OBSERVATIONS IN THE COLORADO DESERT 85 



phylla, all common in the desert canyon. Rarer plants were Caly- 

 coseris Wrightii var. calif ornica, Coldenia brevicalyx, Malperia tenuis 

 and Astragalus sabulonum. 



.MOUNTAIN SPRINGS 



Mountain Springs is in San Diego county, almost on the line 

 dividing it from Imperial county, and some 5 miles from the 

 Mexican boundary. A steep escarpment here divides the Colo- 

 rado desert from the confused region of mountains, seldom ex- 

 ceeding 5000 feet in altitude, which reaches to the shores of the 

 Pacific. An excellent road, cut in the rocky sides of Myers' can- 

 yon, is the artery of travel between Imperial valley and the port 

 of San Diego. On the desert side it is approached from Coyote 

 Wells, the altitude of which is only 225 feet. An ascent of 

 865 feet in a distance of 6.5 miles intervenes to the base of the 

 mountain wall. Thence to the springs (alt. 2370 ft.) is 5.5 miles 

 and a rise of 1260 feet, and from there to the summit 3.5 miles and 

 a rise of 861 feet, making its altitude 3231 feet above sea level. 



These data will convey some idea of the extreme abruptness 

 of the desert rim at this part of its course, and this will be more 

 evident when it is remembered that the canyon mileage is meas- 

 ured along the road, which by its convolutions attains an easy 

 grade, so that the direct incline would be no more than one-fifth 

 of the road distance. It is evident, therefore, that there is here 

 compressed in a short space a difference of altitude which should 

 manifest itself by a corresponding differentiation of the plant 

 population. 



Such differences exist, but not as marked as might be expected 

 were certain other factors not taken into consideration. There 

 are no records of the rainfall at Mountain Springs; probably it is 

 slightly, but only slightly, greater than that upon the open desert 

 beyond. The temperature, especially in winter, must be some- 

 what cooler. But it must be remembered that this precipitous 

 canyon faces the burning Salton Basin, while behind it are low 

 mountains whose aridity is little modified even to the borders 

 of the sea. The passage is not from one phytogeographical 



