4. Lemna minor Linnaeus, Sp. Pl. 2: 970. 1753.
浮萍 fu ping
Fronds free floating on water surface, 1-8 coherent in one small group, without green stalk at base (but with a thin white stipe connecting fronds), shiny green, sometimes reddish on upper surface, scarcely reddish on lower surface (always deeper red on upper surface than on lower), obovate to elliptic, 2-6(-10) mm, 1.3-2 × as long as wide, flat, with mostly distinct papillae on upper surface near apex and above node, margin entire, base rounded; veins 3(-5), nearly reaching apex, greatest distance between lateral veins near or proximal to middle. Root 0.5-15 cm, sheath not winged, apex mostly rounded. Turions absent. Ovary with 1 ovule; utricular scale with narrow opening at apex. Fruit winged laterally toward apex. Seed with 10-16 distinct ribs. Fl. (rare) May-Sep. 2n = 20, 40, 42, 50, 63, 126.
Lakesides, pools, ponds, ditches, slow-flowing streams; in regions with suboceanic cool- to moderately temperate climate; (sea level to) 2000-3000 m. W Xizang [Afghanistan, N India, Kazakhstan, Nepal, N Pakistan, W Russia, Turkmenistan; Africa, SW Asia, Europe, North America; introduced in Australia, Japan, and Pacific islands (New Zealand)].