Description from Flora of China
Habenaria bassacensis Gagnepain; H. lacei (Rolfe ex Downie) Gagnepain; Pecteilis bassacensis (Gagnepain) Tang & F. T. Wang; P. lacei (Rolfe ex Downie) Tang & F. T. Wang; P. susannae (Linnaeus) Rafinesque subsp. henryi (Schlechter) Soó; Platanthera lacei Rolfe ex Downie.
Plants slender to robust, 50-70 cm tall. Tubers oblong, ca. 3.5 × 1.5 cm. Stem stout, with 1 to several tubular sheaths at base, with 4-6 or more leaves and several amplexicaul sterile bracts above. Leaves ligulate-oblong to lanceolate, 7.5-10(-12) × 2-3.5 cm, apex acute. Sterile bracts usually tightly sheathing stem, narrowly elliptic to lanceolate, 6-10 × 1-1.5 cm, apex acute. Rachis 5-8 cm, laxly 4-7-flowered; floral bracts foliaceous, narrowly oblong-lanceolate, 3-4 cm, exceeding ovary, apex acute. Flowers white, large; pedicel and ovary 25-45 mm, shallowly winged, glabrous. Dorsal sepal oblong-ovate, 15-20 × 8-15 mm, apex obtuse; lateral sepals spreading, oblong-ovate, slightly oblique, 15-20 × 6-14 mm, apex obtuse. Petals erect to spreading, oblanceolate to linear, slightly oblique, 12-18 × 1-2.5 mm, apex subacute; lip broadly flabellate, 20-25 × 15-25 mm; disk with 1 small, convex callus near base; lateral lobes broadly cuneate-ligulate to nearly rhombic, 15-20 × ca. 14 mm, apical margin and outer lateral margins deeply lacerate-fimbriate, inner lateral margins entire; mid-lobe linear-ligulate, 15-22 × ca. 3 mm, slightly fleshy, entire, apex slightly obtuse; spur pendulous, often distinctly curved forward, slender, 8-11.5 cm × 1-1.5 mm, attenuate toward apex. Fl. Jul.
Forests, grasslands, gullies; 1000-1900 m. S Yunnan [Cambodia, Laos, Myanmar, Thailand, Vietnam].