Northern Vietnam, Tuyen Quang Prov., Na Hang Distr., Thuong Lam Municipality, Na Lau village, in the vicinity of point 22°28′23′'N, 105°19′47′'E. Primary evergreen seasonal broad-leaved forest on highly eroded remnant ridge composed with soft stratified limestone consolidated with numerous quartzite dikes at elev. 450-500 m a.s.l. Lithophytic herb on wet travertine deposited on vertical shady cliff. Flowers light blue. Occasional.