CHAPTER XIX 



NITROGEN AND ITS RELATION TO PLANTS 



Nitrogen. A substance which plays an important part in 

 animal and plant life is nitrogen. Soil and the fertilizers which 

 enrich it, the plants which grow on it, and the animals which 

 feed on these, all contain nitrogen or nitrogenous compounds. 

 The atmosphere, which we ordinarily think of as a storehouse 

 of oxygen, contains far more nitrogen than oxygen, since four 



fifths of its whole weight is 

 made up of this element. On 

 examining nitrogen we find 



7 ,,1\\\\\1\ tnat it i s colorless, odorless, 



and tasteless. If the oxygen 

 in a vessel filled with air is 

 made to unite with some 

 other substance, nitrogen re- 

 mains. This can be done by 

 floating on water a dish con- 

 taining phosphorus, then ig- 



FIG. 65. -Preparing nitrogen. n j ting the phosphorus, and 



placing an inverted jar over the burning substance (Fig. 65). 

 The phosphorus in burning unites with the oxygen of the air and 

 the gas that remains in the jar is chiefly nitrogen. 



Plant food. Food is the source of energy in every living 

 thing and is essential to both animal and plant life. Plants 

 get their food from the lifeless matter which exists in the air 

 and in the soil, while animals get their food from plants. It is 

 true that man and many other animals eat fleshy foods and 



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