Erect softly hairy much branching herb to c.50 cm high. Stem woody at base, sometimes rooting where nodes touch substrate, densely hairy, internodes 5-13 cm.
Stipules c.10 × 7 mm with a filiform extension at the tip, hairy, semi-persistent. Petioles 2-6 cm long, densely hairy. Leaves very asymmetric, up to 7-17 cm long from base to tip and 3-6 cm wide, midrib 5-13 cm, ovate-lanceolate, venation pinnate-palmate, covered with colourless hairs, margin scalloped and irregularly dentate with a fringe of short hairs, shallowly cordate at the base, pale green.
Male flowers borne in monochasial cymes of c.14 flowers; tepals 2, suborbicular, c.8 × 9 mm, base cordate becoming truncate at maturity, outer surface with a few short colourless hairs, margin slightly fimbriate, white; stamens 45-50, yellow, anthers c.0.75 mm long, dehiscing through short slits near the tip, filaments the same length, slightly fused at the base.
Female flowers borne in pairs; pedicel c.3 mm long; tepals 4, equal, sub-rhomboid, denticulate, white, c.15 × 11 mm; styles 3, twice spirally twisted, yellow, deciduous; ovary 10 × 14 mm with 3 equal wings, truncate across the apex, scattered with colourless hairs, pale green or pink, placentation axile, placentae bifid, wings rounded at the base and acute at the tip.
Fruit c.12 × 16 mm, drying pale brown, dehiscent, capsule oval. Seeds barrel shaped, c.0.3 mm long, collar cells c.2/3 the length of the seed. (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)
Conservation
Proposed IUCN category: VU D2. (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)
Distribution
Asia-Tropical: Sulawesi (Sulawesiendemic)
Endemic to Indonesia, Sulawesi, Sulawesi Gorontalo.
See specimen tab for map of point distribution data of georeferenced specimens.
Etymology
It is unusual in section Petermannia in the female flowers having four rather than five tepals, the rhomboidal tepals giving a cross-shape to the perianth; hence the epithet chiasmogyna (female cross). (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)
see Thomas et al., 2012 (Thomas, D.C., Hughes, M., Phutthai, T., Ardi, W.H., Rajbhandary, S., Rubite, R., Twyford, A.D. & Richardson, J.E. 2012: West to east dispersal and subsequent rapid diversification of the mega-diverse genus Begonia (Begoniaceae) in the Malesian archipelago. – Journal of Biogeography 39: 98-113)
Gorantalo, Nr Gunung Gambuta, 9 iv 2002, M. Mendum, H.J. Atkins, M. Newman, Hendrian, A. Sofyan 46 (E, L); Gorantalo, Gunung Boliohutu, 22 iv 2002, M. Mendum, H.J. Atkins, M. Newman, Hendrian, A. Sofyan 146 (E); Gorantalo, Gunung Boliohutu, 23 iv 2002, M. Mendum, H.J. Atkins, M. Newman, Hendrian, A. Sofyan 167 (holo E) – Type of Begonia chiasmogyna M. Hughes. (Hughes, M. An annotated checklist of Southeast Asian Begonia. 2008)