Cal mostly 10-ribbed, with equal, firm, spinescent teeth; cor bilabiate, the upper lip entire, subgaleately rounded, the lower lip 3-lobed, and with a pair of prominent projections ("nipples") on the upper side near the base; stamens 4, ascending under the upper lip, the lower pair the longer; pollen-sacs set end to end, with a transverse line of contact, at the expanded summit of the filament, the proximal one with its back to the filament, the distal one surpassing the filament; each pollen-sac opening by 2 valves, the larger valve smooth and next to the filament, the smaller valve minutely bristly-ciliate and thrown back from the tip, remaining attached at the line of contact of the pollen-sacs; annuals with toothed or entire lvs, the small fls crowded in dense verticils in the upper axils. 10, temp. Eurasia.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.