We conducted our surveys by walking through an area, moving between canyon 

 bottoms and ridges as much as possible. The study area is large and could not be 

 surveyed entirely and evenly during the time allotted. Thus, we chose to stratify our 

 surveys, giving preference to areas with high topographic and edaphic diversity (Gillison 

 and Brewer 1985). We concentrated our efforts .south of the Pryor Mountains in the 

 drainage of the Bighorn River (townships 25, 26, 27, 28). This area is highly dissected 

 with many different soil types. The area west of the mountains in the drainage of the 

 Clarks Fork of the Yellowstone River is a series of parallel valleys with sandy clay and 

 silty soils. We surveyed portions of many of these valleys and found them relatively 

 homogeneous. Most areas were visited only once during the study; however, we did 

 return to areas with exceptional diversity. A map showing the locations of our sur\'eys is 

 in Figure 2. 



We located populations of target species on USGS 7.5' topographic maps and 

 recorded the dominant plant species in the immediate area for each population. We 

 used the "feel" method to determine the textural class of the soil (Brady 1974). We also 

 estimated the density of target species plants in 0.5-hectare plots by assigning them into 

 one of three classes: (1) MOO, (2) 101-1000, and (3) >1000. In this way we obtained 

 estimates of density, soil texture, elevation and vegetation for each population. We 

 recorded only one population of each target species in each quarter-section. 



RESULTS 



We searched for and recorded information on 35 species of rare plants that were 

 previously known from the Pryor Mountain Desert area. In addition, we discovered six 

 rare species previously unknown from the area, including four species not previously 

 known from Montana. One species, Eriogonum lagopus , is a candidate for listing as a 

 threatened or endangered species by the U.S. Fish and Wildlife Service. A list of these 

 species is provided in Table 1. A list of all vascular plant species encountered in the 

 study area is in Appendix A. We located populations of all but one of the rare species 

 that had previously been found in the area. Although we examined many specimens of 

 Delphinium in the field, we were unable to locate any populations of D. geyeri. 



Distribution maps for each species are in Appendix B. Information on location, 

 elevation, vegetation, soil texture and plant density for each population of each species is 

 in Appendix C. The results of our surveys are summarized by species in the following 

 section. The Natural Heritage Program status for each species reflects the most current 

 knowledge, including the results of this survey. The Montana status is taken from Lesica 

 and Shelly (1991) and does not reflect the results of this study. 



