126 THE r6le of nitrogen in plant-metabolism, iii., 



which ought to be detected by the nitrous acid method. The 

 latter, however, gives no nitrogen after the phosphotungstic 

 precipitation and hydrolysis, and this result may be inter- 

 preted, either as proof of the absence of polypeptides, or 

 that, by steric hindrance, the reaction is made exceedingly 

 slow. 



