11. Potamogeton perfoliatus Linnaeus, Sp. Pl. 1: 126. 1753.
穿叶眼子菜 chuan ye yan zi cai
Potamogeton perfoliatus var. mandschuriensis A. Bennett.
Plants perennial, submerged in fresh water. Rhizome unspotted, terete, slender. Stems terete, 0.5-2.5 mm in diam., densely branched at upper part. Stipules axillary, convolute, 3-22 mm, membranous, evanescent; leaves sessile, lanceolate to broadly ovate, orbicular-ovate, or ovate-oblong, 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 cylindric, 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 2 indistinct lateral keels, with a short beak at tip. Fl. and fr. May-Oct. 2n = 52.
Lakes, ponds, rivers, channels. Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jilin, Liaoning, Nei Mongol, Qinghai, Shandong, Shanxi, Xinjiang, Xizang, Yunnan [Afghanistan, India, Indonesia (Sumatra), Japan, Kazakhstan, Korea, Kyrgyzstan, Mongolia, Pakistan, Russia, Tajikistan, Uzbekistan; Africa, SW Asia, Australia, Central and North America, Europe].