''Arthrochilus'', commonly called elbow orchids, is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of about fifteen species of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s from the

orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Eart ...

family (Orchidaceae) and is found in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

and

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

. 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 A pollinium (: pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchid Orchids are plants tha ...

is transferred between insect and flower.

Description

Orchids in the genus ''Arthrochilus'' are terrestrial,

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

sympodial In botany, sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, als ...

herbs Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnish (food), garnishing food, for medicinal purposes, or for fragrances. Culinary use typi ...

usually with a few inconspicuous, fine roots and a single oval-shaped

tuber Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reproduc ...

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

stolon In biology, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...

s. The stem is short, erect and unbranched with thin, leaf-like

cataphyll In plant morphology, a cataphyll (sometimes also called a ''cataphyllum'' or cataphyll leafJackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928) is a reduce ...

s at each

node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics * Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines ...

. There are up to six leaves at or near the base of the plant, sometimes forming a

rosette Rosette is the French diminutive of ''rose''. It may refer to: Flower shaped designs * Rosette (award), a mark awarded by an organisation * Rosette (design), a small flower design *hence, various flower-shaped or rotational symmetric forms: ** R ...

around the stem. The

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

is a

raceme A raceme () or racemoid is an unbranched, indeterminate growth, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are ...

with a few to many non- resupinate, dull-coloured flowers on a wiry stalk. The

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

is similar to or larger than the

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

sepals and its sides curve inwards. The lateral sepals and

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s are attached the base of the

column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member ...

, the petals similar to, but smaller than the sepals. The highly modified labellum is dominated by the

callus A callus (: calluses) is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, b ...

and is hinged to the column by a flexible "claw". The callus is ornamented with feathery

cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...

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

glabrous Glabrousness () is the technical term for a lack of hair, down, setae, trichomes, or other such covering. A glabrous surface may be a natural characteristic of all or part of a plant or animal, or be due to loss because of a physical condition, ...

dehiscent Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part. Structures that op ...

capsule containing a large number of winged seeds.

Taxonomy and naming

The genus ''Arthrochilus'' was first formally described in 1858 by

Ferdinand von Mueller Baron Sir Ferdinand Jacob Heinrich von Mueller, (; 30 June 1825 – 10 October 1896) was a German-Australian physician, geographer, and most notably, a botanist. He was appointed government botanist for the then colony of Victoria, Australia ...

and the description was published in ''

Fragmenta phytographiae Australiae ''Fragmenta phytographiae Australiae'' is a series of papers written by the Victorian Government botanist Ferdinand von Mueller in which he published many of his approximately 2000 descriptions of new taxa of Australian plants. Including the p ...

''. Mueller described '' Arthrochilus irritabilis'' at the same time and it is regarded as the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

. The scientific name of the genus is derived from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

words ''arthron'' meaning "joint" and ''cheilos'' meaning "lip" referring to the jointed labellum.

Distribution and habitat

Elbow orchids are found in all states of Australia except

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

and in southern

Papua New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...

and on the

Torres Strait Islands The Torres Strait Islands are an archipelago of at least 274 small islands in the Torres Strait, a waterway separating far northern continental Australia's Cape York Peninsula and the island of New Guinea. They span an area of , but their tot ...

. The majority of elbow orchid species occur in tropical regions but '' A. huntianus'' grows in eastern Australia with the subspecies ''nothofagicola'' occurring in

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

. The tropical species grow and flower in the summer wet season, usually growing in sand in forest or woodland.

Ecology

The labellum of elbow orchids mimics wingless female thynnid wasps of the Superfamily

Vespoidea Vespoidea is a superfamily of wasps in the order Hymenoptera. Vespoidea includes wasps with a large variety of lifestyles including eusocial, social, and solitary habits, predators, scavengers, parasitoids, and some herbivores. Descriptio ...

Family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Thynnidae The Thynnidae (also known as thynnid wasps, flower wasps, or thynnid flower wasps) are a family of large, solitary wasps whose larvae are almost universally parasitoids of various beetle larvae, especially those in the superfamily Scarabaeoidea. ...

. In its attempt to fly off with the dummy female, the insect is thrust head-first against the column where the hooked wings hold the insect in place long enough for the

pollinia A pollinium (: pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of milkwee ...

to stick to its back. If it is carrying pollinia from another flower, the pollinia are crushed against the stigma. For three species of elbow orchid, a single species of wasp from the genus '' Arthrothynnus'' has been identified. In the case of some tropical species, the wasps struggle so violently with the labellum that the organ is often torn off. Some other orchids similarly employ thynnid wasps as pollinators but only ''Arthrochilus'' flowers have restraining hooks on the labellum.

Species list

The following is a list of species recognised by the ''

Index Kewensis The 1893 ''Index Kewensis'' (IK), maintained by the Royal Botanic Gardens, Kew, is a publication that aims to register all botanical names for seed plants at the rank of species and genera. It later came to include names of taxonomic families and ...

'': *'' Arthrochilus apectus'' D.L.Jones - untidy elbow orchid ( Qld.) *'' Arthrochilus aquilus'' D.L.Jones - dark elbow orchid (Qld.) *'' Arthrochilus byrnesii'' Blaxell - sandstone truffle orchid (N.T., W.A.) *'' Arthrochilus corinnae'' D.L.Jones - swamp elbow orchid (Qld.) *'' Arthrochilus dockrillii'' Lavarack - green truffle orchid (Qld.) *'' Arthrochilus huntianus'' (F.Muell.) Blaxell - common elbow orchid (N.S.W., Tas., Vic., S.A.) *'' Arthrochilus irritabilis'' F.Muell. - clubbed elbow orchid (Qld.) *'' Arthrochilus laevicallus'' Ormerod (Papua New Guinea) *'' Arthrochilus latipes'' D.L.Jones - robust elbow orchid (N.T.) *'' Arthrochilus lavarackianus'' (D.L.Jones) Lavarack - glaucous truffle orchid (Qld.) *'' Arthrochilus oreophilus'' D.L.Jones - montane elbow orchid (Qld.) *'' Arthrochilus prolixus'' D.L.Jones - wispy elbow orchid (N.S.W., Qld.) *'' Arthrochilus rosulatus'' D.L.Jones - rosetted elbow orchid (Qld.) *'' Arthrochilus sabulosus'' D.L.Jones - spotted elbow orchid (Qld.) *'' Arthrochilus stenophyllus'' D.L.Jones - narrow-leaved elbow orchid (Qld.)

References

External links

Australian Native Orchid Society (Queensland), Kabi Group, ''Arthrochilus prolixus''

* ttps://web.archive.org/web/20140521200422/http://www.orchidsonline.com.au/node/2409 Orchids Online, ''Arthrochilus oreophilus'', Synonym: ''Spiculea irritabilis'' sensu Dockr. {{Taxonbar, from=Q249471 Diurideae genera Orchids of Australia Flora of Queensland Orchids of New Guinea