Begonia xiphophylloides Kiew, 2013

Sang, Julia, Kiew, Ruth & Geri, Connie, 2013, Revision of Begonia (Begoniaceae) from the Melinau Limestone in Gunung Mulu National Park and Gunung Buda National Park, Sarawak, Borneo, including thirteen new species, Phytotaxa 99 (1), pp. 1-34 : 31

14. Begonia xiphophylloides Kiew , spec. nov. ( Figure 17 )

Sect. Petermannia

Begonia xiphophylloides differs from B. xiphophylla Irmscher (1953: 100) in its smaller size (up to 30 cm tall not to 75 cm tall), smaller leaves (to 10 × 2 cm not 11.5–14.5 × 2–3 cm) that have a serrate margin (not distantly spaced teeth), short inflorescences to 4 cm long (not laxly branched and up to 9 cm long) and fruits almost circular in outline,10–11 × 9–11 mm, with wings 2–3 mm wide (not a broad fruit 10 × 18 mm with wings ca. 4.5 mm wide).

Type: — MALAYSIA. Borneo. Sarawak. Marudi District: Gunung Mulu National Park, Sungai Melinau , 16 April 1978, Kiew RK 267 (holotype KEP!; isotype K) .

Erect, bushy herb to 30 cm tall, flowering at 10 cm tall; fibrous root system extensive. Stems wiry, woody at base, with thickly matted hairs, much branched, internodes 2–2.5 cm long, (2–) 4 mm diameter. Stipules thin, lanceolate, 5–6.5 × 1.5–2 mm, margin entire, apex attenuated into an acute apex, caducous. Leaves alternate, sometimes opposite, distant. Petioles: 0.4–0.6(–1.3) cm long, with thickly matted hairs. Laminas dark green above, thinly papery when dried, glabrous above, beneath with appressed matted hairs especially on the veins, not oblique, narrowly elliptic to narrowly slightly oblanceolate, 6.3–8(–10) × 1.1–2 cm, slightly asymmetric, broad side 0.7–1.3 cm, base cuneate or rounded, slightly unequal, margin serrate especially in upper half, teeth tipped by a distinct hair, apex acute to narrowly acuminate, acumen to 1 cm long. Venation pinnate, lateral veins 4–5 pairs along midrib, acutely ascending to the margin, slightly raised above, prominent beneath. Inflorescences terminal on short side branches 1–2 cm long, protogynous, sessile with a single female flower from the leaf axil, above racemose, 2.5–4 cm long, and producing one at a time a series of few-flowered dichasia of male flowers. Bracts transparent, pale green, lanceolate ca. 5 × 1.5–2.5 mm, margin entire, apex acute, caducous. Uppermost bracts of male flowers many, pale green, ovate, 4–7 × 1.5–2.7 mm, margin entire, apex apiculate, persistent. Male flower: pedicels fine, 1.5–3(–6) mm long; tepals 2, white, broadly oval, 2.2– 3.5 × 1.5–2.5 mm, glabrous, margin entire, apex rounded; stamens 30-35, cluster ovate, ca. 2 mm across, sessile; filaments ca. 0.5 mm long; anthers broadly obovate, ca. 0.5 mm long, apex emarginate, dehiscing through short pore-like slits in upper half. Female flower: pedicel ca. 2 mm long; ovary narrowly ovoid with dense glandular hairs, ca. 3.5 × 1.5 mm, wings 3, equal, hardly developed, locules 3, placental branches 2 per locule; tepals 5, white, broadly lanceolate, ca. 3.2 × 1.7 mm, margin entire, apex rounded; styles and stigma not seen. Fruits pendent, 10–11 × 9–11 mm, circular in outline; pedicel 9–11 mm long, slender and recurved; capsule ca. 9 × 5 mm, narrowed proximally and distally, glabrous, locules 3, wings equal, 2–3 mm wide, thinly papery, splitting between the wings and locules. Seeds barrel-shaped, ca. 0.3 mm, collar cells more than half of the seed length.

Distribution: — MALAYSIA. Borneo. Sarawak. Marudi District: Gunung Mulu National Park. Endemic in the Melinau limestone, only from the Melinau Gorge and the Sungai Melinau.

Habitat: —Common in riparian forest at ca. 70 m elevation, on sandy banks or on limestone rocks.

Etymology: —Greek xiphos = sword; phyllos = leaf, oides = similar to, referring to the very narrow leaves like those of Begonia xiphophylla .

Additional specimens examined (paratypes): — MALAYSIA. Borneo. Sarawak. Marudi District: Gunung Mulu National Park – Melinau Gorge, Abang Mohtar S 49655 ( AAH, K, KEP, L, MO, SAN, SAR) ; Sungai Melinau below Melinau Gorge , Kiew 299 ( K, KEP) , 321 (K, KEP); sub-camp 5, Melinau Gorge , Lewis 308 ( SAR) , Lewis 329 ( SAR) ; Bukit Pantu, Julaihi et al. S 74882 ( SAR) .

Notes: —The extremely narrow leaves about five times longer than wide resemble those of Begonia xiphophylla , which also shares the same type of inflorescence that is sessile with one or two female flowers from the leaf axis and a raceme of very small male flowers above, but it differs in its smaller size of its stature, leaf, inflorescence and fruit (see diagnosis above) and in its habitat. Begonia xiphophylloides is only known from riparian forest below 100 m while B. xiphophylla has been collected from rocky habitats (but not from limestone) in mixed dipterocarp forest at higher elevation (350–660 m). The extensive fibrous root system and wiry stem of B. xiphophylloides suggests that it may be rheophytic but its leaves are too soft to be able to withstand water currents.

Figures

FIGURE 17. Begonia xiphophylloides. A. branched habit; B. lower leaf surface; C. male inflorescence; D. male flower bud; E. open male flower; F. stamen cluster; G. stamen; H. fruit; I. TS ovary; J. seeds. All from RK 267, drawn by Joseph Pao.