oblong) (Bameby 1964). The duplicate of the annotated specimen at MONTU (Herbarium at U. of 

 Montana) has calyx 1 2 mm long with teeth 7 mm long. A collection from Fallon County, Montana 

 (Lesica #4280) has calyx 8 mm long with teeth 3 mm long. Our collections from Carter County 

 (Vanderhorst 5695, 5713) have relatively short calyces (about 8 mm) and teeth (3-5 mm), but 

 relatively broad basal leaflets. Plants intermediate between the two varieties are reported from 

 Colorado, Kansas, and Nebraska (Great Plains Flora Association 1 986). Further collecting and 

 consultation will be required to determine which variety or varieties occur in Montana. 



GEOGRAPHICAL DISTRIBUTION 



Global distribution: Great Plains; Astragalus racemosus var. longisetus is found in the 

 western Great Plains in southwest South Dakota, northwest Nebraska, eastern Colorado and 

 eastern New Mexico (Great Plains Flora Association 1 986), eastern Wyoming (Dom 1 992), 

 and eastern Montana. Note: The nominate variety has a broader and sometimes sympatric 

 distribution (Bameby 1 964), from western Minnesota to southern Saskatchewan south to the 

 Texas panhandle (Great Plains Flora Association 1 986). 



Montana distribution: Carter and Fallon counties. 



Carter County distribution: Prior to this study 

 raceme milkvetch was known by one 1938 

 collection with uncertain location data and, more 

 recently, from one location on state land along 

 Highway 212 east of Hammond. In 1997, five 

 populations were found on BLM land and an 

 additional population was found along the roadside 

 on private land. These occurrences are scattered 

 across the southern half of the county, and there is 

 a possibility that the range extends north along the 

 Powder River breaks. 



Astragalus racemosus 



PtOBtam May 1998 



HABITAT: Raceme milkvetch is confined to and is an indicator of selenium soils (Great Plains 

 Flora Association 1986). It usually grows on "gumbo"; usually in "low sites with an abundance of 

 alkali" (Barr 1983). These soils with high selenium content are found locally on substrates derived 

 from marine shales. Another selenium indicator, prince's plume {Stanleya pinnata), grows in the 

 same habitat at two Carter County sites. Vegetation of the sites varies from grasslands to sagebrush 

 steppe and greasewood communities. The largest known population with the most robust plants 

 occurs on gentle slopes of a low relief shale ridge with an excellent quality upland Elymus 

 lanceolatus/Stipa viridula (ELYLAN/STIVIR) grassland with eroded scabby patches supporting 

 Eriogonum pauciflorum (ERIPAU) communities. This stand has among the highest diversity of 

 forbs observed in Carter County. In contrast, high population numbers were also found in Stipa 

 comata/Carex filifolia (STICOM/CARFIL) grassland. This population is on the edge of the contact 

 zone between sandstone and shale substrate parent materials and is a meeting and mingling of 

 dominance by wheatgrass {Elymus lanceolatus and/or Pascopyrum. smithii) on shale and 

 STICOM/CARFIL on sandstone. In the breaklands at the southeastern comer of the County 

 (Wymonkota) a few plants were also found near the contact zone of sandstone and shale outcrops 



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