INDEX 



489 



Tulip, opening and closing of flowers of, 296. 



pollen of. 293. 

 Tulip Tree, protection of, against dryness, 

 213. 



transpiration of, 204. 

 Tumble weeds. 322. 

 Tourney, on forests, 113. 

 Turgidity, 123, 124, 209, 269. 

 Turnip, storage of food in, 260, 313. 

 Tuttle, acknowledgement to, x. 

 Twinberry. See Partridge-berry. 

 Twining plants, 275, 276. 277. 

 Twisting to increase fruit production, 318, 



319. 

 Type, 420, 434, 450. 

 Typhoid fever, 371, 376, 379, 380. 



Ulex. See Gorse. 

 Ulmus. See Elm. 

 Uredospores, 402.* 

 Urtica See Nettle. 

 Urine, 48. 



U. S. Biological Survey, 356. 

 laboratory for plant-breeding, 441, 

 Dept. of Agriculture, publications of, 113, 

 129, 133, 153, 160, 178, 222, 245, 264, 294. 

 310, 349, 354, 377. 384, 400, 407, 421, 433, 

 434, 441. 



soil surveys of, 351. 



forests of, 356. 

 Ustilago. See Smut. 



Vaccination, 379. 

 Variation, bud, 420. 



cause of, 421, 450. 



curve of. 417, 418,* 419.* 



due to crossing, 422, 424.* 426,* 427*-429,* 

 430, 434. 



environment, 326-360. 



fluctuating, 417. 418,* 419*-421, 442, 443, 

 448.* 449, 450. 



lack of, in vegetative propagation, 433. 



production of, 421. 



sudden, 420. 421. 442,' 443-445,* 446,* 447*- 

 449,* 450-453. • 



suppression of, 433-434. 

 Varnish, absent from water-plants, 339. 



protects against drying, 214, 333, 334. 

 Vegetable matter. See Humus. 



Veins of animals, 176. 



— leaf, 225. 

 Verbascum. See Mullein. 



Vernation as protection against drying, 213. 

 Vicia. See Horse Bean. 

 Vinca, leaf arrangement of, 220,* 221.* 

 Vinegar as preservative, 386. 



manufacture of, 387. 

 Viola. See Violet. 

 Violet, dispersal of seeds of, 321. 



protection of pollen of, 294. 



preferred by bees, 298. 

 Violet rays cut out potassium bichromate 



265. 

 Virginia Creeper attracts insects, 299. 



tendrils of, 274. 

 Vitis. See Grape. 

 deVries, acknowledgement to, x. 409. 



on origin of species, 442-453. 



Waite, on plant diseases, 407. 

 Walnut, cross-pollination of, 302. 



germination of. 59. 



leaf-scar of, 212. 



seed of, path of water in, 23,* 24. 



structure of, 3, 23,* 24,59. 



seed-cover of, escape from, 54. 



— — holds water, 29. 



openings in, 8,* 9. 23,* 29. 



Wandering Jew, 102,* 138. 139. 140.* 



growth of, at nodes, 250. 



root cap of, 86. 



root-hairs of, 102.* 



roots of, 102.* 



stomata of, 196. 



supplies carbon dioxide to aquaria, 285, 

 Ward, on plant diseases, 407. 

 Wasp, power of scent of, 300. 



vision of, 300. 



Water, absorption of, by root, 88, 102, 103, 

 119,* 120*-123.* 332.* 



seeds, 6, 7,* 8,* 9*-15,* 16-19.* 



20,* 21,* 22,* 23.* 26.* 27.* 



wood. 68. 



affected by heat, 332. 



force required for, 121-123.* 124. 



hindered by dissolved salts, etc., 18, 



124. 217. 336, 



seed-covers, 8-26. 



