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 6. Lasianthus caeruleus Pitard (1924: 390) — Fig. 21 (plate), Fig. 20 (map) Type: — VIETNAM . Lao Cai Province , Sapa , 1400–1500 m elev., 6 December 1913 , A. Chevalier 29398 ( holotype P! [P04009929]) . Specimens examined: — VIETNAM . Central: Thua Thien Hue Province , Bach Ma National Park , 1193 m elev., 26 July 2019 , Dang V.S. & Naiki A. , Dang 407 & Dang 411 ( VNM , the herbarium of Iriomote Station (Japan)); Da Nang City, Ba Na Nature Reserve , 1480 m elev., 26 June 2019 , Dang V.S. & Hoang N.S. , Dang 373 ( VNM ); in the same location, 1489 m elev., 27 July 2019 , Dang V.S. & Naiki A. , Dang 420 ( VNM , the herbarium of Iriomote Station ( Japan )) . Distribution: —Endemic to Vietnam (currently known as Sapa District in Lao Cai Province , Bach Ma National Park in Thua Thien Hue Province, Ba Na Nature Reserve in Da Nang City, and Kon Chu Rang Nature Reserve in Gia Lai Province ). FIGURE 21. Lasianthus caeruleus Pit. (A–G from Dang 411 and H–J from Dang 407 , VNM and the herbarium of Iriomote Station (Japan)): A. Habit, B. Fruiting branch, C. Stipules, D. Abaxial leaf surfaces, E–G. Inflorescence showing lateral view flowers and buds, H–J. Young fruits. Habitat & Ecology: —Growing in primary and secondary montane forests or on the edge of the forest, on gravel soil at 1200–1600 m elev. This species was found in the forest habitats where Lasitnhus japonicus Miq. (1867: 110) , Croton sp. , Phyllanthus reticulatus Poir. (1804: 298) , Streblus indicus (Bureau) Corner (1962: 226) , Melastoma malabathricum L. (1753: 390), Anomianthus sp. , Rubus pluribracteatus L.T.Lu & Boufford (2003: 255) are dominant. Phenology: —Flowering and fruiting from June to December. Vernacular name: —Xú hưƠng lam. Notes: — Lasianthus caeruleus was described in 1924 from a Vietnamese specimen ( A. Chevalier 29398 ). This species was characterized in the field as having yellowish-green, velvety branches and then black, pubescent ones.