and spreading, the whole forming a rather open, rounded clump 4 

 to 8 feet high and often much broader than tall. This species is 

 very variable in foliage, fairly distinctive leaf forms having been 

 developed in various climatic areas. 1 Although some authors con- 

 sider these forms to be of specific rank, more conservative botanists 

 prefer to recognize them simply as varieties or forms of R. calif or- 

 nica. The fact that the forage utilities of these variations are similar 

 is an additional argument for adhering to the more conservative 

 nomenclatural viewpoint in this treatment. 



California buckthorn inhabits foothills and mountain slopes from 

 southern Oregon to southern California. It is most characteristic, 

 common, and abundant in the foothill or lower montane areas at ele- 

 vations ranging from 1,000 to 3,000 feet, though it frequently de- 

 scends to near sea level in the valleys or occurs up to 5,000 feet in the 

 Sierras. This shrub is a common component of the foothill woodland 

 chaparral, where it is usually associated with whiteleaf manzanita 

 (Arctostaphylos viscida) and wedgeleaf ceanothus (Ceanothus 

 cimeatus). Like these and other chaparral species, California buck- 

 thorn inhabits warm and dry sites, usually on southern exposures 

 where the soil, generally, is stony, only moderately fertile, and fre- 

 quently rather shallow. Although very common, this shrub seldom 

 grows in a pure stand, nearly always occurring as large, shrubby 

 individuals, especially in the small openings in the chaparral. The 

 plant is difficult to destroy, especially by fire, as it sprouts freely, the 

 seeds are long-lived, and heat facilitates their germination. 



California buckthorn, important chiefly because of its commonness 

 on many ranges, apparently contributes very little to the grazing 

 capacity. Its evergreen leaves are leathery and tough ; the twigs and 

 bark are acrid and bitter. On closely grazed or on winter ranges, 

 sheep and goats pick at the foliage but, under more average condi- 

 tions, the species is usually so unpalatable that it is not used even by 

 goats. The species has local value as ground cover for watershed 

 protection, doubtless serves as a covert for deer, and its edible, juicy 

 fruit is eaten by birds. 



BUCKTHORNS 



Kham'nus spp. 



The buckthorns compose a genus of about 100 species, rather 

 widely distributed throughout the temperate and warm climates of 

 the world, especially of the Northern Hemisphere. The buckthorn 

 family (Rhamnaceae), which takes its name from this genus, con- 

 tains several other genera, of which the various species of Ceanothm 

 are the best known and most valuable from a western range stand- 

 point. The Old World jujube (Zizyphus jujuba, syn. Z. vulgaris). 

 cultivated for its edible fruits, is also a member of this family. The 

 origin of the common name buckthorn is rather obscure. It may 

 have arisen in Europe, where some of the species are thorny and 

 provide shelter for the male deer, or buck, or it may be a distortion 



1 Jepson, W. L. A MANUAL OF THE FLOWERING PLANTS OF CALIFORNIA. 1.238 pp.. illus. 

 Berkeley, Calif. [1925.] 



