Begonia humifusa S.Julia & Kiew, 2022

Julia, S., Kiew, R. & Ling, C. Y., 2022, ADDITIONS TO THE BEGONIA FLORA OF SARAWAK, BORNEO, I: TWELVE NEW SPECIES AND A NEW RECORD, Edinburgh Journal of Botany 79 (410), pp. 1-46 : 8-10

3. Begonia humifusa S.Julia & Kiew , sp. nov.

Similar to Begonia addrinii S.Julia & Kiew in its habit but distinguished by its unevenly bullate, obovate to rhomboid leaves (versus bullate, obovate to orbicular leaves); shorter ovate bracts, 2–3 × 2–3 mm (versus lanceolate, 4–7 × 2–3 mm); and stamens 36–41 (versus 25–30).

– Type: Malaysia, Borneo , Sarawak, Julau District , Lanjak Entimau Wildlife Sanctuary , Mujok, Sungai Segak Mit, 1°40′56′′N, 112°09′30′′E, 21 v 2016, Ling & Dino SFC 5930 (holotype SAR!, isotype KEP!). Figure 4 .

Creeping herb, rooting at the nodes. Stem, petiole and stipule densely pilose, hairs whitish. Stems to 33 cm long, unbranched, pale green, internodes 1.5–4.5 cm long, 4–6 mm thick, slightly thicker at nodes. Stipules pale green, ovate, 6–12 × 6–12 mm, margin entire, keeled, apex setose, seta 1–2 mm long, caducous. Leaves closely arranged when young, becoming distant when mature, slightly oblique; petioles pale green, reddish when young, 0.7–2.5 cm long, succulent, terete; leaves plain green above, sometimes with a metallic sheen, paler beneath, in life succulent, bullate, sometimes with hispid hairs in between veins above, hairs whitish, slightly asymmetrical, obovate to rhomboid, 4.5–7 × 3.2–8 cm, base cordate, overlapping, slightly unequal, basal lobe 0.6–1.3 cm long, margin shallowly serrate and ciliate, apex acute or rounded; venation palmate, 4 or 5 veins radiating from the base, branching 2 or 3 times towards the margin, with 2 veins in basal lobe, concolorous, slightly impressed above, prominent beneath. Inflorescences erect, axillary, several along the creeping stem, pinkish or brownish, simple dichasia, peduncle unbranched, 3–6 cm long, topped by 1 female and 2– 4 male flowers; bracts reddish, ovate, 2–3 × 2–3 mm, margin entire, keeled, apex acute, persistent; bracteoles reddish, ovate to lanceolate, 2.5–4 × 1–2 mm, margin entire. Male flowers: pedicel white to pale pink, 8–17 mm long, glabrous or bristly, hairs pink; tepals 4, white or white tinged pink towards apex inside, with bristles outside, hairs white to pinkish, margin entire, apex broadly acute, outer two tepals broadly ovate to elliptic, 5–14 × 7–12 mm, inner two tepals narrowly elliptic to oblong, 5–13 ×

2–4 mm, stamens 36–41, cluster loosely globose, subsessile, filaments c. 1 mm long; anthers yellow, obovate, 1.2–1.5 × 0.4–0.6 mm, apex emarginate. Female flowers: pedicel whitish or greenish, 5–6 mm long, ovary pinkish or greenish tinged reddish, ovary and wings triangular, 5–8 × 8–14.5 mm, wings 3, slightly unequal, 2–3.5 mm wide, locules 3, placentas 2 per locule; tepals 5, whitish, pinkish or whitish green, broadly ovate; outer four tepals 5–10 × 4–7 mm, glabrous or bristly outside, hairs pink, inner tepal 4–8 × 3–4 mm, margin entire, apex broadly acute, styles 3, yellow, 2–3 mm long; stigma yellow, anchor-shaped, papillose. Capsules single, pale green or pale green tinged reddish, 0.5–0.8 × 0.9–1.3 cm, locules

3, wings 3, slightly unequal, 2–4 mm wide, acute proximally, rounded to acute distally, dehiscing between the locules and wings; pedicel pendent, green, stiff, 5–7 mm long.

Distribution. Malaysia ( Sarawak). To date, known only from a few river systems in Julau District (see Figure 1 ).

Habitat. Locally abundant, growing near riverbanks in primary forest and also in disturbed forest areas on clayey exposed soils on steep slopes at 136–164 m elevation.

Etymology. Latin, humifusus (‘spreading over the surface of the ground’), referring to its creeping habit.

Additional specimens examined. MALAYSIA. Sarawak: Julau District – Lanjak Entimau Wildlife Sanctuary, Mujok, Sungai Sengkadang , 1 ° 40′53′′N, 112 ° 09′07′′E, 22 v 2016, Ling & Dino SFC 5943 ( KEP, SAR) ; Mujok, Sungai Nyamuk , 1 ° 40′53′′N, 112 ° 09′07′′E, 23 v 2016, Ling & Dino SFC 5946 ( KEP, SAR) ; Mujok, Sungai Igan , 1 ° 44′20′′N, 112 ° 06′02′′E, 25 v 2016, Ling & Dino SFC 5969 ( KEP, SAR) .

In life, the leaves of Begonia humifusa are conspicuously bullate, but on drying this character is lost. This species is locally common and abundant. It occurs both within and outside the boundary of the Totally Protected Area (TPA) of Lanjak Entimau Wildlife Sanctuary.

Begonia humifusa resembles B. gibbsiae Irmsch. ex. Sands in its leaf shape, size and venation but differs in having longer stems, 33 cm (versus 3–25 cm long); wider stipules, 6–12 mm (versus 1.2–2 mm wide); and axillary inflorescences 3–6 cm long (versus terminal inflorescence 13–20 cm long).

Figures

Figure 1. Distribution of Begonia papyraptera and the 12 new species of Begonia recorded from Sarawak and described in this article.

Figure 4. Begonia humifusa S.Julia & Kiew, sp. nov. A, Habit; B, stipule; C, inflorescence; D and E, male flowers; F and G, female flower; H, capsule; I, cross-section of capsule. All photographs taken by C. Y. Ling: A, B and I, Ling & Dino SFC 5930 (the type specimen); C–F and H, Ling & Dino SFC 5946; G, Ling & Dino SFC 5943.