382 FOREST TREES OF THE PACIFIC SLOPE. 



Arizona (from White Mountain region to the Bill Williams (River) Fork) ; southern 

 California (Providence Mountains). 



OCCURRENCE. 



Low mountain slopes, foothills, and mesas in dry gravelly soils. In groups and scat- 

 tered among chaparral and occasional small desert trees. 



Climatic Conditions (marked by high temperature) and silvical habits, etc., unde- 

 termined. 



Family STERCULIACE^. 



Sterculiacere contains a large number of genera, but these are mainly 

 represented in tropical regions outside of the United States. The West 

 Indian tree, from which chocolate of commerce is derived, is a member of this 

 family, as is also the sycamore-leafed Sterculia, indigenous to China and so 

 often planted for ornament in the frostless. warmer parts of the United States. 

 One genus only, the following, belongs to this country. 



FREMONTODENDRON. 11 



The genus Fremontodendron is represented by only one species, which is con- 

 fined to California. The generic characters are included with those of its 

 species. 



Fremontia. 



Fremontodendron califomicum (Torr.) Coville. 



DISTINGUISHING CHARACTERISTICS. 



The commonest field name of Fremontodendron californictt/m is " slippery elm," 

 which refers to the mucilaginous tough bark and twigs. These taste like those 

 of the true slippery elm (Limits pubescens) of the East. It is also called 

 " silver oak," because of the white undersurface of its leaves, and " leather 1 

 wood," because of its tough twigs and bark. All of these names, however, were 

 used for eastern trees and shrubs long before they were applied to this Cali- 

 fornia tree. Fremontia is desirable to avoid confusion. 



Usually a small tree from 10 to 20 feet high, with a short trunk from 3 to 6 

 inches through and an open crown of wide-spreading limbs; occasionally some- 

 what taller and with a thicker trunk. Very often, however, it is a much 

 branched shrub, from 4 to feet high, forming dense thickets with other foot- 

 hill brush. The trunk bark is rough, deeply seamed, and blackish brown, some- 

 times reddish ; year-old twigs are smooth and pale reddish brown, and when 

 young are densely covered with rust-colored down. Mature leaves (fig. 180), 

 borne singly at a point on the twigs, are thick, veiny, rusty-downy beneath and 

 more or less hairy above. The leaves of each season's growth remain on the 

 twigs about two winters. Mature fruit (fig. 180), preceded by a bright yellow, 

 rose-like flower, is a densely woolly 4 or 5 celled capsule, splitting open at its 

 point when ripe in midsummer. The deep reddish brown small seeds are slowly 

 shaken from the open pods by the wind or browsing animals. Wood, deep, often 

 clear, reddish brown, fine-grained, dense, rather soft, cutting easily, and with a 

 very thick layer of whitish sapwood. Not used for any economic or domestic 

 purpose. Both tree and shrubby forms are of considerable service for the 

 tenacious protective cover they form on dry rocky foothill slopes. Range cattle 

 browse upon the twigs, which are very nutritious. 



° Formerly written Fremontia, a generic name recently found to have been preoccupied 

 for another group of plants, but which fortunately could be modified so as to retain its 

 dedicatory reference to General J. C. Fremont, through whose early western exploration* 

 the one species representing this genus was discovered. 



