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 foothills of limestone ridges and mesas near karst lake at 500-550 m alt. Terrestrial and epilitic herb on wet open steep rocky lake slopes. Flowers white. Very common. VH 4932 25-27.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)