97 



THE ROLE OF NITROGEN IN PLANT-METABOLISM. 



Part iii. — The Distribution of Nitrogen in 

 Acacia Seeds. 



By James M. Petrie, D.Sc, F.I.C, Linnean-Macleay 

 Fellow of the Society in Bio-Chemistry. 



(From the Phi/siolof/ical Laboratory nf the University of 



Sydney.) 



As a large stock of the seeds of Acacia injcnantha was 

 made available to the writer some time ago, the opportunity 

 was taken to make an experimental stvxdy of the protei-is 

 and other nitrogen compounds contained in them. The seeds 

 were in a mature condition and had been kept about two 

 years in stock. 



Preliminary E xaminatioii . — For the purpose of analysis, a 

 quantity of the seeds, w'th their tightly adhering black tests 

 left on, was crushed as finely as possible in a small mill. A 

 portion was dried at 100° C, to ascertain the amount of 

 moisture ; the residue was incinerated and the weight of the 

 ash noted. In another portion, the nitrogen was estimated 

 by Kjeldahl's method. As it would be a matter of very great 

 difficulty to separate the different parts of these seeds 

 mechanically, it was expected that a number of different 

 proteins would be dissolved together in the extracts. The 

 greater part would represent the reserve proteins of the seed ; 

 and a smaller amount would be extracted from the proto- 

 plasm of the embryonic tissues. 



