Annual or perennial herbs or shrubs. Leaves opposite, subulate, exstipulate. Flowers small, grouped in cymose spikes or panicles. Sepals 4, scarious-margined. Petals 4, entire or 2-dentate to 2-fid. Stamens (2-) 4-8; filaments inserted on a perigynous disk. Ovary 1-celled, 2-10-ovuled; styles 2. Capsule 2-seeded, 2-valved, compressed-lenticular. Seeds often 2, horseshoe-shaped.