Begonia triangularis Kiew & C.Y.Ling

Sang, Julia, Kiew, Ruth & Yiing, Ling Chea, 2016, Six new species of Begonia (Begoniaceae) from Central Sarawak, Borneo, Phytotaxa 277 (2), pp. 171-181 : 179-180

6. Begonia triangularis Kiew & C.Y.Ling , spe c. nov. ( Figure 7 )

Section Petermannia

Diagnosis: —Similar to Begonia murumensis S.Julia & C.Y.Ling (2015: 115) in its cane-like habit, petiolate non-oblique, narrowly lanceolate leaves, inflorescence, and female flowers with dimorphic tepals, but it is different in its male flowers with 4 tepals with larger outer tepals 7–8 × 4–6 mm (vs. flowers with 2 tepals, 4–5 × 3 mm in B. murumensis ) and broadly triangular fruits 6–8 × 10–12 mm (vs. squarish in outline and 12–15 × 11–18 mm).

Type: — MALAYSIA. Borneo. Sarawak. Kapit District: Bukit Ngingit, 7 August 2015, Ling et al. SFC 5709 (holotype SAR!; isotype KEP!) .

Erect herb to 30 cm tall. Indumentum of stems, stipules, petioles and peduncles of dense minute fine white hairs. Stems reddish brown, unbranched, succulent, 2.5–3.5 mm thick, internodes 2–4 cm long, thicker at nodes. Stipules pale green tinged pale red at base, ovate, 9–12 × 5–6 mm, margin ciliate, apex acute, caducous. Leaves alternate, distant, not oblique, held horizontally; petioles reddish brown, 0.8–2.8 cm long, terete or slightly grooved; lamina plain green to dark green above, pale green beneath, young plants with grey-green leaves, in life succulent, glossy, slightly asymmetric sometimes equal especially in juvenile plants, narrowly oblanceolate, slightly falcate 8.5–13 × 2.5–4 cm, broad side 1.5–3 cm wide, base rounded, basal lobes undeveloped, margin unequally serrate with larger teeth at the vein endings, apex acuminate, acumen 1.5–2 cm long; venation pinnate, veins greenish above dark brown near the leaf base, pale green beneath, 5–6 veins on either side of the midrib, slightly impressed above, midrib slightly raised above, prominent beneath, minutely pubescent on both surfaces. Inflorescences protogynous, axillary in axils of upper leaves, racemose 3–6 cm long, peduncle 1.5–2 cm, one or two female flowers below, above sparsely branched with male flowers. Bracts pale green, sometimes tinged red at base, ovate, 9–13 × 6–9 mm, margin ciliate, persistent; bracteoles 2–4 pairs, bracteoles of female flowers similar to bracts, pale green sometimes tinged reddish, 10–11 × 4–5 mm, bracteoles of male flowers reddish, oval, 5–8 × 5–10 mm, margin serrate, each tooth tipped by a hair, persistent. Male flowers: pedicel pale green, sometimes tinged red, 2–3 mm long, glabrous; tepals 4, white inside, outside white or sometimes reddish towards the apex of outer tepals, glabrous, outer 2 tepals broadly ovate, 7–8 × 4–6 mm, margin entire, apex broadly acute; inner 2 tepals lanceolate, 5–7 × 2mm, margin entire, apex acute; stamens 37–45, cluster conical, subsessile; filaments pale yellow, 0.8–1 mm long; anthers pale yellow, obovate, 0.8 × 0.4 mm, apex emarginate. Female flowers: pedicel pale green, ca. 3 mm long, glabrous; ovary pale green with reddish wings or deep red, ovate, ca. 5 × 10 mm, glabrous, wings 3, equal, locules 3, placenta 2 per locule; tepals 6, white inside, outside white tinged reddish, glabrous, outer 5 tepals ovate, 5–6.5 × 3-5 mm, margin entire, apex acute, inner tepal lanceolate, ca. 6 × 2 mm; styles 3, pale yellow, 2–2.5 mm long, divided to base, shallowly Y-shaped; stigma pale yellow, papillose forming a twisted band. Capsules single or in pairs, 6–8 × 10–12 mm, glabrous, locules 3, wings 3, unequal, broadly rounded proximally, slightly concave or rounded distally, 4–6 mm wide, thinly fibrous, dehiscing between locule and wing; pedicel pendent, 5–6 mm long.

Etymology: —Latin, triangularis = triangular; referring to the narrowly triangular almost equal-sided leaf.

Distribution: — MALAYSIA. Borneo. Endemic in Sarawak. So far known only from the type locality.

Habitat: —Disturbed hill dipterocarp forest, growing near streams on old logging road with sandstone and mudstone boulders.

Proposed conservation status: —Critically Endangered. The species is known only from a single locality that lies outside the network of Totally Protected Areas. The species is threatened by habitat disturbance due to logging.

Figures

FIGURE 7. Begonia triangularis. A–B, Habit; C, Stipule; D, Male inflorescence showing the bract and bracteoles; E, Male flower; F–G, Female flower; H, Old fruits; I, Cross-section of ovary.All photos from SFC 5709 by C.Y.Ling.