Parasitic on many hosts, especially Trifolium; plants 1.5-5 dm, strict and simple from a ±bulbous-thickened base, ±glandular-villous; infl spicate, ±elongate, not very dense, especially below, the axis exposed; fls sessile, subtended by a bract but without bractlets; cal split to the base above and below, the 2 lateral segments slender and elongate, mostly bifurcate, commonly unequally so, the lower fork the smaller; cor white or yellowish, marked with violet, 10-15 mm; 2n=38. Native of Europe and w. Asia, intr. from N.J. to N.C.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.