Citation: R. Br., Prod. Fl. Nov. Holl. 326 (1810).

Derivation: Greek pteron, a wing; stylos, column.

Synonymy: Not Applicable

Common name: Green-hoods.

Description:
Plants terrestrial, usually glabrous; tubers ovoid to globose, produced close to or at some distance from the parent plant; leaves several, rosette-forming or distributed up the flowering stem, almost orbicular to linear; species which have cauline leaves and no basal rosette on flowering plants do produce rosettes on non-flowering plants.

Flower resupinate, solitary or several in a raceme; floral bract often not differentiated; perianth glabrous or minutely scabrid, mostly green, sometimes with rufous tints; dorsal sepal uppermost, deeply concave and curved, its lateral margins dovetailed into the petals to form with them a hood or galea over the column; lateral sepals (lower lip) connate for part or most of their length, the free lobes diverging widely or narrowly, their tips short or long, acuminate to almost filiform, erect in front of the galea (e.g. fig. 992) or reflexed against the ovary (e.g. fig. 979), adnate to the foot of the column; petals falcate, with the anterior margins shortly adnate to the base of the lateral sepals (e.g. fig. 989), posterior margins free under the dorsal sepal, outer surface with a median longitudinal groove into which the slightly involute margin of the dorsal sepal locks; labellum the smallest of the perianth-segments (e.g. fig. 993), usually included for most of its length, mobile on a claw attached to the column-foot, irritable, projecting from the foot of the column; lamina usually undivided, sometimes with hairs but usually without calli, produced at the line of junction with the claw into an appendage that is usually strap-shaped and more or less laciniate at its free end (e.g. fig. 978A); column elongate, its foot more or less adnate to the base of the dorsal sepal (e.g. fig. 979), beating on either side of the rostellum a more or less quadrangular partly twisted wing, sometimes narrowly winged below; its base more or less produced into a horizontal foot; anther terminal (e.g. fig. 979), pollinia 2 per cell, crescentic, soft but coherent, inclined over the rostellum, with a movable attachment within a cavity in the column, pointless; pollinia powdery, elongated, free; stigma of 2 lobes, usually vertically elongated and occupying the middle of the column (e.g. fig. 991A); rostellum immediately below the anther and high above the stigma with which it is connected by a narrow groove.

Distribution:  About 70 species mainly Australian, represented also in New Zealand, New Guinea and New Caledonia. Of 19 species in New Zealand 6 are common with S. Aust.

Biology: Flowers pollinated by small flies or fungus gnats.

Taxonomic notes: Jones & Muir in Nicholls (1969) Australian Orchids record P. xingens (Rupp)D.L. Jones, (1976) Orchadian 5, 5:54 from near Port Elliot, S. Aust. but the collection they refer to is immature and doubtfully of this hybrid. P. acuminata R. Br. par. ingens Rupp, Proc. Linn. Soc. N.S.W. 53:552 (1928).

Key to Species:

1. Labellum filiform (beset with long yellow hairs)	P. plumosa 18.
1. Labellum flattened, at least below
2. Lateral sepals erect, their filiform tips embracing the galea (e.g. fig. 978A)
3. Leaves mostly crowded at the base of the flowering scape into a leafy rosette (e.g. fig. 984) (stem bracts leaf-like on P. foliata)
4. Labellum 2-fid at the tip	P. concinna 5.
4. Labellum entire at the tip
5. Flower nodding (facing downwards)	P. nutans 17.
5. Flower erect (facing forward)
6. Labellum twisted towards the tip; galea greater than 3 cm long	P. curta 7.
6. Labellum straight or curved but not twisted
7. Inflexed central tooth in the sinus formed by the lateral sepals; galea less than 1.5 cm long	P. nana 16.
7. No inflexed tooth in the sinus between the lateral sepals; galea 1-6 cm long
8. Galea 1-3 cm long
9. Stem bracts leaf-like; labellum linear-oblong, curved forward	P. foliata 12.
9. Stem bracts inconspicuous; labellum ovate, not curved forward	P. pedunculata 21.
8. Galea 4-6 cm long
10. Sepals with at least 15 mm long filiform tips; labellum lanceolate	P. furcata 13.
10. Sepals, acuminate tips less than 10 mm long and not filiform; labellum oblong-elliptical	P. cucullata 6.
3. Leaves cauline or reduced to bracts, basal rosette absent at flowering
11. Stem leaves reduced to bracts; flowers usually 2 to many; galea less than 1 cm long
12. Flowers wholly green, facing each other; ovary longer than the perianth-segments	P. aphylla 2.
12. Flowers brown and green, not facing each other; ovary smaller than the perianth-segments	P. parviflora 20.
11. Stem leaves present; flower usually single; galea more than 1 cm long
13. From the galea the dorsal sepal produced into a 8-10 mm long filiform point	P. tenuissima 27.
13. From the galea the dorsal sepal obtuse or produced into an acuminate or short-filiform tip less than 8 mm long
14. Labellure tip obtuse; sinus between the lateral sepals bulging and protruding forward	P. obtusa 18.
14. Labellum tip acute to acuminate; sinus between the lateral sepals not bulging or protruding forward
15. Labellum as short as the column and not protruding through the sinus between the lateral sepals
16. Plant usually less than 10 cm tall, stem robust; cauline leaves more than 3 cm long; galea 25-45 mm long, more than 20 mm diam	P. robusta 24.
16. Plants 8-25 cm tall, stem slender; cauline leaves less than 3 cm long; galea 20-25 mm long, less than 18 mm diam	P. alata 1.
15. Labellum much longer than the column and protruding through the sinus between the lateral sepals
17. Labellum more than 10 mm long, thick-textured, gradually narrowed into a subacute apex	P. erythroconcha 10.
17. Labellum less than 9 mm long, thin-textured, abruptly narrowing into an acuminate apex	P. dolichochila 9.
2. Lateral sepals reflexed against the ovary, their filiform tips spreading or recurved (e.g. fig. 979.)
18. Leaves cauline, leaf rosette absent at flowering
19. Labellum tip 3-fid; lateral sepals narrow, to 5 mm wide	P. longifolia 14.
19. Labellum tip 2-fid; lateral sepals 11-12 mm wide	P. vittata 28.
18. Leaves mostly crowded at the base of the flowering scape into a rosette (e.g. fig. 981.)
20. Labellum glabrous
21. Basal appendage of the labellum bent forward (as letter C)	P. cycnocephala 8.
21. Basal appendage of the labellum bent backwards (as letter S)	P. mutica 15.
20. Labellum with setae or hairs
22. Labellum thin-textured, almost membranous
23. Basal appendage of the labellum, except a pair of elongated setae near the base of the labellum lamina	P. biseta 3.
23. Basal appendage of labellum beset with setae; no pair of elongated setae near the base of the lamina	P. ovata 19.
22. Labellum fleshy
24. Lateral sepals shortly acuminate, margins much incurved
25. Galea less than 15 mm long; lateral sepals less than 5 mm broad; flowers with maroon or purplish tints	P. pusilla 23.
25. Galea more than 15 mm long; lateral sepals 5-10 mm broad; flower with red and brown tints	P. rufa 25.
24. Lateral sepals produced into long filiform tips; margins not much incurved
26. Labellum more than 2.2 mm broad, shallowly channelled below	P. xerophila 29.
26. Labellum less than 2 mm broad, deeply channelled below
27. Base of lateral sepals c. 10 mm broad, cordate, the margins commonly thickened, usually with numerous setae on the outer surface; labellum apex depressed	P. boormanii 4.
27. Base of lateral sepals narrowed, ovate, less than 9 mm wide, the margins not thickened, usually a few setae or none; labellum apex straight
28. Galea less than 16 mm long; labellum setae yellowish, numerous; lateral sepals strongly recurved near the base	P. setifera 26.
28. Galea more than 16 mm long; labellum setae white, usually sparse; lateral sepals straight near the base	P. excelsa 11.

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