Much like no. 1 [Apios americana Medik.], the tubers fewer and larger; fls greenish-white, suffused with rose toward the tip, 17-22 mm; standard terminating in a spongy protuberance 4 mm. Rocky woods; Ill., Ky., and reputedly Tenn. Aug. Rare and little-known.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.