FLORA OF VIETNAM Rubiaceae Ophiorrhiza tonkinensis Pit.?
Quang Binh Prov., Minh Hoa Distr., Thuong Hoa municipality, around point 17°41′28”N 105°53′42.7”E.
Primary closed evergreen broad-leaved forest on rocky very steep cliffy slope of remnant mountain composed with solid crystalline limestone at elevation about 700 m a.s.l. near to the top of mountain.
Lithophytic herb to 2 cm tall on shelves of vertical shady cliff. Common on mountain top.