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 7. Lasianthus cambodianus Pit. (1924: 382) — Fig. 22 (plate), Fig. 20 (map) Type: — CAMBODIA . Kompong Pseu Province , Montibus Knang Krepoeu , May 1870 , Pierre 1256 ( holotype P! [P04009927]; isotypes A! [A00096529], P! [P04009928]) . Specimens examined: — VIETNAM . Central: Kon Tum Province , Ngoc Linh Nature Reserve , 1067 m elev., 12 February 2017 , Tagane S. , Nagamasu H. , Nguyen V.N. , Hoang T.B. , Hoang T.S. , Yang C.J. , Kawakubo A. V 6361 ( DLU , FU ); Thua Thien Hue Province , Bach Ma National Park , 1193 m elev., 26 July 2019 , Dang V.S. & Naiki A. , Dang 417 ( VNM ) . Distribution: —Indochina region ( Cambodia ). In Vietnam , Lasianthus cambodianus occurs in Kon Tum and Thua Thien Hue. Habitat & Ecology: —Growing in shaded understory of evergreen forest, at 1000–1200 m elev. This species was collected in the forest habitats where dominated by species of Fabaceae , Fagaceae , Lauraceae , Rubiaceae , Myrtaceae , and Clusiaceae . Phenology: —Flowering from May to July. Fruits not seen. Vernacular name: —Xú hưƠng cambốt. Notes: — Lasianthus cambodianus was first recorded for the flora of Vietnam by Dang et al. (2017) . It is easily recognizable in the field in having lanceolate to oval-oblong leaves, midrib and nerves strongly prominent abaxially, secondary veins 15–18 on each side of midrib, bracts 6–8 mm long and bracteoles 4–6 mm long, and corolla white and lobes 5. Lasianthus cambodianus is closely related to L. giganteus Naiki (2015: 165) which was described in 2015 from Bokor National Park of Cambodia , but differs in its smaller leaves (20–26 × 5–9 cm vs. 21–31 × 9–11 cm ), shorter petioles ( 1–4 mm long vs. 15–25 mm long), smaller calyx (tubes 2 mm long, lobes 1 mm long vs. tube 2.5–3.5 mm long, lobes 2–2.5 mm long).