''Pterostylis micromega'', commonly known as the swamp greenhood, is a species of greenhood orchid endemic to New Zealand. Both flowering and non-flowering plants have a rosette of leaves while flowering plants also have a single, relatively large whitish flower with a pointed dorsal sepal. The flower colour and pointed dorsal sepal are unique in New Zealand ''Pterostylis''.

Description

''Pterostylis micromega'' 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 which often grows in loose colonies. Non-flowering plants have a rosette of broad elliptic leaves, each leaf long with a petiole a further wide. Flowering plants have a similar rosette at the base of a flowering stem tall with egg-shaped stem leaves wrapped around it, the highest leaf about as tall as the flower. There is a single, mostly whitish flower with a pale green tinge. 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 is long and curves forward with a tapering tip. The lateral sepals are erect, have narrow tips which are higher than the galea and there is a wide gap between them and the galea. The labellum is curved, reddish-brown and protrudes above the sinus between the lateral sepals. Flowering occurs between November and February.

Taxonomy and naming

''Pterostylis micromega'' was first formally described in 1853 by Joseph Dalton Hooker and the description was published in '' Flora Novae-Zelandiae''. 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 ...

(''micromega'') is derived from the Ancient Greek words ''mikros'' meaning "small" or "little" and ''mega'' meaning "large".

Distribution and habitat

The swamp greenhood grows in swampy areas sometimes in colonies of up to fifty. It has been recorded on the North,

South South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...

and Chatham Islands but its distribution is now much reduced. It has not been observed on Chatham Island since the 1800s but is still present near Waikato, on the Volcanic Plateau, near Wanganui and in the Wairarapa.

Conservation status

''Pterostylis micromega'' is classed as "data poor", "extreme fluctuations" and "range restricted" under the ''New Zealand Threat Classification System''.

References

{{Taxonbar, from=Q15492623 micromega Orchids of New Zealand Plants described in 1853