4G8 MB. J. B. LAWEB, DR. GILBERT, LOT) DR FUOH ON 



differences of plan adopted bj ML. Boussingault and MLG.ViLije, so fur a^ the] have 

 themselves described them, or in the results and explanations ofothi 

 any satisfactorj solution of the difference of resuli arrived at. A priori, there ar< 

 for concluding, both from the chemical characters of Nitrogi a itself, and from whai m 

 at present know of the chemistry of vegetation in other respects, that plants would ool 

 assimilate Nitrogen offered to them in the free state. On the other hand — to say 

 nothing of the large total amount of combined Nitrogen actually existing — the sta- 

 tistics of Nitrogen-production show that there is an amount of Nitrogen periodically 

 available for the vegetation of a given area of land, the source of a considerable propor- 

 tion of which is as yet not satisfactorily explained. The question whether or not the 

 assimilation of free Nitrogen by plants may account for all, or a part, of the otherwise 

 unexplained fixation, is seen to be left in a dilemma almost inexplicable, by the conflict- 

 ing character of the results that have been recorded relating to it. Yet, as has been 

 already said, upon the decision finally come to in regard to this question, must materially 

 depend the degree of importance to be attached to the investigation of the other actual 

 or possible sources of Nitrogen to plants, which we have briefly noticed. Under these 

 circumstances, it seemed desirable that any opinions we might offer or adopt on tins 

 subject should have the support of such evidence as might be afforded by renewed expe- 

 riment. We proceed, then, to follow up our account of the Nitrogen-statistics of vege- 

 table production, the consideration of the several possible sources of Nitrogen to plants, 

 and the review of the results and opinions of others on some of the points at issue, by a 

 statement of our own experimental evidence in regard to this important question. 



PART SECOND. 



EXPERIMENTAL RESULTS OBTAINED AT EOTHAMSTED DURING THE 



TEARS 1857, 1858, AND 1859. 



Introductory observations. 

 In laying this part of the subject before the Fellows of the Royal Society, we shall 

 follow the general order in which the questions involved were presented to ourselves in 

 the investigation. In so doing it will be necessary : — 



1. To consider all possible conditions to be fulfilled in order to effect the solution of 

 the main question of the assimilation of free Nitrogen by plants, and to endeavour to 

 eliminate all sources of error in our investigation. 



2. To examine a number of collateral questions, which have a bearing upon the points 

 at issue, and to endeavour so far to solve them as to reduce the general solution to that 

 of a single question to be answered by a final set of experiments. 



3. To give the results of the final experiments themselves, and to discuss their bear- 

 ings upon the question which it is proposed to solve by them. 



