TH£J WORK OF ROOTS 



149 



escape of ammonia and nitrogen gas and partly to 

 the rain, which washes the soluble nitrogen compounds 

 out of the soil. 



Some plants have the power of taking nitrogen 



98. Tubercles on roots of Clover, 



from the air by means of the bacteria or minute plants 

 which inhabit tubercles on the roots. Such plants 

 are Clover (Fig. 98), Lupines, Beans and other mem- 

 bers of the Pea family. A crop of Clover or Lupines 

 plowed under and allowed to decay furnishes nitrogen 



