Dothideomycetes » Dothideomycetes, genera incertae sedis


Perischizon Syd. & P. Syd., in Sydow & Sydow, Annls mycol. 12(3): 265 (1914).

 Index Fungorum number: IF 3822; Facesoffungi number: FoF 12365, 3 morphological species (Species Fungorum 2022), no molecular data available.

Parasitic on leaves: Sexual morph: Leaf spots scattered, circular to elliptical, occasionally confluent, with a slight reddish-brown discoloration, on one or the other but generally not simultaneously both sides of the leaf with superficial dark brown to black ascomata, the whole leaf underneath the colony reddish brown. External hyphae not observed. Internal hyphae colorless to pale brown, septate, branched, intergrading with the stroma, intercellular. In external appearance stroma discoid, at times elliptical or variable in shape, flat at the top but occasionally with a central protruding wart, confluent, generally rather matt but sometimes shiny. Stroma in vertical section, forming a complex structure originating below the cuticle from where it grows outwards to form the superficial crust. Sometimes poorly developed, appearing as masses of brown hyphae filling the epidermal cells or forming anchor-like arms at intervals, composed of brown to dark brown cells forming a textura angularis which becomes hyaline and penetrates deeply into the epidermal cells and mesophyll. Asexual morph: not reported. Teleomorph: Ascomata erumpent, easily visible to the unaided eye. External appearance pulvinate or variable in shape, with a clearly defined edge, steep sides and a rather flat loop, sometimes with a central protruding circular wart, dark brown to black generally rather matt but rarely shiny in the central part, initially without an aperture, later opening by a circumferential fissure or by one or more irregular fissures to the side of or around the central wart. In horizontal section; with an upper wall composed of angular to prismatic cells, with dark brown walls, becoming laciniate towards the edge which is well defined. In vertical section; above the leaf cuticle, composed of separate blackened upper and lower walls enclosing one or more fertile locules with a stromatic column (similar to but distinct from the upper wall) located between locules and under the central protruding circular wart, connecting the upper wall in the region of the wart to stromatic tissue extending down within the leaf, typically with a small portion of displaced cuticle above the wart and stromatic column. The column composed of brown to dark brown, prismatic or sometimes angular cells. Upper wall dense brown to dark brown making interpretation of individual layers difficult, composed of cells forming a textura angularis. Lower wall, composed of angular cells, brown to dark brown forming a textura angularis. Locule composed of a hyaline basal cushion merged with the lower wall cells, not easily visible, with parallel asci and interthecial filaments above that cushion and covered at their apex by a gelatinous layer which appears brown partly because of embedded broken remnants of upper wall. Asci maturing sequentially with young asci and asci containing fully formed brown ascospores in the same locule, probably with more than one functional wall layer. Young asci initially almost globose, becoming clavate to broadly clavate, sometime slightly forked at the base, thick-walled at the apex with a subapical chamber visible before spores can be seen. Full sized asci containing spores, broad clavate, not changing color in IKI, containing up to 8 ascospores arranged in one or two rows or sometimes in clusters. Asci after spore release: collapsed with large apical crack in the outer wall and with the inner extending through the crack. Ascospores initially hyaline, with a mucous sheath, becoming brownuniseptate verrucose ellipsoidal, slightly narrowed at the septum with the lower cell slightly attenuated and the upper cell with a domed apex. Interthecial tissues: septate, smooth, colorless to light brown, thin-walled filiform, sometimes slightly swollen and rounded at the top, branching dichotomously at an acute angle with branches tending to occur near the top of an individual cell immersed in a hymenial gel which includes near the top some brown to dark brown remnants of the broken upper wall (adapted from Inácio and Cannon 2008).


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