1428 AGRICULTURAL BOTANY, CHKMISTRY AND PHYSIOLOGY OF PLANT.S 



nitrogen was estimated by the Joldbauer method ; insohtble nitrogen re- 

 presented that part left undissolved after prolonged shaking with water ; 

 soluble nitrogen was divided into the nitrogen precipitated by phospho- 

 tungstic acid, the nitrogen in the filtrate from this precipitate and a further 

 fraction obtained by distilling the water soluble nitrogen with sodium 

 hydroxide. Results are given in Tables III and IV. 



The experiments v/ere repeated with so^^bean and with cowpeas and 

 the following conclusions were drawn : 



(i) The total nitrogen determinations show that about 74 per cent 

 of the nitrogen of the cowpeas and soybeans at the time of harvest is in 

 the tops, while the remainder is distributed between the roots and the 

 nodules. In the earlier periods the roots contain the larger part while 

 later they contain much the smaller part. 



(2) The percentage of soluble nitrogen in soybeans and cowpeas 

 varies with the different parts of the plant and with the period of growth. 

 In these experiments the soluble nitrogen, as an average, constituted in 

 the tops about 45 per cent of the total nitrogen ; in the roots 34 per cent ; 

 in the nodules of the soybeans i per cent, and in the nodules of the cow- 

 peas 34 per cent. 



(3) Phosphotungstic acid usually precipitates some form of uitro- 



