inflorescences are glabrous but viscid (sticky). The broadly linear to narrowly 

 lanceolate, bright green leaves are 1 to 5 mm wide, 2 to 5 cm long, and flat or twisted 

 (fig. 56d) . Leaf margins are sometimes scabrid. Crushed foliage usually emits a very 

 pungent odor. Branches of the cymes are glabrous. Involucral bracts are obtuse, oblong, 

 not keeled, and 5 to 7 mm long. Stickyleaf low rabbitbrush is widely distributed on dry 

 plains and hills from Washington, Idaho, and Montana south to Colorado, Utah, Nevada, 

 and eastern California. It occurs primarily in sagebrush and pinyon- juniper communities 

 at elevations between 1,520 and 2,600 meters (5,000 and 8,500 feet). This subspecies 

 often becomes dominant in cleared or overgrazed areas. At lower elevations stickyleaf 

 low rabbitbrush may be found associated with such halophytes as shadscale, winterfat, 

 and halogeton. Other subspecies of low rabbitbrush are also often associated with it. 

 Anderson (1971) recommends placing the former ssp. pwnilus in synonymy with C. visaidi- 

 florus ssp. visaidif torus because its specimens are "only environmentally modified 

 variants of C. v. ssp. visoidiflorus." Our chromatographic work (McArthur and others 

 1978) supports Anderson's reduction of pumilus to synonomy. 



Because of its wide distribution from moist to arid sites, the species is well 

 suited to a wide range of disturbed sites over the western States. 



CHARACTERISTICS OF THE GENUS TETRADYMIA (HORSEBRUSH) 



The genus Tetradymia consists of rather low, stiffly branched shrubs. The stems 

 are uniformly canescent or have glabrous to woolly streaks running down the stem inter- 

 nodes from the primary leaves. The tomentum may be permanent or deciduous on both the 

 stem and leaves. Spines may be present. 



Tetradynria bears primary and secondary leaves. Primary leaves develop alternately 

 along elongated shoots and are usually long-lived. These leaves are linear to spatulate 

 and may form slender, straight, or recurved spines. Secondary leaves develop in fas- 

 cicles in the axils of the primary leaves (fig. 59). They are generally short-lived 

 and often dry up and fall away within a few weeks (Strother 1974). 



}^orsebrush flowers are borne in heads located singly or in pairs in the upper 

 primary leaf or spine axils or are clustered in short, dense racemes or corymbs at the 



Figui -e 39. — Primary (A) 

 and secondary (B) leaves 

 on NuttalZ horsebrush 

 (7. nuttalliij. Speci- 

 men growing in Antelope 

 Valley, Sanpete Co., 

 Utah. 



58 



