Herbs perennial. Leaves and branches opposite, rarely whorled. Flowers hermaphroditic, with 1 bract and 2 bracteoles, axillary or clustered into spikes. Bracts and bracteoles small, membranous. Tepals 4, persistent, lanceolate, subulate. Stamens 4 or 5, united at base; pseudostaminodes triangular or nearly quadrangular (subulate), alternate with stamens. Styles very short; stigma very short, 2-parted. Utricles dehiscent by lid. Seeds ovoid.