areas and a greater rainfall. In its primitive condition it is 

 characterized by vast numbers of annuals which germinate with 

 the winter rains and flower during the vernal period; characteris- 

 tic perennial herbs are California Poppy (Eschscholzia califomicd) 

 and Gum Plant {Grindelia camporum). Large areas of alkaline 

 flats are encountered, especially on the west side of the valley. 

 On the valley floors or undulating plains the traveler finds small 

 depressions, a few meters square and a few centimeters deep, 

 which fill with water in the rainy season. When a little deeper, 

 well-defined and numerous, they take the name of "hog-wallows". 

 With the coming of the dry season the water evaporates, and the 

 beds of these pools in late spring or early summer give rise to a 

 distinctive flora composed of a number of species of mostly 

 annual plants. The narrow curtain of trees along the streams is 

 composed of CaUfornia Sycamore (Platanus racemosa), Fremont 

 Poplar {Populus fremontii), and a few willows — though the 

 willows are not confined to the valley floors. 



The Upper Sonoran Zone may often be divided into the lower 

 foothill belt and the chaparral belt. The lower foothill belt is a 

 grassland formation, sometimes with a scattered growth of Blue 

 Oak (Quercus douglasii) and Engelmann Oak {Q. engelmanii), 

 plus several characteristic herbs. Above the lower foothill belt 

 is the chaparral belt, or hard chaparral. It has an average altitude 

 of 100 to 400 feet (30 to 122 m) and is characterized by the 

 presence of extensive brush lands. Most of the species represent 

 extreme arid-land types and possess various markedly xerophytic 

 structures, such as small or reduced leaves, entire leaves, 

 thickened epidermis, hard and very dense wood, vertically placed 

 leaves, small flowers, and seeds adapted to xerophytic conditions. 

 The most widely spread and characteristic species are three spe- 

 cies of California lilac (Ceanothus), several manzanitas (Arcto- 

 staphylos spp.), and Mountain Mahogany (Cercocarpus betu- 

 loides). Many of the species of Chaparral inhabit rocky or 

 gravelly slopes or ridges and grow on well-drained slopes. 



Coastal southern California, below about 4,000 or 5,000 feet 

 (1,219 or 1,524 m), lies mostly in the Upper Sonoran Life Zone. 

 Some of the more important species are: Goldenbowl Mariposa 

 {Calochortus concolor), and the related C plummerae; Englemann 



57 



