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 upper 2 lobes connate for all or most of their length, the lower 3 separate; standard oblong to suborbicular, narrowed at base; wings oblong; keel nearly straight; stamens 10, usually diadelphous; fr indehiscent, stipitate, transversely segmented and eventually separating into 1-seeded joints (articles), ± beset with hooked hairs; ours all perennial herbs with ± petioled (rarely subsessile), pinnately 3-foliolate lvs and purple or pink or less often white fls in elongate racemes or panicles. (Meibomia.) 300, mainly warm reg.