Lasianthus vietnamensis V.S.Dang, Naiki & Tagane (2021: 50)

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

71. Lasianthus vietnamensis V.S.Dang, Naiki & Tagane (2021: 50) — Fig. 103 (plate), Fig. 104 (map)

Type: — VIETNAM. Kon Tum Province, Ngoc Linh Nature Reserve , 1365 m elev., 14 February 2017, Tagane S., Nagamasu H., Nguyen V.N., Hoang T.B., Hoang T.S., Yang C.J., Kawakubo A. V 6668 ( holotype VNM! [ VNM00042945 ]; isotypes DLU!, FU!, the herbarium of Iriomote Station ( Japan)) .

Specimens examined: — VIETNAM. Central: Kon Tum Province, Ngoc Linh Nature Reserve , 1365 m elev., 15˚12’24.02”N, 107˚46’10.04’’E, 14 February 2017, Tagane S., Nagamasu H., Nguyen V.N., Hoang T.B., Hoang T.S., Yang C.J., Kawakubo A. V6668 ( DLU, FU, VNM, the herbarium of Iriomote Station ( Japan)); in the same location, 1070 m elev., 15˚10’05.07”N, 107˚45’23.06’’E, 12 February 2017, Tagane S., Nagamasu H., Nguyen V.N., Hoang T.B., Hoang T.S., Yang C.J., Kawakubo A. V 6422 ( DLU, FU, the herbarium of Iriomote Station ( Japan)) .

Distribution: —Endemic to Vietnam (known only from the Ngoc Linh Nature Reserve, Kon Tum Province).

Habitat & Ecology: —In primary forests at 1000–1400 m elev.

Phenology: —Flowering and fruiting from February to June.

Vernacular name: —Xú hưƠng việt.

Notes: — Lasianthus vietnamensis is similar to L. caeruleus Pit. (1924: 390) which is endemic to Vietnam in the shape of leaves and inflorescence type, but differs from the latter in having larger leaves (8–14 × 1.5–3.5 cm vs. 4.5–7 × 0.8–1.5 cm), more secondary veins (5–7 on each side of midrib vs. 4–5 on each side of midrib), longer petioles ( 5–10 mm long vs. 4–5 mm long), bracts 0.7–1 mm long (vs. absent) and larger calyx ( 2.5–3 mm long vs. tube ca. 1 mm long for tubes, 0.5–1 mm long vs. 0.5 mm long for lobes), yellowish-white (vs. blue) when ripe, and fruits with 5 (vs. 4) pyrenes.

Figures

FIGURE 103. Lasianthus vietnamensis V.S.Dang, Naiki & Tagane (from V6668, VNM): A. Branch with flower buds, B. Close-up of expanding young leaves, C. Stipules, D.Abaxial leaf surfaces, E–G. Inflorescence showing side view calyxes, H. Fruits, I. Seeds (A, D–F, H: photos by Shuichiro Tagane).

FIGURE 104. Distribution maps of Lasianthus vietnamensis, L. viridiramulis, L. vuquangensis, L. yaharae and L. yersinii.