100 GENERAL MICROBIOLOGY 



GENERAL CHARACTERISTICS OF MOLD GROWTH 

 AND HINTS FOR STUDY 



A brief description of the molds to be studied in the 

 laboratory is here given. The references cited will give 

 more in detail of their structure, importance and occur- 

 rence. 



In these descriptions, there have been noted the parts 

 of the structure of each mold that are to be found micro- 

 scopically and drawn, also the quickest method of obtain- 

 ing the best results. All microscopic drawings and meas- 

 urements can be secured from the adhesion culture or the 

 moist-chamber culture. 



Rhizopus nigricans Black mold 

 (Mucor stolonifer) 



The mycelium in the advanced stage consists of rhizoids 

 (rootlets), bearing clusters of sporangiophores, joined by 

 long hyphse (the stolons) to the mycelium proper. The 

 hyphse are non-septate. 



The fruiting bodies consist of typical sporangia (spore 

 cases containing spores) borne on the enlarged end (col- 

 umella) of the sporangiophore. Spores are liberated by the 

 bursting of the sporangium. 



The columella can be observed in fruiting bodies of a 

 light brown color; white sporangia are too young and black 

 too old to show this structure. If no fruiting bodies grow 

 in the adhesion culture, they may be studied directly from 

 a plate culture by preparing a glycerin slide. Take care 

 not to burst the sporangium when transferring it to the 

 slide. 



Aspergillus niger Black mold 



The mycelium of this mold consists of septate hyphse 

 with frequent dichotomous branching. 



