B. sphenantheroides

Herbs monoecious, perennial, erect, 50–150 cm tall. Rhizomes congested, 15–25 mm across, to 9 cm long; erect stem stout, 5–20 mm across, internodes 7–30 cm, glabrous. Stipules caducous, triangular or narrowly so, apex aristate or apiculate, margin entire, glabrous. Leaves alternate, petiole to 20–30 cm long, glabrescent (puberulent when young); leaf blade herbaceous, asymmetric, ovate to broadly ovate, 21–41 cm long, 15–28 cm wide, glabrous or subglabrous, base obliquely cordate, margin irregularly loosely serrulate or denticulate; apex acute or short acuminate; venation 7- or 8- palmate. Inflorescences 2–3 (–7)-flowered, protandrous; peduncle 1–5 cm long, scaberulous; bracts deciduous, narrowly ovate to lanceolate, apex acuminate, margin entire, 0.9–1.8 cm long, subglabrous. Staminate flower: pedicel 0.7–1.5 cm long, scabrous; tepals 4, outer 2 reddish, oblong, ovate or orbicular, 0.8–1.9 cm long, 0.5–1.5 cm wide, abaxially scabrous, inner 2 pinkish, broadly oblanceolate to oblong, 0.5–1.7 cm long, 0.3–0.9 cm wide, glabrous; androecium actinomorphic, subglobose, 0.7 cm across, stamens 70–120, yellow, clavate; filaments 0.7–2 mm long, fused to a short central column; anthers 1.5–1.8 mm long, apex truncate. Carpellate flower: pedicel 1.5–2.2 cm long, scabrous; ovary green, unequally 3-winged, wings red, scabrous, 2-locular; placentae axile, bilamellate; tepals 5, reddish, unequal, elliptic to obovate, 0.9–1.8 cm long, 0.5–1.5 cm wide, apex obtuse, abaxially scabrous; styles 2, ca. 5 mm long, 2-cleft, fused at base, stigmatic band wavy-twisted and spiralled. Capsule nodding, unequally 3-winged, abaxial wing falcate, 5–16 mm tall, ca. 7 mm wide, lateral wings triangular or narrowly so, 3–6 mm tall. Begonia sphenantheroides is assignable to section Platycentrum. It bears a superficial resemblance to B. roxburghii A. DC. (section Sphenanthera) in the erect and branched stems, differing by being onoecious (vs. dioecious) and the broadly ovate leaf blade (vs. triangular-ovate), carpellate flower with 5 tepals (vs. 4 or rarely 3), abaxially scabrous (vs. glabrous) tepals, 2-styled pistil (vs. 4-styled), 2-locular ovary (vs. 4-locular), setose capsule (vs. glabrous or puberulent) and unequally 3-winged (vs. wingless, 4-horned) capsule. Most members of section Platycentrum are rhizomatous or with short aerial stems that appear only at anthesis. Begonia sphenantheroides has upright stems all year-round, a feature not frequently encountered in sect. Platycentrum. In the greenhouse, we observed some abnormally developed tubular pistillate flowers (Fig. 9:M) like those of sect. Symbegonia (Warb. 1894: 149) L. L. Forrest & P. M. Hollingsworth (2003: 208), which was probably induced by the cultivated condition.

• Classification: Species
• Plant Type: Unknown
• Botanical Section: Platycentrum
• Origin: Asia, NE Vietnam
• Originator: C.-I Peng
• Date of Origin: 2015