CHAPTER V 



MOLDS BELONGING TO THE FUNGI IMPERFECTI AND 



THE ASCOMYCETES 



Among the molds encountered by the bacteriologist, Ascomycetes 

 are comparatively scarce. The Fungi Imperfecti, however, are abun- 

 dant. Since many of the latter forms show a similarity to or identity 

 with the conidial stages of known Ascomycetes, both classes may 

 conveniently be considered together here. 



Many species of Fungi Imperfecti, often only after extended study, 

 have been found to be asexual stages of perfect fungi, and un- 

 doubtedly more species in the future 'will be found to have a perfect 

 stage. But all species of Fungi Imperfecti are not necessarily merely 

 conidial stages of perfect fungi ; in the course of evolution they may 

 have permanently lost their ability to form sexual spores at all. 

 Some of the most widespread and vigorous molds have never been 

 shown to possess a perfect stage although they have had almost con- 

 tinuous study for over half a century. 



The point of view that Fungi Imperfecti are merely conidial 

 stages of sexual fungi has led many mycologists almost to ignore 

 them, or to treat them in their discussions with the perfect fungi 

 which have a similar conidial apparatus and, often, as here treated, 

 to give minor attention to the asexual stage. This in no way helps 

 the worker who wishes to know the identity or to understand the 

 morphology of the mold which he isolates from the lesion of a patient 

 or one which he has found to have industrial or biochemical impor- 

 tance. His mold, as he must study it, does not form sexual spores. 

 Even in those in which the perfect stage has been found, these sexual 

 spores are in many cases produced only rarely and under exceptional 

 conditions. Such a worker must depend upon classifications based 

 on the asexual stage. 



At best, any classification of the Fungi Imperfecti must be more 

 or less artificial, not necessarily indicating phylogenetic relation- 

 ships. However, it is evident that in many cases species closely re- 

 lated on the basis of their sexual spores had already been classified 

 together on the basis of their conidial stages.®- ^^ 



The problem is complicated by the fact that in many cases it is 

 somewhat difficult to decide just what are the conidia. As pointed 



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