Medicago sativa L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Deep-rooted perennial with slender stems to 1 m; stipules lance-ovate, toothed; lfls oblanceolate or oblong to narrowly obovate, 1.5–3 cm, toothed at the summit; peduncles erect, about equaling the subtending lvs; heads subglobose to short-cylindric; fls 6–12 mm, on pedicels 2–3 mm; cal-lobes lance-linear, 1–3 mm, about equaling the tube; pod finely hairy; 2n=16, 32. June–Sept. A highly diversified species, with pronounced but confluent variation. The two subspecies characterized below are connected by a hybrid swarm called ssp. ×varia (Martyn) Arcang. Additional variants may be characterized in more detailed treatments.