N. Vietnam, Tuyen Quang prov., Na Hang distr., Xuan Tam municipality, near Ban Cai village (22°29′18′'N, 105°19′47′'E). Primary broad-leaved evergreen dry forest on very steep slopes of highly eroded remnant limestone ridge at elev. 450-500 m a.s.l. Terrestrial herb up to 1 m hg on very steep rocky slopes. Flowers yellow. Rare.