EXERCISE 42. A FIELD STUDY OF LEGUMES 



Equipment: Spade; yardstick. 



Method: Carefully dig up a clover plant in the field, 

 noting the tiny nodules on the roots. 



Dig up other legumes and observe their root system and 

 the presence of nodules. 



These nodules are the homes of the bacteria which have 

 the power of taking the nitrogen from the soil and making it 

 available for the use of the clover plant. 



Discussion : Nitrogen is a very important food for plants 

 and is very expensive when purchased in a fertilizer. Only 

 the legumes that have the nodules on their roots are able 

 to use this free nitrogen of the soil air. The legumes include 

 the common clovers, alfalfa, soy beans, cow peas, garden 

 peas and many other plants, all of which have a beneficial 

 effect upon the soil. 



In sections where a legume has been grown for many 

 years the bacteria which work upon its roots may be found 

 in abundance in the soil, but when a legume is taken to a 

 new locality for the first time it is frequently desirable to 

 add to the soil the proper bacteria. This process is called 

 inoculation, and may be performed by means of pure cul- 

 tures or by the shipment of soil from a locality where the 

 legume has been growing. 



Roots showing the nodules may be preserved in glass 

 cans or wide-mouthed bottles by the use of a formalin solu- 

 tion consisting of one tablespoonful of formalin to each 

 quart of water. 



Note. — Formalin (forty per cent) can be purchased at any drug 

 store. It is a clear, colorless liquid. 



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