( 307 ) 
Cuart or THE ANNUAL RAINFALL ReEcorps, CiassiF1ED ACCORDING TO 
THE PHYTOGEOGRAPHIC SECTIONS 
(Each column represents one eighth the actual rainfall) 
Hoes alntode _ ESO to Hea anita Es raped: Zone, rainfall ae 2cm. 

Foothills, areas Pre to 1321 ERS os Austral Zone; rainfall 488.7 
cm. 

Interior valleys, altitude to 454 meters, Lower Austral Zone; rainfall 324 
cm. 
Coastal valleys, altitude 10 to 279 meters, Upper Austral Zone; rainfall 
340.5 cm. 
San Diego district, altitude 10 to 100 meters, Lower Austral Zone; rainfall 
238 cm. 
PHYTOGEOGRAPHIC FEATURES 
GENERAL DESCRIPTION 
Phytogeographically southern California is separated into three 
clearly defined floral divisions—the coastal slope, the mountain, 
and the desert. Each of these divisions has derived its charac- 
teristic plants from different floral elements. ‘The species of the 
coastal slope are principally of Californian origin; the species 
confined to the mountains, boreal or of boreal ancestry; and those 
of the deserts, endemic or migrants from the Great Basin, Sonora, 
or Lower California. To discuss these different floras intelli- 
gently it is essential that some general system be followed. 
Engler’s! arrangement has many commendable features, but 
Merriam’s? system of North American life zones has been more 
completely worked out for this country and is therefore adopted. 
An outline of Merriam’s life zones for North America north of 
the tropics is as follows: 
Region Zone Area 
Arctic-alpine 
Borealinencn tarts = cee s Hudsonian 
Canadian 
1Engler, A. Syllabus der Pflanzenfamilien, 213-222. 1907. 
2Merriam, C. H. Life Zones and Crop Zones of the United States. Bull. 
U. S. Biol. Survey, No. 10. 1898. 
