190 EXPERIMENTS WITH CARBONATE OF AMMONIA, 



supposed to be formed there, and to be afterwards earned up to 

 the other parts of the plant by the ascending sap. Ammonia, 

 and especially when it enters in combination with humic acid, 

 is peculiarly adapted to the production of these compounds,* 

 and hence, probably, one reason why its action upon growing 

 plants is in many cases so immediate and striking. 



b Among the intelligible chemical uses of ammonia in the sap, 

 I may mention that, when it enters the roots in the state of car- 

 bonate, it has the power, and probably exercises it, of decom- 

 posing the alkaline sulphates and chlorides, converting them 

 into carbonates, and thus preparing them to combine with the 

 organic acids formed in the sap, with which we find them so 

 generally united. 



c The salts of ammonia carry into the plant the sulphuric, 

 muriatic, humic, and other acids with which they may happen 

 to be combined, and thus supply other elements which are 

 directly or indirectly necessary to the production of the parts 

 of the plant. 



d They are all the producers of, or are necessary to the 

 production of numerous chemical changes in the sap. These 

 changes are as yet by no means understood, but we know that 

 they take place, and that nitrogen, sulphur, phosphorus, &c., 

 are necessary to the production of them. None of the sub- 

 stances we have it in our power to apply to growing plants is 

 capable of undergoing more varied transmutations than ammonia. 

 Such transmutations it not only itself undergoes in the interior 

 of plants, but, in so changing, it causes, or is accompanied by, 

 similar chemical changes in other substances also without 

 which constant and varied metamorphoses, the healthy growth 

 of plants could not proceed. 



3. Experiments with carbonate of ammonia, and with am- 

 moniacal liquor. 



I am not aware of any field experiments which have been 

 made with carbonate of ammonia in any other form than that 

 in which it occurs in the ammoniacal liquor of the gas-works. 

 This liquor varies in strength, and, besides carbonate, it contains 



* See my Lectures on Agricultural Chemistry and Geology, 2d edition, p. 243. 



