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 67. Lasianthus thuathienhuensis V.S.Dang & Naiki (2021: 46) — Fig. 98 (plate), Fig. 99 (map) Type: — VIETNAM . Thua Thien Hue Province , Bach Ma National Park , 1293 m elev., 26 July 2019 , Dang V.S. & Naiki A. , Dang 419 ( holotype VNM ! [ VNM00042940 ]; isotypes VNM ! [ VNM00042941 , VNM00042942 ], the herbarium of Iriomote Station (Japan)) . Specimens examined: — VIETNAM . Central : Thua Thien Hue Province , Bach Ma National Park , 1293 m elev., 16°11’76.06’’N, 107°51’32.04’’E , in evergreen forests, 26 July 2019 , Dang V.S. & Naiki A. , Dang 419 ( VNM , the herbarium of Iriomote Station (Japan)); in the same location, 1293 m elev., 16°11’76.06’’N, 107°51’32.04’’E , in evergreen forests, 26 July 2019 , Dang V.S. & Naiki A. , Dang 414 ( VNM , the herbarium of Iriomote Station ( Japan )) . Kon Tum Province , Ngoc Linh Nature Reserve , 1376 m elev., 15˚10’07.04”N, 107˚45’43.04’’E, 13 February 2017 , Tagane S., Nagamasu H., Nguyen V.N. , Hoang T.B., Hoang T.S., Yang C.J., Kawakubo A. V6480 ( DLU , FU ). Gai Lai , Kon Ka Kinh National Park , 1260 m elev., 14˚20’09.06”N, 108˚25’23.07’’E, 22 April 2021 , Dang V.S. , Le T.K.N. & Truong B.V. , Dang 467 ( VNM ) . Distribution: —Endemic to Vietnam (known from the Bach Ma National Park in Thua Thien Hue Province, Kon Ka Kinh National Park in Gia Lai Province , and Ngoc Linh Nature Reserve in Kon Tum Province ). Habitat & Ecology: —In evergreen forests at 1000–1400 m elev. Phenology: —Flowering and fruiting from April to July. Vernacular name: —Xú hưƠng thừa thiên huḗ. Notes: — Lasianthus thuathienhuensis is similar to L. lacduongensis V.S.Dang & Naiki which was described from Bidoup Nui Ba National Park of Lam Dong Province in having the shape of leaves, stipules, and number of pyrenes, but differs from the latter in having longer petioles ( 8–10 mm long vs. 5–7 mm ), fewer secondary veins (5–7 on each side of midrib vs. 8–10 on each side of midrib) and smaller calyx lobes ( 0.2–0.3 mm long vs. 0.3–0.5 mm long).