446 MISSOURI STATE HORTICULTURAL SOCIETY. 



having a considerable portion of organic matter retain a still greater 

 portion. 



The most common forms in a commercial way are carbonate, ni- 

 trate and muriate of ammonia, which have a direct and favorable influ- 

 ence on vegetable life, not only promoting rapidity and luxuriance of 

 growth, but in the interior portions causing the substances taken up as 

 plant food to separate from some and recombine with other elements, 

 and so build up the structure. Uniting successfully with the organic el- 

 ements and their principal compounds as the nature of each plant re- 

 quires, it seems to be a sort of essential distributive force. 



NITRIC ACID. 



The combination of one of nitrogen with five of oxygen forms nitric 

 acid. It derives its name from nitre or saltpetre, being generally ob- 

 tained by the distillation of this permanent salt. It imparts a yellow 

 color to most animal and vegetable substances. It is not found in a 

 pure state, but in the tropical regions it is found in combination with 

 lime, soda and potash, and known as nitrate of soda, lime and potash. 

 These salts are soluble in water, yet are solid when dry. The nitrates 

 of lime, soda and magnesia, so strongly attract moisture from the air 

 that in damp weather they are inclined to assume a liquid form, and 

 hence, in soils, increase its powers of absorbing and retaining moisture. 

 In small quantities these have a salutary effect upon plant growth, es- 

 pecially the grasses; yet when a soil has naturally enough of these ele- 

 ments to induce the vigorous growth of any plant, the addition of more 

 would probably not prove beneficial. 



The most important use which nitric acid has in its relation to soils 

 and plant growth, consists in its remarkable solvent powers, for by its 

 action the alkaline mineral elements become capable of assuming a 

 liquid form, the condition precedent to their being used so as to influ- 

 ence and aid plant growth. As it is exhaled by the leaves, its use is 

 similar to that of carbonic acid in perfecting the organization. 



PHOSPHORIC ACID. 



Another auxiliary to plant growth is phosphoric acid, which by com- 

 bination with potash, lime and soda, constitutes the valuable commercial 

 fertilizers, known as the phosphates, which are extensively used. 



All of the compounds treated in this paper are the immediate pro- 

 moters of plant growth, being essential to perfect organization, germi- 



