24 



THEORIES ON THE ABSORPTION OF NITROGEN 



The primary soil materials employed were a fine quartzose 

 sand, chemically impure and containing other material beside 

 silica. 



Sulphuric acid 



Lime 



Magnesia 



Potash 



Soda 



Phosphoric acid (only traces) 



Per cent. 

 0*0052 

 O'OOSo 

 0*0030 

 0'00I4 



o'oo67 



Only distilled water w^as used for irrigation, and the 

 first third from each distillation was removed owing to the 

 possibility of its containing traces of ammonia. Nutritive 

 solutions were then prepared with this water, and although 

 the results obtained with the Gramine^e were negative, 

 so far as nitrogen fixation was concerned, they none the 

 less furnished a striking illustration of the plant faculty of 

 absorbing mineral salts, and of the influence of these latter 

 on the growth of crops. 



Appended is a table giving the yield, in dry matter, for 

 oats and barley raised on solutions respectively rich and 

 poor in this nutritive material : — 



Barley 



Oa-is 



Seed 



Husks 



Straw 



Rich admixture Poor admixture Rich admixture Poor admixture 



I3'57i ... 12-676 ... 12-891 ... 11-499 



2015 ... 1-984 ... 1-643 ••• i"392 



12-270 ... 9051 ... 12-119 ... 11-103 



27-856 



23-711 



26-653 



23 '994 



Percentage of crude ash 



Percentage ok pure ash 



The greater part of the mineral matter is seen to accumu- 

 late in the straw. 



As we have already mentioned, the irregularities occur- 

 ring in the previous experiments led Hellriegel to believe 



