{{short description|Reproductive structure of fungi producing aeciospores}} {{refimprove|date=January 2017}}
[[File:Puccinia aecidia 0482.jpg|thumb|Close up of aecia of ''Puccinia sessilis'']]An '''aecium''' (plural '''aecia''') is a specialised reproductive structure found in some plant pathogenic rust fungi that produce aeciospores. Aecia may also be referred to as "cluster cups". The term aecidium (plural aecidia) is used interchangeably but is not preferred.<ref>{{cite book |last1=Ulloa |first1=Miguel |last2=Hanlin |first2=Richard T. |title=Illustrated dictionary of mycology |date=2000 |publisher=APS Press |isbn=0-89054-257-0}}</ref>
In some rust fungi such as ''Phragmidium'', aecia lack an outer wall structure (a peridium) but instead produce a diffuse aecium called a caeoma.<ref>''Fungi''. Lilian E Hawker, 1966, Hutchinson University Library</ref>
[[File:Gall on nettle - geograph.org.uk - 947367.jpg|thumb|A rust gall covered with aecia]]In some species of rust fungi with a life cycle including two different host plants, the binucleate spores produced in the aecia cannot infect the current plant host, but must infect a different plant species.
== References == {{reflist}}
Category:Fungal morphology and anatomy Category:Reproductive system
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