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 19. Lasianthus eberhardtii Pit. (1924: 375) — Fig. 39 (plate), Fig. 37 (map) Type: — VIETNAM . Bac Kan Province , Ban Khuang , Eberhardt 4646 ( holotype P! [P02285249]; isotypes P! [P02285249, P02285249]) . Specimens examined: — VIETNAM . Northern: Lao Cai Province , Hoang Lien National Park , 870 m elev., 29 April 2016 , Naiki A. , Yahara T. , Toyama H. , Tagane S. , Nagamasu H. , Nguyen V.N. , Hoang T.B. , Hoang T.S. V 4669? ( DLU , FU ) . Central: Thanh Hoa Province , Thuong Xuan , 17 June 2016 , Trinh N.B. TH16-10 ( VAFS ) ; Distribution: —Endemic to Vietnam (currently known as Bac Kan , Lao Cai , Thai Nguyen , and Thanh Hoa ). Habitat & Ecology: —Growing in open shade, on less sandy ground in primary or secondary forest at 700–1500 m elev. Phenology: —Flowering and fruiting from June to November. Vernacular name: —Xú hưƠng eberhardt. Notes: — Lasianthus eberhardtii was described in 1924 from a Vietnamese specimen ( Eberhardt 4646 ). This species can easily be recognized in the field in having yellow hirsute branches, oblong leaf blade, tip pointed 12–15 mm long, secondary veins 9–12 on each side of midrib, bracts 10–20 mm long, and fruits 4 mm long, pyrenes 6. Lasianthus eberhardtii is closely related to L. harmandianus Pierre ex Pit. (1924: 376) which is endemic to Laos , but differs from the latter by having leaves long hairy along margin (vs. smooth margin), bracts 10–20 mm long (vs. 6.5 mm long), flowers grouped by 1–4 (vs. 8–12) and calyx 6, erect (vs. 5, reflexed).