REGIONAL DISTRIBUTION 



509 



FIG. 379. Tree yucca in the Mohave Desert 

 Redrawn from a photograph by Coville 



At Stanford University, thirty miles south of San Francisco, 

 the rainy season usually begins in October and lasts until 

 April. June, July, August, and September are usually rain- 

 less. At San Diego the dry season begins in April and lasts 

 for seven months. Vegetation begins with the autumn rains 



