6. Alternanthera sessilis (Linnaeus) R. Brown ex de Candolle, Cat. Pl. Hort. Monsp. 77. 1813.
Gomphrena sessilis Linnaeus, Sp. Pl. 1: 225. 1753
Herbs, annual or perennial, 2-6 dm. Stems procumbent, pubes-cent in lines, glabrate. Leaves sessile; blade elliptic to oblong or oblanceolate, 1.2-5 × 0.5-2.2 cm, apex obtuse to acute, glabrous. Inflorescences axillary, sessile; heads white, subglobose or ovoid, 0.5-1.1 cm; bracts keeled, ca. 1/2 as long as tepals. Flowers: tepals white, ovate to lanceolate, 2-3.5 mm, apex acuminate, hairs not barbed; stamens 5; anthers 3-5, globose; pseudostaminodes subulate, margins laciniate. Utricles included within tepals, sides exerted in mature fruit, greenish stramineous, obcordate, 1.3-1.7 mm, apex retuse. Seeds lenticular, 0.9-1.1 mm.
Flowering summer-early fall. Wet disturbed areas; 0-20 m; introduced, Ala., Fla., Ga., La.; Mexico; West Indies; Central America (Belize, Costa Rica, Guatemala, Nicaragua, Panama); South America; Africa; Asia.
Alternanthera sessilis is reported from Maryland, Mississippi, South Carolina, and Texas, but I have seen no specimens from these states.