Description from Flora of China
Thelaia rotundifolia (Linnaeus) Alefeld.
Herbs 15–25(–30) cm tall. Rhizome long, slender, branched, producing adventitious roots and aerial stems at nodes; aerial stems 15–30 cm, ribbed, with a basal rosette of crowded leaves, and higher up with 1 or 2 oblong-ovate sheathing, scalelike, brownish bracts. Rosulate leaves 4–7, semievergreen; petiole ca. 2 × or ca. as long as blades; leaf blade slightly green abaxially, green adaxially, slightly shiny, orbicular to ovate, (2–)3–6 × (1.5–)2.5–5.5 cm, leathery, base sometimes subcordate, margin obscurely crenate or nearly entire, apex rounded. Rachis-inserted scale-shaped leaves 1 or 2; raceme 8–15-flowered, 6–16 cm. Pedicel 4.5–5 mm; bracts axillary, imbricate, lanceolate, membranous. Flowers spreading or rarely nodding, 1.5–2 cm in diam., widely opened, fragrant (scent of Convallaria majalis Linnaeus). Sepals ovate-lanceolate to lanceolate, 3.5–5.5 mm, reflexed at tip, apex rounded. Petals incurved, pure white, orbicular-ovate, 6.5–10 × 4–6 mm, rather thick, apex obtuse. Stamens arched toward upper side of flower; filaments glabrous, anthers yellow, tubules present. Style 7.5–10 mm, deflexed at base and facing lower part of corolla, dilated at apex into a ring. Capsule (6–)7–8 mm in diam. Fl. Jun–Jul, fr. unknown.
According to Haber (Syst. Bot. 8: 277–298. 1983), one of the main areas of taxonomic difficulty in Pyrola occurs in P. sect. Pyrola (see Křísa, Bot. Jahrb. Syst. 90: 476–508. 1971, for sectional subdivisions). The type of the section is P. rotundifolia Linnaeus, a white-flowered species common throughout Europe and eastward to just beyond Lake Baikal in Siberia (cf. Hultén, Amphi-Atlantic Pl. map 123. 1958). Numerous taxa, both white- and pink-flowered, have been recognized as segregates of this widespread species, or described as distinct but related to P. rotundifolia. The assessment of taxonomic affinities within this “complex” has been problematic because of the lack of clear morphological discontinuities (Haber & Takahashi, Bot. Mag. (Tokyo) 101: 483–495).
Picea forests, mountain thickets, grassy slopes; 1400–3200 m. Gansu, ?Hebei, ?Jiangsu, ?Liaoning, ?Ningxia, ?Shaanxi, Sichuan, N Xinjiang (Altay), Xizang, Yunnan [Japan, Mongolia, Myanmar, Russia; Europe].