Herbs erect, annual, sometimes woody at base and perennial, often in water and then with elongate pneumatophores on submerged branches. Stems 50-300 cm tall, branched, new growth and inflorescence minutely puberulous. Petiole 3-18 mm; leaf blade lanceolate, 2-9 × 0.5-2 cm, subglabrous or puberulous, lateral veins 7-15 per side, submarginal vein inconspicuous, base narrowly cuneate, apex acuminate. Sepals 4, lanceolate, 2-4 mm, finely puberulous. Petals yellow, fading to orange-yellow, elliptic, 2-3 × 1-2 mm. Stamens 2 × as many as sepals; anthers 0.4-0.6 mm; pollen in monads. Style 1-1.5 mm; stigma depressed-globose. Capsule cylindric, subterete, enlarged in upper 1/6-1/3, 1.5-3 cm, finely puberulous, relatively thinly walled; subsessile. Seeds in inflated upper capsule in 2 or more rows per locule, free, pale brown, ovoid, 0.3-0.5 mm, raphe narrow; seeds in lower capsule in one row per locule, embedded in cube of relatively hard endocarp, brown, 0.7-0.9 mm, raphe ca. 1/3 width of seed. Fl. and fr. Jun-Feb. 2n = 16*.