69G The Sources of the Nitrogen of our Leguminous Crops, 
nodules have a weak alkaline reaction when in apparently an 
active condition — that is whilst 'still flesh-red and glistening. 
It will be seen that the experimental results which have 
been brought forward constitute only a small proportion of 
those already obtained, or yet to be obtained, at Eothamsted; 
and it is hoped that, in the course of the further prosecution of 
the investigations which have been undertaken, more definite 
answers will be forthcoming to some of the admittedly still open 
questions in connection with this interesting and important 
subject. 
Of what Importance to Agriculture is the Newly- 
RECOGXISED SoURCE OF NiTROOEN TO LEGUMINOUS CrOPS ? 
The question yet remains : — What is the practical importance 
of the newly-recognised source of nitrogen to the Lerjuminos'Af, 
considered in its bearing on the known facts of agricultural 
production, and especially on the question of the sources of the 
nitrogen, not only of leguminous crops themselves, but of crops 
generally ? Unfortunately, as in the matter of the explanation 
of the action by which the nitrogen is fixed, there is much yet 
to learn before an adequate answer can be given. Stdl it is 
desirable to report progress. 
We have said that whilst experience, whether practical or 
experimental, did not point to an unsolved problem in the 
matter of the sources of the nitrogen of the agricultural plants 
of other families, it was quite otherwise so far as those of the 
Leguminosce were concerned. It is true, that both agricultural 
investigation, and direct vegetation experiment, have clearly 
shown that Leguminosrn do take up much soil-nitrogen, and, at 
any rate in great part, as nitrate. But it is admitted that, in 
the case of some direct experiments bearing on the point, the 
evidence was not such as to justify the conclusion that the 
whole of the nitrogen had been so derived ; and that hence 
some other explanation of the large amounts assimilated was 
needed. 
It has been seen that the balance of experimental evidence is 
against the supposition that the higher plants themselves can 
assimilate free nitrogen. But, it is now established that, at any 
rate in the case of some leguminous plants, they gain nitrogen 
coincidently with the development on their roots of tubercular 
bodies containing bacteria ; and the evidence points to the con- 
clusion that it is the lower organisms, and not the higher 
plants, that fix free nitrogen. 
It has been stated that the characteristic nodules have been 
