MOLD OR HYPHOMYCETE GROUP 393 







clature. The pathologists and bacteriologists who have de- 

 scribed the organisms have rarely paid any attention to 

 their botanical relationships, and the organisms themselves, 

 for the most part, have been ignored by the botanist in his 

 classification. 



As before stated, the possession of a more or less definite 

 mycelium, a more or less " mold-like " growth, and the general 

 production of spores are all that is needed to include an organism 

 in the group. Many of the organisms of the group are very com- 

 mon in nature and are pathogenic only under exceptional condi- 

 tions, while others have so adapted themselves to a parasitic 

 existence that they may be regarded as obligate parasites. Many, 

 too, have been noted once or twice only in certain pathological 

 conditions, and it is by no means certain that they were more than 

 accidental saprophytes. 



The genera of molds containing species of known pathogenicity 

 are 



Aspergillus. 



Penicillium. 



Fusarium. 



Sporotrickum. 



Microsporon and Trichophyton. 



Achorion. 



Oldium or Oospora. 



THE GENUS ASPERGILLUS 



The Aspergilli are widely distributed in nature. They are 

 abundant in the soil and on decaying materials of all kinds. 

 Their spores are common in the air, and cultures may readily be 

 secured in most localities by simple plate exposure. They are not, 

 however, present in such numbers as the genus next to be de- 

 scribed, Penicillium. Several hundred species have been de- 

 scribed, and by some authors the genus is subdivided into two 

 genera, Aspergillus and Sterigmatocystis. 



Aspergillus is placed by the botanists among the Ascomycetes 

 or sac fungi, because at one stage in the life history sexual repro- 

 duction occurs, resulting in the formation of sacs filled with spores. 

 This phase of the life history has been worked out in but few species; 



