Lasianthus latifolius (Blume ex DC.) Blume ex Miq. (1857: 320)

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

44. Lasianthus latifolius (Blume ex DC.) Blume ex Miq. (1857: 320) — Fig. 70 (plate), Fig. 67 (map)

Type: — INDONESIA. Java, Blume s.n. (lectotype L! [L0057522], designated by Zhu 2012) .

Mephitidia latifolia Blume ex DC. (1830: 453) . Type: — INDONESIA. Java, Blume s.n. (lectotype L! [L0057522], designated by Zhu 2012).

Specimens examined: — VIETNAM. Central: Gia Lai Province, K’Bang District, Kon Chu Rang Nature Reserve , 1015 m elev., 20 April 2021, Dang V.S., Truong B.V. & Duong M.T.T.N., Dang 464 ( VNM) .

Distribution: —Southeast Asia region ( Cambodia, Indonesia). In Vietnam, Lasianthus latifolius occurs in Kon Chu Rang Nature Reserve of Gia Lai Province.

Habitat & Ecology: —This species was collected under the canopy of the evergreen forest at around 900–1100 m elev.

Phenology: —Fruiting from February to May, fruiting from June to October.

Vernacular name: —Xú hưƠng lá rộng.

Notes: — Lasianthus latifolius is a new record for the flora of Vietnam. This species is characterized by having elliptic-oblong leaves, secondary veins 6–7 on each side of midrib, flowers white, calyx lobes longer than the calyx tube, and fruits globose with 6 pyrenes. It is closely related to L. calycinus Dunn (1912: 367) which is endemic to China, but differs from the latter in having fewer secondary veins (6–7 on each side of midrib vs. 8–9 on each side of midrib), longer petioles (10–15 mm long vs. 8–10 mm long), smaller calyx (tube ca. 1.5 mm long, lobes ca. 2.5 mm long vs. tube 2–2.5 mm long, lobes 4–5 mm long) and larger corolla (8–12 mm long vs. 7–9 mm long).

Additional corolla morphology for L. latifolius : corolla cylindrical, 8–12 mm long, white, corolla tube 6–8 mm long, pubescent outside, corolla lobes 5, triangular-lanceolate, 2–4 mm long, pubescent outside, floccose inside, the throat hairy; stamens 5, filaments short, anthers oblong, 1–1.4 mm long; ovary with 5 locules, style linear, 7–8 mm long.

Figures

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

FIGURE 70. Lasianthus latifolius (Blume ex DC.) Blume ex Miq. (from Dang 464, VNM): A. Branch, B. Close-up of young branch and leaves, C. Stipules, D. Abaxial leaf surfaces, E–G. Inflorescence showing side view calyx, buds and flowers, H–J. Fruits.