稀脉浮萍 xi mai fu ping

Lemna paucicostata Hegelmaier; L. perpusilla Torrey var. trinervis Austin; L. trinervis (Austin) Small.

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 bright green, without reddish color, obovate to lanceolate, 1.5-4(-6.5) mm, 1-3 × as long as wide, flat, with distinct papillae on upper surface near apex and above node, margin entire, base rounded; veins 3, nearly reaching apex, lateral veins outcurved at middle. Root 0.5-3 cm, sheath winged toward base, apex pointed. Turions absent. Ovary with 1 ovule; utricular scale with slit on one side. Fruit not winged. Seed with 8-24 distinct longitudinal ribs. Fl. (frequent) all seasons. 2n = 20, 40*, 42, 50*, 60, 70, 80, 84.

Lakesides, pools, ponds, rice fields, ditches; in regions with warm-temperate to tropical climate; sea level to 2800 m. Anhui, Fujian, Guangdong, Guizhou, Hebei, Henan, Hubei, Jiangsu, Jiangxi, Liaoning, Qinghai, Shaanxi, Shandong, Shanxi, Taiwan, Yunnan, Zhejiang [worldwide].

The plants with large thin fronds and conspicuous veins and without distinct papillae are often called Lemna trinervis. These characters, however, can be observed easily in most geographical races of L. aequinoctialis.

In FRPS (13(2): 210. 1979), the name Lemna perpusilla Torrey was misapplied to this species.