18. Potamogeton natans Linnaeus, Sp. Pl. 1: 126. 1753.
浮叶眼子菜 fu ye yan zi cai
Potamogeton morongii A. Bennett.
Plants perennial, in fresh water. Rhizome slender to robust, terete. Stems slender to robust, terete, 1.5-2 mm in diam., usually simple or occasionally sparsely branched. Leaves dimorphic. Submerged leaves reduced to long, narrowly linear, obtuse phyllodes, 10-20 cm × 2-3 mm, often disappearing early, 1-3-veined. Floating leaves with axillary, convolute, often fibrous-persistent stipules 4-17 cm, petiolate, with a flexible discolored joint and distinct angle at top of petiole immediately below blade; blade opaque, ovate to broadly oblong-ovate or ovate-elliptic, 4-9 × 2.5-5 cm, leathery, 17-35-veined, base cuneate to subcordate, apex rounded or cuspidate. Spikes cylindric, 3-5 cm, densely flowered; peduncles 3-8 cm. Carpels 4. Fruit obovoid, 3.5-4.5 mm, abaxial keel obtuse, indistinct, with a short beak at tip. Fl. and fr. Jul-Oct. 2n = 52.
Lakes, ponds, channels, usually in slightly acid water. Heilongjiang, Xizang [Afghanistan, Japan, Kazakhstan, Korea, Kyrgyzstan, Mongolia, Myanmar, Nepal, Russia, Tajikistan, Uzbekistan; temperate and boreal regions of Africa, SW Asia, Europe, and North America].