Psoralea argophylla Pursh

Psoralidium argophyllum (Pursh) Rydberg
Psoralea argophylla Pursh, Fl. Am. Sept. 475. 1814.
Psoralea incana Nutt. (Fraser, Cat.; hyponym. 1813) Gen. 2: 102. 1818.
Psoralea argophylla decumbens A. Gray. Pacif. R. R. Rep. 12 ! : 41. 1860.
Lotodes argophyllum Kuntze, Rev. Gen. 194. 1891.
Psoralea argophylla robustior Bates, Am. Bot. 20: 16. 1914. A perennial, with a rootstock; stem erect, 3-5 dm. high, silvery -canescent. divaricately branched; leaves digitately 3-5-foliolate; stipules 5-10 mm. long, lanceolate; petioles 2-5 cm. long; leaflets 1.5-4 cm. long, 5-20 mm. broad, elliptic to broadly obovate, obtuse, often mucronate, more or less silky on both sides, usually silvery-white beneath; peduncles 3-8 cm. long; spikes interrupted, 2-4 cm. long; bracts ovate-lanceolate, 5-10 mm. long, longacuminate; flowers 2-4 at each node; calyx densely white-silky; tube about 2 mm. long, campanulate; upper four lobes lanceolate, acute, about 3 mm. long, the lowest lobe lanceolate, long-acuminate, 6-7 mm. or in fruit more than 1 cm. long; corolla dark-blue or purple, 8-9 mm. long; banner broadly obovate; pod ovoid, densely silky, 7-8 mm. long, with a flat straight beak; seed brown, oval, compressed, 4 mm. long.
Type locality: Banks of the Missouri [Dakota].
Distribution: Wisconsin to Saskatchewan, Wyoming, New Mexico, and Missouri.