Two new species of Lasianthus Jack (Rubiaceae) from southern Vietnam

Two new species of shrubs in the genus Lasianthus Jack (Rubiaceae), L. naikii V.S.Dang & Vuong sp. nov. and L. sonlangensis V.S.Dang, Vuong & Quan sp. nov. from Kon Chu Rang Nature Reserve of Gia Lai Province in southern Vietnam, are described and illustrated. The similarities and differences of two new species with the morphologically closest allies are presented. Descriptions, illustrations, colour plates and vernacular names are provided.