Seed-plant. See "Spermaphyte." _Selaginella_, _-eæ_. See "Smaller club-moss." Sensitive-brier, 209; Fig. 115. Sensitive-plant, 209. Sepal, 148, 150, 174, 179. _Sequoia_. See "Red-wood." Sessile leaf, 170. _Shepherdia_, 206. Shepherd's-purse, 173-180; Figs. 93-95. gross anatomy of stem, 173. leaf, 124, 173. root, 173. branches, 174. flower, 174, 175. fruit and seed, 175. histology of root, 175, 176. stem, 177. leaf, 177, 178. development of flower, 179. ovule, 179. embryo, 180. Shooting-star, 212; Fig. 117. Sieve-tube, 111, 137. _Silene_. See "Catch-fly." Silicon, 2. Simple leaf, 170. _Siphoneæ_, 22, 34. _Sisyrinchium_. See "Blue-eyed grass." Skunk cabbage, 157. Slime mould, 12, 14; Fig. 5. plasmodium, 12. movements, 13. feeding, 13. spore-cases, 13. spores, 13. germination of spores, 14. Smart-weed. See "_Polygonum_." _Smilaceæ_, 155. Smoke-tree, 198. Smut, 64, 65. Smut-corn. See "_Ustillago_." Snowberry, 223. Soft-tissue, 112. _Solanum_, _-eæ_, 215. Solomon's Seal, 154; Fig. 83. Soredium, 74. Sorus, 118. _Spadicifloræ_, 153, 157. Spadix, 157. Spanish bayonet. See "_Yucca_." _Sparganium_. See "Bur-reed." Speedwell. See "_Veronica_." Spermaphyte, 128-129. Spermatozoid, 28, 36, 40, 46, 51, 89, 96, 106, 122. Spermagonium, 79, 80. _Sphagnum_, _-aceæ_, 99, 100. sporogonium, 100. leaf, 100. Spice-bush, 188. Spiderwort, 6, 151, 157; Fig. 85. _Spigelia_. See "Pink-root." Spike, 181. Spikenard, 202; Fig. 110. Spinach, 184. Spindle-tree, 199; Fig. 109. _Spirogyra_, 30-32; Fig. 18. structure of cells, 30. starch, 31. cell-division, 31. sexual reproduction, 32. Sporangium, 55, 62, 113, 121, 122, 131, 148, 151, 179. Spore-case. See "Sporangium." Spore-fruit, 51, 66, 69, 70, 73, 83. Spore-sac. See "Ascus." Sporocarp. See "Spore-fruit." Sporogonium, 87, 90, 102, 123. Sporophyll, 128, 131, 148. Sporophyte, 109. Spring-beauty, 185; Fig. 98. Spruce, 142. Spurge. See "_Euphorbia_." Squash, 221. Staining agents, 4, 231, 233. Stamen, 128, 143, 148, 174, 179. Standard, 207. _Staphylea_. See "Bladder-nut." Starch, 31, 95, 152. _Statice_. See "Sea-rosemary." _Stellaria_. See "Chick-weed." _Stemonitis_, 13; Fig. 5. _Sticta_, 75; Fig. 45. _Stigeoclonium_, 26; Fig. 14. Stigma, 145, 148, 175, 179. St. John's-wort, 195; Fig. 105. Stock, 192. Stoma. See "Breathing-pore." Stonecrop, 202; Fig. 113. Stone-fruit, 206. Stone-wort. See "_Characeæ_." Stony-tissue, 110. Stramonium, 215. Strawberry, 171, 202, 206; Fig. 113. Style, 148, 175, 179. _Stylophorum_, 187; Fig. 103. Sugar, 8, 145. Sulphur, 2. Sumach, 198; Fig. 108. Sun-dew, 192, 193; Fig. 104. Sunflower, 224. Suspensor, 180. Sweet-flag, 157. Sweet-potato, 214. Sweet-scented shrub. See "_Calycanthus_." Sweet-william, 185. Sycamore, 183. _Sympetalæ_, 210. _Symphoricarpus_. See "Snowberry." _Symplocarpus_. See "Skunk-cabbage." Synergidæ, 144.