376 
Plant society, 113. 
Plants, classes of, in relation to 
economy of water, 115-118*. 
Plants, destruction of, by animals, 
122. 
Plants of uneatable texture, 123. 
Pleodorina, #298. 
Pleurococcus, 212. 
Plum hybrids, *319. 
Plumule, *5, *14. 
Pod, 183, 187, *194. 
Poisonous plants, 125, 126. 
Poisonous seeds, 21. 
Poisons, plants containing, 125, 126. 
Pollarded trees, 95. 
Pollen, 162—169*. 
Pollen, discharge of, *162. 
Pollen grain, germination of, *165. 
Pollen grains, *163. 
Pollen grains, number of, per ovule, 
167. 
Pollen, protection of, from visitors, 
1738. 
Pollen tubes, 163, 164, #165, 
Pollen-carrying apparatus, 
*170. 
Pollination, 168~180*. 
Polypetalous, 153. 
Polysepalous, 153. 
Pome, 188. 
Poplar, leafy twig of, *97. 
Poplar twig, 51. 
Potato tuber, 59, *60, 83, 84, 332, 
333. 
Prickle, *123, *124. 
Prickly leaves, #124. 
Primary root, *14, 30. 
Primrose, pollination in flowers of, 
*178. 
Procambium, *71. 
169, 
ESSENTIALS OF BOTANY 
Propagation, by root, 42. 
Protection of plants from animals, 
122-126*, 
Proteids, 19, 20. 
Proteids, tests for, 20. 
Prothallium, *283, *284, *290. 
Protonema, *274. 
Protoplasm, *43, 44, 45. 
Protoplasm, characteristics of, 44, 
45, ; 
Psalliota, type study, 259-261*, 
Pteridophytes, 280-294*, 
Pteridophytes, remarks on, 293, 294. 
Puccinia, type study, 255-258. 
Raceme, App. I, *357. 
Raspberry, *189. 
Ray, medullary, *70, *71, *72, *738, 
74. 
Ray-flowers, App. I, *359. 
Receptacle, 150, *156. 
Red alge, 234-237%, 
Red clover, leaf of, #109. 
Regular flowers, 149. 
Reproduction in seed plants, 165- 
167*, 
Respiration, 136, 140, 141. 
Retuse, App. I, *356. 
Rhachis, 282. 
Rhizoids, hairs serving as roots * 
in ferns, mosses, and liverworts, 
¥*265, *273. 
Rhizopus, type study, 246-248, 
Ring, annual, *78. 
Ringent, ¥*152. 
Rise ot water in stems, 78-80. 
Rockweed, type study, 230-233*. 
Root, 30-42*, 
Root, adaptation to work, 41, 42. 
Root, dicotyledonous. section, *37. 
