Erect annual 1-2 dm, the finely hairy stems usually branched at base; lvs obovate-oblong to elliptic, 6-12 mm, entire or with a few low teeth, scabrous, on petioles 1-2 mm; fls 1-3 in each upper axil; pedicels 2-4 mm; cal 5-6 mm, very gibbous beneath, constricted at the throat, hirsutulous on the ribs, the lips about equal and half as long as the tube, the lower lip bifid to the base, the upper widened to the summit and subtruncate, with 3 small teeth 0.5 mm; cor pale purple, 7-10 mm; 2n=18. Native of Europe, intr. as a weed of roadsides and waste places from N. Engl. to Wis. and N.J. June-Sept. (Acinos arvensis)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.