Lasianthus coriaceifolius H.Zhu, 2012

Zhu, H., Roos, M. C. & Ridsdale, C. E., 2012, A taxonomic revision of the Malesian species of Lasianthus (Rubiaceae), Blumea 57 (1), pp. 1-102 : 31

31. Lasianthus coriaceifolius H.Zhu , sp. nov. — Fig. 10

Proximus L. myrtifolio Ridl. subsp. vicario H.Zhu , sed foliis majoribus 9–11 cm longis 3–4.5 cm latis, nervulis reticulatis, calycibus majoribus, tubis calycis longioribus, lobis calycis ovato-oblongis et drupis acute 8-porcatis differt. —

Typus: Lee S.52556 ( holo L; iso K), Borneo, Sarawak, Ulu Trusan Lawas , 900 m alt., in hill mixed dipterocarp forest, 12 May 1986 .

Treelet, 4–5 m high; branchlets terete, 3–4 mm diam, fistulose, glabrous, darkish. Leaves: blades lanceolate-oblong or oblong, 9 –15 by 3 –6 cm, thickly coriaceous, glabrous on both surfaces; apex abruptly acute, base acute to subrounded, midrib slightly depressed above, conspicuously prominent beneath, darkish, nerves prominent on both surfaces, 6 – 8 pairs, ascending at an angle of c. 80 °, curved to margin; nervules prominent on both surfaces, conspicuously reticulate, margin conspicuously recurved; petioles 0.5 –1 cm long, glabrous, darkish. Stipules triangular, c. 3 by 3 mm, glabrous. Inflorescences sessile; bracts inconspicuous. Flowers fascicular, sessile; calyx longcampanulate, sparsely puberulous or glabrous, darkish, tubes c. 3 mm long, lobes 4, ovate-oblong, c. 2 mm long; corolla 8–9 mm long, glabrous external surface. Drupes ellipsoid, 5 –6 mm diam, with 8 acute, conspicuous ridges, glabrous, crowned by persistent calyx lobes; pyrenes 4, rhombic-circular in the transverse section.

Distribution — Malaysia ( Sarawak) and Brunei.

Habitat & Ecology — In montane forest. Flowering and fruiting between May and September.

Note — This species is characterized by its glabrous plants, thickly coriaceous leaves with reticulate nervules and conspicuously recurved margin, and 8-ridged drupes. It is closely related to L. myrtifolius subsp. vicarius , but differs from the latter by having relatively big leaves (9–11 by 3–4.5 cm) with reticulate nervules, relatively big calyx ( 5 mm long) with longer calyx tubes and ovate-oblong calyx lobes, drupes with 8 acute ridges. Lasianthus myrtifolius subsp. vicarius has leaves 4.5–7.5 by 2 –3 cm, nervules parallel, calyx campanulate, 2 – 3 mm long with triangular calyx lobes, drupes without conspicuous ridges.

Figures

Fig. 10 Lasianthus coriaceifolius H.Zhu. a. Habit with inflorescences; b. lower surface of leaf showing reticulate nervules; c. detail of node showing stipule and axillary inflorescences; d. fruit; e. cross section of fruit (all: B. Lee S.52556, holo L).