This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Erect, or assurgent, nearly glabrous, much branched, densely dark-glandular, light green, 1°-2° high. Root not tuberous; petioles equalling or shorter than the leaves; stipules linear, 3"-4" long, early deciduous; leaflets 3, digitate, sessile, sometimes with a few scattered hairs, linear to oblanceolate, entire, varying from acute to obtuse or even emarginate at the apex, narrowed or cuneate at the base, 8" - 15" long, 3"-4" wide; peduncles slender; spikes dense, short, 4"-6" thick, 6-10-flowered; bracts membranous, caducous; flowers bluish-white, 3" long; corolla 2-3 times as long as the calyx; pod subglobose, about 2" long, sparingly pubescent, or glabrous, punctate; seed globose, brown.
In dry soil, Iowa to North Dakota, Saskatchewan, Kansas, Arizona and British Columbia. June-July.
Psoralea tenuiflora Pursh, Fl. Am. Sept. 475. 1814.
Erect, finely appressed-canescent, especially when young, punctate, much branched, slender, 2°-4° high. Root not tuberous; leaves short-petioled, digitately 3-5-foliolate; stipules subulate, 1"-2" long; leaflets very short-stalked, entire, oval, oblong or elliptic, 6"-10" long, 1 1/2"-3" wide, obtuse and mucronulate at the apex, narrowed or cuneate at the base; peduncles slender, longer than the leaves; racemes loosely 6-14-flowered, 1'-3' long; bracts scale-like, persistent; flowers purplish, 2" long; corolla about twice the length of the calyx; pod ovate, glabrous, punctate, 2'-3" long; seed ovoid, brown.
Psoralea obtusiloba T. & G., doubtfully recorded from Kansas in our first edition, is not definitely known within our area.
Stem 1°-4° high, profusely branching, canescent, not glandular. Petioles 2 1/2"-15" long, mostly shorter than the leaflets; stipules 1 1/2"-3 1/2" long, subulate, sometimes reflexed; leaves 3-5- sometimes 7-folio-late; leaflets 5"-18" long, 1 1/2"-4" wide, oblong, glandular on both surfaces, rugose, glabrous or with a few scattered hairs above, canescent with closely appressed white hairs beneath; peduncles 2'-7' long; spikes oblong or cylindric, usually many-flowered, the flowers about 4" long, at length interrupted and appearing almost as if whorled; bracts 1"-1 1/2 long, lanceolate, hirsute; calyx canescent, the lobes triangular, acute, the lower one the longest; pod ovoid, glabrous, light brown, covered with darker glands, beak short, stout, straight; seed 2 1/2" long, compressed.
Prairies, Illinois to Montana, Texas, Arizona and Mexico. Perhaps a large-flowered race of the preceding species. May-Oct. Scurvy-pea.