Plant: perennial aquatic herb; vegetative stem submersed and growing to surface or emersed and contracted, procumbent, branching Leaves: sessile, submersed or emersed, alternate (opposite at nodes with inflorescences), linear, entire, 2-10 cm long, 1-5 mm wide; apex acute; base clasping Inflorescence: 1-flowered Flowers: perianth salverform, yellow, the tube 1.5-5 cm long, the lobes linear, obtuse at apex, 4-11 mm long; stamens all of equal size, 2-10 mm long, the filaments centrally inflated, the anthers lanceolate, yellow, coiling after anthesis, 0.9-3.9 mm long Fruit: SEEDS 7-30, 1.0-1.6 mm long, the testa with longitudinal wings and cross striae between wings Misc: Rivers and canals; up to 600 m (1800 ft.); fl. Jun.-Oct.; no fr. seen