Pterostylis revoluta

Pterostylis revoluta, commonly known as the autumn greenhood, is a species of orchid endemic to south-eastern Australia. 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 white and green flowers which have a long, curved, pointed labellum which extends beyond the sinus between the lateral sepals.

Autumn greenhood
Pterostylis revoluta growing in the Aranda bushland reserve
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Cranichideae
Genus: Pterostylis
Species:
P. revoluta
Binomial name
Pterostylis revoluta
Synonyms[1]

Diplodium revolutum (R.Br.) D.L.Jones & M.A.Clem.

Description

Pterostylis revoluta is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette of between three and seven greyish to bluish, egg-shaped leaves. Each leaf in the rosette is 10–30 mm long and 4–12 mm wide. Flowering plants have a single flower 20–25 mm long, 9–12 mm wide and which lean forwards slightly. The flower is borne on a flowering stem 100–150 mm high with between three and five leaves wrapped around the stem. The flowers are pale green and white with a brown tinge. The dorsal sepal and petals are fused, forming a hood or "galea" over the column. The dorsal sepal curves forward and downward with a thread-like tip 4–8 mm long. The lateral sepals are held closely against the galea, have an erect, curved thread-like tip 20–25 mm long and a narrow V-shaped sinus between their bases. The labellum is 14–17 mm long, about 3 mm wide, curved, pointed and extends for about half its length above the sinus. Flowering occurs from February to June.[2][3]

Taxonomy and naming

Pterostylis revoluta was first formally described in 1810 by Robert Brown and the description was published in the Prodromus Florae Novae Hollandiae et Insulae Van Diemen.[1][4] The specific epithet (revoluta) is a Latin word meaning "turned over" or "rolled back".[5]

Distribution and habitat

The autumn greenhood grows on sheltered slopes in forest and in coastal scrub in coastal and near-coastal area from south-east Queensland to Nowra in New South Wales and as far inland as Cessnock.[2][3]

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References
  1. "Pterostylis pedunculata". APNI. Retrieved 24 May 2017.
  2. Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. p. 296. ISBN 978-1877069123.
  3. Jones, David L. "Pterostylis revoluta". Royal Botanic Garden Sydney: plantnet. Retrieved 24 May 2017.
  4. Brown, Robert (1810). Prodromus Florae Novae Hollandiae et Insulae Van Diemen. London. p. 327. Retrieved 22 May 2017.
  5. Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press. p. 657.
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