Hippuris eschscholtzii Lamarck; H. montana Reichenbach; H. spiralis D. Yu; H. vulgaris var. ramificans D. Yu.
Stems 10-150 cm or longer in running water. Leaves (4-)8-12-whorled, often spreading, lanceolate to linear, 1.5-6 × 0.1-0.2 cm, longest at mid-shoot, margin entire to weakly denticulate, apex somewhat thickened, subacute; submerged leaves longer than emergent leaves. Flowers purplish. Stamens ca. 1.5 mm. Ovary ca. 1 mm. Achene ovoid-ellipsoid, 1.5-2.5 mm, smooth. Fl. Apr-Sep, fr. May-Oct.
Stagnant and slow-running waters, lakes, bogs, streams, river shores, paddy fields; near sea level to 5000 m. Gansu, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan [temperate regions worldwide].
The character of leaves spirally arranged seems not to be true for Hippuris spiralis. In fact, in that entity the leaves are whorled but the whorls are oblique. This variation may be caused by twisted shoots, especially in running water. Terminal subshoots are a common variant in H. vulgaris. For these reasons, both H. spiralis and H. vulgaris var. ramificans are treated here as synonyms of H. vulgaris.
