PHYSIOLOGY OF THE ACTINOMYCETES 359 



and show marked radial foldings. Such forms are at first smooth 

 and glistening on the surface, but later develop spores, when the 

 surface develops the powdery appearance mentioned above. Not 



Fig. 131. Colony of mold-like actinomycete, Streptomyces griseolus. 



Fig. 132. Colony of bacterium-like actinomycete, Actinomyces bovis. 



infrequently the aerial hyphae do not develop all over the surface, 

 but in concentric rings. In the second type the colonies are not so 

 tenacious, but tend rather to be of a mealy consistency, and are 

 not so adherent to the agar. Their surface is usually irregularly 

 wrinkled in all directions, not showing the radial folds. These colony 



