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 68. Lasianthus thuyanae V.S. Dang & Naiki (2020: 49) — Fig. 100 (plate), Fig. 99 (map) Type: — VIETNAM . Ha Noi City, Ba Vi National Park , 50 km west of Ha Noi city center, 1267 m elev., 17 November 2018 , Dang V.S. & Naiki A. , Dang 277 ( holotype VNM ! [ VNM00042943 ]; isotypes HN !, KYO !, VNM ! [ VNM00042944 ], VNMN!) . Specimens examined: — VIETNAM . Northern: Ha Noi City , Ba Vi National Park , 1267 m elev., 17 November 2018 , in evergreen forest, Dang V.S. & Naiki A. , Dang 277a ( VNM , the herbarium of Iriomote Station ( Japan )) . FIGURE 100. Lasianthus thuyanae V.S.Dang & Naiki (from Dang 277 , VNM and the herbarium of Iriomote Station (Japan)): A. Branch, B. Close-up of expanding young leaves, C. Stipules, D. Abaxial leaf surfaces, E–H. Inflorescence showing lateral view buds flowers, I. Young fruit, J. Mature fruit, K. Seeds. Distribution: —Endemic to Vietnam (currently known only from Ba Vi National Park of Ha Noi City). Habitat & Ecology: —Growing under the canopy of the evergreen forest at 1000–1250 m elev. The forest habitats where collected Lasianthus thuyanae dominated by species of Lauraceae , Fagaceae , Fabaceae , and Rubiaceae . Phenology: —Flowering and fruiting from July to December. Vernacular name: —Xú hưƠng thúy an. Notes: — Lasianthus thuyanae was described as new from a Vietnamese specimen ( Dang 277 ) by Dang & Naiki (2020) . It is characterized by having densely brown tomentose on branches, secondary veins 5–6 on each side of midrib, flowers sessile, calyx dark purple and corolla white, and fruits ovoid or globose, blue when ripe. This species is similar to L. curtisii King & Gamble (1904: 128) in the shape of the leaves, the number of secondary veins, and fruit color, but differs from the latter in having brown tomentose hairs on branches and petioles (vs. villose), stipules 1.7–2 mm long (vs. 1–1.5 mm long), corolla tubes 11–15 mm long (vs. 7–8 mm long), and calyx dark purple (vs. greenish white).