Monographs Details: Astragalus serenoi var. sordescens Barneby
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
Description:Variety Description - More slender than var. Serenoi, the stems 1.5-3 dm. long; leaves 2-10 cm. long; peduncles 3-10 cm. long; racemes 5-15-flowered, the axis 2-7 (10) cm. long in fruit; calyx 7.9-10.2 mm. long, the teeth 1.5-2.5 mm. long; flowers shorter and with narower petals, the banner 14.5-16 mm. long, 6.4-8 mm. wide, 13.5-14.8 mm. long, the claws 7.2-7.8 mm., the blades 7-7.7 mm. wide; keel 12.7-14 mm. long, the claws 7.2-8.4 mm., the blades 6-6.4 mm. long, 2.5-2.7 mm. wide; pod 1.5-2.2 cm. long, 5-7 mm. in diameter, somewhat incurved, subunilocular, the septum not over 0.5 mm. wide; seeds ochraceous, minutely purple-speckled, lustrous but sparsely pitted, 2.4-3 mm. long.

Distribution and Ecology - Gentle slopes and flats, among and often sheltering under or scrambling up through low sagebrush, 5000-6800 feet, known only from northcentral Nye County (south of Belmont; 35 miles northeast of Warm Springs), Nevada.—Map No. 68.—May to July.

Discussion:The flower of var. sordescens is smaller and narrower than that of the typical naked milk-vetch, and tawny yellow except for the sordidly purplish wing- and keel-tips and the purplish veining of the banner. I first ascribed it (l.c.) to A. Shockleyi, known at the time only from fruiting material, and the true differential characters were not appreciated until much later. I may have been influenced in my misidentification by the proximity to var. sordescens of a Fish Lake Valley suggestive of the type-station of A. Shockleyi, although I have since learned from the label of a topotypus (Shockley 527, NA, NY) that this was actually in Esmeralda County. The comparatively short, shortly pedunculate racemes and small, obliquely ovoid, subunilocular fruit provide further means, for the present, of distinguishing var. sordescens; although one may question whether the differential characters will be found consistently correlated as more populations are studied.
Distribution:Nevada United States of America North America|