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 34. Lasianthus japonicus Miq. (1867: 110) — Fig. 58 (plate), Fig. 57 (map) Type : — JAPAN . Nagasaki , October 1962 , S. Coll. 949 (isolectotype K! [K000763881]) . Lasianthus hartii Franch. (1899: 209) . Type :— CHINA . Fokien , La touche s.n. ( holotype P!). Lasianthus taiheizanensis Masam. & Suzuki (1930: 49) . Type :— CHINA . Taiwan , Taiheizan , Suzuki s.n. ( holotype TI!). Lasianthus japonicus var. lancilimbus (Merr.) H.S.Lo (1999: 99) . Type :— CHINA . Kwangtung , Nam Kwan Shan , Tsang 20293 ( holotype IBSC !; isotype K!, NY!). Lasianthus lucidus Blume (1826: 997) var. caudisepalus Deb & M.Gangop. (1991: 292) . Type:— INDIA . Assam , Cox & Hutchinson 499 ( holotype K!; isotype E!). Specimens examined: — VIETNAM . Norther: Vinh Phuc Province , Tam Dao National Park , 1124 m elev., 13 November 2018 , Dang V.S. & Naiki A. , Dang 236 & Dang 251 ( VNM , the herbarium of Iriomote Station ( Japan )) . Central: Thua Thien Hue Province , Bach Ma National Park , 1193 m elev., 26 July 2019 , Dang V.S. & Naiki A. , Dang 372 & Dang 415 ( VNM , the herbarium of Iriomote Station ( Japan )) . Distribution: —Widespread in tropical and subtropical regions in Asia ( China , India , Japan ). In Vietnam , Lasianthus japonicus occurs in Thua Thien Hue, anh Vinh Phuc . Habitat & Ecology: —Growing under evergreen forest and the edges of the forest at 900–1200 m elev. Phenology: —Flowering and fruiting from July to December. Vernacular name: —Xú hưƠng nhật. Notes: — Lasianthus japonicus is easily identified in the field in having oblong to oblong-lanceolate leaf blade, secondary veins 5–7 on each side of midrib, inflorescences congested-cymose, calyx purple, corolla white at anthesis, and fruits globose, blue to blackish when ripe.