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 53. Lasianthus nuichuaensis V.S.Dang & Naiki (2021: 17) — Fig. 81 (plate), Fig. 78 (map) Type: — VIETNAM . Ninh Thuan Province , Nui Chua National Park , 260 m elev., 16 August 2019 , Dang V.S. & Naiki A. , Dang 404 ( holotype VNM ! [ VNM00042926 ]; isotypes VNM ! [ VNM00042927 , VNM00042928 ], the herbarium of Iriomote Station (Japan)) . FIGURE 81. Lasianthus nuichuaensis V.S.Dang & Naiki (from Dang 404 , VNM): A. Fruiting branch, B. Stipules, C. Abaxial leaf surfaces, D–F. Close-up of inflorescences and flowers, G–H. Close-up of immature and mature fruits, I. Seeds. Specimens examined: — VIETNAM . Central: Ninh Thuan Province , Nui Chua National Park , 260 m elev., 11°44’06.53’’N , 109°13’15.12’’E , in secondary forest, 16 August 2019 , Dang V.S. & Naiki A. , Dang 404 ( VNM , the herbarium of Iriomote Station ( Japan )); in the same location, 256 m elev., 11°44’06.51’’N , 109°13’15.11’’E , in secondary forest, 01 December 2017 , Dang V.S. & Naiki A. N10147 ( KYO , VNM , the herbarium of Iriomote Station (Japan)) . Distribution: —Endemic to Vietnam (known only from the Nui Chua National Park, Ninh Thuan Province ). Habitat & Ecology: — This species is only known from the type locality in Nui Chua National Park , Ninh Thuan Province , southern Vietnam where it grows under the shade of the secondary forest at an elevation between 200–300 m . Phenology: —Flowering from June to September, fruiting from October to December Vernacular name: —Xú hưƠng núi chúa. Notes: — Lasianthus nuichuaensis is closely related to L. hispidulus (Drake) Pit. (1924: 382) in the shape of leaves, the number of secondary veins and inflorescences, but differs from the latter by having glabrous branches (vs. densely brown-villous), smaller leaves (5–7 × 1.5–3 cm vs. 7–10 × 3–5 cm ), bracts 1–1.5 mm long (vs. absent), calyx and corolla lobes 4 (vs. lobes 5), orange fruits (vs. blue) and drupe with 4 pyrenes (vs. 5 pyrenes).