THE SDUECES OF THE XETBOGEX OF VEGETATION, ETC. 449 



came from the atmosphere, might be partly due to titrate of Ammonia produced by 

 electrical action and brought down by ram. 



2. M. Bousslxgault's experiments in 1851, 1852, and 1853, in which the plants were 



confined in limited volumes of air*. 



BoussiN'GAi'LT resumed the subject of the sources of the Nitrogen of vegetation in 

 1851. His object was, apparently, to settle more definitely, whether plants assimilated 

 Nitrogen from any other source than the combined forms of it. 



In his experiments inlSol and 1852, Boussixgault confined his experimental plants 

 under a glass shade of about 35 litres capacity, which shut off the free access of external 

 air by resting in a lute of sulphuric acid. Tubes passed under the shade for the supply 

 of carbonic acid, and water, as they might be needed. Pumice-stone, coarsely powdered, 

 washed, ignited, and cooled over sulphuric acid, served as soil. To this, at the com- 

 mencement, some of the ash from farm-yard manure, and also from seed of the kind to 

 be sown, was added. 



In 1851, a Haricot was grown under these conditions, the seed of which, when sown, 

 was estimated to contain 0-0349 gramme of Nitrogen. After two months of growth, 

 flowers being formed, the dry substance of the plant was more than double that of the 

 seed sown; and the total products yielded only 0-0340 gramme of Nitrogen. There 

 was, therefore, apparently a slight loss of Nitrogen, which amounted, however, to less 

 than a milligramme. In 1852, two Haricots, sown respectively in separate pots, con- 

 tained, together, 0-0155 gramme Nitrogen. They were each allowed to grow for three 

 months, during which time the dry substance was nearly doubled ; and in one instance 

 open flowers were formed. The products of both experiments taken together yielded 

 to analysis only 0-0115 gramme of Nitrogen. There was an apparent loss, therefore, in 

 the two experiments, of 4 milligrammes of Nitrogen. It is seen, then, that in these new 

 experiments with Leguminous plants, hi which the free circulation of atmospheric air 

 was not permitted, there was not the apparent gain of Nitrogen that had been met with 

 in Boussixgault's early experiments (in 1837 and 1S38), in which free access of air into 

 the enclosing apparatus was allowed. 



In 1851, ten seeds of Oats, and in 1852 four, were experimented upon in a similar 

 manner. In both cases there was an apparent very slight loss of Nitrogen. In the first 

 case the Oats vegetated for two months, and hi the second for 2 J months; and in the 

 latter, the plant arrived at the point of shooting forth the ear. 



In 1853, the apparatus adopted by Boussixgatlt consisted of a large globe, or carboy, 

 of white glass, having a capacity of 70 or SO litres. At the bottom of this vessel, a 

 matrix of pumice-stone (or burnt brick) and ashes, prepared as in the last series, was 

 placed to serve as soil. This was watered with distilled water, and then the seeds were 

 sown. The neck of the vessel was then closed with a cork, through a perforation in 

 which, a flask of carbonic acid was inverted, whose aperture, opening into the globe, was 



* Ann. dc Cliim. et de Phys. se'r. 3. tome xli. 185i. 



3 Q 2 



