Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Cal regular, deeply 5-cleft; standard orbicular; wings obovate-oblong, two-thirds as long as the standard; keel usually beaked and upcurved; stamens 10, monadelphous into a closed tube, the filaments alternately long and short; pod small, oblong or ovate, few–seeded, subtended or enclosed by the persistent cal; herbs or shrubs with stipules adnate to the petiole, serrate lfls, and solitary or paired axillary fls. 75, mainly Mediterranean.