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General DescriptionPlants perennial, submerged in freshwater. Rhizome unspotted, terete, slender. Stems densely branched at upper part, terete, 0.5-2.5 mm in diameter. Stipules axillary, convolute, 3-22 mm, membranous, evanescent. Leaves sessile; leaf blade lanceolate to broadly ovate, orbicular-ovate, or ovate-oblong to lanceolate, 3-5-veined, with narrow rows of lacunae bordering midvein, base cordate and amplexicaul, margin minutely denticulate, apex obtuse or rounded. Spikes usually contiguous and cylindrical, with 4-7 whorls of opposite flowers; peduncles 2-11 cm. Carpels 4. Fruit obovoid, 2.5-4.5 mm; abaxial keels 3, with a slightly sharp midvein and two indistinct lateral keels, with a short beak at tip.