VEGETATION AND ENVIRONMENT IN CALIFORNIA 233 



scarcity of water. With such facts in mind, it was suspected 

 that there might be variation in the roots of the trees of the coast 

 valleys in a similar direction which might account for the phe- 

 nomena of species distribution already noted. Further than this, 

 in the desert, where the shrubs are widely separated as already 

 described, it is found that the water table is so deep as to be 

 beyond the possibility of direct use to the plants of the areas in 

 question. Therefore, from analogy, the relation of the tree distri- 

 bution in the coast valleys to depth of perennial water was also 

 a feature to be especially examined. The leading results of a 

 preliminary survey can be briefly stated. The root system of 

 Quercus douglasii, and the typical distribution of the species, will 

 first be mentioned. As indicated by figure 1, as already stated, 

 this species inhabits foothills which may be unusually arid. Not 

 only is the water table at a great depth, but the denizens of such 

 localities are subject to the drying influences of hot summers and 

 are exposed to desiccating winds, as no other large species of the 

 genus are. An examination of the roots of several specimens 

 growing in widely separated localities shows that there is an 

 unusually large development of superficial roots, which for the 

 most part lie within 3 feet and often just beneath the surface. 

 These roots are of large diameter also and serve as mechanical 

 supports of the plant. The superficial laterals reach outward for 

 a relatively long distance from their place of origin enclosing a 

 large area surrounding the tree. The main root is usually not 

 deeper than 12 feet, although at the crown it is often fairly stout. 

 It seems fair to conclude, both from the character of the root 

 development of the species and the fact that perennial ground 

 water is beyond attainment by the roots, that, like the shrubs of 

 the desert, the Douglas oak has become adjusted so that it 

 depends wholly on the surface waters for its moisture supply. 



The Coast Live Oak, Quercus agrifolia, together with the 

 Valley Oak, Q. lohata make up the most of the open forest of the 

 valleys of the Coast Range. The latter penetrates into the inte- 

 rior and occurs in portions of the Great Valley as well. It has 

 been found- that in the latter valley the oaks are confined to 



^ Jepson, W. L., Sylva of California. Mem. Univ. Cal., vol. 2, 1910. 



