92 
SIR J. B. LAWES AND PROFESSOR J. H. GILBERT ON THE 
It is obvious/therefore, that such an action is not directly comparable with that of 
root-sap on a poor subsoil. Loges concluded however that the substance taken up is 
an amide or peptone body, 
MM. Berthelot and Andre have also published the results of experiments to 
determine the character of the insoluble nitrogenous compounds in soils, and of the 
changes they undergo when acted upon by hydrochloric acid. They found the nitrogen 
in the extract existed partly as ammonia, but in much larger proportion as soluble 
amides, and that the amounts obtained of both, increased with the strength of the acid, 
the time of contact, and the temperature. They also found 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 24 hours’ than after only 1 hour’s contact, when, with the longer period, the 
acidity of the extract became neutralised. 
In the experiments of Berthelot and Andr^, as in those of Loges, the strength 
of acid used was much greater than in the Rothamsted experiments, and very much 
greater than is likely to occur in any root-sap. Further, the soil they operated upon 
was about 4 times as rich in nitrogen as the Rothamsted subsoils, and with the 
strongest acid, and a temperature of 100° C., nearly one-third of the total nitrogen of 
the soil was dissolved. 
Still, the results of Loges, and of Berthelot and Andre, are of much interest as 
confirming the supposition that the insoluble nitrogenous compounds in soils are, or 
yield, amide bodies, and as indicating the changes to which they are subject when acted 
upon by acids. Supposing, however, the acid root-sap so to act on the insoluble organic 
nitrogen of the soil, and especially of the subsoil, the question still remains, whether 
the amide rendered soluble is taken up as such, or undergoes further change before 
serving as food for the plant ? It is seen that ammonia is an essential result of the 
reaction ; and the further question arises, therefore, whether the liberated ammonia is 
taken up as sach, or is first oxidated into nitric acid ? Then, again, is the soluble 
amide subjected to further change, perhaps first yielding ammonia, and this again 
nitric acid ? On this supjiosition we are again met with the difiiculty as to the 
sufficient aeration of the subsoil. 
Independently of much other evidence, our own direct experiments have shown it 
to be probable, if not certain, that fungi can utilise both the organic carbon and the 
organic nitrogen of the soil; though they seem to develop the more freely when the 
humic matters have not undergone the final stages of change by which the compound 
of so low a proportion of carbon to nitrogen as is found in raw subsoils, has been pro¬ 
duced. As bearing on the question whether amides, rendered soluble within the soil, 
may be taken up as such by chlorophyllous plants the results of various experiments 
