Begonia muluensis C. Y. Ling & Kiew. A & B. Habit 2018, spec. nov.

Similar to Begonia yiii Kiew & S. Julia (2013: 28) in its habit and inflorescence but it can be differentiated by its thinner stem 3–5 mm thick (vs. ca. 7 mm thick), lamina slightly falcate, elliptic or oblanceolate with an acuminate apex, acumen to 1.5 cm long (vs. broadly obovoid lamina with rounded or sometimes caudate apex), bracts larger 15–20 × 11–14 mm (vs. 13–15 × 8–9 mm), and shorter fruit pedicel, ca. 2.5 mm long (vs. 5–6 mm long). Type:— MALAYSIA. Borneo. Sarawak. Marudi District: Gunung Mulu NP, Gunung Mulu, 19 April 2016, Ling et al. SFC 6925 (holotype SAR!).

Erect herb to 45 cm tall, sometimes straggling. Stem, petiole, stipules, lower surface of veins and peduncle sparsely hispid, hairs magenta or white. Stem reddish, red-brown or light green, little branched, succulent, 3–5 mm thick; internodes 2–4.5 cm long, slightly thicker at nodes. Stipules ovate, 12–24 × 7–13 mm, reddish to pale green, margin ciliate, apex acute, persistent. Leaves alternate, distant, not oblique, held at 45° angle, in young plants held horizontally; petiole reddish to red-brown, 1–4.5 cm long, slightly grooved above. Lamina asymmetric, elliptic or oblanceolate, slightly falcate, 5–10.5 × 3.2–5.6 cm, broad side 2–3.2 cm, base rounded, margin irregularly or minutely serrate, apex acuminate, acumen 0.5–1.5 cm long, plain green to dark olive green above, pale green or magenta beneath, succulent, glossy; venation pinnate, 2–4 veins on either side of the midrib, above reddish near the base, beneath magenta, otherwise green, impressed above, prominent beneath. Inflorescence protogynous, axillary in the upper leaf axils, racemose, 6–15 cm long, peduncle 2.5–6 cm long, usually with 1, rarely 2 female flowers at the base with male flowers above. Bracts pale green, reddish or white, ovate, 15–20 × 11–14 mm, margin ciliate, persistent; lower bracteoles similar to bracts, 2–4 pairs, pale green tinged red at the base or sometimes reddish, ovate, 6–12 × 5.5–9 mm, margin ciliate, persistent; upper bracteoles 2–4 pairs, white or pinkish, folded in half, oval, 6–10 × 8–11 mm, margin minutely serrate or ciliate, persistent. Male flower: pedicel white or pinkish, minutely hairy, hairs white, 6–8 mm long; tepals 4, white inside, outside white tinged pinkish towards the apex, glabrous, margin entire, outer 2 tepals elliptic, 10–14 × 7.5–9 mm, apex broadly acute, inner 2 tepals narrowly elliptic to lanceolate, 8–12 × 2–2.5 mm, apex acute; stamens 38–46, cluster conical, subsessile; filament pale yellow, 0.4–0.5 mm long; anther yellow, obovate, 1–1.5 × 0.5–1 mm, apex emarginate. Female flower: sessile, ovary white, pale green or pinkish, ovate, 5–9 × 12–16 mm, glabrous, wings 3, unequal, locules 3, placentas 2 per locule; tepals 5, white or sometimes pinkish white outside, outer 4 tepals ovate, 6–12 × 4–8 mm, inner tepal broadly lanceolate or rarely ovate, 4.5–10 × 3–4 mm; styles 3, orange-yellow, 3–4 mm long, divided to base, deeply Y-shaped above; stigma yellow, papillose forming a continuous twisted band. Capsule single or in pairs, 8–10 × 12–15 mm, glabrous, locule 3, wings 3, subequal, rounded proximally and distally, 5–7 mm wide, thinly papery, dehiscent between locule and wing; pedicel pendent, 5–6 mm long, glabrous.

Distribution: — MALAYSIA. Borneo. Sarawak. Endemic in Gunung Mulu NP where it is very common around Camp 3.

Habitat: —Lower montane forest in semi-exposed to shaded areas at 800–1381 m elevation.

Etymology: —Named after its type locality, Gunung Mulu.

Additional specimens examined: — MALAYSIA. Borneo. Sarawak. Marudi District: Gunung Mulu NP – Gunung Mulu, Ling et al. SFC 6931 (SAR), Martin S 38153 (K, KEP).

Notes: —This species usually grows in clumps. Two different leaf colours were observed within the same population, i.e., individuals with plain green leaves and individuals with leaves magenta underneath.