Annual rigid herbs, dichotomously branched. Leaves opposite, awl-shaped, exstipulate. Bracts narrow. Flowers small. Calyx tubular, usually 15-nerved, persistent; teeth 5, acute. Petals 5, long-clawed, with small, emarginate or 2-fid or dentate limb; coronal scales 0 or present as short, crisp hairs. Stamens 5-10. Ovary 1-celled, many-ovuled; styles 2. Capsule long-cylindrical, 4-toothed, borne on a very short carpophore. Seeds few, with a straight embryo.