''Pterostylis petrosa'', commonly known as the Riverina rustyhood, is a plant in the orchid family

Orchidaceae 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. Along with the Asteraceae, they are one of the two largest families of flowering ...

and is

endemic Endemism is the state of a species being found 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 found elsew ...

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

. It has a rosette of leaves at its base and up to eight dark brown flowers with transparent "windows", long spreading tips on the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral cons ...

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 The term ''sepalum'' was coined b ...

s and a thin, brown, insect-like labellum.

Description

''Pterostylis petrosa'', is a terrestrial,

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

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 leaves, usually in the autumn; to the shedding of petals, aft ...

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. It has a rosette of between six and ten egg-shaped leaves at the base of the flowering spike, each leaf long and wide. The leaves are often withered by the time of flowering. Up to eight dark brown flowers with translucent panels and long, wide are borne on a flowering spike tall. Each flower is carried on the end of a thin stalk long. There are between two and four stem leaves with their bases wrapped around the flowering spike. 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 * Dorsal co ...

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 joined to form a hood called the "galea" over the column with the dorsal sepal having a thread-like tip long. The lateral sepals are turned downwards and are wider than the galea. They are shallowly dished, hairy on their outer edges and suddenly taper to a thread-like tip, . The labellum is brown, thin and insect-like, long and about wide with two long hairs on the "head" end and nine to twelve shorter hairs on each side of the "body". Flowering occurs from September to November.

Taxonomy and naming

''Pterostylis petrosa'' was first formally described in 1983 by David Jones and Mark Clements from a specimen collected near The Rock and the description was published in '' Muelleria''. 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 ...

(''petrosa'') is a

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

word meaning "rocky" or "stony", referring to the habitat where this orchid grows, and to the type location.

Distribution and habitat

The Riverina rustyhood occurs in the

Riverina The Riverina is an agricultural region of south-western New South Wales, Australia. The Riverina is distinguished from other Australian regions by the combination of flat plains, warm to hot climate and an ample supply of water for irrigation ...

area where it grows on a few stony hills in rock crevices and on ledges.

References

{{Taxonbar, from=Q15492391

petrosa PetroSA (The Petroleum, Oil and Gas Corporation of South Africa ( SOC) Ltd.) is the national oil company (NOC) of South Africa. Its main activities are the extraction of natural gas from offshore fields about 89 km from Mossel Bay, the produ ...

Endemic orchids of Australia Orchids of New South Wales Plants described in 1983