N. Vietnam, Prov. Cao Bang, distr. Tra Linh, municipalite Quoc Toan, vicinity of Thang Heng and Lung Tao villages near Thang Heng lake. Closed evergreen broadleaved primary forest on steep slopes and bluffs of limestone ridges and mesas at 550-600 m alt. Epilitic herb on vertical shadow bluffs. Leaves pale green with white numerous smallest marks. Not common, but occasionally abundant. VH 4973 25-27.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)