Begonia flagellaris Hara [sect. Diploclinium]

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 flagellaris Hara [sect. Diploclinium] Fig. 2 鞭状秋海棠 (Chinese name)

Begonia flagellaris Hara [sect. Diploclinium ] J. Japan. Bot. 48(12): 358-359, f. 3 (1973).

Description.

Tuberous, stoloniferous, dioecious, deciduous herb, 2-20 cm tall. Tubers usually 2-4 (1-3 old, red-brown, one new, white) connected, 3-15 mm diameter. Stolon: developing from underground tubers or inflorescence; usually one per plant, green, unbranched to rarely branched, glabrous, slender, 10-50 cm long, 2-5 mm thick, aerial bulbs produced at stolon tips, 1-5 mm thick. Leaf: usually one basal large and none to several smaller cauline (on stolons or peduncles), petiole green, 2-28 cm long, 1.5-7 mm thick, sparsely hairy; lamina basifixed, symmetric or nearly so, cordate, 2.5-26 × 1.2-28 cm, adaxial surface green, with short warty-base hairs, underside pale green, sparsely hairy; venation palmate, 9-11, green, adaxially impressed, abaxially prominent, base cordate, auricles non-overlapped to slightly overlapped, margin irregularly serrate to occasionally double serrate, rarely one to few shallowly lobed; apex acuminate. Inflorescence: simple umbellate, 1-2 from the lower part of the stem, 6-20 cm long, rachis green to pink, 4-17 cm long, 2-3 mm thick; peduncle nearly erect, glabrous. Male flower: white to pinkish, pedicel 14-28 mm long, 1 mm thick, top sparsely hairy; corolla 18-24 × 10-12 mm, tepals 4, outer 2, ovate, subequal, 7-12 × 7-11 mm, upper one centre thick and concaved, adaxially white hairy, up 1 mm long, less hairy on lower tepal; inner 2, glabrous, obovate to obovate-lanceolate, 7 × 4-5 mm; androecium leaning towards upper tepal, stamens 10-14, filaments free, about 1 mm long, anther elliptic, up to 1.5 mm long, 0.8 mm wide, apex obtuse. Female flower: pedicel 20-35 mm long, 1 mm thick; tepals 5, unequal, glabrous; ovary hairy, 3-locular, placentae bifid; stigmas and styles 3. Fruit: pendulous, capsule ellipsoid, 6-9 × 4.5-5 mm; wings 3, unequal, green, adaxially wing extremely long, narrowly triangular, 10-28 × 5-7 mm, lateral wings extremely narrow to nearly absent; stalk red at lower part, 24-40 mm long, 1 mm thick.

Specimen collected from China.

Xizang: Jilong Xian, Jilong Zhen, under bamboos, 28°21'41"N, 85°21'12"E, alt. 2030 m, 23 Sept 2017, Daike Tian, Yan Xiao and Zhu Lu, TDK3343 (CHS); on steep slope under forest or rocky hill, 28°21'48"N, 85°21'43"E, alt. 2360 m, same date, Daike Tian, Yan Xiao and Zhu Lu, TDK3344 (CHS).

Distribution and phenology.

China: Xizang, Jilong Xian, Jilong Zhen, border of China and Nepal; Nepal. Alt.1650-2900 m. Flowering August to September (early October), fruiting September to November.

Conservation status.

Near Threatened (NT). Begonia flagellaris is distributed in both Nepal and China, and there are many individual plants in each population. However, this species should be considered as Endangered (B1ab(iii)) for China because only two populations have so far been found and both are by the roadside.

Remarks.

Stolons develop from underground tubers or the top of inflorescence (usually on larger plants), with several small leaves. Hara ( Hara 1973) compared the similarity between this species and B. picta J.E.Smith ( Smith 1805); however, the two are quite different in appearance. Begonia flagellaris is mostly similar to B. adscendens C.B. Clarke (1890: 26), but differs mainly by having long stolons and more hairs on the outer tepals of the male flowers.

Figures

Figure 2. Habitat and morphology of Begonia flagellaris (Photos by Daike Tian) A, B habitat (rock hill or under bamboos, arrows indicate begonia plants) C individuals with long stolons D flowering plant E individual with aerial bulbs on stolon tips (arrows indicate tiny aerial bulbs) F fruit with extremely unequal wings G large individual with stolons (arrows indicate stolons) and fruits H simple umbellate inflorescence with white male and female flowers I infructescence J male flowers in front, dorsal and side views, respectively K cross-section of an ovary with the bilamellate axile placenta and three locules L underground tubers.