276 NATURE STUDY AND AGRICULTURE 



large, dig up and examine the roots for tubercles. Why 

 do you find them on one and not on the other ? 



These experiments may be varied by inoculating some 

 clover seed and planting in some of the sterilized soil. This 

 may be done by pouring some water over soil in which 

 bacteria are present and shaking thoroughly. When the 

 water is clear, pour over the clover seeds and plant. 



Books and Bulletins: Principles of Agriculture, Bailey; 

 United States Department of Agriculture: Simple Exercises 

 Illustrating Some Applications of Chemistry to Agriculture; 

 Office of Experiment Stations, Bulletin 195. Farmers' 

 Bulletins: The Liming of Soils, No. 77; Soil Fertility, 

 No. 257; Renovation of Work-out Soils, No. 245; Soil In- 

 vestigations in the United States, No. 169. 



