Vientiane prov., Kasi distr., between Pa Chao and Nam Ken villages, Pa Chao Mt., around point 19°19'50.6''N 102°21'20.5''E.
Secondary broad-leaved evergreen dry forest on very steep rocky mountain slopes composed by solid marble like highly eroded limestone at elev. 1000-1100 m a.s.l. Herbaceous vine to 10 m long in open secondary forest. Not rare.
Houphan Prov., Viengxay Distr., Xieng Luong village, around point 20°22'06.1''N 104°17'18.6''E. Primary and secondary broad-leaved evergreen dry forest on very steep rocky slopes of highly eroded mountains composed by solid marble-like limestone at elev. 600-700 m a.s.l. Herbaceous vine 4-5 m long in alluvial valley between limestone mountains among open secondary scrub. Common.
Cao Bang Prov., Bao Lac Distr., Hong An municipality, Mi Lung village. Primary broad-leaved and mixed humid evergreen forest on very steep slopes and along rocky ridge composed with solid crystalline highly eroded limestone at elevation 1500-1550 m a.s.l. around point 22°50’01.3’’N 105°50’05.7’’E. Herbaceous vine to 10 m long in open rocky slope. Flowers pale dull yellowish. Very common.
Houphan Prov., Viengxay Distr., Xieng Luong village, around point 20°22'06.1''N 104°17'18.6''E. Primary and secondary broad-leaved evergreen dry forest on very steep rocky slopes of highly eroded mountains composed by solid marble-like limestone at elev. 600-700 m a.s.l. Herbaceous vine 3-4 m long among open secondary shrubs in alluvial mountain foothills. Common.
Houphan Prov., Viengxay Distr., Xieng Luong village, around point 20°22'06.1''N 104°17'18.6''E. Primary and secondary broad-leaved evergreen dry forest on very steep rocky slopes of highly eroded mountains composed by solid marble-like limestone at elev. 600-700 m a.s.l. Herbaceous vine 3-4 m long in rather open place. Flowers white, very fragrant. Common.
N. Vietnam, prov. Ha Giang, distr. Yen Minh, municipality Du Gia, E slopes of Phu Tha Ca mountain system at 1600-1700 m elev. (N 23ш56' E 105ш13'). Primary evergreen broadleaved very wet mountain forest on shale very steep slopes. Lithophyte herb on open wet vertical shale-quartzite cliffs along waterfall. Flowers white with violet tint.
No CBL 2067 03 May 1999
International Botanical Expedition of the U.S.A. National Geographic
Son La Prov., Moc Chau Distr., Chieng Son comm., about 1 km to NE from Chieng Son Village, around point 20°46’02.0N 104°37’03.1E. Remnants of primary broad-leaved evergreen forest on tops of hills composed with karstic highly eroded yellow-white limestone at elevation 1150-1250 m a.s.l. Herbaceous vine 3-4 m long on exposed mossy rocks near mountain top. Not common.
Son La Prov., Van Ho Distr., Van Ho comm., Hua Tat village, around point 20°46’21.7N 104°47’47.5E. Remnants of primary evergreen broad-leaved and mixed forest (with Pinus wangii) on very steep rocky slopes and on mountain tops composed with highly eroded karstic light gray marble-like limestone at elevation 1300-1350 m a.s.l. Terrestrial herb on steep wet open slope. Flowers white. Locally common.