Polycarpon depressum Nutt.

Stems prostrate, 1-6 cm. Leaves opposite, not whorled; stipules 0.4-1.2 mm; blade spatulate to obovate or oblanceolate, 3-9 mm. Inflorescence bracts mostly present. Flowers: sepals flat or sometimes barely keeled, 1-1.5 mm; petals linear to elliptic, 0.8-1 mm, 2 times as long as sepals; stamens 3-5. Capsules not clasped by calyx, spherical, valve margins straight or only slightly rolled inward after dehiscence. Seeds obliquely triangular, 0.4-0.5 mm, finely granular.