Perennial or annual herbs, hygrophilous, glabrescent to tomentose. Upper leaves alternate. Inflorescence a terminal spike or spicate. Flowers usually trimorphically heterostylous, usually 6-merous. Hypanthium tubular, ribbed. Epicalyx present. Petals deep purple. Stamens 12, diplostaminous, inserted near the base of hypanthium, some or all exserted. Ovary bilocular, spindle-shaped; style exserted or included; longer or shorter than both whorls of the stamens, or longer than the inner whorl but shorter than the outer; stigma capitate-subglobose, papillose. Capsule included in the hypanthium, 2-valved, spindle-shaped. Seeds triangular.