234 W. A. CANNON 



the alluvial deltas where the soil is a loam, and hence fairly 

 pervious to the rains. 



The Coast Live Oak frequently occurs where the depth to the 

 water table is considerable, 35 feet, or over, although it is found 

 also where the perennial water is more shallowly placed. In 

 certain situations, as where gravelly strata intervene between the 

 surface and the water table, it is clear that the roots of this species 

 do not penetrate to the zone of perennial water. A study of the 

 roots of Q. agrifolia, in fact, shows that the species has a very 

 strongly developed superficial system, most of the roots being 

 within 3 feet of the surface. In this regard similar to the root- 

 system of the Douglas oak, the roots of the Live Oak, however, are 

 much more numerous and smaller and also very evidently adjusted 

 to acquire practically all of its moisture in mature specimens, 

 from the superficial water derived directly from the rains. Hence, 

 where the rains are scant, or where there is no run-off from higher 

 and adjacent areas, so that the superficial soils are not sufficiently 

 moist throughout the year, the species is wanting. 



The story of the Valley Oak, Q. lohata, is very different from 

 that of the two species just mentioned. Quercus lohata finds its 

 best development where the soil moisture is abundant, partic- 

 ularly where the depth to the perennial water supply is probably 

 not great. Hence it is the Valley Oak bj^ necessity, as it is the 

 Valley Oak par excellence. In the coast valleys it appears often in 

 association with the Coast Live Oak, but in the valleys further 

 from the sea it is confined to the vicinity of streams or to other 

 places where the moisture relations are relatively good. Under 

 favorable circumstances this species develops into large trees. 

 For example, one specimen was seen near Clear Lake which had a 

 spread of top which was estimated to be 144 feet. 



An examination of the roots of the Valley Oak shows that they 

 have a type of development unlike that of the other oaks already 

 mentioned. There is an especially well developed main root and 

 numerous and large laterals. Both the main root and the laterals 

 are apparently capable of deep penetration, and the laterals may 

 extend widely as well. Therefore, the greatest development of the 

 roots of this species does not occur near the surface of the ground, 



