Begonia delicata is similar to Begonia alchemilloides A. DC., differing by the presence of a ring of trichomes at the apex of the petiole, stipules and first order bracts with entire margin (vs. laciniate) and staminate flowers with 2 (vs. 4) tepals.

BRAZIL. Bahia: São Felipe, Serra da Copioba, 12°50'50"S, 39°05'22"W, Jun 1953 (fl, fr), G. Pinto 53–55 (holotype: ALCB!).

Annual herb, 11–15.5 cm high, monoecious, villous to glabrescent, provided with three types of trichomes, simple, slender trichomes, 1–2.6(–4.5) mm long, trichomes with thickened base, 0.3–0.8 mm long and microscopic, and sparse glandular trichomes. Stem 6–8 mm diam., rhizomatous, prostrate, fleshy, pilose, covered by stipules; internodes 1–3 mm long. Stipules 0.7–0.75 × 0.3–0.35 cm, ovate, apex long-apiculate, margin entire, with minute hairs to essentially glabrous, carinate, appressed, persistent. Leaves: petiole 3.5–9 cm long, cylindrical, villous to glabrescent, ring of trichomes at apex ca. 4 mm long; blade 3.5–7.8 × 4–9.2 cm, reniform, entire, symmetric to slightly asymmetric, basifixed; base cordate; apex rounded; margin crenate, ciliate; sparsely pilose to glabrescent on both surfaces, trichome scars with thickened base, concolorous, light green; venation actinodromous, 7–9 veins at base, membranaceous. Inflorescence: dichasial cyme 9–20 cm long, 4–14-flowered; peduncle 7–17,5 cm long, pilose and glandular; first order bracts ca. 1.5 × 0.8 mm, lanceolate, apex apiculate, margin entire, carinate, persistent. Staminate flowers: pedicel 9–12 mm long, sparsely glandular to glabrous; tepals 2, white, 6–7 × 5.5–6 mm, ovate to elliptic, apex acute to obtuse, margin entire, glandular on abaxial surface; androecium actinomorphic, stamens 16–22, filaments 0.2–0.4 mm long, free, anthers 1.5–2 mm long, rimose, connective prolonged. Pistillate flowers: tepals 5, [only seen in bud]: bracteoles 2, opposite, at base of ovary, lanceolate, persistent [only seen in bud]; styles 3, ca. 0.5 mm long, bifid, branches spirally-arranged, stigmatic papillae covering branches, stigmatic surface papillose, yellow; ovary 7.5–8.2 mm long, trilocular, placentation axile, placenta bifid [obtained from capsules]. Capsules ca. 12 × 13 mm [including wings], three-winged, sparsely glandular, dehiscing at the basal portion; wings unequal, larger ones ca. 14 × 5 mm, apex rounded, smaller ones ca. 12 × 3 mm, rounded. Seeds ca. 0.2 mm long, elliptic to oblong.

(paratype). BRAZIL. Bahia: São Felipe, Serra da Copioba, 12°50'50"S, 39°05'22"W, Oct 1950 (fl), G. Pinto 587 (RB!).

The epithet refers to the fragility and delicacy of the plant.

Begonia delicata occurs exclusively in the Recôncavo region (Fig. 2). It is known by only two collections, both from Serra da Copioba, the most recent made in 1953, growing on rocks covered by moss. It has not been found in conservation unit.

Found flowering in June and October, and with fruits in June.

Begonia delicata is a small herb easily recognised by the rhizomatous stem covered in stipules, the petioles with a ring of trichomes at the apex, and by the reniform leaf-blades, with crenate margins. Few Brazilian Begonia are delicate herbs and, amongst those species, Begonia alchemilloides and Begonia hoehneana Irmsch. (state of São Paulo) are those that most resemble the new species. Begonia delicata, however, can easily be distinguished from both species by the presence of a ring of trichomes at the apex of the petiole and by the staminate flowers with fewer tepals (2 vs. 4). Moreover, the stipules and first order bracts are entire, whereas in Begonia alchemilloides they are laciniate, and the leaves are crenate whereas in Begonia hoehneana they are dentate. Among the species that occur in Bahia, Begonia hirtella Link most closely resembles Begonia delicata (see the key below), but can be distinguished by its habit (prostrate in Begonia delicata vs. erect in Begonia hirtella), the stipules and first order bracts (entire vs. fimbriate), the ring of trichomes at the apex of the petiole (present vs. absent) and the shape of the leaf-blades (reniform vs. ovate). According to the sectional classification of Doorenbos et al. (1998), Begonia delicata would belong to the sect. Doratometra (Klotzsch) A. DC., which consists of approximately ten annual species, with inconspicuous flowers in relative small inflorescences and two bracteoles below ovary.