Sp. Pl. 2: 979. 1753.
Gen. Pl. ed. 5, 420. 1754.
Herbs, annual, monoecious, covered with rusty-colored, stellate, and whitish simple trichomes. Stems ascending, not jointed or armed, slender. Leaves alternate, petiolate; blade ovatelanceolate to narrowly lanceolate, base tapered, margins entire, plane or revolute, apex acute to acuminate. Inflorescences glomerules, cymes, or flowers solitary. Staminate flowers in terminal glomerules or at end of pistillate cymes. Pistillate flowers solitary in upper leaf-axils or forming cymes commingled with staminate flowers. Flowers unisexual; staminate with perianth segments 3–5, stamens 2–5; pistillate with bracteoles 2, perianth segments 3–4, stigmas 2, filiform. Fruiting structures persistent, accrescent perianth surrounding utricle; utricles winged, obovate to cuneate, laterally compressed; pericarp adherent. Seeds vertical, ovoid; seed-coat grayish, granular; embryo horseshoe-shaped; perisperm copious. x = 9.
Species ca. 5 (1 in the flora).