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THIS BOOK IS DUE ON THE DATE
INDICATED BELOW AND IS SUB-
JECT TO AN OVERDUE FINE AS
POSTED AT THE CIRCULATION
DESK.



JAN -4 1984



Camfariiige Natural ^nenre iMamiate

Biological Series.
General Editor: — Arthur E. Shiplev, M.A.

FELLOW AND TUTOR OF CHRIST's COLLEGE, CAMBRIDGE.



»■ C. COIIEGE OTA.&Ui



PRACTICAL
PHYSIOLOGY OF PLANTS.



aonton: C. J. CLAY and SONS,

CAMBRIDGE UNIVERSITY PRESS WAREHOUSE,
AVE MARIA LANE,

AND

H. K. LEWIS,
136, GOWEK STREET, W.C.




(Slassoto: 263, ARGYLE STREET.

ILcipjig: F. A. BROCKHAUS.

i^cia lorfe: MACMILLAN AND CO.

JSombag: GEORGE BELL AND SONS.



PRACTICAL

PHYSIOLOGY OF PLANTS



BY



FRANCIS DARWIN, M.A., F.R.S.,

FELLOW OF Christ's college, Cambridge,

AND READEB IN BOTANY IN THE UNIVERSITY,



AND

THE LATE E. HAMILTON ACTON, M.A.,

fellow and lectubeb of ST John's college, Cambridge.



WITH ILLUSTRATIONS.



SECOND EDITION.



CAMBRIDGE :
AT THE UNIVERSITY PRESS.

1895

[All lUghts reserved.]



First Edition Oct. 1894
Second Edition Oct. 1895



CAMBRIDGE : PRINTED BY J. AND C. F. CLAY,
AT THE UNIVERSITY PRESS.



PREFACE.

Edward Hamilton Acton died in the early part of
the present year. This is not the place to speak of what
we, his friends, have lost by his death, nor of his promising
career as a man of science. All that I can do here is to
explain in what way I have dealt with that part of the
book for which he was especially responsible.

Part II, on the chemistry of metabolism, was entirely
written by Mr Acton, and is here reprinted practically as
he left it. The only changes are two or three corrections
found in his interleaved copy of the book, and a few verbal
and typographical alterations introduced for the sake of
uniformity.

The book (as explained in the preface to the 1st Edition)
originated in the following way.

In 1883 I began a course of instruction in the
physiology of plants, of which the chief feature was the
demonstration of experiments in the lecture-room. Some



my



17140



VI PREFACE.

years later a different arrangement was made ; the students
were required to perform the experiments for themselves,
and at the same time laboratory work in the chemistry of
metabolism was organised by Mr Acton. To enable the
students to carry out their work, written instructions
were needed, and the present book is the result of an
extension and elaboration of what we prepared for our
classes.

The book makes no pretence to completeness, it
contains merely such a selection of experimental and
analytical work as seems suitable for botanical students.

Part I, which deals with general physiology, is
necessarily of a somewhat more elementary character
than Part II, which treats a particular department of
physiology in a more special manner, and presupposes a
greater amount of knowledge on the part of the student.

A few experiments which experience has shown to
be unsuitable have been omitted in the present edition.
The chief additions are: — Exps. 5 and 52 (Timiriazeff's
eudiometer), Exp. 83 (the importance of stomata in
gaseous interchange), Exps. 118 a, 118 b, 118 c (Stahl's
cobalt method), Exp. 205 A (Pfeffer and Czapek's method
of localising geotropic irritability in roots), Exp. 249 A
(chemotaxis in Bacteria), Exps. 249 B and c (chemotaxis
in pollen-tubes).



PREFACE. vil

The references to the literature of Part I have been
increased in number, and they now give a fuller, though
still but a rough guide to the published authorities. The
references to Sachs' books appear to have been a source
of difficulty to some of our readers. I therefore give
the full titles of those to which reference is made.

Physiologie Vegetate, recherches su7^ les conditions
d'existence des plantes, et sur le jeu de leurs organes.
Traduit de I'Allemand avec I'autorisation de I'auteur,
par Marc Micheli. Paris, V. Masson et Fils, 1868. [This
is the translation of Sachs' Handhuch der Eooperimental-
Physiologie der Pflanzen, being volume iv of Hofmeister's
Handhuch der Physiologischen Botanik, Leipzig, 1865.

Arbeiten des hotanischen Instituts in Wurzbiirg, heraus-
gegeben von Prof Dr Julius Sachs. Leipzig, Engelmann.
Band i. 1874, Band ii. 1882, Band ill. 1888.

Text-hook of Botany, moiyhological and physiological,
by Julius Sachs, Professor of Botany in the University of
Wlirzburg. Edited with an Appendix by Sidney H. Vines,
M.A., D.Sc, F.L.S., Fellow and Lecturer of Christ's
College, Cambridge. Second Edition, Oxford, at the
Clarendon Press, 1882. [This is a translation of Sachs'
Lehrbuch der Botanik (Edit. 1874).]

Vorlesungen uher Pflanzen-Physiologie von Julius
Sachs. Leipzig, Englemann, 1882. [An English trans-

D. A. b



Vlll PREFACE.

lation was published in 1887 by the Clarendon Press
under the title Lectures on the Physiology of Plants.]

Gesammelte Ahhandlungen ilber Pflanzen-Physiologie
von Julius Sachs. Leipzig, Engelmann. Band I. 1892,
Band ii. 1893. [This is referred to in the text as Sachs'
Collected Papers^

I gladly take this opportunity of expressing my thanks
to Mr F. F. Blackman, Demonstrator of Botany in the
University, for much valuable help in the arrangement of
the experiments in Part I. Also to the Cambridge
Scientific Instrument Company for the use of the cliches
for Figs. 25 and 26.

FRANCIS DARWIN.



Botanical Laboratory, Cambridge.
September, 1895.



CONTENTS,



PART I.

GENERAL PHYSIOLOGY.
CHAPTER I.

ON SOME OF THE CONDITIONS AFFECTING THE LIFE OF PLANTS.

Section A. Respiration. 1. Eespiration ; production of COg
by germinating seeds or buds. 2. Absorption of COo by potash.
3. Sachs' method. 4. Winkler-Hempel apparatus. 5. Timiriazeff's
Eudiometer. 6, 7, 8. Intramolecular respiration. 9, 10. Kise of
temperature during respiration. 11. Succulents . pp. 1 — 13.

Section B. The effect of various temperatures: of certain
poisons : and of electrical shock. 12. Injurious temperature
demonstrated on Oxalis leaf. 13. Do., injected leaf. 14. Do.,
beetroot. 15. Do., dry and soaked seeds. 16. Circulation of pro-
toplasm, Sachs' hot-box. 17. Velten's method. 18. Circulation
of protoplasm, effect of CO.,. 19. Do., chloroform. 20. Oxalis
leaf killed by chloroform. 21. Do. by phenol. 22. Do. by
induced current. 23. Effect of induced current on circulating
protoplasm pp. 14 — 20.

b'2



CONTENTS.



CHAPTER II.

ASSIMILATION OF CARBON.

Section A. rormation of starch. 24. Sachs' Iodine method.
25. Schimper's method. 26. Variegated leaves. 27. Disappear-
ance of starch in darkness, 28. Effect of dull light. 29. Local
effect. 30. Gardiner's experiment. 31. Kays of different refran-
gibility. 32. Terrestrial leaves under water. 33. Stomata and gaseous
exchange. 34. Excess of CO2. 35. Plants deprived of COo. 36. Gain
in weight. 37. Translocation. 38. Assimilation of sugar. 39. Do.,
formaldehyde. 40. Leucoplasts pp. 21 — 34.

Section B. Evolution of oxygen. 41. Bubbles of gas.
42. Light of varying intensity. 43. Dependence on presence of CO2.
44. Temperature and gas evolution. 45. Chloroform. 46. Co-
loured lights. 47. Collection of gas evolved. 48. Engelmann's
blood method. 49. Phosphorus method. 50. Gas analysis, Pfeffer's
method. 51. Gas analysis, Winkler-Hempel apparatus. 52. Timiria-
zeff's Eudiometer. 53. Engelmann's bacterial method. 54. Diffusion
of gas through cuticle pp. 35 — 49.

Section C. Reactions of chlorophyll and of some other pig-
ments. 55. Separation by benzene, ether, olive oil. 56. Action
of light. 57. Aeration and effect of light. 58. Action of acid.
59. Action of copper salts. 60. Stability of the copper compound.
61. Spectroscopic examination. 62. Anthocyan in Kicinus, &c.
63. Floridese. 64. Brown sea-weeds . . . pp. 50— 53.

Section D. Production of chlorophyll, etiolation, sun- and
shade-leaves. 65. Appearance of the green colour. 66. Etiolin
and light. 67. Pinus. 68. Chlorophyll formation and tempera-
ture. 69, 70. Do. and oxygen. 71. Do. and iron salts.
72. Form of etiolated plants. 73. Sun- and shade-leaves.

pp. 54—57.

CHAPTER III.

FURTHER EXPERIMENTS ON NUTRITION.

Section A. Water-culture. 74. Method. 75. Potassium
salts necessary. 76. Phosphoric acid necessary. 77. Experi-
ments with Lemna. 78. Calcium oxalate formation. 79. Nitrate
reaction pp. 58 — 67.



CONTENTS. XI

Section B. Nutrition of Fungi and of Drosera. 80. Method.
81. Various cultures. 82. Puccinia. 83. Hanging-drop cultures.
84. Germination of spores. 85. Drosera, digestion of white of egg.
86. Drosera, benefit from feeding .... pp. 68 — 72.

Section C. Functions of roots. 87. De Saussure's experiment.
88, 89, 89 A. Eoot pressure. 90. Moll's experiment. 91. Absorption
by means of dead roots . pp. 73 — 78.

CHAPTER IV.

TRANSPIRATION.

Section A. Absorption of water. 92. Potometer. 93. Kohl's
method. 94. Effect of sunshine. 95. Effect of wind. 96. Effect
of light. 97 — 100. Negative pressure. 101. Permeability of mem-
branes. 102. Oozing of water from wood. 103. Permeability of
splint-wood. 104. Recovery of flaccid shoot. 105. Emulsion ex-
periment. 106, Injection with cocoa-butter. 107. Compression.
108. Incisions. 109. Cross-cuts. 110. Do,, course shown by
eosin. 111. Air-pump and potometer. 112. Strasburger's air-
pump experiment pp. 79 — 96.

Section B. Loss of water. 113. Loss of weight during transpi-
ration, 114. Transpiration compared with evaporation from water.
115. Loss compared with absorption. 116. Spring balance.

pp. 97— lOl.

Section C. Stomata, bloom, lenticels. 117. Stomatal trans-
piration. 118, Stipa-hygrometer. 118a. Stahl's cobalt method.
118 b. Stomata in withered leaves, 118 c. Effect of salt on the
stomata, 119, Stomata and intercellular spaces, 120, Leaf injected
with water. 121. Frost effects, 122, Blocking of stomata with water.
123. Movements of stomata. 124. Do, with induced current.
125. Lenticels and intercellular spaces. 126. Bloom as affecting
transpiration pp. 102 — 111.

CHAPTER V.

PHYSICAL AND MECHANICAL PROPERTIES.

Section A, Imbibition, hygroscopic movements, polariscope,
osmosis. 127, Laminaria, microscopic observation, 128. Lami-
naria, increase not uniform in all directions. 129. Imbibition of seeds.



XU CONTENTS.

temperature effect. 130. Imbibition ; salt solution. 131. Stipa,
action of. 132, 133. Stipa, temperature. 134. Stipa, salt solu-
tion. 135. Stipa, mechanism of movement. 136. Nobbe's ex-
periment. 137. Variability in the swelling of seeds. 138. Kise
of temperature accompanying imbibition. 139. Work done during
imbibition. 140. Polariscope. 141, Polariscope, observations on
strained glass rods. 142. Traube's artificial cell. 143. Slowness of
diffusion. 144. Kelation of membrane to diffusing fluid. 145. Absorp-
tion of methylene blue by living cell . . . . pp. 112 — 124.

Section B. Tiirgor. 146. Plasmolysis, microscopic observations.
147. Kecovery after plasmolysis. 148. Osmotic strength of cell-sap
in terms of KNOg. 149. Isotonic coefficient. 150. Do., micro-
scopic method. 151. Hydrostatic pressure in turgescent tissue.
152. Pfeffer's gypsum method pp. 125—132.

Section C. Tensions of tissues. 153. Longitudinal tensions.
154. Extension of pith in water. 155. Changes in transverse di-
mensions of pith. 156. Tangential dimension. 157. Shortening
of roots. 158. Imperfect elasticity of tissues. 159. Cyclometer.
160. Hofmeister's experiment. 161. Loss of rigidity. 162. In-
crease in length. 163. Splitting turgescent tissues. 164. Split-
ting a root. 165. Splitting a pulvinus . . . pp.133 — 141.



CHAPTER VI.

GROWTH.

Section A. Experiments witliout special apparatus. 166. Method.
167. Free oxygen necessary. 168. Respiration necessary, 169. Effect
of salt solution. 170. Growth at various temperatures.

pp. 142—145.

Section B. Distribution of growth. 171. Distribution in roots.
172. In air-roots. 173. In stems. 174. Grand period, time
observation. 175. Growth and plasmolytic shrinking pp. 146 — 148.

Section C. Auxanometers. 176. Methods. 177. Descent
of the weight measured on a scale. 178. Micrometer screw.
179. Arc-indicator. 180. Microscope. 181. Self-recording aux-
anometer. 182. Do., simple form. 183, 184. Growth and tem-
perature, microscopic method. 185. Growth and respiration, micro-



CONTENTS. XIU

scopic method. 186. Growth and temperature, auxanometer.

187. Growth and light, auxanometer. 188. Growth and Hght,

Phycomyces. 189. Growth and light, Sinapis. 190. Periodicity,
auxanometer ........ pp. 149 — 162.



CHAPTER VII.

CURVATURES.

Section A. Geotropism. 191. Eegion of growth and region of
curvature, roots. 192. Do., stems. 193. Subsequent changes in
curvature. 194. Grass-haulms. 195. Noll's experiment, grass-

haulms. 196, 197. Geotropism and respiration. 198. Johnson's
experiment. 199. Pinot's experiment. 200. Knight's experiment.
201. Sudden curvature. 202, 203. After effect . pp. 163—172.

Section B. Curvatures due to injury &c. 204. Decapitated

roots. 205. Decapitation prevents perception of stimulus. 205 a. Do.,
Pfeffer's experiment. 206. Recovery after decapitation. 207. Cur-
vature due to injury. 208. Ciesielski's experiment. 209. Drooping
of leaves in frost pp.173 — 179.

Section C, Heliotropism. 210. Positive heliotropism. 211. After
effect. 212. Light of high refrangibility most effective. 213. Nega-
tive heliotropism. 214. Struggle between the effects of light and
gravitation. 215. Transmitted stimulus . . pp. ISO — 183.

Section D. Diaheliotropism, diageotropism &c. 216. Diahelo-
tropism. 217. The movements due to specific sensitiveness ; klinostat.
217 A. Exclusion of helio- and geotropism. 218. Rectipetality.

219. Theory of klinostat, grass-haulms. 220. Do., Cucurbita.

221. Diageotropism, roots. 222. Growth of secondary roots in Hght.
223. Diageotropism, Narcissus. 224. Horizontal branches. 225. Tor-
sion of internodes. 226. Buds of the yew. 227. Epinasty.
228. Epinasty and geotropism. 229. Nutation of epicotyls

pp. 184—199.

CHAPTER VIII.

FURTHER EXPERIMENTS ON MOVEMENT.

Section A. Stimulus of contact, chemical agency, moisture,
changes in illumination and temperatvire. 230. Tendrils, sensi-



XIV CONTENTS.

tive to contact. 231. Tendrils, Pfeffer's contact experiment. 232. Mi-
mosa, movements produced by stimulation, 233. Mimosa, temperature.
234. Mimosa, darkness. 235. Mimosa, continued stimulation.
236. Oxalis acetosella, sensitiveness. 237. Oxalis, Briicke's experi-
ment. 238. Drosera, stimulated by meat. 239. Do., by inorganic
matter. 240. Drosera stimulated by dilute solutions. 241. Drosera,
inflection indirectly caused. 242. Berberis, irritable stamens.
243. Berberis, effect of chloroform. 244. Stigma of Mimulus.
245. Centaurea, irritable stamens. 246. Phycomyces, curvature
towards iron. 247. Hydrotropism. 248. Movement of chloroplasts.
249. Chemotaxis, antherozoids. 249 a. Chemotaxis: bacteria.
249 b, c. Do., pollen tubes. 250. Opening and closing of tulip,
temperature. 251. Tulip, sensitive to small change of temperature.
252. Crocus, mechanism of movement. 253. Light and darkness,
daisy. 254. Light and darkness, Trifolium. 255. Nyctitropic

movements, Trifolium. 256. Do., Mimosa, self-recorded. 257. Para-
heliotropism, Averrhoa pp. 200 — 226.

Section B. Autonomous movements. Periodicity. 258. Cir-
cumnutation. 259. Do., twining plants. 260. Autonomous

movements, Trifolium. 261. Do., Averrhoa. 262. Do., Desmo-

dium. 263. Periodicity, light and darkness, daisy. 264. Perio-

dicity, temperature, daisy. 265. Contrast, daisy pp. 227 — 234.



PART II.

CHEMISTRY OF METABOLISM.
CHAPTER IX.

INTRODUCTION. SOLVENTS. METHODS OF EXTRACTION.
GENERAL NOTES ON APPARATUS AND MANIPULATION.

Introductory. Preparation of material to be examined. Preparation
of extracts : non-nitrogenous plastic substances. Preparation of ex-
tracts: nitrogenous plastic substances. Filtration. Evaporation of
solutions. Changes occurring in solutions on keeping pp. 237 — 248.



CONTENTS. XV

CHAPTER X.

PROTEIDS. AMIDES. AMMONIA. NITRATES, &C.

Literature. Practical classification of nitrogenous plastic sub-
stances. Qualitative examination for proteids insoluble in water, soluble
in dilute alkali — for proteids soluble in water — for peptones and albu-
moses — for amides — for ammonia, nitrates, nitrites. Estimation of
proteids — of peptones and albumoses. Estimation of amides. Estima-
tion of ammonia, nitrates and nitrites. Experiments on nitrogenous
metabolism. Qualitative examination of Onobrychis sativa for proteids
&G. Comparison of amounts of proteids, peptones, amides in seeds of
Onobrychis and in shoots of the same grown under various conditions.
Comparison of amounts of ammonia, nitrates, nitrites in shoots of
Onobrychis from plants variously treated . . pp. 249 — 260.

CHAPTER XI.

OILS AND FATS. GLYCERINE.

Literature. Extraction of oils and fats. Qualitative examination of
benzene extract. Reactions of glycerin. Quantitative examination.
Determination of total oils and fats — of free fatty acids — of glycerin.
Experiments. Determination of oils and fats in seeds of Lepidium —
in seedlings of Lepidium, young and old . . . pp. 261 — 265.



CHAPTER XII.

TANNINS AND GLUCOSIDES.

Literature, Extraction of tannins and glucosides. Many different
bodies included under heading tannin and glucoside. Qualitative tests
for tannins. Qualitative tests for phloroglucin. Removal of tannins
before examining for sugars. Determination of whether a tannin is a
glucoside or not, Glucosides. Identification of salicin. Examination
for certain sugars. Experiments. Testing extract of willow-bark for
tannin, salicin, sugars. Estimation of certain sugars in young and old
fruits of Musa sapientum pp. 266 — 275.



XVI CONTENTS.

CHAPTER XIII.

DEXTRINS AND SUGARS, GLUCOSES, CANE-SUGAR, MALTOSE, &C.

Literature. Soluble carbohydrates. Qualitative test for fermentable
sugars. Estimation of fermentable sugars. Kemoval of dextrins. Tests
for glucoses, cane-sugar, maltose, mannite, pentoses. Estimation of
glucoses, cane-sugar, maltose. Calculation of results. Experiments on
sugars. Testing leaves of Tropaeolum majus for various sugars. Estima-
tion of fermentable sugars in leaves and roots of Beta vulgaris. Estima-
tion of various sugars in leaves of Beta vulgaris under different conditions.

pp. 276 — 289.

CHAPTER XIV.

STARCH. CELLULOSE.

Literature. Estimation of starch and cellulose. Experiments on
starch. Estimation of starch in the potato by different processes —
in leaves of Acer pseudo-platanus under different conditions. In grains
of wheat before and after germination . . . pp. 290 — 294.



CHAPTER XV.

ORGANIC ACIDS AND SALTS.

Literature of organic acids. Qualitative examination for organic
acids. Determination of 'acidity' of extracts. Literature of inorganic
salts. Preparation of ash of tissues. The constituents of the ash.
Estimation of chlorine — phosphoric acid — alkalies — in ash. Estimation
of calcium oxalate in tissues. Experiments on organic acids. Compari-
son of acidity of juice from old and young rhubarb petioles — of acidity
and amounts of sugars in juice from ripe and unripe apples. Experi-
ments on inorganic salts. Weights of ash from normal and etiolated
leaves. Estimation of phosphoric acid and alkalies in leaves and grains
of barley — of calcium oxalate in young and old leaves of Sempervivum
tectorum pp. 295— 302.



CONTENTS. XVU

CHAPTER XVI.

UNORGANISED FERMENTS. (ENZYMES.)

Literature. Extraction of enzymes. Comparison of activity of
extracts. Experiments on diastatic ferments. Preparation of solid
diastase. Influence of filtration on diastatic power of extracts. Com-
parison of diastatic power of malt and ungerminated barley — of leaves
of Pisum sativum and Trifolium pratense. Experiments on invertase
and glycase. Decomposition of a glucoside (salicin) by an enzyme
(synaptase) from another plant .... pp. 303 — 311.

CHAPTER XYII.

GENERAL EXPERIMENTS.

The increase in weight of growing Spirogyra. The influence of in-
organic salts on the formation of starch. The changes in the reserve
materials of an oily seed during germination under different conditions.

pp. 312—313.

APPENDIX I.

Notes on the results likely to be obtained in experiments on metabo-
lism pp. 314 — 322.



APPENDIX II.

List of reagents and material required for experiments on meta-
bolism pp. 323 — 326.



LIST OF ILLUSTRATIONS.



FIG. PAGE

1 Apparatus for demonstrating respiration .... 2

2 Apparatus for estimating COo produced during respiration . 4
3, 4, 5 Winkler-Hempel apparatus for gas-analysis . . . 7, 8

6 Foil clamp for holding cover-slips together under water, for

use with Velten's hot-stage 18

7 Apparatus for the preparation of water free from CO., hut

not free from oxygen 28

8 Arrangement for the culture of plants in an atmosphere free

from CO., 30

9 Apparatus for gas-analysis for use in experiments on assimi-

lation 42

10 Timiriazeff's eudiometer 46

11, 12 Lemna cultivated in various nutrient solutions . . 64, 65

13 Apparatus for demonstrating root pressure .... 75

14 Another apparatus for the same purpose .... 77

15 The potometer, for estimating the absorption of water by a

cut branch 80

16 A modification of Kohl's apparatus for the same purpose . 88

17 A method of preventing evaporation from the surface of a

flower-pot 97

18 Apparatus for comparing loss by transpiration with the water

absorbed . . • 99

19 A spring-balance for use in transpiration experiments . 101

20 A hygrometer made of the awn of Stipa for performing

Garreau's experiment 103

21 Devaux's gelatine method of making an air-tight junction

with the j)etiole of a leaf 108



LIST OF ILLUSTRATIONS. XIX

FIG. PAGE

22 Apparatus for demonstrating the hygroscopic properties of

the awn of Stipa 114

23 Diagram illustrating the use of turgescent tissue in De Vries'

experiments on isotonic coefficients 126

24 Tracings from split portions of the hypocotyl of Ricinus used

in experiments on isotonic coefficients .... 127

25 Pfeffer's gypsum method 132

26 Arrangement for demonstrating that a turgescent shoot loses

rigidity when bent 139

27 Micrometer-screw used in growth experiments . . . 151

28 Recording auxanometer 154

29 Method of using the auxanometer-lever .... 158

30 Tracing illustrating the effect of an increase of temperature

on growth 160

31 Hanging writer for recording geotropic or other movements

on a revolving drum . . 172

32 Illustrating the curvature of a root which has recovered from

the effects of decapitation 176

33 Curvature of roots produced by small pieces of card attached

to the tips 177

34 Drooping of laurel leaves in a frost 179

35 A twig of Veronica salicifolia exposed to oblique illumination 184

36 The Minostat 186

37 Section showing part of the mechanism of the klinostat . 188

38 A seedling Cucurbita which has germinated on the klinostat ;

showing the frill-like growth of the heel or peg . . 193

39 Diageotropism of the flower of Narcissus poeticus . . 195

40 Leaves of clover in the day and night position . . . 222

41 The sleep-movements of Mimosa recorded on a drum by

means of a hanging writer 223

42 Paraheliotropic movement in Averrhoa bilimbi . . . 225

43 Diagram representing the circumnutation of a cabbage-

seedling 228

44 Leaf of Desmodium gyrans 232

45 Apparatus for distillation under reduced pressure . . 246



ERRATA.

Page 67, note 1,/or " Zimmerman" read " Zimmermann."

„ 70, line 5 from foot, for " developement " read " development."
„ 102, last line, /or "fig. 18" read "fig. 20".
„ 135, note 1, for " 1889 " read " 1888."
„ 136, line 2, for " rasor " read " razor."



PAET I.

GENERAL PHYSIOLOGY.



CHAPTER I.

ON SOME OF THE CONDITIONS AFFECTING THE
LIFE OF PLANTS.

Section A. Respiration. Section B. Temperature —

Poisons — Electricity .

Section A. Respiration.

The presence of free oxygen is a necessary condition of
the life of all the higher plants. This fact will be more
conveniently demonstrated in the chapters on growth and
growth-curvatures. The present section is intended as an
introduction to the study of the facts without special
reference to the importance of respiration.

(1) Production of CO. 2.

Take a stoppered jar of about 500 c.c. capacity, fill it
to one-third of its height with (in spring) horse-chestnut
buds or (in winter) with beans which have been soaked
in water for 12 hours and have been afterwards placed in
damp cocoa-fibre for 12 hours. Place the jar in a warm