Small annual or perennial, diffusely branched herbs with prostrate rarely ascending stem. Leaves opposite to subopposite, subsessile to petiolate, ochrea tubular or 2-partite. Flowers in terminal, axillary clusters or heads, sessile to pedicellate. Perianth 3-5 cleft, sepaloid, outer 2 tepals usually small. Stamens 2-5 alternating with staminodes, filaments usually short. Pollen grains tri-pantoporate, spinulose. Stigmas 2-3, ± rounded, styles 2-3, short, ovary orbicular-trigonous. Nut small, trigonous, biconvex or subcompressed; inserted or rarely exserted.