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 32. Lasianthus hongiaoensis V.S.Dang & Naiki (2021: 32) — Fig. 55 (plate), Fig 52 (map) Type: — VIETNAM . Lam Dong Province , Bidoup Nui Ba National Park , 1698 m elev., 24 February 2016 , Tagane S. , Nagamasu H. , Naiki A. , Dang V.S. , Nguyen V.N. , Wai J. V 4318 ( holotype VNM ![ VNM00042898 ]; isotypes FU !, VNM ! [ VNM00042899 , VNM00042900 ], the herbarium of Iriomote Station ( Japan )) . FIGURE 55. Lasianthus hongiaoensis V.S.Dang & Naiki (from V4318 , VNM): A. Branch with fruits, B. Close-up of expanding young leaves, C. Stipules, D. Abaxial leaf surfaces, E. Flower buds and young fruit, F. Inflorescence showing side view flowers, G–H. Fruits, J. Seeds ( E–F : photos by Shuichiro Tagane). Specimens examined: — VIETNAM . Central: Lam Dong Province , Bidoup Nui Ba National Park , 1698 m elev., 12°09’52.95’’N , 108°32’00.38’’E , in hill evergreen forests, 24 February 2016 , Tagane S. , Nagamasu H. , Naiki A. , Dang V.S. , Nguyen V.N. , Wai J. V 4318 ( FU , VNM , the herbarium of Iriomote Station ( Japan )); in the same location, 1490 m elev., 12°10’26.91’’N , 108°41’53.94’’E , in evergreen forests, 19 February 2014 , Toyama H., Tagane S. , Dang V.S. , Nagamasu H. , Naiki A. , Tran H. , Yang C.J. with Ngoc N.V. , Cuong N.Q. , Hieu H.N.P. , Loi X.N. V1842 ( FU , VNM , the herbarium of Iriomote Station ( Japan )) . Distribution: —Endemic to Vietnam (known only from the Bidoup Nui Ba National Park, Lam Dong Province ). Habitat & Ecology: —In hill evergreen forest at around 1400–1700 m elev. Phenology: —Flowering and fruiting from February to June. Vernacular name: —Xú hưƠng hòn giao. Note: — Lasianthus hongiaoensis is morphologically similar to L. hispidulus (Drake) Pit. (1924: 382) in the shape of leaves, flower color at anthesis, and blue fruits, but differs from the latter in having densely pubescent at branches and branchlets (vs. densely brown-villous), longer stipules ( 1–1.5 mm long vs. 1 mm long) and larger calyx ( 1.5–2 mm long vs. 1–1.5 mm long for tubes and 1.5–2 mm long vs. 1–1.5 mm long for lobes). It is also similar to L. nuichuaensis V.S.Dang & Naiki which was described from Nui Chua National Park, Ninh Thuan Province , Southern Vietnam , but differs from the latter by having plants covered by densely pubescent (vs. glabrous), larger leaves (7–9 × 2.5–3.5 cm vs. 5–7 × 1.5–3 cm ), fewer secondary veins (4–5 on each side of midrib vs. 5–6 on each side of midrib), larger calyx lobes ( 1.5–2 mm long vs. 0.5–1 mm long) and fruits with 5 (vs. 4) pyrenes.