aecium
/ˈiːsɪəm/Mycology
noun
A fruiting body produced on the mycelium of a rust fungus at a particular stage in its life cycle (especially, in heteroecious species, that occurring on an alternate host), within which aeciospores are produced.
Origin
Early 20th century. Shortened from aecidium, with omission of the medial syllable.