''Caladenia'', commonly known as spider orchids, is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of 350

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

s in the orchid

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

Orchidaceae 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 ...

. Spider orchids are

terrestrial Terrestrial refers to things related to land or the planet Earth. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...

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 medicina ...

with a single hairy leaf and a hairy stem. The labellum is fringed or toothed in most species and there are small projections called calli on the labellum. The flowers have adaptations to attract particular species of insects for

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...

. The genus is divided into three groups on the basis of flower shape, broadly, spider orchids, zebra orchids and cowslip orchids, although other common names are often used. Although they occur in other countries, most are Australian and 136 species occur in

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 ...

, making it the most species-rich orchid genus in that state.

Description

Orchids in the genus ''Caladenia'' 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, a ...

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 with a few inconspicuous, fine roots and a

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 growin ...

partly surrounded by a fibrous sheath. The tuber produces two "droppers" which become daughter tubers in the following year. There is a single hairy convolute leaf at the base of the plant. Most species have an enlarged cell at the base of each hair. The leaf may be medium-sized to large, fleshy or leathery, lance-shaped to oblong, but is always

simple Simple or SIMPLE may refer to: * Simplicity, the state or quality of being simple Arts and entertainment * ''Simple'' (album), by Andy Yorke, 2008, and its title track * "Simple" (Florida Georgia Line song), 2018 * "Simple", a song by John ...

, lacking lobes and serrations. 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 ...

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 sh ...

with from one to eight

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 " ...

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

s. The three

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 ...

s and two

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

s are free and similar in size and shape to each other. In some species, the sepals or petals or both have narrow tips with club-like ends. As is usual in orchids, one petal is highly modified as the central labellum. The labellum is divided into three parts, each of which usually has a fringed or dentate margin, while the central lobe has stalked or button-like calli which are often in rows. The sexual parts of the flower are fused to 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 ...

, which has wing-like structures on its sides. Most species flower in early spring but some species, such as the winter spider orchid ('' C. drummondii'') flower in other months. The fruit that follows flowering is a non-fleshy,

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 o ...

capsule containing up to 500 seeds. Kwinana gnangarra 300815-102

Taxonomy and naming

The first specimens of the genus were collected by Joseph Banks in Sydney in 1777 and by

Archibald Menzies Archibald Menzies ( ; 15 March 1754 – 15 February 1842) was a Scottish surgeon, botanist and naturalist. He spent many years at sea, serving with the Royal Navy, private merchants, and the Vancouver Expedition. He was the first recorded Euro ...

King George Sound King George Sound ( nys , Menang Koort) is a sound on the south coast of Western Australia. Named King George the Third's Sound in 1791, it was referred to as King George's Sound from 1805. The name "King George Sound" gradually came into use ...

in Western Australia in 1784. James Edward Smith formally described ''Arethusa catenata'', now known as ''

Caladenia catenata ''Caladenia catenata'', commonly known as white caladenia, white fingers and lady's fingers, is a plant in the orchid family Orchidaceae and is endemic to New South Wales, Queensland and Victoria. It is a ground orchid with a single hairy leaf ...

'' in 1805, from specimens collected in Sydney. The genus was first formally described by Robert Brown in 1810 in ''

Prodromus Florae Novae Hollandiae ''Prodromus Florae Novae Hollandiae et Insulae Van Diemen'' (Prodromus of the Flora of New Holland and Van Diemen's Land) is a flora of Australia written by botanist Robert Brown and published in 1810. Often referred to as ''Prodromus Flora Nova ...

''. At the same time he described 15 species of ''Caladenia'' but did not nominate a

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( ...

. Brown collected the specimens as a member of

Matthew Flinders Captain (Royal Navy), Captain Matthew Flinders (16 March 1774 – 19 July 1814) was a British navigator and cartographer who led the first littoral zone, inshore circumnavigate, circumnavigation of mainland Australia, then called New Holland ...

' mapping and exploration voyage that circumnavigated Australia. He spent just over three years on botanical research with assistants in Australia. The genus name (''Caladenia'') 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 p ...

words ''kalos'' meaning "beautiful" and ''aden'' meaning "a gland" referring to the colourful labellum. There has been disagreement between taxonomists as to which orchids belong in the genus ''Caladenia'' and which do not, and about classification within the genus. Recent studies of the

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

of the group suggest that

John Lindley John Lindley FRS (5 February 1799 – 1 November 1865) was an English botanist, gardener and orchidologist. Early years Born in Catton, near Norwich, England, John Lindley was one of four children of George and Mary Lindley. George Lindley ...

’s 1840 description of ''Caladenia'' (in ''The Genera and Species of Orchidaceous Plants''), but including '' Glossodia'' and '' Elythranthera'', as being the most accurate reflection of the subtribe ''

Caladeniinae Caladeniinae is an orchid subtribe in the tribe Diurideae. See also * Taxonomy of the Orchidaceae The taxonomy of the Orchidaceae (orchid family) has evolved slowly during the last 250 years, starting with Carl Linnaeus who in 1753 recognized ...

''. Those orchids previously included in the genera ''Glossodia'', ''Elythranthera'' and ''Cyanicula'' have been transferred to ''Caladenia''. Caladenia orchids are informally grouped into those with long narrow sepals and petals, such as the white spider orchid ('' C. longicauda'') and the clubbed spider orchid ('' C. longiclavata''), those with short sepals and petals which tend to hang near the stem, such as the zebra orchid ('' C. cairnsiana'') and dwarf zebra orchid ('' C. pachychila'') and a third group with short, spreading sepals and petals such as the cowslip orchid ( ''C. flava'') and fan orchid ( ''C. nana'').

Distribution and habitat

Most caladenias are

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

to Australia. Eleven species, ten of which are endemic, occur in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...

with one also occurring in Australia. ''

'' and '' C. carnea'' occur in New Caledonia, with the latter also found in

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

. There are about 136 species endemic to the south-west of Western Australia, 114 of which have been formally described and a further 18 hybrids which have been described and named. In Western Australia, caladenias are found in the south-west from north of Kalbarri on the west coast to the

Nuytsland Nature Reserve Nuytsland Nature Reserve is a protected area of Western Australia in the south-eastern part of the state, on the south coast. Geography Nominally located at 32° 18' S 125° 52' E, it has an area of 6,253.44 km², and takes in over 500&nb ...

on the coast of the

Great Australian Bight The Great Australian Bight is a large oceanic bight, or open bay, off the central and western portions of the southern coastline of mainland Australia. Extent Two definitions of the extent are in use – one used by the International Hydro ...

. Their habitats range from cool, moist

Karri ''Eucalyptus diversicolor'', commonly known as karri, is a species of flowering plant in the family Myrtaceae and is endemic to the south-west of Western Australia. It is a tall tree with smooth light grey to cream-coloured, often mottled bar ...

forest, to swamplands near the coast and to almost arid mallee

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

Ecology

Orchids in the genus ''Caladenia'' are pollinated by insects, usually bees or wasps. Some species appear to attract male wasps by having the scent, shape and colouration of flightless female wasps. For example, '' C. lobata'' attracts male '' Thynnoides bidens'' wasps. As the wasps lands on the flower, the labellum is pulled down by the insect's weight. As it moves up the labellum, that organ tips the insect against the column where the wasp contacts the sexual parts and either picks up or deposits

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 mi ...

. Many such orchids are only attractive to one species of insect. Sometimes hybrids between female-mimicking and food-attracting species occur as in the case of '' C. patersonii'' which has the odour of fermentation. ''C. patersonii'' attracts several insect species, and forms hybrids with insect-mimicking species including '' C. lobata'' and '' C. dilatata''. In some caladenias, the sepal and petals (apart from the labellum) are narrow with expanded tips called "clubs". These are thought to be the source of sexual attractants for those species that mimic female wasps. Most such species do not have a scent detectable by humans but are attractive to male Thynnid wasps. For some species, such as '' C. multiclavia'', it is the labellum that mimics the size, shape and presumably the scent of females.

Use in horticulture

''Caladenia'' have generally proven difficult to maintain and cultivate artificially. Some enthusiasts have had limited success by cultivating the symbiotic fungus that the orchid requires and by careful use of fertiliser to keep the fungus and orchid in balance. The 1889 book 'The Useful Native Plants of Australia' records that "These and other orchids have edible tubers."

Gallery

Image:Caladenia Crebra.jpg, Arrowsmith spider orchid ('' C. crebra'') Image:Kwinana gnangarra 300815-105.jpg, Clubbed spider orchid ('' C. longicauda'') budding Image:Caladenia chlorostyla LC277.jpg, White fingers ('' C. chlorostyla''), from

Image:Caladenia.PlateI.jpg, Several Caladenia species from Pelloe's ''West Australia Orchids'' Image:Caladenia atrovespa (5090971253).jpg, '' C. atrovespa'' growing near Canberra Image:Kwinana gnangarra 300815-100.jpg, Dancing spider ('' C. discoidea'') growing near

Perth Perth is the list of Australian capital cities, capital and largest city of the Australian states and territories of Australia, state of Western Australia. It is the list of cities in Australia by population, fourth most populous city in Aust ...

Image:Caladenia lobata.JPG, Butterfly orchid ('' C. lobata'') near Mount Barker Image:Caladenia venusta.JPG, Large white spider orchid ('' C. venusta'')

References

* New species in ''Orchid Research Newsletter'' No. 47 (January 2006) (Royal Botanical Gardens, Kew)

External links

*
Gallery of images
- Orchid Society of Western Australia {{Taxonbar, from=Q2720020 Diurideae genera Orchids of Australia Taxa named by Robert Brown (botanist, born 1773)