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Fungi Imperfecti[′fən‚jī ‚im·pər′fek‚tī]
(or Deuteromycetes), a class of higher fungi with a well-expressed branching multicellular mycelium. The fungi develop in a haploid state (haplophase), and reproduction is asexual, by means of conidia (spores). The life cycle for the most part does not include sexual stages characterized by formation of higher sporebearing forms. In many Fungi Imper-fecti the hyphae of the mycelium undergo anastomosis, which leads to the formation of heterokaryons—cells with genetically unlike nuclei. This causes recombination of genetic characters in the haploid state and extensive intraspecies variation with formation of new forms of the fungus.
The Fungi Imperfecti include approximately 30, 000 widely distributed species. They play an important ecological role: fungi populating the soil destroy plant and animal remains. Many Fungi Imperfecti are the causative agents of plant diseases; others form moldy deposits on food products and various industrial products. A number of Fungi Imperfecti, in particular Penicil-lium and Aspergillus (some species of these genera, which have perfect stages of sporebearing, are similar to the Ascomycetes), produce various such antibiotics as penicillin and griseofulvin, which are widely used in medicine. According to their type of sporebearing, the Fungi Imperfecti are divided into three orders —Hyphomycetes, Melanconiales, and Spheropsidales.
M. A. LITVINOV