Pterostylis tasmanica

Detailed description

Tuberous, terrestrial spring to summer-green, glabrous orchid either solitary or growing in loose groups. Plants at flowering up to 180 mm tall. Stem wiry, smooth, enclosed in 3–(6) foliaceous leaves. Rosette leaves (4)–8–(18); petiole 6–15 mm long, distinctly winged; lamina 15–25 × 6–8 mm, yellow-green to dark green, broadly ovate, elliptical to elliptical-lanceolate, acute. Cauline leaves 1–2, narrower and broadly sheathing (closely embracing the stem). Flower 1–(2), up to 25 mm long, clearly separated from subtending foliaceous bract; translucent green with dark green longitudinal and transverse veins, brownish towards galea apex and lateral sepals, galea erect in proximal ⅔ then obliquely erect or curved forwards nearly at 90 degrees. Dorsal sepal 18–23 × 12–13 mm, inflated at base and tapered to apex, with a short filiform apex 0.5–1.5 mm long. Lateral sepals deflexed; conjoined part 7–9 × 3–4 mm, tapered to c. 2 mm across at the base, with a thickened, dark green central pad, the margins incurved; free points 7–11 mm long, linear, usually brown, parallel or slightly divergent, apex subacute. Petals asymmetric, falcate 15–20 × 1.5–2.0 mm, dark green, narrowed in distal ½ to an attenuate, long-acuminate apex. Labellum prominent, protruding from sinus, arching, 13.0–15.0 × 0.5 mm, linear-filiform, clad for most of its length in long yellow plumose cilia, apex terminated by a dark brown, glabrous, somewhat irregular, spheroidal, knob-like callus 2.0 × 1.3 mm. Column erect, 12–14 mm long; column wings 4–5 mm long, basal lobe 1.5 × 1.0 mm, set at an angle of 20 degrees, inner margins incurved, sparsely white ciliate, apex obtuse; mid-section 3 mm long, transparent; apical lobe 1.8 mm long, shortly rostrate. Pollinia 2 mm long, yellow, oblong, mealy. Capsule asymmetrical, 1.2–1.6 × 6.0–8.0 mm, obovoid.