20 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [VolYX.. 



Phacelia in Hydt'ophyllacew, but most of the species are below the for- 

 est district and of westward range. 



Eriogonum of Folygonacew, of which the same is to be said, although 

 a few species are conspicuous in the wooded region. 



Compositce are very prominent, as they are throughout Korth America^ 

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

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

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

 and Erigeron is more x>rominent than Aster. 



The number of species of Astragalus in the Eocky 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. ccerulea 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 th& 

 higher mountains and ravines of the Great Basin, i)robably more of them 

 than are yet recorded. Of additional species only two come to mind^ 

 and both are peculiar. They are — 



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



Feraphyllum ramosissimum, Nutt., a peculiar Pomaceous genus, along- 

 the western rim of the Great Basin. 



A few other higher-mountain species of CeanotJms 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 Reoions 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 Loicer Eoclry fountain Slopes, 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 parvifolius, along with C. ledifolius 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 of 

 this i^eculiar genus, although the latter was founded on a Mexican 

 species. 



Coioania Mexica^ia, which is likewise Mexican, as the name intimates. 



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

 but not ascending above the base of the mountains. 



