22 THE ri.ANT. 



Water is composed of hydrogen and oxygen, and, if 

 analyzed, yields simply these two gases. Plants per- 

 form such analysis, and in this way are able to obtain 

 a sufficient supply of these materials, as their sap is 

 composed chiefly of water. "Whenever vegetable 

 matter is destroyed by burning, decay, or otherwise, 

 its hydrogen and oxygen unite and form water, which 

 usually escapes in the form of an invisible vapor. 

 The atmosphere of course contains greater or less 

 quantities of watery vapor arising from this cause 

 und from the evaporation of liquid water. This 

 rapor condenses, forming rains, etc. 



Hydrogen and oxygen are never taken into con- 

 eideration in manuring lands, as they are so readily 

 obtained from the water constituting the sap of the 

 plant, and consequently they need not occupy our 

 attention in this book. 



NITKOGEN. 



Nitrogen^ the only remaining atmospheric constitu- 

 ent of vegetable matter, is for many reasons worthy 

 of close attention. 



1. It is necessary to the growth and perfection of 

 all cultivated plants. 



2. It is necessary to the formation of all animal 

 substances. 



3. It is often deficient in the soil. 



4. It is liable to be easily lost from manures. 

 Athough about four-fifths of atmospheric air are 



pure nitrogen, it is almost certain th?it plants get no 



