quite ripe) + 4.2-4.5 mm. long (adapted from 

 Barneby 1964) . 



3. LOCAL FIELD CHARACTERS: Astragalus molybdenus is 

 only positively identified in fruit. It is 

 distinguished from other co-occurring Astragalus 

 species by its small, distinctly three-angled 

 (making it appear slightly inflated) , curved 

 fruits, and leaflets, which have hairs only along 

 their margins and dorsal surfaces. 



Vegetatively , Astragalus molybdenus is similar to, 

 and co-occurs (in Montana) with, A. bourgovii , A. 

 alpinus , and A. vexillif lexus . Fruits of A. 

 vexillif lexus are curved, and resemble those of A. 

 molybdenus , but are not three-angled (appearing 

 flat in side view) . The fruits of A. bourgovii 

 and A. alpinus are only gently curved, and not 

 distinctly three-angled. 



Other useful (but not definitive) characteristics 

 in the vegetative state include the yellow-green 

 stems of A. molybdenus (A. vexillif lexus has 

 distinctly reddish stems) , and the presence of 

 minute hairs only along the margins and dorsal 

 side of the leaflets (A. bourgovii and A. alpinus 

 both have minute hairs that extend onto the 

 adaxial side of the leaflets) . 



GEOGRAPHICAL DISTRIBUTION 



1. RANGE: In Montana, A. molybdenus is currently 

 known from eight populations in the Sawtooth 

 Range, Teton County, near' the headwaters of the 

 North and South Forks of the Teton River. The 

 locations are included in Figure 1, p. 6. These 

 populations occur within 10 air miles of one 

 another (U.S.G.S. 7.5' topographic maps: Our Lake 

 and Mt. Wright) . The Montana populations are 

 disjunct from populations in Colorado by nearly 

 960 km (600 mi). Limestone substrates are common 

 in the Sawtooth Range, and extensive areas of 

 potential habitat exist for some miles to the 

 north and south of these populations. There was 

 not enough time to thoroughly survey all the 

 potential habitat for this species. 



The distribution of population centers of 

 Astragalus molybdenus in Montana and Colorado, and 

 A. shultziorum in Wyoming, is shown in Figure 2, p 

 7. 



