142 ERYTHEA. 



comes forth from the hillside with a rush and a volume, that 

 is unsurpassed. For miles along the Sacramento Eiver, the 

 hillsides are washed with the falling water as it flows forth, 

 not in rivulets but in sheets. 



However, the lack of running water and the dryness of the 

 soil can hardly account for this flora showing so little affinity 

 with what is expected on high mountains in the Northern 

 Hemisphere. The explanation must be sought in the 

 geological history of the mountain. Compared with the 

 Rocky Mountains, the Cascade and the Sierra Nevada Moun- 

 tains, to which Mt. Shasta belongs, are quite recent; nor do 

 they extend to ttie Arctic regions, so the connection with the 

 extreme north is not so close nor the relationship so intimate 

 as in the Eocky Mountains. According to Asa Gray, the 

 entire alpine flora of the Pacific Coast contains fewer species 

 and a smaller proportion of arctic species than the Rocky 

 Mountains, as shown by the following table: 



Alpine species in the Eocky Mountains, 184; 56% Arctic. 



Alpine species in the Pacific Coast Mountains, 111; 45% Arctic. 



The volcanic nature of Mt. Shasta may have had something 

 to do with cutting it otf from glacial connection with the 

 north. While nobody knows or even presumes to guess 

 when the last eruption took place on Mt. Shasta, evidences of 

 recent volcanic action are known in the same region. At 

 Cinder Cove near Lassen's Peak volcanic action is thought to 

 have ceased only two hundred years ago, and solfataras are 

 quite common throughout the entire region, one on the top 

 of Mt. Shasta seeming to indicate that the volcano is not yet 

 entirely extinct. Its isolated position, too, may have had 

 considerable influence in depriving it of species found on 

 other high mountains of the Pacific Coast and giving it some 

 local species ; probably the dryness of the soil has pro- 

 hibited many species and greatly restricted the number of 

 individuals; but whatever is the reason the fact remains that 

 on Mt. Shasta there is an almost total lack of those species 

 that connect the Rocky Mountains with the Alps and unite 

 the northern parts of Europe, Asia and America. 



