Perennial variously aromatic herbs of damp or wet places. Stems erect or ascending from a creeping rhizome, glabrous or with simple hairs (in ours), leafy, branched or not. Leaves undivided, serrate or dentate, usually with younger leaves in axils, shortly petiolate or sessile, villous to glabrous, ± gland-dotted abaxially. Flowers borne in many-flowered verticillasters either in axils of upper leaves or in continuous or interrupted spikes of verticillasters subtended by bracts; flowers frequently unisexual and gynodioecious, sometimes gynomonoecious. Calyx small, slightly bilabiate or regular with 5 subequal teeth, tubular-campanulate, 10-13-veined; tube glabrous or villous at throat. Corolla weakly bilabiate, small, with 4 subequal lobes, uppermost slightly larger; tube included within calyx. Stamens 4, subequal and, when fertile, clearly exserted beyond corolla lobes; thecae bilocular, parallel. Style subequally bifid. Nutlets small, ovoid or globose, not trigonous, rounded, smooth or clearly reticulate, mucilaginous on wetting or not.