3. Lemna japonica Landolt, Veröff. Geobot. Inst. E.T.H. Stiftung Rübel Zürich. 70: 23. 1980.
日本浮萍 ri ben fu ping
Lemna leiboensis M. G. Liu & C. H. You.
Fronds free floating on water surface, 1-8 coherent in one group, without green stalk at base (but with a thin white stipe connecting fronds), shiny green, sometimes reddish or red on lower surface (always deeper red on lower surface than on upper), obovate to elliptic, 2-6(-7) mm, 1.3-1.8 × as long as wide, flat or slightly gibbous on lower surface, with mostly distinct papillae on upper surface near apex and above node and indistinct ones along midline, margin entire, base rounded; veins 3(-5), nearly reaching apex, greatest distance between lateral veins near or proximal to middle, lateral veins outcurved medially. Root 0.5-15(-18) cm, sheath not winged, apex rounded (to pointed). Turions absent. Ovary with 1 ovule; utricular scale with narrow opening at apex. Fruit not known. Fl. (very rare) Jul-Oct. 2n = 40*, 50, 63.
Lakesides, pools, ponds, ditches; in regions with moderately temperate to warm-temperate climate; sea level to 2900 m. Hebei, Heilongjiang, Henan, Hubei, Jiangsu, Nei Mongol, Shaanxi, Shandong, Shanxi, S Sichuan, Yunnan, Zhejiang [Japan, Korea].
Lemna japonica may have originated from hybridization between L. minor and L. turionifera.
Lemna leiboensis, described from S Sichuan, most likely is conspecific with L. japonica. It can only be distinguished by its larger fronds, conspicuous veins, and pointed root caps. However, these characters are shared by L. japonica as well.