Diuris alba
{{Short description|Species of orchid}}
{{Italic title}}
{{Speciesbox
| name = White donkey orchid
| image = Diuris alba - Curtis' 101 - cut out from pl. 6201 (1875).jpg
| image_caption = Diuris alba from Curtis's Botanical Magazine
| genus = Diuris
| species = alba
| authority = R.Br.{{cite web |title=Diuris alba |url=https://biodiversity.org.au/nsl/services/apc-format/display/78724 |website=Australian Plant Census |accessdate=22 June 2023}}
| synonyms =
}}
Diuris alba, commonly called the white donkey orchid, is a species of orchid which is endemic to eastern Australia. It has up to three leaves, and a flowering stem with up to seven white flowers with purplish markings.
Description
Diuris alba is a tuberous, perennial herb, usually growing to a height of {{convert|150-400|mm|in|sigfig=1|abbr=on}}. There are up to three linear leaves arising from the base of the plant, each leaf {{convert|100-300|mm|in|sigfig=1|abbr=on}} long, {{convert|2-3|mm|in|sigfig=1|abbr=on}} wide and rolled so that the sides of the leaf face each other. There are between two and seven white flowers with lilac or purple markings arranged on a flowering stem, each flower about {{convert|20|mm|in|sigfig=1|abbr=on}} wide. The dorsal sepal is egg-shaped, {{convert|8-17|mm|in|sigfig=1|abbr=on}} long and {{convert|5-9|mm|in|sigfig=1|abbr=on}} wide with its margins turned downwards. The lateral sepals are linear to lance-shaped, {{convert|20-40|mm|in|sigfig=1|abbr=on}} long, {{convert|2-3|mm|in|sigfig=1|abbr=on}} wide and turned downwards, either parallel to each other or crossed. The petals are erect, ear-like above the flower, {{convert|10-22|mm|in|sigfig=1|abbr=on}} long and {{convert|4-8|mm|in|sigfig=1|abbr=on}} wide with a dark-coloured, stalk-like "claw" {{convert|4-6|mm|in|sigfig=2|abbr=on}} long. The labellum is {{convert|10-14|mm|in|sigfig=1|abbr=on}} long and has three lobes. The central lobe is a broad egg shape to almost circular, {{convert|7-11|mm|in|sigfig=1|abbr=on}} wide with a raised midline. The lateral lobes are linear to lance-shaped with the narrower end towards the base, {{convert|3-4|mm|in|sigfig=1|abbr=on}} long and {{convert|1-2|mm|in|sigfig=1|abbr=on}} wide. There are two broad calli {{convert|5-6|mm|in|sigfig=2|abbr=on}} long. Flowering occurs from August to November.{{cite web|last1=Jones|first1=David L.|title=Diuris alba|url=http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Diuris~alba|publisher=Royal Botanic Garden Sydney: plantNET|accessdate=11 November 2017}}
Taxonomy and naming
Diuris alba was first formally described in 1810 by Robert Brown and the description was published in Prodromus florae Novae Hollandiae.{{cite web|title=Duiris alba|url= https://id.biodiversity.org.au/instance/apni/493577|publisher=APNI|accessdate=13 September 2016}}{{cite book|last1=Brown|first1=Robert|title=Prodromus florae Novae Hollandiae|date=1810|location=London|page=315|url=https://www.biodiversitylibrary.org/item/21871#page/183/mode/1up|accessdate=12 March 2018}} The specific epithet (alba) is a Latin word meaning "white".{{cite book|last1=Brown|first1=Roland Wilbur|title=The Composition of Scientific Words|date=1956|publisher=Smithsonian Institution Press|location=Washington, D.C.|page =856}}
Distribution and habitat
The white donkey orchid occurs on the coast and nearby ranges of New South Wales and Queensland north from the Central Coast. It grows with grasses in forest.