with a feltlike white to green tomentum. The tomentum, however, is neither as dense nor 

 resinous as in rubber rabbitbrush, Paulsen and Miller (1968) observed that Parry 

 rabbitbrush spread from underground roots. We have recently confirmed this phenomenon 

 in ssp. attenuatus. 



The glabrous to tomentulose, somewhat viscid leaves are narrowly linear to ellip- 

 tic, and range in size from 0.5 to 8 mm wide and 1 to 8 cm long. 



Flower heads usually are arranged in terminal leafy racemes (fig. 35) that some- 

 times form panicles. The involucral bracts are 9 to 14 mm high and terminate in acu- 

 minate to very attenuate herbaceous tips (fig. 36c) . The yellow, tubular to funnelform 

 corollas are 8 to 11 mm long. Achenes are 5 to 6 mm long and are covered with long, 

 shaggy, appressed hairs. Blooming occurs from July to September. Cleaned seeds 

 average 550 per gram (250,000 per pound). 



Hybridization. --Chrysothamnus parryi has 2n = 18 chromosomes (Anderson 1966, 1969, 

 1971). This species is composed of 10 subspecies, 6 of which occur in the Intermountain 

 region (Hall and Clements 1923). Among the Chrysothamnii, Chrysothamnus parryi is 

 probably most closely related to C. nauseosus with which it shares similarities in 

 pubescence, corolla, shape, and style-branches. In our fieldwork through Utah and 

 Nevada, we have found plants intermediate between C. nauseosus ssp. salioifotius and 

 C. parryi. Within the species, intermediate forms are known to occur between ssp. 

 parryi and howardi and between howardi and attenuatus (Hall and Clements 1923) . 



Distribution and habitat . --Parry rabbitbrush occurs in dry, open places in moun- 

 tains and foothills of western North America from Wyoming and western Nebraska west to 

 California and south to New Mexico and Arizona. Like other species of rabbitbrush, 

 this species tends to increase on overgrazed and disturbed areas. 



Z/se . --Although this species is generally palatable, it is not as widespread or 

 abundant as rubber rabbitbrush and low rabbitbrush and thus not as important for forage. 

 It is browsed mainly during periods of drought, particularly the more abundant subspe- 

 cies of attenuatus, howardij and parryi. Parry rabbitbrush has potential value for 

 stabilizing disturbed soils. We have observed several of its subspecies on readouts 

 and fills. 



Subspecies . --Chrysothamnus parryi ssp. asper is a low shrub 1.5 dm or more high 

 with slightly spreading to erect branches. Its green leaves, roughened with short- 

 stalked resin glands, are 2 to 5 cm long and 1 to 3 mm wide. The heads contain 5 to 10 

 disc flowers and are subtended by somewhat ranked involucral bracts with straight tips. 

 This subspecies occurs on mountainsides bordering desert areas from 2,100 to 2,600 

 meters (6,900 to 8,500 feet) in elevation in western Nevada and eastern California. 

 Its type locality is listed as "Hockett trail, in the valley of Little Cottonwood 

 Creek, eastern slope of the Sierra Nevada of Inyo Co., Cal." (Hall and Clements 1923). 



Chrysothamnus parryi ssp. attenuatus consists of low shrubs with mostly erect stems 

 up to 6 dm high. It has green, slightly viscid, narrowly linear leaves, 2 to 4 mm long 

 and about 1 mm wide (fig. 39b) . The leaves are erect but are not larger than the in- 

 florescence. Heads contain 5 to 7 disc flowers and are subtended by involucral bracts 

 with slender, straight tips. The bracts are ranked into 5 vertical rows. Blooming 

 occurs from August to October. Subspecies attenuatus is found in the sagebrush, pinyon- 

 juniper, and yellow pine vegetational types from southern Idaho to Nebraska and south 

 to New Mexico, Arizona, and California. Its type locality is listed as "Marysvale, 

 Utah, at 2,150 m in clay" (Hall and Clements 1923). We recently noted that this sub- 

 species will spread by adventitious shoots from underground roots. 



Chrysothamnus parryi ssp. howardi (Howard rabbitbrush) is a low shrub (fig. 35). 

 Its spreading basal stems and erect branches are up to 6 dm high (fig. 55). The nar- 

 rowly linear, tomentose leaves are 2 to 4 cm long, about 1 mm wide, and the upper ones 



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