N. Vietnam, Prov. Cao Bang, distr. Tra Linh, municipalite Quoc Toan, vicinity of Thang Heng and Lung Tao villages near Thang Heng lake. Remnant closed evergreen primary broadleaved forest in alluvial valley bottom between limestone ridges and mesas near karst lake at 500 m alt. Terrestrial and epilitic herb up to 1.2 m hg on shadow rocky wet lake slopes. Flowers white with yellow tip of central tepal. Not common. VH 4858 25-27.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)