FLORA OF VIETNAM Rubiaceae s.l. Silvianthus tonkinensis (Gagnep.) Ridsdale
N.Vietnam, Thanh Hoa Prov., Quan Hoa Distr., Phu Le Municipality, Hang village, around point 20°31′33′'N, 105°05′06′'E. Primary evergreen seasonal broad-leaved closed lowland forest on steep slopes of rocky ridge composed with crystalline marble-like highly eroded limestone at elev. 500-550 m. Shrub 1.5-2 m tall. Fruits white-pinkish. Not rare.