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 17. Lasianthus dalatensis Wernham (1921: 138) — Fig. 36 (plate), Fig. 37 (map) Type: — VIETNAM . Lam Dong Province , Langbian Plateau , 1524 m elev., April 1918 , Boden Kloss s.n. ( holotype BM! [ BM000945601 ]) . Specimens examined: — VIETNAM . Central: Lam Dong Province , Bidoup Nui Ba National Park , 50 km northeast of Dalat City , 1490 m elev., 19 November 2014 , Toyama H. , Tagane S. , Dang V.S. , Nagamasu H. , Naiki A. , Tran H. , Yang C.J. V1939 ( FU , VNM , the herbarium of Iriomote Station (Japan)); Khanh Hoa Province , Hon Ba Nature Reserve , 1512 m elev., 21 July 2018 , Dang V.S. & Hoang N.T.B.N. , Dang 189 ( 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 in primary or secondary montane forests, rarely at the edge of a forest, 900–1600 m elev. Phenology: —Flowering and fruiting from July to November. Vernacular name: —Xú hưƠng đà lạt. Notes: — Lasianthus dalatensis was described by Wernham in 1921 from a Vietnamese specimen ( Boden Kloss s.n. ). This species is characterized by having an elliptic-lanceolate leaf blade, glabrous on both surfaces, secondary veins 7–9 on each side of midrib, and flowers crimson to pink, and ultimately white. Lasianthus dalatensis morphologically resembles L. yaharae V.S.Dang, Tagane & H.Tran (2015: 352) which was discovered in 2015 from Hon Ba Nature Reserve of Khanh Hoa Province , but differs from the latter in having more number of secondary veins, ultimately white flowers in anthesis and smaller calyx, corolla tube and corolla lobes.