Annuals. Stems not articulate. Leaves opposite, small, simple, more or less coriaceous, acute to spinescent. Flowers hermaphrodite, axillary, solitary, grouped in terminal spike-like inflorescences, 2-bracteolate. Perianth segments 5, connate at base, the outer 3 (rarely 2) with a dorsal wing in fruit, or (rarely) all segments without wings. Stamens 5, inserted on a small disk; anthers obtuse or apiculate; staminodes (disk lobes) 5. Stigmas style-like, (stylodia) almost free. Fruit included in the perianth, membranous. Seeds compressed; embryo vertical.