Pterostylis dilatata

Pterostylis dilatata, commonly known as the robust snail orchid, is a species of orchid which is endemic to the south-west of Western Australia. Non-flowering plants have a rosette of leaves but flowering plants lack a rosette and have a single green and white flower on a flowering stem with stem leaves. The flowers appear in winter and have lateral sepals which almost close off the front of the flower.

Robust snail orchid
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Cranichideae
Genus: Pterostylis
Species:
P. dilatata
Binomial name
Pterostylis dilatata
Synonyms[1]
  • Linguella dilatata (A.S.George) D.L.Jones & M.A.Clem.
  • Diplodium dilatatum (A.S.George) D.L.Jones & M.A.Clem.

Description

Pterostylis dilatata is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette lying flat on the ground. Flowering plants lack a rosette but have a single green and white flower on a flowering stem 50–150 mm (2–6 in) tall with three to five stem leaves. The stem leaves are 4–20 mm (0.2–0.8 in) long and 1–4 mm (0.04–0.2 in) wide. The flower is green and white, 18–24 mm (0.7–0.9 in) long, 6–8 mm (0.2–0.3 in) wide. The dorsal sepal and petals form a hood over the column with the petals flared and the dorsal sepal having a short point. The lateral sepals are erect, fused for most of their length except for their thread-like tips which are 11–15 mm (0.4–0.6 in) long. The lateral sepals are in close contact with the gales and have a bulging sinus between them. The labellum is about 6 mm (0.2 in) long, 2 mm (0.08 in) wide and not visible outside the intact flower. Flowering occurs from May to August.[2][3][4][5]

Taxonomy and naming

Pterostylis dilatata was first formally described in 1984 by Alex George from a specimen collected near Bluff Knoll. The description was published in Nuytsia.[1] The specific epithet (dilatata) is a Latin word meaning "spread out", "enlarged" or "extended"[6] referring to the bloated base of the flower.[3]

Distribution and habitat

The robust snail orchid grows in shrubland, woodland and in soil pockets on granite outcrops between Geraldton and Israelite Bay in the Avon Wheatbelt, Esperance Plains, Geraldton Sandplains, Jarrah Forest, Swan Coastal Plain biogeographic regions of Western Australia.[3][7]

Conservation status

Pterostylis dilatata is classified as "not threatened" by the Government of Western Australia Department of Parks and Wildlife.[7]

References
  1. "Pterostylis dilatata". APNI. Retrieved 26 June 2016.
  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. 298. ISBN 978-1877069123.
  3. Brown, Andrew; Dixon, Kingsley; French, Christopher; Brockman, Garry (2013). Field guide to the orchids of Western Australia : the definitive guide to the native orchids of Western Australia. Simon Nevill Publications. p. 352. ISBN 9780980348149.
  4. Hoffman, Noel; Brown, Andrew (2011). Orchids of South-West Australia (3rd ed.). Gooseberry Hill: Noel Hoffman. p. 404. ISBN 9780646562322.
  5. Archer, William (2010-07-19). "Robust Snail Orchid - Pterostylis dilatata". Esperance Wildflowers. Retrieved 26 June 2017.
  6. Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press. p. 743.
  7. "Caladenia dilatata". FloraBase. Western Australian Government Department of Biodiversity, Conservation and Attractions.
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