FLORA OF VIETNAM Polypodiaceae s.l. Onichium siliculosum
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 500-550 m a.s.l.
Secondary shrubs on very steep mossy rocky slope of N exposition of rocky ridge composed with light gray solid marble-like highly eroded crystalline limestone along Quy Son River valley.
Terrestrial fern on very steep slope. Locally common.