Lasianthus hatinhensis V. S. Dang, Naiki & Yahara 2021

28. Lasianthus hatinhensis V.S.Dang, Naiki & Yahara (2021: 30) — Fig. 50 (plate), Fig. 47 (map) Type: — VIETNAM. Ha Tinh Province, Vu Quang National Park, 1758 m elev., 23 June 2016, Yahara T., Nguyen N., Toyama H., Tagane S., Okabe N., Nguyen H. V 5875 (holotype VNM! [VNM00042894]; isotypes DLU!, FU!, the herbarium of Iriomote Station (Japan)). Specimens examined: — VIETNAM. Central: Ha Tinh Province, Vu Quang National Park, 1758 m elev., 18˚11’41.09”N, 105˚23’06.08’’E, in lower montane forest, 23 June 2016, Yahara T., Nguyen N., Toyama H., Tagane S., Okabe N., Nguyen H. V 5875 (DLU, VNM, the herbarium of Iriomote Station (Japan)). Distribution: —Endemic to Vietnam (known only from the Vu Quang National Park, Ha Tinh Province). Habitat & Ecology: —Moist evergreen forest in shaded places at 1600–1800 m elev. Phenology: —Flowering and fruiting from March to July. Vernacular name: —Xú hưƠng hà tĩnh. Note: — Lasianthus hatinhensis is similar to L. micranthus Hook.f. (1880: 190) in the shape of leaves and pedunculate congested cymes, but differs from the latter in having 4 calyx lobes (vs. 5), larger calyx tubes (1.5–2 mm long vs. 1 mm long), smaller corolla lobes (1–2 mm long vs. 2–2.5 mm long) and fruits with 4 (vs. 5) pyrenes. It is also similar to L. sapaensis V.S. Dang & Naiki (2019: 39) which was discovered at Hoang Lien National Park, northern Vietnam, but differs from the latter in having fewer secondary veins (5–6 on each side of midrib vs. 6–7 on each side of midrib), calyx and corolla lobes 4 (vs. 5), smaller calyx (1.5–2 mm long vs. 2–3 mm long for tubes and 1–1.5 mm long vs. 1.5–2 mm long for lobes) and corolla (4–5 mm long vs. 7–8 mm long for tubes and 1–2 mm long vs. 3–4 mm long for lobes), and fruits with 4 (vs. 5) pyrenes.Published as part of Dang, Van-Son & Naiki, Akiyo, 2023, A revision of the genus Lasianthus Jack (Rubiaceae) from Vietnam, pp. 1921-1935 in Phytotaxa 581 (1) on pages 1921-1935, DOI: 10.11646/phytotaxa.581.1.1, http://zenodo.org/record/757155