Cal deeply 5-parted, the sep linear; cor tubular, bilabiate, the lips slightly spreading, much shorter than the tube, the upper shorter than the lower; stamens 4, inserted near the middle of the cor-tube and included in it; style shortly 2-lobed, the stigmas wedge-shaped; fr ovoid, septicidal; annual with opposite, pinnatifid lvs and small fls on axillary, solitary or paired, bractless pedicels. Monospecific.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.