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VESTAL— PIIYTOGEOGRAPHY OF COLORADO 



187 



Lichen association.— Lichens, especially Rinodina, Lecanora, 

 and Parmelia cons per sa, partly cover the dry rock surfaces, espe- 

 cially granites in the foothills and the craggy outcrops and loose 

 surface rocks of the mountain-front: Rock exposures are infre- 

 quent in the plains proper. 



TABLE VII 

 Conspectus of associations 



Associations with equivalent or similar representation in plains, mountain-front, and foothills areas 

 are shown on the same horizontal line. Very local or poorly developed representation of a community in 

 a particular zone is indicated by parentheses. 



Mixed grasslands and short-grass. — The shallow-rooted short- 

 grasses, Bouteloua and Bulbilis, dominate the compacted fine soil 

 surface of most of the plains, as the well known short-grass associa- 

 tion. Bouteloua alone, with admixture of plants of different physio- 

 logical and geographic character, is the important element of dry 



