454 MR. J. B. LAJWES, DB. GILBEBT, AND DB. PUOH OS 



washed, in which they grew. In no case among those experiment! iii which the 

 modern refinement! of analysis were had recourse to <li<l he find, cither with Legumi- 

 nous or with other plants, such a gain of Nitrogen beyond that supplied in the seed, as 

 couhl load to the conclusion that the free or oncombined Nitrogen of the atmosph 



had been assimilated. In many of the instances the plants, yielded not only flowers hut 

 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, Beeds whi 

 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 amoimt 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 — Boussixgault 

 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. Boussixgault's experiments in which lie supplied combined Nitrogen 

 in the form of Nitrate of Potash, or Soda*. 



In 1855 Boussixgault made one experiment with Ilelianthus in which he supplied 

 no 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 hi 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. Boussixgault concluded that the 

 gain of Nitrogen was to be attributed to the Nitrogen of the Nitrate. 



Lastly in regard to Boussixgault's experiments : In 1858f he resumed the question of 

 the action of Nitrates upon vegetation. He grew two separate pots of Ilelianthus, 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 0-0111 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. Boussixgault found, however, that there remained 

 * Ann. dc Ckim. et de Phys. scr. 3. tome xlvi. 1856. t Cornpt. Bend, tome xlvii. 1S5S. 



