Perennial herb, erect or prostrate, 30 - 40cm high. Stems green or purple, bristly,thickened at the nodes. Leaves opposite, subsessile, lanceolate oblong, denticulate,hirsute on both sides. Flowers white in axillary or terminal head; the female radiated,the bisexual in the centre. Achene 3 - angled, slightly flattened (Vietnam)