Annual or perennial herbs. Stems 4-angled to -winged. Flowers 4-merous, borne in axillary few-many-flowered fascicles. Calyx campanulate with 4 erect lobes. Corolla: tube with 4 semilunate fimbriate-papillose scales subtending the filaments; lobes 4, without nectaries. Stamens ± equal, all fertile. Ovary 1-locular; ovules numerous. Fruit a 2-valved obovoid capsule.