508 



PKACTICAL BOTANY 



FIG. 378. A twig 

 of sagebrush 



Modified after 

 Schimper 



number of pines. The alpine flora, occurring 

 on the mountains toward the timber line and 

 above it, comprises many beautiful herbaceous 

 and shrubby species. The "alkali" regions, 

 with a highly saline soil, abound in such hal- 

 ophytes as the salty sage, 1 the greasewood, 2 

 the glasswort, 3 and the Western blite. 4 The 

 best known of these saline areas is the Great 

 Basin, covering an extensive area to the east 

 of the Sierra Nevada, extending nearly to 

 the Great Salt Lake. It is desolate, treeless, 

 and without grass. The less saline valleys 

 and the foothills are covered with sagebrush, 

 while the lower and more "alkaline" valleys 

 are tenanted by such decided halophytes as 

 those just named. 



In the southern part of the region of the 

 Rocky Mountain system and to the south- 

 west are found some of the principal deserts 

 of the United States, such as the Mohave Des- 

 ert, the Ralston Desert, and in southern Cali- 

 fornia the Colorado Desert. In some of these 

 the temperature for long periods in the sum- 

 mer ranges as high as 118 F., and the total 

 annual rainfall may be less than an inch. Ex- 

 treme xerophytes, such as cacti, a few palms, 

 and tree yuccas (Fig. 379), abound. 



459. The Pacific slope. The summer and 

 the winter climate of the Pacific coast region 

 differ in temperature much less than do por- 

 tions of the Atlantic coast in the same lati- 

 tude. In the southern part of the region the 

 most striking difference between seasons is 

 the contrast between their amount of rainfall. 



1 Atriplex. 



2 Sarcobatus vermiculatus. 



3 Salicomia. 

 * Suceda. 



