N. Vietnam, Hoa Binh prov., Da Bac distr., Cao Son municipality, Nui Hen (Ba Tri) mountain system (20°54′09′'N, 105°12′15′'E). Remnants of primary forest among secondary wet broad-leaved evergreen forest with bamboo on very steep mountain slopes based on shale and sandstones with quartzite at 700-800 m a.s.l. Woody fern with stem up to 5 m hg and fronds about 2.5 m lg in open wet slope of the river. Very common at 600-800 m a.s.l.