''Praecoxanthus aphyllus'', commonly known as leafless orchid, is the only species of the flowering plant genus ''Praecoxanthus'' in the orchid family, Orchidaceae and is endemic to the south-west of Western Australia. Plants in flower lack a true leaf, although those plants that are not flowering do possess a green leaf. This species is one of the first orchids to flower each year and its creamy white, fragrant flower easily distinguishes it from other species.

Description

''Praecoxanthus aphyllus'' is a terrestrial, perennial, deciduous, sympodial

herb 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 ...

with a few inconspicuous, fine roots and a tuber partly surrounded by a fibrous

sheath Sheath pronounced as , may refer to: * Scabbard, a sheath for holding a sword, knife, or other large blade, as well as guns, such as rifles. * The outer covering of a cable * Condom, a kind of contraception * Debye sheath, a layer of a plasma in ...

. The tuber produces a replacement "dropper" which becomes the daughter tuber in the following year. Non-flowering plants produce a single, stalkless, egg-shaped leaf which is long, wide and glabrous with prominent white veins. The leaf of flowering plants is reduced to a tiny

bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

at the base of the stem. There is a single

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 on the end of a wiry, glabrous stem high. The flower is wide and long. The three sepals and two

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 spreading, creamy-white, free and similar in size and shape to each other. As is usual in orchids, one petal is highly modified as the central labellum. The labellum has three lobes and is purple, green and yellow with two irregular rows of stalked, club-like calli. 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 and are widest at the base. Flowering occurs from March to May and the fruit that follows is a non-fleshy, hairy,

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 seeds.

Taxonomy and naming

Leafless orchid was first formally described in 1837 by George Bentham who gave it the name ''Caladenia aphylla'' and published the description in '' Flora Australiensis''. In 2000,

Stephen Hopper Stephen Donald Hopper AC FLS FTSE (born 18 June 1951) is a Western Australian botanist. He graduated in Biology, specialising in conservation biology and vascular plants. Hopper has written eight books, and has over 200 publications to his n ...

and Andrew Brown described the genus ''Praecoxanthus'' and included this species. The genus name ''"Praecoxanthus"'' is derived from the Latin word ''praecox'' meaning "premature" or "precocious" and the Ancient Greek ''anthos'' meaning "flower". The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

"aphyllus" is derived from the Ancient Greek prefix "a-" meaning "without" and ''phyllon'' meaning "leaf".

Ecology

Leafless orchid flowers are highly fragrant and attract native bees. The yellow calli on a purple labellum resemble pollen-bearing stamens but the flower is nectarless, attracting the insects to an absent reward.

Distribution and habitat

This orchid usually grows in sandy soils in woodland but near Esperance tends to grow in low heath with sub-soil moisture. Unlike some orchids, they do not usually grow in colonies and individuals are well-spaced. It occurs between Pinjarra and Albany and in a coastal strip east to Esperance in the Avon Wheatbelt, Esperance Plains, Jarrah Forest, Mallee,

Swan Coastal Plain The Swan Coastal Plain in Western Australia is the geographic feature which contains the Swan River as it travels west to the Indian Ocean. The coastal plain continues well beyond the boundaries of the Swan River and its tributaries, as a geol ...

and

Warren A warren is a network of wild rodent or lagomorph, typically rabbit burrows. Domestic warrens are artificial, enclosed establishment of animal husbandry dedicated to the raising of rabbits for meat and fur. The term evolved from the medieval Angl ...

biogeographic regions A biogeographic realm or ecozone is the broadest biogeographic division of Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided into bioregions, which are further subdivided into ecoregions. De ...

Conservation

''Praecoxanthus aphyllus'' is classified as "Not Threatened" by the Western Australian Government

Department of Parks and Wildlife The Department of Parks and Wildlife (DPaW) was the department of the Government of Western Australia responsible for managing lands described in the ''Conservation and Land Management Act 1984'' and implementing the state's conservation and e ...

References

External links

* *
C Hookman, ''Praecoxanthus aphyllus'' - Leafless Orchid
{{Taxonbar, from1=Q9062096, from2=Q15515349 Monotypic Orchidoideae genera Diurideae genera Caladeniinae Orchids of Western Australia