412 



Journal of Agricultural Research 



Vol. VI, No. II 



organism. This set of organisms are, however, more resistant to copper 

 than are others, and what we have occurring is a suppression of other 

 types which feed on nitrates, thus permitting a greater accumulation 



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Fig. 5. — Graph showing parts per million of various arsenic compounds in the soil at which the greatest 



stimulation occurred. 



of nitrates under these conditions. While not so likely in the other 

 cases, the same possibility does arise. This, however, can be answered 

 definitely only by further experiments. 



