1. FEDERAL STATUS: Cirsium longistylum is on the Watch 

 List for Region 1 of the U.S. Forest Service. Under 

 the Endangered Species Act (U.S. Dept. of Interior 

 1990), administered by the U.S. Fish and Wildlife 

 Service, this species is categorized as C2, ("current 

 information indicates that proposing to list as 

 endangered or threatened is possibly appropriate, but 

 substantial biological information is not on file to 

 support an immediate ruling") . 



2. STATE: Cirsium longistylum has most recently been 

 ranked by the Montana Natural Heritage Program as an S2 

 species ("imperiled in Montana because of rarity (6-2 

 occurrences)" (Shelly 1990). Although only 20 

 populations of C. longistylum are currently recorded, 

 several contain tens of thousands of individuals and 

 numerous other populations were observed that were not 

 recorded. Thus, the rank will be changed to S3 on the 

 1991 list of Plant Species of Special Concern. 



C. DESCRIPTION 



1. GENERAL NON-TECHNICAL DESCRIPTION: Cirsium longistylum 

 is a perennial thistle from thick, woody underground 

 stems. The stems are 20-24 inches tall, ribbed, and 

 are lightly hairy with long, cobwebby hairs. The basal 

 rosette leaves are somewhat spiny, shallowly lobed, and 

 are green, hairless above and densely white hairy 

 below. The stem leaves are gray-green with long white 

 cobwebby hairs, narrowly spear-shaped, about 10 times 

 as long as wide (up to 6 inches long and 0.5 inch 

 wide) , with lobes about 1/3 the width. Smaller leaves 

 are only shallowly lobed with numerous fine marginal 

 spines to 0.2 inch long. The flower heads are about 

 1.2 inches high and 1 inch wide, usually in a tight 

 cluster in the top 2/3 of the plant. In young plants, 

 the upper part of the stem may be unexpanded and the 

 flowers clustered at the top of the stem. The flower 

 heads have a few small leaves beneath, the uppermost 

 resemble the involucral (outer, subtending) bracts of 

 the flower in shape. The involucre is 0.8 inch high 

 with the outer bracts narrowly spear-shaped, 0.06-0.08 

 inch wide at the base, with a few glands or a dark 

 blotch, the tip is slightly wider and has a slender 

 0.08 inch spine. The middle and inner involucral 

 bracts are progressively less widened at the tip. 

 Flowers are white, the petals 0.8-0.9 inch long with a 

 basal ring of 30-40 tawny hairs 0.70-0.75 inch long. 

 The anthers are 0.30-0.35 inch long. The style extends 

 to 0.4 inch beyond the corolla tube. The seeds are 

 0.22-0.26 inch long and 0.08 inch wide, light brown and 



