ABSORPTION OF NITRIC ACID — ITS EFFECT ON VEGETATION. 73 



been sought for. Were we, therefore, entitled, from the mere presence 

 of this acid in plants, to infer that it had really entered by their roots or 

 leaves, we should have no hesitation in drawing our conclusion. But, 

 like ammonia, it may have been formed in the interior of the living ve- 

 getable ;* and hence the fact of its presence proves nothing in regard to 

 the state in which the nitrogen it contains entered into the circulation of 

 the plant. 



2°. But nitric acid, like ammonia, exerts a powerful influence on the 

 growing crop, whether of corn or of grass. Animal matters, as we have 

 seen, give otf ammonia during their decay, and manures are rich and 

 efficacious in proportion to the quantity of animal manure they contain. 

 The crop produced also is valuable and rich in nitrogen in like propor- 

 tion. Therefore, as already stated, it is inferred that ammonia enters 

 directly into the living plant, and supplies it with nitrogen. 



The effect of nitric acid is similar in kind, and perhaps equal in de- 

 gree. Applied to the young grass or sprouting shoots of grain, it has- 

 tens and increases their growth, it occasions a larger produce of grain, 

 and this grain, as when ammonia is employed, is richer in gluten^ and 

 more nutritious in its quality. f An equal breadth of the same field 

 yields a heavier produce, and that produce, weiglit for weight, contains 

 more when saltpette or nitrate of soda have been applied in certain 

 quantities to the young plants which grow upon it. It is reasonable to 

 conclude, therefore, that the acid of the nitrates, in some form or other, 



* Wlien the beet-root arrives at maturity, the sugar begins to diminish, and saltpetre or 

 other nitrates to be furmed, probably at the expense of the ammonia which the juice pre- 

 viously contained.-^Decroizelles, Jour, de Phar., X., p. 42. 



t The analogous effects of ammoiiiacal manures and of the nitrates on the relative quan- 

 tities of gluten and starch in grain, are shown by the following experiments : 



Hermbstaedt sowed equal quantities of the same wheat, on equal plots of the same ground, 

 and manured them with equal weights of different manures. Then from 100 parts of each 

 sample of grain produced, he obtained starch and gluten in the following proportions: 



Gluten. Starch. Produce. 



Without manure 9-2 C6-7 3 fold. 



With vegetable manure (rotted 



potatoe haulm) 9-6 65-94 5 « 



With cow dung 120 62-3 7 " 



With pigeons' dung 12-2 632 9 " 



Witii horse dung 13 7 61-64 10 « 



With goats' dung 329 424 12 « 



With sheep dung 32-9 42-8 12 « 



With dried night-soil 33-14 4144 14 « 



With dried ox-blood 34-24 413 14 « 



With dried human urine - - - 351 39-3 12 "i 



The manures employed by Hermbstaedt are supposed, during lermentation, to evolve 

 more ammonia in the order in which they are here placed, beginning at the top of the list ; 

 while the amount and kind of the produce obtained by the use of each, afford the chief evi- 

 dence in favour of the opinion that this ammonia actually enters into and yields nitrogen to 

 the plant. 



Mr. Ilyett found in flour raised on two patches of the same land in Gloucestershire, the 

 one dressed with nitrate of soda, the other undressed, the following proportions : 



Gluten. Starch. 



In the nitrated - - - 23-25 49-5 



In the unnitrated. - - 19* 55-5 



And Mr. Daubeny, {Three Lectures on Agriculture, p. 76,] in flour from wheat top-dressed 

 with saltpetre, found — 



In the nitrated 15 per cent, of gluten. 



In the unnitrated - - - - 13 " " 



These differences are not so striking as in the case of ammonia, but they are precisely 

 the same in kind^ and lead to the same general conclusion in regard to the nature of the in- 

 fluence of the nitrates on vegetation. Accurate and repeated experiments on the precise 

 effects of the nitrates are still much to be desired. 



[' Schiibler. Grundsiitze der Agricultur Chemte, II. p. 170.] 



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