PTEROSTYLIS (Greenhoods)

Other common names are Shell, Snail, Midget, Jug, Cockatoo, Banded, Dwarf. The genus is widespread throughout Australia and most abundant in the southern areas. Their underground vegetative reproduction produces masses of over lapping leaf rosettes, which are mostly immature plants of which about 10%, flower each year. The flowering plants do not produce rosettes but have varying sized and numbers of cauline leaves. The highly successful pollinating strategy produces copious seeds that germinate readily and produce large numbers of plants. Darwin, in his classic work "The Fertilisation of Orchids", stated that Pterostylis had evolved the most amazing and effective reproduction strategy within the world's Orchidaceae. The first research relating to these strategies was undertaken by Cheeseman in 1833 in New Zealand and this was followed by Fitzgerald 1882; Edith Coleman in the Eastern States and Sargent in 1907 in WA. All were able to define the remarkable mechanism of the sensitive labellum that was able to trap visiting insects. The insects enter the galea (pouch) and probe the base of the pouch for a liquid they find irresistible. This activates the sensitive labellum, which with the assistance of the column and the column wings forces, the insect backwards and traps it in a confined space. The margins of the column are coated in coarse hairs and notches ensuring that the only way out is upwards. The column wings channel the insect to the sticky stigma and the two pollen sacks. A daub of this sticky glue fastens the pollinia to the insect and they are then transported to the next flower. The insect attracting agent is a sublime secretion at the base of the pouch and some researchers have postulated that the insects receive a drink/food with possible sexual attractions. The galea encloses the winged column and sensitive labellum where the dorsal sepals and petals and the lateral sepals unite to form the pouch. The labellum, broadly elliptical, has hairs and indentations along both sides giving footholds to enable the insect to escape upwards. It is held forward below the sinus (the union of the lateral sepals) by an elastic claw at the base. Insects entering trigger off the sensitive labellum that forces the visitor to a confined space where the only escape is upwards so that the pollinating process described earlier is effected. If pollination has not been effected then the labellum retracts ready to repeat the process. This takes from 20 minutes to some hours depending on the ambient temperature. The precise explanation of just how the elastic claw performs its purpose is still subject to scientific research. However the mechanism seems to be highly efficient as almost all flowers produce seed capsules.

Bird orchids. This distinctive group is present in most of the lower southwest with only a few outside this area. The actual number of species is not known but this should be rectified when the current revision is published. The species name' barbata' refers to the hairy bearded labellum that is characteristic. The labellum is thin, wiry and has mostly coarse irregular hairs that serve to close off the orifice containing the stigma and pollinias. The same sensitive elastic hinge, as for the entire genus, is employed.

PYRORCHIS (Beak orchids)

The genus includes 2 species previously classified as Lyperanthus (Hoffman and Brown, 1998). Both species have a fleshy, oval leaf, live in colonies and flower following hot summer bushfires. Pyrorchis nigricans also occurs in South Australia, Victoria, New South Wales and Tasmania.

RHIZANTHELLA (Underground orchids)

In 1928, Farmer John Trott of Corrigin, unearthed the first specimens of Rhizenthella gardneri when ploughing new land that had been previously rolled and burnt. He took the specimen to Charles Gardner, the Government Botanist, who, in turn, forwarded them onto Dr. Sanders Rodgers who named the species in Gardners honour. As the common name implies, the species spends most of its life cycle underground, growing in association with, and close to Melaleuca uncinata, that sheds its leaves to produce thick layers of leaf mould. The developing capitulum of tiny, crowded orchids, are exposed when the floral bracts expand and, occasionally push through the leaf mould, allowing light, and presumably pollinators to enter. Since the first finds, just six confirmed sightings were made in Corrigin - Babakin areas. A breakthrough occurred in 1979 when farmer John McGuiness of Munglinup, East of Ravensthorpe, turned over a Malley root and found an orchid under it. Research then and again in 1980 produced a total of 26 specimens. Further collections were made at the Oldfield locations, with another 9 plants sighted . Finance was made available for research from the World Wildlife Fund, resulting in a well organized research program led by Kings Park research scientists and assisted by the members of the Western Australian Native Orchid Study Group. Around 150 sightings were made and as a result of this and ongoing research, the knowledge of the biology of Rhizanthella gardneri has been greatly advanced. Rhizanthella gardneri are unusual in other ways amongst the orchid family. The flowers are produced in a capitulum, which appears to be one large flower but on closer examination, proves to be a whole group of small flowers grouped together within a series of bracts which gives the appearance of being a single flower.

Ron Heberle

SPICULAEA� (Elbow orchid)

Spiculaea (spiked column wings) ciliata (soft hairs on the labellum).This remarkable orchid is the product of a much harsher environment than that of the present. It has adapted to survive, flower and reproduce in the summer months (November to January) when all surface moisture is absent. It is widely distributed inland to the goldfields and west to the Darling Scarp where it grows in thin layers of moss and soil on and around granite sheets of rock.To withstand the environmental hazards, the leaf and stem dry off from the base upward to force the sap up the succulent stem enabling the buds to open in turn. This survival trait is demonstrated well when a plant can be plucked, placed in a letter and sent by post without any protection half way across the world to the USA or to Europe, and when received the buds will continue to open. The pollinating strategy is similar to that of the Drakaea where the insect imitating labellum is attached to a wiry stem hinged in the centre. Although not sensitive it can only move in the direction of the column (as with Drakaea) and achieves pollination via pseudo-copulation. The male wasps, attempting to carry off the sham female, are carried forward and guided by the spiked column wings either to transfer pollen to the stigma or to be daubed with pollen to be carried to another plant. A� truly remarkable orchid. Ron Heberle April 2003

THELYMITRA (Sun orchids)

Thelymitra's are a terrestrial orchid genus found in Australia, (50 odd species) New Zealand, (about a dozen species) New Caledonia, (2) and the odd one in Timor, Java, and The Philippines.

The Thelymitra's on the following pages, all come from the south west of Western Australia, specifically, the area around Albany, which is known for it's unusual flora. Thelymitra's are known as 'Sun Orchids' because of their tendency to only open on sunny days, closing at night and during cold and cloudy weather.
Unlike most orchids, the lip, or what passes for a lip, is usually the same shape as the petals. There are, however, a few species in which the lip tends to be modified slightly, and appears to be shaped like a 'normal' orchid lip.�
One of the most outstanding features of Thelymitra's, is the huge colour range, which can include white, yellow, pink, red, orange, blue, purple and all sorts of combinations of the above, which can produce orchids that are quite stunning, as Ron Heberle's photographs will show. The blue Thelymitra's can be quite unbelievable when one comes across them in the bush, as true blue orchids are so rare in nature. The number of flowers carried on Thelymitra's, varies between one and 20 to 25, sometimes more. Flower size is between 1 - 6cm.

Ron Heberle