dehiscence type (pl. dehiscence types) – major categories of asci distinguished by their functional and structural differences in dehiscence; not to be confused with the large variety of ascus types. Two main categories were originally recognized in ascomycetes: the unitunicate and the bitunicate ascus. It soon became evident, however, that these two categories are not adequate to distinguish all major structural and functional differences in ascus dehiscence. More recently nine categories have been distinguished, some of these categories being further distinguished into ascus types because of differences in their apical structure: prototunicate, unitunicate, bitunicate, lecanoralean, annular, hypodermataceous, operculate, suboperculate, pseudooperculate, ostropalean, and verrucaroid.