Ascending annual to 6 dm; lfls 3-7 pairs, 1-2 cm; fls usually paired (-4) in the upper axils, 25-35 mm, dull yellow in aspect, or the standard marked with violet, the keel commonly dark purple; cal-tube 6-9 mm, the linear-subulate subequal lobes half to two- thirds as long; style with a conspicuous tuft of hairs just behind the tip on the outer (abaxial) side, glabrous on the other side; 2n=14. Native of sw. Europe and w. Asia, occasionally intr. in our range from N.Y. to Va. and Ky., and in se. U.S.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.