EXERCISES 



139 



acre upon the field to be planted with soy beans. A good 

 inoculation can be obtained by merely mixing equal quan- 

 tities of bacteria-laden 

 earth and soy beans and 

 planting the mixture. 

 The roots of the plants 

 on the land thus treated 

 will be found to have 

 the nodules attached to 

 them in abundance, and 

 the absence of the nod- 

 ules will be noticed in 

 plants from fields not 

 inoculated. Tests seem 

 to show that there are 

 a limited number of the 

 nitrogen-fixing bacteria 

 for soy beans in all soils, 

 but it is best to inocu- 

 late to secure at once 

 their beneficial action. 



Fig. 76. Nodules on the roots of soy beans. 



EXERCISES 



1. What are the principal characteristics of the legumes? 



2. How does the protein content of the legumes compare 

 with that of cereal grains? 



3. How do legumes benefit the soil? 



4. Under what conditions will clover "wear out" the land? 



5. What are the principal legumes grown in the Northern 

 States? In the South? 



6. Can a piece of land be inoculated for alfalfa by sowing 

 clover on it? 



