314 



GENERAL SCIENCE 



reason of climatic conditions. To mature the crop requires 

 about four months from the late frosts of spring to the early 

 freezes of fall. So vigorous is the growth of the corn plant 

 that abundance of water and of plant food must be available. 

 The demand for moisture is especially heavy at the time 

 when the ears are forming. The corn plant has a most ex- 

 tensive root system of the fibrous form penetrating the soil 

 to long distances in all directions. In the growing season the 



FIG. 1 02. Relation of corn crop (dotted line) to rainfall (solid line). 



quantity of water that passes from the leaves into the air by 

 transpiration demands an excessively large supply daily 

 from the soil. To conserve the moisture content of the soil 

 requires that the surface layer be kept finely pulverized, and 

 that the ground be kept free from weeds which rob it both 

 of moisture and of food material. The corn plant has a 

 relatively large amount of leaf surface, and a correspond- 

 ingly large amount of chlorophyll by means of which the 

 production of food for plant growth occurs. 



