112 



Sir J. B. Lawes and Prof. J. H. Gilbert. 



Provided this were clearly established to be the case, the question 

 would still remain, whether the complex nitrogenous body is merely 

 rendered soluble, and taken up as such, as is probably the case with 

 the fungi, or whether, after being attacked, it is subjected to further 

 change before entering the plant ? 



In the autumn of 1885, Dr. G. Loges published the results of 

 experiments in which he acted upon soils by pretty strong hydro- 

 chloric acid, and determined the amount of nitrogen taken up 

 ( s Yersuchs- Stationen,' vol. 32, p. 201). One of his soils contained 0*804, 

 and the other 0*367 per cent, of nitrogen; whilst the surface soil of 

 the lucerne plot at Rothainsted contained only about 0*122, and the 

 subsoil, which is assumed to have yielded large quantities of nitrogen 

 to the crops, little more than 0*04 per cent. Again, in the one case, 

 Loges found 40 per cent., and in the other 22*6 per cent., of the 

 total nitrogen taken up. It is obvious, therefore, that such an action 

 is not directly comparable with that of root-sap on a poor subsoil. 



Loges states that in experimenting with a great variety of soils lie 

 has always found the hydrochloric acid extract gave the phospho- 

 tungstic precipitate, from which it is concluded that the substance 

 taken up is an amide or peptone body. 



Still more recently, MM. Berthelot and Andre (' Compt. Rend.,' vol. 

 103, 1886, p. 1101) have published the results of experiments to de- 

 termine the character of the insoluble nitrogenous compounds in soils, 

 and of the changes they undergo when acted upon by hydrochloric acid 

 of various strengths, for shorter or longer periods, and at different 

 temperatures. They found the nitrogen in the extract existed partly 

 as ammonia, but in much larger proportion as soluble amides, and 

 that the amounts obtained for both increased with the strength of acid, 

 the time of contact, and the temperature. They also call attention to 

 the fact that when the clear filtered acid extract is exactly neutralised 

 by potash, one portion of the amide still remains soluble, whilst 

 another is precipitated, showing that the amides rendered soluble 

 constitute two groups. Such re-precipitation is quite in accordance 

 with the* results obtained in our own experiments, in which less 

 nitrogen remained dissolved after twenty -four hours, than after only 

 one hour's contact, when, w r ith the longer period, the acidity of the 

 extract became neutralised. 



As in Loges' experiments, so in those of MM. Berthelot and Andre, 

 the strength of acid used was in all cases much greater than in that 

 of the Rothamsted experiments, and very much greater than is likely 

 to occur in any root-sap. Further, the soil they operated upon was 

 about four times as rich in nitrogen as the Rothamsted subsoils, whilst, 

 with the strongest acid, and a temperature of 100° C, about one- 

 fourth of the total nitrogen of the soil was dissolved. 



Still, the results of Loges, and of Berthelot and Andre, are of much 



