434 



PLANT SOCIOLOGY 



Soil formation, 242 



and development of vegetation, 



310, 312 

 climatic factors in, 255 

 in alpine regions, 312 

 in arid climates, 311 

 fungi, 77 



granulation, 207, 211 

 horizon, acidification of uppermost, 



171 

 horizons, 45, 164, 173, 189 

 map, Europe, 259 



U. S., 260 

 moisture and exposure, 266 

 availability of, 216 

 coefficient of, 214 

 nitrogen content of, 145 

 of swamps, 256 

 organisms and vegetation, 232 

 oxygen content of, 224 

 particles, size of, 207, 210, 211 

 permeability, 232 

 profiles, 164, 173, 189, 254 



pH changes in, 174 

 putrefaction in, 243 

 reaction, 171 



samples, for pH determinations, 168 

 slope of, 268 



solution, concentration of, 164, 202 

 structure, 231 



(See also Soil profiles; Soil crumb- 

 ing; etc.) 

 surface temperature, 265 

 system, 161 



temperature, 218, 221, 222, 223 

 and exposure, 265 

 and growth, 219 

 annual cycle of, 221 

 in deserts, 222 

 maximal, 221 

 measurement of, 223 

 with increasing altitude, 219 

 theory, chemical, 159 



physical, 160 

 types, 254 

 and pH, 178 

 classification of, 255 

 climatic, 258 

 water, 211, 229, 230 

 capacity of, 213 



Soils, classification of, 256 

 degree of division of, 208 

 mechanical analyses of, 208 

 rich in zinc, 197 

 Solarium tuberosum, 37, 186 

 Solar energy, 83, 84 

 Soldanella alpina, 120, 122 

 carpatica, 123 

 minimal, 123 

 pusilla, 120, 123, 261 

 Solenetz, 256 



Solfataras, plant communities of, 203 

 Solidago, 16 



missouriensis, 328 

 virga aurea, 69 

 Solifluction, 269 



Solontschak association of arid steppes, 

 202 

 soils, succulents, 201 

 Sorbus-Betula horizon, 348 

 Sorghastrum avenaceum, 328 

 Spacial factor in classification, 366 

 Spacing, determination of, 30 

 SpaUerstraucher, 294 

 Spartium junceum, 190 

 Spartina, 194, 308 

 stricta, 16 

 townsendi, 16 

 Species: area curves, 40, 54, 55 

 Linnaean, 21 

 of plants, 21 

 Specific acidity, 167 



alkaUnity, 167 

 Spectra, biological, 298, 300 

 Spectrum, of sunlight, 83 



phytochromatic, 107, 108 

 Spergula arvensis, 373 

 Sphaerella nivalis, 289 

 Sphaeroporus globosus, 38 

 Sphagnetalia, 372 

 Sphagnetum, 127, 136 

 Sphagnum, 76, 127, 182, 251, 293 

 fuscum, 253, 352 

 moor, 127, 253 

 peat, 251 

 peat layer, 327 

 Sphenopus, 194 



gouani, 230 

 Spiraea tomentosa, 333, 334 



