Annual or perennial herbs. Leaves opposite to sub-opposite or sub-verti¬cillate, usually exstipulate. Flowers small, bisexual, regular, solitary or in cymose clusters. Sepals 5, free or united at the base, persistent. Petals absent; petaloid staminodes often present. Stamens 3-20, filaments free or united at the base, anthers bilocular, dehiscing longitudinally. Ovary superior, placentation axile. Fruit dry, membranous, dehiscing loculicidally by 3-5 valves. Seeds endospermic.