MOLDS 47 



constantly found upon every kind of putrescible matter, especially as 

 the causes of fermentation or decay in food. Their spores (conidia) are 

 produced in countless numbers, and are so, light that they float in air 

 currents and are carried by contact in every conceivable manner by 

 animals and by man. The Hfe cycle from spore to spore is frequently 

 very short, often being completed in twenty-four hours or less. Many 

 of these forms are propagated for an indefinite number of generations by 

 asexual spores or conidia, while for some of them no sexual-fruiting form 

 is known. These species are the "weeds" of the bacterial culture- 

 room, since they cannot be entirely eUminated and will survive, as a 

 rule, conditions more severe than the bacteria themselves. 



Molds of Fermentation. — A few species have acquired special 

 importance by their fermentative action. In most cases these forms 

 are widely distributed and able to utilize other media and conditions 

 also. They differ from closely related species of the same genera in the 

 ability to produce special enzymes or specially large amounts of such 

 enzymes as bring about particular forms of fermentation. Certain of 

 these species have been utilized in the manufacture of drinks, of citric 

 acid, in cheese ripening, etc. Others are so adapted to growth under 

 conditions of fermentation as to be found constantly in connection with 

 such processes, in which their vigorous growth and fermenting power ' 

 seriously interferes with control of results. 



Parasites and Facultative Parasites. — A few molds are found 

 as primary agents in causing diseases of man and animals. Some others 

 enter as secondary infections, but become pathogenic after entrance. 

 These comprise species of Aspergillus and Penicillium which produce 

 disease in the external ear of man, Aspergillus fumigaPus, a cause of lung 

 disease of birds, and the series of forms causing skin diseases, derma- 

 tomycoses, of both man and animals. 



Generic Consideration of Groups* 



The MupoRS or Black Molds.— The mucors or black molds con- 

 stitute a large group of species belonging to the Phycomycetes or algal 



•The series o£ forms presented contains representatives of the most common groups as 

 they occur in laboratory cultures, and such as have acquired importance to the worker in 

 bacteriology by participation in processes regularly studied by the bacteriologist. For more 

 complete discussion of the fungi, the student is referred to standard text-books of cryptogamic 

 botany. For discussions of species, Lafar's Technical Mycology includes the groups found 

 associated with the bacteria; for other groups, special botanical literature must be consulted. 



