454 MR. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
washed, in which they grew. In no case among those experiments in which the 
modern refinements of analysis were had recourse to did he find, either with Legumi- 
nous or with other plants, such a gain of Nitrogen beyond that supplied in the seed, as 
could lead to the conclusion that the free or uncombined Nitrogen of the atmosphere 
had been assimilated. In many of the instances the plants yielded not only flowers but 
seed; and hence it might be concluded that the conditions provided were adequate for 
the performance, by the plant, of the complete course of its natural functions of growth. 
Still it might be objected that the vigour of growth was somewhat limited, and that, 
under these circumstances, the plant might well refuse to perform the, perhaps, difficult 
office of assimilating a very refractory elementary body. In a few instances, seeds whose 
germinating power had been destroyed were supplied as manure. In these cases the 
amount of Nitrogen assimilated by the plants was much greater than that contained in 
the living seed sown ; and the luxuriance of growth was consequently comparatively great. 
Nevertheless, instead of a gain, there was generally a loss in the total amount of com- 
bined Nitrogen, which was considered to be due to the evolution of free Nitrogen by the 
decomposing manurial matter. To get increased vigour of growth—to avoid, if possible, 
a loss of Nitrogen such as is above supposed—and, at the same time, to determine whe- 
ther or not the Nitrogen of Nitrates were really assimilable by plants—BovussinGavuLt 
has latterly made some experiments in which Nitrates were employed as manure, a brief 
notice of the results of which should be here given. 
6. M. Boussincavut’s experiments in which he supplied combined Nitrogen 
in the form of Nitrate of Potash, or Soda*. 
In 1855 Boussincautt made one experiment with Helianthus in which he supplied 
ho nitrate to the soil, and another in which a small known quantity of Nitrate of Potash 
was employed. In a third experiment Cress was grown in a manured soil, in a fourth 
in a soil destitute of combined Nitrogen, and in a fifth in a soil to which a known quan- 
tity of Nitrate of Soda was added. In the case of the manured soil, and in the two 
cases where Nitrate was employed, there was a very considerable increase in the assimi- 
lation of carbon; and there was also much more Nitrogen assimilated than was supplied 
in the seeds sown. The increased assimilation of Nitrogen where Nitrate was used, did 
not, however, exceed that supplied in the manure. Bovussincautt concluded that the 
gain of Nitrogen was to be attributed to the Nitrogen of the Nitrate. 
Lastly in regard to BovssinGauLt’s experiments: In 1858+ he resumed the question of 
the action of Nitrates upon vegetation. He grew two separate pots of Helianthus, two 
seeds being sown in each pot. The soils were composed of sand and quartz well washed 
‘from saline matter and ignited. To one pot Nitrate of Potash containing 0-011] gramme 
of Nitrogen, and to the other Nitrate containing 0:0222 gramme Nitrogen, was added. 
In the first case, he did not get back, in the plant, soil, and pot, the Nitrogen of the 
seed and Nitrate by 0:0014 gramme. In the second experiment the loss of Nitrogen 
amounted to just 1 milligramme. Bovssineavtr found, however, that there remained 
* Ann, de Chim. et de Phys. sér. 8. tome xlvi. 1856. + Compt. Rend. tome slvii. 1858. 
