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 

 189. Absorption spectrum of chlorophyl 190. Action of light on chlorophyl 

 solutions 191. Red and other coloring matters in leaves 192. Relation of antho- 

 cyan to light 193. Arrangements for concentrating rays on chlorophyl 194. Stimu- 

 lating influence of light 195. Perceptive zones in phototropism 196. Localiza- 

 tion of the sensory zone 197. Transmission of stimulus-effects 198. Transmission 

 in stems 199. 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. Aphototropistn 209. Diaphototropism 

 210. Paraphototropism of leaves of Taraxacun 211. Diaphototropism of leaves 

 of Arisaema 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. 



219. 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 229. 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 239. 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. Plasmolysis 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 



