EFFECTS OF NITKIC ACID UPON VEGETATION. 91 



the ammonia, contained in such manures enters into the- 

 substance of plants and yields up nitrogen to them, it must 

 also be considered that a portion of the nitrogen contained 

 in plants and procured from decaying animal substances, 

 may be obtained from other compounds of it than ammonia,, 

 and in which ammonia may not exist. 



Nitric acid is invariably present in the juices of plants 

 in combination with potash, soda, lime, and magnesia. 

 Therefore all the evidence afforded by the facts above noted 

 are also applicable to the belief that this acid is one of the 

 sources, at least, from w r hence the nitrogen of plants is de- 

 rived. This acid has been detected in tobacco, and the sun- 

 flower, and in the grain of barley in the form of nitrate of 

 soda. If we were therefore to infer from these facts that 

 this acid really enters the roots of plants we might draw a 

 certain conclusion. Like other compounds of nitrogen, it 

 may have been formed in the interior of plants during the 

 many changes there effected, and hence its presence proves 

 no more in regard to a solution of the question at issue than 

 the presence of ammonia. The same uncertainty would 

 still exist. 



But the most recent investigations go to show that of 

 all the forms in which nitrogen enters into plants, nitric 

 acid is the most probable one. It exerts a powerful in- 

 fluence upon growing crops of grass and grains. It changes 

 the color of the leaves to an intense green in a short time ; 

 and largely increases the quantity of nitrogenous matter in 

 grain, as well as the yield of the crop. For instance it has 

 been found that a dressing of nitrate of soda has increased 

 the amount of gluten in wheat from 19 to 23? per cent, 

 reducing the starch from 55 J to 49 ^ per cent. Many other 

 similar instances are recorded, all tending to show the fav- 

 orable effect of nitric acid upon the growth of vegetation. 

 Heretofore a still more striking instance has been given of 

 similar results from the use of manures rich in ammonia. 

 But recent researches of the leading investigators espec- 

 ially those at the Rothampstead farm in England under 

 the supervision of Sir J. B. Lawes, aided by a most efficient 



