Genoplesium citriodorum

Genoplesium citriodorum, commonly known as the lemon-scented midge orchid and as Corunastylis citriodorum in Australia, is a small terrestrial orchid endemic to New South Wales. It has a single thin leaf fused to the flowering stem and up to thirty three small, lemon scented, dark purplish black flowers. It usually grows under shrubs in shallow sandstone soil in the Blue Mountains.

Lemon-scented midge orchid
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Diurideae
Genus: Genoplesium
Species:
G. citriodorum
Binomial name
Genoplesium citriodorum
Synonyms[1]

Description

Genoplesium citriodorum is a terrestrial, perennial, deciduous, herb with an underground tuber and a single thin leaf 200–300 mm (8–10 in) long and fused to the flowering stem with the free part 15–20 mm (0.6–0.8 in) long. Between twenty and thirty three dark purplish black flowers are arranged along a flowering stem 30–40 mm (1–2 in) tall and taller than the leaf. The flowers are about 6 mm (0.24 in) long and 5 mm (0.20 in) wide and lean forward. As with others in the genus, the flowers are inverted so that the labellum is above the column rather than below it. The dorsal sepal is narrow egg-shaped, about 5 mm (0.20 in) long and 2 mm (0.08 in) wide with prominent red lines and sparsely hairy edges. The lateral sepals are about 5.5 mm (0.2 in) long, 1.5 mm (0.06 in) wide, turn downwards and spread widely apart from each other. The petals are narrow egg-shaped, about 3.5 mm (0.1 in) long, 1 mm (0.04 in) wide with prominent stripes and hairy edges. The labellum is purple, narrow egg-shaped, about 4 mm (0.2 in) long, 1.5 mm (0.06 in) wide, with many hairs up to 1 mm (0.04 in) on its edges. There is a dark reddish purple callus in the centre of the labellum and extending two-thirds of the way to its tip. Flowering occurs between December and April.[2][3][4]

Taxonomy and naming

The lemon scented midge orchid was first formally described in 1991 by David Jones and Mark Clements who gave it the name Genoplesium citriodorum and published the description in Australian Orchid Research.[5] In 2002, Jones and Clements changed the name to Corunastylis citriodora.[6] The specific epithet (citriodorum) is derived from the Latin words citrea meaning "the citron-tree"[7]:206 and odor meaning "smell",[7]:568 referring to the strongly lemon-scented flowers.[2]

Distribution and habitat

Genoplesium citriodorum is only known from the Blue Mountains at heights of 900–1,200 m (3,000–4,000 ft) where it grows under shrubs in shallow soil over sandstone and sometimes in permanently wet areas.[2][3][4]

References
  1. "Genoplesium citriodorum". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew.
  2. Jones, David L.; Clements, Mark A. (1991). "Contributions to Australian orchidology". Australian Orchid Research. 2: 67.
  3. Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. pp. 176–177. ISBN 1877069124.
  4. Jones, David L. "Genoplesium citriodorum". Royal Botanic Garden Sydney. Retrieved 30 January 2018.
  5. "Genoplesium citriodorum". APNI. Retrieved 30 January 2018.
  6. "Corunastylis citriodora". APNI. Retrieved 30 January 2018.
  7. Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press.
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