978 THE HIGHER BACTERIA, MOLDS AND FUNGI 



The Phycomycetes, Ascomycctes and Hyphomycetcs arc the only 

 groups that need be considered here. The two former concern us 

 chiefly because they are found so frequently as contaminants in 

 bacterial cultures and will be briefly discussed. 



PHYCOMYCETES 



Members of the genus Mucor belonging to this order frequently 

 appear in agar plates which have been opened. They develop as a 

 mesh of delicate white filaments completely filling the plate and press- 



FIG. 106. MUCOR MUCEDO. Single-celled mycelium with three hyphse and one 

 developed sporangium. (After Kny, from Tnvel.) 



ing against the cover. The sporangia can be seen with the naked 

 eye as black dots scattered through the growth. On opening such a 

 plate the meshwork quickly collapses and forms a white speckled 

 feltwork over the medium. 



Microscopically the mycelium consists of branching tubular fila- 

 ments with or without septa. The usual mode of reproduction is by 

 asexual spores. These develop in the tip of a hypha which enlarges 

 to form a spherical or pear-shaped capsule, the sporangium. The 

 septum 'which divides it from the supporting hypha bulges into the 

 sporangium, forming the columella. Within the capsule innumerable 



