532 



Index 



Sere, 431 



Serpentine, toleration by plants, 285 

 Sessile existence, 44-45, 310 

 Sex ratio, influence of crowding on, 

 325 



influence of temperature on, 158 

 Sheep, 315, 384, 491, 502 

 Shells, formation of, 273-276 

 Short-day plants, 224 

 Sinking rate of marine organisms, 36- 



42 

 Size, of organisms, in relation to 

 medium, 32-34 

 in food chain, 470 

 Slave-making ants, 385 

 Snails, 104, 121, 312 

 Social dominance, 328 

 Societies of animals, 331-.332 

 Sodium, recjuirements of plants for, 



282 

 Soil, action on plants, 73-76 



calcium carbonate in, 271 



chemical composition, 72-73 



community, 420-421 



decomposition in, 301 



effects of organisms on, 76 



erosion, 11 



formation, 77-79 



moisture in, 111-112 



nutrients in, 284-286 



organisms in, 76-77, 472 



oxygen in, 244 



particles, 74 



pH, 269-270 



profile, 80-84 



regeneration of nutrients in, 304-305 



saline, 97 



temperature, 130-131 



texture and structure of, 73-74 



water, 112 

 Soil-group divisions, 84—89 

 Solar constant, 186 

 Solifluction, effect on tree line, 174 

 Soybean plant, 366 

 Spanish moss, 375-376 

 Spawning of marine organisms in lunar 



cycle, 220-221 

 Species composition, latitudinal differ- 

 ences, 487-489 



of communities, 414-424 



variation in microclimates, 123 



Species flocks, 417 

 Species/genus ratio, 417-418 

 Spectral distribution of radiant energy, 



134-135, 192-194 

 Springs, 132 



thermal, 130 

 Spruce forest, 431 



community, 408 

 Stagnation, in cycles, 303 



in lakes, 138 

 Standing crop, 482-489, 494-496 



equihbrium level of, 485-487 



in relation to population growth, 

 483-485 



regional differences in, 487-489 

 Starling, dispersal of, 428 

 Stenohaline organisms, 97-98 

 Stereotropism, 61 

 Strangling fig, 383 

 Stratification, in communities, 420-424 



in lakes, 138 



in ocean, 136 

 Streams, 42, 48, 52 



adaptations to current, 57 

 Substratum, aquatic, 66-71 



attainment of, 60-61 



breakdown of, 69 



build-up of, 69-71 



reactions to, 61-62 



terrestrial, 71-89 



types of, 62-66 

 Succession, 425-446 



arrested, 431 



convergence in, 438-439 



in old fields, 435^38 



in ponds, 432-435 



in tidal zone, 442-444 



modification of, 444-446 



on fallen logs, 440 



primary, 432-435 



secondary, 435—438 

 Sugar cane, 227, 502 

 Sulphur, 280 

 Sundew, 393 

 Simfisli, 203, 321 

 Sunspot cycle, 463-464 

 Support by medium, 32-42 

 Supralittoral zone, 30 

 Surface film of water, as a substratum, 



62-63 

 Swallows, tree, 228 



I 

 ( 



