''Pterostylis tenuissima'', commonly known as the swamp greenhood, is a species of

orchid 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 ...

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 ...

to the southern mainland of

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 small translucent white flowers with dark green stripes and markings and both 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 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 ...

and

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 ...

sepals have relatively long, thread-like tips.

Description

''Pterostylis tenuissima'' 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 Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...

and when not flowering, a rosette of egg-shaped leaves lying close to the ground, each leaf long and wide. Flowering plants have a single flower long and wide borne on a flowering stem mm high with between three and seven stem leaves. The flowers are translucent white with dark green stripes and markings. The

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 curves forward and downward with a thread-like tip long. The

sepals are held closely against the galea with erect, thread-like tips long. The

sinus Sinus may refer to: Anatomy * Sinus (anatomy), a sac or cavity in any organ or tissue ** Paranasal sinuses, air cavities in the cranial bones, especially those near the nose, including: *** Maxillary sinus, is the largest of the paranasal sinuses, ...

between the lateral sepals bulges forward and has a V-shaped notch in the centre. The labellum is long, about wide, dark brown, slightly curved and protrudes above the sinus. Flowering occurs from October to February.

Taxonomy and naming

''Pterostylis tenuissima'' was first formally described in 1950 by William Nicholls from a specimen collected near

Nelson Nelson may refer to: Arts and entertainment * ''Nelson'' (1918 film), a historical film directed by Maurice Elvey * ''Nelson'' (1926 film), a historical film directed by Walter Summers * ''Nelson'' (opera), an opera by Lennox Berkeley to a lib ...

and the description was published in ''

The Victorian Naturalist ''The Victorian Naturalist'' is a bimonthly scientific journal covering natural history, especially of Australia. It is published by the Field Naturalists Club of Victoria and is received as part of the membership subscription of that club. From ...

''. 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 ...

(''tenuissima'') is the

superlative Comparison is a feature in the morphology or syntax of some languages whereby adjectives and adverbs are inflected to indicate the relative degree of the property they define exhibited by the word or phrase they modify or describe. In languages t ...

form of the

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 ''tenuis'' meaning "thin", hence "thinnest".

Distribution and habitat

The swamp greenhood occurs in the far south-eastern corner of

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

and south-western

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

with a

disjunct population In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a s ...

Wilsons Promontory Wilsons Promontory, is a peninsula that forms the southernmost part of the Australian mainland, located in the state of Victoria. South Point at is the southernmost tip of Wilsons Promontory and hence of mainland Australia. Located at nearb ...

. It grows in swampy mud under dense thickets of woolly tea-tree (''

Leptospermum lanigerum ''Leptospermum lanigerum'', commonly known as the woolly teatree, is a small tree or medium shrub from the plant family ''Myrtaceae''. Its common name derives from the conspicuously hairy capsules produced as fruit, along with the fine, silky hai ...

'') and scented paperbark (''

Melaleuca squarrosa ''Melaleuca squarrosa'', commonly known as scented paperbark, is a plant in the myrtle family, Myrtaceae and is endemic to south eastern parts of Australia, especially Tasmania. It is an attractive shrub with dense foliage and arching branches an ...

''), sometimes forming large colonies.

Conservation

''Pterostylis tenuissima'' is listed as "vulnerable" under the Australian Government ''

Environment Protection and Biodiversity Conservation Act 1999 The ''Environment Protection and Biodiversity Conservation Act 1999'' (Cth) is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and cultu ...

'' and the Victorian Government ''

Flora and Fauna Guarantee Act 1988 The ''Flora and Fauna Guarantee Act 1988'', also known as the ''FFG Act'', is an act of the Victorian Government designed to protect species, genetic material and habitats, to prevent extinction and allow maximum genetic diversity within the Au ...

''. Threats to the species include land clearing, grazing by livestock, draining of wetland and weed invasion.

References

{{Taxonbar, from=Q15493412 tenuissima Endemic orchids of Australia Orchids of South Australia Orchids of Victoria (Australia) Plants described in 1950