500 M. G. Ville on the influence of Nitrates on Vegetation. 



obtained up to the present time seem to show that a cubic metre 

 of the same water contains from 6 to 7 grms. of nitre, cori'e- 

 sponding to I'] grm. of ammonia. 



Although river- and spring-water contain more nitrates than 

 ammonia, the contrary is the case with rain-water, snow and dew. 

 Boussingault^s experiments on a large number of specimens of 

 rain-water collected in the middle of a field in the neighbour- 

 hood of extensive forests, yielded much less of nitrates than 

 ammonia. 



Pelouze showed that nitre slowly disappears in a solution of 

 white of egg, and the acid is changed into ammonia. This ex- 

 plains why only traces of nitrates are found in liquid ammonia. 

 According to Boussingault, mere traces of nitre are found at the 

 top of dung-heaps, and none at all at the bottom. 



M. Georges Ville has published* a continuation of his re- 

 searches on the influence of nitrates on vegetation. The first 

 part was devoted to a description of a new method of detei'mi- 

 ning nitrates t- 



In the second part he details his experiments on seeds and plants 

 grown in sand, to which mineral salts and nitre had been added. 

 His results confirm in general those of Boussingault. He finds 

 that nitre acts by its nitrogen, and that it is absorbed as nitre; 

 that the quantity of nitrogen being equal, nitre acts more ener- 

 getically than ammoniacal salts. 



Ville sowed seeds in calcined sand to which half a gramme 

 of nitre had been added. The seeds germinated and grew, but 

 a period ari'ived at which the development of the plant was 

 arrested ; and it was found on stopping the experiment there, 

 that the quantity of nitrogen in the produce was exactly equal 

 to the nitrogen of the seed and of the nitre added. But if, 

 instead of adding half a gramme of nitre, a gramme was added, the 

 results were different : the vegetation continued, and at the expira- 

 tion of two and a half months the produce contained much more 

 nitrogen than was originally contained in the seeds and the nitre 

 used. This difference arises from the fact, that in the latter case 

 the free nitrogen of the atmosphere had been assimilated. Plants 

 only begin to assimilate this nitrogen at a certain stage of their 

 development ; that with the nitrogen from the smaller quan- 

 tity of nitre this stage had not been reached. To obtain vege- 

 tation in calcined sand, the plant must have passed the embry- 

 onic stage ; and it is immaterial whether it finds the means in 

 the soil itself or in an external manure. However these experi- 

 ments were varied, Ville could never detect the formation of a 



* Annales de Chimie et de Physique, February 1857. 

 t Phil. Mag. June 1856. 



