Lasianthus larsenii H. Zhu (2000: 395)

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

43. Lasianthus larsenii H. Zhu (2000: 395) — Fig. 69 (plate), Fig. 67 (map)

Type: — VIETNAM. Lam Dong Province, Da Lat City, Datanla waterwall, 12 July 1984, D. D. Tirvengadum & Truong Quang Tam 1563 (holotype AAU!) .

Specimens examined: — VIETNAM. Central: Lam Dong Province, Bidoup Nui Ba National Park , 1698 m elev., 24 February 2016, Tagane S., Nagamasu H., Naiki A., Dang V.S., Nguyen V.N., Wai J. V 4340 ( VNM, FU); in the same location, Da Lat City, Datanla waterfall, 1200 m elev., 20 July 2019, Dang V.S., Dang 427 ( VNM) .

Distribution: —Endemic to Vietnam (currently known only from Datanla waterfall area and Bidoup Nui Ba National Park of Da Lat City in Lam Dong Province).

Habitat & Ecology: —Growing in the hill of a secondary forest or along the edge of an evergreen forest at 1000–1500 m elev.

Phenology: —Flowering and fruiting from June to November.

Vernacular name: —Xú hưƠng larsen.

Notes: — Lasianthus larsenii was described in 2000 from a Vietnamese specimen (D. D. Tirvengadum & Truong Quang Tam 1563). It is easily identified in the field in having lanceolate leaves, secondary veins 9–10 on each side of midrib, calyx lobes 6, corolla white, and fruits subglobose, pilose.

Lasianthus larsenii is very similar to L. chevalieri Pit. (1924: 384) which was distributed in Cambodia, China, Thailand, and Vietnam, but differs from the latter in having smaller leaves (6–10 × 2–3.5 vs. 11–16 × 3.5–5.5 cm), smaller flowers, calyx tube 1–1.5 mm long (vs. 3–6 mm long) and calyx lobes 2 mm long (vs. 9–14 mm long).

Figures

FIGURE 67. Distribution maps of Lasianthus lamdongensis, L. lancifolius, L. larsenii, L. latifolius and L. lecomtei.

FIGURE 69. Lasianthus larsenii H.Zhu (A, C–D & J from V7779, G from V4340 and B, E–F & H–I from Tirvengadum & Truong 1563, VNM, FU and AAU): A. Branch with fruit, B. Close-up of expanding young leaves, C. Stipules, D–E. Abaxial leaf surfaces, F–G. Calyx, H–I. Inflorescences, J. Mature fruit (A, C, D, G & J: photos by Shuchiro Tagane).