N. Vietnam, prov. Cao Bang, distr. Tra Linh, municipality Quoc Toan, vicinities of Lung Tao village (N 22°45′ E 106°19′), about 12 km from Cao Bang town to the NNE. Aquatic floating plant in slow-water pools along small streamlet on alluvial valley between remnant limestone ridges at 600 m alt. Not rare.
CBL 1257 14 Dec. 1998
International Botanical Expedition of the U.S.A. National Geographic Society (grant No 6300-98)
Collectors: N.T.Hiep, N.Q.Binh, P.K.Loc, N.X.Tam, Averyanov L.