Lasianthus oblongilobus H.Zhu (2002: 400)

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

54. Lasianthus oblongilobus H.Zhu (2002: 400) — Fig. 82 (plate), Fig. 78 (map)

Type: — VIETNAM. Khanh Hoa Province, Khanh Son District , 1500–1600 m elev., 22 April 1997, Averyanov L., Nguyen Q.B., Nguyen T.H. VH 4153 (holotype AAU!) .

Specimens examined: — VIETNAM. Central: Lam Dong Province, Bidoup National Park , 1655 m elev., 19 November 2014, Toyama H., Tagane S., Dang V.S., Nagamasu H., Naiki A., Tran H., Yang C.J. V1923 ( FU, VNM) ; in the same location, 1658 m elev., 26 November 2017, Dang V.S. & Naiki A. N10109 ( VNM, the herbarium of Iriomote Station (Japan )) ; Khanh Hoa Province, Hon Ba Nature Reserve, 30 km west of Nha Trang City , 1518 m elev., 24 July 2018, Dang V.S. & Hoang N.T.B.N., Dang 194 ( VNM) .

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

Habitat & Ecology: —Growing under the canopy of an evergreen forest or the edge of a montane forest at 1200– 1700 m elev.

Phenology: —Flowering and fruiting from July to December.

Vernacular name: —Xú hưƠng đài thuôn.

Notes: — Lasianthus oblongilobus was described as new from a Vietnamese specimen by Zhu (2002). This is characterized by having elliptic-lanceolate leaves, secondary veins 5–6 on each side of midrib, calyx lobes oblong and 1.5–2 mm long.

Additional fruit morphology for L. oblongilobus : fruits globose, 4–5 mm diam., smooth, glabrous, crowned by calyx lobes, yellowish-orange when ripe; pyrenes 4. Seed ovoid, 2–3 mm long, irregular sulcate on the abaxial face, blackish brown when dry.

Figures

FIGURE 78. Distribution maps of Lasianthus nghiasonii, L. nhatrangensis, L. ngoclinhensis, L. nuichuaensis and L. oblongilobus.

FIGURE 82. Lasianthus oblongilobus H.Zhu (from N10109, VNM and the herbarium of Iriomote Station (Japan)): A. Branch, B. Closeup of expanding young leaves, C. Stipules, D.Abaxial leaf surfaces, E–F. Inflorescence showing side view flower buds, G–I. Young fruits, J. Mature fruits.