Pterostylis irwinii

Detailed description

Terrestrial tuberous herb growing in diffuse colonies. Plants dimorphic. Sterile plants 60–100 mm tall; 2–3-leaved; leaves linear, 40–120 × 30–50 mm, dark green, entire acuminate. Flowering plants 150–200 mm tall, stems reddish. Leaves 3–5, cauline, widely spaced, spreading; lamina linear, 60–170 × 4–5 mm, dark green to bronze-green, glossy beneath, sessile, sheathing at base; margins entire; apex acuminate. Pedicel 20 mm long, slender. Ovary linear, 10–13 mm long, ribbed, reddish or red-brown. Flower solitary, 35–45 × 10–12 mm, erect, translucent white and dark green with red to red-brown suffusions in the apex of the galea and lateral sepals; galea shallowly gibbous at the base then erect before bending forwards, the apex erect to obliquely erect, the dorsal sepal much longer then the petals. Dorsal sepal ovate-lanceolate in outline when flattened, 43–48 × 14–16 mm, expanded near the base then tapered to the long-acuminate or attenuate apex. Lateral sepals obliquely erect to erect, hardly embracing the galea, leaving a very wide lateral gap to the petal margins, much of the labellum visible through this gap; upper part of sinus flat when viewed from the side, with a deep, relatively wide central notch when viewed from the front; internally the sinus projecting inwards as a small platform-like projection; conjoined part 14–16 × 8–10 mm, prominently scabrid, narrowed to 2.5 mm wide at base, tapered into the free points; free points 24–27 mm long, involute, tapered, erect, the tips extending above the galea. Petals obliquely linear-lanceolate, 30–33 × 3–4 mm, strongly falcate, long-acuminate, green with white stripes, red-brown toward the apex. Labellum erect, curved forwards in the distal third, the apex protruding prominently through the sinus in the set position; labellum hinge ligulate, 3 × 2 mm; lamina oblong-lanceolate, 15.0–18.0 × 3.2–3.5 mm, red-brown; apex subobtuse to acute; callus raised, 0.7 mm wide near apex; basal appendage 3.0–3.5 mm long, penicillate. Column 14–16 mm long, bent away from the ovary at 35 degrees at the base then erect, green and white; column foot 4 mm long. Column wings 6–7 mm long; basal lobe 3 × 1 mm, at an angle of about 35 degrees; apex obtuse; inner margins incurved, sparsely and shortly ciliate; mid-section 3 mm long, green; apical lobe 1.3 mm long, linear,obtuse. Stigma narrowly scutiform 3–4 × 2 mm, medial on the column, raised. Anther 1.8 mm long, very shortly rostrate. Pollinia linear-falcate, 1.5–1.8 mm long, yellow, mealy.