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 43. Lasianthus larsenii H. Zhu (2000: 395) — Fig. 69 (plate), Fig. 67 (map) Type: — VIETNAM . Lam Dong Province , Da Lat City , Datanla waterwall, 12 July 1984 , D. D. Tirvengadum & Truong Quang Tam 1563 ( holotype AAU !) . Specimens examined: — VIETNAM . Central: Lam Dong Province , Bidoup Nui Ba National Park , 1698 m elev., 24 February 2016 , Tagane S. , Nagamasu H. , Naiki A. , Dang V.S. , Nguyen V.N. , Wai J. V 4340 ( VNM , FU ); in the same location, Da Lat City , Datanla waterfall, 1200 m elev., 20 July 2019 , Dang V.S. , Dang 427 ( VNM ) . Distribution: —Endemic to Vietnam (currently known only from Datanla waterfall area and Bidoup Nui Ba National Park of Da Lat City in Lam Dong Province ). Habitat & Ecology: —Growing in the hill of a secondary forest or along the edge of an evergreen forest at 1000–1500 m elev. Phenology: —Flowering and fruiting from June to November. Vernacular name: —Xú hưƠng larsen. Notes: — Lasianthus larsenii was described in 2000 from a Vietnamese specimen ( D. D. Tirvengadum & Truong Quang Tam 1563 ). It is easily identified in the field in having lanceolate leaves, secondary veins 9–10 on each side of midrib, calyx lobes 6, corolla white, and fruits subglobose, pilose. Lasianthus larsenii is very similar to L. chevalieri Pit. (1924: 384) which was distributed in Cambodia , China , Thailand , and Vietnam , but differs from the latter in having smaller leaves (6–10 × 2–3.5 vs. 11–16 × 3.5–5.5 cm ), smaller flowers, calyx tube 1–1.5 mm long (vs. 3–6 mm long) and calyx lobes 2 mm long (vs. 9–14 mm long).