Prostrate to erect perennial herbs or subshrubs; branches mostly compressed. Leaves opposite, usually connate at base, terete to trigonous. Flowers solitary or in cymes, axillary or terminal, subsessile to pedicellate; sepals 5, subequal; petaloid staminodes numerous; ovary inferior, 5-locular; ovules numerous, parietal. Fruit a 5-locular capsule; valves winged; locules remaining partly covered by an elastic, membranous 'roof'; seeds pear-shaped, tuberculate.
About 195 species endemic in the Cape Province of South Africa; 4 species naturalised in Australia.