FLORA OF LAOS Acantaceae Strobilanthes arborescens sp.nov. Luang Prabang prov., Pon Xay distr., between Houay Man and Nam Bo villages, Phou Hua Ben Toc Mountain, around point 19°57'33.1''N 102°25'25.8''E. Degraded primary evergreen and semideciduous forest on very steep rocky mountain slopes composed by solid marble like highly eroded limestone at elev. 500-650 m a.s.l. Deciduous treelet or shrub 2-4 m tall on open karstic rocks on mountain top. Flowers blue. Very common. Main co-dominant of deciduous scrub on open tops of karstic limestone mountains. LA-VN 2130 5 April 2017 Coll.: L.Averyanov, N.T.Hiep, N.S.Khang, C.Q.Ngan, T.Maisak, Vichith Lamxay, Koudkeo Phommachanh, Phizar Sayalath, Keooudone Souvannakhoummane.