This new species is similar to P. baileyana and P. rotundifolia, but it differs from them in having roots with hairs, straight petiole remaining from the previous year, leaf blade reniform and revolute at the margin, petiole more than 3 times the length of the leaf blade, scape equal to or shorter than the leave, flower solitary at the apex of the scape, capsule shorter than the calyx.

China. Xizang: Motuo City, Duoxiongla, growing in moist rock crevices covered with moss. 31°04'N, 103°11'E, elevation ca. 3607 m, 18 May 2021, W. B. Ju & X. Li YLZB07293 (holotype CDBI!; isotypes KUN!, PE!).

A perennial plant with a short stock, or up to 2.0 × 1.0 cm, usually girt at the base by the straight and withered petioles. Roots reddish, tuft of wiry, woody on maturity, covered with grayish hairs. Bud scales usually girt at the base by imbricate ovate-oblong to ovate with pale-yellow farinose on the abaxially surface. Leaves including the petiole 1.2–12.5 cm long; leaf blade reniform or suborbicular, but mostly reniform, 0.3–1.5 × 0.4–2.3 cm, firm papery or subleathery, glabrous and with potentially farinose glands above, copious pale-yellow farina on the lower surface, margin dentate revolute on the lower surface, with a deeply cordate to occasionally truncate base, lateral veins 3–4 pairs; petioles 0.9–11.0 cm long, reddish brown, glabrous, slightly broadened and membranous towards the base. Scape 1, sparsely short-stalked glandular, 3.0–10.5 cm tall, erect, hardened in fruiting, usually with a single flower; bracts linear-lanceolate, 0.2–0.5 cm long; pedicels 0.2–1.2 cm long, sparsely short-stalked glandular, not extended in fruit. Flowers heterostylous. Calyx campanulate, 5–8 mm long, glabrous outside, green, inside of pale-yellow farinose, parted nearly to base; lobes lanceolate, margin entire, apex acute, veins 3 with not prominent. Corolla pinkish-purple with a golden-yellow eye, annulate; limb 15–25 mm across, funnelform; lobes spreading, 6–11 × 5–10 mm, broadly obovate, deeply emarginate. Thrum flower: corolla tubes 10–15 mm in length, 2–3 mm in diameter, 2 times the length of calyx, widely ampliated above insertion of stamens; stamens situated at the near apex of the corolla tube; style 3–4 mm. Pin flower: corolla tubes 9–13 mm in length, 2–3 mm in diameter, 2 times the length of calyx; stamens inserted at the middle of corolla tube, style as long as tube. Capsule broad-ovoid to globose, shorter than calyx, dehiscence by apical valves. Seeds numerous, free within capsule at maturity, irregularly ovoid-quadrate or pyriform, ca. 0.5–0.8 mm, brown, testa reticulate.

Flowering occurs in May to June; fruiting at the end of June.

The specific epithet refers to the administrative county name of the type locality viz Motuo (Medog) county in southeast Xizang Autonomous Region, China.

The new species is currently known only from its type locality in Lage, Motuo (Medog) county, Xizang Autonomous Region. It grows in the cracks of steep wet cliffs covered with moss, at elevations of 3550–3700 m.

China, Xizang Autonomous Region, Motuo County, Duoxiongla, it grows in the cracks of steep wet cliffs covered with moss, at elevations of 3626 m, 31 May 2015, Bo Xu & X.M.Zhou YLZB01705 (CDBI!).

Currently, only one population have been found. The size of the Lage population remains unknown. According to the IUCN red list criteria (IUCN 2019), the conservation status of the new species should be better categorized as ‘Data Deficient (DD)’. Further explorations in the adjacent mountainous tracts are necessary for an adequate assessment.

Section Cordifoliae is a small group within the genus Primula that has undergone multiple revisions. Currently, it includes several species such as P. baileyana Kingdon-Ward, P. caveana W.W.Smith, P. gambeliana Watt, P. macklinae A.J.Richards (not validly published), P. littledalei I.B.Balfour & Watt, P. ramzanae Smith & Fletcher and P. rotundifolia Wallich (Richards 2003). These species primarily inhabit the tree-line on mountain rocks of the southern slopes of the Himalayas, at altitudes ranging from 3300 to 6000 meters. The most western species, P. ramzanae, is exclusively found in Phoksumdo Lake in western Nepal. The most eastern species in this section is one incompletely known species P. macklinae, found in northern Myanmar. P. littledalei extends from the southern slopes to Lhasa in the Xizang Autonomous Region, and together with P. baileyana is only found in China. The species represented by P. rotundifolia, P. gambeliana, P. caveana are from central Nepal through Sikkim to Bhutan and Tibet. The distribution area of the new species overlaps with P. baileyana and P. littledalei of this section, which is the lowest elevation distribution except P. macklinae.

Morphologically, P. medogensis shares certain similarities with P. baileyana and P. rotundifolia, both of which also belong to P. sect. Cordifoliae. These similarities include mealy, deciduous plants arising from substantial resting buds, the base of the leaf cluster often has many withered petioles, leaf blades are usually reniform or suborbicular, base cordate, with a conspicuous petiole, corolla pinkish-purple, calyx campanulate, with splitting to below middle, capsule horny (Figs 1–3). However, this new species has a series of morphological characters unique to the section that consists of straight old petioles at the base, petioles 3–7 times longer than the leaf blades, leaf blades mostly reniform with revolute margins, single flowers, and scape shorter than or equal to the leaves. In addition to the unique features described above, P. medogensis clearly differs from P. baileyana by roots clothed in dense grayish hairs, pale- yellow farinose, smaller leaf blades, calyx lobes with 3 veins, and capsules shorter than the calyx; and it differs from P. rotundifolia by its smaller leaf blades, corolla lobes deeply emarginate, the capsule broad-ovoid to globose and shorter than the calyx. For a comprehensive overview of the contrasting characteristics between P. medogensis, P. baileyana, and P. rotundifolia, please refer to Table 1.

Figure 1. 

Habitat of the Primula medogensis sp. nov. (A–D)

Figure 2. 

Primula medogensis sp. nov. A fresh plants B pressed specimen C thrum flower D pin flower E leaves F plants base, showing roots, bud scales and petioles G roots covered with greyish hairs H bud scales I capsule J seed.

Figure 3. 

Primula medogensis sp. nov. A habit B leaves C bud scales D flowers: thrum flower, pin flower, and front of the flower E calyx and ovary F capsule.