''Pterostylis williamsonii'', commonly known as the brown-lip leafy greenhood, is a plant in the orchid family Orchidaceae and is endemic to Tasmania. Flowering plants have up to seven transparent green flowers with darker green and brown bands and a hairy, insect-like labellum with a blackish stripe. Non-flowering plants have a rosette of leaves on a short stalk but flowering plants lack the rosette, instead having five to seven stem leaves.

Description

''Pterostylis williamsonii'', 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. Non-flowering plants have a rosette of between four and six dark green, egg-shaped leaves on a stalk long, each leaf long and wide. Flowering plants have up to nine transparent green flowers with darker green and brown bands on a flowering spike high. The flowering spike has five or six lance-shaped stem leaves which are long and wide. The flowers are long, wide. 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. ...

with the dorsal sepal having a brown tip. The lateral sepals turn downwards, are long, wide and have a narrow tip about long which is orange-brown on its end. The labellum is insect-like, long, about wide and creamy yellow to dark chocolate brown with a black central stripe. Flowering occurs from April to July.

Taxonomy and naming

''Pterostylis williamsonii'' was first formally described in 1998 by David Jones and the description was published in ''Australian Orchid Research'' from a specimen collected by Ron and Kath Williamson at Coles Bay. 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 ...

(''williamsonii'') honours Ronald Herbert Williamson (1931-2003), who collected the type specimen.

Distribution and habitat

The brown-lip leafy greenhood is widespread in Tasmania where it grows in forest near low shrubs and bracken.

References

{{Taxonbar, from=Q15492484 williamsonii Endemic orchids of Australia Orchids of Tasmania Plants described in 1998