Plant: annual aquatic herb; vegetative stem submersed with elongate internodes, or emersed and short Leaves: few, submersed, thickened, green on abaxial surface, linear to oblanceolate, obtuse at apex; petiolate leaves emersed, oblong to oval, cuneate to truncate at base, acute to obtuse at apex, 1-5 cm long, the petiole rigid Inflorescence: 1-flowered Flowers: perianth salverform, blue or white, the tube 15-44 mm long, the lobes narrowly elliptic, obtuse at apex, 5.2-26.3 mm long, the upper lobes yellow toward base; stamens of two sizes, the lateral stamens 2.3-7.8 mm long, with yellow anthers 0.9-3.3 mm long; central stamen 3.3-7.2 mm long, with a purple or white anther 1.3-3.9 mm long; mature pollen remaining in tetrads Fruit: an elongate capsule with longitudinal dehiscence. SEEDS many, 0.5-0.8 mm long, the testa with longitudinal wings and cross striae between wings Misc: Ponds and ditches; up to 1500 m (4500 ft.); Mar.-Sep.