archaeascus (noun,ascus term, pl. archaeasci;deprecated term) – an ascus type that was assumed to be archetypical, i. e., the evolutionary ancestral type from which all other ascus types are supposedly derived. The term archaeascus must no longer be used for several reasons: First, it is rather problematic to assume that any extant ascus type could be regarded as an original, ancestral type from which all other types have evolved. Second, the structures described as characteristic for the archaeascus are most probably artefacts. Structures like the apical nasse or the anneau apicale were described only from chitinoid and amyloid reactions as observed in the light microscope. These structures do not generally correspond well with ultrastructural observations and are possibly a result of examining aged herbarium material. Related terms: apical nasse, anneau apicale. Kind of: ascus.