( 307 ) 
CHart or THE AnnuaL RarinratL Recorps, Crassifiep ACCORDING TO 
THE Puyrocrocrapuic SECTIONS 
(Each column represents one eighth the actual rainfall) 
Deserts, altitude — 87 to 917 meters, Lower Austral Zone; rainfall 64.2 cm. 
Mountains, altitude 1600 to 1780 meters, Transition Zone; rainfall 798 cm. 
Foothills, altitude 847 to 1321 meters, Upper Austral Zone; rainfall 488.7 
fe ea at 
Interior valleys, altitude 400 to 454 meters, Lower Austral Zone; rainfall 324 
“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 
Boreal... . 0... ....005 Hudsonian 
Canadian 
1Engler, A. Syllabus der Pflanzenfamilien, 213-222 
2Merriam, C. H. Life Zones and Crop Zones of he ee States. Bull. 
U.S. Biol. Survey, No. 10. 1898. 
