FLORA OF VIETNAM Acanthaceae Gymnostachyum sp. nov. Son La province, Quynh Nhai district, Muong Giang commune, Remnant primary evergreen broad-leaved forest on limestone mountains, at middle of steep slopes, around point 21.63389° N 103.55481° E, at elevation of 1130 m a.s.l. Terrestrial shrubs about 50 – 100 cm tall, flower white abaxially, and tinted with violet adaxially, locally common. March 2019, Nguyen Sinh Khang et al., NSK 1171