[terro-style-iss]
From pteros, a wing, and stylos, a style.

The largest and one of the most interesting genera among Australian orchids, The various species are commonly called "Greenhoods" because of the shape and colour of the flower usually greenish, tinged or streaked with red or brown. The main part of the hood (known botanically as the galea) is formed of the upper sepal and the two lateral petals, lightly attached. The two lower sepals are joined to form a kind of forked door to the front of the hood. The lip usually is irritable, small and tongue like, with a spur at its base, and is placed inside the joined lower sepals. The long column concealed within the hood is winged hence the name Pterostylis.
The genus includes nearly sixty known species, of which over 40 are Australian, and most of these are endemic. It extends to New Zealand, New Caledonia and New Guinea. Species of Pterostylis, owing to the curious formation of the flowers and what one might term their "habits," are of particular interest to botanists and scientists. The genus is mentioned by Darwin in his book on the fertilisation of orchids, as follows:-
"The flap of the labellum is irritable and hangs out below the hood. If an insect lands on it, it instantly moves and imprisons the visitor against the column, and the only mode of escape is by squeezing past the stigma. After half an hour the lip goes down again and is ready for another capture."
This peculiarity is known to most children, who love to touch a sensitive lip and watch its lightning upward spring. P. vittata, commonly called "Cockatoo Orchid," a species common in Western Australia, is a favourite for such demonstrations. Fitzgerald's observations upon the genus and individual species, recorded in his work on Australian orchids, are intensely interesting, as are also the published notes of Dr. R. S. Rogers.
Fitzgerald formed the opinion that, in spite of Nature's marvellous schemes to ensure fertilisation of the various species of. Pterostylis, they are seldom reproduced naturally by seeds, and that the fact of their being found so frequently in groups pointed to reproduction by tubers or leading roots, which may be swept out of the ground by heavy rain-storms, rooted up by animals or ants, and washed or blown away, to vegetate elsewhere. It has been found, however, that many varieties of Pterostylis can be cultivated from seed, as well as by transplantation, quite easily, and healthy plants in various stages of development may be found nourishing in the greenhouses of many orchid lovers.
In Mr. O. H. Sargent, Western Australia has an orchid enthusiast who is not only an accomplished botanist, but a keen student of Nature. From him we learn that the flowers of some species of Pterostylis contain sticky juices that attract and intoxicate visiting insects, thus compelling them to remain within the flower long enough either to effect fertilisation there, or make sure of pollen being attached to body or wings to be carried on subsequently to another flower.
Two species of the genus in P. barbata and P. turfosa, the latter endemic to Western Australia and known as the "Bird orchid," supply a most striking illustration of that characteristic so often quoted as one by which an orchid may be easily recognised
-the difference of the third petal or "lip" to the other two and the sepals. No contrast could be greater than the long and slender thread-like protruberance bearded with bristling hairs, to the solid structure of the rest of the flower.

P. nana, R. Brown; stunted.
"Snail orchid"
A small slender plant. Leaves in a radical rosette, lower stem-leaves heart-shaped, upper ones lanceolate, stem-clasping. Flower over 1/2 in. long, erect, abruptly curved towards the end. Lower part broadly cuneate, about 1-3 in. long without the linear-subulate lobes, the long points embracing the galea. Lip linear, obtuse, about 1/4 in. long. Column half the length of the galea, the wings with a small lanceolate upper lobe or tooth, the lower lobe oblong and obtuse. Favours moist shady places.
W.A.: Albany, Busselton, Highbury, Jarnadup, Mt. Barker. September - October.
New South Wales, South Australia, Tasmania. Victoria.

P. pyramidalis, Lindley; pyramid-like, referring to the foliage growth.
"Gnome orchid" "Green devils" "Sly orchid"
A species of variable size, sometimes nearly 1 ft. high. Leaves usually crowded at base of stem, passing gradually into stem leaves and scales, but the basal leaves are not always present. Flowers green, similar to P. nana. By some botanists this species is not considered distinct from P. nana, plants of intermediate form being often found. Dr. Rogers, however, is of the opinion that the two species are distinct.
W.A.: Albany, Gosnells, Jarnadup. Margaret River, Riverton, Stirling Range, York. August - October.

P. reflexa, R. Brown; bent back. (See P. robusta.)

P. robusta, Roger.; sturdy.
"Shell orchid"
A slender species, plant without any rosette of ovate radical leaves at time of flowering. Stem leaves lanceolate, usually four or five including the floral bract. Flower whitish green with deeper green longitudinal stripes, rather large single. Galea gradually curved forward at the apex; dorsal sepal with a short slender point, lower lip erect, sepals tapering to thread-like points, embracing and much exceeding the galea. Lip irritable, on a movable claw, practically straight lanceolate, tapering into a point, in the erect position very slightly exceeding the column. Column erect, the upper angle of the wing acute, the lower lobe oblong-obtuse with in turned ciliated margins. Prefers shady places and favour coastal districts, frequently being found beneath peppermint trees (Agonis flexuosa). Note by Dr. Rogers: "Apparently with some hesitation, this plant was included by Bentham in P. reflexa, R. Brown. It differs from the latter, however, in its shorter stem, wider leaves, and relatively short, straight labellum which does not protrude through the sinus of the lower lip, as in the sinus of R. Brown's plant."
W.A.: Albany, Ludlow, Margaret River, Swanbourne, York. May - July.
All other Australian States

P. Rogersii, Coleman; honouring Dr. R. S. Rogers, M.A., M.D., F.L.S.
A plant of from 4 to 8 in. in height. Radical leaves not present at time of flowering, stem leaves 4 to 7, lower leaves bract-like. Flower, solitary, translucent white or grey, with red stripes on perianth segments, column and labellum. Galea slightly bent but not abruptly curved. Lower lip erect, sinus acute. Lip on an irritable claw, markedly recurved, protruding through the sinus, lamina tapering to a long obtuse point. Column erect. (Described "Victorian Naturalist," Vol. XLVI., September, 1929.) Favours sandy soil.
W.A.: Augusta, Bunbury, Busselton, Collie, Ludlow, Margaret River. June - July.

P. constricta, Sargent; contracted.
A small one-flowered specis about 3 in. high, first leaves ovate in a radical rosette. F1ower stem slender, flexuose, without radical leaves, but having narrow-lanceolate leaves that increase in length up to 3/4 in. towards top of stem. Flower 3/4 in. long, bright or bronze green, upper sepal and petals forming hood-like galea. Lateral sepals joined at base and erect in front of galea, the upper portions with a deep V-shaped separation, then tapering into erect points embracing the galea. Lip on a short claw, lanceolate, blunt, edges sharply turned down about two-thirds of the way between base and apex, and just above this constriction, the lip bends abruptly forwards: appendages to the lip densely hairy. (Described Journal Proceedings Royal Society W.A., No. 4, 1907.)
W.A.: Bruce Rock, Narrogin, York. July - August

P. recurva, Bentham; bent back.
"Antelope orchid" "Bull orchid"
Stems 1 to 1.5 ft. high, rigid, flowers one to three, without radical rosette of leaves, reddish-green, over an inch long. Lip triangular, ending in a rigid point. This species is easily identified by the conspicuously recurved or bent back points of the lower sepals. Grows usually in low scrub.
W.A.: Albany, Bayswater, Busselton, Dumbleyung,Highbury, Kalamunda, Kendenup, King's Park, Perth, Kojonup, Stirling Range, Swanbourne. August - September.

P. turfosa, Lindley; growing in a damp place.
"Bird orchid"
Stem short, slender, one-flowered, leaves linear, all nearly equal and equally distant along the stem. Flower green, mottled and striped, the edge of galea and lower sepals tinged with red. Galea upright, over 1 in. long, with a long point, and much contracted in the middle, thus forming two openings or doorways to the interior of the flower, the lower ostensibly for the entry of insects, and the upper one for their departure only, entry there being prevented by an arrangement consisting of a barricade formed by the crossing of the upper angles of the column wings, further safeguarded by two hairs that are automatically released from the point of the galea when the flower is ready for fertilisation, and cross each other in front of the opening. This device, however, does not hinder the egress of an insect visitor. Lower part of galea linear, with spreading lobes ending in long points. Lip thread-like, bearded with long lateral hairs, and having a clavate point. This orchid has been confused by many collectors with P. barbata, an Eastern States species. Favours moist, shady spots, chiefly loamy clay.
W.A.: Albany, Gooseberry Hill, Jarnadup, Mahogany Creek, Parkerville, Pindalup, Pinjarra, Woogenellup, York, August - October.

P.rufa, R. Bwown; reddish.
Stem 6 to 10 in. high with several bracts. Leaves in a radical rosette wither before the flowers are out. Flowers, three to four, often more green than red. Galea nearly 1/2 in. long, curved, with a long, fine point in front. Lower part on a rather long basal projection of the column and hanging down from it, the sepals terminating in long fine points, variable in length. Lip on a short claw, obtuse. Column reaching to end of galea.
W.A.: Bencubbin, Boyup Brook, Bruce Rock, Wongan Hills, York. October - November.
All other Australian States.

P. Sargentii, Andrews; honouring O.H. Sargent.
Stem 3 to 5 in. high. Leaves in a radical rosette wither before flowers appear. Stem-leaves or empty bracts lanceolate, stem-clasping. Flowers. 1 or 2. Galea about 1/2 in. long, curved forward. Upper sepal ending in a short upturned point, lateral petals very shortly pointed, their junction with the upper sepal marked by lines of white hairs inside the galea. Lower part 1/2 in. long, pointing downwards, the lobes ending in very short thread-like points. Lip on a broad claw, glabrous, three-lobed, the middle lobe triangular, not 1/4 in. long, with a ridge down the middle; lateral lobes linear-lanceolate, slightly curved, produced at the base into erect thick club-shaped dark brown appendages. Column nearly as long as the galea, with short almost orbicular wings on either side of the rostellum. (Described Journal W.A. Natural History Society May, 1905)
Note by Dr. Andrews: "The labellum and its appendages are quite different from those of any other species and the column wings have no lower lobe. I have not seen the lines of hairs inside the galea in any other species."
W.A.: Bencubbin, Bruce Rock, Dalwallinu, York. JuIy - October.

P.vittata, Lindley; banded.
"Bell orchid" "Cockatoo orchid" "Helmet orchid"
Often a stout leafy plant from 8 in. to over 1 ft. high. Leaves of seedlings heart-shaped in a flat rosette; in the mature plant, lanceolate, acute, stem-clasping. Flowers, three to seven or more, white, banded with green, or heavily marked with reddish-brown and purple. Galea 1/2 in. or more long, broad, helmet-shaped, with a short point in front, directed downwards. Lower part broadly ovate; recurved, with two short acuminate lobes. Lip extremely irritable, on a strap-like claw, short, flat, obtuse, tip emarginate. Column bent almost at right angles, broadly winged in the middle. A common species, favouring all soils and situations, excepting wet ground.
W.A.: Widely distributed