Western Desert Regions; general remarks. 283 
zona and New Mexico; and the Sonora Desert in Mexico. The southern 
portion of the region consists of a series of slopes and terraces with many 
ranges of hills and mountains with peaks of same altitude. Along the shores 
of the Gulf of California and of the Pacific Ocean, the desert area includes 
the entire surface to within a few feet of the water’s edge and the xerophytic 
vegetation of the plains comes into direct contact with the mangrove and 
strand flora. 
The sources and distribution of the floral element of this great western 
desert region now claim our attention. The northern desert, occupying portions 
of Washington, Oregon and Idaho, is a huge sage brush plain, broken by 
numerous low mountain ranges having little or no timber. Between these 
mountains are the desert sinks and “sleek deserts” (alkaline stretches entirely 
destitute of vegetation). All except the “sleek deserts” are covered with a 
shrubby growth of sage, salt bushes and greasewood. 
Pine Forest range in Oregon has on the highest elevations a scanty growth 
of pine, Pinus albicaulis as found at the extreme upper limit of timberline on 
Mt. Shasta, California (Fig. 7), while neighboring mountains such as Steins 
Mountain have no pines at all. The latter have much more of Funiperus 
virginiana than the former. Pinus ponderosa var. scopulorum, Populus tremuloides, 
P trichocarpa, constitute the remainder of the arborescent species of the 
northern Great Basin. The desert regions of the north are very different from 
those of Arizona and these differences are sufficient to delimit a northern 
Phytogeographic area. There is a very noticeable absence of the creosote bush 
Larrea mexicana, and the various species of Cactaceae, their place being taken 
by the spiny salt bush Arripler confertifolia, bud sage Artemisıa spinescens, 
and black sage Artemisia tridendata. There is, however, a strong similarity. 
The ephemeral spring vegetation of Polemoniaceae, Cruciferae and Boraginaceae 
(Gilia, Amsinckia, Eritrichium) corresponds very closely, as far, er. 
with the conspicuous fugacious spring plants of the Arizona desert’'). 
No portion of the central desert region (Nevada and Utah) is destitute of 
excepting only the alkali flats, 
th of Sarco- 
„veral species of Suaeda, certain chenopodiaceous P ‚acilis. The minor 
Distichlis maritima (Brisopyrum spicatum) and Spartina 8 
REN 
Great Basin. Bureau 
x GrirFitus, Davıp: Forage Conditions of the northern Border of the 
° Plant Industry (U.$.). Bulletin No. 15 and Bulletin No. 39- 
