Description from Flora of China
Plants mostly monoecious, rarely with bisexual flowers. Stem much branched, 100-250 cm, densely leafy in upper part, sparsely light green warty; internodes ca. 3 cm. Submerged leaves 4- or 5-whorled, pectinate, broadly ovate in outline, 3-3.5 × 1-2.5 cm; segments in 13-16 pairs, filiform, 1-1.5 cm. Inflorescence a terminal spike of 4-whorled flowers, 6-10 cm; bracts reniform or suborbicular, shorter than flowers, broader than long. Male flowers: bracteoles rhombic to elongate, margin entire; calyx broadly campanulate, 0.5-1 mm, 4-parted nearly to middle; petals 4(or 5), pale pink, elliptic, 1.5-2.5 mm; stamens 8, without androphore. Female flowers: bracteoles pectinate, lanceolate in outline; calyx tubiform, 0.7-1 mm, margin shortly lobed; petals absent or minute and caducous. Fruit 4-loculed, subcylindric, ca. 2 × 1.5 mm; mericarps abaxially rounded, smooth or sparsely verrucose along margins. Fl. and fr. Apr-Sep.
Stagnant waters, lakes, ditches, slow streams, springs; near sea level to 4200 m, rarely to 5200 m in springs in Xizang. Throughout China [Asia, Europe].