Plants annual, submerged in fresh water. Rhizome absent. Stems densely branched, internodes slightly to strongly compressed, 1.2-3.5 mm wide; nodal glands absent; turions axillary or terminal, shortened shootlike, leafy. Stipules axillary, convolute, 1-1.8 cm, translucent, often fibrous-persistent at apex; leaves sessile, linear, 5-15 cm × 2.4-4.8 mm, 3-5-veined with 12-32 sclerenchymatous strands faint but visible, with narrow rows of lacunae bordering midvein, base narrowly cuneate, apex subacute to rounded and mucronate. Spikes 1.6-3.3 cm in 4-7 whorls of opposite flowers, contiguous, cylindric; peduncles 2.5-6 cm. Carpels usually 2. Fruit subrounded, 3.4-4.6 mm, abaxial keel distinct, beak slightly curved toward back. Fl. and fr. Jul-Sep. 2n = 26.
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