Astragalus collinus var. collinus

Bunchgrass prairies, grassy hillsides, and sagebrush valleys, in light sandy or stony soils overlying basalt, 900-3100 feet, forming colonies and locally abundant in central and southeastern transmontane Washington, extending southeast along the Snake River and its affluents from the south into westcentral Idaho and the north foothills of the Wallowa and Blue Mountains in Oregon, westward into Umatilla County; also apparently isolated on the upper Okanogan and lower Thompson Rivers in southern British Columbia.—Map No. 28.—May to July.

Astragalus collinus (Hook.) Don, Gen. Hist. Diehl. Pl. 2: 256. 1832, published independently of but exactly synonymous with Phaca collina (dwelling on hills) Hook., Fl. Bor.- Amer. 1: 141. 1831.—"On the subalpine range of the Blue Mountains, in dry soils...Douglas." —Holotypus, from "undulating and hilly grounds w. of the Rocky Mountains, in dry soils.," K! isotypi, BM, OXF!—Don’s specimen, formerly in herb. Lambert. (?), not located; he gives the locality as "North America, on the banks of the Columbia River."—Tragacantha collina (Hook.) O. Kze., Rev. Gen. 944. 1891. Homalobus collinus (Hook.) Rydb. in Bull. Torr. Club 40: 53. 1913.

Astragalus cyrtoides (convex, of the calyx, "bossed on the upper side like that of a Cuphea") Gray in Proc. Amer. Acad. 6: 201. 1864. "Clear Water River, interior of Oregon (now in Washington Territory [at present Idaho]), in rich land on hillsides, April 14, Rev. Mr. Spalding."—Holotypus, GH!

Within its area of dispersal the hill milk-vetch, A. collinus, is easily recognized by its greatly modified flower, remarkable for the tumid, basally pouched calyx of nearly the same color as the creamy petals, and for the relatively short, sigmoidally arched banner. The body of the pod is ordinarily straight, but is sometimes a trifle arched upward or downward. A noteworthy collection from Idaho County, Idaho, (Constance 1847, WS, WTU) combines a rather long, gently incurved pod with a developed banner, its limb recurved through about 50° rather than abruptly folded back a little below the apex. This may possibly represent a distinct race cut off from the main area of the species by the deeply dissected topography of the Salmon River canyon, but for the present too little evidence is available on which to base an opinion.