Resistance to disease, 155, 268. Resistant races, 172. Respiration, 17, 31, 130, 271, 275, 276, 285, 287. Reversions, 73. Rhinanthoideae, 265. _Rhinanthus_, 112. _Rhizobium_, 289. _Rhizoctonia_, 238. Rhizomorph, 145. Rhododendron, 218. Rhubarb, 180, 230. _Rhynchitis_, 254. _Rhytisma_, 188. Ribbon grass, 183. _Ribes_, 214. Rice, 172. Rimpau's experiments, 69, 73, 77. Ringing, 194, 201, 202, 210. Ripened wood, 243. _Robinia_, 259. Rodents, 109. _Roestelia_, 217. Rolled leaves, 86. Root, 9, 35, 96, 120, 227, 270. Root-absorption, 181. Root-diseases, 119, 120. Root-excretions, 46. Root-fusions, 262. Root-galls, 221. Root-hairs, 34, 102, 163. Root-nodules, 212, 219. Root-parasites, 112, 265. Root-rot, 230. Roses, 232, 243, 257, 268, 278. Rosettes, 225. Rot, 97, 182, 227, 229, 231, 236. Rotation of crops, 69, 166. Rotifer, 140. Rot-organisms, 200. Rotting of wounds, 87. Rouen law, 85. Rushes, 114. Rust, 122, 142, 171, 172, 175, 191. Rye, 176, 248. _Saccharomyces_, 60. Sachs, 7, 36. _Salvia_, 214. San José scale, 187. Sand-blast action, 184. Sandy soils, 184. _Saperda_, 205. Saprophytes, 135, 137, 175, 234, 243, 244. _Scab_, 189, 216. _Scale_, 187. _Schinzia_, 114. _Schizoneura_, 223. Scion, 183, 262, 264, 266, 282. _Scleroderris_, 223. Sclerotia, 143. Schwarz, 39. _Sclerotinia_, 142, 143, 144, 231, 248, 249, 288. Scolytidae, 205. Scorching, 240, 241. Scurf, 216. Sea-kale, 261. _Secale_, 76. Secretions, 130, 133, 173, 274. Sedges, 189. Seedless grapes, 247. _Selandria_, 208. Selection, 69, 74, 78, 169. Selective absorption, 53, 65. Self-fertilisation, 281. Semi-parasites, 112. _Senecio_, 188. Sensitive plant, 125. _Septoria_, 114, 187. Sewage waters, 59. Sexual act, 72. Shaded foliage, 113. Shanking, 246, 249. Shoots from old wood, 260. Shot holes, 204, 208, 209. Silver fir, 224. Silver leaf, 192. _Sirex_, 206. Skeleton leaves, 204, 207. Slime flux, 227, 233. Slime fungus, 219. Slugs, 111, 164, 207, 269. Smut, 117, 143, 162, 190. Snails, 111, 142, 207. Snow, 106. Soap, as insecticide, 161. Soil, 1, 42, 99, 102, 142, 163. Soil-bacteria, 60. Soil-filtration, 59. Soil-organisms, 61, 143. Solar energy, 135. Somato-plasm, 267. Sooty moulds, 135, 190, 232. _Sorbus_, 207. _Sorosporium_, 216. Sour-rot, 231. Sparrows, 164. Specialised races, 168, 176. Specific predisposition, 155. Spectrum, 19, 21, 26. Spermogonia, 144, 232. _Sphaerella_, 189. _Sphaerotheca_, 187. Sphaeroblasts, 222, 225. _Spicaria_, 237. Spiral grooving, 204, 210. Spiral growth, 252. _Spongospora_, 216. Spontaneous variations, 78, 246, 255. Spores, 144. Sports, 93, 247. Spots on leaves, 120, 186. Spraying, 159, 161, 162.