site are Atriplex gardneri, Agropyron smithii, and Haplopappus 

 uniflora. The site has been grazed. 



D. POPULATION BIOLOGY 



The occurrence is small, consisting of about one hundred 

 plants covering a single acre. 



E. MANAGEMENT CONCERNS 



S. argentea is a narrow endemic which is rare in Montana with 

 just three known sites, all in Beaverhead County. Recently 

 located populations have been small. In the study area the 

 species was associated with an unusual plant community, and 

 although there may be other unmapped subpopulations in the 

 vicinity, it is unlikely that this species is common. The 

 plant is low to the ground and not likely harmed by livestock 

 grazing; nonetheless, the rarity of this species is basis for 

 recommending that it be considered for ELM sensitive species 

 designation. 



Sphaeromeria capitata Nutt. 

 Rock-tansy 



A. DESCRIPTION 



1. General description: This is similar to S. argentea (see 

 previous synopsis) . The deeply lobed leaves are mostly at the 

 woody base of the plant and form dense cushions over rocks. 

 The inflorescence is a tight, spherical cluster of heads of 

 yellow, tubular flowers which lack pappuses. 



2. Diagnostic characters: S. capitata differs from S. 

 nuttallii by having more dense clusters of flower heads and 

 more deeply lobed leaves. 



B. GEOGRAPHIC DISTRIBUTION 



1. Species range: Wyoming and Montana (Hitchcock and Cronquist 

 1973) . 



2. Montana distribution: Carbon and Beaverhead Counties. 



3. Occurrences in the study area: One population was surveyed 

 in the foothills just south of Clark Canyon Reservoir in the 

 northernmost part of the range. Lesica found it to be common 

 in this vicinity and it was also seen by Vanderhorst just 

 south of Bell Canyon. 



C. HABITAT 



Plants grow in cracks and form dense cushions on mostly barren 

 limestone pavement. Other plants in this habitat were 

 Erigeron compositus, Haplopappus acaulis, and Petrophyton 

 caespitosum. 



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