Begonia mentiens 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 : 22-25

9. Begonia mentiens S.Julia & Kiew , sp. nov.

Similar to Begonia jamilahanuiana S.Julia in its habit and leaf characters, but B. mentiens can be distinguished by its wider lamina, 4.5–9 cm (versus 2.5–5 cm wide); inflorescence a compound cyme, 1–4 cm long, produced from leaf axils from base to stem apex (versus paniculate inflorescence 7–15 cm long produced from upper leaf axils); bracts narrowly ovate to linear, c.3 × 1 mm, and bracteoles c.2 × 1 mm, margin entire (versus bracts ovate, 6–7 × 3–4 mm, bractoles 2–6 × 2–5 mm, margin studded with glandular knobs); smaller ovary, 9–10 × 13–15 mm, with equal wings (versus ovary 17–20 × 13–15 mm, with unequal wings); and capsule wider than long, 8–10 × 12–16 mm, with longer pedicel, 11–12 mm long (versus longer capsule, 11–17 × 11–15 mm, with pedicel 5–10 mm).

– Type: Malaysia, Borneo , Sarawak, Julau District , Lanjak Entimau Wildlife Sanctuary, Sungai Igan, 1°44′13′′N, 112°05′59′′E, 25 v 2016, Ling & Dino SFC 5966 (holotype SAR!, isotype KEP!). Figure 10 .

Cane-like herb to 75 cm tall; whole plant glabrous. Stems dark magenta, 4–5 mm thick, internodes 2–5 cm, slightly thicker at the nodes. Stipules magenta, ovate, 7–10 × 5–7 mm, margin entire, keeled, apex setose, seta 1–2 mm long, caducous. Leaves alternate, distant, oblique, asymmetrical, held more or less horizontally, sometimes held at a 45° angle; petioles magenta, 6–10.5 cm long, grooved above; lamina glabrous with silvery elongated spots in between veins, sometimes with silvery spots along the margin and at the leaf apex or sometimes plain green above, pale green beneath, juvenile plants usually with pinkish spots, in life succulent, matt, ovate, 10–13 × 4.5–9 cm, broad side 4–8 cm wide, base shallowly cordate, basal lobes 3–8.5 cm long, margin almost entire, apex acuminate to caudate, acumen 1.5–2 cm long; venation palmate-pinnate, above veins green except near base, magenta beneath, slightly impressed above except near leaf base, prominent beneath, 6–8 veins radiating from the base of leaf, 7 or 8 along the midrib on the broad side, 3–5 veins in basal lobe. Inflorescences protogynous, in the upper leaf axils, compound cyme, 1–4 cm long, up to 7 female inflorescences in the lower part of the leafless stem; male inflorescence towards the apex; bracts reddish, narrowly ovate to linear, c.3 × 1 mm, margin entire, apex setose, seta c. 1 mm long, caducous; bracteoles similar to bracts but smaller, c.2 × 1 mm, caducous. Male flowers: pedicel pink, 7–10 mm long; tepals 2, white or pale pink tinged reddish towards base, ovate, 6–7.5 × 4–6.5 mm, margin entire, apex rounded; stamens 19–26, cluster subsessile, globose, filaments pale yellow, c. 0.5–1 mm long; anthers pale yellow, obovate, c.0.8–1 × 0.8–1 mm, apex emarginate. Female flowers: pedicel pinkish, 9–10 mm long, glabrous; ovary pale green, ovate to triangular in outline, ovary including the wings 9–10 × 13–15 mm, wings 3, equal, sometimes tinged pink, locules 3, placenta 1 per locule; tepals 5, pale pink, deeper pinkish at base, outer four tepals elliptic, 6–9 × 3–4 mm, margin entire, apex rounded, inner tepal narrowly elliptic, 6 × 2.5–3 mm; styles 3, pale yellow green, 2–3 mm long, deeply divided to base, widely Y-shaped; stigma pale yellow, papillose cells large and pale yellow forming a continuous twisted band. Capsules glabrous, 8–10 × 12–16 mm, locules 3, wings 3, equal, rounded proximally, truncate distally, 4–6 mm wide, thinly fibrous, dehiscing between locule and wing; pedicel pendent, 11–12 mm long, reddish towards the base.

Distribution. Malaysia ( Sarawak). To date, known only from Lanjak Entimau Wildlife Sanctuary (see Figure 1 ), where the species is widely distributed.

Habitat. Riparian forest along stream bank with large sandstone or mudstone boulders, on alluvial soils, at elevations 124– 140 m.

Etymology. Latin, mentiens (‘imitating’), referring to the sterile plant resembling those of Begonia jamilahanuiana .

Additional specimens examined. MALAYSIA. Sarawak: Julau District – Ulu Mujok, Sungai Sunpan , 1 ° 42′20′′N, 112 ° 04′48′′E, 20 v 2016, Ling & Dino SFC 5918 ( KEP, SAR) ; Mujok, Lanjak Entimau Wildlife Sanctuary, Sungai Segak , 1 ° 40′53′′N, 112 ° 09′40′′E, 21 v 2016, Ling & Dino SFC 5929 ( KEP, SAR) ; Sungai Nyamuk, tributary of Sungai Mujok , 1 ° 41′24′′N, 112 ° 07′01′′E, 23 v 2016, Ling & Dino SFC 5949 ( KEP, SAR) ; Sungai Mujok, Sungai Sugai , 1 ° 44′04′′N, 112 ° 05′59′′E, 24 v 2016, Ling & Dino SFC 5958 ( KEP, SAR) .

Begonia mentiens is rather common and occurs in a few river systems in Ulu Mujok. In the field, individual plants are scattered (not growing in clumps or close together). In comparison, plants of Begonia jamilahanuana usually grow close together to form a large clump. The irregular spots on the upper leaf surface of Begonia mentiens are pink in the juvenile stage but turn white with age or sometimes completely disappear, whereas the spots on B. jamilahanuana leaves are persistent in adult plants.

Begonia jamilahanuana and B. mentiens seem to occupy different microhabitats. Begonia jamilahanuana is usually found along shade ridges of hill mixed dipterocarp forest with a thick layer of leaf litter, in contrast to B. mentiens , which usually grows by stream banks.

Figures

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

Figure 10. Begonia mentiens S.Julia & Kiew, sp. nov. A, Habit, showing spotted leaves; B, habit, showing individual with plain leaves; C, stipule; D, inflorescence on lower part of stem; E, male inflorescence; F, male flower; G and H, female flower; I, old capsule; J, cross-section of female flower. All photographs taken by C. Y. Ling: A, C and G–J, Ling & Dino SFC 5918; B and E–G, Ling & Dino SFC 5949; D, Ling & Dino SFC 5966 (the type specimen).