BY JAMES M. PETRIE. 841 



iii. The Amount of Non-Protein Nitrogen in Seeds. 



The following series of experiments with seeds of thirty 

 different plant species was carried out by the alcohol method of 

 separation. I may here recall the important statement of 

 Henriques and Hansen, referred to in Part i. (antea p.811) that 

 in their feeding experiments with the products of tryptic hydro- 

 lysis, only that portion soluble in alcohol sufficed for nutrition. 



The samples were air-dried and put through a grinding mill, 

 until almost the whole passed through a 0*5 mm. sieve. Two 

 estimations were then made on each. 



(1) The total nitrogen of the seeds. 



(2) The non-protein nitrogen as represented by the nitrogen 

 not precipitable by alcohol. 



For the latter, 1 gm. of the sample was extracted with 200 cc. 

 of cold distilled water by standing over night, boiled for 2 hours 

 on the w.b., decanted through a filter, the residue again boiled 

 with an equal volume of water for 1 hour and filtered, and the 

 operation repeated a third time. This of course did not perfectly 

 exhaust the seeds of their soluble nitrogen-compounds, but the 

 amount left was inconsiderable. The combined filtrates were 

 evaporated to about 10 cc, and poured into 90 cc. of methylated 

 spirit. The proteins were thereby precipitated in 85 % alcohol. 

 Heated to the boiling point in the w.b., and then allowed to 

 stand for at least 2 hours. The protein ppt. was then filtered 

 off; from the clear filtrate the alcohol w T as removed by distillation, 

 and the nitrogen in the residue determined. 



The results are arranged in descending order of the amounts 

 in the third column. It is seen that Acacia pycnantha contains 

 the highest amount, and also the highest ratio of non-protein 

 nitrogen; and that all the Acacias tested are high. The average 

 for the other leguminous seeds is 19 %, the lowest result being 

 15*7 %. The cereals contain the smallest amount of total 

 nitrogen, and still the non-protein ratio is about the same as in 

 the legumes; rye and wheat have conspicuously high values. 



