DESERT REGIONS OF NORTH AMERICA. 35 
with hardy leaves are included. Ephedra, Gaertneria albicaulis, Oenothera 
claviformis, Lupinus mexicanus, Abronia villosa, Astragalus vaseyi, Plantago 
scartosa, Langlorsia schottit, Stillingia annua, Asclepias subulata, and Fou- 
quierta splendens are typical examples, while a few forms with deeply 
lying bulbs are also found here, including Hes perocallis undulatus. 
To the eastward are to be found series of mountain ranges, generally 
of considerable height and including many old volcanic cones, in which 
the water-supply and the precipitation are extremely scanty. Among the 
ranges, and in a manner inclosed between them, are gently sloping valleys 
and great plains with no well-defined drainage, which bear a characteristic 
shrubby vegetation. In the higher levels are encountered succulents 
and storage forms of the general character found in the Torres district. 
Burseras, known as “‘torote,”’ are abundant, and a copal tree (Terebinthus 
macdougali, plate 40) is found near the Gulf. Accurate information 
concerning this region is, however, difficult to obtain, and it may be made 
the object of explorations from the Desert Laboratory. Accounts of 
some explorations in this region are to be found in Bull. Amer. Geog. Soc. 
1907 (plate 34). 
THE COLORADO DESERT. 
The Colorado Desert, which has been mistakenly supposed by many 
writers to lie in the State of that name, in reality is situated in the south- 
eastern part of California. Perhaps no better description of its limits 
could be made than from the following citation from Prof. W. P. Blake 
(Explorations and Surveys for a Railroad Route from the Mississippi 
River to the Pacific Ocean, War Department, 1855, p. 228), who examined 
this region in 1852, and by his barometric observations first established 
the fact that it included a basin lying below sea-level. 
The region of country known as the Colorado Desert is a long plain or valley 
west of the Colorado River, near its mouth. It extends from the base of Mount 
San Bernardino to the head of the Gulf of California, and is separated from the 
coast slope by the Peninsula Mountains. The limits of the plain on the north 
and northeast are determined by the ranges of mountains which extend from San 
Bernardino Mountain to the mouth of the Gila and beyond into Sonora. On the 
south and east the desert is bounded by the Colorado River and the Gulf. The 
area thus bounded is a long and nearly level plain, extending in a northwest and 
southeast direction from latitude 43°)on the north to the parallel of 32° on the 
south. Its greatest length in this direction, from the base of San Bernardino 
Pass to the Gulf, is 180 miles, or, measuring from the base of the pass to the 
mouth of the Gila, it is 140 miles. Its greatest width is about 75 miles, measured 
in a north-and-south direction along the Colorado River, between the head of the 
Gulf and the mountains north of Fort Yuma. The plain narrows as it extends 
back from the Colorado River and opposite Carrizo Creek its width is reduced to 
between 60 and 70 miles, and still farther westward, near to its extremity at the 
San Bernardino Pass, it will not average over 25 miles. These measurements are 
approximate, and give for the whole area west of the Colorado about 8,250 square 
miles; or, including a portion of the plain beyond the river, about 9,000 square miles, 
