Elbow orchids | |
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Arthrochilus latipes in Kakadu National Park | |
Scientific classification | |
Kingdom: | Plantae |
(unranked): | Angiosperms |
(unranked): | Monocots |
Order: | Asparagales |
Family: | Orchidaceae |
Subfamily: | Orchidoideae |
Tribe: | Diurideae |
Subtribe: | Drakaeinae |
Genus: |
Arthrochilus F.Muell. |
Type species | |
Arthrochilus irritabilis F.Muell. |
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Synonyms | |
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Arthrochilus, commonly called elbow orchids, is a genus of about fifteen species of flowering plants from the orchid family (Orchidaceae) and is found in Australia and New Guinea. The flowers are pollinated by male thynnid wasps which attempt to mate with the flower and are held in place by hooks while the pollinium is transferred between insect and flower.
Orchids in the genus Arthrochilus are terrestrial, perennial, deciduous, sympodial herbs usually with a few inconspicuous, fine roots and a single oval-shaped tuber lacking a protective fibrous sheath. (A. huntianus lacks a true tuber.) Some species form colonies, reproducing asexually from daughter tubers formed on the end of root-like stolons. The stem is short, erect and unbranched with thin, leaf-like cataphylls at each node. There are up to six leaves at or near the base of the plant, sometimes forming a rosette around the stem.
The inflorescence is a raceme with a few to many non-resupinate, dull-coloured flowers on a wiry stalk. The sepal is similar to or larger than the sepals and its sides curve inwards. The lateral sepals and petals are attached the base of the column, the petals similar to, but smaller than the sepals. The highly modified labellum is dominated by the callus and is hinged to the column by a flexible "claw". The callus is ornamented with feathery cilia and club-shaped structures which gives the labellum the form of a wingless, female wasp. The column has two pairs of wings, two which surround the sexual parts of the flower and two larger hook-like wings either side of the column. Elbow orchids mainly flower in summer and the fruit that follows flowering is a dehiscent capsule containing a large number of winged seeds.