Swamp onion orchid (Microtis atrata)
Description
Microtis atrata, commonly known as the swamp mignonette orchid or yellow onion orchid and sometimes as Microtidium atratum, is a species of orchid endemic to southern Australia of Western Australia. It has a single thin leaf and up to forty or more yellowish-green flowers. The flowers are the smallest of any Australian ground-dwelling orchid. The orchid usually grows in large colonies after fire and although small, are easily seen because of their very large numbers in their blackened surroundings. Microtis atrata is a terrestrial, perennial, deciduous, herb with an underground tuber and a single erect, smooth, more or less solid leaf, 30–90 mm (1–4 in) long and about 3 mm (0.1 in) wide. Between two and forty or more yellowish-green flowers are densely crowded along a flowering stem 10–40 mm (0.4–2 in) long, reaching to a height of 50–120 mm (2–5 in). The plants are sometimes up to 200 mm (8 in) tall if growing in water. At about 2 mm (0.08 in) long and wide, the flowers are the smallest of any terrestrial Australian orchid, and as they age, they turn black. The dorsal sepal is egg-shaped to round, about 1 mm (0.04 in) long and wide and forms a hood over the column. The lateral sepals are oblong, less than 1 mm (0.04 in) long and spread apart from each other. The petals are egg-shaped and concave and the labellum is oblong to egg-shaped. Flowering occurs from September to December and is stimulated by fire the previous summer.
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum:
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Class: Liliopsida
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Order: Asparagales
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Family: Orchidaceae
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Genus: Microtis
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