INDEX 



433 



Serpentine plants, 188, 190 

 soil, 188 



profile of, 189 

 Seseli varium, 114 

 Sesleria, 291, 321 



coerulea, 17, 215, 311, 319, 321 



var. calcarea, 70 

 disticha, 25, 72, 308 

 Seslerietalia, 371 

 Seslerieto-Semperviretum, 18, 28, 63, 



121, 250, 317, 319, 321 

 Seslerion coeruleae, 155 

 Settlement, definition of, 25 

 Shade plants, 107 



{See also Sciophytes) 

 Short-day plants, 102 

 Showers, effects of heavy, 115 

 Shrub communities, 372 



seres, 336 

 Sibbaldia procumbens, 61, 68 

 Sibljak, 336 



Sieversia montana, 120, 365 

 reptans, 310 

 turbinata, 156 

 Silene acaulis, 37, 71, 148, 293 

 alpina, 44 

 otites, 62 

 rupestris, 190 

 vulgaris, 191 

 Silicicolous plants, 187 

 Silybeto-Urticetum, 374 

 Silybum-Urtica pilulifera assn., 240 

 Slope of soil, 268 

 Smilax aspera, 130 

 Snow, abrasive action of, 118 

 avoiding communities, 121 

 beneficial effects of, 118 

 cover, 119 



and plant communities, 120, 121, 



122, 124, 345 

 and slope, 269 

 duration of, 121, 124, 261 

 wind and, 149 

 effects of, 118, 123 

 melting, 90 



and exposure, 263 

 -pockets, 124 

 -pocket associations, 29, 122, 123 



plants, 99, 123, 124 

 species favored by, 119 



Snowland communities, 12, 121, 124 

 Snowless vegetation period, in the 



Alps, 261 

 Sociability, 14, 34, 35, 36, 320 



determination of, 37 

 Social development, presentation of, 332 

 specialization, characteristic species. 



66 

 units, mapping of, 357 

 Sociologic independence of communi- 

 ties, 370 

 Sociological classification, 2, 354 

 mixtures, 61 

 progression, 334, 367 

 Sociology, plant, 1 

 Soda, determination of, 205 

 plants, 205 

 soils, 204 



osmotic pressure of, 205 

 vegetation of, 205 

 Sodium chloride content of Mediterra- 

 nean, 195 

 of soil, 196, 200 

 ionic effects of, 194 

 soil, 204 



soils, vegetation of, 195, 198 

 Soil acidity, 165 



and succession, 17 

 measurement of, 168 

 air capacity of, 214, 227, 229 

 algae, communities of, 371 

 anastatic and eustatic, 175 

 atmosphere, 223, 224, 226, 230 

 bacteria, 77, 235, 243 

 buffering of, 174 

 carbonic acid content of, 225 

 chemistry and plant communities, 161 

 climax, 255 



color and soil temperature, 220 

 constancy of plants, 182 

 crumbing, 211 

 development, 255 

 and pH values, 314 

 serpentine, 189 

 dispersion and vegetation, 209 

 elutriation of, 208 

 factors, 159 

 fauna, 233 

 flocculation of, 208 

 flora, 234 



