166 THE YEAR-BOOK OF AGRICULTURE. 



there are three times too much of organized silica for corn, and forty for that of cotton. In 

 the one hundred pounds of oak-leaves, there is only a sufficiency of the same element for the 

 corn, but eleven times more than is needed for the cotton. Of sulphate of potash and the 

 chlorides, the one hundred pounds of leaves of either kind will supply all that is demanded 

 by either crop, in like quantity. 



k 



On the Absorption of Nitrogen by Plants. 



A DEBATE of great interest has been entered into in the French Academy between the cele- 

 brated agricultural chemist, M. Boussingault, and M. Ville, respecting the absorption of ni- 

 trogen by plants, which has been conducted with unusual interest and some acrimony. 



The question discussed by these gentlemen was this : May we ascertain whether or not vege- 

 tables possess the faculty of directly absorbing to their advantage a portion of this gaseous 

 azote which forms the greatest part of the atmosphere ? The importance of the question is 

 evident : if the free and gaseous azote may directly enter into vegetable organisms without 

 passing through some intermediate combination, the veritable source of agricultural wealth is 

 in the atmosphere ; if, on the contrary, before the azote commingles with the plant, it must 

 unite itself to some other element, the agricultural chemist must turn his attention to the 

 search of some new and better method of favoring the slow and difficult formation of combi- 

 nations of azote. In both of the hypotheses the importance of manure remains incontestable, 

 but their functions will not be so important. If azote gas is not capable of assimilation, if it 

 is simply destined to temper the action of the oxygen with which it is mixed in the air, it 

 is evident how important organic matters are in manures, bringing as they do the elements 

 of the azotic principles elaborated by the plants. If, on the contrary, the azote of air is ab- 

 sorbed during the act of vegetation, if it becomes in this way an integral part of the vege- 

 table, then the mineral substances of manures contain the greatest part of their fertilizing pro- 

 perties ; for the azote element would have been abundantly furnished by the atmospheric air. 

 Why, then, has the chemist not yet determined this important point, whether gaseous azote is 

 or is not directly assimilated by plants. The great obstacle lies in the difficulties of making 

 the experiment, which should resolve the question. When the chemist would place a plant 

 under a definitive regimen, to ascertain what it obtains from the mineral kingdom, whence it 

 extracts a portion of its aliment, it is indispensable to measure, to weigh, to analyze every 

 thing the air it respires, the water which moistens it, the soil which upholds. M. Boussin- 

 gault and M. Ville use different methods, of which they are tenacious. It cannot be denied 

 that M. Boussingault exhibits a great deal of art in the process he used in his experiments. 

 He first abandoned the ridiculous pretension commonly entertained before him of measur- 

 ing by default the azote a plant would have absorbed while it lived during a certain time in a 

 limited quantity of air. He substituted in its stead, raising the plants in a completely sterile 

 soil, and comparing the composition of the seed and the composition of the small crops so ob- 

 tained at the expense of air and water alone. A handful of earth previously calcined, and 

 watered with distilled water, evidently can furnish no organic matter to the plant which is 

 developed there ; and consequently, if, after the crop is gathered, the chemical analysis shows 

 it contains more azote than the grains sown contained, it is manifest that this azote came by 

 the air : this result M. Boussingault obtained by experimenting with the seed of clover and 

 of peas. 



But in communicating this result to the world, M. Boussingault did not pretend to do more 

 than to exhibit the bare fact. He made no deduction to demonstrate that it came by the air 

 in its normal state, or by the rare ammoniacal vapors from which the atmosphere is never ex- 

 empt. M. Ville did not imitate his silence. He studied the question, and found the azote of 

 the crops was ten, twenty, thirty times greater than the azote of the seed. However, M. 

 Boussingault, pursuing his researches, (using a different method,) attained diametrically op- 

 posite results, or results which are completely negative. To avoid any objection which might 

 be urged on the ground of the permanent communication of the apparatus with the external 

 air, he planted the objects of his experiments in a completely closed vase, and furnished them 

 in the beginning with the quantity of carbonic acid and of water necessary to their alimenta- 



