44G ME. J. B. LAWKs, DE. GILBERT, AMD DB. FUGH ON 



A bean and a wheat crop may yield equal amounts of dry matter pel acre, whilst the \y 

 produce would contain from two to three times as mueh Nitrogen as the- wheat. Never- 

 theless some attempts at approximate measurement have indicated that the wheat-plant 

 offers a greater external superficies in relation to a given weight of dry substance, than 



does the bean. The wheat-plant would, of course, show a still higher relation of sup • 

 ficies to a given amount of Nitrogen fixed. If, then lore, the larger amount of Nitro- 

 gen yielded per acre hy a bean than by a wheat crop be due to a lai. a of 

 it directly from atmospheric sources in some form, it is obvious that the result must he- 

 due to character, and function, and not to mere extent of surface above ground In 

 connexion with this point it may be observed, more particularly with reference to the 

 crops that are grown for their ripened seed, that the Leguminous on< g< n< rally main- 

 tain their green and succulent surface in relation to a more extended period of the 

 season of active growth and accumulation than do the Graminaceous ones. 



(7) Assimilation of free or uncombined Nitrogen hy Plants. — It has been seen, in the 

 course of the foregoing brief review of the various sources of combined Nitrogen to 

 plants, that those of them which have as yet been quantitatively estimated are inade- 

 quate to account for the amounts of Nitrogen obtained in the annual produce of a given 

 area of land beyond that which may be attributable to the supplies by previous manuring. 

 It must be admitted, too, that the sources of combined Nitrogen which have been alluded 

 to as not yet even approximately estimated in a quantitative sense (if indeed they arc all 

 fully established qualitatively) offer many practical difficulties in the way of any such 

 investigation of them as would afford results directly applicable to our present purpose. 

 It appeared, therefore, that it would be desirable to settle the question, whether or 

 not that vast storehouse of Nitrogen, the atmosphere, in which the vegetation which 

 covers the Earth's surface is seen to live and flourish, be of any measurable avail to the 

 growing plant, so far as its free or uncombined Nitrogen is concerned. 



The settlement of this question (whether affirmatively or negatively) would at any 

 rate indicate the degree of importance to be attached to the remaining open points of 

 inquiry. Indeed, were it found that plants generally, or some of those we cultivate 

 more than others, were able to fix Nitrogen from that presented to them in the free or 

 uncombined form, we should, in this fact, have a clue to the explanation of much that 

 is yet clouded in obscurity in connexion with the chemical phenomena of Agricultural 

 production. We should establish for vegetation, the attribute of effecting chemical 

 combinations with an element at once the most reluctant to associate itself with other 

 bodies in obedience to laboratory processes and at the same time apt to rid itself of 

 connexions once formed in the most violent manner — as the explosive character of main- 

 Nitrogen compounds forcibly illustrates. We should further be able, much more satis- 

 factorily than we are at present, to account — by processes established to be going on 

 under our own observation — for the actually large total amount of combined Nitrogen 

 which we know to exist and to circulate, in land and water, in animal and vegetable 

 life, and in the atmosphere. 



