Description from Flora of China
Didymocarpus rotundifolius Hemsley in F. B. Forbes & Hemsley, J. Linn. Soc., Bot. 26: 230. 1890.
Perennials, stemless. Rhizome internodes inconspicuous. Leaves basal, opposite; petiole 1-4.5 cm X ca. 2 mm; leaf blade orbicular-ovate to orbicular-reniform, 1.6-4.9 X 1.6-5.3 cm, herbaceous, adaxially appressed pilose (hairs to 5 mm), eglandular, base cordate, margin entire to shallowly crenate, apex rounded; lateral veins 3 or 4 on each side of midrib, inconspicuous. Cymes 2-7-flowered; peduncle 4.5-13 cm, pilose; bracts 2, free, narrowly triangular, 4-6 X 0.8-1 mm, puberulent, margin entire, apex acute. Pedicel 1.7-7 cm, glandular puberulent, puberulent, and spreading pilose. Calyx 5-sect from base; segments equal, narrowly triangular to lanceolate-linear, 4-5 X ca. 1 mm, outside pilose, inside pubescent, margin entire, apex attenuate. Corolla purple, 2.3-2.7 cm, outside sparsely puberulent, inside apically pubescent; tube nearly tubular, 1.2-1.7 cm X ca. 8 mm; adaxial lip ca. 5 mm; abaxial lip 7-10 mm. Filaments ca. 7 mm, glandular apically; anthers fused by entire adaxial surfaces, ca. 2 mm, glandular; staminodes 2, ca. 3 mm. Pistil 1.2-1.6 cm, densely glandular puberulent; ovary ca. 7 mm. Stigma obtrapeziform, ca. 1 mm, 2-lobed. Capsule erect, 3-3.5 cm. Fl. and fr. Nov.
After publication of the family treatment for the Flora of China,
this was treated as Primulina rotundifolia (Hemsley) Mich. Möller & A. Weber (Taxon 60: 784. 2011).
* N Guangdong.