Diagnostic Description

Notes. Our field photos and specimens are a good match for material collected from the DVCA, and for the photos in Chong et al. (2015) and Kiew et al. (2015: 94 & 95). The Kalimantan specimens lack dentate tepals in the female flowers, and have slightly more elongate male inflorescences, but we consider this to be acceptable withinspecies variation as the populations are fairly disjunct.

In its habit, non-oblique leaves and hairs on the upper leaf surface, it is most similar to Begonia fuscisetosa Sands (1997: 433), but it is different from this species in its obovate leaves, less than three times longer than wide (vs. elliptic leaves, more than three times longer than wide as in B. fuscisetosa), many flowered inflorescences (vs. few flowered ones) and fruit stalks shorter than the capsule (vs. longer than the capsule).

Provided by: [B].The Begonia TEN / Begonia Resource Centre (Royal Botanic Garden Edinburgh)
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Morphology

Robust begonia to 1 m tall, becoming bushy with a few erect branches from the base, individual stems unbranched or sometimes two-branched with short lateral branches. Stems greenish brown, woody, c. 7 mm diameter, pubescent, hairs white, internodes 3.5–5.5 cm long, swollen at the nodes. Stipules dark red, pubescent, lanceolate, 12–14 × 4–6 mm, margin entire, apex setose, seta c. 1 mm long, caducous. Leaves alternate and distant or with an extremely short internode and appearing opposite, not oblique, held more or less horizontally; petiole green, pubescent, 1–1.7 cm long, flat above; lamina plain rice green, with a row of short dark red bristles with a white tip between the veins, thin in life, matt, obovate, slightly asymmetric, 13–17.5 × 5–7 cm, broad side 2.7–4 cm wide, basal lobe rounded, 0.4–1.2 cm long, margin minutely toothed, apex attenuate to acuminate, acumen to 1.5 cm long; venation pinnate with 7 veins on either side of the midrib, twice branched, 2 veins in the basal lobe, concolorous, strongly impressed above and prominent beneath, midrib pubescent above. Inflorescences protogynous, axillary, racemose, reddish green, pubescent, erect, longer than petioles, 4.5–5.5 cm long with peduncle c. 3.5 cm long, with 2 female flowers at the base and many male flowers above. Bracts maroon, lanceolate, 4.5–9 × ca. 4 mm, pubescent, margin entire, caducous. Bracteoles light brown, triangular, 1–4 × 1–3 mm, margin entire, caducous. Male flower: pedicel pale red, c. 4 mm long; tepals 2, outside deep pink with dark red hairs, inside white pink towards the base, broadly oval, c. 5 × 4 mm, margin entire, apex rounded; stamens 25–28, cluster conical, shortly stalked; filament pale yellow; anthers pale yellow, obovate, c. 1 × 0.5 mm, apex emarginate. Female flower: pedicel c. 6 mm long, pale green, white or red, hairy; ovary pale green, narrowly triangle, c. 1.5 × 1.2 cm, wings 3, more or less equal, locules 3, placentas bilamellate with many ovules on both surfaces; tepals 5, pale green, equal, c. 7 × 5 mm, margin denticulate, with a single pair of teeth in the upper half of the apex; styles 3, pale yellowish green, c. 2.5 mm long, divided to base; stigma pale yellow, papillose forming a continuous twisted band. Capsules (1.6–)1.8(–2.3) × 1.4–1.7(–1.9) cm, locules 3, wings 3, equal, rounded proximally, distally truncate with a pointed tip, c. 6 mm wide, thinly fibrous, dehiscing between the locule and the wing, pendent, pedicel stiff, 4–8 mm long. Seeds ellipsoid, c. 0.4 × 0.2 mm, columnar cells more than half of seed length.

Provided by: [B].The Begonia TEN / Begonia Resource Centre (Royal Botanic Garden Edinburgh)
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Habitat

This is the most common begonia species in DVCA and was found along all trails visited in lowland mixed dipterocarp forest on slight slopes in deep shade or on the side of gullies to 150 m elevation. From the few herbarium collections, it appears to have been overlooked by collectors. It often grows together with B. rotundibracteata Kiew that is similar in habit.

Provided by: [B].The Begonia TEN / Begonia Resource Centre (Royal Botanic Garden Edinburgh)
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Distribution

Found in the Danum Valley Conservation Area (DVCA) in Sabah, and also around Gua Tewet in Bengalon, East Kalimantan. It is described as one of the most common Begonia in the DVCA by Chong et al. (2015), and we noted it formed quite large colonies near the trails around Gua Tewet (Fig. 8).

Borneo. Endemic to Sabah (Danum Valley Conservation Area, Lahad Datu).