Lasianthus annamicus Pit. (1924: 379)

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

1. Lasianthus annamicus Pit. (1924: 379) — Fig. 14 (plate), Fig. 15 (map)

Type: — VIETNAM. Lam Dong Province, Langbian Plateau , 800–1000 m elev., 30 April 1919, A. Chevalier 40425 (holotype P! [P02285255]) .

Specimens examined: — VIETNAM. Central: Lam Dong Province, Bidoup Nui Ba National Park, 50 km northeast of Dalat City , 1430 m elev., 12 July 2019, Dang V.S. & Hoang N.S., Dang 392 ( VNM) .

Distribution: —Endemic to Vietnam (currently known as Bidoup Nui Ba National Park in Lam Dong Province and Hon Ba Nature Reserve in Khanh Hoa Province).

Habitat & Ecology: —Growing under the shade of the primary forest on fertile soil at 800–1700 m elev.

Phenology: —Flowering and fruiting from April to September.

Vernacular name: —Xú hưƠng trung bộ.

Notes: — Lasianthus annamicus was described by Pitard (1924) from a Vietnamese specimen (A. Chevalier 40425) which was collected from Langbian Plateau of Lam Dong Province. It is characterized by having branches of brown ferruginous hirsute, leaf blade oblong-lanceolate, secondary veins 8–9 on each side of midrib, inflorescences axillary, cymose, 1–3-flowered, bracts 5 mm long, and calyx with lobes 6.

This species is closely related to L. attenuatus Jack based on fruit and inflorescences shape, and flower color at anthesis, but differs from the latter in having cuneate leaf base (vs. oblique, cordate or rounded bases in L. attenuatus ) and calyx with lobes 6 (vs. lobes 5 in L. attenuatus ).

Figures

FIGURE 14. Lasianthus annamicus Pit. (from Dang 392, VNM): A. Flowering branches, B. Stipules, C. Close-up of young branch and leaves, D. Abaxial leaf surfaces, E. Flower showing side view of calyx and corolla, F. Inflorescence showing lateral view of flower bud and corolla lobes.

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