EFFECT OF PLANT ROOTS ON NUMBER OF BACTERIA 2Q 



ment, plating from the same dilutions as in the second 

 count. 

 8. Tabulate the data. 



Table 6. — Effect of Partial SteriHzatwn on Number of Bactrria 



Time. 



Treatment. 



Dilution. 



Bacteria per platf 



Bacteria in t gm. 

 of dry soil. 



Days. 

 Beg. 

 Beg. 

 Beg. 



None. 

 ioo° C. 



1% CSa 





I 2 3 



Average 



Average. 



7 

 7 

 7 



None. 



IOO° C. 



1% cs. 











14 

 14 

 14 



None. 

 loo' C. 



1% cs. 











Exercise lo 

 Effect of Plant Roots on Number of Bacteria 



1. Collect soil samples from the immediate vicinity of 

 the roots of various plants (alfalfa, clover, etc.), and similar 

 samples i or 2 feet away from the plants. 



2. Prepare plate counts and moisture determinations of 

 these soils. 



3. Tabulate results as follows: 



Table t.— Effect of Plant Roots 



on Number of 



Bacteria 



No. 



Position. 



Bacteria per plate. 



Bacteria in i gra. 

 of dry soil. 



I 



2 



Near roots. 

 Away from roots. 



123 



/ .._ - -. 



Average 



Average. 



Increase or decrease , , , , 



