580 
Perennial stems, 171. 
Perfect. flower, 18, 11* 
Perianth, 11, 460, 11*, 460*. 
Pericarp, 61, 66%. 
Pericentral cell,. 328. 
Pericycele, 147. 
Peridium, 390. 
Perigynous flower, 16, 15*. 
Perisperm, 46. 
Perisporiales, 364; described, 373- 
375. 
Peristome, 421. 
Perithecium, 369, 370*. 
Permanent root, 103. 
Peronosporales, 353; described, 355- 
360. 
Petal, 12, 11*. 
Petiole, 234. 
Peziza, 366, 367*. 
Pezizales, 364; described, 366-369. 
Phaeophyceae, 318-324. 
Phallus impudicus, 391, 392*. 
Phellogen, 185*. 
Phenotype, 554. 
Phloem, 130, 146, 188. 
Phosphorus, as a soil constituent, 157. 
Photosynthesis, 169; described, 252- 
260; factors influencing, 257. 
Phycocyanin, 297, 324. 
Phycoerythrin, 324. 
Phycomycetes, 352; described, 353- 
363. 
Phylogenetic divisions, 292. 
Phylogeny, 291. 
Phylloglossum, 438. 
Physical basis of heredity, 535. 
Phytophthora cactorum, 358, 361*. 
Phytophthora infestans, 357, 358*, 
359*, 360*. 
Pigments, 281; described, 283. 
Pileus, 386, 386*. 
Pilobolus, 362. 
Pineapple type of fruit, 80, 80*. 
Pine Blister-Rust, 402. 
Pines (Pinaceae), 451-458; gameto- 
phytes, 455-457; life cycle, 457*; 
seed, 457; sporvphyte, 452, 451°; 
strobili, 452-455, 
INDEX 
Pink, family, 480; flower, 481, 15*, 
481* 
Pistil, 11, 11*; compound, 15; de- 
scribed, 14, 462; simple, 15; 
structure, 33-37. 
Pistillate flower, 14, 12*; of Corn, 18, 
19*. 
Pitcher Plant, 132, 272*. 
Pith, 187, 187*. 
Pitted vessels, 188, 190*. 
Placenta, 77, 34*. 
Plagiotropism, 173. 
Plant Breeding, 557-565. 
Plant Ecology, 2. 
Plant food, nature, 120. 
Plant Geography, 3. 
Plant Pathology, 2. 
Plant Physiology, 2. 
Plant succession, 510-512. 
Plasmopara Viticola, 355, 355*, 356*, 
357* . 
Plastids, 115, 251. 
Plectascales, 364; described, 375-377. 
Pleurococcus vulgaris, 294, 307, 294%, 
307*. 
Plowrightia morbosa, 369, 370*. 
Plum type of fruit, 78, 77*. 
Plumule, 56, 466, 56", 466* 
Podophyllum, 180, 180* 
Poisonous Toadstool, 384*. 
Pollen, 41, 41*, 42*; function, !2; in 
relation to external factors, 49; 
structure, 41, 42*. 
Pollen chamber, 448, 449*. 
Pollination, 46; agents, 46; kinds, 47; 
kinds giving best results, 52; 
nature, 46; results, 50; scl, 
close-, and cross-, 48. 
Polyadelphous flowers, 15. 
Polycotyledons, 67. 
Polyembryony, 467. 
Polygonaceae, 478-480. 
Polygonum Muhlenbergti, 227, 479*. 
Polypetalac, 481-489. 
Polypetalous flowers, 13. 
Polyporaceae, 387. 
Polysiphonia, 327, 328*. 
Polysiphonia violacca, 328*. 
