THE SOTJECES OF THE NITBOGEN OF VEGETATION, ETC. 467 



H. — M. A. Petzholdt on the Source of the Nitrogen of Plants*. 



In the years 1852 and 1853, M. H. M. Chlebodarow made some experiments on the 

 subject of the assimilation of Nitrogen by plants, at Dorpat, under the direction of 

 M. Petzholdt, who has reported the results of the inquiry. 



M. Petzholdt assumes that if plants can appropriate the free Nitrogen of the ah*, 

 they will not need ammonia ; and that if they take Nitrogen from ammonia, the arti- 

 ficial supply of the latter will increase growth. 



The experiments were made upon Barley. In 1852, an ignited yellow sand was taken 

 as the soil. To one set of plants, no ammonia was supplied ; to a second, carbonate of 

 ammonia was provided in the soil ; and to a third, carbonate of ammonia was supplied 

 in the air. Both the crops with an artificial supply of ammonia gave three times as 

 much produce as the crops without such supply. The Nitrogen in the produce was 

 also very much greater, both in percentage, and in actual amount, where the ammonia 

 was used. 



In 1853, six sets of experiments were made, and as before, with Barley. The soils con- 

 sisted of an artificial mixture of clay, sand, and felspar, decomposed by heating with 

 lime. The first set of three pots was provided with this soil alone ; the second had, 

 in addition, 0T3 per cent, of bone-ash acted upon by sulphuric acid; and the third had 

 1-33 per cent., or ten times as much, of the same phosphatic manure. The three other 

 sets were, respectively, so far like the three just described, but in addition ammonia 

 was artificially supplied to the atmosphere in which the plants grew. The phosphatic 

 manure, whether with or without the ammoniacal supply, much increased the produce 

 of both corn and straw. The Nitrogen of the crops was also very much increased in 

 actual amount (though diminished in percentage in the dry substance) by the aid of 

 the phosphatic manure ; and the actual amount of Nitrogen was still further increased 

 by the addition of ammonia to the atmosphere of the plants ; and the percentage of 

 Nitrogen in the dry substance was also greater where the ammonia was supplied, than 

 in the corresponding cases without it. The experiments without ammonia were made 

 in free air. The Nitrogen in the produce was about seven times that of the seeds where 

 no phosphates were employed ; about twelve times that of the seed witn the smaller 

 quantity of phosphate ; and about twenty times that of the seed with the larger amount 

 of phosphate. 



M. Petzholdt considered it difficult to account for the fact of M. Boussingault get- 

 ting little or no increase of Nitrogen when he grew plants in free air, which must have 

 supplied some ammonia, even though rain and dew were excluded. He thinks the error 

 must be on the side of M. Boussingault. 



It is seen that the explanations or conclusions of these several arbitrators are nearly 

 as conflicting as those of M. Boussingault and M. G. Ville themselves. 



For ourselves we are free to confess that we are unable to discover, either in the 



* Journ. fur Prakt. Ckein. Band lxv. 



