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 29. Lasianthus hirsutus (Roxb.) Merr. (1952: 229) — Fig. 51 (plate), Fig. 52 (map) Type: — BANGLADESH . Chittagong , sp.no . 139 ( lectotype BM! [ BM000848507 ], designated by Merrill 1952 ) . Triosteum hirsutum Roxb. (1824: 180) . Type : — BANGLADESH . Chittagong , sp.no . 139 ( lectotype BM! [ BM000848507 ], designated by Merrill 1952 ). Lasianthus cyanocarpus Jack (1823: 125) var. asperatus Pierre ex Pit. (1924: 381) . Type :— VIETNAM . Dong Nai Province , Bien Hoa District , Pierre 3256 ( syntype L! [L0305709]). Lasianthus cyanocarpus var. lucidulus Pierre ex Pit. (1924: 382) . Type :— VIETNAM . Dong Nai Province , Bien Hoa District , September 1869 , Pierre s.n. ( syntype L! [L0310260]). Specimens examined: — VIETNAM . Central: Ninh Thuan Province , Thuan Nam District , Ca Na , 12 November 1923 , Poilane 8608 ( VNM ); Khanh Hoa Province , Hon Ba Nature Reserve , 1000 m elev., 19 April 2018 , Dang V.S. & Hoang N.T.B.N. , Dang 184 ( VNM , the herbarium of Iriomote Station (Japan)); in the same location, 1502 m elev., 15 June 2019 , Dang V.S. & Hoang N.T.B.N. , Dang 353 ( VNM ) . Southern: Dong Nai Province , Bien Hoa District , September 1865 , Pierre 3256a ( VNM ); in the same location, Xuan Loc District , Nui Chua Chan , 650 m elev., 07 October 1930 , Poilane 19479 (P) . Distribution: —Widespread in tropical and subtropical regions in Asia ( Bangladesh , Cambodia , China , Japan , India , Indonesia , Laos , Malaysia , Myanmar , Papua New Guinea , Philippines , Thailand ). In Vietnam , Lasianthus hirsutus occurs in Dong Nai , Khanh Hoa , Kien Giang , Lam Dong , Ninh Binh , Ninh Thuan , and Thua Thien Hue. FIGURE 50. Lasianthus hatinhensis V.S.Dang, Naiki & Yahara (from V5875 , VNM): A. Branch with flowers, B. Close-up of young branch and leaves, C. Stipules, D. Abaxial leaf surfaces, E–G. Inflorescence showing side view buds and flowers, H–I. Fruits, J. Seeds ( A, E, G : photos by Shuichiro Tagane). FIGURE 51. Lasianthus hirsutus (Roxb.) Merr. (A–C from Dang 184 and D–I from Dang 353 , VNM and the herbarium of Iriomote Station (Japan)): A. Branch with flower buds, B. Stipules, C. Abaxial leaf surfaces, D–F. Inflorescence showing side view bracts, buds and flowers, G. young fruit, H–I. Mature fruits. FIGURE 52. Distribution maps of Lasianthus hirsutus , L. hispidulus , L. honbaensis and L. hongiaoensis . Habitat & Ecology: —Growing under the shade of the primary or secondary montane forest, sometimes on the edge of the forest, 300–1600 m elev. Phenology: —Flowering and fruiting from September to April of the next year. Vernacular name: —Xú hưƠng quả lam. Notes: — Lasianthus hirsutus is easily recognizable in the field from other Lasianthus in having usually stiff spreading rusty-hirsute branches, oblong to oblong-lanceolate leaves, secondary veins 7–10 on each side of midrib, bracts very large and leaf-like, 2–3.5 cm long, hirsute on both surfaces, flowers white, fruits ovoid to globose, blue when ripe. Lasianthus hirsutus is similar to L. cyanocarpus Jack (1823: 125) which was selected as the type of the genus Lasianthus based on its bracts, but differs from the latter in having larger leaves 12–20 × 4–6 cm (vs. 8–13.5 × 2.5–4.5 cm ), longer petioles 10–15 mm long (vs. 2 mm long), calyx obconical with densely long hirsute (vs. campanulate with tomentose) and pyrenes 5 (vs. 4).