Cal campanulate, sometimes slightly oblique at base, but not gibbous, its lobes equal or the lower (especially the median one) the longest; standard obovate to rotund, usually clawed at base; wings about equaling the standard but longer than the keel; stamens 10(9), usually diadelphous, the upper median filament wholly or mostly free (or suppressed); ovule normally 1; fr short, ±flattened, indehiscent, in ours strongly cross-wrinkled and exserted from the cal; usually ±glandular-punctate herbs with pinnately 3-foliolate lvs, the terminal lfl long-stalked; fls in long-peduncled axillary spikes or racemes, usually blue; x=11. (Often included in Psoralea) 8, N. Amer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.