N. Vietnam, Prov. Cao Bang, distr. Tra Linh, municipalite Quoc Toan, vicinity of Thang Heng and Lung Tao villages near Thang Heng lake. Dry broadleaved evergreen closed primary forest on steep slopes and bluffs of limestone ridges and mesas at 650-700 m alt. Terrestrial and epilitic herb on shadow dry rocky slopes. Flowers pale greenish with pink tint. Leaves pure light green. Not common. VH 4924 25-27.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)