Soil Bacterial Types 



255 



i-apidly. At the date of the last sampling, three months after the ex- 

 periment was started, practically all of the green manure had broken 

 down and the bacterial counts were about the same as in those which 

 had received no green manure. 



At the date of the last sampling, ten colonies were picked from the 

 agar plates of each treatment, making one hundred colonies, and were 

 studied as previously described. Care was exercised to make as rep- 

 resentative a selection as possible from each set of plates. 



TABLE 2. Bacterial Types, as Influenced by CaCOs and Green Manure. 



Table 2 gives a summary of this work. As in the case of the total 

 bacterial counts, it is seen that the calcium carbonate treatments have 

 exerted no appreciable influence on the bacterial types. However the 

 application of the green manure has caused considerable disturbance in 

 the equilibrium existing between the various bacterial types. The rod 

 forms have increased from 42 per cent of the total to 62 per cent, largely 

 at the expense of the coccus forms. The spore formers have decreased 

 from 40 per cent to 32 per cent, and the gelatin liquefiers have increased 

 from 78 per cent to 86 per cent. 



While these results cover only one small angle of a very large 

 problem, they are indicative of what niay be accomplished in the future. 

 Each year it is becoming more apparent that our study of the soil flora 

 must be directed toward a more thorough knowledge of the bacterial 

 types and particularly the interrelationships existing between the various 

 groups. 



