Common name: Collared Greenhood
Pterostylis torquata D.L.Jones APNI*
Synonyms: Diplodium torquatum (D.L.Jones) D.L.Jones & M.A.Clem. APNI*
Description: Terrestrial herb
Sterile and fertile plants dimorphic. Rosettes borne by sterile plants only, leaves 3–5; lamina ovate, 15–25 mm long by 10–15 mm wide, dark green, margins entire, apex subacute; petioles 5–15 mm long.
Scape 10–20 cm tall, slender, smooth; stem leaves 4 or 5 , obliquely erect, lanceolate, 15–40 mm long by 4–7 mm wide, margins entire, apex acuminate. Ovary 10–14 mm long, grey-green, smooth. Flower solitary, 18–21 mm long by 7–9 mm wide, erect, translucent white with dark green and dark brown suffusions and stripes, the upper margin of the sinus with a prominent dark brown band; apex of the galea shallowly decurved. Dorsal sepal 30–35 mm long by 12–15 mm wide, slightly inflated at the base then uniformly tapered; apex acuminate with a filiform point to 1.5 mm long. Lateral sepals erect, tightly embracing the galea; sinus protruding as a prominent knee in side view, sinus flat or shallowly raised at the middle in front view, folded internally; conjoined part 10–13 mm long by 11–15 mm wide, narrowed to c. 2 mm across at the base; upper margins inrolled, abruptly tapered into the filiform free points 15–20 mm long, held erect or slightly recurved high above the galea. Petals obliquely oblanceolate, 23–28 mm long by 5–7 mm wide, falcate, dilated distally; margins entire; apex acute; flange broadly deltate c. 1 mm wide, obtuse. Labellum erect, curved forwards and obliquely erect in the distal third, mostly dark brown-black but whitish or greenish toward the base; apex just extending above the sinus in the set position; claw c. 3 mm long by 1.4 mm wide; lamina narrowly elliptic-oblong, 8.5–10.5 mm long by 2.0–2.5 mm wide, broadest near the middle and tapered toward each end; apex obtuse; basal appendage linear, 2–3 mm long, recurved sharply near the middle, apex penicillate.
Distribution and occurrence: Northern Tablelands of New South Wales (vouchered), and northern coast south to the Newcastle area (Blackbutt Reserve – unvouchered).
In Wet sclerophyll forest up to 1200 m elevation.
NSW subdivisions: NT
Pterostylis torquata could be confused with P. atrans or P. obtusa. Pterostylis torquata differs from P. atrans in the upper margin of the sinus knee is horizontal, and nearly level, and the knee itself is very narrow with an interal angle approaching 45 degrees; whereas in P. atrans the upper margin of the knee is slightly inclined and slopes toward the ground, and the knee itself is broader with an internal angle closer to 90 degrees. In P. atrans the fuscous pigmentation is confined to the galea, the sinus margins are green. Pterostylis atrans has slightly clavate lateral sepal tips, those of P. torquata are filiform. Pterostylis torquata is very similar to P. obtusa, the two species essentially differ only in flower colour, which includes fuscous pigmentation on the galea and around the sinus in P. torquata, but not in P. obtusa. Plants with and without pigmentation may co-occur.
Text by Matt A.M. Renner (16 Dec 2019) based on Jones (1997)
Taxon concept: Jones DL (1997) Six new species of Pterostylis R.Br. (Orchidaceae) from Australia. The Orchadian 12(6): 245–258.
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