Annual, diffused or creeping, branched, glabrous or pubescent herb; stems 4-angled; leaves opposite, simple, ovate-lanceolate, acuminate at apex, subcordate at base, crenate to serrate or entire, scabrous, shortly petioled; flowers small, ebracteate, axillary, solitary or subumbellate racemes; calyx tubular, 3-5 plaited, 2-lipped, 3-5 toothed, lobes lanceolate, acuminate, narrowly oblong, keeled, hardly winged, base deccurent; corolla showy, upper lip erect, purple, oblong-orbicular, erect, concave, notched or bifid; lower lip larger, bluish-purple, throat pale or white, 3-lobed, spreading, tube cylindric, dilated above; stamens 4, upper-2 included, lower appendaged at the base and conniving under upper lip, anthers cohering in pairs, cells often confluent, stigma-2, lamellate, style slender; ovary glabrous; capsules linear to oblong, septicidal, valves separating from flat, placentiferous axis; seeds many, rugose.