THE SOURCES OF THE NITKOGEN OF VEGETATION, ETC. 621 



the Graminacea? and the Leguminosse, which, in some points of view, appear to differ 

 so widely in their demands upon combined Nitrogen provided within the soil. 



4. To take such as had already been experimented upon, with such conflicting results, 

 by M. Boussingadlt and M. G. Ville. 



We shall first consider the results obtained with plants grown without any other 

 supply of combined Nitrogen than that contained in the seed sown. 



I- — Experiments in which the plants had no other supply of combined Nitrogen than 



that contained in the seed soivn. 



The following Table (XII.) gives, at one view, a summary of the numerical results 

 obtained under this head; see also figs. 1-6, Plate XV., which are reduced from careful 

 drawings taken of six out of the nine Graminacese experimented upon, and illustrate 

 the character and extent of growth attained under the conditions in question. 



After the full discussion in the foregoing pages of the circumstances under which the 

 results recorded in the Table just given were obtained, but little need be said in pointing 

 out their bearings upon the question at issue. The column showing the gain or loss in 

 each experiment speaks for itself. In judging of the results of the experiments of 

 1857, the remarks made in discussing the results of Table XIV. (p. 532), with regard 

 to the slates used as lute-vessels in that year, must be taken into consideration. The 

 source of error referred to being obviated in the experiments of 1858, the results of 1857 

 acquire a greater value, as confirming those of the latter year, than, standing alone, they 

 would possess. 



The difference between the results obtained with soil and with pumice as matrix, in 

 1857, are not such as to lead us to attach any importance to them, or to attribute them 

 in any way to the difference of matrix in question. The two experiments may there- 

 fore simply be considered as duplicates. Indeed, the character of the results in the one 

 experiment with Wheat, and in the two with Barley, in 1857, was so similar, that the 

 three experiments may be considered as triplicates. 



Graminaceous Plants. 



It will be observed that the largest gain of Nitrogen in the three experiments with 

 Graminaceae in 1857 was 0-0026 gramme. Keeping in view the probable source of 

 error due to the use of slates in that year, and the difference of result in 1858 when 

 slates were not employed, and, again, considering the fact that so small an amount of 

 Nitrogen had to be determined in such a large amount of soil (0-003 gramme or less of 

 Nitrogen in about 1500 grammes of soil), it seems indeed more than questionable whether 

 the gain should not be attributed to the errors of experiment or analysis alluded to. In 

 fact, we can but conclude that, under the circumstances of growth of the Graminaceous 

 plants to which Table XII. relates, there has been no assimilation of free Nitrogen. 



It should also be noticed that, even when a gain of Nitrogen in the total products is 

 observed, there is, in no case, more Nitrogen in the plant itself than in the original 



4b2 



