Perennial rhizomatous herbs; branches quadrangular and grooved; hairs simple. Leaves sessile to shortly petiolate, decussate, simple, coarsely toothed to lobed. Inflorescence of sessile few-many-flowered cymes forming dense clusters in axes of upper leaves. Calyx 5-lobed, lobes equal, acute; corolla slightly zygomorphic, not 2-lipped, lower lobe broad and entire, lateral lobes narrower, and upper lobe broad and slightly 2-lobed; upper pair of stamens sterile, anthers with both locules fertile, locules slightly divergent. Mericarps 3-angled to 3-keeled.
About 14 species, chiefly from temperate regions of the Northern Hemisphere; 1 species native to Australia.