80 80UTBERN FIELD CROPS 



from the grain is used as a lubricant and for the manufac- 

 ture of a substitute for rubber. The pith from the stalk is 

 employed as a packing material in the construction of 

 warships. Corn . and its by-products are also used in 

 many other ways. 



Structure 



81. Roots. — The root system of the corn plant con- 

 sists of a number of long, slender, branched, fibrous roots. 

 There is no tap-root. A whorl of roots develops near the 

 germinating grain, but the main system springs from the 

 crown of the plant, which usually develops about 1 inch 

 below the surface. Therefore, the depth of rooting of 

 corn is largely independent of the depth at which the 

 grain is planted. 



As a rule, most of the main feeding roots originate 

 in the stratum comprised between 2 inches and 4 inches 

 below the surface of the ground (Figs. 30 and 31). These 

 usually grow out almost horizontally for some distance, 

 and then, if the soil permits, many of them bend down- 

 ward, while some of the smaller, secondary roots occupy 

 the surface layer of soil. Corn roots do not penetrate so 

 deeply in most Southern soils as in other parts of the 

 country. The depth at which roots feed seems to depend 

 chiefly on the supply of moisture and air in the soil. 



The roots of corn are frequently as long as the plant is 

 tall. Indeed, the roots may lap across the rows before the 

 plant is 1 foot high, so that deep cultivation, even at this 

 early stage, may break many roots. 



Besides the feeding roots just mentioned, the corn plant 

 usually develops, at the first few nodes or joints just above 



