The history ofPyrenophoraFr. was reviewed with special reference toPleosporaRab. It was concluded that the two genera are distinct. The following characteristics were found to be of diagnostic value forPyrenophora: ascocarps very large, sclerotioid, slow-maturing, usually setose, occurring on grasses; ascospores large, nearly cylindrical with rounded ends, with 3ndash;5ndash;7 transverse septa, and a longitudinal septum in from one to all cells depending on species. In addition, the known conidial states ofPyrenophorawere noted to be species of the hyphomycete genusDrechsleraIto.An authenticated specimen ofP. phaeocomesfrom the Fries Herbarium was used as a neotype in the apparent absence of Rebentisch's specimen. Numerous ascospores were found among the immature ascocarps on the leaves, and taken as evidence that the fungus is an ascomycete. The conidial-state association was tenuously confirmed by the presence of oneDrechsleraconidium. It was concluded that the namePyrenophoracan be used for the genus of ascomycetes typified byP. phaeocomes.
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