12 UniversHij of California Puhlications. [botany 



south, it need not interfere with the use of the life zones as they 

 jir(> now understood, nor with the nse of the terras by which they 

 arc couniionly designated. In working on the flora of California 

 it has bt'cn found tliat the division of the montane region into 

 life zones has been much more satisfactory than the use of the 

 four " i-egions " as i)roposed by Schimper.* 



Accepting then this division of the montane flora, we find five 

 j)rimary life zones completely encircling San Jacinto Mountain 

 wliich, given in the order of their occurence as one ascends from 

 the l)ase, are as follows: 



Upper Sonoran 



I Lower Transition 

 Transition - 



( ri)]ier Transition 



Canadian 



Hudsonian 



Arctic-alpine. 



For the altitudes over which each of these zones extends the 

 reader is referred to the map of life zones (plate ii). 



As pointed out l)y Covillet, the plants most valuable in 

 determining floral zones are the perennials. This is not only 

 because they are the most conspicuous and therefore the least 

 likely to be overlooked, but also because annuals represent 

 the conditions of but a single season of growth, the importance 

 of this being clear when we consider that the conditions are 

 likely to undergo considerable change from year to year. In the 

 preparation of the list of species for each zone therefore all 

 annuals have been excluded. 



It is furtlici- to be noted that these lists are not intended to 

 be c(mii)lete, only the more characteristic plants being chosen. 

 It is hoped that tliis will not only give an idea of the nature of 

 the vegetation of each of the various zones but that it will also 

 bo an aid in working out the life zones on other mountains. 



UPPER SONORAN ZONE. 



San Jacinto jNIountain is com])letely (mcircled by the Upper 

 Simorau Zone, wliich extends from its base to altitudes ranging 



*A. F. W. Schimper, Pflanzengeographie 7:i7(1901). 

 tContr. U. S. Nat. Ilorl.. iv. 17-18 (lSi):i|. 



