Herbs, annual, erect, densely appressed-hairy throughout. Leaves opposite, linear-lanceolate; bracts herbaceous, leaf-like; stipules absent. Flowers solitary or in few-flowered dichasial cymes, 5-merous, bisexual. Calyx tubular, 10-veined, with 5 spreading, foliaceous lobes longer than petals. Petals 5, purple or rarely white, shorter than calyx, entire, tapering into a distinct claw; coronal scales absent. Stamens 10, with 5 united to petals. Ovary 1-celled; ovules numerous; styles 5. Capsule ovoid, opening by 5 teeth; carpophore absent. Seeds numerous, ± ovoid or reniform, echinulate/tuberculate.
Herbs annual. Stems erect. Leaves narrowly lanceolate to linear. Flowers in few flowered, lax dichasia. Calyx tube ovate or elliptic-ovate, with 10 longitudinal, raised veins; teeth 5, leaflike, linear, usually longer than tube. Androgynophore absent. Petals 5; limb usually shorter than calyx teeth, emarginate, gradually turning to claw; coronal scales absent. Stamens 10. Ovary 1-locular; styles 5, hairy, alternating with calyx lobes. Capsule ovoid, septicidally dehiscing by 5 teeth. Seeds numerous.
Cal-lobes 5, much longer than the coarsely 10-ribbed tube; pet 5, without auricles or appendages; stamens 10; styles (4)5; capsule dehiscent by (4)5 ascending teeth; annual with opposite, entire, exstipulate lvs. 2, Eurasia.