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Atlantic’ Humid 
Transition........... Western Ari 
Pacific Hu 
: lini 
Austral vccuseesherces Upper Austral........ Lepper coreliniae 
Upper Sonoran 
Lower Carolinian 
Louisianian 
Lower Sonoran 
Lower Austral........ 
BOREAL REGION 
GENERAL DESCRIPTION 
In southern California the Boreal Region occupies the uppermost 
altitudes of the prominent mountain peaks, seldom descending 
lower than 2550 meters. It is therefore comparatively restricted, 
appearing only on the following peaks: Pinos, North Baldy, 
Pine, San Antonio, Sugarloaf, San Bernardino, San Gorgonio, 
San Jacinto, and Santa Rosa. e region is most extensive 
in the vicinity of Mount San Gorgonio and Mount San Ber- 
nardino, where it covers the high ridges connecting the peaks and 
the spurs leading from them. 
The three zones of the Boreal Region are less clearly defined 
than in more northerly territories, chiefly because the area covered 
by it is so limited. The presence of the Arctic-alpine Zone was 
first noted by Hall’, who discovered three characteristic Alpine 
species, Carex Preslit, Oxyria digyna, and Ranunculus Esch- 
scholizit on steep north slopes of Mount San Jacinto near perpetual 
snow. ‘To this scanty list Parish* has added Arenaria hirta verna 
and Aniennaria alpina from Mount San Gorgonio. The presence 
even of this small number of truly Arctic-alpine species is of con- 
siderable interest, for, as pointed out by Hall and Parish, they 
mark “the most southern known limit of the Artic flora on the 
North American Continent.” 
CANADIAN ZONE 
The two lower zones, the Hudsonian and the Canadian, are 
inseparable in southern California. Parish suggests that Pinus 
Murrayana characterizes the Canadian, and Pinus flexilis the 
3Hall, H. M. A botanical Survey of San Jacinto Mountain. Univ. Calif. 
Publ., Bot. 1: 16. 1902. 
‘Parish, S. B. Sketch of the Flora of southern"California. Bot. Gaz. 36: 
203-222 and 259-279. 1903. 
