THE I'LANT. 23 



nutriment directly from this source. It is all obtained 

 from some of its compounds, chiefly from the one 

 called amm >nia. Nitric acid is also a source from 

 which plants may obtain nitrogen, though, to the 

 fanner, it is of less importance than ammonia. 



AMMONIA, 



Ammonia is composed of nitrogen and hydrogen. 

 It has a pungent smell and is familiarly known as 

 liartshorn. The same odor is often perceptible 

 around stables and other places where animal matter 

 is decomposing. All animal muscle, certain parts of 

 plants and other organized substances, consist of 

 compounds containing nitrogen. When these com- 

 pounds undergo combustion, or are in any manner 

 decomposed, the nitrogen which they contain unites 

 with hydrogen, and forms ammonia. In conse- 

 quence of this the atmosphere always contains more 

 or less of this gas, arising from the decay and com- 

 bustion which are continually going on all over the 

 world. 



This ammonia in the atmosphere and that which is 

 contained in the soil (derived from the decomposition 

 of organic matters within it) is the capital stock to 

 which all plants, not artificially manured, must look 

 for their supply of nitrogen. As they take up am- 

 monia chiefly if not entirely through their roots, we 

 musit discover some means by which it may be con- 

 veyed from the atmosphere to the soil. 



"SV^ater may be made to absorb many times its 



