22 



SOIL BACTERIOLOGY 



7. The results of the plate counts may be tabulated as 

 follows : 



Table i. — Comparison of the Number of Bacteria on Different Culture-media 





Bacteria per plate. 



Bacteria in i gm. of soil. 



Medium. 



Total. 



Aver- 

 age. 



Liquefiers. 



Average. 



Fjquefiers. 





Total. 



Aver- 

 age. 



Average, 



Heyden Nahrstoff. 

 do. 

 do. 















Sodium asparaginate. 

 do. 

 do. 















Soil-extract agar, 

 do. 

 do. 















Casein agar, 

 do. 

 do. 















Soil-extract gelatin, 

 do. 

 do. 















Exercise 5 



Effect of Depth on Number of Bacteria 



I, The samples for this exercise should be drawn from 

 virgin soil well removed from any source of contamination. 

 Save some of this soil for Exercise 8, p. 42. The type of 

 soil will determine to a certain degree the number of 

 organisms at different depths. 



