224 NITROGEN OF THE AIR IN VEGETATION. 



greater than the quantity contained in the manure. This excels 

 arises doubtless from the air, and it is more than probable that, 

 in this case, a part of the excess of nitrogen is taken up in the 

 form of nitrate of ammonia, which M. Liebig has shown to exist 

 as a frequent constituent of the rain of thunder-storms. But 

 before this can be assumed, it will be necessary to examine the 

 action of this salt on vegetation." 



In a later treatise on this subject, Boussingault says (Annales 

 de Chimie et de Physique, 3 Serie, t. I., p. 240) : — 



" When these tables are examined, it follows that the nitrogen 

 in the plants obtained amounts to more than that present in the 

 manure. I assume, as a general proposition, that this excess 

 arises from the air. But in what way and manne" ~ t ::s ele- 

 ment IS TAKEN UP BY PLANTS, I AM UNABLE TO STATE. The 



nitrogen may be taken up directly as a gas, or dissolved in water, 

 or, what is possible, and as some philosophers (Saussure for ex- 

 ample) believe, the air may contain an infinitely small quantity 

 of ammonia." 



The experiments of Boussingault are, therefore, proofs that 

 the nitrogen of cultivated plants is not obtained from manure 

 alone, but that, besides this, they contain an excess which can 

 only be derived from the atmosphere. That the nitrogen of wild 

 plants must be derived from the air is so obvious, that it requires 

 neither proof nor experiments. 



Boussingault had not the slightest intention of making his ex- 

 periments the foundation for the opinion that the nitrogen of air 

 might be converted into parts of the plant, but only employed 

 them as proofs that the nitrogen of cultivated plants is derived 

 from the atmosphere. 



