410 



PLANT SOCIOLOGY 



Astragalus, poterium, 273 



tragacanlha, 293, 307 



vesicarius, 114 

 Athamanta, 10 

 Atmometers, black, 104 



clay cup, 139 



coefficient of correction of, 139 



mountings of, 139 



rainproofing valves for, 139 

 Atmosphere, soil, 223 

 Atriplex, 194, 205, 239 



confer lifolia, 193 



halimus, 194 



laciniala, 67 



poly car pa assn., 202 



portulacoides, 192, 197, 230 



verruciferum assn., 202 

 Atropis, 194 

 Autecology, 81 

 Autochthonous pollen, 338 

 Avalanche path, 270 

 Available water, 212 

 AvailabiUty of soil moisture, 216 

 Avena versicolor, 25, 71 

 Avicennia, 201 



officinalis, 193 

 Azolla, 370 

 Azotobacter spp., 235 



B 



Bacillus spp., 243 



Bacteria and soil formation, 242 



as pioneers, 309 



nitrate, 237 



nitrifying, 236 



purple, communities of, 203 



soil, 235, 243 



counting device for, 77 



sulphur, 203 



tubercle, 236 

 Bacterium beijerinckii, 236 



coli, 237 



denitrificans, 241 



fiuorescens, 237 



mesentericus, 242 



mycoides, 237 



radicicola, 236 



stutzeri, 241 



vulgare, 237 



Bad lands, of North Dakota, 116 

 Barbula convoluta initial stage, 14 



gracilis, 68, 376 

 Bark communities, 73, 74, 241 

 Barrel-shaped stems, 29G 

 Bartramia ithyphylla, 308 

 Bases, exchange of, in soils, 1(;3 

 Basidiobolus, 169 

 Basophilous plants, 167, 315 



{See also Calcicoles) 

 Bauxite concretions, 190 

 Beech forest, 37, <19, 50, 68, 99, 105 

 108, 138, 170, 177, 178, 183, 275, 

 301, 317, 348, 369 

 -maple forest, 141, 369 

 -hemlock forest, 109 

 -oak forest, 228 

 Beets, selective absorption of, 179 

 Beggiatoa, 203 

 Begonia spp., 296 

 Bellis, 291 

 perennis, 129 

 silvestris, 50 

 Belt formations of lagoons, 197 

 of lichens, 241 

 transects, 357 

 Berardia subacaulis, 63 

 Betula, 17, 89, 105, 280, 339 

 alba, 105 

 horizon, 348 

 nana, 105 

 verrucosa, 308 

 Biennials, 289 

 Biogeographic regions, 366 

 Biological spectra, 298, 300 

 Biotic factors, 271 

 Birch, 157 

 forest, 108 



(See also Betula) 

 Bird roosts, vegetation of, 241 

 Black alkaU, 204 



Block diagrams, use of, 75, 333, 331 

 Blue-green algae, as pioneers, 309 



communities of, 198 

 Blytt and Sernander's periods, 339 

 Bog mosses, 293 

 Bolbophyllum, 296 

 Boletus, 69 

 Bombaceae, 296 

 Bora, 96 



