THE ALPINE FLORA OF MT. SHASTA. 141 



somewhat from the Colorado plant of the same name, but 

 probably not sufficiently so to be of any moment. Cdstilleia 

 is an American genus with the exception of one or two 

 species in northern Asia. The genus is at home equally in 

 maritime, alpine and Sonoran regions. 



8. Eriogonum pyrolcefolium Hook, is a member of a 

 genus especially noticeable throughout the Sonoran region. 

 Outside of some genera of Compositte, and perhaps Chenopo- 

 diacese, no genus is so well represented there in number of 

 species and individuals. 



The rest can hardly be considered truly alpine, as they 

 are found also below the limit of trees; but even if they 

 were to be included, they do not show closer boreal affinities 

 than the first eight. 



This comparison seems to show, that the alpine flora of 

 Mt. Shasta is more closely allied to Pacific Coast and Sonoran 

 plants than to those from the north. 



Why should this mountain, surpassing in altitude any of 

 the peaks of the Eocky Mountains^ have only one cosmopoli- 

 tan alpine plant? Primula, Dryas, Oentiana, Potentilla, 

 Polemoninm, the numerous representatives of Cruciferse, 

 Ranunculacese and (with one exception) Caryophyllaceae are 

 all wanting. 



Above the tree-limit there is not much chance for plants to 

 grow; great stretches of snow and lofty cliffs of volcanic 

 rock leave but little available soil. Water is scarce. From 

 the base up to the snow -fields there are only three places 

 where water is obtainable. The little streams, that trickle 

 from the snow-banks in the Kocky Mountains and gradually 

 unite into rivulets, are totally lacking on Mt. Shasta. This is 

 easily understood, when the volcanic character of the moun- 

 tain is considered. It is an immense lava -cone. The snow 

 that melts under the summer- sun, sinks down through the 

 porous rock and issues at different strata in springs of enor- 

 mous volume. Undoubtedly, the springs along the Sacra- 

 mento River near Dunsmuir, Shasta Springs and thereabouts 

 have the snows of Mt. Shasta as their source. ^ The water 



iGeol. Survey of Calif. Vol. I. p. 350. 



