Perennial herbs, rarely annual. Stipules 0. Leaves opposite, usually alternate above, toothed or entire. Flowers in a terminal inflorescence. Bracteoles 0. Sepals 4, not persistent. Petals 4, rose-purple or white, emarginate. Stamens 8. Stigma clavate, spherical or deeply 4-lobed. Ovary 4-locular. Dehiscence of capsule loculicidal. Seeds with a prominent tuft of hairs.