Description from Flora of China
Viola diffusa var. brevibarbata C. J. Wang; V. diffusa var. brevisepala W. Becker; V. diffusa var. glabella H. Boissieu; V. diffusa var. glaberrima W. Becker; V. diffusa subsp. tenuis (Bentham) W. Becker; V. diffusa var. tomentosa W. Becker; V. diffusoides C. J. Wang; V. tenuis Bentham; V. wilsonii W. Becker.
Herbs annual, stiffly hairy or white puberulous throughout, or subglabrous, rarely glabrous, producing stolon at anthesis. Stolon with rosulate leaves at top, usually producing adventitious roots. Rhizome short, with numerous white rootlets and fibrous roots. Basal leaves numerous, fasciculate and rosulate, or alternate on stolon; stipules adnate to petioles at base, 2/3 free, linear-lanceolate, 4-12 mm, margin remotely denticulate or fimbriate-dentate, apex acuminate; petiole 2-4.5 cm, conspicuously winged, usually puberulous; leaf blade ovate or ovate-oblong, 1.5-3.5 × 1-2 cm, both surfaces densely white puberulous on young leaves, later gradually sparsely so, but still densely puberulous along veins and margin, or glabrous, base broadly cuneate or truncate, rarely shallowly cordate, conspicuously decurrent to petiole, margin obtusely dentate and ciliate, apex obtuse or ± acute. Flowers purplish or yellowish, small, long pedicellate, in basal leaf axils and leaf axils of stolon; pedicels 1.5-8.5 cm, slender, glabrous or sparsely puberulous, 2-bracteolate at middle; bracteoles linear. Sepals lanceolate, 4-5.5 mm, apex acute, basal auricles short, margin sparsely ciliate, apex rounded or remotely denticulate. Lateral petals obovate or oblong-obovate, 6-8 mm, glabrous or shortly bearded, anterior one ca. 6 mm (spur included), conspicuously shorter than other petals, apex acute; spur very short, only ca. 1.5 mm, slightly exserted out of basal auricles of sepals; spur of 2 anterior stamens triangular, short, broad. Ovary glabrous; styles clavate, slightly geniculate, gradually thickened in upper part; stigmas thickly margined on lateral sides and abaxially, slightly raised in central part, shortly beaked in front. Capsule oblong, 6-7 mm, ca. 3 mm in diam., glabrous, often with persistent styles. Seeds ca. 1 mm. Fl. Mar-May, fr. May-Oct. 2n = 26*, 74*.
Mountain forests, forest margins, grassy slopes, stream valleys, rock crevices; below 2000 m. Anhui, Chongqing, Fujian, SE Gansu, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, S Shaanxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Bhutan, Japan, India, Indonesia, Malaysia, Myanmar, Nepal, Papua New Guinea, Philippines, Thailand, Vietnam].