30-50 cm high herb, with short stem and many long fibrous roots, floating or sometimes rooting. Leaves glabrous, 45-110 x 50-100 mm; broadly ovate to rhomboid, entire, obtuse, base cuneate or rounded. Petiole glabrous and spongy, 6-30 cm long, with a fusiform bulbous portion about the middle. Peduncle spongy. Inflorescence (3-)6-15 (-35) flowered. Flowers lilac, tinged blue, withering soon. Perianth c. 57 mm long, tube green, glandular; segments 34-40 mm long, obovate to ovate-oblong, posterior segment with a yellow spot. The longer 3 stamens c. 21 mm, filaments curved, glandular hairy;shorter filaments c. 6 mm long, glabrous; anthers purple-blue. Ovary ovoid, glabrous; style glandular; stigma 3-lobed, glandular.