THE BOLL-WEEVIL 15 



The people began to prepare their lands better and 

 better. As. they showed them these things they 

 talked to the farmers, saying: "The soil needs air 

 and water. You let your lands lie idle during winter, 

 with stalks and stubble and weeds on them ; the re- 

 sults are land-washing and the loss of plant-food, 

 and it has been shown that the weeds and stalks 

 provide shelter for the boll-weevils in winter. If 

 possible plow your land well in the fall to enable the 

 soil to store up moisture ; cover-crops should be 

 sown to prevent the loss of this moisture, to avoid 

 the leaching away of the plant-food, and to keep the 

 soil from washing. Good crops for this purpose are 

 rye, oats, and wheat, but whenever possible crops 

 should be used that have the power to add nitrogen 

 to the soil, because this is one of the most important 

 and most expensive plant-foods." 

 The people who had listened became very much 

 interested, and asked, "What are some of the plants 

 that have the power to make nitrogen?' 7 They 

 were told that good examples were vetch, cowpeas, 

 clovers, alfalfa, and others ; that the vetches and 

 some of the clovers made good ccfver-crops. Some 

 asked, "How can any plant make nitrogen in the 

 soil?" The entomologist replied: "One day when 

 Dr. Science was walking across a field he heard a 

 vetch-plant and a bacterium talking together, and he 

 listened. 



