N. Vietnam, Prov. Cao Bang, distr. Tra Linh, municipalite Quoc Toan, vicinity of Thang Heng and Lung Tao villages near Thang Heng lake. Broadleaved evergreen closed primary forest on steep slopes and bluffs of limestone mesas and ridges at 550-650 m alt. Terrestrial fern on steep rocky shadow slopes. Common. VH 4866 25-27.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)