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Didymocarpus cordifolius P.W. Li & Li H.Yang, sp. nov. (Figs. 1 & 2) Diagnosis: — Didymocarpus cordifolius is morphologically similar to D. margaritae Smith (1912: 151), but can be easily distinguished by its short petioles with both glandular and eglandular hairs (vs long petioles with eglandular hairs), glandular pubescent peduncles (vs glabrous), short calyx tubes (vs calyx without a tube), pale purple corollas (vs orange corollas with yellow patches on the ventral side), hairy anthers (vs glabrous), and ovary and style of subequal length (vs ovary much longer than style) (Fig. 3A–E). Type:— CHINA. Yunnan: Yuanyang County, Ga’niang Town, near Yangping village, on the moist cliff along the roadside, 23°3'47.96" N, 102°55'2.7" E, 2096 m, 21 August 2021, L.H. Yang & P.W. Li YLH1203 (holotype IBSC!; isotypes IBSC!, PE!). Perennial herbs with annal or monocarpic flowering stems. Stems 1.5–3 cm long, densely woolly hairy, intermixed with short glandular hairs. Leaves 2–4, opposite, distinctly unequal, crowded at stem apex; petioles 0.4–1.2 cm long, densely covered with glandular and eglandular hairs; leaf blade somewhat bullate, broadly ovate to cordate, 3.5–9 × 3–9 cm, base cordate, margin double serrate, apex obtuse or round, adaxially glandular and eglandular pubescent, abaxially glandular pubescent, lanate along veins; lateral veins 4–6 on each side of midrib, conspicuous. Cymes axillary, 1- to 2- branched, 1- to 6-flowered. Peduncles 2.5–6 cm long, glandular pubescent. Bracts 2, free, oblanceolate to oblong, 1–3 × 0.7–1.9 mm, margin entire, apex obtuse, glabrous on both sides. Pedicels 3–6 mm long, glandular pubescent. Calyx 5-lobed nearly to base, tubes 0.5–0.8 mm long, lobes slightly unequal, 1.3–1.7 × 0.7–1 mm, margin with inconspicuous tooth, apex obtuse, glabrous on both sides. Corolla pale purple, glabrous, narrowly tubular; tube 1.4–1.6 cm long, 2–3 mm in diameter; limb distinctly bilabiate, adaxial lip 2-lobed to near base, lobes suborbicular, 2–2.3 × 2.5–2.9 mm; abaxial lip 3-lobed to middle, lateral lobes suborbicular, 3.4–4.4 × 3.6–5 mm, ventral lobe reniform, 4.4–4.6 × 5.6–5.9 mm. Stamens 2, inserted at ca. 1 cm above the corolla base; filaments ca. 3 mm long, glabrous; anthers coherent, glandular and eglandular hairy, thecae divaricate. Lateral staminodes glabrous, ca. 1 mm long, adnate to ca. 6 mm above corolla base; dorsal staminode not seen. Disc ring-like, ca. 0.5 mm high, glabrous. Pistil included, glabrous; ovary linear oblong, ca. 5 mm long; style linear, ca. 7 mm long; stigma disclike. Capsules straight, 1.1–1.8 cm long, bivalved, dehiscing loculicidally. Distribution and habitat:— Didymocarpus cordifolius is currently known from Yuanyang County in Yunnan, China, and more field investigation is needed to explore its distribution range. This species grows on moist cliffs under the forest at an elevation of ca. 2000 m. Phenology: —Flowering from July to August and fruiting from August to September. Etymology: —The epithet “ cordifolius ” refers to the cordate leaves of Didymocarpus cordifolius. The Chinese name for this new species is “xīn yè cháng shuò jù tái 心叶Rffiffȍ ” Additional specimens examined (paratype):— CHINA. Yunnan: Yuanyang County, Ga’niang Township, near Yangping village, 23°3ʹ47.96ʺ N, 102°55ʹ2.7ʺ E, 2096 m, 20 October 2018, L.H. Yang & H.H. Kong YLH834 (IBSC!). Notes: — Didymocarpus cordifolius is similar to D. silvarum in the bullate leaves and the narrowly tubular corollas, but they are quite different from each other in stem length, corolla color, and indumentum type on stems, petioles and anthers (Fig. 3F–H). Didymocarpus cordifolius is also similar to D. andersonii Clarke (1874: 92), which is distributed in eastern Nepal, Bhutan, and northeastern India (Weber et al., 2000), in vegetative characters (Fig. 4). However, the large connate bracts and bracteoles (Fig. 4A–B), the shallowly lobed calyxes (Fig. 4C–D), the narrowly funnel-form corollas (Fig. 4B), and the large limbs (Fig. 4B) of D. andersonii are obviously different from those of D. cordifolius (Figs. 1–2). In addition, Didymocarpus cordifolius is somewhat similar to D. nanophyton C.Y.Wu in Li (1983: 32) in length of petioles, but the eglandular hairy stems, the elongated upper internodes, the bilabiate calyx with a relatively long tube, and the long capsules of the latter species (Fig. 5) are distinct from those of D. cordifolius. The detailed morphological comparison among the five allied species is provided in Table 1.