Lasianthus formosensis Matsum. 1901

24. Lasianthus formosensis Matsum. (1901: 17) — Fig. 45 (plate), Fig. 42 (map) Type: — CHINA. Taiwan, Y. Tashiro & S. Tanaka 131 (holotype TI!). Lasianthus tenuicaudatus Merr. (1931: 324). Type:— CHINA. Guangdong, Y. Tsiang 822 (holotype IBSC!). Lasianthus kwangsiensis Merr. ex H.L.Li (1943: 458). Type:— THAILAND. Chanthaburi, Khao Soi Dao, 12 December 1924, Kerr 9618 (holotype K! [K000777028]; isotype E! [E00327853]). Specimens examined: — VIETNAM. Northern: Ha Noi City, Ba Vi National Park, 1267 m elev., 17 November 2018, Dang V.S. & Naiki A., Dang 280 (VNM, the herbarium of Iriomote Station (Japan)); in the same location, 1268 m elev., 17 November 2018, Dang V.S. & Naiki A., Dang 282 (VNM, the herbarium of Iriomote Station (Japan)); Ninh Binh Province, Cuc Phuong National Park, 365 m elev., 18 November 2018, Dang V.S. & Naiki A., Dang 287 (VNM, the herbarium of Iriomote Station (Japan)); in the same location, 368 m elev., 18 November 2018, Dang V.S. & Naiki A., Dang 288 (VNM, the herbarium of Iriomote Station (Japan)). Distribution: —Widespread in tropical and subtropical regions in Asia (China, Japan, Thailand). In Vietnam, Lasianthus formosensis occurs in Ha Noi, Ha Tinh, Ninh Binh and Thua Thien Hue. Habitat & Ecology: —Growing in secondary montane forest, the edge of the forest, and an open area at 300–1300 m elev. Phenology: —Flowering and fruiting from June to December. Vernacular name: —Xú hưƠng nhiễu hoa. Notes: — Lasianthus formosensis was clarified in the revisions by Zhu (2001) and Zhu & Taylor (2011). This species can be recognized in the field in having oblong to ovate-elliptic leaves, secondary veins 6–7 on each side of midrib, flowers grouped by 6–9, lanceolate calyx lobes longer than the tube, and fruit ovoid-globose, blue when ripe. ; 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, .