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 28. Lasianthus hatinhensis V.S.Dang, Naiki & Yahara (2021: 30) — Fig. 50 (plate), Fig. 47 (map) Type: — VIETNAM . Ha Tinh Province , Vu Quang National Park , 1758 m elev., 23 June 2016 , Yahara T. , Nguyen N. , Toyama H. , Tagane S. , Okabe N. , Nguyen H. V 5875 ( holotype VNM ! [ VNM00042894 ]; isotypes DLU !, FU !, the herbarium of Iriomote Station (Japan)) . Specimens examined: — VIETNAM . Central: Ha Tinh Province , Vu Quang National Park , 1758 m elev., 18˚11’41.09”N, 105˚23’06.08’’E, in lower montane forest, 23 June 2016 , Yahara T. , Nguyen N. , Toyama H. , Tagane S. , Okabe N. , Nguyen H. V 5875 ( DLU , VNM , the herbarium of Iriomote Station ( Japan )) . Distribution: —Endemic to Vietnam (known only from the Vu Quang National Park, Ha Tinh Province ). Habitat & Ecology: —Moist evergreen forest in shaded places at 1600–1800 m elev. Phenology: —Flowering and fruiting from March to July. Vernacular name: —Xú hưƠng hà tĩnh. Note: — Lasianthus hatinhensis is similar to L. micranthus Hook.f. (1880: 190) in the shape of leaves and pedunculate congested cymes, but differs from the latter in having 4 calyx lobes (vs. 5), larger calyx tubes ( 1.5–2 mm long vs. 1 mm long), smaller corolla lobes ( 1–2 mm long vs. 2–2.5 mm long) and fruits with 4 (vs. 5) pyrenes. It is also similar to L. sapaensis V.S. Dang & Naiki (2019: 39) which was discovered at Hoang Lien National Park, northern Vietnam , but differs from the latter in having fewer secondary veins (5–6 on each side of midrib vs. 6–7 on each side of midrib), calyx and corolla lobes 4 (vs. 5), smaller calyx ( 1.5–2 mm long vs. 2–3 mm long for tubes and 1–1.5 mm long vs. 1.5–2 mm long for lobes) and corolla ( 4–5 mm long vs. 7–8 mm long for tubes and 1–2 mm long vs. 3–4 mm long for lobes), and fruits with 4 (vs. 5) pyrenes.