Semi-parasitic annual or perennial herbs or subshrubs; rootlets often connected to those of other plants by nodule-like swellings (haustoria). Leaves opposite and decussate, serrate, pinnatifid or crenate; lower surface with sessile glands. Inflorescences terminal spike-like racemes; bracts leaf-like. Calyx 4-lobed, median clefts longer or equal to the lateral clefts; corolla 2-lipped, upper lip hooded, with 2 recurved lobes, lower lip with 3 spreading lobes; stamens 4, in pairs of unequal length, anthers forming a U-shaped configuration by fusion along the margins, dehiscing by eglandular hair-lined slits, filaments attached on the outer face, bases of cells attenuated into a rigid awn; ovary 2-locular; stigma unequally 2-lobed. Capsule loculicidal; seeds many, obliquely ellipsoid, longitudinally ribbed, with trabeculate connecting ribs.
About 200 species, from temperate regions of both Hemispheres, extending into the tropics in Malaysia; c. 20 species in Australia.