''Pterostylis laxa'', commonly known as the antelope greenhood, is a species of orchid endemic to south-eastern

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 ...

. 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. This greenhood has green and white flowers with darker green or brown markings and a dorsal sepal with a long thread-like tip.

Description

''Pterostylis laxa'' 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 12 to 25 bright green, egg-shaped leaves lying flat on the ground, each leaf long and wide. Flowering plants have a single flower long and wide which leans slightly forwards on a flowering stem high with between three and five stem leaves. The flowers are green and white with darker green or brown markings. 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 dorsal sepal has a thread-like tip long. The lateral sepals are erect or backswept, held closely against the galea, have thread-like tips long and a flat sinus with a central notch between their bases. The labellum is long, wide, dark-coloured, curved, pointed and visible above the sinus. Flowering occurs from January to April.

Taxonomy and naming

''Pterostylis laxa'' was first formally described in 1968 by

John Blackmore John Blackmore was an English politician who sat in the House of Commons in 1654. Blackmore was the son of John Blackmore of Exeter, Devon. He matriculated at Exeter College, Oxford on 12 December 1634, aged 18. He was awarded BA on 16 January ...

from a specimen collected in the Upper

Grose Valley The Grose Valley is a rugged valley in the Blue Mountains, New South Wales, Australia. It has been formed by the Grose River, the headwaters of which are in the Mount Victoria area. The valley is located between the Great Western Highway and ...

. The description was published in ''The Orchadian''. 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 ...

(''laxa'') is a Latin word meaning "loose" or "slack".

Distribution and habitat

The antelope greenhood grows among grasses on slopes in forest in north-eastern Victoria and in eastern New South Wales as far north as the Northern Tablelands.

References

{{Taxonbar, from=Q15491872 laxa Endemic orchids of Australia Orchids of New South Wales Orchids of the Australian Capital Territory Orchids of Victoria (Australia) Plants described in 1968