Annual, glabrous and glaucous herbs. Leaves opposite; stipules absent; bracts herbaceous. Flowers solitary or in few-flowered dichasia, usually 5-merous, bisexual; sepals 4 or 5, free; petals entire; stamens 8 (rarely 10) or 4 (rarely 5); ovary 1-celled, with many ovules, styles 4(–5). Capsule oblong, straight, opening by as many or twice as many teeth as styles; seeds numerous, discoid to angular-nautiloid, tuberculate.
6 species indigenous to Europe and the Mediterranean; 1 species naturalised in Australia.