20 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.vj 



Phacelia in HydrophyUacece, but most of the Bpecies are below the for- 

 est district and of westward range. 



Erioganum of Polygonacece, of which the same is to be said, although 

 a few species are conspicuous in the wooded region. 



Composite are very prominent, as they are throughout North America. 

 and the genus Aplopappus might be added to the foregoing; but the 

 most characteristic genera are not in the wooded region. There, too r 

 the species of Solidago and of Aster are less numerous than at the East, 

 and Erigeron is more prominent than Aster. 



The number of species of Astragalus in the Rocky Mountain and more 

 western districts is inferior only to those of Asia, but they mostly affect 

 the unwooded plains. 



Peculiar to and conspicuous in the cooler wooded region are the two 

 beautiful long-spurred, species of Aquilegia, A. cccrulea and A. chrysantha, 

 the former alpestrine, the latter at lower elevations, neither found north 

 of Colorado. 



A few of the Rocky Mountain wooded-region shrubs occur on the 

 higher mountains and ravines of the Great Basin, probably more of them 

 than are yet recorded. Of additional species onlj- two come to mind, 

 and both are peculiar. They are — 



Shepherdia rotundifblia of Parry, in the mountains of Southern Utah. 



Peraphyllum ramosissimum, Xutt., a peculiar Pomaceous genus, along 

 the western rim of the Great Basin. 



A few other higher-mountain species of Ceanothus come in from Cali- 

 fornia, as to various herbs ; but we call to mind no characteristic species 

 of the basin which belong unequivocally to the forest district. 



III. — Woodless Regions below Forest. 



These may be distinguished into the lower mountain slopes, the west- 

 ern arid district, of which the so-called Great Basin is the center and 

 the exemplar, and the less arid, unbroken plains east of the proper 

 Rocky Mountains. 



1. The Lower Eoehy Mountain Xlojies, including the "parks," so called. 

 Of Colorado and valleys which are not condemned to a saline vegetation. 

 partake of the growth above and below, but they have a good number 

 of characteristic plants. The prevalent characteristic shrubs are largely 

 RosaceOUS, They are: 



Cercocarpus par trifolius, along with C. ledifoUus when that is not reck- 

 oned among the trees; the former a species which is even more common 

 on all Californian foot-hills. These districts are the headquarters oi 

 this peculiar genus, although the Latter was founded on a Mexican 



species. 



Oowania Mexicana, which is likewise Mexican, as the name intimates. 

 Purshia tridentata, which extends much farther north than the others, 

 but not ascendin > the base of the mountains. 



