Pterostylis alata

Pterostylis alata, commonly known as the striped greenhood, is a species of orchid endemic to Tasmania. As with similar orchids, the flowering plants differ from those which are not flowering. The non-flowering plants have a rosette of leaves but the flowering plants have a single flower with leaves on the flowering spike. This greenhood has a white flower with prominent dark green stripes and a sharply pointed, brown-tipped dorsal sepal. Similar greenhoods growing on the Australian mainland were formerly known as Pterostylis alata but are now given the name Pterostylis striata.

Striped greenhood
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Cranichideae
Genus: Pterostylis
Species:
P. alata
Binomial name
Pterostylis alata
Synonyms[2]

Description

Pterostylis alata is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette of dark green, wrinkled leaves, 4–20 mm (0.2–0.8 in) long and 3–12 mm (0.1–0.5 in) wide. Flowering plants have a single flower 17–21 mm (0.7–0.8 in) long and 6–7 mm (0.2–0.3 in) wide borne on a spike 80–250 mm (3–10 in) high. The flowers are white with dark green stripes. The dorsal sepal and petals are fused, forming a hood or "galea" over the column. The dorsal sepal curves forward with a narrow point 2–5 mm (0.08–0.2 in) long and is brownish near the tip. The lateral sepals are held closely against the galea, have erect, thread-like tips 23–27 mm (0.9–1 in) long and a broad V-shaped sinus between their bases. The labellum is 10–12 mm (0.4–0.5 in) long, about 3 mm (0.1 in) wide, brown and curved and protrudes above the sinus. Flowering occurs from May to August but mainly in June and July.[3][4]

Taxonomy and naming

The striped greenhood was first formally described in 1806 by Jacques Labillardière who gave it the name Disperis alata. (Disperis is a genus of orchid mainly from Africa and Madagascar.) Labillardière published the description in Novae Hollandiae Plantarum Specimen from a plant he collected "in Van-Diemen's Land".[5][6] In 1871 Heinrich Reichenbach changed the name to Pterostylis alata.[1] The specific epithet (alata) is a Latin word meaning "winged".[7]

Distribution and habitat

Pterostylis alata grows in open forest and coastal scrub in Tasmania.[3][2] Pterostylis alata does not grow on the mainland of Australia and plants formerly placed in this species are now recognised as Pterostylis striata.[8][9]

References
  1. "Pterostylis alata". APNI. Retrieved 8 June 2017.
  2. Jones, David L. (1998). "Contributions to Tasmanian Orchidology". Australian Orchid Researcu. 3: 139.
  3. Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. p. 290. ISBN 978-1877069123.
  4. "Flowering times of Tasmanian orchids" (PDF). Tasmanian Government Department of Primary Industries, Parks, Water and Environment. Retrieved 8 June 2017.
  5. "Disperis alata". APNI. Retrieved 8 June 2017.
  6. Clements, Mark A. (2013). The allure of orchids. Canberra, A.C.T.: National Library of Australia. p. 3. ISBN 9780642278074.
  7. Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press. p. 77.
  8. Jones, David L. "Pterostylis striata". Royal Botanic Gardens Sydney: plantnet. Retrieved 8 June 2017.
  9. "Pterostylis alata". Royal Botanic Gardens Melbourne: vicflora. Retrieved 8 June 2017.
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