36 



Microbiological Population of the Soil 



in soils and in composts. Their growth throughout the soil may be 

 so extensive as to hold the mass of particles together by means of 

 a very fine microscopic network of mycelium and its excretion prod- 



«^ 





2^ 



^ C 



^ 



^' 



^'->. 



V 





Fk;. 19. Micr()bii)l()gical population of soil, as shown by contact slide method: 

 a, h, d, different types of liacteria; c, fungus mycelium (from Cholodny). 



nets. Fungi vary greatly in their relation to higher forms of life, 

 notably plants (saprophytic vs. parasitic), to soil bacteria (forma- 

 tion of antibiotic substances), and to other members of the soil 

 population. 



4. Algae. These organisms comprise the grass-green Chloro- 

 phyceae, the blue-green Cyanophyccae, and the Diatomaceae. Their 



