''Pterostylis angusta'', commonly known as the narrow shell orchid, is a species of orchid endemic to the

south-west The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each se ...

of Western Australia. As with similar greenhoods, the flowering plants differ from those which are not flowering. The non-flowering plants have a rosette of leaves flat on the ground but the flowering plants have a single flower with leaves on the flowering spike. In this species the flower is green, white and brown with an inflated base, a narrow hood and the longest labellum of any Western Australian ''Pterostylis'' species.

Description

''Pterostylis angusta'' is a terrestrial, perennial, deciduous,

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 an underground tuber and when not flowering, a rosette of dark bluish-green leaves lying flat on the ground. Each leaf is long and wide. Flowering plants usually only have a single flower long and wide which leans slightly forwards on a flowering stem high with between three and seven stem leaves. The flowers are green and white, brownish near the tip. The dorsal sepal 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 fused, forming a hood or "galea" over 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 base of the galea is inflated and the top is narrow with a sharply-pointed end. The lateral sepals are held closely against the galea and have narrow tips long and a V-shaped sinus between their bases. The labellum is long, about wide and curved, and protrudes above the sinus. Flowering occurs from late May to July.

Taxonomy and naming

''Pterostylis angusta'' was first formally described in 1971 by

Alex George Alexander or Alex George may refer to: *Alex George (botanist) (born 1939), Australian botanist * Alexander L. George (1920–2006), American political scientist * Alexander George (philosopher), American philosopher *Alex George (motorcyclist), Sc ...

from a specimen collected near Mount Trio in the

Stirling Range The Stirling Range or Koikyennuruff is a range of mountains and hills in the Great Southern region of Western Australia, south-east of Perth. It is over wide from west to east, stretching from the highway between Mount Barker and Cranb ...

and the description was published in '' Nuytsia''. 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 ...

(''angusta'') is a Latin word meaning "narrow", referring to the narrow galea.

Distribution and habitat

The narrow shell orchid grows in two disjunct areas in the Jarrah Forest

biogeographic region An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of l ...

, one between Brookton and the Stirling Range and the other between Australind and

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. It mostly grows in woodland, often in sandy soil.

Conservation

''Pterostylis angusta'' is listed as "not threatened" by the

Government of Western Australia The Government of Western Australia, formally referred to as His Majesty's Government of Western Australia, is the Australian state democratic administrative authority of Western Australia. It is also commonly referred to as the WA Government o ...

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

{{Taxonbar, from=Q15491172 angusta Endemic orchids of Australia Orchids of Western Australia Plants described in 1971