18 Universiiy of California PiihHcdHons. [botany 



On aiscendiuj? the iiiouutain from any one of the four sides a 

 dense growth of chaparral is found covering all the lower slopes 

 and completely occupying the Upper Sonoran Zone. On the 

 north this belt is separated from a similar one of the San Bernar- 

 dino Mountains only by a narrow strip, the San Gorgonio 

 Pass, which flares out to the east to unite with the Colorado 

 Desert. On the southeast it connects directly with the chaparral 

 belt of the Toro Mountains, while to the south it spreads over a 

 series of low hills, ultimately reaching the Palomar and Cuyamaca 

 Mountains. On the west it is bounded by the low plains of the 

 San Jacinto Valley. The mountain is thus seen to be completely 

 surrounded by a brush covered area of considerable width, which 

 separates the forests of its higher slopes from those of the other 

 Southern California ranges . 



On closer examination of this chaparral belt we find the 

 principal shrul> to be the Chamisal ( Adenostoma fascirulatiimj 

 which covers the hills with almost impenetrable thickets often 

 miles in extent, while growing with it but in less abundance are 

 several species of Manzauita, Ceanothus, Yucca and, on shaded 

 slopes, the Mountain Mahogany f Cercocarpns heUdcefoliusJ, the 

 Tree Poppy ( Dendromecon rigidumj and other species. 



Characteristic foot-hill annuals are abundant during the 

 spring and early summer. The majority of these blossom in the 

 shade of the higher bushes, some of them in small clearings, 

 while, by the elongation of their stems and peduncles, a few 

 ambitious species render their flowers conspicuous by carrying 

 them above the sea of chaparral. 



The plants of this belt exhibit strong xerophile characters, as, 

 for example, in the reduction of the leaf surface, this being 

 especially noticeable in the case of the Chamisal and of Bebhia 

 juncea, while in the Manzanitas the same end is often attained 

 by a twist in the i)etiole, the leaf being thus brought into a 

 vertical position. Moreover in the shrubby species the leaves are 

 nearly always thick ;ni(l leathery, besides being often covered 

 witli a dense, woolly pubescence, as in SpJueralcia amhigna, 

 Eriodictyon tomentosum, and others, while there is scarcely a 

 glabrous ])l;iti( to be found anywhere in the chaparral region. 



An excellent opjwrtunity of studying the root systems 



