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overlain by bench gravels of Pleistocene age 

 and by glaciofluvial alluvium on the broad 

 bottom lands. In the vicinity of Sula in the 

 upper Bitterroot River drainage, most of the 

 rock exposed near the drainage bottoms is 

 granitic; some pre-Cambrian sedimentary and 

 Tertiary volcanic rocks are exposed in places. 

 The bottom lands in this area are alluvium 

 (Alden 1953) . 



In Montana, populations of P. lemhiensis are 

 most often found on steep, east- to southwest- 

 facing slopes. A few sites have been found on 

 northeast- and northwest-facing slopes. In a 

 few locations (i.e., Trail Creek (002), Big 

 Hole Battlefield (006) ) , the populations occur 

 partially on level ground. For four sites 

 studied in Montana, Ramstetter (1983) found the 

 slopes to range from 20-45%. 



The recently verified sites in Montana range 

 from 1265 m (4,150 ft.) to 2470 m (8,100 ft.) 

 in elevation. 



In Montana, P. lemhiensis occurs in the 

 Beaverhead, Big Hole, Bitterroot, and Red Rock 

 river drainages. These areas are within 

 hydrologic unit numbers 10020002, 10020004, 

 17010205, and 10020001, respectively, as mapped 

 by the U.S. Geological Survey (1980) . 



5. Edaphic factors: Within appropriate habitat, 

 Penstemon lemhiensis prefers areas that are 

 more sparsely vegetated. The soils in these 

 microhabitats are often very gravelly. 

 However, the soil texture is highly variable; 

 P. lemhiensis has been found in soils ranging 

 from fine clay to sand (Ramstetter 1983) . 

 During the course of field surveys by the MTNHP 

 from 1986 to 1989, the species has been found 

 most often in soil areas characterized as 

 gravelly loams. 



Ramstetter (1983) obtained measurements of soil 

 moisture content from three sites at the Big 

 Hole National Battlefield population. The 

 percent water in soil (fresh-dry weight/dry 

 weight) ranged from 7 to 22 percent, at a soil 

 depth of 20 cm, on 2 July 1982. On 28 August 

 1982, these values ranged from 4 to 7 percent. 



Penstemon lemhiensis is not restricted to any 

 particular geological substrate; known sites 



