CONTENTS xi 



Differences in potential between illuminated, and non-illuminated portions of a stem 



— 160. Effect of electric current upon streaming movement of protoplasm — 161. 

 Influence of induced current upon Mimosa — 162. Influence of currents of electricity 

 upon growth; direct current — 163. Effects of continuous stimulation — 164. Effects 

 of alternating secondary currents — 165. Influence of static electricity — 166. Elec- 

 trotropism — 1 67. Electrotaxis. 



VIII. Relations of Plants to Light 110-146. 



168. Nature and derivation of light — 169. Trophic relations of light — 170. Tonicity 

 to light — 171. Direct chemical influence of light upon protoplasm — 172. Critical 

 points in the chemical action of light — 173. So-called rigor of darkness — 174. Etiola- 

 tion — 175. Etiolated seedlings — 176. Etiolation of plants with, and without aerial 

 stems — 177. Etiolation leaves with parallel veins — 178. Etiolation of sessile leaves — 

 176. Etiolation of climbing and trailing plants — 180. Formation and maintenance of 

 chlorophyl — 181. Formation of chlorophyl in darkness — -182. Growth of green 

 plants in darkness — 183. Formation of chlorophyl in a blanched specimen — 184. 

 Microchemical test for the presence of chlorophyl — 185. Absorption of light by 

 tissues of plants — 186. Purposes and uses of chlorophyl — 187. Critical points in the 

 photosynthetic relations of light to plants — 188. Fluorescence of chlorophyl solutions 



— i8g. Absorption spectrum of chlorophyl — igo. Action of light on chlorophyl 

 solutions — igt. Red and other coloring matters in leaves — 192. Relation of antho- 

 cyan to light — 193. Arrangements for concentrating rays on chlorophyl — ig4. Stimu- 

 lating influence of light — • igs. Perceptive zones in phototropism — ig6. Localiza- 

 tion of the sensory zone — ig7. Transmission of stimulus-effects — 198. Transmission 

 in stems — igg. Rays inducing phototropic reactions — 200. Color filters — 201. Re- 

 action time — 202. Critical points in the phototropic relations of light to plants — 203. 

 Intensity of illumination necessary to constitute a stimulus — 204. Negative reaction 

 to light above the maximum — 205. Summation of stimuli — 206. Threshold of stimu- 

 lation — 207. Zone of curvature — 208. Aphototropism — 2og. Diaphototropism — 

 210. Paraphototropism of leaves of Taraxacum — 211. Diaphototropism of leaves 

 ofArisaema — 212. Compass plants — 213. Other reactions due to intensity of illu- 

 mination — 214. Paraphototropism — 215. Nyctitropic movements — 216. Formative 

 influence of light — 217. Production of primordial leaf-forms in diffuse light — 218. 

 Influence of light on the formation of tubers. 



IX. Composition of the Body 147-174. 



2ig. Substances found in plants — 220. Carbohydrates — 221. Fractional extrac- 

 tions — 222. Estimation of tannins and glucosides — 223. Determination of sugars 

 and dextrins — 224. Starch — 225. Cellulose — 226. Proteids — 227. Extraction of 

 proteids — 228. Separation of proteids — 22g. General qualitative test for proteids — 

 230. Tests for albumin — 231. Treatment of proteoses — 232. Tests for peptone — 

 -233. Determination of ^proteid soluble in alcohol — 234. Proteids soluble in dilute 

 acid and alkali — 235. The fats — 236. The extraction of fats — 237. Qualitative 

 tests for fats — 238. Determination of organic and inorganic matter — 23g. Inorganic 

 constituents — 240. Qualitative determination of mineral constituents — 241. En- 

 zymes — 242. Determination of enzymes. 



X. Exchanges and Movements of Fluids 175-216. 



243. Physical constituents of protoplasm — 244. Imbibition — 245. Increase in 

 walls by imbibition — 246. Energy of imbibition — 247. Movements caused by imbi- 

 bition — 248. Osmose in cells — 249. PWsmolysis — 250. Permeability of plasmatic 

 membranes to coloring matter — 251. Osmose: change in osmotic qualities of mem- 

 branes affecting permeability — 252. Turgidity — 253. Estimation of the force of 



