Fungi Imperfecti

Members of Phycomycetes, Ascomycetes, and Basidiomycetes all exhibit perfect stages in their reproductive cycles, producing zygospores, oospores, ascospores, or basidiospores. They also reproduce asexually by conidia. More than 10,000 species of fungus, however, do not reveal any perfect stage and reproduce only by conidia. Because the accepted method of classifying fungi is based on the fruiting structures exhibited in the perfect phase and such forms show evidence of only an imperfect phase, they are placed in a taxonomic catchall called the Fungi Imperfecti. Each year, studies of species relegated to Fungi Imperfecti uncover perfect stages; this makes possible removing such forms from Fungi knperfecti and placing them in their proper classes. Some forms classified as Fungi Imperfecti for many years have eventually been properly reclassified. Reclassification is most often made to Ascomycetes and sometimes to Basidiomycetes. Does this mean a gradual demise of Fungi Imperfecti? The answer is “no,” because many newly discovered species are added to this group. Also, many forms of fungi have permanently lost (or never had) the capacity for perfect reproduction: these will remain in Fungi Imperfecti. (Many of these fungi are of great importance because they are parasites that cause diseases of plants, animals, and human beings.) The conidial stages of most of these fungi are similar to conidial stages of Ascomycetes.

The hyphae of this group are septate, having cross walls at the ends of cells. The end walls each have a central perforation (also seen in Ascomycetes) that allows the movement of cytoplasm and nuclei from one cell to another. The cells are usually multinucleated.