840 



THE ROLE OF NITROGEN, ETC., II. 



the total nitrogen in the seeds. Now on making a rough extrac- 

 tion of Acacia seeds with dilute salt solution and precipitating 

 the proteins, the nitrogen in the nitrate represented over 50 % of 

 the total. This very large figure led to further investigation, and 

 varying results were obtained according to the degree of fineness 

 of the meal when ground. This is probably to be accounted for 

 partly by the different amounts of spermoderm or skin which are 

 included in the samples after passing through different sizes of 

 sieves. It was decided to keep the outer skins on all the seeds. 

 First, because in many it was almost wholly impossible to remove 

 the skins completely; and second, since the latter are rich in both 

 soluble carbohydrates and soluble nitrogen-compounds, it seems 

 quite possible that these take a share in the supply of nutriment 

 during germination. The skins may therefore be looked upon, 

 from the chemical point of view, as an essential part of the seed- 

 sample. 



That the method of preparing the sample makes a considerable 

 difference in the result the following table shows, 



(a) Acacia seeds ground and passed through 15 mm. sieve. 



(b) Acacia seeds ground and passed through 05 mm. sieve. 



(c) Acacia seeds, skins entirely removed, ground and passed 

 through 0-5 mm. sieve. 





(a) 



coarse 



whole seed. 



(b) 



fine 



whole seed. 



(?) 





cotyledons only. 



Total N in seeds 



N not pptd. by alcohol .. 

 =% of total N 



4-09% 

 1 63 



40-00 



5-04% 

 1-70 

 33-75 



5-52% 

 1-71 

 31-00 







Now it is observed from these that the non-protein nitrogen is 

 the same in each, but the total nitrogen of the seed varies with 

 the treatment. 



It was further observed that in making an aqueous extract of 

 the seeds considerably more nitrogenous material was dissolved 

 by standing in the cold for twelve hours, than when boiled and 

 filtered a number of times in succession. 



