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Genus Pterostylis Family Orchidaceae

Synonyms: Diplodium Sw. APNI*
Oligochaetochilus Szlach. APNI*
Plumatichilos Szlach. APNI*
Crangonorchis D.L.Jones & M.A.Clem. APNI*
Eremorchis D.L.Jones & M.A.Clem. APNI*
x Taurodium D.L.Jones & M.A.Clem. APNI*
Taurantha D.L.Jones & M.A.Clem. APNI*

Description: Terrestrial herbs, sympodial; roots filamentous; tuberoids paired and often also produced at apices of stolons.

Leaves basal or scattered along the stem, several per shoot, convolute, petiolate or sessile.

Inflorescence racemose, 1–several-flowered, terminal; flowers resupinate. Dorsal sepal adherent to lateral petals to form a helmet (galea), about as long as lateral sepals. Lateral sepals basally fused, often erect and embracing the galea. Lateral petals shorter or rarely longer than dorsal sepal. Labellum free, attached to column foot by a short, irritable claw; lamina not lobed or less frequently 2[–4]-lobed, usually with a basal appendage and sometimes with a terminal knob. Column lacking free filament and style; column wings fused to column, expansive in upper half, where they are usually 2-lobed, broad. Column foot much shorter than column. Anther erect to incumbent, persistent. Pollinia 4, soft and mealy. Stigma entire, situated at about the middle of the column. Rostellum ventral.

Distribution and occurrence: World: c. 120 species, Australia, New Zealand, New Caledonia, New Guinea. Australia: c. 100 species (most species endemic), all States except N.T.

We do not to recognise the following genera segregated from, or resurrected from synonymy under Pterostylis by Jones & Clements (2002, Australian Orchid Research volume 4): Bunochilus, Crangonorchis, Diplodium, Eremorchis, Hymenochilus, Linguella, Oligochaetochilus, Petrorchis, Pharochilum, Plumatichilos, Ranorchis, Speculantha, Stamnorchis, Taurantha, Urochilus. Those authors justified recognition of these genera on the grounds that their phylogenetic analysis showed these taxa all to be monophyletic and that each was supported by some morphological characters. However, as these authors also noted, Pterostylis, as traditionally circumscribed, is also a monophyletic group that is strongly supported by both morphological and molecular data. Therefore, there was no grouping problem to resolve by recircumscribing genera that were not monophyletic. The insights into relationships gleaned from molecular and morphological data can as well be enshrined within the Linnean hierarchy at the level of subgenus, without disruption of established concepts, and numerous name changes.
The key below is based on the previous PlantNet key, Jones (2006)'s Bunochilus revision. It is a beta version and was put up online on 30 January 2020. No key of this scope for such an intricate group of plants is ever perfect – if you identify any errors or omissions, or can suggest improvements please use the Contact Us link on the green banner above. Note added 8 April 2020: Thank you to Lachlan Copeland and Gavin Phillips for providing couplets for the Speculantha group, and many other correspondents so far, for identifying errors and omissions in both key and descriptions.

Text by D. L. Jones, updated by Peter Weston (March 2007) and Matt A.M. Renner (8 April 2020).
Taxon concept: D.L. Jones (1993, Flora of New South Wales vol. 4)

Taxa not yet included in identification key
Pterostylis bicornis,    Pterostylis crebra,    Pterostylis falcata,    Pterostylis furva,    Pterostylis jeanesii,    Pterostylis sp. Botany Bay (A.Bishop J221/1-13)

 Key to the species 
1Lateral sepals deflexed away from the galea2
Lateral sepals erect and embracing the galea46
2Labellum lamina filiform with an apical knob and numerous long yellow trichomes [Plumatochilos]3
Labellum flat, lacking an apical knob and yellow trichomes
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3Galea bearing a rostrum at its apex, around 4 mm longPterostylis plumosa
Galea without a rostrum, or with a short rostrum at its apex, to 1.5 mm long
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4Labellum with trichomes more or less equal maximum length from base to near tip, extending at even density from base to near the apical callusPterostylis tasmanica
Labellum with trichomes shortening toward the apex, and becoming sparse in the vicinity of the apical callus
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Pterostylis sp. Botany Bay (A.Bishop J221/1–13)
5Labellum with each lateral lobe developed as large basal extension, appearing as a marginal ridge causing the labellum base to appear furrowed; rosette leaves attached to a growth arising laterally from the base of a scapePterostylis daintreana
Labellum lacking lateral lobes or with poorly developed lateral lobes that do not extend basally; rosette either stem-encircling or only on non-flowering plants
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6Stem leaves well-developed and spreading, rosette only developed on non-flowering plants [Bunochilus]7
Stem leaves reduced and tightly sheathing the peduncle, rosette leaves encircling the base of a scape
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7Petal flanges reduced or absent, not blocking off the internal base of the galea.8
Petal flanges present, large, projecting and blocking off the internal base of the galea.
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8Synsepalum elliptic, petals with reduced basal flanges, the anterior margin straight or shallowly curved9
Synsepalym ovate, petals without basal flanges, then anterior margin broadly curved
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9Labellum appearing hairy with transparent acicular siliceous cells over most of its surface10
Labellum not appearing hairy, transparent acicular cells confined to the labellum base, or absent
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10Flowers 10–13 mm long, labellum midlobe 0.5–1.0 mm longPterostylis longifolia
Flowers 14–18 mm long, labellum midlobe 1.0–1.6 mm long
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Pterostylis major
11Labellum cream to pale yellow, with a conspicuous dark central stripe12
Labellum wholly dark, brown or blackish, central stripe inconspicuous
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12Labellum with numerous acicular cells at the base13
Labellum with few acicular cells at the base
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13Flowers dark green with bright orange-brown tips on the sepalsPterostylis jonesii
Flowers pale green with light-brown tips on the sepals
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14Flowers 12–15 mm long, labellum midlobe c. 1 mm longPterostylis melagramma
Flowers 17–20 mm long, labellum midlobe 1.5 mm long
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Pterostylis lineata
15Labellum with a long recurved apical lobe on the basal moundPterostylis barringtonensis
Labellum with a short erect lobe on the basal mound
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Pterostylis loganii
16Flowers 17–20 mm long, labellum 5–7.5 mm long, midlobe 1.5 mm long.Pterostylis chocolatina
Flowers 7–15 mm long, labellum 3.5–5.0 mm long, midloe 0.5–1.0 mm long
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17Labellum without any acicular cellsPterostylis parca
Labellum base with a few short acicular cells
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Pterostylis tunstallii
18Labellum equal width throughout, pale green with a darker stripePterostylis macrosepala
Labellum widest toward apex, brown with a darker stripe
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19Labellum basal mound small, rounded, with a vestigial apical lobePterostylis tenuis
Labellum with a well-developed basal mound and an erect apical lobe
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Pterostylis umbrina
20Galea wider than the oblong synsepalumPterostylis stenosepala
Galea equal in width or narrower than the elliptic synsepalum
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Pterostylis smaragdyna
21Labellum lamina glabrous, thin and membranous, with a well-developed dark-coloured basal appendage, lacking trichomes. Sepals obtuse to acute, apices not drawn out into a filimentous tip. [Hymenochilus]22
Labellum lamina thick and fleshy, covered with transparent siliceous cells, basal appendage absent or poorly developed, margins with spreading trichomes. Sepals acuminate or (usually) drawn out into a filimentous tip. [Oligochaetochilus]
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22Labellum appendage recurved, central lobe not produced into a knob-like structurePterostylis mutica
Labellum appendage erect, central lobe produced into a beak-like structure
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23Labellum appendage dark green, central lobe of appendage prolonged and pointed, forming the 'swan's head'. [P. cycnocephala sens. lat.]24
Labellum appendage blue-black, central lobe of appendage short and blunt. [P. bicolor sens. lat.]
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24Flowers pale translucent green with darker green nerves. Rosette leaves elliptic, 10–35 mm long by 5–25 mm wide. Less robust plants of sclerophyll forest and grassland Pterostylis cycnocephala
Flowers opaque white, strikingly lined in well-defined mid- to dark-green lines along the nerves. Rosette leaves broadly ovate to elliptic, 25–45 mm long by 10–25 mm wide. More robust plants of alpine and subalpine grassland and herbfield
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Pterostylis crassicaulis
25Labellum obovate to oblong, with a black-green appendage. Taller stature plants from forests and grasslands.Pterostylis bicolor
Labellum elliptic, with short thick black appendage. Smaller stature plants with more densely crowded racemes of alpine grassland and herbfield.
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Pterostylis clivicola
26Labellum with 2 prominent basal trichomes 2.5–6 mm long, arising near the base and directed forwards27
Labellum lacking 2 prominent, erect basal trichomes, those trichomes present in basal area less than 2 mm long
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27Basal lobe of the labellum c. 3 mm long, filamentous tips of lateral sepals c. 10 cm or more longPterostylis woollsii
Basal lobe of the labellum c. 1 mm long, filamentous tips of lateral sepals less than 2 cm long
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28Flowers transparent with dark brown markings, labellum obovatePterostylis maxima
Flowers transparent with green or light brown markings, labellum elliptic-oblong
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29Plants diminutive, 5–8 cm tall, sepal tips usually in contact with the groundPterostylis despectans
Plants robust, 7 to 35 cm tall, flowers held well clear of the ground and not in contact with it.
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30Plants with clumping habit. Pterostylis pedina
Plants solitary.
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31Taller growing habit (scape to 25 cm tall), narrower galea (not measured), longer free points on sepals (7–21 mm long), smaller petals (c. 13 x 5 mm), and shorter (5–6 mm) oblong labellumPterostylis biseta
Shorter growing habit (scape 9–15 cm tall), wider galea (not measured), shorter free points on sepals (14–20 mm long), larger petals (16–19 mm x 5–6 mm), and longer (7–9 mm) oblong-elliptic to elliptic labellum
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Pterostylis petrosa
32Labellum margins scalloped inwards between trichomesPterostylis lingua
Labellum margins flat between trichomes
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33Lateral sepals reflexed back against the ovary, flower green with a contrasting darker labellum34
Lateral sepals deflexed, not reflexed back against the ovary, flowers various colours and shades, labellum not contrasting against green flower.
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34Labellum with 4 or 5 setae on each side, generally only one of which is prominent. Lateral sepals filiform for around one third their lengthPterostylis gibbosa
Labellum with 6 to 8 setae on each side. Lateral sepals filiform for around one half their length.
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Pterostylis mitchellii
35Tips of lateral sepals hooked forwards36
Tips of lateral sepals deflexed or curved gently forwards, not hooked
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36Proximal flanges of petals not meeting leaving a gap, labellum wholly visible from the sidePterostylis setifera
Proximal flanges of petals meeting and blocking off the base of the galea, labellum not or only partially visible from the side
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37Flower c. 1.2 cm longPterostylis calceolus
Flower c. 2 cm long
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Pterostylis hamata
38Dorsal sepal with a filiform point 8 mm or more long39
Dorsal sepal with a filiform point 3 mm long or less
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39Labellum widest near the base and tapered to the apex, lateral sepals deeply concave, the labellum not visible from the side in the set positionPterostylis boormanii
Labellum widest at or above the middle, lateral sepals flat to shallowly concave, the labellum visible from the side in the set position
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40Margins of lateral sepals densely ciliate, free points of lateral sepals 5–6 mm long, curved forwardsPterostylis cobarensis
Margins of lateral sepals glabrous or nearly so, free points of lateral sepals 7–20 mm long, deflexed or swept backwards
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Pterostylis chaetophora
41Labellum obovate, 4.5–5 mm long42
Labellum oblong, c. 4 mm long
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42Labellum broad-obovate, marginal trichomes 3–5 pairsPterostylis saxicola
Labellum narrow-obovate, marginal trichomes 12–14 pairs
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Pterostylis praetermissa
43Flowers noddingPterostylis rufa
Flowers more or less erect
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44Outer third of lateral sepal margins folded inwards and nearly touching beneath the labellumPterostylis pusilla
Lateral sepals folded inwards at the very margins only
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45Flowers c. 4 mm wide, green and light brown, dull, lateral sepals swept backPterostylis aciculiformis
Flowers c. 7 mm wide, reddish brown, shiny, lateral sepals deflexed
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Pterostylis squamata
46Flower solitary (rarely 2)47
Flowers 2 or more, rosette leaves attached to a growth arising laterally from the base of a scape [Speculantha]
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47Rosette leaves borne by non-flowering and flowering individuals, though in the latter these may be more diffusely distributed up the base of the scape, dimorphism among flowering and non-flowering individuals therefore incomplete or absent. [Pterostylis]48
Rosette leaves developed on non-flowering plants only, absent from flowering plants, dimorphism among flowering and non-flowering individuals therefore complete. [Diplodium]
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48Rosette leaves petiolate, tightly grouped at the base of the scape50
Rosette leaves sessile, grouped in a loose spiral in the basal third of the scape
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50Labellum apex conspicuously notched51
Labellum apex entire
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51Labellum apex just visible, not protruding through the front of the sinus in the set positionPterostylis concinna
Distal third of labellum protruding conspicuously through the sinus in the set position
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52Flower 2–2.5 cm longPterostylis conoglossa
Flower 3–5 cm long
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53Rosette leaves dull, flower semi-nodding, lobes of labellum notch nearly parallelPterostylis ophioglossa
Rosette leaves shiny, flower erect, lobes of labellum notch widely spreading
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Pterostylis collina
54Labellum not protruding through the front of the sinus in the set position, either the tip just visible or the whole labellum enclosed and not visible55
Distal quarter to third of the labellum protruding through the front of the sinus in the set position
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55Sepals all with filiform points of similar lengthPterostylis pedoglossa
Dorsal sepal much shorter than the lateral sepals
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56Lateral sepals tightly embracing the galea, no lateral gap visiblePterostylis nana
Lateral sepals loosely embracing the galea, leaving a lateral gap
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57Apex of galea horizontal or decurved, labellum ovatePterostylis pedunculata
Apex of galea obliquely erect, labellum ovate-oblong
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58Flower 12–20 mm longPterostylis erecta
Flower 14–17 mm long
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Pterostylis oblonga
59Apex of labellum acuminatePterostylis acuminata
Apex of labellum obtuse to subacute
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60Flower conspicuously nodding61
Flower erect to semi-erect, not conspicuously nodding
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61Flower c. 2.5 cm long, labellum 12–16 mm longPterostylis nutans
Flower c. 1.5 cm long, labellum 9–13 mm long
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Pterostylis hispidula
62Flowers 5–6 cm long, erectPterostylis baptistii
Flowers semi-erect, 2–3.5 cm long
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63Labellum scabrid, distal half protruding from the sinus in the set positionPterostylis x ingens
Labellum smooth, the tip to distal quarter protruding from the sinus in the set position
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64Flower c. 3.5 cm long, labellum tip twisted prominently to one sidePterostylis curta
Flower 2–2.5 cm long, labellum tip straight (not twisted)
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Pterostylis hildae
65Labellum apex notched66
Labellum apex entire
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66Flower c. 3 cm long, green and white, stem leaves ovatePterostylis furcillata
Flower c. 3.5 cm long, heavily suffused with red, stem leaves lanceolate
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Pterostylis pulchella
67Labellum blue-green, sometimes darkPterostylis oreophila
Labellum dark green to brownish, to blue-black, never blue-green
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68Flower c. 2 cm long, lateral sepals tightly embracing the galea, no lateral gap visiblePterostylis foliata
Flower 3 cm or more long, lateral sepals loosely embracing the galea leaving a lateral gap
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69Flower with dark brown stripes and suffusionsPterostylis riparia
Flower green and white
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70Scape smoothPterostylis furcata
Scape scabrid
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71Flower c. 3 cm long, sinus protruding prominently in an abrupt curve when viewed from the side, free points reflexed behind the galeaPterostylis alpina
Flower 3–5 cm long, sinus protruding in a shallow curve when viewed from the side, free points erect above the galea
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72Galea hood inclined upwardPterostylis aneba
Galea hood more or less level.
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73Sinus broadly and shallowly notched, flowers 40–50 mm longPterostylis monticola
Sinus deeply and narrowly notched, flowers 30–40 mm long
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Pterostylis subtilis
74Dorsal sepal acute to acuminate, lacking a filiform point75
Dorsal sepal with a distinct filiform apical point, at least 4 mm long
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75Petal margins prominently flared, dark red-brown, distal half of labellum linear to filiform with a slightly expanded apex76
Petal margins decurved, green to light brown, labellum tapered in distal half but not linear to filiform, apex acute to subacute
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76Petals dark red-brown, distal half of labellum linear to filiform with a slightly expanded apexPterostylis grandiflora
Petals green, distal half of labellum broad, with an obtuse apex
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Pterostylis hians
77Flower c. 2 cm long, lateral sepal points erect, labellum strongly curvedPterostylis longicurva
Flower 4–5 cm long, lateral sepal points widely divergent, labellum shallowly curved
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Pterostylis truncata
78Sinus V-shaped when viewed from the front79
Sinus flat or raised, often with a small central notch when viewed from the front
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79Labellum not protruding from the sinus in the set position, apex obtuse, truncate or slightly notchedPterostylis fischii
Labellum protruding from the sinus in the set position, apex long-acuminate
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80Flower erectPterostylis reflexa
Flower semi-erect to semi-nodding
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81Flower 4.5–7 cm long, galea with a long sweeping shallow curve. labellum 18–24 mm longPterostylis ampliata
Flower 2–3 cm long, galea with a short curve, labellum 12–17 mm long
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82Flower pale green and whitePterostylis revoluta
Flower heavily suffused with light brown to dark brown
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Pterostylis longipetala
83Sinus abruptly protruding and platform-like when viewed from the side84
Sinus flat or shallowly mounded or curved when viewed from the side, never platform-like though in some species like P. decurva the sinus does have a protruding knee, the upper margin is not horizontal so does not appear platform like in lateral view.
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84Distal third of labellum protruding from the sinus in the set position85
Labellum tip barely visible through the sinus in the set position
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85Flower bluish green and white, labellum 15–19 mm longPterostylis aestiva
Flower dark green and white, labellum 13–17 mm long
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Pterostylis metcalfei
86Petal margins parallel with top of sinus knee, Sinus J- or U-shaped when viewed from side. Filiform tip to dorsal sepal shorter than petal length above the sinus. Flowers green and white, or if with brown pigments these suffuse and concentrated around the sinus, or on the tip of the galea only. 87
Petal margins inclined toward top of sinus knee, sinus C-shaped when viewed from side. Filiform tip to dorsal sepal longer than petal length above the sinus. Flowers liberally adorned with brown pigments on the galea, sometimes extending to include on surface of synsepalum, lateral sepal tips, and galea.
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87Sepal tips slightly clavatePterostylis atrans
Sepal tips filiform
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88Flower green and white with red-brown suffusions in the galeaPterostylis torquata
Flower green and white only, labellum 9–11 mm long
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89Flowers 2.5–2.8 cm long, sinus protruding, spout-likePterostylis obtusa
Flowers 1.8 cm long, sinus not so markedly protruding, sometimes with margins slightly inrolled
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Pterostylis alveata
90Flower 2–2.5 cm long, green or with warm brown tints around the galea, labellum 11–13 mm long, rosette leaf margins entirePterostylis decurva
Flower 3.5–4 cm long, with intense and often sharply delineated red-brown pigmentation around the galea, labellum 15–17 mm long, rosette leaf margins minutely crenulate
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Pterostylis abrupta
91Flower more than 3 cm long92
Flower 1.5–2.5 cm long
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92Sinus scabrid, labellum protruding prominently from the sinus in the set positionPterostylis coccina
Sinus smooth, labellum tip just visible in the set position
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Pterostylis robusta
93Labellum protruding prominently from the sinus in the set position94
Labellum tip visible in the set position, but not protruding prominently
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94Galea suffused with brown pigments95
Galea not suffused with brown pigments [but P. elegans can have galea suffused with brown pigments, so this couplet construction is not ideal – see the recognition section of P. elegans]
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95Flowers semi-nodding, labellum evenly curved throughout, lateral sepals free tips tending to curve outward and downwardPterostylis laxa
Flower erect, labellum curved forwards suddenly in the distal third, lateral sepal free tips erect.
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Pterostylis decurva
96Labellum longer than column, sinus knee angle less than right anglePterostylis metcalfei
Labellum shorter than column, sinus knee right angled.
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97Dorsal sepal tip 5–8 mm long, labellum 8–11 mm long, flowers darkPterostylis elegans
Dorsal sepal tip 3–5 mm long, labellum 11–14 mm long, flowers bright
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Pterostylis russellii
98Flowers strikingly marked with green, white and dark brown, colours clearly delineated, dark-brown particularly intense around the sinus; upper galea shallowly hooded and rather two dimensional, petals exposed to a width approximately equal that of the dorsal sepal at equivalent point along the galea hood, lower petal margin usually arched inward, following the shape of the dorsal sepal; dorsal sepal ending in a short point to 5 or 6 mm long, but sometimes shorter, pointing forward or downwardPterostylis striata
Flowers marked with green, white, and light-brown, colours not clearly delineated, sinus green, petals green or light brown; upper galea deeply hooded, three dimensional, petals exposed to a width greater than that of the dorsal sepal, particularly near their apex, lower petal margin straight or curved outward, contrary to the shape of the dorsal sepal; dorsal sepal ending in a point 5 or 6 mm or longer, usually pointing downward
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Pterostylis divaricata
99Galea glabrous, not scabrous.100
Galea scabrous, bearing fine ornamentation
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100Flowers less than 7 mm longPterostylis parviflora
Flowers 10–13 mm long
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Pterostylis ventricosa
101flowering from the new replacement tuber while it is still attached to the old tuber, and before the rosette has been developed by the old tuberPterostylis vernalis
Flowering from a mature tuber at the same time or after the rosette has been developed.
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102Flowers up to 8mm longPterostylis uliginosa
Flowers around 10mm long
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103Flowers red and white all over when freshPterostylis amabilis
Flowers only coloured red/brown distally when fresh
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104Flowers marked dark chocolate brown to black distally, not changing colour with age [coastal areas north of Minnie Water]Pterostylis nigricans
Flowers marked reddish brown distally, ageing to a red or pinkish hue [inlands areas south of Peak Hill and Orange]
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Pterostylis rubescens

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