36 THE MICROBE AND ITS ACTIVITIES 



group, the actinomyces may be considered distinct, having char- 

 acteristics which place them in a position intermediate between 

 the bacteria and the filamentous fungi, although the majority of 

 the soil forms somewhat more closely resemble the fungi than the 

 bacteria. The mycelium is, however, much smaller in cross sec- 



FiG. 25. — Branching mycelium of Actinomyces (from Drechsler). 



tion than that of the filamentous fungi. The actinomyces are 

 relatively abundant in the soil, making up from 10 to 60 per cent 

 of the colonies developing on the plates which have been prepared 

 from soil, by the use of artificial media. Actinomyces are active 

 in the decomposition of a variety of organic substances in the 

 soil. 



Most of the actinomyces are aerobic, although possibly less 



