Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Cal bilabiate, the tube campanulate, oblique, the upper 2 lobes united part-way; pet usually acute, the standard oblong-obovate, tapering to the base, the wings and keel shorter, oblong, clawed; stamens 10, diadelphous for about half their length; anthers alternately large and small; ovary cylindric; style smooth, nearly straight; fr indehiscent or only tardily dehiscent, slightly flattened to somewhat inflated, glandular or spiny, few-seeded; gland-dotted perennial herbs with odd-pinnate lvs and dense axillary racemes of white, yellow, or blue fls. 20, ± cosmop.