Herb, forming large patches; stems creeping or floating, rooting at nodes, with pneumatophores sometimes present below water; flowering stems ascending, with patent hairs or more rarely glabrate. Lvs alternate; petiole 0.5-3 cm long, glabrous or somewhat hairy. Lamina 2-8 × 0.7-3 cm, elliptic, oblanceolate or obovate, glabrous except for midrib near base; base cuneate to attenuate; apex obtuse to rounded. Fls solitary, 4-5-merous; pedicels 1.5-4.5 cm long at anthesis, generally with patent hairs. Sepals 6-8 mm long, narrow-triangular or lanceolate-oblong, scarcely accrescent; apex emarginate. Petals 1.5-1.7 mm long, bright yellow. Stamens 8 or 10; filaments unequal. Style c. 4 mm long, stout, hairy. Stigma slightly 4-lobed. Capsule 2-2.7 cm long, narrow-cylindric, ribbed, woody, glabrous or glabrate. Seeds firmly embedded in cubes of woody endocarp c. 1.5 mm thick, uniseriate in each locule.