Begonia filiformis Irmscher (1939: 521)

Hoang, Thanh Son & Lin, Che-Wei, 2023, A new species Begonia wiformis, and a new record of B. filiformis (B. sect. Coelocentrum, Begoniaceae) from nothern Vietnam, Phytotaxa 591 (4), pp. 292-300 : 299

Begonia filiformis Irmscher (1939: 521) ( Figs. 5 & 6 )

Type:— CHINA. Guangxi, Lungchow , N. W. hills, flowers green or white, H. B. Morse 575 (Holotype K; fragments of holotype at B) .

Specimens examined:— VIETNAM. Ha Giang Province, Vi Xuyen District, Minh Tan Commune , 22°58’14”N, 104°53’15”E, 754 m elev., Growing in cracks of mossy rocks on semi-shaded limestone cliffs in evergreen broadleaved forest., 25 March 2022, Hoang Son 6433 ( VAFS, VNMN) .

Notes:— Begonia filiformis is recognized by its rugose ovate leaves, densely glandular-hispid peduncles and flowers with pale green tepals and staminate flowers with an actinomorphic androecium. Begonia filiformis was initially discovered in Lungchow, southern Guangxi. This species has long been suspected to also exist in Vietnam, as existing collections are known from near the Vietnamese border. The specimens referred to in this study were collected within the Vi Xuyen District of Ha Giang Province. There are only two known populations of this species in the area, and neither of them is located within any protected forests ( Fig. 1 ). The Vietnamese population roughly fits morphologically into the type, except that stipules sometimes have an entire margin (vs. shallowly and densely serrate), the tepals are tinged with yellowish-green (vs. pale green to white), and the abaxial wing of capsule is nearly trapezoidal (vs. lunate).

Figures

FIGURE 1. Distribution map of two new species, Begonia wiformis (yellow square) and B. filiformis (blue triangles).

FIGURE 5. Begonia filiformis Irmsch. A. Habit; B, B'. Portion of leaf, upper and lower surfaces; C, C'. Stipule of rhizome and the base of inflorescence; D, D', D'', D'''. Bracts; E, E', E''. Staminate flower, face, side and back views; F, F'. Stamens, dorsal and ventral views; G, G'. Pistillate flower, face and side views; H, H'. Style and stigmatic band, dorsal and ventral views; I. Cross section of an immature capsule, J. Capsule.

FIGURE 6. Begonia filiformis Irmsch. A, B. Habit and habitats; C. Habit; D. Portion of leaf, upper surface, E. same, lower surface; F. Stipules; G. Bracts; H. Staminate flower, face and back views; I. Pistillate flowers, face and side views; J. Immature inflorescence; K. Capsule; L. Cross section of ovary.