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

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of about fifteen species of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

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. Along with the Asteraceae, they are one of the two largest families of flowering ...

family (Orchidaceae) and is found in

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

and

New Guinea New Guinea (; Hiri Motu Hiri Motu, also known as Police Motu, Pidgin Motu, or just Hiri, is a language of Papua New Guinea, which is spoken in surrounding areas of Port Moresby (Capital of Papua New Guinea). It is a simplified version of ...

. 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 (plural 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 mil ...

is transferred between insect and flower.

Description

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

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

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 leaves, usually in the autumn; to the shedding of petals, aft ...

sympodial 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, also referred to a ...

herbs In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...

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

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...

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, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

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 around the stem. Arthrochilus (correct labels)

The

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

is a

raceme A raceme ( or ) or racemoid is an unbranched, 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 produced as the s ...

with a few to many non-

resupinate Resupination is derived from the Latin word ''resupinus'', meaning "bent back with the face upward" or "on the back". "Resupination" is the noun form of the adjective "resupine" which means "being upside-down, supine or facing upward". The word " ...

, 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 * Dorsal c ...

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 The term ''sepalum'' was coined b ...

is similar to or larger than the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral cons ...

sepals and its sides curve inwards. The lateral sepals and

petal Petals are modified Leaf, leaves that surround the reproductive parts of flowers. They are often advertising coloration, brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''c ...

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 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, but they may o ...

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

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

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 (from the Latin '' glaber'' meaning "bald", "hairless", "shaved", "smooth") 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 ...

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, (german: Müller; 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 Vict ...

and the description was published in '' Fragmenta phytographiae Australiae''. Mueller described '' Arthrochilus irritabilis'' at the same time and it is regarded as the

type species In 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 species that contains the biological type specimen ...

. 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 ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

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 (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

and in southern

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

and on the

Torres Strait Islands The Torres Strait Islands are a group 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 total land ...

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

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

. 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 SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

Vespoidea Vespoidea is a superfamily of wasps in the order Hymenoptera, although older taxonomic schemes may vary in this categorization, particularly in whether to recognize the superfamilies Scolioidea (for scoliid wasps) or Formicoidea (for ants). V ...

Family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Thynnidae The Thynnidae (also known as thynnid wasps or 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. Until recently, the co ...

. 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 (plural 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 mil ...

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 ''Arthrochilus huntianus'', commonly known as common elbow orchid, is a flowering plant in the orchid family (Orchidaceae) and is endemic to south-eastern Australia. It has no leaves but an insect-like flower which has its labellum dangling like ...

'' (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 ''Arthrochilus latipes'', commonly known as robust elbow orchid, is a flowering plant in the orchid family (Orchidaceae) and is endemic to the "Top End" of the Northern Territory in Australia. Each plant has from two to four ground-hugging leaves ...

'' 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

* Berg Pana, H. 2005. ''Handbuch der Orchideen-Namen. Dictionary of Orchid Names. Dizionario dei nomi delle orchidee''. Ulmer, Stuttgart

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