Isolates previously identified as Microsporum gypseum (Bodin) Guiart & Grigorakis have been found to be the imperfect states ofNannizzia incurvata Stockdale, N. gypsea (Nannizzi) comb. nov. and W.fulva sp. nov. The three species are heterothallic and cross-mating does not occur between them. They show slight but constant differences in their colonial and microscopic appearance on agar media and in the form of the peridial hyphae and appendages of their cleistothecia.Although the Microsporum states of N. incurvata and N. gypsea can be distinguished from each other it has been impossible to decide which, if either, of these is M. gypseum, sensu stricto. The imperfect state of N. fulva is M. fulvum Uriburu which had previously been considered synonymous with M. gypseum.In a previous report describing Nannizzia incurvata as a perfect state of Microsporum gypseum (Bodin) Guiart & Grigorakis (Stockdale, 1961) certain differences were noted between N. incurvata and Gymnoascus gypseus, described as the perfect state ofM. gypseum by Nannizzi (1927). It was also found that five of 12 isolates identified as M. gypseum failed to form cleistothecia alone or when mated with single ascospore isolates of N. incurvata.Other reports of the rediscovery of the perfect state of M. gypseum have been made: Griffin (1960) isolated a fungus which he considered to be conspecific with G. gypseus Nannizzi, although he found some differences and gave an amended diagnosis; and Szathm~ry & Herpay (1960) described the cleistothecia of M. gypseum and those of a closely related fungus, "Epidermophyton radiosulcatum var. flavum" Szathm~ry. The cleistothecia described by Szathm~ry & Herpay for M. gypseum closely resembled those of G. gypseus. OBSERVATIONSCultures of Griffin's isolate of G. gypseus and Szathm~try's isolate of "E. radiosulcatum var. flavum" were obtained and slight differences between their cleistothecia and those of N. incurvata were observed. Single ascospore isolations were made by Miss Christine Dawson, University of Glasgow, and G. ~pseus and the perfect state of "Epidermophyton radiosulcatum var. flavum", like N. incurvata (Stockdale, 1961), were found to be heterothallic.Attempts were then made to cross-mate the three fungi, but without success; cleistothecia were formed only when compatible mating strains from the same parent were mated. All available isolates which had been identified as M. gypseum and did not form cleistothecia by themselves were then mated with the single ascospore isolates. Of the five which had failed to mate with N. incurvata three mated with G. gypseus and two with "E. radiosulcatum var. flavum". None mated with more than one of the single ascospore isolates. 114 at Michigan State University on February 9, 2015 http://sabouraudia.oxfordjournals.org/ Downloaded from THE MICROSPORUM GYPSEUM COMPLEX 1 15Small but constant differences in the cultural and microscopical characters of the imperfect states of the three fungi were also observed, and these were sufficient for isolates subsequently received at th...

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