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 1. Lasianthus annamicus Pit. (1924: 379) — Fig. 14 (plate), Fig. 15 (map) Type: — VIETNAM . Lam Dong Province , Langbian Plateau , 800–1000 m elev., 30 April 1919 , A. Chevalier 40425 ( holotype P! [P02285255]) . Specimens examined: — VIETNAM . Central : Lam Dong Province , Bidoup Nui Ba National Park , 50 km northeast of Dalat City , 1430 m elev., 12 July 2019 , Dang V.S. & Hoang N.S. , Dang 392 ( VNM ) . Distribution: —Endemic to Vietnam (currently known as Bidoup Nui Ba National Park in Lam Dong Province and Hon Ba Nature Reserve in Khanh Hoa Province ). Habitat & Ecology: —Growing under the shade of the primary forest on fertile soil at 800–1700 m elev. Phenology: —Flowering and fruiting from April to September. Vernacular name: —Xú hưƠng trung bộ. Notes: — Lasianthus annamicus was described by Pitard (1924) from a Vietnamese specimen ( A. Chevalier 40425 ) which was collected from Langbian Plateau of Lam Dong Province . It is characterized by having branches of brown ferruginous hirsute, leaf blade oblong-lanceolate, secondary veins 8–9 on each side of midrib, inflorescences axillary, cymose, 1–3-flowered, bracts 5 mm long, and calyx with lobes 6. This species is closely related to L. attenuatus Jack based on fruit and inflorescences shape, and flower color at anthesis, but differs from the latter in having cuneate leaf base (vs. oblique, cordate or rounded bases in L. attenuatus ) and calyx with lobes 6 (vs. lobes 5 in L. attenuatus ).