338 A. Gray—North American Flora. 
a single ubiquitous Poplar, their higher crests bearing a well- 
developed alpine flora. is is the arctic flora prolonged south- 
ward upon the mountains of sufficient elevation, with a certain 
admixture in the lower latitudes of types pertaining to the 
lower vicinity. 
here are almost 200 alpine Phzenogamous species now 
known on the Rocky Mountains; fully three-quarters of which 
are arctic, including Alaskan and Greenlandian; and about 
half of them are known in Europe. Several others are North 
Mexico, and there they are few and small. In these southern 
and of other vegetation, mostly of Rocky Mountain types. . 
Desolate and desert as this region appears, it is far from uD!D- 
teresting to the botanist; but I must not stop to show how. 
Yet even the ardent botanist feels a sense of relief and exultation 
when, as he reaches the Sierra Nevada, he passes abruptly into 
perhaps the noblest coniferous forest in the world,—a forest 
coast, from the southern part of California to Alaska. 
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