122 PLANT FOOD 



3. Pupils usually know much more about the parts of plants above 

 the ground than they do about roots, the main feeding organs of 

 plants. The reason for this lies in the fact that roots are hidden from 

 view. The teacher should demonstrate before the class the complete 

 root systems of common farm plants. 



REFERENCES 



Fertilizers and Crops. Van Slyke. 



Soil Fertility and Permanent Agriculture. Hopkins. 



Fertilizers. Voorhees. 



Chemistry of Plant and A nimal Life. Snyder. 



Plant Culture. Goff. 



Farmers' Bulletins. Washington, D.C. 



186. Elementary Exercises in Agriculture. 



237. Lime and Clover. 



245. Renovation of Worn-out Soils. 



257. Soil Fertility. 



327. Conservation of Natural Resources. 



