634 IMPROVEMENT OF LIVING THINGS BY MAN 



versity of Illinois have shown that the oil content of the grain, the 

 starch content, the position of the ear on the plant, and other 

 factors could be improved, but no new factor has been produced. 



In a government test of corn to increase the yield, ears were 

 chosen from plants that gave a high yield ; seed from these ears 

 was planted in rows alternating with seed from equally good- 

 looking ears from the same kind of corn not selected for its high 

 yield. Note the results with eight pairs of ears. 



Pounds of Corn Yieldei 



by the Seed of One Ear 



Field Ears 



Ears from High- Yielding Parents 



170 lbs. 



177.5 lbs. 



139.5 



180 



139 



199 



173 



197 



154 



172 



133 



176 



156.5 



194 



153 



200.5 



What per cent of increase was there from the selected corn? 

 If the seed from the field-grown corn yielded 42 bushels per acre, 

 what would have been the gain per acre by planting seed from the 

 selected corn ? State results both in bushels and in dollars, assum- 

 ing corn to be worth 50 cents per bushel. 



In selecting wheat we might breed for a number of different char- 

 acters, such as more starch, or more protein in the grain, a larger 

 yield per acre, ability to stand cold or drought, or to resist plant 

 disease. But although selection is the one most important method 

 for bettering production of crops, it is after all a hit-or-miss method, 

 as we do not know whether we are selecting variations that are 

 inheritable. Therefore in order to produce new varieties of plants, 

 another method is used, known as hybridization. 



Practical Exercise 17. Suppose you were selecting seed corn from an acre 

 for a large yield. How would you go about making the selection? Would 

 you select from large plants with large ears or plants bearing large kernels of 

 corn? Give reasons. 



Hybridization. We have already learned that pollen from one 

 flower may be carried to another of the same species and produce 



