Plant relatively slender, 20-50 cm tall with 6-11 flowers in a lax spike. Sepals pale green (occasionally with a rose-coloured tinge), or the lateral ones distinctly bicoloured (pale green/pale purplish brown) with the midvein constituting a boundary, 8-11 × 4-5 mm. Petals yellowish green to olive-green (often suffused with rust-red), 5-9 × 1.5-2.5 mm, approximately half as wide as the sepals. Lip with brown ground colour, now and then provided with a narrow light brown to yellow margin, entire with rounded to truncate base, 5-9 × 7-10 mm, shorter than the dorsal sepal, the basal part shortly velvety to subglabrous, the distal part (sub)glabrous; front edge rounded to shortly acuminate with a short terminal point; bulges weakly developed to obliquely conical (but each of them at most one fourth as large as the stigmatic cavity); mirror H-shaped (rarely a little more complicated). Eye-like knobs of the column dark.