A revision of the genus Lasianthus Jack (Rubiaceae) from Vietnam Author Dang, Van-Son 0000-0001-8681-4141 Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & Institute of Tropical Biology, Vietnam Academy of Science and Technology, 85 Tran Quoc Toan Street, District 3, Ho Chi Minh City, Vietnam. & Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam. & dvsonitb @ gmail. com; https: // orcid. org / 0000 - 0001 - 8681 - 4141 dvsonitb@gmail.com Author Naiki, Akiyo 0000-0002-3235-2823 Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & naiki @ lab. u-ryukyu. ac. jp; https: // orcid. org / 0000 - 0002 - 3235 - 2823 * Author for correspondence naiki@lab.u-ryukyu.ac.jp text Phytotaxa 2023 2023-01-26 581 1 1921 1935 http://dx.doi.org/10.1094/PDIS-04-22-0755-PDN journal article 10.11646/phytotaxa.581.1.1 1179-3163 7571550 64. Lasianthus sonlangensis V.S.Dang, Vuong & Quan (2022: 25) — Fig. 95 (plate), Fig. 94 (map) Type: — VIETNAM . Gia Lai Province , K’Bang District , Son Lang Commune , Kon Chu Rang Nature Reserve , 900–1100 m elev., 22 April 2021 , Van-Son Dang , Ba Vuong Truong , Minh Quan Dang & Nghia Son Hoang , Dang 465 ( holotype VNM ! [ VNM00042935 ]; isotypes HN !, VNM ! [ VNM00042936 , VNM00042937 ]) . Specimens examined: — VIETNAM . Central: Gia Lai Province , K’Bang District , Son Lang Commune , Kon Chu Rang Nature Reserve , 1080 m elev., 25 April 2021 , Van-Son Dang , Ba Vuong Truong , Minh Quan Dang & Nghia Son Hoang , Dang 465a ( VNM ) . Distribution: —Endemic to Vietnam (currently known only from Kon Chu Rang Nature Reserve of Gia Lai Province ). Habitat & Ecology: — Lasianthus sonlangensis occurs in the understory of the primary evergreen forest at an elevation of 900–1100 m . Phenology: —Flowering and fruiting from March to September. Vernacular name: —Xú hưƠng sƠn lạng. Notes: — Lasianthus sonlangensis was described from a Vietnamese specimen ( Dang 465 ) by Dang et al. (2022) . It is similar to L. caeruleus Pit. (1924: 390) in the shape of leaves and inflorescences, but differs from the latter in having more than secondary veins, shorter petioles, bracts present (vs. absent), larger calyx and corolla lobes 4 (vs. 5).