CHAPTER XVI 

 THE BREEDING OF CORN 



Under any given set of conditions the yield of corn is 

 conditioned on two sets of forces. The first and most 

 commonly recognized set of forces is external to the plant 

 and consists of the plant's environment. The second s^t 

 resides within the plant itself and is commonly expressed 

 as heredity. 



Certain factors of environment, such as temperature, 

 light and rainfall, are beyond our control. Others, such as 

 the ravages of insect enemies and parasitic f ungi~ are par- 

 tially controllable; whereas tillage and the supplying of 

 food to the plant are almost wholly under control. The 

 two last named factors have received widespread atten- 

 tion from corn growers. The factors of heredity have been 

 almost wholly disregarded. The possibility of improving 

 corn by breeding has long been recognized, and in recent 

 years many evidences of such improvement have been 

 furnished in this country by the agricultural experiment 

 stations, state departments of agriculture, the national 

 Department of Agriculture and other agencies, as well as 

 by many grpwers of commercial seed. 



229. The significance of type in com breeding. — 

 Corn breeders in the past have laid much emphasis on the 

 value of selecting seed with a definite type of plant in view. 

 For example, directions for selecting are often given with 

 reference to the type of ear as regards its length and cir- 

 cumference as well as depth and shape of kernels. Also 



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