Distribution and Habitat •~~Chrysothamnus vaseyi occurs scattered over plains, hill- 

 sides, and mountain valleys at altitudes of 1,700 to 2,600 meters (5,600 to 8,500 feet) 

 in Utah, Wyoming, Colorado, New Mexico, and Arizona [Hall and Clements 19^3). 



Use . --This shrub is probably browsed by sheep, but is small and so scattered it is 

 of little value. 



Chrysothamnus Viscidiflorus (Hook.) Nutt. (low rabbitbrush^) 



Low rabbitbrush varies in appearance and foliage characteristics. It is usually 

 3 dm to 1 m tall with many erect stems branching from a simple base. The brittle, 

 erect twigs are glabrous or puberulent with pale green or white bark. 



Leaves are narrowly linear to oblong or lanceolate, 1 to 6 cm long and often 

 twisted. Leaf vestiture is glabrous or pubescent and commonly viscidulous with 

 usually scabrous margins. Degree of pubescence may vary tremendously in variants of 

 this species. As Hall and Clements (1923) pointed out, sometimes the pubescence 

 among the subspecies of viscidiflorus "will occur as a fairly dense though minute 

 puberulence in certain plants, while others almost exactly duplicating these in every 

 other respect will be perfectly glabrous." Furthermore, L. C. Anderson (letter 

 3/30/76) has observed good correlation between plant stature and leaf size of ssp. 

 viscidiflorus and lanceolatus with altitude and amount of precipitation. 



Flower heads containing approximately 5 perfect, fertile disc flowers each are 

 arranged in compact terminal cymes. Involucral bracts number about 15 per head and 

 are arranged in poorly to well defined vertical ranks. The bracts of some subspecies 

 have a greenish or brownish thickened spot near their apex. Low rabbitbrush averages 

 about 1,725 cleaned seeds per gram (782,000 per pound) (Plummer and others 1968). 



Hybridization. --Chrysothamnus viscidiflorus is the center of a polyploid species 

 complex with a basic chromosome number of = 9. Diploid (2n = 18), triploid (2n = 27), 

 tetraploid (2n = 36), pentaploid (2n = 45), and hexaploid (2n = 54) populations of this 

 species are known to occur (Anderson 1966, 1971; Anderson and others 1974). 



This species includes numerous subspecies and ecotypes within subspecies. Most 

 important among these in the Great Basin are 2 glabrous subspecies, viscidiflorus and 

 stenophyllus , and 2 pubescent subspecies, lanceolatus and puberulus (fig. 56). Hall 

 and Clements (1923) believe numerous intergrades have been held together in one rather 

 close species through interbreeding where their ranges meet or overlap. Abrams and 

 Ferris (1960) describe C. viscidiflorus as a highly polymorphic species composed of 

 several freely intergrading subspecies of overlapping distribution. We invariably find 

 intermediates when doing fieldwork on this species. We believe forms of low rabbitbrush 

 may be improved for grazing and other uses through selection and breeding. Because each 

 subspecies is self-fertile and predominately self-pollinated, each maintains its iden- 

 tity despite occasional outcrossing (McArthur and others 1978). 



Distribution and habitat . --lovi rabbitbrush is one of the most widely distributed 

 shrubs on rangelands throughout western North America. It occurs in dry, open areas 

 from British Columbia and North Dakota, south to New Mexico, Arizona, and eastern 

 California at elevations between 790 and 3,350 meters (2,600 and 11,000 feet). Low 

 rabbitbrush is usually associated with sagebrush, snakeweed iXanthocephalum) , and other 

 species of rabbitbrush. 



70ther common names include yellowbrush, yellow rabbitbrush, yellowsage, rabbitsage, 

 sticky-leaved rabbitbrush, and Douglas rabbitbrush. 



54 



