Illegitimate unions, 265. Immunity, 155, 156, 165, 168, 169. Impervious subsoil, 181. Inarching, 269. Increase in dry weight, 23. Indian agriculture, 172. Indian wheats, 168. Indispensability of elements, 278. Infection, 262, 265, 267. Ingredients of protoplasm, 272. Insect bites, 225. Insect diseases, 145, 146, 154, 189. Insect punctures, 88. Insects, 89, 98, 108, 109, 120, 138, 142, 153, 174, 187, 194, 203, 205, 206, 207, 208, 212, 223, 229, 241, 244, 248, 251, 254, 255, 258, 259, 269. Insolation, 180, 242. Intercellular endophytes, 136, 137. Intercellular mycelium, 128. Interference, 91. Internal causes of disease, 99, 101. Intracellular parasites, 127, 136. Intramolecular respiration, 277. Intumescences, 212, 215. Inulin, 11, 17. Invertebrata, 108. Irritability, 125, 127. Irritation, 119, 139. _Isaria_, 163. Ivy, 113, 165. Japanese trees, 250. Jerusalem Artichoke, 264. _Juncus_, 219. Juniper, 114. Kidney bean, 192. Knauers, 223. Knife wounds, 194, 195. Labour, 161. Lace-wings, 165. _Lachnus_, 223. Lady-birds, 164, 165. Lammas shoots, 257, 259. Larch, 168, 171. Larch disease, 115, 149, 152, 166, 171, 223, 241. Larvae, 110. Lateral wounds, 132. Lawns, 112. Laying of wheat, 179, 180. Leaf-curl, 236, 253. Leaf-diseases, 114, 119, 120, 242. Leaf-galls, 217, 218. Leaf-miner, 86, 109, 204. Leaf perforations, 208. Leaf rolling, 214, 246, 254. Leaf-spots, 114, 190. Leguminoseae, 137, 219. Lemons, 235. Lenticels, 217. Lepidoptera, 187. _Leptosphaeria_, 249. Lichens, 137. Liebig, 4. Life, 271, 285, 287. Life and death, 271. Light, 27, 106. Lily disease, 143. Lime, 163, 215, 218, 232, 253, 254, 260, 269. Limes, 172. Limits of variation, 287. _Linaria_, 252. Liquid antiseptics, 160, 161, 162. Living environment, 99, 108. Local action, 114. Local disease, 119, 121. Locusts, 109, 145, 163, 164. Longicorns, 205. _Loranthus_, 113, 245, 265. Losses due to epidemics, 142. Lowering of temperature, 100. Lucerne, 249. Lurking parasites, 142, 145. Lychnis, 232. _Lyonetra_, 206. _Lysimachia_, 217. Machine, plant compared to a, 79. Magnesium, 272. Maize, 116, 173, 219, 267. _Majanthemum_, 175. Malformations, 116, 130, 131, 246, 251. _Mal nero_, 190. Mallow, 252. Malpighi, 85. Mammals, 142. Man and plants, 108, 142, 143. Manna, 227, 235. Manna Ash, 235. Maple, 259. Maximum, 288. Maximum absorption, 19. Maximum assimilation, 19. Maximum temperature, 105. Mealy bug, 164. _Melampsora_, 176. Melon, 220. Messmates, 63. Metabolic products, 274. Metabolism, 23, 127, 271. Metabolites, 278. Metallic compounds, 162. Mice, 108, 163. Microbes, 227. Micro-organisms, 183. Mildew, 86, 164. Millardet, 169. Mineral salts, 101.