Description from Flora of China
Phaius albus Lindley in Wallich, Pl. Asiat. Rar. 2: 85. 1831; P. marshallianus (H. G. Reichenbach) N. E. Brown; Thunia marshalliana H. G. Reichenbach.
Plants, terrestrial or epiphytic. Stem erect, terete, 30-100 cm tall, somewhat stout, usually with ca. 10 leaves, base with several amplexicaul sheaths, completely enclosed in leaf sheaths. Leaf blade narrowly elliptic or narrowly elliptic-lanceolate, 10-20 × 2.5-5 cm, papery or herbaceous, apex acuminate or long acuminate, with amplexicaul sheaths at base, articulate; sheaths persistent, tubular, 2-4 cm, becoming scarious. Rachis 4-10 cm, 2-7-flowered; floral bracts persistent, broadly elliptic to elliptic, cymbiform, large, 3-5 cm, papery. Flowers large, white, lip yellow [or white] and with orange or chestnut spots and stripes; pedicel and ovary 2.5-3 cm. Sepals narrowly oblong, 4-5 × ca. 1.5 cm, apex acuminate. Petals similar to sepals in size, slightly narrower; lip broadly ovate-oblong or broadly oblong-pandurate, 4-5 × 2.5-3 cm, irregularly fimbriate or erose, simple, apical margin crisped; disk with 5-9 shortly dentate-fimbriate ridges; spur cylindric, ca. 1 cm × 3-3.5 mm, apex obtuse. Column ca. 2 cm. Capsule ellipsoid, ca. 4 × 2 cm. Fl. Jun. 2n = 36, 38, 40, 42, 44, 80.
The Chinese material belongs to Thunia alba var. alba; T. alba var. bracteata (Roxburgh) N. Pearce & P. J. Cribb, from Bhutan, NE India, and Nepal, is distinguished by the lack of a yellow patch on the lip.
Lithophytic on rocks or epiphytic on lower branches of trees in forests or in shaded and rocky places; 1200-2300 m. SW Sichuan, SE Xizang, S, SE, and W Yunnan [Bhutan, NE India, Indonesia, Malaysia, Myanmar, Nepal, Thailand, Vietnam].