Cal 4-lobed (the upper median lobe lacking), more deeply cleft above and below than on the sides; cor bilabiate, the upper lip concave, shallowly 2-lobed or merely notched, its sides often reflexed or revolute, the lower lip spreading, 3- lobed, the lobes often emarginate; stamens 4, included, ascending under the upper lip; pollen- sacs acuminate or mucronate at base; ovary laterally compressed; style elongate; stigma capitellate; fr loculicidal, truncate or retuse above; seeds several, fusiform, with ca 10 narrow wings; low, hemiparasitic herbs, ours all annuals with small, thinly retrorse-hairy stem and opposite, sessile, ovate to rotund, palmately veined, coarsely toothed lvs, the upper bracteal lvs similar but tending to be alternate; fls small, sessile or subsessile. Hundreds of described spp., only a few reasonably distinct; irregularly widespread.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
