Succulent aquatic; stems to 3 m long, prostrate or floating, finally ascending, rooting at lower nodes. Leaves emergent; petioles 17-54 cm long (those of the floral leaf shoot as short as 5 cm long); petiole sheaths with ligule to 7.5 cm long (those in axil of floral shoot to 24 cm long); blades ovate-cordate, reniform or sagittate,15-34 cm long, about as wide as long, the sinus open or narrow, the veins closely spaced, radiating from apex of sinus but arcuate-ascending near margin. Spikes axillary, many-flowered; peduncles 6-25 cm long, spathate beneath flowers; flowers bilabiate, tristylous, congested at apex of the pilose rachis; perianth blue, 1.5-2.2 cm long, 6-lobed to near base, sparsely pubescent, the hardened bases spinulose-ridged, the largest lobe grooved with a bilobed yellow spot; stamens 6, unequal, in 2 groups of 3 each; anthers introrse, blue; filaments adnate to tube basally, glandular-pubescent near apex; style 1, of 3 possible lengths: (1) short with medium and long stamens; (2) medium with short and long stamens; or (3) long with short and medium stamens; stigma trilobate, each lobe bifid. Fruits ovoid, indehiscent utricles; seed 1, ovoid, 6-7 mm long. Croat 7065.