BULLETIN OF THE BUSSEY INSTITUTION. 285 
there are so many influences working to impair the nicety of the 
_ results that it would be extremely difficult, if not impossible, to 
attain that high degree of accuracy which would be needful for the 
case in point. I have consequently been forced to abandon this 
line of enquiry. 
It should be said that there is good reason to believe that the 
diversity of results just now spoken of may depend for the most 
part upon a greater or less degree of activity in the process of 
nitrification in the contents of the several jars. That is to say, the 
organism or ferment,* upon whose presence nitrification depends, 
may have been better suited by the conditions of the earth in 
one jar than in another, and have prospered or languished ac- 
cordingly. 
It is manifest that in carrying out experiments of this sort the 
purely chemical part of the enquiry becomes complicated with the 
question how best to care for the ferment organism, and how to 
contro! its growth so that it shall be equal in all cases or, at the 
least, comparable. Indeed, one the first things now to be done in 
seeking to explain the agricultural value of the nitrogen in vege- 
table-mould is to determine precisely what the ferment organism is, 
and to study its habits and the history of its development. When 
this knowledge has been gained, it will doubtless be practicable 
for the farmer to employ the soil-nitrogen in a much more intelli- 
gent way than has been customary hitherto. He will then be able 
to count definitely upon the soil-nitrogen as a resource in a sense 
that was hardly to be thought of by his predecessors. 
Many methods of tillage and of manuring, and some modes of 
mulching, —the conduct of which is now purely empirical, — and the 
whole subject of composts made with peat and loam, will undoubt- 
edly then be brought into the domain of reasonable practice. For 
example, the question is now open whether the well-known power 
of clover and root-crops to supply themselves with nitrogen may 
not really depend upon the comfort and shelter these crops offer 
to the nitrifying ferment. It is not unlikely that the ferment organ- 
ism may prosper exceedingly beneath the dense shade of clover 
and other large-leaved plants, in the comparatively moist surface- 
soil which is peculiar to such fields. Perhaps even the manner in 
which the roots of these plants act upon the soil may have a favor- 
able influence upon the life of the ferment? There is an old ex- 
* See ‘‘American Journal of Science,” April and June, 1878, 15. pp. 
310, 444. 
