example, is limited in its southward distribution, chiefly, it ap- 

 pears, by high summer temperatures and low, or excessive, soil 

 moisture. Bermudagrass {Cynodon dactylon) is limited northward by 

 low intensity or insufficient duration of adequate temperatures. 

 The former has a wide range of amplitude at lower temperatures, 

 the latter a wide range at higher temperatures. But Bermuda- 

 grass appears to have a wider range for soil moisture than Ken- 

 tucky bluegrass. 



Table 1-1. Amplitudes of Species to Approximate Concentrations of Mineral Salts 

 IN Marsh, Transition Bog, and Sphagnum Bog in Central Russia. 

 (After N. J. Katz.'^i) 



Marsh, Transition Bog, Sphagnum Bog, 



6 to 10% 5 to 6% 3.5 to 5% 



Pinus silvestris 



Betula alba Scheuchzeria palustris . . 



Alnus glutinosa Carex lasiocarpa Rhynchospora alba 



Carex limnosa 



Carex rostrata Eriophorum vaginatum . 



Menyanthes tnfoliata Ledum palustre 



Calla palustris Cassandra calyculata . . 



Carex vesicana 



Carex diandra Molinia coerulea 



Carex gracilis Calamagrostis lanceolata 



Carex paradoxa 



Carex caespitosa 



Aulocomnium palustre 



Camptothecium nitens Sphagnum subbicolor .... Sphagnum medium . . . . 



Acrocladium cuspidatum Sphagnum balticum . . . 



Drepanocladus vernicosus Sphagnum recurvum 



In rigorous environments the geographic distribution of species 

 is probably indicative of tolerance limits. For example, in Spitz- 

 bergen, species such as Luzula confusa, Oxyria digyna, Polygonum 

 vivipara, Poa alpina vivipara, Salix polaris, and Saxifraga oppositifolia 

 which grow in a variety of habitats differing in altitude and sub- 

 stratum, probably have wide ecological amplitudes, while other 

 species such as Alopecurus alpinus, Calamagrostis neglecta, Carex mis- 



lO • Species and Popmmlatioxms 



