THE SOTJKCES OF THE NITROGEN OF VEGETATION, ETC. 451 



in a limited atmosphere, and supplied carbonic acid. The result was, that the plants 

 thus grown, in a limited atmosphere, but in a good soil, were even more luxuriant than 

 a parallel set, grown in a similar soil, in the open air. In both cases a large quantity 

 of seed was produced. 



3. M. Boussingault's experiments in 1854, with a current of washed air*. 



In this series of experiments, Boussingault supplied his plants with a current of air, 

 previously washed by passing first through vessels containing pumice-stone saturated 

 with sulphuric acid, and then through water. He also supplied carbonic acid from 

 bicarbonate of soda acted upon by sulphuric acid, — the gas evolved being passed first 

 over chalk, then through a solution of carbonate of soda, and lastly over pumice-stone 

 saturated with a solution of carbonate of soda. The enclosing apparatus consisted of a 

 metal-framed glass case of 124 litres capacity, which was cemented down upon a 

 polished iron plate, upon which the experimental pots were placed. Across one side of 

 the case was a metallic joint-bar, in which were apertures for the insertion of tubes for 

 the admission of the washed air, and for the supply of water and carbonic acid. On the 

 opposite side was a similar joint-bar, to an aperture iu which, a tube was attached con- 

 necting the case with an aspirator of 500 litres capacity. By this apparatus, therefore, 

 the plants could be supplied with a current of air freed from ammonia, with water, and 

 with carbonic acid, at pleasure. During the experiment, the atmosphere in the Case 

 generally contained from 2 to 3 per cent, of carbonic acid. Lastly, by means of one of 

 the apertures any withered leaves were removed as they fell from the plants ; and they 

 were then dried and preserved for analysis with the remainder of the products. 



One of the experiments made in this apparatus was with a single Lupin, which was 

 allowed to grow for two and a half months. The dry matter of the produce was more 

 than six times that of the seed. The Lupin sown was estimated to contain 0-0196 

 gramme of Nitrogen. The Nitrogen found in the products amounted to 0-0187 gramme. 

 There was a loss, therefore, of nine-tenths of a milligramme of nitrogen. 



Four experiments were made with Dwarf Haricots, in three of which single seeds, and 

 in the fourth two seeds, were sown. One experiment lasted over two and a half months, 

 and the plant flowered ; one over three months, and the plant seeded ; one over three and 

 a half months, in which case also the plant seeded ; and another over three and a quarter 

 months. The dry substance of the produced plants was from three to four times as much 

 as that of the seed sown. The total Nitrogen in the five seeds employed in the four expe- 

 riments was estimated at 0-1672 ; the Nitrogen found in the total products amounted to 

 0-1061 gramme. There was therefore, upon the whole, a loss of 0-0011 gramme of Ni- 

 trogen. In two of the experiments there was a loss of 1 milligramme each of Nitrogen ; 

 and in the other two a gain, amounting to less than 1 milligramme in each case. 



In the next experiment, one Lupin seed was sown to grow, and another was steeped 

 in hot water and applied as manure. The dry matter of the produce from the one seed 

 amounted to nearly three times that of the two seeds employed in the experiment. The 



* Ann. de Chim. et de Phys. se'r. 3. tome sliii. 1S55. 



