1903] FLORA OF SOUTHERN CALIFORNIA 221 
divisions, it is of less importance in the study of smaller areas. 
Within these narrower limits it is probable that more than one 
subzone may be traced, but much fieldwork must be done before 
this can be accomplished satisfactorily. There are indications, 
however, in the Colorado Desert of a subzone below the Larrea, 
whose limits appear to be traceable by the growth of Atriplex 
polycarpa. But for the present the Larrea zone may be taken as 
a whole, and considered as extending over all parts of the two 
deserts below 3,000" altitude (g15™). 
Above the Larrea, the zones of the two deserts, although 
analogous, are indicated by entirely different plants. In the 
Mojave Desert the first zone above is that of Vucca brevifolia. 
This belongs properly between 3,000 and 4,000 * (g15—1,220) 
altitude; occasionally, however, it descends 500% (150™) lower, 
or again carries its characteristic species as high as 7,000 * 
(2,133™). In its normal limits Juniperus californica is mingled 
with the Yucca, but does not accompany it far above them. The 
principal belt of this zone, beginning at the upper end of Ante- 
lope Valley, follows the base of the San Bernardino Range to 
Warrens Wells, and thence, along the Chuckawalla Mountains, 
at least to Virginia Dale.. A less important belt extends from 
Daggett to Pilot Knob. 
Above the first named Yucca belt is the Pifion zone, marked 
by the presence of Pinus monophylla, having an altitudinal breadth 
between 4,000 and 6,000 * (1,220-1,830™). It also begins in 
Antelope Valley, and extends, but with considerable interrup- 
tions, from Gormans Station to and beyond Warrens Wells, and 
possibly even to Virginia Dale. 
In the upper end of Antelope Valley the orographical confu- 
sion which there exists has given rise to a curious phytogeograph- 
ical anomaly. Here Pinus Sabiniana, Quercus Douglas, and dQ: 
Wislizent, trees characteristic of the western slope of the Sierra 
Nevada throughout central California, coming through Tejon 
Pass, find themselves on the eastern slope of that range, and the 
unusual sight is presented of desert foothills clothed with an 
almost unmixed growth of scrub-oaks. Here, too, are found 
Aesculus californica, Balsamorhiza deltoidea, Gilia tricolor, Layia 
