370 W. E. TOTTINGHAM AND A. J. BECK 



relation held whether or not the acidity tending to develop by 

 hydrolysis of ferric chloride was prevented. 



5. Although the lower plane of concentration upon which iron 

 and manganese weVe employed here approaches that probably 

 obtaining in the average water extract of soils, the application 

 of the preceding conclusions to field conditions would be clearly 

 unjustified. A greater variety of component salts and various 

 other conditions might modify the effects of the elements in 

 question in soil cultures as compared with water cultures. The 

 soil phase of the problem therefore calls for further investigation. 



