Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Much like Orbexilum, but the lvs digitately 3–5-foliolate, or the upper 1-foliolate; cal-tube gibbous at base on the upper side; standard broadly oblanceolate to obovate or suborbicular; fr opening by transverse rupture, not strongly cross-ribbed; x=11. (Often included in Psoralea) 21, N. Amer.