Tree group, 282. 
Tropical forest, 355. 
Truffle, 147. 
Tuber, 65; self-burial, 67. 
Tumbleweed, 257. 
Turgor, 104. 
Turpentine, 219. 
Twiner, 47. 
Ulothrix, 105. 
Umbel, 233. 
Umbelliferse, 294. 
Vacuole, 115. 
Variation, 316. 
Vascular bundle, 51. 
Vascular cylinder, 50, 74. 
Vascular system, 76; fern, 188. 
Vaucheria, 111. 
Vegetative multiplication, 101. 
Vegetative propagation, 316. 
Vein, 18, 53. 
Venation, 6. 
Venus fly-trap, 40. 
Vernal habit, 67. 
Viticulture, 298. 
INDEX 365 
Water, absorption by root, 78; 
absorption by seed, 86; plant 
associations, 324. 
Watermelon, 314. 
Water plants, 326. 
Water reservoirs, in plants, 29; 
pollution of, 102. 
Water-root, 80. 
Water-sprout, 70. 
Wheat, 264. 
Wheat rust, 149. 
White pine, timber, 218. 
Wind, plant associations, 326. 
Wings, 291. 
Winter spore, 150. 
Wood, 51; root, 74. 
Wounds, healing, 55. 
Wrack, 118. 
Xerophytes, 326, 337. 
Xylem, 51; root, 74. 
Yeast, 138. 
Yellow pine, timber, 218. 
Yucca, pollination, 244. 
Zygospore, 107. 
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