FLORA OF VIETNAM Apocynaceae Alstonia guangxiensis D.Fang & X.X. Chen
N.Vietnam, Cao Bang Prov., Trung Khanh Distr., Ngoc Khe Municipality, Pac Nga village, around point 22°54′59′'N, 106°31′44′'E, at elevation 800-850 m a.s.l.
Remnants of primary broad-leaved and coniferous forest on ridge tops and on very steep slopes and cliffs of rocky ridges and mesae composed with light gray solid marble-like highly eroded crystalline limestone.