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..
Herbs, mostly with pinnate leaves, but these sometimes with only 1 leaflet or 3, as in the following species, the umbellate or solitary, yellow, red or rose-colored flowers on bracted axillary peduncles. Calyx-teeth nearly equal. Petals free from the stamen-tube, the stamens diadelphous; standard ovate or suborbicular, wings oblong or obovate; keel incurved, mostly pointed or beaked. Pod linear, flattened or nearly terete, not stipitate. [In honor of David Hosack, 1769-1835 professor of botany and materia medica in Columbia College.]
About 50 species, natives of North America, all except L. Helleri Britton of North Carolina, and the following species, confined to the western part of the continent. Type species: Hosackia bicolor Dougl.
Trigonella americana Nutt. Gen. 2: 120. 1818. Lotus sericeus Pursh, Fl. Am. Sept. 489. 1814. Not DC. 1813. Hosackia Purshiana Benth. Bot. Reg. under pl. 1257. 1829. Lotus americanus Bisch. Litt. Ber. Linnaea 14: 132. 1840. Hosackia americana Piper, Contr. U. S. Nat. Herb. 11: 366. 1906.
Annual, erect, branched, villous-pubescent, or glabrate, 10'-20' high. Leaves 3-foliolate, or the upper sometimes 1-foliolate, sessile or the lower on petioles about 1" long; stipules minute or none; middle leaflet slightly longer-stalked than the lateral ones, oblong, the lateral lanceolate, rounded at the base, s"-8" long, 2"-3" wide; peduncles axillary, 1-flowered, 9"-12" long in fruit, leafy-bracted at the summit; flowers rose-color, about 2" long, the standard darker-veined; calyx-lobes linear, about twice the length of. the tube; pods straight, about 1' long, acute, glabrous, 4-7-seeded, deflexed.