Perennial with a long creeping rootstock. Stem long, floating, rooting at the nodes. Leaves floating, lamina more or less rounded or rarely orbicular with a cordate base, 2.5-5 (-11) cm x 2-6 cm with dense conspicuous dark glands on the under surface with margin entire or wavy, petiole (2-) 3-7 (-10) cm long. Flowers in an axillary fasciculate umbel, pedicels 5-7 cm long. Calyx 7-10 mm long, c.4 mm broad, obtusish, Corolla 18-25 mm long, bright yellow, united almost one third with obovate emarginate lobes, finely and sparingly fringed. Anthers more or less enlarged in their lower part, 3-4 mm long, filaments bearded with 5 oblong, oval, ciliate appendages at the top. Stigma bilobed, style 4-5 mm long, ovary shorter than the style. Capsule ovoid, 18.25 mm long, acute; seeds ellipsoid, 4-6 mm x c.3 mm, winged.