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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 have chosen 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. The numerous name changes that they proposed for Pterostylis are simply unnecessary. (P.H. Weston March 2007)

Text by D. L. Jones
Taxon concept: D.L. Jones (1993, Flora of New South Wales vol. 4)

Taxa not yet included in identification key
Pterostylis aneba,    Pterostylis atrans,    Pterostylis barringtonensis,    Pterostylis bicornis,    Pterostylis chocolatina,    Pterostylis clivicola,    Pterostylis crassicaulis,    Pterostylis despectans,    Pterostylis elegans,    Pterostylis falcata,    Pterostylis furcillata,    Pterostylis hians,    Pterostylis jonesii,    Pterostylis lineata,    Pterostylis loganii,    Pterostylis macrosepala,    Pterostylis major,    Pterostylis melagramma,    Pterostylis metcalfei,    Pterostylis mitchellii,    Pterostylis oblonga,    Pterostylis oreophila,    Pterostylis parca,    Pterostylis pedina,    Pterostylis petrosa,    Pterostylis rubescens,    Pterostylis smaragdyna,    Pterostylis sp. Botany Bay (Bishop J221/1-13),    Pterostylis stenosepala,    Pterostylis subtilis,    Pterostylis tasmanica,    Pterostylis tenuis,    Pterostylis torquata,    Pterostylis uliginosa,    Pterostylis umbrina,    Pterostylis ventricosa,    Pterostylis vernalis

 Key to the species 
1Lateral sepals erect and embracing the galea; flowers usually 1 or rarely 22
Lateral sepals deflexed away from the galea; flowers usually more than 2 or rarely 245
2Flower solitary (rarely 2)3
Flowers 2 or more, rosette leaves attached to a growth arising laterally from the base of a scape
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3Rosette leaves encircling the base of the scape4
Rosette leaves only developed on non-flowering plants
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4Rosette leaves petiolate, tightly grouped at the base of the scape5
Rosette leaves sessile, grouped in a loose spiral in the basal third of the scape
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5Labellum apex conspicuously notched6
Labellum apex entire
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6Labellum 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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7Flower 2–2.5 cm longPterostylis x conoglossa
Flower 3–5 cm long
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8Rosette 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
9Labellum not protruding through the front of the sinus in the set position, either the tip just visible or the whole labellum enclosed and not visible10
Distal quarter to third of the labellum protruding through the front of the sinus in the set position
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10Sepals all with filiform points of similar lengthPterostylis pedoglossa
Dorsal sepal much shorter than the lateral sepals
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11Lateral sepals tightly embracing the galea, no lateral gap visiblePterostylis nana
Lateral sepals loosely embracing the galea, leaving a lateral gap
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12Flower c. 1.5 cm long, apex of galea horizontal or decurved, labellum ovatePterostylis pedunculata
Flower c. 2 cm long, apex of galea obliquely erect, labellum ovate-oblong
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Pterostylis erecta
13Apex of labellum acuminatePterostylis acuminata
Apex of labellum obtuse to subacute
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14Flower conspicuously nodding15
Flower erect to semi-erect, not conspicuously nodding
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15Flower 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
16Flowers 5–6 cm long, erectPterostylis baptistii
Flowers semi-erect, 2–3.5 cm long
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17Labellum 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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18Flower 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
19Labellum apex notched20
Labellum apex entire
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20Flower c. 3 cm long, green and white, stem leaves ovatePterostylis x furcillata
Flower c. 3.5 cm long, heavily suffused with red, stem leaves lanceolate
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Pterostylis pulchella
21Dorsal sepal acute to acuminate, lacking a filiform point22
Dorsal sepal with a distinct filiform apical point, at least 4 mm long
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22Petal margins prominently flared, dark red-brown, distal half of labellum linear to filiform with a slightly expanded apexPterostylis grandiflora
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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23Flower 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
24Sinus V-shaped when viewed from the front25
Sinus flat or raised, often with a small central notch when viewed from the front
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25Labellum 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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26Flower erectPterostylis reflexa
Flower semi-erect to semi-nodding
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27Flower 4.5–7 cm long, galea with a long sweeping shallow curve. labellum 18–24 mm longPterostylis sp. B sensu Harden (1993)
Flower 2–3 cm long, galea with a short curve, labellum 12–17 mm long
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28Flower pale green and whitePterostylis revoluta
Flower heavily suffused with light brown to dark brown
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Pterostylis longipetala
29Sinus abruptly protruding and platform-like when viewed from the side30
Sinus flat or shallowly mounded or curved when viewed from the side, never platform-like
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30Distal third of labellum protruding from the sinus in the set position31
Labellum tip barely visible through the sinus in the set position
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31Flower bluish green and white, labellum 15–19 mm long (CT, ST)Pterostylis aestiva
Flower dark green and white, labellum 13–15 mm long (NC)
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Pterostylis russellii
32Flower less than 2 cm longPterostylis alveata
Flower more than 2 cm long
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33Flower green and white with red-brown suffusions in the galea34
Flower green and white only, labellum 9–11 mm long
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Pterostylis obtusa
34Flower 2–2.5 cm long, labellum 11–13 mm longPterostylis decurva
Flower 3.5–4 cm long, labellum 15–17 mm long
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Pterostylis abrupta
35Flower more than 3 cm long36
Flower 2–2.5 cm long
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36Sinus 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
37Labellum tip just visible in the set positionPterostylis striata
Labellum protruding prominently from the sinus in the set position
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38Flowers semi-nodding, labellum evenly curved throughoutPterostylis laxa
Flower erect, labellum curved forwards suddenly in the distal third
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Pterostylis decurva
39Labellum dark blue-greenPterostylis dubia
Labellum dark green to brownish, never blue-green
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40Flower 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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41Flower with dark brown stripes and suffusionsPterostylis riparia
Flower green and white
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42Scape smoothPterostylis furcata
Scape scabrid
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43Flower c. 3 cm long, sinus protruding prominently in an abrupt curve when viewed from the side, free points reflexed behind the galeaPterostylis alpina
Flower 4–5 cm long, sinus protruding in a shallow curve when viewed from the side, free points erect above the galea
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Pterostylis monticola
44Flowers c. 7 mm long, green and white; labellum narrow-ellipticPterostylis parviflora
Flowers c. 10 mm long, dark brown, green and white; labellum rhombic
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Pterostylis nigricans
45Labellum lamina filiform with an apical knob and numerous long yellow trichomesPterostylis plumosa
Labellum flat, lacking an apical knob and yellow trichomes
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46Labellum with 2 lateral lobes developed as large basal extensions; 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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47Stem leaves well-developed and spreading, rosette only developed on non-flowering plants48
Stem leaves reduced and tightly sheathing the peduncle, rosette leaves encircling the base of a scape
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48Flowers c. 1.5 cm long, labellum 2.5–3 mm wide, pale green with a blackish central stripe, with numerous transparent, acicular trichomesPterostylis longifolia
Flowers c. 1 cm long, labellum 1.5–2 mm wide, wholly dark brown, with very few transparent, acicular trichomes
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Pterostylis tunstallii
49Labellum lamina glabrous, thin and membranous, with a well-developed dark-coloured basal appendage50
Labellum lamina thick and fleshy, covered with transparent siliceous cells, basal appendage absent or poorly developed, margins with spreading trichomes
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50Labellum appendage erect, central lobe produced into a beak-like structure51
Labellum appendage recurved, central lobe not produced into a knob-like structure
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Pterostylis mutica
51Flowers c. 8 mm long, labellum appendage dark green, central lobe of appendage prolonged and pointedPterostylis cycnocephala
Flowers c. 1 cm long, labellum appendage blackish, central lobe of appendage short and blunt
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Pterostylis bicolor
52Labellum with 2 prominent basal trichomes 2.5–6 mm long, arising near the base and directed forwards53
Labellum lacking 2 prominent, erect basal trichomes, those trichomes present in basal area less than 2 mm long
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53Basal 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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54Flowers transparent with green or light brown markings, labellum elliptic-oblongPterostylis biseta
Flowers transparent with dark brown markings, labellum obovate
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Pterostylis maxima
55Labellum margins scalloped inwards between trichomesPterostylis lingua
Labellum margins flat between trichomes
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56Lateral sepals reflexed back against the ovaryPterostylis gibbosa
Lateral sepals deflexed, not reflexed back against the ovary
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57Tips of lateral sepals hooked forwards58
Tips of lateral sepals deflexed or curved gently forwards, not hooked
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58Proximal 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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59Flower c. 1.2 cm longPterostylis calceolus
Flower c. 2 cm long
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Pterostylis hamata
60Dorsal sepal with a filiform point 8 mm or more long61
Dorsal sepal with a filiform point 3 mm long or less
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61Labellum 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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62Margins 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
63Labellum obovate, 4.5–5 mm long64
Labellum oblong, c. 4 mm long
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64Labellum broad-obovate, marginal trichomes 3–5 pairsPterostylis saxicola
Labellum narrow-obovate, marginal trichomes 12–14 pairs
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Pterostylis praetermissa
65Flowers noddingPterostylis rufa
Flowers more or less erect
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66Outer 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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67Flowers 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

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