EXERCISE A-35. TO STUDY THE ROOTS 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 home of the bacteria which have 

 the power of taking the nitrogen from the soil air 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 fertilizer. 

 Only the legumes that have the nodules on their roots are 

 able to use the 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. 



Roots showing the nodules may be preserved in cans 

 or wide-mouthed bottles by the use of formalin * solution, 

 consisting of one tablespoonful of formalin to each quart 

 of water. 



Observe that the nodules on the clovers and alfalfa 

 are quite small, while those on peas and soy beans are 

 much larger. In addition to the nitrogen which red clover 

 and alfalfa bring to the soil, they exercise a very beneficial 

 effect upon the physical condition by means of their strong, 

 deep root system. 



* Formalin (40%) can be purchased at any drug store. It is a 

 clear, colorless liquid. 



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