Viola xinchengensis Y. Nong & G. Y. Wei 2025, sp. nov.

Viola xinchengensis Y. Nong & G. Y. Wei sp. nov. Chinese name. xīn chéng jǐn cài (忻城堇菜). Diagnosis. Viola xinchengensis is most similar to V. lucens, but differs from the latter by its stipules margin long fimbriate-dentate (vs. fimbriate-dentate), stolon absent (vs. stolon slender, often producing a new plant at the top) and sepals 4–6 mm, glabrous (vs. 2.5–3 mm, villous). Viola xinchengensis is similar to V. fargesii, but it can be easily distinguished by its pedicels sparsely white villous (vs. densely spreading white puberulous) and sepals 4–6 mm, glabrous (vs. 7–9 mm, puberulous). More detailed morphological differences amongst the three similar species are shown in Table 2. Type. China • Guangxi: Xincheng, 23°59'42"N, 108°44'28"E, alt. 370 m, on the cliff at the bottom of a sinkhole, 20 April 2024, Y. Nong NY 2024042002 (holotype GXMI! 051188; isotypes IBK!). Description. Perennial herbs, small, 5–10 cm tall; rhizome erect, sometimes elongate, with short internodes, ca. 2 mm, lateral stem and stolon absent. Leaves nearly basal; stipules adnate to petioles for about 1 / 8 at base, brown, lanceolate, 5–7 mm × 1–2 mm, margin long fimbriate-dentate, apex acuminate. Petiole 1.5–3.5 cm, villous, narrowly winged only in the upper part. Leaf blade ovate, 1.5–2.5 cm × 1.5–2 cm, apex acute, base cordate, margin crenate, both surfaces densely villous. Pedicels much exceeding the leaves, glabrous or sparsely villous, 2 - bracteolate above middle; bracteoles opposite, linear, 6–8 mm, margin villous. Sepals ovate-lanceolate, entire, 4–6 mm, apex acuminate, basal auricles short, ca. 2 mm, glabrous. Flower 1.0– 1.5 cm in diameter, petals 5, white with purple or purplish, posterior and lateral ones oblong-obovate, ca. 7–8 mm × 3–5 mm, narrow at the base, lateral petals white with purple, lateral ones bearded, anterior one boat-shaped, 5–8 mm (spur included); spur saccate, short, 1.5–2 mm, ca. 2 mm in diam. Anthers ca. 1.2 mm, connective appendages ca. 0.5 mm; nectariferous glands broadly triangular, ca. 0.5 mm. Ovary ovoid, glabrous; style clavate, base slightly geniculate, thickened upwards, slightly flat at the apex, conspicuously margined on lateral sides, shortly beaked in front, with a stigma hole open upwards at the tip of the beak. Cleistogamous flowers ca 1.5 mm long; bracteoles linear, 6–8 mm, margin villous, acuminate at the apex. Sepals green, entire, 4–6 mm, apex acuminate. Petal 1, ovate, white with purple, 1.0– 1.5 cm long. Capsule ovoid, dehiscence explosive, ca. 5 mm, glabrous. Seeds brown, ovoid, 1 mm, densely covered with tubercles. Phenology. Flowering and fruiting from April to June. Etymology. The specific epithet “ xinchengensis ” refers to the type locality, Xincheng County (忻城县), which is situated in central Guangxi, southwest China. Distribution and habitat. The new species is known only from central Guangxi, China (Fig. 5). It has been found mainly on the cliff at the bottom of a sinkhole at elevations of 370 m. It usually grows with Begonia pseudoleprosa C. I Peng & al. and Primulina sclerophylla (W. T. Wang) Yan Liu on the damp cliffs. IUCN Red List Category. Data available for the new species are still insufficient to assess its conservation status. According to the IUCN Criteria (IUCN 2022), it is considered Data Deficient (DD) until more information becomes available. Although Viola xinchengensis currently has relatively good growth, further collection and monitoring are necessary to allow more conclusive estimations about the rarity and vulnerability of the species. Additional specimens examined (paratypes). China • Guangxi: Xincheng, 23°59'42"N, 108°44'28"E, alt. 370 m, at the bottom of a sinkhole, 26 April 2024 Y. Nong NY 20240042602 (GXMI) • Xincheng, 23°59'42"N, 108°44'28"E, alt. 370 m, at the bottom of a sinkhole, 12 June 2024 G. Y. Wei WGY 20240061201 (GXMI). Taxonomic notes. Viola xinchengensis lacks bulbils, lateral stems and stolons. Stipules are adnated to petioles for about 1 / 8 at base, membranous, glandular-lacerate. Bottom petal is 7–12 mm long, including the spur. Style apex margined and flattened. According to the study of Viola (Marcussen et al. 2022), V. xinchengensis belongs to V. sect. Plagiostigma subsect. Diffusae W. Becker.