1 52 



OUTLINE OF PLANT GEOGRAPHY 



arid portions of this desert develop an extremely interesting 

 vegetation, in which Cacti play an important role and comprise 

 numerous species, ranging in size from the low-spreading prickly- 

 pears and little melon-cacti, to the giant Suarro (Cereus giganteus), 



Fig. 40. — "Ocatilla" (Fouquiera splendens), Colorado desert. 

 Photo., Dr. W. S. Cooper. 



whose huge fluted columns are sometimes 30 to 40 feet high, and 

 the most conspicuous objects in the desert landscape. 



Creosote-bush (Larrea), Palo-verde (Parkinsonia), and the ex- 

 traordinary Ocatilla (Fouqwira splendens) are also characteristic 

 of this region. The latter consists of a cluster of unbranched 

 slender stems, 8 to 10 feet long, bearing small bright green leaves 

 at times, but mostly quite bare. In the spring each wand is tipped 

 with a cluster of bright red flowers. 



In seasons of heavy spring rains, the ground is covered for a 

 brief period with a carpet of showy flowers, but these soon dis- 

 appear with the intense dry heat of the desert summer. 



In the vicinity of the Colorado desert are found the only native 

 1 difornian palms. Rising abruptly from the desert to a height 

 of 10,000 feet, the San Jacinto mountains have at their base 

 canyons opening on the desert. Some of these are watered by 



reams which lose themselves in the desert sands, but the floor 

 of the canyons is permanently moist. 



