Lasianthus attenuatus Jack (1823: 126)

Dang, Van-Son & Naiki, Akiyo, 2023, A revision of the genus Lasianthus Jack (Rubiaceae) from Vietnam, Phytotaxa 581 (1), pp. 1921-1935 : 1921-1935

2. Lasianthus attenuatus Jack (1823: 126) — Fig. 16 (plate), Fig. 15 (map)

Type: — INDONESIA. Sumatra, Bencoolen, Jack s.n. (isotype L! [L0000674]) .

Lasianthus wallichii Wight (1846: 503) . Type:— INDIA. Silhet, De Silva s.n. ex Wall. Cat. 8442 (isotypes K! [K001125525, K001125526, K001125527]).

Lasianthus thorelii Pit. (1924: 389) . Type:— LAOS. Penongs , Thorel 2161 (isotypes P! [P02285232, P02285233]).

Lasianthus tonkinensis (Drake) Pit. (1924: 376) . Type:— VIETNAM, Ha Noi City, Ba Vi National Park , Balansa 2656 (holotype P! [P02285231]; isotype K! [K000777039]).

Specimens examined: — VIETNAM. Northern: Ninh Binh Province, Cuc Phuong National Park, 365 m elev., 18 November 2018, Dang V.S. & Naiki A., Dang 285 & Dang 289 ( VNM, the herbarium of Iriomote Station (Japan )) . Central: Da Nang City, May–July, 1927, J. & M. S.Clemens 3776 (P); Quang Tri Province, 600 m elev., 14 March 1936, Poilane 25391 (P); Kon Tum Province, Dak Glei District , 1000–1100 m elev., 01 February 1947, Poilane 32958 (P); Khanh Hoa Province, Hon Ba Nature Reserve , 600 m elev., 18 June 2019, Dang V.S. & Hoang T.B.N., Dang 361 ( VNM); Gia Lai Province, Kon Chu Rang Nature Reserve , 920 m elev., 19 August 2019, Oguri E., Tagane S., Sugai K., Suyama Y. & Bui H.Q. V10327 & V10433 ( HN, KAG, MAK, VNM); in the same location, 1050 m elev., 21 April 2021, Dang V.S. & Truong B.V., Dang 462 ( VNM) . Southern: Dong Nai Province, Xuan Loc District, Nui Chua Chan , 650 m elev., 07 October 1931, Poilane 19478 (P) .

Distribution: —Widespread in tropical and subtropical regions in Asia ( Bhutan, Brunei, Cambodia, China, India, Indonesia, Japan, Laos, Malaysia, Myanmar, Nepal, Papua New Guinea, Philippines, Thailand). In Vietnam, Lasianthus attenuatus occurs in Da Nang, Dak Nong, Dong Nai, Gia Lai, Ha Noi, Khanh Hoa, Kon Tum, Ninh Binh, Quang Tri, Thai Nguyen, and Tuyen Quang.

Habitat & Ecology: —In primary and secondary montane forests or on the edge of the forest at 300–1200 m elev.

Phenology: —Flowering and fruiting from June to November.

Vernacular name: —Xú hưƠng bắc bộ, Xú hưƠng wallich.

Notes: —Two Vietnamese species, L. tonkinensis (Drake) Pit. (1924: 376) and L. wallichii Wight (1846: 503) were treated as synonyms of L. attenuatus by Zhu et al. (2012).

This species is easily recognizable in the field in having oblong or elliptic-lanceolate leaves, oblique, cordate or rounded leaf base, secondary veins 6–8 on each side of midrib, bracts 5–13 mm long, and fruits globose or ovoid, blue when ripe.

Figures

FIGURE 15. Distribution maps of Lasianthus annamicus, L. attenuatus, L. bachmaensis and L. bidoupensis.

FIGURE 16. Lasianthus attenuatus Jack (A–D from Dang 285 and E–I from Dang 289, VNM and the herbarium of Iriomote Station (Japan)): A. Habit, B. Fruiting branch, C. Stipules, D.Abaxial leaf surfaces, E. Inflorescence showing lateral view bracts and flower buds, F. Flower and buds, G–H. Young and mature fruits, I. Mature fruits.