Vicia americana Muhl.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Trailing or climbing perennial to 1 m; stipules all or mostly sharply serrate; lfls usually 4–8 pairs, 1.5–3 cm; racemes shorter than the subtending lvs, loose, with 2–9 blue-purple fls 15–27 mm; cal-tube very oblique, 3.5–5.5 mm, the upper lobes to 1 mm, the lower 1.2–3 mm; fr 2.5–3.5 cm; 2n=14, 28. Moist woods; c. N.Y. and s. Ont., s. in the mts. to w. Va., w. to Minn. and Mo., and widely distributed in w. N. Amer. May–July. Most of our plants are the widespread var. americana, with elliptic or oblong lfls 5–12 mm wide, the mucronate summit otherwise obtuse to broadly rounded, the numerous lateral veins leaving the midrib at an angle of about 45 degrees and branching and anastomosing before reaching the margin. The var. minor Hook. (var. angustifolia, V. sparsifolia) grows chiefly on the Great Plains and westward, but sometimes occurs within our western border; it has thick, narrow, densely puberulent lfls with prominent, essentially unbranched lateral veins that leave the midrib at a very narrow angle. Occasional plants in our range with truncate or emarginate lfls sharply toothed toward the summit, otherwise like var. americana, resemble or actually represent the otherwise chiefly cordilleran var. truncata (Nutt.) Brewer. (V. truncata)