Family: Orchidaceae
Diuris
Citation:
Smith, Trans. Linn. Soc. 4:222 (1798).
Derivation: Greek dis, two; oura, a tail; referring to the lateral sepals.
Synonymy: Not Applicable Common name: Donkey-orchids.
Description:
Terrestrial glabrous plants with underground tubers and several imbricate scales at the base of the scape; leaves more than one, generally several, narrow, at or near the base, with a few stem bracts higher up.
Flowers resupinate, 1, 2, or more, in a terminal raceme, rather large and conspicuous, yellow, purple, or white, often spotted or blotched with dark-brown or purple; dorsal sepal erect or slightly recurved at the apex, more or less ovate, its tip blunt and its base clasping the column; lateral sepals narrow-linear, often herbaceous, spreading or deflexed, parallel or crossed, exceeding the dorsal sepal in length; petals longer than the dorsal sepal, oval, elliptical or orbicular, on slender stalks, erect or spreading; labellum usually as long as or longer than the dorsal sepal, deeply 3-lobed; the middle lobe much contracted at the base, with 1 or 2 raised longitudinal lines along the narrow part; column very short, the sexual elements arising separately from the floral receptacle, at first quite separate, but united as the flower approaches maturity by an adhesion between the pollen-masses and the viscid disk of the rostellum; anther erect, 2-celled, on a very short filament, margins of the filament produced into erect lateral lobes or wings not adnate to the stigmatic-plate; stigma borne on a widened style or "plate" in front of the anther, a slot in its upper border representing the rostellum and likewise enclosing the loose viscid disk, the latter attached at maturity to the apices of the pollinia without intervention of a caudicle; pollinia 2, each deeply 2-lobed, suspended behind the stigma from the back of the viscid disk; pollen-masses mealy.
Distribution:
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Endemic to Australia except for 1 representative in Indonesia; about 45 species.
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Biology:
Pollination is effected chiefly by native bees and sympatric species commonly form hybrids.
Key to Species:
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1. Dorsal sepal and petals without spots or blotches (clear canary to chrome, rarely orange-yellow or purple), but sometimes with a few brown streaks towards their claws |
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2. Dorsal sepal 9-nerved; petals 7-nerved; petals and labellum less than 15 mm long; flowers not nodding |
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D. x fastidiosa 2. |
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2. Nerves on the dorsal sepal and petals inconspicuous; petals and labellum 15-20 mm long; flowers often nodding |
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D. lanceolata 3. |
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D. punctata 8. |
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1. Dorsal sepal and/or petals normally spotted with conspicuous dark-brown or purple-brown markings or blotches |
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4. Lateral lobes of the labellum large, as long or nearly as long as the middle one |
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5. Lateral sepals greatly exceeding the petals in length, often nearly twice as long; leaves 6 or more, setaceous or almost so |
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D. palustris 7. |
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5. Lateral sepals shorter than, or approximately equal in length to the petals; leaves not setaceous |
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6. Lateral sepals usually crossed; blotches generally distinctly demarcated from the yellow ground colour; 2 longitudinal raised lines at the base of the labellum |
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D. maculata 5. |
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6. Lateral sepals nearly parallel; flowers wall-flower colour, dark blotches merging into the yellow ground-colour; 1 raised line at the base of the labellum |
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D. longifolia 4. |
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4. Lateral lobes of the labellum very much shorter than the middle one |
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7. One longitudinal raised line along the base of the labellum |
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D. sulphurea 9. |
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7. Two longitudinal raised lines along the base of the labellum |
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8. Dorsal sepal with small dots and shorter markings; labellum usually emarginate to obtuse; leaves to 17 cm long |
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D. x palachila 6. |
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8. Dorsal sepal with 2 conspicuous brown dots at the base of the lamina; labellum acute, basally the lines surrounded in front and on both sides by a conspicuous dark-brown border; leaves 7-12 cm long |
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D. brevifolia 1. |
Author:
Not yet available
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