69 



Potter and Snyder (1915 a) find this fraction to be present in 

 all of their eight soils, with a minimum of 1.99 per cent and a maxi- 

 mum of 6.30 per cent. They do not give sufficient analytical data 

 to permit a recalculation of their figures in order to ascertain if 

 any errors in calculation were made. However, it is possible that 

 their rinding is due to the fact that all of their mineral soils repre- 

 sented a single soil type. It is possible that this form of nitrogen 

 may have been especially abundant in their particular soil. It is 

 of particular interest to note that their soil was from the Wisconsin 

 drift area, as was my sample of Carrington silt loam from Morris- 

 town, which gave my maximum amount of nitrogen in this frac- 

 tion. The sample of Carrington silt loam from Nerstrand was sit- 

 uated on the Kansan drift and gave no "histidine" nitrogen. 



