636 INDEX 



Tussock plants, 284, 285, 336, 361, 413, 



415, 417, 418, 419, 420-41, 491, 546 



Twilight zone (region, see also Dys- 



photic zone), 495-6, 511 

 Twining plants, 87, 88, 89, 431 

 Tychoplankton, 479, 480, 489 

 Types of coniferous forest, 344-50 

 Typha (Cattail, Reedmace), 319, 372, 



461, 505 

 T. angiistifolia (Narrow-leafed Cat- 

 tail), 463 

 Typhoid fever, 26, 279 



Ukraine, meteorological stations in, 575 



Ulex (Gorse), 124, 359 



Ulniiis (Elm), 68, 121, 173, 246, 280, 



306, 340, 341 

 Ulopteryx, 37 

 U/othrix, 30, 31 

 Ultra-violet radiation, 475 

 Ulva (Sea-lettuce), 31, 32, 523 



U. lactuca (Sea-lettuce), 31 

 Umbelliferae, 412, 417 

 Umbrella-shaped trees, 441, 447 

 Under-shrubs, see Ground-shrubs 

 Underground stem, 69 

 Undergrowth of coniferous etc. forests, 



344. 349. 350 

 Undisturbed tracts, aliens rare in, 219- 



21 

 Ungava, Canada, 347, 537 

 Unicellular organisms, 26, 28, 29, 30, 



31-4 

 Uniformity of flora and vegetation in 



early geological ages, 154 

 United States, 251 



, algin production in, 38 



, climatic analogues of, 574, 575, 



576 



Department of Agriculture, 214, 



282, 570, 575 



, endemics of, 205 



, fossil flora of, 150 



, land use and management in, 



556, 567. 570 



, loss from erosion in, 570 



, plants dispersed by ice in, 109 



, Scots Pine planted in, 574 



, soil losses in, 309, 568, 569, 570 



, use of locally-grown seed in, 563 



, vegetation of, 337, 338, 339, 341, 



343, 345. 348-51. 352, 353, 354. 



355. 356, 357. 360-1, 362, 364, 



369, 376-7, 445, 447, 451, 485, 



486, 533, 568, 569 

 Units, chmax, 333, 334 

 Upland Rice, 224 



Upper air, dispersal in, 100, loi, 106 

 — sublittoral zone, 527, 530, 532, 534 

 Upwelling, in ocean water, 513, 519 

 Urals, 338 



Urtica (Stinging Nettle), 554 



U. dioica (Stinging Nettle), 554 

 Usnea barbata, 48 

 Utilization of crops and crop products, 



282 

 Utricularia (Bladderwort), 373, 484, 485 



Vaccinium (Bilberry, Blueberry, 



Whortleberry), 258, 346, 348, 349, 

 358-9, 500-1 

 V. uliginosum subsp. alpinum (Arctic 



Blueberry), 392, 393, 395, 404 

 V. vitis-idaea agg. (Mountain Cran- 

 berry), 392, 393 



Valerian, 264 



Valleys, 389, 542, 543, 545 



— , trees restricted to, 361, 362, 543-4 



Vallisneria (Tape-grass), 503 



Valonia, 274 



Vanilla, 262 



Variation, 25, 562-3 



— , climatic, 284-5, 288-9, 291-3, 294 



■ — , cyclic quantitative, of algal vegeta- 

 tion, 526 



— in salinity of sea-water, 317, 507-8, 

 522-3, 531, 533, 537 



Variety, 25 



Vascular bundles, 54, 70, 71, 73 



— plants, see Vasculares 



— structure, 54, 68, 70, 71 



— system, 54, 505 

 Vasculares (vascular plants), 54-74, 



133-44. 317, 417, 420, 484, 485 



— of the Arctic, 422 

 Vavilov, N. I., 223, 252, 253 

 Vectors, insect, of diseases, 117, 252 

 Vegetable fats, 266 



— fibres, 270-1, 282 



— flower-pot, 432, 433 



— ivory, 269 



— oils, 265, 271 



— sponge, 271 



— tallow, 266 



Vegetables, fruits used as, 231 

 Vegetation, 3, 6, 7, 9, 11, 14, 16, 17, 283 



314, 315, 336-540. 554-6, 565 

 — , antarctic, 415-22, 537-8 

 — , aquatic, factors affecting, 472-9, 



507-15 

 — , arctic, 62, 380-409, 422, 490, 520, 



535, 536, 537 

 — , artificial changes in, 215, 566-71 

 — , cliflF, 372, 550 

 — , conservation of, 309, 569, 573 

 — , cyclic changes in, 330 

 — , desert, 93, 364-8, 449-54 

 — , elements in, 210-12 

 — , erosion checked by, 555, 562, 569, 



570 

 — , freshwater, 479-500, 502-6 



— intertidal, 526-38 



