Electronic Flora of South Australia
Electronic Flora of South Australia
Census of SA Plants, Algae & Fungi
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Electronic Flora of South Australia genus Fact Sheet

Family: Orchidaceae

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.

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:  Endemic to Australia except for 1 representative in Indonesia; about 45 species.

Biology: Pollination is effected chiefly by native bees and sympatric species commonly form hybrids.

Key to Species:
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
2. Dorsal sepal 9-nerved; petals 7-nerved; petals and labellum less than 15 mm long; flowers not nodding
D. x fastidiosa 2.
2. Nerves on the dorsal sepal and petals inconspicuous; petals and labellum 15-20 mm long; flowers often nodding
3. Flower yellow
D. lanceolata 3.
3. Flower purple
D. punctata 8.
1. Dorsal sepal and/or petals normally spotted with conspicuous dark-brown or purple-brown markings or blotches
4. Lateral lobes of the labellum large, as long or nearly as long as the middle one
5. Lateral sepals greatly exceeding the petals in length, often nearly twice as long; leaves 6 or more, setaceous or almost so
D. palustris 7.
5. Lateral sepals shorter than, or approximately equal in length to the petals; leaves not setaceous
6. Lateral sepals usually crossed; blotches generally distinctly demarcated from the yellow ground colour; 2 longitudinal raised lines at the base of the labellum
D. maculata 5.
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
D. longifolia 4.
4. Lateral lobes of the labellum very much shorter than the middle one
7. One longitudinal raised line along the base of the labellum
D. sulphurea 9.
7. Two longitudinal raised lines along the base of the labellum
8. Dorsal sepal with small dots and shorter markings; labellum usually emarginate to obtuse; leaves to 17 cm long
D. x palachila 6.
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
D. brevifolia 1.

Author: Not yet available

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