those listed above occur among the trees, and during the spring 

 following a wet winter the ground among the shrubs and trees is 

 carpeted with spectacular masses of showy annuals in flower. 



Creosote Bush Scrub (Plate 16; Map 3) 



The last plant community to be discussed is the one which is 

 the most widespread in the southern desert portions of California. 

 This is the Creosote Bush Scrub. Creosote Bush is Larrea divari- 

 cata (Zygophyllaceae), a rather attractive, tall shrub that domi- 

 nates much of the desert landscape below 3,500 feet (1 ,067 m) 

 from Inyo County southward (Plate 16A). It also occurs locally 

 in some interior cismontane valleys such as at Poso Creek, Tulare 

 County, and localities in western Riverside County. Also present 

 as plant associates of the Creosote Bush are Burro Weed {Fran- 

 seria dumosa, Compositae), the colorful and spiny Ocotillo 

 (Fouquieria splendens, Fouquieriaceae), Brittle Bush (Encelia 

 farinosa, Compositae), Cheese Bush (Hymenoclea salsola, Com- 

 positae), and prickly pears and chollas of the cactaceous genus 

 Opuntia (Plate 16B). Because of the limitations of water supply 

 in the area occupied by the Creosote Bush Scrub, the water 

 courses (which are dry most of the year) support a characteristic 

 flora that takes advantage of the abundant supply of water during 

 rainy periods of the winter or summer (Plate 16D). Some bota- 

 nists would consider this wash woodland to represent a separate 

 plant community. Certain desert trees and shrubs generally occur 

 only along these water courses. These include Palo Verde {Cer- 

 cidium floridum, Leguminosae), Smoke Tree (Dalea spinosa, 

 Leguminosae), Catclaw {Acacia greggii, Leguminosae), Desert 

 Willow (Chilopsis linearis, Bignoniaceae), Chuparosa (Beloperone 

 californica, Acanthaceae), and Desert Lavender (Hyptis emoryi, 

 Labiatae). Another interesting tree that occurs around moist, 

 somewhat alkaline spots in the Creosote Bush Woodland is Cali- 

 fornia Fan Palm {Washingtonia filifera), which often coexists with 

 various willows (Salix spp.). This species is rather uncommon in 

 nature, although it is widely planted as an ornamental in sub- 

 tropical regions. 



The seeds of many wash woodland tree species are very hard- 

 coated and will not germinate even if left in water for over a year. 



112 



