Begonia dioica Buch.-Ham. ex D.Don [sect. Diploclinium], 1825

Tian, Dai-Ke, Xiao, Yan, Li, Yan-Ci & Yan, Ke-Jian, 2020, Several new records, synonyms, and hybrid-origin of Chinese begonias, PhytoKeys 153, pp. 13-35 : 13

Begonia dioica Buch.-Ham. ex D.Don [sect. Diploclinium] Fig. 1 走茎秋海棠 (Chinese name)

Begonia dioica Buch.-Ham. ex D.Don [sect. Diploclinium ] D. Don, Prodr. Fl. Nepal. 223. 1825: 223; R. Camfield & M. Hughes, Eur. J. Taxon. 396: 35. 2018.

Description.

Tuberous, creeping, stoloniferous, dioecious, deciduous herb, 3-11 cm high. All plant parts glabrous. Tubers 2-3 (1-2 old, one new). Stolon: usually one to three developing from previous year’s tuber, red, slender, 5-60 cm long, 1-2 mm thick, usually unbranched, rarely branched or towards the apex with many fibre-like branches in large individuals, one to many tiny white aerial bulbs on stolon tips, gradually turning red after stolons touch moss or rock surface. Stipule: lanceolate, 3-4 × 1-2 mm, glabrous, caduceus. Leaf: 1 per plant, basal, petiole green to red, 1-22 cm long, 1.5-5 mm thick, adaxially shallowly grooved along the full length; lamina narrowly deltate-ovate, basifixed, symmetric, 2.5-17 × 1.5-10 cm, upper surface green, underside green, pink green or red, venation palmate, 8-9, green to red, adaxially impressed, abaxially prominent, tertiary even secondary veins invisible; base shallowly cordate, auricles non-overlapped, margin crenate to dentate or double serrate; apex acuminate. Inflorescence: cymose, usually 1, terminal, 8-22 cm long, rachis pink to red, 6-10 cm long, 1-2 mm thick; peduncle branched up to three times, primary 5-10 cm long, secondary and tertiary 3-5 mm long, with 2-5 female flowers or 3-5 male flowers. Bract: lanceolate 2-8 × 1-2 mm, caduceus. Male flower: pedicel 10-25 mm long; tepals 4; outer tepals ovate-orbicular, 6-15 × 5-10 mm, pink to red, margin entire; inner tepals elliptic, 4-8 × 2-4 mm, white to pale pink; androecium with 15-20 stamens; filaments 1-2 mm long, unequal, fused at base into a short column; anther obovate, 1 mm long, dehiscing via short slits near the tip, not hooded, connective not extended. Female flower: pedicel 12-30 mm long; bracteoles absent; tepals 3 (occasionally 2), persistent, outer two larger, elliptic-ovate, nearly equal, 6-15 × 6-10 mm, pink to red, inner one smaller, lanceolate, 6-7 × 3-5 mm, white to pink; ovary 3-locular, placentae bifid; styles 3, persistent, deeply forked once and spirally 1.5-2 circled. Fruit: pendulous, capsule ellipsoid, 7-10 × 6-8 mm; wings 3, unequal or nearly equal, red or reddish-green, rounded-triangular, 2-6 × 7-12 mm, stalk red, 15-40 mm long, 0.8-1 mm thick.

Specimen collected from China.

Xizang (Tibet): Chentang Zhen of Dingjie Xian, 27°50'54.11"N, 87°26'30.70"E, alt. 2427 m, on rock surface and tree trunks. 19 Sept 2017, Daike Tian, Yan Xiao and Zhu Lu TDK3306 (CHS).

Distribution and phenology.

Southern Xizang of China, northern Pakistan, northern India, Nepal and Bhutan; alt. 1350-2430 m; Flowering July to September, fruiting August to November.

Conservation status.

Least Concern (LC). Begonia dioica has numerous suitable habitats throughout its distribution range ( Camfield and Hughes 2018). However, it should be considered as Critically Endangered (B2ab(v)) for China at the country level because only one population has been found so far and a continuing decline in the number of mature individuals is predicted due to road construction and other human’ activities.

Remarks.

Most of the individuals develop long stolons only from tubers formed in the previous year. The stolons are often branched in large individuals and the branch tops produce one to many tiny whitish bulbs, which grow larger as they touch the surface of a rock, tree trunk, soil or moss and then can develop into small plants in the second year. The tepals of female flowers are always persistent, even as the fruits mature.

Figures

Figure 1.. Habitat and morphology of Begonia dioica (Photos by Daike Tian) A, B habitat (rock-moss surface and tree trunk, arrows indicate begonia plants) C individuals with long red stolons (arrows indicate stolons) D plants of different size and stolons with small whitish aerial bulbs (arrows indicate tiny bulbs) E leaves showing glabrous adaxial (upper) and abaxial (low) surfaces F female flowers with three tepals (upper: adaxial view, low: abaxial view) G cross-section of ovary with bilamellate axile placenta and three locules H tubers under moss.