Annual; pubescent throughout. Stem erect, branching especially at base, 10–35 cm high. Leaves sessile, ovate-spathulate to linear-lanceolate, 10–30 mm long, 2–5 mm wide. Inflorescence of dense lateral and terminal clusters; bracts herbaceous. Flowers bisexual, pedicels 2–5 times calyx length; calyx ellipsoid, campanulate in fruit, 7–10 mm long, 10-veined, reticulate, pubescent on veins otherwise glabrous, calyx-lobes triangular, acute or acuminate, margins ciliate; petals absent or shorter than calyx, rarely exserted, limb 1.5–3 mm long, deeply bifid, white, pink or greenish; styles 3. Capsule ovoid-oblong, 5–10 mm long; carpophore 1–2 mm long, more or less glabrous; seeds reniform, flattened, dorsal rim with 2 undulate wings, dull blackish-brown, striate, up to 1 mm long. Flowers Aug.–Sep.