''Genoplesium sigmoideum'', commonly known as the Dave's Creek midge orchid, is a species of small terrestrial

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 ...

that is

endemic Endemism is the state of a species being found only 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 foun ...

to a small area in the

Lamington National Park The Lamington National Park is a national park in the McPherson Range on the Queensland/New South Wales border in Australia. From Southport, Queensland, Southport on the Gold Coast, Australia, Gold Coast the park is to the southwest and Brisbane ...

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

. It has a single thin leaf fused to the flowering stem and up to twenty dark red flowers with a hairy labellum. The species is treated as ''Corunastylis sigmoidea'' in Queensland.

Description

''Genoplesium sigmoideum'' is a 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 ...

herb Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Culinary use typically distingu ...

with an underground

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 ...

and a single thin leaf with a reddish base and long, fused to the flowering stem with the free part long. Between five and twenty flowers are crowded along a flowering stem long, reaching to a height . The flowers lean downwards, are dark red and about wide. The flowers are inverted so that the labellum is above 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 ...

rather than below it. 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 egg-shaped, about long and wide and

concave Concave or concavity may refer to: Science and technology * Concave lens * Concave mirror Mathematics * Concave function, the negative of a convex function * Concave polygon A simple polygon that is not convex is called concave, non-convex or ...

. 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 are linear to lance-shaped, about long, wide and spread widely apart with a whitish

gland A gland is a Cell (biology), cell or an Organ (biology), organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also funct ...

on the tip. The

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 linear to egg-shaped, about long and wide with a prominent S-shaped gland on the tip. The labellum is elliptic to egg-shaped with the narrower end towards the base, about long, wide with its edges densely covered with short hairs. There is a thick, tapering, dark purplish-red

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 ...

in the centre of the labellum and extending almost to its tip. Flowering occurs in December and January.

Taxonomy and naming

''Genoplesium sigmoideum'' was first formally described in 1991 by David Jones and the description was published in ''Australian Orchid Research''. In 2002, David Jones and Mark Clements changed the name to ''Corunastylis sigmoidea'', the name the species is known by in Queensland, but the latter name is not accepted by the

Australian Plant Census The Australian Plant Census (APC) provides an online interface to currently accepted, published, scientific names of the vascular flora of Australia, as one of the output interfaces of the national government Integrated Biodiversity Information Sys ...

. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

(''sigmoideum'') refers to the S-shaped gland on the petals.

Distribution and habitat

''Genoplesium sigmoideum'' grows with low shrubs in shallow soil on rock ledges near Dave's Creek in the Lamington National Park.

References

{{Taxonbar, from=Q15462814 sigmoideum Endemic orchids of Australia Orchids of Queensland Plants described in 1991