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 55. Lasianthus phamhoangii V.S.Dang & Naiki (2021: 28) — Fig. 83 (plate), Fig. 84 (map) Type: — VIETNAM . Khanh Hoa Province , Hon Ba Nature Reserve , 617 m elev., 22 November 2014 , Toyama H. , Tagane S. , Dang V.S. , Nagamasu H. , Naiki A. , Tran H. , Yang C.J. with Hieu H.N.P. V1962 ( holotype VNM ! [ VNM00042929 ]; isotypes FU !, VNM ! [ VNM00042930 , VNM00042931 ], the herbarium of Iriomote Station (Japan)) . Specimens examined: — VIETNAM . Central: Khanh Hoa Province , Hon Ba Nature Reserve , 617 m elev., 12°06’39.77’’N , 108°58’59.23’’E , in evergreen forests, 22 November 2014 , Toyama H. , Tagane S. , Dang V.S. , Nagamasu H. , Naiki A. , Tran H. , Yang C.J. with Hieu H.N.P. V1962 ( FU , VNM , the herbarium of Iriomote Station (Japan)); in the same location, 919 m elev., 12°06’46.88’’N , 108°58’14.43’’E , in evergreen forests, 21 February 2014 , Toyama H. , Dang V.S. , Tagane S. , Fuse K. , Yahara T. , Nagamasu H. , Tran H. with Ngoc N.V. , Cuong N.Q. , Thach N.D. , Hieu H.N.P. V 846 ( FU , VNM , the herbarium of Iriomote Station ( Japan )) . Distribution: —Endemic to Vietnam (known only from the Hon Ba Nature Reserve, Khanh Hoa Province ). Habitat & Ecology: —Primary or secondary forests at elevations between 600–1000 m . Phenology: —Flowering and fruiting from April to September. Vernacular name: —Xú hưƠng phạm hoàng hộ. Notes: — Lasianthus phamhoangii is similar to L. hirsutus (Roxb.) Merr. (1924: 382) in having rusty hirsute on branches and branchlets, the shape of leaves, inflorescences and fruit color but distinguished by its secondary veins (12–16 on each side of midrib vs. 7–10 on each side of midrib), shorter stipules ( 6–7.5 mm long vs. 8–10 mm long), calyx and corolla lobes 4 (vs. 5), larger calyx ( 2.5–3.5 mm long vs. 1 mm long for tubes and 1.5–2 mm long vs. 2.5 mm long for lobes) and corolla ( 12–15 mm long vs. 10–12 mm long for tubes and 3–5 mm long vs. 3 mm long for lobes) and fruits with 4 (vs. 5) pyrenes.