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 600 m alt. Herb vine 3-4 m lg on wet open rocky steep slopes. Flowers yellowish. Not common. VH 4981 25-27.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)