nation by insects found in the bluet. The general shape of the corolla is

356 ECOLOGY.

the same, but the parts of the flower are in fives, instead of in fours as in
the bluet. While the pollen of the .short-styled primulas sometimes must
fall on the stigma of the same flower, Darwin has found that such pollen is

Fig- 454-
Dichogamous flowers of primula.

not so potent on the stigma of its own flower as on that of another, an ad-
ditional provision which tends to necessitate cross pollenation.

In the case of some varieties of pear trees, as the bartlett, it has been
found that the flowers remain largely sterile not only to their own pollen, or
pollen of the flowers on the same tree, but to all flowers of that variety.
However, they become fertile if cross pollenated from a different variety of
pear.

655. Pollenation of the skunk's cabbage. — In many other flowers cross
pollenation is brought about through the agency of insects, where there is a
difference in time of the maturing of the stamens and pistils of the same
flower. The skunk's cabbage (Sphathyema foetida), though repulsive on
account of its fetid odor, is nevertheless a very interesting plant to study for
several reasons. Early in the spring, before the leaves appear, and in many
cases as soon as the frost is out of the hard ground, the hooked beak of the
large fleshy spathe of this plant pushes its way through the soil.

If we cut away one side of the spathe as shown in fig. 456 we shall have
the flowering spadix brought closely to view. In this spadix the pistil of
each crowded flower has pushed its style through between the plates of
armor formed by the converging ends of the sepals, and stands out alone
with the brush-like stigma ready for pollenation, while the stamens of all the
flowers of this spadix are yet hidden beneath. The insects which pass from
the spadix of one plant to another will, in crawling over the projecting
stigmas, rub off some of the pollen which has been caught while visiting a
plant where the stamens are scattering their pollen. In this way cross pollen^
ation is brought about. Such flowers, in which the stigma is prepared

POLLEN A 7' JON ; HE l^EROSPOR Y.

357

*'ig- 455-
Skunk's cabbage.

Fig. 456.
Proterogyny in skunk's cabbage. (Photograph by the author.)

358

POLLEN A TION : HE TEROSPOR Y.

359

Fig. 457-
Skunk's cabbage ; upper flowers proterandrous, lower ones proterogynous.

360 ECO LOG V.

for pollenation before the anthers of the same flower are ripe, are protcr-
ogynous.

656. Now if we observe the spadix of another plant we may see a condi-
tion of things similar to that shown in fig. 457. In the flowers in the upper
part of the spadix here the anthers are wedging their way through between
the armor-like plates formed by the sepals, while the styles of the same
flowers are still beneath, and the stigmas are not ready for pollenation. Such
flowers are proterandrous, that is, the anthers are ripe before the stigmas of
the same flowers are ready for pollenation. In this spadix the upper flowers
are proterandrous, while the lower ones are proterogynous, so that it might
happen here that the lower flowers would be pollenated by the pollen falling
on them from the stamens of the upper flowers. This would be cross pol-
lenation so far as the flowers are concerned, but not so far as the plants are
concerned. In some individuals, however, we find all the flowers proter-
androus.

657. Spiders have discovered this curious relation of the flowers and in-
sects.— On several different occasions, while studying the adaptations of the
flowers of the skunk's cabbage for cross pollenation, I was interested to find
that the spiders long ago had discovered something of the kind, for they
spread their nets here to catch the unwary but useful insects. I have not
seen the net spread over the opening in the spathe, but it is spread over the
spadix within, reaching from tip to tip of either the stigmas, or stamens, or
both. Behind the spadix crouches the spider-trapper. The insect crawls
over the edge of the spadix, and plunges unsuspectingly into the dimly
lighted chamber below, where it becomes entangled in the meshes of the
net.

Flowers in which the ripening of the anthers and maturing of the stigmas
occur at different times are also said to be dichogamous.

658. Pollenation of jack-in the pulpit. — The jack-in-the-pulpit (Arisaema
triphyllum) has made greater advance in the art of enforcing cross pollena-
tion. The larger number of plants here are, as we have found, dioecious, the
staminate flowers being on the spadix of one plant, while the pistillate flowers
are on the spadix of another. In a few plants, however, we find both
female and male flowers on the same spadix.

659. The pretty bellflower (Campanula rotundifolia) is dichogamous
and proterandrous (fig. 459). Many of the composites are also dichoga-
mous.

660. Pollenation of orchids. — But some of the most marvellous adapta-
tions for cross pollenation by insects are found in the orchids, or members of
the orchis family. The larger number of the members of this family grow
in the tropics. Many of these in the forests are supported in lofty trees
where they arc brought near the sunlight, and such are called "epiphytes."
A number of species of orchids are distributed in temperate regions.

POLLE NATION: HETEROSPORY. 361

661. Cypripedium or lady-slipper.— One species of the lady-slipper is
shown in fig. 465. The labellum in this genus is shaped like a shoe, as one

Fig. 458-
A group of jacks.

can see by the section of the flower in fig. 465 . The stigma is situated at st,
while the anther is situated at a, upon the style. The insect enters about
the middle of the boat-shaped labellum. In going out it passes up and out

362

ECOLOGY.

at the end near the flower stalk. In doing this it passes the stigma first and
the anther last, rubbing against Ixith. The pollen caught on the head of

Fig- 459-

Proterandry in the bell-flower (campanula). Left figure shows the svngencecious stamens
surrounding the immature style and stigma. Middle figure shows the immature stigma being
pushed through the tube and brushing out the pollen ; while in the right-hand figure, after
the pollen has disappeared, the lobes of the stigma open out to receive pollen from another
flower.

the insect, will not touch the stigma of the same flower, but will be in posi-
tion to come in contact with the stigma of the next flower visited.

662. Epipactis. — In epipactis, shown in fig. 466, the action is similar to
that of the blue iris.

Fig. 460.

Kalmia latifolia, showing position of anthers before insect visits, and at the right the
scattering of the pollen when disturbed by insects. Middle figure section of flower.

663. In some of the tropical orchids the pollinia are set free when the insect
touches a certain part of the flower, and are thrown in such a way that the
disk of the pollinium strikes the insect's head and stands upright. By the
time the insect reaches another flower the pollinium has bent downward suffi-

POLLEN A TION : HE TEROSPOR Y.

ciently to strike against the stigma when the insect alights on the labellum.
In the mountains of North Carolina I have seen a beautiful little orchid, in
which, if one touches a certain part of the flower with a lead-pencil or other
suitable object, the pollinium is set free suddenly, turns a complete somer-
sault in the air, and lands with the disk sticking to the pencil. Many of the

Fig. 46!.
Spray of leaves and flowers
of cytisus.

orchids grown in conservatories can be used to demonstrate some of these
peculiar mechanisms.

664. Pollenation of the canna. — In the study of some of the marvellous
adaptations of flowers for cross pollenation one is led to inquire if, after all,
plants are not intelligent beings, instead of mere automatons which respond

Fig. 462.
Flower of cytisus grown in conservatory.

Same flower scattering poller.

to various sorts of stimuli. No plant has puzzled me so much in this respect
as the canna, and any one will be well repaid for a study of recently opened
flowers, even though it may be necessary to rise early in the morning to
unravel the mystery, before bees or the wind have irritated the labellum.
The canna flower is a bewildering maze of petals and petal-like members.

ECOLOGY.

The calyx is green, adherent to the ovary, and the limb divides into three,
lanceolate lobes. The petals are obovate and spreading, while the stamens
have all changed to petal-like members, called staminodia. Only one still
shows its stamen origin, since the anther is seen at one side, while the fila-
ment is expanded laterally and upwards to form the staminodhint.

Fig. 463.

Spartium, showing the dusting of the pollen througli the opening keels on the under side
of an insect. (From Kerner and Oliver.;

665. The ovary has three locules, and the three styles are usually united
into a long, thin* strap-shaped style, as seen in the figure, though in some
cases three, nearly distinct, filamentous styles are present. The end of this
strap-shaped style has a peculiar curve en one side, the outline being some-

POLLEN A TION : HE TEKOSPOK Y.

times like a long narrow letter S. It is on the end of this style, and along
the crest of this curve, that the stigmatic surface lies, so that the pollen

Fig. 465.

Section of flower of cypripedium. st,
stigma ; <i, at the left stamen. The insect
enters the labellum at the center, passes
under and against the stigma, and Out
through the opening />, where it rubs
against the pollen. In passing through
another flower this pollen is rubbed off
on the stigma.

must be deposited on the stigmatic end or margin
in order that fertilization may take place.

666. If we open carefully canna-flower buds
which are nearly ready to open naturally, by
unwrapping the folded petals and staminodia, we will see the anther-bearing

Fig. 464.
Cypripedium.

Fig. 466.

Epipactis with portion of perianth removed to show details. /, labellum ; st, stigma ; r,
rostellum ; /, polfinium. When the insect approaches the flower its head strikes the disk
of the pollinium and pulls the p^ollinium out. At this time the pollinium stands up out of the
way of the stigma. By the time the insect moves to another flower the pollinia have moved
downward so that they are in position to strike the stigma and leave the pollen. At the
right is the head of a bee, with two pollinia (a> attached.

366

ECO LOG Y.

staminodium is so wrapped around the flattened style that the anther lies

closely pressed against the face of the style, near the margin opposite that

on which the stigma lies.

667- The walls of the anther locules which lie against the style become

changed to a sticky substance for their entire length, so that they cling

firmly to the surface of the style
and also to the mass of pollen
within the locules. The result is
that when the flower opens, and
this staminodium unwraps itself
from the embrace of the style, the
mass of pollen is left there de-
posited, while the empty anther is
turned around to one side.

668. Why does the flower de-
posit its own pollen on the style ?
Some have regarded this as the act
of pollenation, and have concluded,
therefore, that cannas are neces-
sarily self pollenated, and that
cross pollenation does not take
place. But why is there such evi-
dent care to deposit the pollen on

. Fi&- 467- the side of the style away from the

Canna flowers with the perianth removed to . . • -> -rr • • i

show the depositing of the pollen of the style by stlgmatlC margin ? If we Visit the

cannas some morning, when a

number of the flowers have just opened, and the bumblebees are humming
around seeking for nectar, we may be able to unlock the secret.

669. We see that in a recently opened canna flower, the petal which
directly face^ the style in front stands upward quite close to it, so that the
flower now is somewhat funnelshaped. This front petal is the labellum, and
is the landing place for the bumblebee as he alights on the flower. Here
he comes humming along and alights on the labellum with his head so close
to the style that it touches it. But just the instant that the bee attempts to
crowd down in the flower the labellum suddenly bends downward, as shown
in fig. 468. In so doing the head of the bumblebee scrapes againsj; the
pollen, bearing some of it off. Now while the bee is sipping the nectar it is
too far below the stigma to deposit any pollen on the latter. When the bum-
blebee flies to another newly opened flower, as it alights, some of the pollen
of the former flower is brushed on the stigma.

670. One can easily demonstrate the sensitiveness of the labellum of
recently opened canna flowers, if the labellum has not already moved down
in response to some stimulus. Take a lead-pencil, or a knife blade, or even

POLL EN A 7 'ION : HE TEROSPOR Y.

367

the finger, and touch the upper surface of the labellum by thrusting it
between the latter and the style. The labellum curves quickly downward.

671. Sometimes the bumblebees, after sipping the nectar, will crawl up
over the style in a blundering manner. In this way the flower may be pol-

Fig. 468.
Pollenation of the canna flower by bumblebee.

Canna flower. Pollen on style, sta-
men at left.

lenated with its own pollen, which is equivalent to self pollenation. Un-
doubtedly self pollenation does take place often in flowers which are adapted,
to a greater or less degree, for cross pollenation by insects.

CHAPTER LI.

SEED DISTRIBUTION.

672. Means for dissemination of seeds. — During late summer or autumn
a walk in the woods or afield often convinces us of the perfection and variety
of means with which plants are provided for the dissemination of their
seeds, especially when we discover that several hundred seeds or fruits of
different plants are stealing a ride at our expense anci annoyance. The hooks
and barbs on various seed-pods catch into the hairs of passing animals and
the seeds may thus be transported
considerable distances. Among the
plants familiar to us, which have such
contrivances for unlawfully gaining
transportation, are the beggar-ticks
or stick tights, or sometimes called

Fig. 469.

Bur of bidens or bur-marigold, show-
ing barbed seeds.

Fig. 470.

Seed pod of tick-treefoil (desmodium) ; at the
right some of the hooks greatly magnified.

bur-marigold (bidens), the tick-treefoil (desmodium), or cockle-bur (xanthi-
um), and burdock (arctium).

673. Other plants like some of the sedges, etc., living on the margins of
streams and of lakes, have seeds which are provided with floats. The wind
or the flowing of the water transports them often to distant points.

368

SEED DISTRIBUTION.

369

674. Many plants possess attractive devices, and offer a substantial
reward, as a price for the distribution of their seeds. Fruits and berries are
devoured by birds and other animals ; the seeds within, often passing un-
harmed, may be carried long distances. Starchy and albuminous seeds and

Fig. 47'
Seeds of geum showing the booklets where the end of the style is kneed.

grains are also devoured, and while many such seeds are destroyed, others
are not injured, and finally are lodged in suitable places for growth, often
remote from the original locality. Thus animals willingly or unwillingly
become agents in the dissemination of plants over the earth. Man in the
development of commerce is often responsible for the wide distribution of
harmful as well as beneficial species.

675. Other plants are more independent, and mechanisms are employed
for violently ejecting seeds from the pod or fruit. The unequal tension of
the pods of the common vetch (Vicia sativa) when drying causes the valves
to contract unequally, and on a dry summer day the valves twist and pull in
opposite directions until they suddenly snap apart, and the seeds are thrown
forcibly for some distance. In the impatiens, or touch-me-not as it is better
known, when the pods are ripe, often the least touch, or a pinch, or jar, sets
the five valves free, they coil up suddenly, and the small seeds are whisked
for several yards in all directions. During autumn, on dry days, the pods
of the witch hazel contract unequally, and the valves are suddenly spread
apart, when the seeds, as from a catapult, are hurled away.

Other plants have learned how useful the " wind " may be if the seeds are
provided with "floats," "parachutes," or winged devices which buoy them

370

ECOLOGY.

up as they are whirled along, often miles away. In late spring or early
summer the pods of the willow burst open, exposing the seeds, each with a
tuft of white hairs making a mass of soft down. As the delicate hairs dry,

Fig. 472.

Touch-me-not (Impatiens fulva) ; side and front view of flower below ; above unopened
pod, and opening to scatter the seed.

they straighten out in a loose spreading tuft, which frees the individual seeds
from the compact mass. Here they are caught by currents of air and float
off singly or in small clouds.

676. The prickly lettuce. — In late summer or early autumn the seeds of
the prickly lettuce (Lactuca scariola) are caught up from the roadsides by
the winds, and carried to fields where they are unbidden as well as unwel-
come guests. This plant is shown in fig. 473.

677. The wild lettuce. — A related species, the wild lettuce (Lactuca cana-
densis) occurs on roadsides and in the borders of fields, and is about one
meter in height. The heads of small yellow or purple flowers are arranged
in a loose or branching panicle. The flowers are rather inconspicuous, the
rays projecting but little above the apex of the enveloping involucral bracts,
which closely press together, forming a flower-head more or less flask-
shaped.

At the time of flowering the involucral bracts spread somewhat at the
apex, and the tips of the flowers are a little more prominent. As the flowers
then wither, the bracts press closely together again and the head is closed.
As the seeds ripen the bracts die, and in drying bend outward and down-
ward, hugging the flower stem below, or they fall away. The seeds are

SEED DISTRIBUTION.

thus exposed. The dark brown achenes stand over the surface of the recep-
tacle, each one tipped with the long slender beak of the ovary. The "pap-
pus," which is so abundant in many of the plants belonging to the composite
family, forms here a
pencil-like tuft at the
tip of this long beak.
As the involucral bracts
dry and curve down-
ward, the pappus also
dries, and in doing so
bends downward and
stands outward, brist-
ling like the spokes of
a fairy wheel. It is an
interesting coincidence
that this takes place
simultaneously with
the pappus of all the
seeds of a head, so
that the ends of the
pappus bristles of ad-
joining seeds meet,
forming a many-sided
dome of a delicate and
beautiful texture. This
causes the beaks of the
achenes to be crowded
apart, and with the
leverage thus brought to
bear upon the achenes
they are pried off the
receptacle. They are
thus in a position to
be wafted away by the
gentlest zephyr, and
they go sailing away
on the wind like a
miniature parachute.
As they come slowly

to the ground the seed . Fig' 473>.

Lactuca scanola.
is thus carefully low-
ered first, so that it touches the ground in a position for the end which
contains the root of the embryo to come in contac.t with the soil.

372

ECOLOGY.

678. The milkweed, or silkweed. — The common milkweed, or silkweed
(Asclepias cornuti), so abundant in rich grounds, is attractive not only

Fig. 474.
Milkweed (Asclepias cornuti) ; dissemination of seed.

because of the peculiar pendent flower clusters, but also for the beautiful
floats with which it sends its seeds skyward, during a puff of wind, to finally
lodge on the earth.

679. The large boat-shaped, tapering pods, in late autumn, are packed
with oval, flattened, brownish seeds, which overlap each other in rows like
shingles on a roof. These make a pretty picture as the pod in drying splits
along the suture on the convex side, and exposes them to view. The silky
tufts of numerous long, delicate white hairs on the inner end of each seed,
in drying, bristle out, and thus lift the seeds out of their enclosure, where
they are lifted like fairy balloons, buoyant as vapor, they go bearing the
precious burden of an embryo plant, which is to take its place as a contest-
ant in the battle for existence.

680. The virgin's bower. — The virgin's bower (Clematis virginiana), too,
clambering over fence and shrub, makes a show cf having transformed its

SEED D IS 7 *KJB U TION.

373

exquisite white flower clusters into grayish-white puffs, which scatter in the
autumn gusts into hundreds of arrow-headed, spiral plumes. The achenes

Fig- 475-
Seed distribution of virgin's bower ^clematis).

have plumose styles, and the spiral form of the plume gives a curious twist
to the falling seed (fig. 474).

CHAPTER LII.
STRUGGLE FOR OCCUPATION OF LAND.

681. Retention of made soil. — In the struggle of plants for
existence, there are a number of species which stand ready to
rush in where new opportunities present themselves by changed
conditions, or by newly made soil. The permanent drainage of
ponds or marshes brings changed conditions, and the flora there

Fig. 476.
Made soil at mouth of stream, being overgrown by plants. Ithaca, N. Y.

undergoes remarkable transformations. The deposits of the
washings of streams in protected places along the shores, or at
their mouths, where deltas or lateral plateaus are made by the
accumulations of soil scoured off the banks of the stream, or
washed off the fields during rains, make new ground. With such
banks of newly made ground are deposited seeds carried along
with the soil, or dropped there by the wind, by birds, or other
agencies of seed distribution.

682. Figure 476 is from a photograph taken at the mouth of
one of the streams emptying into Cayuga Lake. At the left is

374

OCCUPATION OF LAND.

I

I

ECOLOG V.

a newly made bank of soil. The species of bidens were here
among the first to start in the soft black mud. These are fol-
lowed later by grasses, by species of the arrowhead (sagittaria),
pickerel-weed (pontederia), etc. The loose soil becomes per-
meated by a mass of roots, and year by year becomes more firm.

683. Vegetation of sand dunes. — Along the sandy beaches
of lakes, or of the ocean, drift piles of the fine sand are formed,
which often are moved onward by the wind. The surface parti-
cles are moved onward to the leeward of the drift, and so on.
The form and location of the sand dune gradually changes.
Such drifts sometimes slowly but surely march along over soil
where a rich vegetation grows, and over valuable land. Even
on these sand dunes there are certain plants which can gain a
foothold and grow. When a sufficient number obtain a foothold
in such places they retain the sand and prevent the movement
of the dune.

684. Reforestation of lands. — When by the action of fire or
wind, or through the agency of man, portions of forests are
partially or completely destroyed, a new set of conditions is pre-
sented over these areas. One of the most important is that light
is admitted where before towering trees permitted but a limited
and characteristic undergrowth to remain. Hundreds of forms,
which for years have been dormant, are now awakened from
their long sleep, and new and recent importations of seeds which
are constantly rushing in spring into existence to fill the gap,
multiply their numbers, and make more sure the perpetuation
of their kind.

685. The earliest to appear are not always the ones to endure
the longest, and a battle royal takes place during years for su-
premacy. The weaker ones are gradually overcome by the more
vigorous, and a new crop of trees, which often springs up in such
places, finally usurps again the domain, in the name of the same
or of a different species.

686. Domestic plants protected by man occupy cultivated
fields. When cultivation ceases, or the crop is removed, or the
fields are neglected, hundreds of species of feral plants, which

OCCUPATION' OF LAND.

377

are constantly springing up, now flourish, bear seed, and take
more or less complete possession of the soil. Impoverished land,
abandoned by man, becomes nurtured by nature. Weeds, grass,
flowers, spring up in great variety often. Some can thrive but
little better than the abandoned crops, while others, peculiarly
fitted because of one or another adapted structure or habit, flour-

Fig. 478.

Abandoned field, in Alabama, growing up to broom-sedge and trees. (Photograph by Prof.
P. H. Mell.)

ish. Crab-grass and other low-growing plants often cover and
protect the soil from the direct rays of the sun, and thus conserve
moisture. The clovers which spring up here and there, by the
aid of the minute organisms in their roots, gather nitrogen.
The melilotus, the passion flower, and other deep-rooted plants
reach down to virgin soil and lift up plant food. Each year
plant remains are added to, and enrich, the soil. In some places
grasses, like the broom-sedge (andropogon) succeed the weeds,
and a turf is formed.

687. Seeds of trees in the mean time find lodgment. During
the first few years of their growth they are protected by the

ECO LOG Y.

herbaceous annuals or perennials. In time they rise above
these. Each year adds to their height and spread of limb, until
eventually forest again stands where it was removed years before.
In the Piedmont section of the Southern States such a view as is

Fig. 479.
Abandoned field, Alabama, self reforested by pines. (Photograph by Prof. P. H. Mell.)

presented in fig. 478 represents how abandoned fields are taken
by the broom-sedge, to be followed later by pines, and later
by a forest as shown in fig. 479.

688. In New York State many abandoned hillsides are being
reforested slowly by nature with the white pine. Fig. 480 rep-
resents a group of self-sown pines ranging from three to six

OCCUPATION OF LAND.

379

meters high (10-20 feet), growing up in an abandoned orchard
near Ithaca. In this reforestation of impoverished lands, man
can give great assistance by timely and proper planting.

Fig. 480.

Self-sown white pine in abandoned orchard ; trees 9-20 years old. Near Ithaca. (Photo-
graph by the author.)

689. Beauty of old fields. — During one season from my win-
dow I beheld a marvellously beautiful sight. The scene was
located in a portion of an old field on a hillside, in a rapidly
growing part of the city. New buildings had sprung up all

380 ECOLOG y.

around, and this was waiting sale or improvement. But there
were innumerable seeds of a great variety of plants in that vacant
lot. They sprang into growth to occupy the land, and a great
tangle of luxuriant vegetation was the result. Burdock, tower-
ing pigweeds, grasses, beggar-ticks, mullein, St. John's wort,
masses of giant goldenrods, blue-rayed asters, occupied every
inch of the ground in a grand medley of kind and color.
Through this mass, briers and blackberry bushes pushed their
thorny sprays, laying hold on you if you attempted entrance.
Children plucked the beautiful flowers, but the flowers they
cared not, neither took they thought for the future day when
they must give way under the influence of man to stone walls
and a plain greensward, so joyous were they in the mere
thought of existence and radiant beauty.

CHAPTER LIII.

SOIL FORMATION IN ROCKY REGIONS AND
IN MOORS.

Lichens.

690. Many of the lichens are small and inconspicuous. They
often appear only as bits of color on tree trunk or rock. One
of the conspicuous ones on stones lying on the ground is the
grayish-green thallus of Parmelia contigua (fig. 481 ). Its pretty,
flattened, forking lobes radiate in all directions, advancing at the
margin, and covering year by year more and more of the stone
surface. Numerous cup-shaped fruit bodies (apothecia) are scat-
tered over the central area. The thallus clings closely to the rock
surface by numerous holdfasts from the under side, which pene-
trate minute crevices of the rock. The lichen derives its food
from the air and water. By its closely fitting habit it retains in
contact with the rock certain acids formed by the plant in
growth, or in the decay of the older parts, which slowly disinte-
grate the surface ot the rock. These disintegrated particles of
the rock, mingled with the lichen debris, add to the soil in those
localities.

691. Lichens are among the pioneers in soil making.—
The habit which many lichens have of flourishing on the bare
rocks fits them to be among the pioneers in the formation of soil
in rocky regions which have recently become bared of ice or
snow. The retreat of glaciers from peaks long scoured by ice,
or the unloading of broken rocks along its melting edge, exposes
the rocks to the weathering action of the different elements. Now
the lichens lay hold on them and invest them with fantastic

382

ECO LOG V.

figures of varied color. Disintegrating rock, debris of plants
and animals, join to form the virgin soil. Certain of the blue-
green algae, as well as some of the mosses, are able to gain a
foothold on rocks and assist in this process of soil formation.

Fig. 481.
Rock lichen (Parmelia contigua).

A view of rocks thrown down by the melting and retreating edge
of a glacier in Greenland is shown in fig. 481. These rocks at
the time the photograph was taken had no plant life on them.
At other places in the vicinity of this glacier, rocks longer uncov-
ered by ice were being covered by plant life. One of the green-
land rock lichens are shown in fig. 483.

SOIL FORMATION: ROCK: DISINTEGRATION. 383

692. Other plants of rocky regions. — Certain of the higher
plants also find means of attachment to the bare rocks of the
arctic and mountain regions. The roots penetrate into narrow
crevices in the rock, and are able to draw on the water which is

Fig. 482.
Edge of glacier in Greenland, showing freshly deposited rocks. (From Prof. R. S. Tarr.)

elevated by capillarity. Such plants, however, which live on
bare rocks, whether in the arctic or in mountain regions, have
leaves which enable them to endure long periods of drought.
These plants have either succulent leaves like certain of the stone-

3^4

ECO LOG Y.

crops (sedum), or small thick leaves which are closely overlapped
as in the Saxifraga oppositifolia.

693. Few of us, unfortunately, can make the trip to the arctic
regions to study these interesting plants which play such an im-
portant role in the economy of nature. Rocky places, however,

Fig. 483.
Rock lichen (umbilicaria) from Greenland.

or loose stones are common nearer home. Observation of their
flora, and the means by which such plants derive nutriment, store
moisture, or protect themselves from drought, will well repay out-
door excursions.

694. Filling of ponds by plants. — Not only are plants im-
portant agencies in the formation of soil in rocky regions, they

SOIL FORMATION: MOORS.

385

386 ECOLOGY.

are slowly but surely playing a part in the changes of soil and in
the topography of certain regions. This is very well marked in
the region of small ponds, where the bottom slopes gradually out
to the deeper water in the center. Striking examples are some-
times found where the surface of the country is very broken
or hilly with shallow basins intervening. In what are termed
morainic regions, the scene of the activity of ancient glaciers,
or in the mountainous districts, we have opportunities for study-
ing plant formations, which slowly, to be sure, but nevertheless
certainly, fill in partly or completely these basins, so that the
water is confined to narrow limits, or is entirely replaced by plant
remains in various stages of disintegration, upon which a charac-
teristic flora appears.

695. A plant atoll. — In the morainic regions of central New
York there are some interesting and striking examples of the ef-
fects of plants on the topography of small and shallow basins.
These formations sometimes take the shape of ' ' atolls, ' ' though
plants, and not corals, are the chief agencies in their gradual ev-
olution. Fig. 484 is from a photograph of one of these plant atolls
about 15 miles from Ithaca, N. Y. , along the line of the E. C. &
N. R. R. near a former flag station known as Chicago. The basin
here shown is surrounded by three hills, and is formed by the
union of their bases, thus forming a pond with no outlet.

696. Topography of the atoll moor. — The entire basin was
once a large pond, which has become nearly filled by the growth
of a vegetation characteristic of such regions. Now only a small,
nearly circular, central, pond remains, while entirely around the
edge of the earlier basin is a ditch, in many places with from
3o-6ocm. of water. There is a broad zone of land then lying
between the central pond and the marginal ditch. Just inside of
the ring formed by the ditch is an elevated ring extending all
around, which is higher than any other part of the atoll. On a
portion of this ring grow certain grasses and carices. The soil for
some depth shows a wet peat made up of decaying grasses, carices,
and much peat moss (sphagnum). In some places one element
seems to predominate, and in other cases another element. On

SOIL FORMATION: MOORS. 387

some portions of the outer ring are shrubs one to three meters in
height, and occasionally small trees have gained a foothold.

697. Next inside of this belt is a broad, level zone, with Carex
filiformis, other carices, grasses, with a few dicotyledons. Inter-
mingled are various mosses and much sphagnum. The soil for-
mation underneath contains remains of carices, grasses, and
sphagnum. This intermediate zone is not a homogeneous one.
At certain places are extensive areas in which Carex filiformis
predominates, while in another place another carex, or grasses
predominate.

698. A floating inner zone. — But the innermost zone, that
which borders on the water, is in a large measure made up of the
leather-leaf shrub, cassandra, and is quite homogeneous. The
dense zone of this shrub gives the elevated appearance to the
atoll immediately around the central pond, and the cassandra is
nearly one meter in height, the " ground " being but little above
the level of the water. As one approaches this zone, the ground
yields, and by swinging up and down, waves pass over a consid-
erable area. From this we know that underneath the mat of
living and recent vegetation there is water, or very thin mud, so
that a portion of this zone is " floating."

699. The inner, or cassandra, zone is more unstable, that is
it is all "afloat," though firmly anchored to the intermediate
zone. The roots of the shrubs interlace throughout the zone,
firmly anchoring all parts together, so that the wind cannot break
it up. Between the tufts of the cassandra are often numerous
open places, so that the water or thin mud on which the zone
floats reaches the surface, and one must exercise care in walking
to prevent a disagreeable plunge. No resistance is offered to a
pole two to three meters long in thrusting it down these holes.
Grasses, carices, mosses, sphagnum, and occasionally moor-loving
dicotyledons occur, anchored for the most part about the roots
of the cassandra. Standing at the inner margin of the cassandra
zone, one can see the mud, resembling a black ooze, formed of
the titrated plant remains, which have floated out from the bot-
tom of the older formations. In some places this lies very near

388

ECOLOG Y.

SOIL FORMATION: MOORS. 389

the surface, and then certain aquatic plants like bidens, and
others, find a footing. Upon this black ooze the formation can
continue to encroach upon the central pond. Agitated by the
wind, more and more of the ooze passes outward, so that in time
there is a likelihood that the pond will cease to exist, yielding,
as it has in other places, the right of possession to the conten-
tious vegetation.

700. How was the atoll formed? — In the early formation of
the atoll, it is possible that certain of the water-loving carices and
grasses began to grow some distance (three to four meters) from
the shore, where the water was of a depth suited to their habit.
The stools of these plants gradually came nearer the surface of
the water. As they approach the surface, other plants, not so
strong-rooted, like mosses, sphagnum, etc., find anchorage, and
are also protected to some extent from the direct rays of sunlight.
Partial disintegration of the dead plant parts and mingling with
the soil gradually fills on the inside of the zone, so that the depth
of the water there becomes less. Now the zone of the carices
can be extended inward.

701. The continued growth of the sphagnum and the dying
away of the lower part of the plant add to the bulk of the plant
remains in the zone, and finally quite a firm ground is formed,
shutting off the shallow water near the shore from the deeper
water of the pond. As time goes on other plants enter and
complicate the formation, and even make new ones, as when the
cassandra takes possession.

702. The original pond here was rather oblong, and one end
possibly much shallower than the other, so that it filled in much
more rapidly, leaving the central pond at the east end. Over
a portion of the west end there is an extensive cassandra forma-
tion, with some ledum (labrador tea), but separated from the
circular cassandra zone by an intermediate zone. In this end-
cassandra formation other shrubs, and white pines five to fifteen
years old, are gaining a foothold, and in a quarter of a century
or more, if left undisturbed, one may expect considerable changes
in the flora of this atoll. It is possible that a rise of the water

390

ECOLOGY.

for a number of
years when the
earlier zones were
floating accounts
for the circular ele-
vation and atoll
formation.

703. A black-
spruce moor. — A
somewhat similar
but more advanced
plant formation oc-
curs east of Free-
ville, N. Y., and
about nine miles
distant from Ithaca.
The center of the
basin, which was
perhaps shallower
than the former
one, has become
completely filled,
and all of the cen-
tral formation is
more elevated than
the margin by the
shore of the basin.
All around the mar-
gin in wet weather
the ground is more
or less submerged,
while all the central
portion is so ele-
vated that the nu-
merous stools or
hummocks of

SOIL FORMATION: MOORS. 39 1

grasses uke eriophorum, with its white tufts sparkling in the
sunlight like a firmament of stars, shrubs like cassandra, pyrus,
nemopanthes, etc. , support one in walking above the water which
rises in the intervening spaces. Sphagnum, polytrichum, and
other mosses grow, especially in the stools of the other plants,
where they now are shaded by the larger growth, and in drier
seasons catch the water which trickles down during rain.

Years ago the forest encroached on this formation, and trees of
the hemlock-spruce, black spruce, larch, etc. , of considerable size
gained a footing, first along the margin, then along the more ele-
vated zone n short distance within. The black spruce trees spread
all over the center of the formation, attaining a height of one to
six or eight meters, while the trees of the marginal zone where they
first entered, and the ground is somewhat more elevated, attained
a much greater height.

704. Fall of the trees on the marginal zone when the wind
break was removed. — Thesis large trees of the marginal zone,
though they were rooted to a great extent in loose soil, never-
theless were protected from winds by the forests on the sur-
rounding hills. When, however, these hills on three sides were
cleared for cultivation the wind had full sweep, and many of
the large trees were uprooted by the force of the gales. This
view is supported by the fact that the western hill is still covered
by forest, and large spruce trees of the marginal zone are still
standing, though several were uprooted September, 1896, during
a fierce southeastern gale, the wind from this direction having
full play upon them.

705. Dying of the spruce of the central area. — This re-
moval of the forests from the surrounding hills very likely had
its influence in hastening the melting of the winter snows on the
hills, so that excessive quantities of water from this source rushed
quickly down into the swamp, flooding it at certain seasons
much higher than the normal high-water mark during former
times, when the hills were forest-covered. Also during rains
the water would now rush quickly down into the swamp, flood-
ing it at these times. This greater quantity of water has had its

392

ECOLOG Y.

effect, probably, in causing many of the young spruces over the
center of the formation to die off.

706. This may also have been hastened by fires which would
now more often sweep over the swamp during dry seasons. In
partial evidence of this are many young spruce trees with scars
near the ground where the bark has been destroyed. This gives
admittance to wood-boring insects which farther aid in the proc-

Fig. 487-
Dying black spruce in moor. (Photograph by the author.)

ess of weakening and debilitating the trees. The dying off of
the lower limbs of these marsh spruces suggests both the action
of fire, as well as excessive moisture at times. Many of them
now present only a small convex top of living branches. It is
interesting to observe the gradation in this respect in different
trees.

707. The weird aspect presented by a clump of these dying
young spruce trees is heightened also by the changes in the form
of the branches as they die. The living branches have a graceful
sigmoid sweep with their free ends curving upwards as in many

SOIL FORMATION: MOORS. 393

conifers. As the branches die, the free ends curve downward
more and more, all gradations being presented in a single tree.
A group of such dying spruce trees is shown in fig. 487. Some
have been long dead ; only the knotted, weather-beaten trunks
still remain tottering to their final condition. Others with leaf-
less, dried, sprawling branches go swirling with every wind,
while a few struggle on in the presence of these untoward con-
ditions.

708. Other morainic moors. — In other basins, where the
hills on all sides are still forest-clad, more equable temperature
and moisture conditions are conserved. This permits plants to
.flourish here which in the exposed basins are disappearing from
the formations or only leading a miserable existence. This is
strikingly true of some sphagnum formations. In the atoll for-
mation described the evidence suggests that sphagnum formerly
played a more active part in the evolution of that type of moor
than has been the case since the hills were denuded of their
trees. So also in the spruce moor, sphagnum probably was at
one time a prominent factor in the formation of the early vege-
tation. But excessive drought during certain seasons, and full
exposure to the sun and wind, have served to lessen its influence
and importance. But where protected from the wind, to a large
extent from the heat of the sun, and supplied with a suitable
moisture condition, the sphagnum flourishes. It grows either
alone in shallow water, encroaching more and more on the center
of the basin, or follows after and anchors among water-loving
grasses and carices. In some cases it may thus largely cover
such earlier formations. An examination of the sphagnum
plant shows us how well it is adapted to flourish under such
conditions. The main axis of the plant bears lateral branches
nearly at right angles, but with a graceful downward sweep at
the extremity. These primary lateral branches bear secondary
branches, which arise, usually several, from near the point of
attachment to the main axis. They hang downward, overlap on
those below, and completely cover the main axis or stem. The
leaves of sphagnum are peculiarly adapted for the purpose of

394 ECOLOG Y.

taking up quantities of water. Not all the cells of the leaf are
green, but alternate rows of cells become broadened, lose their

chlorophyll, and their protoplasm
collapses on the inner faces of the -
cell walls in such a way as to form
thickened lines, giving a peculiar
sculpturing effect to them. Perfora-
tions also take place in the walls.
These empty cells absorb large quan-
tities of water, and by capillarity it
is lifted on from one cell to another. •
These pendent branches, then, which
envelop the sphagnum stem, lift
water up from the moist substratum
to supply the leaves and growing
parts of the plant which are at the
upper extremity.

709. Year by year the extension
of the sphagnum increases slowly
upward by growth of the ends of
the individual plants, while the older
portions below die off, partly disin- ,
tegrate, and pass over into the in-
creasing solidity and bulk of the ;
peat. It thus happens sometimes
that the centers of such basins or
moors are more elevated than the
margins, because here a greater
amount of water exists in the depths '
which is pumped up for use by the
Fig. 488. plants themselves. Such a formation

Two fruiting plants of sphagnum. . .

(From Kerner and Oliver.) IS Sometimes Called a "high mOOr.

710. Because of the peculiar topographic features of these
basins, together with the conditions of moisture, etc., changes
in their form are quite readily observed. But no less important
are the influences of plants on soil conditions on the hills, and

SOIL FORMATION- MOORS.

395

in more level areas. Old plant parts, and plant remains, by
decay add to the bulk, fertility, and changing texture and phy-
sical condition of the soil.

Fig. 48y.
Where isoetes grows. A s. ...... inorainic basin near Ithaca. (Photograph by the author.)

711. The bald cypress (Taxodium distichum). — Very char-
acteristic are the formations presented by the forests of the bald
cypress of the South, which grows in swampy or marshy places.
The " knees ' ' on the roots of this cypress make grotesque figures
in the cypress forest. These take the form of upright, columnar
outgrowths, broader at the base or point of attachment to the

396

ECOLOG Y.

horizontal root, and possess a fancied resemblance to a knee.
These knees are said to occur at points on the horizontal root
above and opposite the point where a root branch extends down-
ward into the soft marsh soil. They thus give strength to the

Fig. 490.
Cypress knees, Mississippi. (Photograph by H. von Schrenk.)

horizontal root at the point of attachment of the branch which
penetrates into the soft soil, and during gales they hold these
root branches more rigidly in position than would be the case if
the horizontal root could easily bend at this point. The knees
thus are supposed by some to strengthen the anchor formed by
the root in the loose soil. Their development may be the result
of mechanical irritation at these points on the horizontal root,

SOIL FORMATION: MOORS. 397

brought about by the strain on the roots from the swaying of the
tree. Others regard them as organs for aerating the portions of
the root system which are usually submerged in water or wet
soil. The knees catch and hold floating plant remains during
floods, and by the decay of this debris the fertility of the soil is
increased. In deeper water where the lower part of the tree is
constantly submerged, peculiar buttresses are sometimes formed
on the trunk, as shown in figure 491.

398

ECOLOG Y.

SOIL FORMATION: MOORS.

CHAPTER LIV.

ZONAL DISTRIBUTION OF PLANTS.

712. On the margins of lakes or ponds, where the slope is
gradual from the land into the water, one often has an oppor-
tunity to study the relation
of various plants to different
conditions of soil and water.
In rowing near the south shore
of Lake Cayuga, I have often
been impressed with the defi-
nite areas occupied by certain
plants. Figure 492 is from a
photograph, taken from the
boat, of the shore distribution
of these plants. The most
striking feature here is the
grouping of certain kinds of
plants in definite lines or
zones. Here the limitations
of the zones are quite distinct,
so that the transition from
one zone to another is quite
abrupt, though there is some
mixture of the kinds at the
zone of transition, or tension
line.

493 713. This arrangement of

sagittaria variabiiis. plants under such environ-

mental influences is termed " zonal distribution of plants. ' ' The

400

ZONAL DISTRIBUTION' OF PLANTS.

401

slope where this photograph was taken is so symmetrical that
plants suited by their long habit of growing at certain depths of
water, or in soil of a certain moisture content, are readily drawn

Fig- 494-
Sagittaria variabilis.

into zones parallel with the shore line. Several zones can be
readily made out in this region; two of them at least do not show
in the picture since they are submerged.

714. If we treat of the two submerged zones, the first one is
in the rear of the point from where the photograph was taken,
and consists of extensive areas of chara in four to five meters of

4O2

ECOLOGY.

water. The second zone then is in the water shown in the fore-
ground of the picture. The plants here are also submerged, or
only a small portion reaches the surface of the water, and so the

Fig- 495-
Sagittaria heterophylla. Often forms a zone just outside of the Sagittaria variabilis.

zone does not show. In this zone occurs the curious Vallesneria
spiralis, with its corkscrew flower stem, and various potamoge-
tons.

715. In the third zone, or the first one which shows in the
picture, are great masses of the arrow-leaf (sagittaria) so variable

ZONAL DISTRIBUTION OF PLANTS.

403

404

ECOLOGY.

ZONAL DISTRIBUTION OF PLANTS.

405

in the form of its leaves. Next is the fourth zone, made up here
chiefly of bullrushes (scirpus), and occasionally are clumps of the
cattail flag (typha). Behind this is the fifth zone, only to be
distinguished at this distance by the bright flower heads of the
boneset (Eupatorium perfoliatum) and joepye-weed (Eupato-

Fig. 498-
Bank of joepye-weed, Eupatorium purpureum. (Photograph by author.)

rium purpureum), and the blue vervain (Verbena hastata), which
occurs on the land. Willows make a compact and distinct sixth
zone, while at the right, shown in figure 496 taken alongside
this view, the oaks on the hillside beyond form a seventh zone,
and still farther back is a zone of white pines, making the
eighth.

716. On the banks of a stream emptying into this end of the
lake, after pursuing its sinuous course through wooded flats, are
living pictures, which present a wealth of beauty in color and
harmony of association and environment, charming to behold

406

ECOLOGY.

and delightful to study. At the entrance (figure 497) a broad
sweep of typha margins a projecting arm of the land which affords
a quiet nook for the repose of mats of green algae, of such sorts

Fig. 499.
Pontederia, showing leaves and flower spike.

as spirogyra, cedogonium, cladophora, etc., floating on the placid
water in the foreground. Slender stems of zizania rise like
shooting stars among the flags, with scirpus crowding near,
while masses of the flowers of the thoroughwort are sheltered by

ZONAL DISTRIBUTION OF PLANTS.

407

overhanging willows. On the left, pond-weeds (Potamogeton
natans) and the yellow water lily, or spatter-dock (nuphar),

Fig. 500.
Yellow water lily on jutting arm in stream. (Photograph by the author.)

float their leaves and flowers on the quiet water, while the small
yellow flowers of the mud plantain ( Heteranthera graminifolia)
glitter in the sunlight. The arrow-leaf (Sagittaria heterophylla,

408 ECOLOGY.

and variabilis) stand to their necks in the water. The shore
near by is lined with sedges. Beyond these on the banks
are masses of the white and purple eupatorium, with a goodly
sprinkling of the swamp milkweed, its blossoms ablaze with
color, while a long bank of willows forms a background of satis-
fying green.

717. Rowing up the stream, one passes in review minor for-
mations, which exhibit less regularity of distribution and fewer
individuals of one species. Pontederia still lingers along near
the shore, nearly touching the feet of the purple eupatorium on
the bank. The yellow water lily, in groups here and there,
points out the shallows, or traces the jutting arms of the shore,
which in the distance seem to intercept the course, and the
wavelets on the water toss into fantastic figures the mirrored
shrubs and trees. In the quiet nooks the sunlight blazes down
upon umbels of the blue cornel and the pendent fruit clusters
of the trailing nightshade. Banks of goldenrod are massed on
one hand, and here and there stand gorgeous clusters of the
arrow-leaved polygonum and of the yellow touch-me-not, while
every now and then the sickly, blighting form of the cuscuta
holds its victims in a crushing embrace.

718. Successions of waves running along the sunny shore
throw lights and shadows, which chase each other up the trunks
of overhanging trees in the form of rings of sunlight and shade,
and then throw a quivering, shimmering light over the foliage.
Fallen trees stretch their weather-beaten and bleached trunks
over the stream, and their mirrored ghosts dance in the waves at
your approach, while the towering elms beyond, smothered in
the foliage and embrace of the poison ivy, add to the weird
beauty of the scene.

ZONAL DISTRIBUTION OF PLANTS. 409

Fig. 501.
Elms in background covered by poison ivy. (Photograph by the authors

CHAPTER LV.

PLANT COMMUNITIES: SEASONAL CHANGES.

719. One of the interesting subjects for observation in the
study of the habits and haunts of plants is the relation of plants
to each other in communities. In the topography of the moors,
and of the land near and on the margins of bodies of water, we
have seen how the adaptation of plants to certain moisture con-
ditions of the soil, and to varying depths of the water, causes
those of a like habit in this respect to be arranged in definite
zones. Often there is a predominating species in a given zone,
while again there may be several occupying the same zone, more
or less equally sharing the occupation. Many times one species
is the dominant form, while several others exist by sufferance.

720. Plants of widely different groups may exist in the
same community. — So it is that plants of widely different rela-
tionships have become adapted to grow under almost identical
environmental conditions. The reed or grass growing in the
water is often accompanied by floating mats of filamentous algae
like spirogyra, zygnema ; or other species, as oadogonium, coleo-
chaete, attach themselves to these higher lords of creation ; while
desmids find a lodging place on their surface or entangled in the
meshes of the other algae. Chara also is often an accompaniment
in such plant communities, and water-loving mosses, liverworts,
and fern-like plants as marsilia. Thus the widest range of plant
life, from the simple diatom or monad to the complex flowering
plant, may, by normal habit or adapted form, live side by side,
each able to hold its place in the community.

721. In field or forest, along glade or glen, on mountain
slope or in desert regions, similar relationships of plants in

410

PLANT COMMUNITIES: SEASONAL CHANGES. 41 1

communities are manifest. The seasons, too, seem to vegetate,
blossom, and fruit, for in the same locality there is a succession
of different forms, the later ones coming on as the earlier ones
disappear.

722. Seasonal succession in plant communities. — The
wooded slopes in springtime teem with trillium, dentaria, pod-
ophyllum, and other vernal blossoms, while on the steeper hill-
sides the early saxifrage is to be found. In the rocky portions

Fig. 502.
Azalea (Rhododendron nudicaulis).

of the glen, which is also a favorite lodgment for this pretty,
white saxifrage, the wild columbine loves to linger and dangle
its spurred flowers. The lichen-colored ledge is wreathed with
moss and fern. On the partly sunlit slopes the clusters of azalea
are radiant with blossoms, while here and there the shad-bush,
or service-berry (amelanchier), with its mass of white flower-

412

ECO LOG Y.

Fig. 503-
Walkine fern, climbine down a

PLAN rr COMMUNITIES: SEASONAL CHANGES.

sprays, overhangs some cliff, and the cockspur thorn (crataegus)
vies with it in the profusion of floral display. Near by sheets of
water pour themselves unceasingly on the rocks below, scattering
spray on the thirsty marchantia. Out from the steep slopes
above rise the graceful sprays of yew (taxus), shaded by the
towering hemlock spruces. The "walking-fern" here, holding
fast above, climbs downward by long graceful strides.

723. But the scene shifts, and while these flowers cast their
beauty for the season, others put on their glory. The flowering

Fig. 504.
Spray of kalmia flowers.

dogwood spreads its deceptive bracts as a halo around the clus-
ters of insignificant flowers. The laurel (kalmia) with its clus-
ters of fluted pinkish blossoms is a joy only too brief. Smaller
and less pretentious ones abound, like the whortleberries, am-
phicarpaea, bush-clover (lespedeza), sarsaparilla, and so on.

724. In the autumn the glen is clothed with another robe of
beauty. With the fall of the "sere and yellow leaf," golden-

4H ECOLOGY.

rod and aster still linger long in beauty and profusion. When
the leaves have fallen the witch-hazel (hamamelis) begins to

Fig. 5°S-
Spray of witch-hazel (hamamelis) with flowers ; section of flower below.

flower, and the snows begin to come before it has finished
spreading its curled yellow petals.

725. The landscape a changing panorama. — In our temper-
ate regions the landscape is a changing panorama ; forest and
field, clothed with a changing verdure, don and doff their foliage
with a precision that suggests a self-regulating mechanism.

In the glad new spring the mild warmth of the sun stirs the
dormant life to renewed activity. With the warming up of the
soil, root, absorption again begins, and myriads of tiny root hairs
pump up watery solutions of nutriment and various salts. These
are carried to the now swelling buds where formative processes
and growth elongate the shoot and expand the leaf. Buds long
wrapped in winter sleep toss back the protecting scales. In a
multitude of ways the different shrubs and trees now discard the
winter armature which has served so good a purpose, and tiny
bud leaves show a multitude of variations from simple bud scale
to perfect leaf, a remarkable diversification in which the plant
from lateral members of the stem forms organs to serve such a
variety of purpose under such diametrically opposed environ-
mental conditions.

PLANT COMMUNITIES: SEASONAL CHANGES. 41S

726. Refoliation of bare forests in spring. — There is a cer-
tain charm watching the refoliation of the bare forests, when the
cool gray and brown tints are slowly succeeded by the light yel-
low-green of the young leaves, which presents to us a warming

Fig. 506.
Opening buds of hickory.

glow of color. Then the snow-clad fields change to gray, and
soon are enveloped in a living sea of color. The quiet hum of
myriads of opening buds and flowers in harmony with the
general awakening of nature, and the trickling streamlets which
unite into the gurgling brooks, makes sweet music to our atten-
tive minds.

416

ECOLOGY.

727. The evergreens display a striking contrast of color. The
leafy, fan-shaped branches of the hemlock-spruce (tsuga) are

Fig. 507.
Austrian pine, showing young growth of branches in early spring.

fringed with the light green of the new growth. The pines lift
up numbers of cylindrical shoots, with the leaf fascicles for a
time sheathed in the whitened scales, while the shoots are tipped
with the brown or flame-colored female flowers, reminding one

PLANT COMMUNITIES: SEASONAL CHANGES. 417

of a Christmas tree lighted with numerous candles. The numer-
ous clusters of staminate flowers suggest the bundles of toys and
gifts, and one inquires if this beautiful aspect of some pines
when putting on their new growth did not suggest the idea of
the Christmas tree at yule time.

728. The summer tints are more subdued. — As summer-
time draws on the new needles of the pine are unsheathed, the
light green tints of the forest are succeeded by darker and sub-
dued colors, which better protect the living substance from the
intense light and heat of midsummer. The physiological pro-
cesses for which the leaf is fitted go on, and formative materials
are evolved in the countless chlorophyll bodies and transported
to growing regions, or stored for future use. In transpiration
the leaf is the terminus of the great water current started by the
roots. Here the nutrient materials, for which the water serves
as a vehicle, are held back, while the surplus water evaporates
into the air in volumes which surprise us when we know that it
is unseen.

729. Autumn colors. — As summer is succeeded by autumn, a
series of automatic processes goes on in the plant which fits it
for its long winter rest again. Long before the frosts appear,
here and there the older leaves of certain shrubs lose more or
less of the green color and take on livelier tints. With the dis-
integration of the chlorophyll bodies, other colors, which in
some cases were masked by the green, are uncovered. In other
cases decomposition products result in the formation of new
colors. These coloring substances to some extent absorb the
sun's rays, so that much of the nitrogenous substances in the leaf
may not be destroyed, but may pass slowly back into the stem
and be stored for future use.

730. Fall of the leaf. — The gorgeous display of color, then,
which the leaves of many trees and shrubs put on is one of the
many useful adaptations of plants. While this is going on in
deciduous trees, the petiole of the leaf near its point of attachment
to the stem is preparing to cut loose from the latter by forming
what is called a separative layer of tissue. At this point the cells

ECOLOGY.

in a ring around the central vascular bundle grow rapidly so as to
unduly strain the central tissue and epidermis, making it brit-
tle. In this condition a light puff of wind whirls them away in
eddies to the ground. The frosts of autumn assist in the separa-
tion of the leaf from the stem, but play no part in the coloration
of the leaf.

As the cold weather of autumn and winter draws slowly on,
these trees and shrubs cast off their leaves, and thus get rid of
the extensive transpiration surface, or in same cases the dead
leaves may cling for quite a long period to the trees. However
in the death and fall of the leaves of these deciduous trees and
shrubs, or the dying back of the aerial shoots of perennial
herbaceous plants, there is a most useful adaptation of the plant
to lay aside, for the cold period, its extensive transpiration sur-
face. For while the soil is too cool for root absorption, should
transpiration go on rapidly, as would happen if the leaf surface
remained in a condition for evaporation, the plants would lose
all their water and dry up.

CHAPTER LVI.

ADAPTATION OF PLANTS TO CLIMATE.

731. Some characteristics of desert vegetation. — One of the

important factors in plant form and distribution is that of climate,
which is modified by varying conditions, as temperature, hu-
midity of the air, dryness, etc. In desert regions where the air
and soil are very dry, and plants are subject to long periods of
drought, there is a very characteristic vegetation, and a variety of
forms have become adapted to resist the drying action of the
climate.

732. Some of the plants, especially the larger ones, have very
succulent stems or trunks, or they are more or less expanded but
thickened, while the leaves are reduced to mere spines or hairs,
as in the cacti. If plants in desert regions had thin and broadly
expanded leaves, transpiration would be so rapid, and so great,
as to kill them. In these succulent stems there is a proportion-
ately small surface area exposed, so that transpiration is reduced.
The chlorophyll resides here in the stems, and they function as
foliage leaves in many other plants do.

733. Other plants of the desert, which do not have succulent
stems, are provided with closely appressed and small, thick,
scale-like leaves. The leaves in many of these plants have an
epidermis of several layers of cells, so that transpiration does not
take place so rapidly. In addition to this the stomata are sunk
in pits, or cavities, so that the guard cells are not so exposed to
the drying action of currents of air at the surface.

734. In still other cases the leaves and stems are covered with
a dense felt of hairs which serves as a cushion to protect them

419

420

ECO LOG V.

FIG. 508.
Birch trees trom Greenland, one third natural size.

ADAPTATION TO CLIMATE. 421

from the direct rays of the sun, and also from the fierce blasts of
dry air which frequently sweep over these regions. The hairs
are so close, and so interwoven, that the air caught in the inter-
stices is not easily displaced, and the leaves are not then subject
to the drying effects of the passing winds.

735. Some plants of temperate regions possess characters
of desert vegetation. — Even in temperate regions in localities
where the climate is more equable, certain plants, strangely, are
similarly modified, or provided with protecting armor. The
common purslane (portulacca) is an example of a succulent
plant, and we know how well it is able to resist periods of
drought, even when cut free from the soil. With the oncoming
of rains it revives, and starts new growth, while in wet weather
cutting it free from its roots scarcely interferes with its growth.

736. Similarly the common mullein (Verbascum thapsus), the
leaves and stems of which are so densely covered with stellate
hairs, is able to resist dry periods. One can see how efficient this
panoply of trichomes is by immersing the leaves in water. It is
very difficult to remove the air from the interstices of the inter-
woven trichomes so as to wet the epidermis.

737. Alpine plants with desert characteristics. — Alpine
plants (those on high mountains), as well as arctic plants, are
similarly modified, having usually either succulent stems and
leaves, or small, thick and appressed leaves, or leaves covered
with numerous hairs. Cassiope, occurring on mountain summits
of the northeastern United States, and far northward, has numer-
ous needle-shaped, closely imbricated leaves. The plants need
the protection afforded them by these peculiarities in these alpine
and arctic regions because of the dry air and winds, as well as
because of the bright sunlight in these regions. Because of the
bright sunlight in alpine and arctic regions many of the plants
are noted for the brilliant colors of the flowers.

738. Low stature of alpine plants a protection against wind
and cold. — Another protection to plants from winds and from
the cold in such regions is their low stature. Many of the her-
baceous plants have very short stems, and the leaves lie close to

422

ECOLOGY.

FIG. 509.
Willows from Greenland, or:^ third natural size.

ADAPTATION TO CLIMATE. 423

the soil, the plants and flowers sometimes half covered with the
snow. The heat absorbed by the soil is thus imparted to the
plant. Trees in such regions (if the elevation or latitude is not
beyond the tree line) have very short and crooked stems, and
sometimes are of great age when only a foot or more high, and
the trunk is quite small. In figure 508 are shown some birch trees
from Greenland, one third natural size, the entire tree being here
shown. Similarly figure 509 represents some of the arctic wil-
lows, one third natural size.

739. Some plants of swamps and moors present characters of
arctic or desert vegetation. — Many of the plants of our swamps
and moors have the characters of arctic or of desert vegetation,
i.e. small, thick leaves, or leaves with a stout epidermis. The
labrador tea (Ledum latifolium), an inhabitant of cold moors or
mountain woods, has thick, stout leaves with a hard epidermis
on the upper side, and the lower side of the leaves is densely
covered with brown, woolly hairs. Transpiration is thus lessened.
This is necessitated because of the cold soil and water of the
moor surrounding the roots, which under these conditions absorb
water slowly. Were the leaves broad with a thin and unpro-
tected epidermis, transpiration would be in excess of absorption,
and the leaves would wither. Cassandra, or leather-leaf, and
chiogenes, or creeping snowberry, are other examples of these
shrubs growing in cold moors.

740. Hairs on young leaves protect against cold and wet.—
Hairs on young leaves in winter buds afford protection from cold
and from the wet. The young leaves of the winter buds of many of
our ferns are covered with a dense felt of woolly hairs. In species
of osmunda this is very striking. The leaves are quite well
formed, though small, during the autumn, and the sporangia are
nearly mature. The hairs are so numerous, and so closely mat-
ted together, that they can be torn off in the form of a thick
woolly cap.

APPENDIX.

COLLECTION AND PRESERVATION OF MATERIAL.

Spirogyra may be collected in pools where the water is pres-
ent for a large part of the year, or on the margins of large
bodies of water. To keep fresh, a small quantity should be
placed in a large open vessel with water in a cool place fairly
well lighted. In such places it may be kept several months in
good condition.

Mucor may be obtained by placing old bread, etc., or horse
dung, in a moist covered vessel. In the course of a week there
should be an abundance of the mycelium and gonidia. From
this material cultures may be made, if desired, in nutrient gela-
tin or nutrient agar.

Saprolegnia, or water mould, can be used for a study of pro-
toplasm. Collect several dead house flies from window sills of
neglected rooms. Immerse them in alcohol, then rinse in
water to remove the alcohol. Then throw them in vessels of
water containing freshly collected algae from several different
places. In the course of a week there should be a tuft of whit-
ish threads of the water mould surrounding the fly.

Nitella is obtained in rather deep pools or ponds, or in slow-
running water, at a depth of one to three feet usually.

Stamen hairs or tradescantia can usually be obtained in
greenhouses from flower buds just ready to open or just after
opening.

(Edogonium is often found in floating mats in ponds, or on
the margins of slow-running streams, or of lakes. Frequently
it is attached to other aquatic plants, Fruiting plants can be

425

426 APPENDIX.

detected by certain of the cells being rounded and broader than
others, and some of them at least usually containing the spores,
a single spore nearly or quite filling the large cell, or oogonium.
When it cannot be studied fresh it may be preserved in 2%
formalin or in 70$ alcohol, first placing it successively in 25$
and 50$ alcohol for a few hours.

Some species of vaucheria occur in places frequented by
cedogonium or spirogyra, while others occur in running water,
or still others on damp ground. Frequently fine specimens of
vaucheria in fruit may be found during the winter growing on
the soil of pots in greenhouses. The jack-in-the-pulpit, also
known as Indian turnip, growing in damp ground I have found
when potted and grown in the conservatory yields an abundance
of the vaucheria, probably the spores of the alga having been
transferred with the soil on the plants. When material cannot
be obtained fresh for study, it may be preserved in advance in
formalin or alcohol as described for oedogonium.

Coleochaete scut at a is not so common as the redogonium,
spirogyra, or vaucheria. But it may be sometimes found with
the small circular green disks adhering to rushes, grasses, or
other aquatic plants in large ponds or on the margins of lakes.
When found it is well to make permanent mounts of material
killed in formalin, either in glycerine or glycerine jelly.

Wheat rust. — The cluster-cup stage may be collected in May
or June on the leaves of the barberry. Some of the affected
leaves may be dried between drying-papers. Other specimens
should be preserved in 2% formalin or in 70^ alcohol. If the
cluster cup cannot be found on the barberry, other species may
be preserved for study.

The uredospore and teleutospore stages can usually be found
abundantly on wheat and oats, especially on late-sown oats which
ripen in autumn. The affected leaves and stems may be pre-
served dry.

The powdery mildews are common during summer and au-
tumn on a variety of leaves of shrubs, herbs, and trees. They
can be recognized by the mildewed spots, or by the numerous

COLLECTION AND PRESERVATION OF MATERIAL. 427

minute black specks on the surface of the leaf. The leaves
should be preserved dry after drying under pressure.

Liverworts.

Marchantia. — The green thallus (gametophyte) of marchan-
tia may be found at almost any season of the year along shady
banks washed by streams, or on the wet low shaded soil. Plants
with the cups of gemmae are found throughout a large part of
the year. They are sometimes found in greenhouses, especially
where peat soil from marshy places is used in potting. In May
and June male and female plants bear the gametophores and
sexual organs. These can be preserved in 2$% formalin or in
70$ alcohol. If one wishes to preserve the material chiefly for
the antheridia and archegonia a small part of the thallus may be
preserved with the gametophores, or the gametophores alone.

In July the sporogonia mature. When these have pushed out
between the curtains underneath the ribs of the gametophore,
they can be preserved for future study by placing a portion of
the thallus bearing the gametophore in a tall vial with 2$ for-
malin. Plants with the sporogonia mature, but not yet pushed
from between the curtains on the under side, can be collected in
a tin box which contains damp paper to keep the plants moist.
Here the sporogonia will emerge, and by examining them day
by day, when some of the sporogonia have emerged, these plants
can be quickly transferred to the vials of formalin before the spo-
rogonia have opened and lost their spores. In this condition the
plant can be preserved for several years for study of the gross
character of the sporogonia and the attachment to the gameto-
phyte. From some of the other plants permanent mounts in
glycerine jelly may be made of the spores and elaters.

Riccia. — Riccia occurs on muddy, usually shaded ground.
Some species float on the surface of the water. It may be pre-
served in 2^ formalin or 70$ alcohol.

Cephalozia, ptilidium, bazzania, jungermannia, frullania, and
Other foliose liverworts may be found on decaying logs, on the

428 APPENDIX.

trunks of trees, in damp situations. They may be preserved in
formalin or alcohol. Some of the material may also be dried
under pressure.

Mosses are easily found and preserved. Male and female
plants for the study of the sexual organs should be preserved in
formalin or alcohol. In all these studies whenever possible living
material freshly collected should be used.

Ferns.

For the study of the general aspect of the fern plant, polypo-
dium, aspidium, onoclea, or other ferns may be preserved dry
after pressure in drying sheets. A portion of the stem with the
leaves attached should be collected. These may be mounted on
stiff cardboard for use. The sporangia and spores can also be
studied from dried material, but for this purpose the ferns should
be collected before the spores have been scattered, but soon after
the sporangia are mature. But when greenhouses are near it is
usually easy to obtain a few leaves of some fern when the sporangia
are just mature but not yet open. To prevent them from opening
and scattering the spores in the room before the class is ready to
use them, immerse the leaves in water until ready to make the
mounts ; or preserve them in a damp chamber where the air is
saturated with moisture.

For study of the prothallia of ferns, spores should be caught
in paper bags by placing therein portions of leaves bearing ma-
ture sporangia which have not yet opened. They should be
kept in a rather dry but cool place for one or two months.
Then the spores may be sown on well -drained peat soil in pots,
and on bits of crockery strewn over the surface. Keep the pots
in a glass-covered case where the air is moist and the light is
not strong. If possible a gardener in a conservatory should be
consulted, and usually they are very obliging in giving sugges-
tions or even aid in growing the prothallia.

Lycopodium, equisetum, selaginella, isoetes, and other pteri-
dophytes desired may be preserved dry and in 70$ alcohol.

Pines. — The ripe cones should be collected before the seeds

COLLECTION AND PRESERVATION OF MATERIAL. 429

scatter, and be preserved dry. Other stages of the development
of the female cones should be preserved either in 70$ alcohol or
in 2\% formalin. The male cones should be collected a short
time before the scattering of the pollen, and be preserved either
in alcohol or formalin.

Angiosperms. — In the study of the angiosperms, if it is de-
sired to use trillium in the living state for the morphology of the
flower before the usual time for the appearance of the flower in
the spring, the root-stocks may be collected in the autumn, and
be kept bedded in soil in a box where the plants will be sub-
jected to conditions of cold, etc. , similar to those under which
the plants exist. The box can then be brought into a warm
room during February or March, a few weeks before the plants
are wanted, when they will appear and blossom. If this is
not possible, the entire plant may be pressed and dried for the
study of the general appearance and for the leaves, while the
flower may be preserved in 2-J# formalin, of course preserving a
considerable quantity. Other material for the study of the plant
families of angiosperms may be preserved dry, and the flowers
in formalin, if they cannot be collected during the season while
the study is going on.

Demonstrations. — Upon some of the more difficult subjects in
any part of the course, especially those requiring sections of the
material, demonstrations may be made by the teacher. The ex-
tent to which this must be carried will depend on the student's
ability to make free-hand sections of the simpler subjects, upon
the time which the student has in which to prepare the material
for study, and the desirability in each case of giving demostra-
tions on the minuter anatomy, the structure of the sexual organs
and other parts, in groups where the material should be killed
and prepared according to some methods of precision, now used
in modern botanical laboratories. The more difficult demonstra-
tions of this kind should be made by the instructor, and such
preparations once made properly can be preserved for future
demonstrations. Some of them may be obtained from persons
who prepare good slides, but in such cases fancy preparations of

43° APPENDIX.

curious structures should not be used, but slides illustrating the
essential morphological and developmental features. Directions
for the preparation of material in this way cannot be given, in
this elementary book, for want of space.

Method of taking notes, etc. — In connection with the prac-
tical work the pupil should make careful drawings from the
specimens ; in most cases good outline drawings, to show form,
structure etc., are preferable, but sometimes shading can be
used to good advantage. It is suggested that the upper 2/3 of
a sheet be used for the drawings, which should be neatly made
and lettered, and the lower part of the page be used for the
brief descriptions, or names of the parts. The fuller notes and
descriptions of the plant, or process, or record of the experi-
ment should be made on another sheet, using one, two, three,
or more sheets where necessary. Notes and drawings should be
made only on one side of the sheet. The note-sheets and the
drawing-sheets for a single study, as a single experiment, should
be given the same number, so that they can be bound together
in the cover in consecutive order. Each experiment may be
thus numbered, and all the experiments on one subject then
can be bound in one cover for inspection by the instructor.
For example, under protoplasm, spirogyra may be No. i, mucor
No. 2, and so on. In connection with the practical work the
book can be used by the student as a reference book ; and dur-
ing study hours the book can be read with the object of arrang-
ing and fixing the subject in the mind, in a logical order.

The instructor should see that each student follows some well-
planned order in the recording of the experiments, taking notes,
and making illustrations. Even though a book be at hand for
the student to refer to, giving more or less general or specific
directions for carrying on the work, it is a good plan for every
teacher to give at the beginning of the period of laboratory
work a short talk on the subject for investigation, giving general
directions. Even then it will be necessary to give each indi-
vidual help in the use of instruments, and in making prepara-
tions for study, until the work has proceeded for some time,

APPARATUS AND GLASSWARE. 431

when more general directions usually answer. The author does
not believe it a good plan for the student to have written,
minute, directions for preparing the plants and experiments.
General directions and specific help where there is difficulty,
until the student learns to become somewhat independent, seems
to be a better plan.

APPARATUS AND GLASSWARE.

The necessary apparatus should be carefully planned and be
provided for in advance. The microscopes are the most expen-
sive pieces of apparatus, and yet in recent years very good mi-
croscopes may be obtained at reasonable rates, and they are
necessary in any well-regulated laboratory, even in elementary
work.

Microscopes. The number of compound microscopes will
depend on the number of students in the class, and also on the
number of sections into which the class can be conveniently
divided. In a class of 60 beginning students I have made two
sections, about 30 in each section ; and 2 students work with
one microscope. In this way 15 microscopes answer for the
class of 60 students. It is possible, though not so desirable, to
work a larger number of students at one microscope. Some can
be studying the gross characters of the plant, setting up appa-
ratus, making notes and illustrations, etc., while another is en-
gaged at the microscope with his observations.

The writer does not wish to express a preference for any pat-
tern of microscope. It is desirable, however, to add a little to
the price of a microscope and obtain a convenient working
outfit. For example, a fairly good stand, two objectives (2/3
and 1/6), one or two oculars, a fine adjustment, and a coarse
adjustment by rack and pinion, and finally a revolver, or nose-
piece, for the two objectives, so that both can be kept on the
microscope in readiness for use without the trouble of removing
one and putting on another. Such a microscope, which I have

432 APPENDIX.

found to be excellent, is Bausch & Lomb's AAB (which they
recommend for high schools), costing about $25.00 to $28.00.
I have compared it with some foreign patterns, and the cost of
these is no less, duty free, for an equivalent outfit. Of course,
one can obtain a microscope for $18.00 to $20.00 without some
of these accessories, but I believe it is better to have fewer
microscopes with these accessories than more without them.
Of the foreign patterns the Leitz (furnished by Wm. Krafft,
411 W. 59th St., N. Y. ) and the Reichert are good, while Queen
& Co., Philadelphia, Pa., and Bausch & Lomb, Rochester,
N. Y., furnish good American instruments.

Glass slips, 3X1 inch ; and circle glass covers, thin, 3/4 in.
diameter.

Glass tubing of several different sizes, especially some about
$mm inside diameter and ^mm outside measurement, for root-
pressure experiments.

Rubber tubing to fit the glass tubing, and small copper wire
to tighten the joints.

Watch glasses, the Syracuse pattern (Bausch & Lomb), are
convenient.

U tubes, some about 2omm diameter and io-i$cm long.
Corks to fit.

Small glass pipettes ( ' * medicine droppers ' ' ) with rubber
bulbs.

Wide-mouth bottles with corks to fit. Reagent bottles. (Small
ordinary bottles about locm x 4cm with cork stoppers will an-
swer for the ordinary reagents. The corks can be perforated
and a pipette be kept in place in each ready for use. Such
bottles should not be used for strong acids.)

Small vials with corks for keeping the smaller preparations in.

Small glass beakers or tumblers.

A few crockery jars for water cultures.

Fruit jars for storing quantities of plant material.

Glass graduates; i graduated to IOOQCC, i graduated to
IOOOT.

Funnels, small and medium (6 and locm in width). Test

APPARATUS AND GLASSWARE. 433

tubes. A few petrie dishes. Bell jars, a few tall ones and a
few low and broad. Thistle tubes. Chemical thermometer.

Balance for weighing. A small hand-scale furnished by Eimer
& Amend, 205-211 3d Ave., N. Y. , is fairly good ($2.00).

For pot experiments, the "Harvard trip-scale," Fairbanks
Scale Co. (about $6.00).

Apparatus stand, small, several, with clamps for holding test
tubes, U tubes, etc.

Agate trays, very shallow, several centimeters long and wide.
Agate pans, deep, for use as aquaria, etc., with glass to cover.

Paraffin or wax, for sealing joints in setting up transpiration
apparatus.

Mercury, for restoration of turgidity, and for lifting power of
transpiration.

Sheet rubber, or prepared vessels for enclosing pots to prevent
evaporation of water from surface during transpiration experi-
ments.

Litmus paper, blue, kept in a tightly stoppered bottle. Filter
paper for use as absorbent paper. Lens paper (fine Japanese
paper) for use in cleaning lenses ; benzine for first moistening
the surface, and as an aid in cleaning.

For materials for culture solution, see Chapter III.

REAGENTS.

Glycerine, alcohol of commercial (95$) strength, formalin or
formalose of 40$ strength, chloral hydrate crystals, iodine crys-
tals, eosin crystals, fuchsin crystals, potassium iodide, potassium
hydrate, potash alum. It is convenient also to have on hand
some ammonia, sulphuric acid, nitric acid, and muriatic acid in
small quantity.

REAGENTS READY FOR USE AND FOR STORING PLANT MATERIAL

IN.

Alcohol. Besides the 95$ strength, strengths of 30$, 50$, and
70$, for killing material and bringing it up to 70$ for storage.

434 APPENDIX.

Formalin. Usually about a 2\% is used for storing material,
made by taking 97 \ parts water in a graduate and filling in 2|
parts of the 40% formalin.

Salt solution 5$ ; sugar solution 15$ (for osmosis).
Iodine solution. Weak — to ^oocc distilled water add 2

grams iodide of potassium ; to
this add i gram iodine crys-
tals.

Strong — use less water.

Eosin. Alcoholic solution. Distilled water $occ, alco-
hol $occ, eosin crystals £ gram, potash alum 4
grams.
Aqueous solution. Distilled water IOQCC, eosin crystals

i gram.

Chloral hydrate ; aqueous solution, nearly sat. sol.
Schimper's solution. Chloral hydrate 5 parts, water 2 parts,
iodine to make a strong color.

STUDENT LIST OF APPARATUS.

Several glass slips 3X1 inch, and more circle glass covers,
thin and J inch diameter.

One scalpel.

One pair forceps, fine points.

Two dissecting needles (may be made by thrusting with aid of
pincers a sewing needle in the end of a small soft pine stick).

Lead- pencils, one medium and one hard.

Note paper; a good paper, about octavo size, smooth, unruled,
with two perforations on one side for binding. Several manila
covers or folders to contain the paper, perforated also. Enough
covers should be provided so that notes and illustrations on dif-
ferent subjects can be kept separate.

REFERENCE BOOKS.

The following books are suggested as suitable ones to have on
the reference shelves, largely for the use of the teacher, but sev-

REFERENCE BOOKS. 435

eral of them can with profit be consulted by the students also.
There are a number of other useful reference books in Ger-
man and French, and also a number of journals, which might be
possessed by the more fortunate institutions, but which are too
expensive for general use, and they are not listed here.

Kerner and Oliver, Natural History of Plants. Blackie & Son,
London, 1895. Henry Holt & Co., New York, 1895.

Strasburger, Noll, Schenck & Schimper, A Text Book of Bot-
any, translated by Porter. The Macmillan Co., New York,
1898.

Vines, Student's Text Book of Botany. The Macmillan Co.,
New York, 1895.

Atkinson, The Biology of Ferns. The Macmillan Co., New
York, 1894.

MacDougal, Experimental Plant Physiology. Henry Holt &
Co., New York, 1895.

Spalding, Introduction to Botany. D. C. Heath & Co., Bos-
ton, 1895.

Bessey, Essentials of Botany. Henry Holt & Co., New
York.

Goebel, Outlines of Classification and Special Morphology of
Plants. Oxford, Clarenden Press, 1887.

Warming & Potter, Hand Book of Systematic Botany. Mac-
millan &Co., New York, 1895.

DeBary, Comparative Morphology and Biology of the Fungi,
Mycetozoa, and Bacteria. Oxford, Clarenden Press, 1887.

Underwood, Our Native Ferns and their Allies. Henry Holt
& Co., New York.

Bailey, Lessons in Plants. Macmillan & Co., New York,
1898.

Gray, Lessons and Manual of Botany. American Book Co.,
New York.

Miiller, The Fertilization of Flowers. Macmillan & Co. , New
York.

Darwin, Insectivorous Plants. D. Appleton & Co., New
York.

436 APPENDIX.

Darwin, The Power of Movement in Plants. D. Appleton &
Co., New York.

Darwin, Cross and Self Fertilization in the Vegetable King-
dom. D. Appleton & Co., New York.

Warming, Oekologische Pflanzengeographie. Gebriider Born-
trager, Berlin.

Papers by Macmillan in the Bulletin of the Torrey Botanical
Club and Minn. Bot. Studies, by Shaler in the 6th, loth, and
1 2th Annual Reports of the United States Geological Survey,
and by Ganong in Trans. Roy. Soc. Canada, sec. ser. vol. 3,
1897—98, should be consulted by those interested in ecology.

Where materials cannot be readily collected in the region for
class use, they can often be purchased of supply companies.

The Cambridge Botanical Supply Co., Cambridge, Mass.,
supplies plant material of several groups for study, as well as
apparatus and paper.

The Ithaca Botanical Supply Co., Ithaca, N. Y., will supply
plants for study in various groups, and upon order will prepare
permanent slides for demonstration of the more difficult topics,
such as the structure of the sexual organs of liverworts, mosses,
ferns, etc.

INDEX.

Absorption, 13

Aceraceae (A-cer-a ce-ae), 273,
275, 298

Acer saccharinum (A'cer sac-
cha-ri'num), 275

Adder tongue, formation of
flower, 349

Adiantum (A-di-an'tum), 169, 173

Adiantum concinnum, spermato-
zoids of, 181; embryo, 184, 185

Adiantum cuneatum, fertiliza-
tion, 182; embryo, 186

^Ecidiospore (^E-cid'i-o-spore),

131

^Ecidium (^E-cid'i-um), 132
^Esculinae (^Es-cu-lin'ae), 273, 297
Agaricus campestris (A-gar'i-

cus cam-pes'tris), 136, 326-331
Agaricus melleus, 338
Aggregatae, 290, 299
Alga, Algae, 2
Alismaceae (A-lis-ma'ce-ae), 254,

255

Alisma plantago, 254
Amanita phalloides (Am-a-ni'ta

phal-loi'des), 334, 335
Almond (family), 276
Amygdalaceae (A-myg-da-la'-

ce-ae), 276, 295, 298
Anemophilous, 353
Angiosperms, comparative table

of, 238
Angiosperms, morphology of,

221-236

Antheridiophores, 145
Antheridium, of vaucheria, 107;

cedogonium, 101, 102; coleo-

chaete, 112; saprolegnia, 123;

erysiphe, 138; liverworts, 141,

145, 146; mosses, 160, 161;

ferns, 180, 181; selaginella,

194; isoetes, 198
Antipodal cells, 231, 233
Apogamy, 245

Apogeotropic (Ap-o-ge-ot'ro-
pic), 83

Apogeotropism (Ap-o-ge-ot'ro-
pism), 83

Apospory, 245

Apple, 276

Araceae (A-ra'ce-ae), 257, 294, 296

Archegonia (Ar-che-go'ni-a) of
liverworts, 141, 142, 155, 156;
mosses, 160, 161; ferns, 176,
181, 182; selaginella, 195; iso-
etes,198; gymnosperms, 210,211

Archegoniophore, 147

Archesporium (Ar-che-spor'i-
um), 153, 239

Arisaema triphyllum (Ar-i-sae'ma
tri-phyrium), 257; germination
of, and embryo, 311, 313; pol-
lenation of, 360, 361

Asclepias cornuti (As-clep'i-as
cor-nu'ti), dissemination of
seed, 372

Ascomycetes (As-co-my-ce'tes),
138, 139

Ascospore, 137-139

Ascus (pi. Asci), 137-139

Ash (American), 304

Aspidium acrostichoides, 165,
172, 177

Aspidium spinulosum, 168

Asplenium bulbiferum, 174, 175,

239

Aster novae-angliae, 290, 291
Atoll, made by plants, 386
Azalea, 411

Bacteria, nutrition of, 321
Bald cypress, 395, 396
Basidiomycetes (Ba-sid-i-o-my-

ce'tes), 136. 139
Bast, 44; fibres, 48; parenchyma,

48
Batrachospermum (Ba-tra-cho-

sper'mum), 116

437

438

INDEX.

Bean, germination of, 307, 308

Beet, osmose in, 15, 16, 17, 18

Bell flower, 289

Bicornes, 283, 284, 298

Bidens, seed of, 368

Bindweed, 284

Black rust, 129

Black spruce moor, 390

Blasia, 155

Bloodroot, 271

Blue-green algae, 118

Bluet, pollenation of, 354, 355

Borage, 285

Boraginaceae (Bor-ag-i-na'ce-ae),

285, 299

Buckwheat, 267
Bur marigold, seeds of, 368
Brown algae, 115, 118
Bryony, tendril of, 88
Butomus, 255

Callithamnium, 119

Caltha palustris, 268, 269

Cambium, 44, 48

Campanula, 289; pollenation of,

362

Campanulaceae, 289, 299
Campanulinae, 289, 299
Canna, pollenation of, 363-367
Caprifoliaceae (Cap-ri-fo-li-a'

ce-ae), 288, 296, 299
Carbon conversion, 59, 61, 67, 68;

rays of light concerned in, 67
Carbon dioxide, absorption of,

51; loss of, 54

Carbon, food of plants, 59-64
Carex laxiflora, 261
Carex lupuiina, 260
Carnation rust, 323, 324
Castor oil bean, germination of,

308, 309
Cattails, 257
Cell, 3
Cell sap, 3

Cephalozia (Ceph-a-lo'zi-a), 155
Chaetophora (Chae-toph'o-ra), 103
Champia, 119
Chlamydospores (Chlam-yd'o-

spores), of mucor, 123
Chlorophyceae (Chlo-ro-phy'ce-

x), 118
Chlorophyll, 2. 65-69; band, 2;

bodies, 66; movement of chlo-
rophyll bodies, 68, 69

Chloroplastid, 67

Chloroplasts, 66, 68 ; starch

formed in, 68
Choke cherry, 276, 277
Christmas fern, 165-167
Chromatin, 240
Chromatin skein, 241
Chromoplasts, 68
Chromosomes, 241—243
Claytonia virginiana, 267
Cleistogamous, 353, 354
Clematis virginiana, 269, 270 ;

dissemination of seed, 372, 373
Closterium, 98
Cosmarium, 98
Club mosses, 191-195
Cluster cup, 131, 132, 135
Coleochaete (Co-le-o-chae te), 110-

H3

Coleochaete scutata, no, 112
Coleochaete sbluta, 112
Columella, of rhizopus, 121, 123
Compositae, 290, 296, 299
Conferva, 103
Confer voideae(Con-fer-voi'de-ae),

103, 118

Conjugatae (Con-ju-ga'tae), 98, 118
Conjugation, 94, 96
Contortae, 287
Convolvulaceae (Con-vol-vu-la'

ce-ae), 284, 299
Convolvulus (Con-vol'vu-lus),

284, 285
Cortex, 44
Cruciferae (Cru-cif'er-ae), 272,

295, 297
Cupuliferae (Cu-pu-lif'er-ae), 263,

294, 296
Curvembryae (Curv-em'bry-ae),

268, 297

Cuticularized, 37
Cyanophyceae (Cy-an-o-phy'ce-

ae), 118

Cycas, 214-217 (see also frontis-
piece.)

Cyclosis (Cy-clo'sis), 9
Cyperaceae (Cy-per-a'ce-ae), 259-

261, 296

Cypress knees, 396
Cypripedium, 361, 365
Cytisus (Cy-ti'sus), scattering of

pollen, 363
Cystocarp, 116-119
Cystopteris bulbifera, 174

INDEX.

439

Cystopus candidus, haustoria of,

324
Cytoplasm (Cy'to-plasm), 5

Daucus carota, 281

Dentaria, 221, 225, 227

Desert vegetation, characters of,

419

Desmids, 98

Desmodium (Des-mo'di-um), dis-
semination of seeds, 368
Diadelphous (Di-a-del'phous),

272
Diageotropism (Di-a-ge-ot'ro-

pism), 83
Diaheliotropic (Di-a-he-li-ot'ro-

pic), 84, 86
Diaheliotropism (Di-a-he-li-ot'-

ro-pism), 84, 86
Dicentra canadensis (Di-cen'tra

can-a-den'sis), 271
Dichogamous (Di-chog'a-mous),

360

Dicotyledons, 262-293
Diffusion, 13
Dionaea muscipula (Di-o-nae'a

mus-cip'u-la), 90
Dipsacaceae (Dip-sa-ca'ce-ae),

289, 296, 299

Dipsacales(Dip-sa-ca'les),289,299
Dodder, nutrition of, 321
Dorsiventral, 88
Downy mildews, 128
Drosera (Dros'e-ra), 90
Duck weeds, 314, 315

Ecology (sometimes written (ecol-
ogy), 300-423

Elaters, 150

Embryo, of angiosperms, 232,235

Embryo sac, 229-233

Endosperm, 209-211, 234, 235

Epidermal system, 48

Epigynous, 255

Epinastic (Ep-i-nas tic), 86

Epinasty (Ep-i-nas'ty), 86

Epipactis, pollenationof, 362, 365

Equisetum arvense, 187-189 ;
gametophyte of, 190

Equisetum hyemale, 189

Erica, 284

Erythronium americanum (Er-y-
thro'ni-um), 252, 253 ; forma-
tion of flower, 349

Etiolated plants (E-ti-o-la'ted), 65
Euastrum (Eu-as'trum), 98
Eupatorium purpureum (Eu-pa-

to'ri-um pur-pu're-um), 405
Evaporation, 35, 36
Evening primrose, 279, 280

Ferns, 165-186; dimorphism of,
340-345

Fertilization, in fucus, 115, 117;
cedogonium, 102; peronospora,
127 ; saprolegnia, 125 ; spiro-
gyra, 97 ; sphaerotheca, 138 ;
vaucheria, 108; picea, 212; an-
giosperms, 231-234; cycas, 217

Fibro-vascular system, 48, no

Figwort (family), 285

Flagellates, 119

Florideae, 117

Forget-me-not, 286

Fragaria vesca, 275, 276

Frullania, 72, 154, 155

Fucus, 115, 116, 118

Fumariaceae (Fu-ma-ri-a'ce-ae),
271

Fumitory, 271

Fundamental system, 48

Fungi, 56, 65 ; classification of,
139; nutrition of, 332-337; res-
piration in, 56; wood destroy-
ing, 336, 337

Gametangium (Gam-e-tan'gi-

um), 97
Gamete (Gam'ete), 95-97, 107,

109
Gametophore (Gam-e'to-phore),

145, 147
Gametophyte (Gam-e'to-phyte),

143, 144, 159, 164, 175, 176, 199;

of angiosperms, 228 ; signifi-
cance of, 239-246
Gamopetalous (Gam-o-pet'a-

lous), 284
Gamosepalous (Gam-o-sep'a-

lous), 278, 283
Gases, diffusion of, 49-53
Gaylussacia resinosa (Gay-lus-

sa'ci-a), 283, 284
Gemmae of mucor, 22 ; of mar-

chantia, 153
Gentian, 287
Gentiana crinita, 287
Gentianaceae, 287, 299

440

INDEX.

Geotropism (Ge-ot'ro-pism), 82,

84
Geraniaceae (Ger-a-ni-a'ce-ae),

272, 295, 297

Geum, dissemination of seed, 369
Gingko, 216, 218
Glacier (Greenland), 383
Glumiflorae (Glu-mi-flo'rae), 258,

296
Gonidangium (Go nid-an'gi-um),

121

Gonidiophores, 126, 127

Gonidium (pi. gonidia), 75, 76,
121, 123, 126, 127

Gracillaria, 116, 118, 119

Gramineae, 258, 294, 296

Ground cherry, 285

Growth, 75-81

Gruinales, 272, 297

Guttation, 40, 41

Gymnosperms, 202-220 ; classi-
fication of, 219 ; comparative
table of, 220

Gynandrous, 255

Hamamelis, 414

Haustoria (Haus-to'ri-a), of

fungi, 323, 324
Heliotropism (He-li-ot'ro-pism),

84, 85

Hepaticse, 140
Heterospory (Het-er-os'po-ry),

origin of, 351-353
Hickory, opening buds, 415
Hieracium venosum, 292
Holdfasts, 93, 98, 115
Honeysuckle, 288
Horse-chestnut, 302, 303
Horsetails, 187-190
Houstonia ccerulea, 287
Huckleberry, 283
Hydnum, 337, 338
Hydrotropism (Hy-drot'ro-pism),

90
Hypocotyl (Hy-po-cot'yl), 307,

308

Hyponastic (Hy-po-nas'tic, 86
Hyponasty (Hy-po-nas'ty), 86

Impatiens fulva, 370

Indian corn, osmose in cells of,

16
Indian-pipe, 283 ; mycorhiza of,

320

Indian turnip, 311, 313; forma-
tion of flower, 349

Indusium, 166, 170

Inferior ovary, 255

Insectivorous plants, 90

Integument, 209

Irritability, 82-92

Isoetes (I-so'e-tes), 196-199; hab-
itat of, 395

Isopyrum biternatum, 270

Jack-in-the-pulpit, 311, 313, 349,

350

Jamin's chain, 48
Jungermannia (Jung-er-man'-

ni-a), 156, 157

Kalmia latifolia, 362, 413
Karyokinesis, 240-244
Kinetic energy, 67
Kinoplasm, 241

Labiatae, 286, 295, 299
Lactuca canadensis, dissemina-
tion of seed, 370, 371
Lactuca scariola, dissemination

of seed, 370, 371 ; parahelio-

tropism, 88

Lamium amplexicaule, 286
Leaf, epidermis of, 37; structure

of, 36-38

Leguminosae, 278, 298
Lemanea, 116

Lemna trisulca, nutrition of, 314
Lepiota naucina, 335
Lettuce, prickly, dissemination

of seed, 370, 371; wild, 370, 371
Leucoplasts, 68
Lichens, nutrition of, 316-318;

soil formation by, 381, 384
Ligula, 291

Liliaceae, 251-253, 294, 296
Linin, 240

Linnaea borealis, 288, 289
Liquids, movement of in plants,

42-48
Liverworts, 140 ; nutrition of,

70-72

Lodicules, 259
Lonicera ciliata, 288
Lycopodium cernuum, 193
Lycopodium clavatum, 191, 192
Lycopodium lucidulum, 192
Lycopodium phlegmaria, 193

INDEX.

441

Macrosporangium, 194-199 ; of

pine 207, 209; of cycas, 214; of

trillium, 224
Macrospore, 194-199 ; of angio-

sperms, 229
Maple, 273, 274
Marattia, fertilization, 182
Marchantia, nutrition of, 70, 71;

structure and development,

I447I53

Marsh marigold, 268, 269
Medicago denticulata, 319
Medulla, 44

Micrasterias (Mi-cras-te'ri-as), 98
Microsomes (Mi'cro-somes), 6
Microsphaera (Mi-cro-sphae'ra),

138
Microspore, 194, 197, 199; of pine,

204; of cycas, 215; of trillium,

223
Milkweed, dissemination of seed,

372

Mint family, 286
Mitchella repens, 288
Mnium affine (Mni'um af'fi-ne),

72, 74, 158-161
Monaster, 241
Monocotyledons, 251-261, 294,

296

Monotropa, 283
Morning glory, 284
Mosses, nutrition of, 72; struc-
ture of, 158-163
Mougeotia (Mou-ge-o'tia), 98
Moulds, nutrition of, 322
Mucor, 6-8, 120-123; osmose in,

15; mycelium, 6
Mushrooms 136; studies of, 326-

337; poisonous, 334, 335
Mustard, 272
Mutualism, 318
Mycelium 6, 76, 121, 136; sterile

in coal mines, 325, 326
Mycorhiza, 320
Myrtiflorae, 280, 298

Nettle (dioecious), 265
Nightshade (family), 285, 299
Nitella, 8, 9
Nitrogen, gathered by plants,

318

Nostoc, 118
Nucellus, 209-211
Nuclear plate, 241

Nuclear spindle, 241

Nucleolus, 4

Nucleus 3; morphology of, 239-

244

Nuculiferae, 286
Nutation, 80
Nutrient solution, 22
Nutrition, means for, 70-72;

further studies in, 314

Oak, 263
Oat, 258
CEdogonium (CE-do-go'ni-um),

99-103

CEnothera biennis, 279, 280
Onoclea sensibilis (On-o-cle'a

sen-sib'i-lis), rhizome, 168;

dimorphism of, 340-345
Onograceae, 280, 298
Oogonium (O-o-go'ni-um), 99,

100, 102, 107, 108, 112, 123, 124,

127

Oospore, 100, 108, 128
Orchidaceae, 255, 256, 296
Orchids, pollenation of, 360-363
Oscillatoria (Os-cil-la-to'ri-a), 118
Osmose, 13, 18
Ostrich fern, 345, 346
Ovule of pine, 207; of trillium,

224
Oxygen, 51, 52, 54

Palisade cells, 37

Palms, 257; cocoanut palms, 257

Papaveracese, 271

Papilionaceae, 278, 295, 298

Pappus, 291

Paraheliotropic, 88

Paraheliotropism(Par-a-he-li-ot'-

ro-pism), 90
Parasitic fungi, nutrition of, 322,

323

Parenchyma, 44, 48
Parmelia, fruit of, 318
Parsley, 281
Parthenogenesis, 127
Partridge berry, 288
Passiflorinae, 298
Pea (family), 278
Pear, 277

Peltigera, 316, 317
Pepper, 235
Pepper root, 225
Perigynium, 260

442

INDEX.

Perigynous, 275
Perisperm 234
Perithecium, 136-138
Peronospora alsinearum (Per-o-

nos'po-ra al-sin-e-a'rum), 125,

127, 128
Peronospora calotheca, hausto-

ria of, 324
Personatae, 285, 299
Petaloideae (Pet-al-oi'de-ae), 251,

296
Phaeophyceae (Phae-o-phy'ce-ae),

115, 118

Phloem (Phlo'em), 45, 47, 48
Photosyntax, 61
Photosynthesis, 61
Phycomycetes (Phy-co-my-ce'-

tes), 128
Phyllotaxy, 306
Phytophthota infestans (Phy-

toph'tho-ra in-fes'tans), 126,

127, 128
Picea vulgaris, 212; fertilization

in, 212

Pine, new growth, 416
Pine, white, 202-213
Pines, reforestation by, 378, 379
Pinus strobus, 202-220
Piper nigrum endosperm and

perisperm of, 235
Plant body, 72, 73; members of,

73, 74; leaf series, 74; stem

series, 73; root, 74
Plant communities, 410
Plasmolysis (Plas-mory-sis), 19
Plasmopora viticola (Plas-mop'o-

ra vi-ti'co-Ja), 125, 126, 128
Platycerium alcicorne, 345
Pleurococcus (Pleu-ro-coc'cus),

118, 119

Plum (family), 276
Plumule, 308
Podophyllum peltatum, 229-231 ;

karyokinesis in, 240-243
Pollen, of pine, 204 ; of cycas,

215 ; of trillium, 223
Pollenation, 351-367; of pine, 206,

208
Polycarpicae (Pol-y-car'pi-cae) 268,

297
Polygonacese (Po-lyg-o-na'ce-ee),

267, 297

Polygoniflorae, 267, 297
Polygonum sagittatum, 267

Polymorphic, 135
Polypetalous, 278
Polypodium vulgare, 170, 239
Polyporus (Pol-yp'o-rus), 338
Pomaceae, 276, 295, 298
Pontederia, 406
Poppy (family), 271
Porella, 155
Portulacaceae, 268, 297
Potential energy, 67
Powdery mildews, 136
Primrose, 355, 356
Primula, 284; pollenation of, 356
Primulaceae, 284, 299
Primulinas, 284, 299
Procambium strands, 47
Progeotropism (Pro-ge-ot ro-

pism), 82, 83
Promycelium (Pro-my-ce li-um),

134-136

Proterandrous, 360
Proterandry, 362
Proterogynous, 360
Prothallium, of ferns, 176-182;

of pine, 209, 210; of cycas, 214,

215; of angiosperms, 228-233
Protococcoideae (Pro-to-coc-coi'-

de-ae), 118, 119
Protococcus (Pro-to-coc'cus), 118,

119
Protonema (Pro-to-ne'ma), 163,

178, 180
Protoplasm, 1-12; movement of,

7-1 1

Prunus virginiana, 277
Pteridophyta (Pter-i-doph'y-ta),

200, 201

Pteris aquilina, 178
Pteris cretica, 245
Pteris serrulata, spores of, 177 ;

embryo of, 183, 186
Puccinia graminis, 129-136
Pumpkin, roots of, 77, 78
Pumpkin seed, germination of,

309-311
Purslane, 268
Pyrenoid, 2
Pyrolaceae, 283, 299
Pyrola elliptica, 283

Quercus rubra, 263
Quillworts, 196-198

Ranunculaceae, 268, 294, 297

INDEX.

443

Rattlesnake-weed, 292

Red algae, 116, 119

Red rust, 129

Red-snow plant. 118, 119

Reforestation of lands, 376, 379

Respiration, 54-58; intramolecu-
lar, 58

Rhabdonia (Rhab-do'ni-a), 117,
119

Rhizoids (Rhi'zoids), 71, 72

Rhizome, of trillium. 221

Rhizomorphic (Rhi-zo-mor'phic),

325
Rhizopus nigricans (Rhi'zo-pus

ni'gri cans), 120-123
Rhododendron nudicaulis, 411
Rhodophyceae (Rho-do-phy'ce-

ae), 116, 119, 139
Rhceadineae, 271, 297
Rock lichens, 382-384
Root hairs, 24; absorption by, 19,

25, 26; acidity of, 27; corrosive

action of, 27
Root pressure, 31, 32, 39, 40 ;

periodicity of, 32; variation of,

32

Root tubercles, 318
Rosa, 276

Rosaceae, 275, 295, 298
Rose (family), 275
Rosiflorae, 275, 298
Rubiales, 288
Rubus odoratus, 275, 276
Russian thistle, 268
Rusts, 129 -

Sac fungi, 136-138
Sagittaria, 255

Sagittaria heterophylla, 402-404
Sagittaria variabilis, 400, 404
Salicaceae, 262, 294, 296
Salsola soda, 268
Sand dunes, vegetation of, 376
Sanguinaria canadensis, 271
Saprolegnia, 123—126
Saxifraga virginiensis, 274
Saxifragaceae, 274, 298
Saxifraginae, 274, 298
Scorophulariaceae, 285. 299
Seeds, distribution of, 368, 373
Selaginella, 193-195, 199-201
Sensitive fern, dimorphism of,

340-346
Sensitive plants, 89, 90

Silkweed, dissemination of seeds,

372

Silphium laciniatum, 88
Siphoneae (Si-pho'ne-ae), 109, 118
Skunk's cabbage, 356, 357
Soil formation, 381-388
Solanaceae, 285, 299
Sorus, of ferns. 166, 170, 173
Spadiciflorae, 257, 296
Spadix, 257
Spartium, scattering of pollen,

364

Spathe, 257

Spathyema fcetida, 257

Spectrum, bands in, 67 ; absorp-
tion bands of, 67

Spermagonia, 132

Spermatia, 132

Spermatozoids in gymnosperms,
216-219

Sperm cells, 146

Sphaerella nivalis (Sphae-rel'la
ni-va'lis), 118

Sphaerotheca (Sphae-ro-the'ca),
138

Sphagnum in moors, 386—394 ;
structure of leaves, 394

Spiderwort, II

Spirodela polyrrhiza, 315

Spirogyra, 2, 93-98

Sporangium, of ferns, 167-175

Spores, of riccia, 143 ; of ferns,
169-172 ; of equisetum, 188

Sporidium, 134, 136

Sporocarp, 112, 113

Sporogonium (Spor-o-go'ni-um)
of riccia, 142 ; of marchantia,
149, 150; of foliose liverworts,
I55~I57 J °f mosses, 161, 162

Sporophyte (Spor'o-phyte), 143,
144, 150, 152, 156, 157. 159,104.
175, 182, 199; of angiosperms,
228 ; significance of, 239-246

Squirrel corn, 271

Staghorn fern, 345

Starch, 59; test for, 59, 60; trans-
location of, 61; where found,
60, 61, 63

Starch grains, form of, 63

Staurastrum (Stau-ras'trum), 98

Sterigma, 134

Stoma (pi. Stom'a-ta), 38 ; action
of, 39 ; demonstration of, 41

Strobilus, 192

444

INDEX.

Sundew, go

Symbiosis, 318

Sympetalae, 283, 298

Synergids (Syn-er'gids), 231, 233

Taxodium distichum, 395
Teasel, 289
Teleutospore, 130, 135
Temperature, 91, 92
Tensions, tissue, 29, 30
Tetraspores, 117
Tissues, synopsis of, 48
Touch-me-not, dissemination of

seed, 370

Transpiration, 33-41
Trichomes, 48
Trillium erectum, 251
Trillium grandiflorum, 221-224 ;

formation of flower, 347, 348
Tubiflorse, 284, 299
Turgescence, 14, 28
Turgescent, 15
Turgid, 15

Turgidity, 28 ; restoration of, 28
Twin flower, 289

Ulmacese, 266, 294, 297
Umbelliflorse, 281, 298
Uncinula, 136, 138
Unifolium, 254
Uredineae(U-re-din'e-ae), 129-136,

139

Uredospore, 131, 135
Uromyces caryophyllinus, 323
Urtica, 265
Urticaceae, 265, 297
Urticiflorae.,265, 297

Vascular bundle, 43 ; structure

of, 44-47

Vaucheria, 105-109
Vaucheria geminata, 108

Vaucheria sessilis, 106-107

Vessels, 45, 46

Vetch, root tubercles of, 318, 319

Vicia sativa, dissemination of
seed, 369

Viola cucullata, 354

Violet, endosperm and embryo,
235 ; pollenation of, 353, 354

Virgin's bower, 269, 270 ; dis-
semination of seed, 372, 373

Volva, 334, 335

Wake robin, 221

Walking fern, 173, 413

Water moulds, 123-126

Water plantain, 254

Water vapor, 34

Wheat rust, 129

Whortleberry, 283

Wild carrot, 281, 282

Willow, 262

Witch hazel, 414

Wolffia, 315

Wood fibres, 48; parenchyma, 48

Xanthidium, 98
Xylem, 44, 45, 47, 48

Yellow water lily, 407

Zamia, 219

Zamia integrifolia, 216

Zonal distribution of plants,

400-408
Zoogonidium (Zo-o-go-nid'i-um),

TOI, 102, 105, 106
Zoospores, 101, 103, in, 112
Zygnema (Zyg-ne'ma), 98
Zygomorphic, 289
Zygospore (Zy'go-spore), 2, 95

97, 98, 122
Zygote (Zy'gote), 95, 122

July, 1898.

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For this purpose he has skillfully employed a brilliant style of exposition, and he has not
hesitated to use illustrations in black and in color with the freest hand. The purpose has
been attained. He has succeeded in constructing a popular work on the phenomena of
vegetation which is practically without any rival. The German edition has been accepted
from the first as a useful treatise for the instruction of the public ; in fact, some of its illus-
trations have been taken, bodily from the volumes by museum curators, to enrich exhibi-
tion cases designed for the people. With two exceptions, the full-page colored plates
leave little to be desired, and might well find a place in every public museum in which
botany has a share. Most of the minor engravings are unexceptionable. They are clear,
and almost wholly free from distracting details which render worthless so many iflustra-
tions in popular works on natural history. Professor Kerner's style in German is seldom
obscure — it is what one might fairly call easy reading; but it is no disparagement to him
and his style tostate that the translation is clearer than the original throughout. . . In the
first two issues the author was engaged chiefly with the study of the structure of the plant,
and its adaptation to its surroundings. In this concluding volume he considers the plant
from the point of view of its relation toothers. Therefore he begins with a full and ab-
sorbingly interesting account of reproduction in the vegetable kingdom, and then passes to
an examination of species. . . With this book, there is no excuse for even busy people to
be ignorant of how the other half, the plant-half, lives."

Botanical Gazette : " Kerner's work in English will do much toward bringing- modern
botany before the intelligent public. We need more of this kind of teaching that will
bring those not professionally interested in botany to some realization of its scope and
great interest."

Professor J. E. Humphrey : " It ought to sell largely hereto colleges and public libra-
ries, as well as to individuals, and I can heartily commend it."

John M, Macfarlane, Professor in University of Pennsylvania : " It is a work that
deserves a wide circulation."

Professor John M. Coulter in The Dial : "It is such books as this that will bring
botany fairly before the public as a subject of absorbing interest ; that will illuminate the
botanical lecture-room ; that will convert the Gradgrind of our modern laboratory into a
student of nature."

New York Times : " A magnificent work, with its careful text and superb illustrations.
The whole processof plant life is explained, and all the wonders of it."

The Critic : " In wonderfully accurate but easily comprehended descriptions, it opens
to the ordinary reader the results of botanical research down to the present time."

The Outlook : ". . . For the first time we have in the English language a great work
upon the living plant, profound, in a sense exhaustive, thoroughly reliable, but in language
simple and beautiful enough to attract a child. . . Theplatesare most of them of unusual
beauty. Author, translator, illustrators, publishers, have united to make the work a
success."

HENRY HOLT & CO., 29 West 23d Street, New Tort

October, 1893

HENRY HOLT & CO.'S
RECENT BOOKS

The Publishers'1 Catalogue of GENERAL LITERA-
TURE, including History, Biography, Travels, Fine
Arts, Fiction, etc., etc., or their neiu Educational
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New York.

PUGH'S TONY DRUM, A COCKNEY BOY

With a cover and ten most striking illustrations in c^lor by WIL-
LIAM NICHOLSON, whom so great an authority as Whistler has called
the greatest living English illustrator. The author is already known
through his versatile and forceful volume of stories, King Circum-
stance. 1 2 mo.

For King Circumstance, see page 2 of this circular.

CORNISH'S CONCISE DICTIONARY OF GREEK
AND ROMAN ANTIQUITIES

Based on SIR WILLIAM SMITH'S larger work and edited by F.

WARRE CORNISH, Vice-Provost of Eton College. 8vo. $4.00, net.

The latest and perhaps the best book on the subject, inspired
throughout by the most recent result of excavation. It has 829
pages and some 1100 illustrations.

LANGLOIS & SEIGNOBOS' INTRODUCTION TO
THE STUDY OF HISTORY

Translated by G. G. BERRY. With a preface by F. YORK

POWELL. i2mo. $2.25, net, special.

A practical book on method for historians and students of history.
It discusses the problem of investigation, such as the Search for
Documents, Textual Criticism, and the Critical Classification of
Sources; also the Problems of Construction, such as the Grouping
of Facts, Constructive Reasoning, and Exposition.

A NEW VOLUME IN THE AMERICAN SERIES

THE SCIENCE OF FINANCE

By HENRY C. ADAMS, Professor in the University of Michigan.

8vo.

The author is probably the leading American authority on the
subject, and here lays special stress upon the necessities of tb'
American people.

TARBET'S FIGHTING FOR FAVOUR

A Romance of Sixteenth-century Scotland. 12010. $1.25.

N. Y. Times: " The style is pleasing. . . . The movement is rapid
and the interest well sustained.11

Buffalo Express : " The fighting and love-making are more than
commonly real and exciting.1'

HENRY HOLT & CO.'S RECENT BOOKS

RINGWALT'S MODERN AMERICAN ORATORY

12010. $1.00, net.

Schurz's General Amnesty, Black's Trial by Jury, Phillips' Dan-
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FORD'S THE FEDERALIST

The well-known collection of papers on the Constitution by
HAMILTON, JAY, and MADISON. Edited by PAUL LEICESTER FORD,
editor of The Writings of 7 homas Jefferson. With foot-notes
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JENKS' LAW AND POLITICS IN THE MIDDLE

AGES With a synoptic table of sources. 8vo. $2.75, net.

Harvard Law Review : " A valuable contribution to legal history.
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PUGH'S KING CIRCUMSTANCE

i?mo. $1.25.

Boston Transcript : " A volume of short stories, each of which has
its own strong, peculiar vein of interest and reality. . . . Each story
is in itself strikingly complete. . . . The writer of these short stories
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ELLIOTT'S THE DURKET SPERRET

A Romance of the Cumberland Mountains. (Uniform with the
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The Nation : " A homespun heroine in whose possibility one is
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New York Tribune : " Worth reading a second time."

New York Commercial Advertiser : "Strengthens Miss Elliott's
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ous."

Independent: "Decidedly above the common. Its descriptive
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the mountain cirl chosen for the heroine are excellent."

NewYorkTiw.es : " The utter sincerity and naturalness of dialogue
are features that should claim particular attention,'1

13th IMPRESSION OF A "POWERFUL NOVEL"

VOYNICH'S THE GADFLY

iamo. $1.25.

New York Tribune : " It is nothing more or less than one of the
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A BOOK FOR OLD AND YOUNG

LUCAS' A BOOK OF VERSES FOR CHILDREN

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Chicago Post : " Will interest the old hardly less than the young."

BURROW'S THE FIRE OF LIFE

i2mo. $1.25.

Boston Transcript: "Exceedingly entertaining and taking. . . .
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The Independent: "This charmingly simple and sweet novel
. . . belongs to a class (far too small) of fiction that leaves a good
taste in the mind after reading."

kth IMPRESSION OF A CHARMING BOOK

JEROME'S SKETCHES IN LAVENDER, BLUE,

AND GREEN With 40 illustrations. 121110. $1.25.

Boston Transcript: " A humorist whose humor is of the exquisitely
pleasing kind that delights by its delicate exaggeration of the common
faults and foibles of humanity, without offending by descending to
mere burlesque; . . . there is in his work much of both wit and phi-
losophy. . . . Several of the tales have a strong emotional interest;
they are all original and well told."

List of Mr. Jerome K. Jerome's books on application.
6th IMPRESSION OF A WORK ON CUBA TO- DA Y

ROWAN & RAMSEY'S ISLAND OF CUBA

With maps, points of international law, etc. i6mo. $1.25.
Boston Transcript : " So graphic, at times picturesque, that read-
ing for information is an intellectual delight.

28 t h IMPRESSION OF THE AMERICAN NOVEL

FORD'S THE HON. PETER STIRLING

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A NEW FOUR-VOLUME EDITION OP

TAINE'S ENGLISH LITERATURE

With 28 portraits. Gilt tops. In box. $7.50.
The Dial : "The most satisfactory edition for library use that we
have in English."

KERNER'S NATURAL HISTORY OF PLANTS

With over 2000 illustrations (16 of them in colors).

4 parts. 8vo. Cloth, $15.00, net ; carriage $1.00.
New York Times: "A magnificent work; . . . superb illustrations."
The Nation : " The lucidity of style is remarkable."

5th IMPRESSION OF THE SEQUEL TO
" THE PRISONER OF ZENDA "

HOPE'S RUPERT OF HENTZAU

With eight illustrations by CHARLES DANA GIBSON. 12010. $1.50.

Critic : "Even better than 'The Prisoner of Zenda.' . . . Mov-
ing swiftly, from a simple beginning to an impressive climax."

Life: " Does not let down one bit the high standard of chivalrous
love which was the charm of that romance " [" Zenda "].

Dial : " Our chief regret is that further volumes in the series are,
at least, improbable."

E. A. Dithntar in N. Y. Times'1 Saturday Review : " A sequel for
a wonder as vigorous and powerful as its original."

Geo. IV. Smalley in N. V. Herald : " A story which lays a spell
upon you. The animation is unceasing.'1

A NEW ILLUSTRATED EDITION OF

HOPE'S PRISONER OF ZENDA

(Being- the 481/1 Impression of this romance.}

With five full-page illustrations by C. D. GIBSON, and a view and
plan of the castle by HOWARD INCE. i^mo. $1.50.

OTHER BOOKS BY ANTHONY HOPE

With frontispieces by RACKHAM, RUSSELL, and WECHSLER. i8mo.
7SC. each.

The Indiscretion of the Duchess, \-zth Impression; The Dolly Dia-
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4th IMPRESSION OF A HUMOROUS TALE

WELLS' (D. D.) HER

LADYSHIP'S ELEPHANT

With cover by WM. NICHOLSON. i2mo. $1.25.

The Nation : " He is probably funny because
he cannot help it. ... Its author must consent
to be regarded as a benefactor of his kind with-
out responsibility."

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Express: "Mr. Wells has more than enough
humor to tell his story in a very natural and
laughable way. He has a great deal of comic
talent."

Chicago Evening Post : " An instantaneous
success. . . . The most read story of the season."

New York Tribune: " Mr. Wells allows his
sense of humor to play about the personalities
of half a dozen men and women whose lives,
fora few brirf, extraordinary days, are irextri
From the back of Wm cablv intertwined with the life of the aforesaid
Nicholson's cover jor monarch of the jungle. . . Smacks of fun

Elt- '0'8 piaced

HENRY HOLT & CO. 2e wNees

THE METRIC SYSTEM.

io-centimeter rule. The upper edge is in millimeters, the lower in centimeters and half-
centimeters.

UNITS. THE MOST COMMONLY USKD DIVISIONS AND MULTIPLES.

Centimeter (cm), i/ioo meter; Millimeter (mm),

THE METER, for

i/iooo meter; Micron (//), i/iooo millimeter. The

micron is the unit in micrometry.

Kilometer, 100 meters; used in measuring roads and other

long distances.

THF GRAM for ( MilliSram (rag)> VIOO° gram-

WEIGHT 1 Kil°Srami I00° grams, used for ordinary masses, like

( groceries, etc.

THE LITER, for j Cubic Centimeter (cc), i/iooo liter. This is more
CAPACITY. ... ( common than the correct form, Milliliter.
Divisions of the units are indicated by Latin prefixes: deci, i/io; centi,

I/ioo; milli, i/iooo.

Multiples are designated by Greek prefixes: deka, 10 times; hecto, 100

times; kilo, 1000 times; myria, 10,000 times.

TABLE OF METRIC AND ENGLISH MEASURES.

METER = 100 centimeters, 1000 millimeters, 1,000,000 microns, 39.3704
inches.

Millimeter (mm) = looo microns, I /io millimeter, i/iooo meter, 1/25 inch,
approximately.

MICRON (fi) (unit of measure in micrometry ) — i/iooo mm, i/ioooooo me-
ter (0.000039 inch), 1/25000 inch, approximately.

Inch (in.) = 25.399772 mm (25.4 mm, approx.).

LITER = 1000 milliliters or 1000 cubic centimeters, I quart (approx.).

Cubic centimeter (cc or cctm) = i/iooo liter.

Fluid ounce (8 fluidrachms) = 29.578 cc (30 cc, approx.).

GRAM — 15.432 grains.

Kilogram (kilo) = 2.204 avoirdupois pounds (2\ pounds, approx.).

Ounce Avoirdupois (437^ grains) = 28.349 grams ) (30 grams,

Ounce Troy or Apothecaries' (480 grains) = 31. 103 grams ) approx. ).

TEMPERATURE.

To change Centigrade to Fahrenheit: (C. X f) +32 = F. For example, to
find the equivalent of 10° Centigrade, C. = 10°, (10° X f ) + Z2 = 5°° F-

To change Fahrenheit to Centigrade: (F. — 32°) X f = C. For example,to
reduce 50° Fahrenheit to Centigrade, F. = 50°, and (50°— 32°) X f = 10° C. ;
or - 40° Fahrenheit to Centigrade, F. = —40°, (- 40°- 32°) = - 72°,

A = _ 40° C.
— From "The Microscope" (by S. ff. Gage) by permission.

University of Toronto
Library

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