2. Potamogeton oxyphyllus Miquel, Ann. Mus. Bot. Lugduno-Batavi. 3: 161. 1867.
尖叶眼子菜 jian ye yan zi cai
Potamogeton chongyangensis W. X. Wang.
Plants perennial or annual, submerged in fresh water. Rhizome present or absent. Stems usually creeping at base, filiform, 0.5-1 mm in diam., densely branched; nodal glands absent; turions shootlike, strongly shortened, leafy, axillary or terminating lateral branches. Stipules axillary, free, 6-12 mm, convolute, membranous and translucent, fibrous-persistent; leaves sessile, linear, slightly to distinctly falcate, 3-10 cm × 1.5-3 mm, 5-7-veined with 2-18 faint but visible sclerenchymatous strands, with narrow rows of lacunae bordering midvein, midvein not thickened toward leaf base, base narrowly cuneate, attenuate toward apex, apex acuminate. Spikes in 3 or 4 whorls of opposite flowers, contiguous, broadly cylindric. Carpels 4. Fruit obovoid, 3-3.5 mm, abaxial keels 3, with a sharp midrib, with a short beak ca. 0.5 mm at tip. Fl. and fr. Jun-Oct. 2n = 26.
Ponds and streams, usually in slightly acid water. Anhui, Heilongjiang, Hubei, Jiangsu, Jiangxi, Liaoning, S Shaanxi, Taiwan, Xizang, Yunnan, Zhejiang [Indonesia (Sumatra), Japan, Korea, Russia].