Lasianthus membranaceoideus 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 : 62

77. Lasianthus membranaceoideus H.Zhu , sp. nov. — Fig. 24

A L. membranaceo Stapf foliis coriaceis, venationibus brachidodromibus, stipulis inconspicuis, bracteis inconspicuis, fructibus globosis conspicue octogonis, pyrenis 4 differt. —

Typus: Dransfield et al. 6537 ( holo L ; iso K), Brunei, Belait, 50 m alt., in primary mixed dipterocarp forest, 5 June 1989.

Small tree, up to 3 m high, branchlets terete, 2 mm diam, glabrous. Leaves: blades oblong, 9–11 by 3–4 cm, coriaceous, glabrous, apex cuspidate, base subrounded to cuspidate, midrib depressed above, prominent beneath, nerves prominent on both surfaces, 6 – 8 pairs, combinate venous, ascending at an angle of almost 90°, curved near the leaf margin and joining the veins above forming an intramarginal vein, internerved veins conspicuous, ascending from the midrib at a right angle, combination to the main nerves; nervules conspicuous on both surfaces, reticulate; petioles 6 –10 mm long, glabrous. Stipules inconspicuous. Inflorescences sessile or forming a very short tubercle; bracts inconspicuous. Flowers sessile, very small; immature flowers only 1 mm long, 4-merous; calyx campanulate, glabrous, lobes ovate-triangular, 0.3 – 0.5 mm long; corolla glabrous on external surface, lobes 4, ovate, 0.5 mm long; anthers 4. Drupes globose, c. 7 mm diam, conspicuously 8-ridged, glabrous, rugose; pyrenes 4, rarely 3, with two irregular sulcae on the abaxial face of the pyrene, subrhombic in transverse section, and with very thick-walled abaxial side.

Distribution — Endemic to Borneo.

Habitat & Ecology — In lowland rainforest between 50– 300 m altitude. Flowering and fruiting between March and June.

Additional specimen examined. Borneo, Sabah, Lumaku, Nooteboom 1167 (L).

Note — This species is close to L. membranaceus . It differs from the latter by having coriaceous leaves with combinate venous nerves forming looped venation; stipules inconspicuous; drupes globose with 8 ridges, pyrenes 4; each pyrene with 2 irregular sulcate on the abaxial face. Lasianthus membranaceus has membranaceous to subcoriaceous leaves without conspicuous looped venation; stipules triangular, 3 mm long; drupes verrucose, without conspicuous ridges; pyrenes usually 2, rarely 3–4; pyrene without 2 sulcae on the abaxial face.

Figures

Fig. 24 Lasianthus membranaceoideus H.Zhu. a. Habit with inflorescence; b. leaf; c. fruit; d. cross section of fruit (all: J. Dransfield et al. 6537, holo L).