362 INDEX 
Peronospora, 142. 
Petal, 221, 222. 
Petiole, 6. 
Pheophycex, 116. 
Phloem, 52; root, 74. 
Photosynthesis, 18, 87. 
Phototropism, 92. 
Phycomycetes, 144. 
Pileus, 155. 
Pine, timber, 218. 
Pineapple, 281. 
Pirus, 2X9. 
Pistil, 228. 
Pitcher-plant, 35. 
Pith, 50; ray, 51. 
Plains, 341. 
Plant associations, 324; cactus 
desert, 341; deciduous forest, 
350; mangrove swamp, 336; 
meadow, 345; mesophytic thick- 
et, 348; peat-bog, 336; plain, 
341; pondweed, 328;  reed- 
swamp, 331; rock, 338; salt and 
alkaline desert, 344; salt marsh 
and meadow, 336; salt steppe, 
344; sand, 338; subtropical 
desert, 341; swamp, 331; swamp 
forest, 336; swamp thicket, 332; 
tropical forest, 355; xerophytic 
forest, 344; xerophytic thicket, 
344. 
Plant-breeding, 316. 
Plasmolysis, 115. 
Plastid, 104. 
Pleurococcus, 102. 
Plum, 289. 
Plumule, 86; escape of, 91. 
Pod, 238. 
Pollarding, 70. 
Pollen, 242; Angiosperm, 224; 
conifer, 212. 
Pollen-sac, 226; conifer, 212. 
Pollen-tube, Angiosperm, 
conifer, 217. 
Pollination, Angiosperm, 
conifer, 217. 
Pollinium, 24s. 
Pome, 289. 
Pomelo, 299. 
Pomology, 289. 
Pond-seum, 113. 
Pondweed association, 328. 
Pore Fungi, 156. 
Potato, 305. 
Prairie, 345. 
Profile leaves, 29. 
Pronuba and Yueea, 244. 
Prop-root, 80. 
Protection, leaves, 24. 
Proteid, SS. 
Prothallium, 193. 
Prothallus, 193. 
Protoplasm, 87, 103. 
Prune, 289. 
Prunus, 288. 
Pteridophytes, 183, 207, 208. 
Puffball, 158. 
Pumpkin, 315. 
Pyrenoid, 114. 
Quince, 291. 
Quinine, 309. 
Raceme, 282. 
Rain, leaves, 32. 
Xanunculacez, 2S4. 
Raspberry, 27. 
Ray, 310. 
Reaction, 93. 
Receptacle, 240. 
Red Algze, 124. 
Redwood, 219. 
Reed swamp, 331. 
Reforestation, 323. 
236; 
249; 
