subsp. obliquinervis

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 : 66

a. subsp. obliquinervis

Lasianthus obliquinervis Merr. (1906) 136. — Type: Whitford 247 (lecto US, designated here), Philippines, Luzon , Bataan, May 1904.

Shrubs, c. 2 m high, branches 5 – 6 mm diam, striate; branchlets 2– 3 mm diam, terete or slightly compressed, puberulous. Leaves: blades ovate-lanceolate to ovate-elliptic, 10–15 by 2.5– 5 cm, subcoriaceous, glabrous above, puberulous beneath, brownish, apex acuminate to acute, rarely cuspidate, base acute, slightly asymmetric and decurrent, midrib slightly depressed above, prominent beneath, pubescent beneath, nerves flat above, prominent beneath, 3– 6 pairs, ascending at an angle of 50–70°, curved to the margin, brown pubescent, nervules obscure above, conspicuous beneath, parallel, glabrous; petioles 1.5 – 2 cm long, pubescent. Stipules triangular to oblong-triangular, up to 5–6 mm long, 3–4 mm broad at base, pubescent. Inflorescences sessile; bracts small, ovate to subulate, c. 1 mm long, hirsute. Flowers fascicular, sessile; calyx campanulate, 1.5 by 1.5 mm, densely pubescent, limb with 4–5 triangular lobes, lobes 0.5 mm long, densely hirsute outside, glabrous inside; corolla 6 – 8 mm long, densely hirsute except the base, lobes 5, oblong, c. 4 mm long; stamens 5, filaments 2 mm long; anthers 1 mm long. Drupes globose, hirsute, blue when fresh, 4–5 mm diam, crowned by persistent calyx lobes, 5 – 8-ridged, often 6-ridged; pyrenes 5 –8, smooth on the abaxial face, triangular in transverse section.

Distribution — Philippines (Luzon to Mindanao), Papua New Guinea (Southern Highlands).

Habitat & Ecology — Montane forest between 800–1800 m altitude.

Notes — This species is close related to L. chrysoneurus . It differs from the latter by having leaves with longer petioles (1.5 –2 cm) and acute base, as well as less nerves (3– 6 pairs); bracts small, less than 2 mm long; calyx lobes triangular, 1.5 mm long, glabrous internal surface; drupes conspicuously 5 –8-ridged. Lasianthus chrysoneurus has relatively big ovate-oblong or oblong leaves with petioles less than 1 cm long, the base cuneate to obtuse, nerves 8 –10 pairs; bracts longer than 2 mm; calyx lobes lanceolate, longer than 1.5 mm, hirsute both surfaces; drupes without conspicuous 5 –8 ridges.

Lasianthus obliquinervis is variable in leaf size. Specimens which were treated as L. obliquinervis were mixed with L. verticillatus even if identified by Merrill himself. From our check- ing on specimens in L, MO, SING and Chinese herbaria, most specimens indicated as L. obliquinervis agree well with L. verticillatus , while some do not. When Merrill described L. obliquinervis , he cited 10 collections (syntypes). We are not sure if all the syntypes represent the same species. Only two syntypes, i.e. Whitfort 247 and Meyer 2212 were traced and seen. Both of them match Merrill’s description and surely represent L. obliquinervis . Lasianthus obliquinervis differs from L. verticillatus by having stipules oblong-ovate, c. 5 mm long, calyx limbs with 4–5 triangular lobes and drupes with usually 6 triquetrous pyrenes and not crowned by an enlarged cupular and truncate calyx limb.