The Ascus Apex in Lichenized Fungi III. The Pertusaria-Type

Abstract

On the basis of light microscopic (LM), scanning electron microscopic (SEM) and transmission electron microscopic (TEM) investigations the Pertusaria-type of ascus is described as a particular functional type. The functionally unitunicate Pertusaria-type is characterized by its structure, staining properties, and by its particular mode of dehiscence. Tripartite ascus walls were observed in LM and TEM. The non-amyloid ascus wall is surrounded by a thin, amyloid outer layer. Both become amorphous at maturity and partly disintegrate. An apically thickened, amyloid inner layer reaches the base of the ascus. In its fine structure this amyloid inner layer resembles the material of the amyloid dome of Lecanora-type asci. It plays an important role during dehiscence and spore discharge. An elongation process was observed prior to dehiscence, at the end of which the ascus tip is situated above the hymenial surface. Dehiscence occurs by bursting or splitting of the whole ascus tip. The Pertusaria-type might represent a side-branch of evolution from bitunicate to unitunicate forms within the Lecanorales.Pertusaria-type asci are restricted to a small number of genera within the Pertusariaceae. A considerable heterogeneity in ascus structure and staining properties was observed within the Pertusariineae sensu Henssen & Jahns (1973) and Henssen (1976).

The Ascus Apex in Lichenized Fungi IV. Baeomyces and Icmadophila in Comparison with Cladonia (Lecanorales) and the Non-Lichenized Leotia (Helotiales)

“…It is highly probable that the Baeomycetaceae are not the only lichenized members of the Helotiales. The similarities in ascus structure, function and staining properties in the Baeomycetaceae and the Trapeliaceae, ' a family with no clear relationships' (Poelt 1974), and in some members of the Lecideaceae and Lecanoraceae were described by Hertel (1970) and Honegger (1982c). These groups deserve further investigation.…”

Airborne ascospore discharge with co‐dispersal of attached epihymenial algae in some foliicolous lichens

“…Further increase in pressure then dislodges and fires off this ascospore, while the next one in line lodges in the opening, and is then subsequently forced out; the process repeats in rapid succession until all spores have been ejected (Ingold, 1933). It is not clear to what extent this description applies to lichen-forming ascomycetes, which have a number of functionally variant ascus types (e.g., Honegger, 1978Honegger, , 1980Honegger, , 1982, and at least in some cases appear to fire off their eight ascospores in a single mass (Morando et al, 2019). The foliicolous lichens studied here produce only a single, large ascospore per ascus, which is likely to be of greater diameter than the opening formed at the tip of the ascus.…”

Ascomycete Systematics

“…Chadefaud et al, 1963Chadefaud et al, , 1967 or as drawings accompanied by photographs (e.g. Bellemere, this volume; Letrouit-Galinou, 1981, 1987;Hafellner and Bellemere, 1982a, 1982cHonegger, 1978Honegger, , 1980Honegger, , 1982b. It should be stressed that the ascal wall is not just a single character but provides many characters.…”