228 W. A. CANNON - , 



GEOGRAPHICAL DISTRIBUTION OF THE FLORA 



I have insisted somewhat upon the physiographic and the 

 chmatic features of Cahfornia because some appreciation of these 

 physical factors should assist in forming a proper background for 

 the interpretation of many features of its flora. We may turn 

 now and consider for a moment the geographical distribution of 

 the vegetation of the state. 



We have grouped the physiographic provinces, which are also 

 climatic provinces, into mountains, valleys, and deserts. These 

 regions, however, are commonly subdivided into life zones, which 

 in certain ways is a convenience. In the mountains the life 

 zones, each having characteristic rainfall and temperature, range 

 from the Transition, through the Canadian and the Hudsonian to 

 the Boreal. The annual precipitation is from 25 to 75 inches, as 

 means, but it may greatly exceed this, as for example at Bowman's 

 Dam, in the Sierras, 135 inches of rain has been recorded, and 

 this does not take into account snow fall. The foothills, greater 

 valleys, and the deserts are included in the Sonoran zone, and the 

 mean precipitation is 15 inches or less. Since the Sonoran life 

 zone may comprise the greatest part of the surface of California a 

 xerophytic stamp to its flora, as remarked above, is to be expected. 



In characterizing the life zones, it will be sufficient for present 

 purposes, to mention categorically certain representative arboreal 

 species. Of the Hudsonian, Pinus albicaulis is typical; of the 

 Canadian, Pinus inonticola and P. jeffreyi; and of the Transition, 

 Pinus lambertiana and P. ponderosa. In the Sierras, the Big 

 Tree occurs in the Transition, and in the coast ranges the redwood 

 is in the same zone. 



ENDEMIC SPECIES 



The general outline of the features of the geographical distri- 

 bution of plants in California does not make a special point of the 

 large number of endemic species, some of which have avery hmited 

 range. This constitutes a very interesting phase of the flora of 

 the state. For the present purpose it will suffice to mention some 

 of the best known species of restricted distribution. 



