DESERTS AND DESERT FLORA OF THE WEST 

 Colorado River on the east and the mountain divide 

 of southern California on the west. It is principally 

 the bed of an ancient inland sea or lake, with peb- 

 ble-covered beaches that are still discernible along 

 the base of the surrounding mountains. At one time 

 this depression was part of the Gulf of California. 

 Along its eastern shores the Colorado River de- 

 posited the materials ground from the Grand Canon. 

 Finally a great delta was formed across the gulf 

 to the Cocopa Mountains, and that part of the gulf 

 so cut off became a desiccated sink. But time and 

 again the flood waters of the Colorado have cut 

 channels through the delta and partially refilled the 

 basin. Definite proof of these vagaries of the river 

 are found in the two channels, known as the Alamo 

 and New River, that lead from the delta into the 

 basin. And the presence of the lakes is shown by 

 the numerous shells of fresh water mollusks scat- 

 tered through the soil of the basin. 



One of the most surprising characteristics of 

 the flora of the Salton sink is the absence of cacti, 

 yuccas and other succulents. 



The most striking botanical feature of the Colo- 

 rado Desert, and the most picturesque tree in Cali- 

 fornia, is the desert palm, Washingtonia filifera. This 

 unique tree is limited in its native state to a few 

 isolated groves fringing the base of the mountains 

 at the northwestern end of the Colorado Desert. 

 Groves may be seen from the station at Indio, about 

 eight miles to the north, at the base of the Chucka- 

 walla Mountains. But the most interesting grove 

 is in Palm Canon at the eastern base of San Jacinto 

 Mountain. These are splendid trees, with straight, 

 unbranched trunks, 80 to 100 feet high, crowned 

 by great tufts of spreading fan-shaped leaves and 

 clothed well down the trunk with withered leaves 

 that lie pendant along the sides in great thatch-like 

 masses. (See PL XXIV.) 



In visiting this grove one will encounter many 

 plants not seen in the Salton sink. Two cylindrical 

 opuntias, Opuntia echinocarpa and Opuntia bigelovii, 

 are found in this region. They may be distinguished 

 even from the car window by the stout erect habit 

 and more or less evident central trunk of bigelovii. 

 The curious little gymnosperm, Ephedra nevadensis, 

 with slender equisetum-like branches, is a common 

 shrub, as is Gaertneria (Franseria) dumosa and 

 Encelia farinosa, a compositaceous shrub with 

 silvery gray leaves and bright yellow flowers of the 

 sunflower type. Around Palm Springs and between 

 the Springs ana the Canon one will encounter the 

 mesquite, screwbean, palo verde, smoke tree, and 



175 



