PARRY — ALPINE FLORA. 543 



transporting movements of the prevailing winds. Hence re- 

 sults an accumulation of snow in the upper valleys, by which 

 these frozen treasures of winter are safely stored away, to be 

 dispensed in fertilizing streams to the lower valleys during 

 the dry warm season, when most required for agricultural or 

 mining purposes. 



5. The peculiar alpine vegetation, attaining to elevations of 

 14,000 feet above the sea level, is enabled to maintain its ex- 

 istence by the protection afforded by the ordinary winter 

 snows, and, in the more sheltered and deeply covered valleys, 

 includes plants which flourish also at much lower elevations. 



6. The true timber line, everywhere exhibited as a well 

 marked horizontal plane, varying in elevation, according to 

 the degree of latitude or character of exposure, from 12,000 

 feet to 10,700 feet above the sea, indicates a limit beyond 

 which the minimum winter temperature is destructive of all 

 exposed phamogarnous vegetation, and whatever in the form 

 of tree growth persists above this point, can only do so by 

 being deeply buried in the accumulation of winter snow, 

 which, weighing down their branches, gives that distorted 

 growth peculiar to such localities. 



7. In the accompanying list, comprising 141 species of alpine 

 plants, 56 are noted as exclusively alpine, or confined to the 

 bald alpine exposures; 84 species, as far as at present known, 

 are peculiar to the Eocky Mountain range, or to Northern 

 America, while the remaining 57 species are common to the 

 European or Asiatic Alps, or to high northern latitudes of 

 both continents. 



On some future occasion, in connection with a more com- 

 plete list, the writer proposes to deduce some fuller compari- 

 sons in reference to the geographic distribution of the Rocky 

 Mountain alpine flora. 



