INDEX 
Plant fibers, 312-314 
Plant geography, 197 
Plant industries, *808-332 
Plant lice, 328, 330 
Plantain, flowers of, 152* 
Plant-breeding rules, 190, 191 
Plasmopara, 239%, 261 
Plastid, 37* 
Pleurococcus, 221, 222%, 223, 249, 260 
Plum, black knot of, 247 
Plums, 187* 
Plumule, 158*, 160*, 162* 
Poison ivy, 73* 
Pollarding, 98* 
Pollen, 15, 128%, 129*, 130%, 134%, 
135* 
Pollen, discharge of, 128*, 129* 
Pollen chamber, 129* 
Pollen grain, germination of, 135%, 
301* 
Pollen sac, 129* 
Pollen tubes, 16, 1385*, 136*, 291* 
800 
Pollen-carrying, 139 
Pollen-carrying apparatus, 146*, 150* 
Pollination, *1384-154, 290 
Pollution of water supply, 229 
Polyporus, 234*, 235*, 261 
Pond lily, 78* 
Pondweed, section of stem of, 85* 
Potato, 87%, 88%, 145* 
Potato blight, 240*-242 
Preservation of fruits, 208, 209 
Pressure of water, 24 
Privet, branching of, 97* 
Propagation by cuttings, 90 
Propagation by roots, 32* 
Propagation by seeds, *161-171 
Proteins, 17, 39, 43, 159, 183, 184 
Protonema, 263*, 266 
Protoplasm, 21, 22 
Protoplast, 21 
Pruning, 317*, 318* 
Pruning due to shade, 77-79 
Pteridophytes, 261, *269-281 
Pteridophytes, classification of, 281 
Pteridophytes, evolution of, 306 
Pteris, 271* 
Ptomaines, 209 
Public health, 212-218 
Puccinia, 255*, 256, 261 
Puffball, 259*, 260 
Pulvinus, 77 
Quercus, 194, 195*, 196 
365 
Radial symmetry, 129 
Raspberry, 89*, 157*, 171* 
Receptacle, 126% 
Red alge, 232*, 233, 261 
Red clover, leaf of, 77* 
Redwood, 204 
Reindeer moss, 251 
Reproduction, sexual, in flowering 
plants, *134-137, *289-292, *299- 
303 
Reproduction, of bacteria, 201-203 
Reproduction, by portions of stem, 
*87-92 
Reserve food in seeds, 158, 159, 165 
Resin duct, 285* 
Respiration, 46, 47 
Resting buds, 94 
Rest period in seeds, 162 
Rhizoids, 236 
Rhizome. See Rootstock 
Rhizopus, 260 
Rhodophycez, 260 
Ring, annual, 12*, 66 
Rise of water in stems, 42, 43 
Rockweed, 231* 
Roguing, 177 
Root, 8*, 9, 10*, 11* 
Root, fleshy, 45* 
Root, section of, 11*, 20* 
Root absorption, 9 
Root climbers, 73*, 74 
Root hairs, 9, 10*, 11*, 21* 
Root system, 25 
Root tubercles, *203-207 
Rooteap, 20 
Roots, aérial, 30*, 31 
Roots, air requirements of, 26*-28 
Roots, anchorage by, 8*, 9 
Roots, earth, 25-29 
Roots, effects of, on soil, 26, 27 
Roots, parasitic, 31 
Roots, pull of, 25, 26 
Roots, reproduction by, 32*~ 
Roots, storage of food and water in, 
45* 
Roots, structure of, 20*, 21* 
Roots, water, 29*-31 
Roots, water-lifting by, 24 
Rootstock, 86*, 87, 271, 272* 
Root-tubercle bacteria #205-207 
Roquefort cheese, 245 
Rose, leaf bud of, 94* 
Rosette plants, 72*, 78 
Runners, 90 
Run-off, 119, 120 
