34 DESERT BOTANICAL LABORATORY 



Basin and the Colorado desert were shown approximately within the 

 districts which may appropriately be designated as desert at the present 

 time. This conception of the matter is shown in F'ig. J, being a map 

 from a text book on physical geography published in 1859. 



Further exploration and utilization of desert areas in agricultural and 

 mining operations led to the abandonment of the term desert as applied 

 to all the regions shown in -P'lg. 3 except those about the lower Colo- 

 rado river and near Great Salt lake. A study of the physiographic, flo- 

 ristic, and meteorological features of western North America has re- 

 sulted in delimiting two great desert areas by the geographer, botanist, 

 and meteorologist. The outlines of these might be roughly traced by 

 lines connecting the stations shown in I^t'g'. i. These regions may be 

 designated as the Sonora-Nevada desert and the Chihuahua desert. 



The Sonora-Nevada desert embraces portions of Utah, Idaho, 

 Washington, Oregon, Nevada, California, Arizona, Baja California, 

 Sonora, and Sinaloa. The northern portion of this region is mainly 

 comprised in the Great Basin and embraces the beds of a number 

 of ancient lakes and the surviving Great Salt lake. Other special 

 physiographic features of interest in this connection are the areas 

 which bear the names of Snake River desert of Idaho ; The Sage 

 plains of Washington ; the Lava Beds of Oregon ; the Ralston desert in 

 Nevada ; Death Valley, Mohave desert, Colorado desert, Salton desert, 

 in southern California and Arizona ; the Painted desert in Arizona 

 and New Mexico ; and the Sonora desert in Mexico. The southern 

 portion of the region consists of a series of extended slopes and ter- 

 races traversed by many ranges of hills and mountains with peaks 

 of some altitude. Along the shores of the Gulf of California and of 

 the Pacific Ocean proper, the desert area includes the entire surface 

 to within a few feet of the water's edge and the xerophytic vegeta- 

 tion of the plains comes into direct contact with the mangrove and 

 strand flora. 



The Chihuahua desert occupies the central table land of Mexico east 

 of the Sierra Madre, extending as far south as San Luis Potosi and in- 

 cluding parts of the states of Coahuila, Chihuahua, and Texas and also 

 portions of Arizona and New Mexico. The Bad Lands of the Dakotas 

 and Montana and the Red desert of Wyoming, both included in the 

 "Great American desert" (Fig. 2), might be regarded as a north- 

 ern arm of this region for the purposes of this paper. The arid 

 portions of this area consist, for the most part, of great valleys en- 

 closed by parallel ranges of mountains which in some instances attain 

 such altitudes as to be timber clad and even bear an alpine vegetation. 



