Dehiscence
dehiscence (pl. dehiscences; synonym: sl. ascus dehiscence, pl. ascus dehiscences) – the process of opening and releasing ascospores from a mature ascus by rupture of the ascus wall, typically, but not always occurring at the ascus apex, sometimes explosive and/or actively ejecting spores, sometimes by gradual disintegration of the wall and subsequent release of spores; different modes of dehiscence have been distinguished: (1) evanescence (prototunicate: disintegration of the entire ascus wall; verrucaroid: disintegration of the apical ascus wall); (2) lateral rupture, i. e., tip sliding off like a hood, e. g., in Corneliales, or in Arthrorhaphis); (3) subapical rupture, i. e., opening with a lid (operculate, suboperculate, and pseudopoerculate); (4) apical rupture: (4a) formation of a simple pore with no elongation (inoperculate: annular, ostropalean or hypodermataceous); (4b) formation of a complex pore with predehiscent elongation (extenditunicate: bivalve or fissurate dehiscence); (4c) apical rupture with extrusion: semi-fissitunicate (rostrate and eversion-type; present in most lecanoralean asci) or fissitunicate (bitunicate , "jack in the box"); cf. dehiscent, non-dehiscent.
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