FARM CROPS 103 



clover or pea family, after prominent members of the group. 

 Other common plants included in it are beans, lentils, locust 

 trees, alfalfa, vetches, lupins, cow peas, and soy beans. 



The growth of characteristic one-sided blossoms and the 

 formation of seed in a pod are distinguishing features of tly 

 members of this family. 



They have power, under proper conditions, of taking 

 free nitrogen from the air for their own use in growing. They 

 have nodules on their roots which are the homes of special 

 kinds of helpful bacteria. It is when these bacteria are 

 present that the plants can use the nitrogen from the air. 

 None but members of this family are thus able to use the 

 free nitrogen. But when the stubble and roots of the legumes 

 decay they leave nitrogen in the soil in a form which other 

 kinds of crops can use. As nitrogen is the most expensive 

 element in purchased fertilizers, farmers should use members 

 of this family often in the rotation courses to secure nitrogen 

 in the soil for all crops. (Page 87.) 



EXERCISE. To Become Acquainted with Some Legumes. 

 The members of the class should bring samples of different 

 clovers, alfalfa, vetch (wild pea), beans, peas, or other 

 legumes. If possible, examine the pods of seed in the heads 

 of clover and on other plants. Note also the one-sided 

 appearance of the blossoms on all of them. The clover 

 heads are composed of many blossoms. 



EXERCISE. Nodules on Clover Roots. Have some of 

 the older pupils dig up roots of clover, alfalfa, or other leg- 

 umes. Wash them and find the nodules or lumps, the size 

 of a pin-head or larger. These are the homes of many bac- 

 teria which aid the clover plants in getting nitrogen. Save 

 the best samples obtained in this exercise by placing them 

 in a bottle of water with a small amount (2 per cent) of 

 formalin added to it. (See Figs. 52 and 55a.) 



Legumes for Summer Forage. Farmers should give 

 some attention to the growing of several legume crops and 



