Lasianthus bifloroideus 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 : 19

10. Lasianthus bifloroideus H.Zhu , sp. nov. — Fig. 4

Similis L. bifloro (Blume) M.Gangop.& Chakrab. ,sed ramulis rare puberulis, foliis ovato-lanceolatis glabris, cymis sessilis vel subsessilis, lobis calycis ovato-oblongis longioribus tubo et pyrenis conspicue verrucatis differt. —

Typus: Paul Chai S.33809 ( holo L; iso K), Borneo, Lubok Antu, Bukut Peninjau , in valley bottom, 13 Mar. 1974 .

Small shrub, 1–2 m high, branchlets terete, slender, less than 1 mm diam, puberulous. Leaves: blades very small, ovate-lanceolate, 1.5 – 3 by 0.5 –1 cm, chartaceous, glabrous on both surfaces, apex acuminate, mucronate, base acute; midrib slightly prominent above, prominent beneath, nerves slender, flat above, prominent beneath, 5 pairs, ascending at an angle of c. 60 °, curved to margin, nervules weak, slender, parallel; petioles short, less than 1 mm long, puberulous. Stipules lanceolate, c. 1 mm long, puberulous. Inflorescences sessile or subsessile, bracts absent. Flowers very small; calyx c. 1 mm long, sparsely puberulous, calyx lobes 4, ovate-oblong, c. 0.7 mm long; corolla not seen. Drupes subglobose, 4–5 mm diam, glabrous, 4-ridged, crowned by 4 c. 1 mm long ovate-oblong calyx lobes; pyrenes 4, warty on abaxial face, orbicular in transverse section.

Distribution — Endemic to Borneo (Lukok Antu).

Habitat & Ecology — Valley bottom near river. Flowering and fruiting in March.

Note — This species is closely related to L. biflorus , but differs from the latter by having branchlets thinly puberulous, leaves ovate-lanceolate glabrous, cymes sessile or subsessile, calyx lobes ovate-oblong longer than calyx tube, drupes more warty. Lasianthus biflorus has branchlets hirsute, leaves subrhombic to elliptic-obovate, hirsute midrib and nerves beneath, cymes with 5 –15 mm long peduncles, drupes less warty.

Figures

Fig. 4 Lasianthus bifloroideus H.Zhu. a. Habit; b. detail of lower surface of leaf showing parallel nervules; c. calyx; d. fruit; e. cross section of fruit (all: Paul Chai S.33809, holo L).