Prostrate annual or perennial herbs. Leaves opposite, exstipulate. Flowers bisexual, in axillary globose clusters, sub-sessile, regular. Calyx tube 5-lobed; lobes with membranous margin, mucronate. Stamens 5-15, free. Ovary bilocular; styles 2, free. Capsule 4-seeded, dehiscence operculate, the valves separating longitudinally.