(312) 
the Klamath Gap. South of this gap the Sub-area occupies the 
Transition Zone of the Sierra Nevada and the inner Coast Ranges 
of central California, and extends through the mountains of south- 
ern California to Mount San Pedro Martir. 
In the Sierra Nevada the Transition Zone is fairly continuous, 
extending almost unbroken from the north Coast Ranges around 
the head of the Sacramento Valley, and southward along the west- 
ern slopes of the Sierra Nevada. The southern inner Coast 
Ranges and the mountains of southern California, on the other 
hand, are composed of isolated ranges. Hence great gaps occur 
in the Transition Zone of these ranges, which form barriers 
to the migration of species. Each of these sections is usually 
represented by several peculiar species, while others are con- 
spicuous by their absence. ‘The Sierran Sub-area separates, there- 
fore, into three natural divisions, the Sierra Nevada District, the 
South Coast Range District, and the San Bernardino District. 
The latter includes the Transition Zone of the San Gabriel and 
San Bernardino ranges,and the mountains southward to San 
Pedro Martir. In this district there. are several endemic species, 
such as Acer bernardinum, Ceanothus integerrimus puberulus, and 
Ceanothus Palmeri, while many of the species common in the 
northern districts are absent. 
Uprer AustTRAL ZONE 
General description.— The Upper Austral Zone in southern 
California is represented wholly by the Upper Sonoran Area, 
which includes two distinct sections, the coastal slope and the 
pion and juniper belts of the desert slopes of the mountains. 
The characteristic plants of these two sections represent two 
different floral elements. The coastal slope species are predom- 
inantly Californian, while many of those on the desert slopes 
belong to the Great Basin element. 
Coastal slope—The coastal slope of southern California is 
separated from the more northern parts of the Californian Sub- 
area> along the seaboard by Point Conception. The coast to 
*The California Sub-area, which is equivalent to Engler’s “Innerkalifornische” 
zone of the ‘“‘Westamerikanische Wisten- und Steppenprovinz,” is that part 
of the Upper Sonoran Area which lies west of the Sierra Nevada divide, and 
extends from southern Oregon to northern Lower California. The name 
“{ntramontane” has been applied to this region, but it is best to restrict that 
term to the floral district of the sub-area which lies between the Sierra Nevada 
and the Coast Ranges of central and northern California. ‘Cismontane” as 
used by Parish (J. c.) includes parts of two zones, which seems illogical. 
