Lasianthus honbaensis (Rubiaceae), a New Species from Southern Vietnam

Lasianthus honbaensis V.S. Dang, Tagane & H. Toyama sp. nova (Rubiaceae) is described and illustrated from Hon Ba Nature Reserve, Khanh Hoa Province, southern Vietnam. It resembles L. inodorus and L. inodorus subsp. pubescens in leaf morphology, but differs from them in having shorter stipules, calyx tubes and corolla, and orange fruits. It is also similar to L. latifolius and L. calycinus in deeply disected calyx lobes and orange fruits, but differs from them by having persistent bracts and shorter calyx tubes. A table comparing the new species with its closest allies is provided.