Whaley • The Gifts of Hybridity 



constitute the environment. A hybrici 

 which will grow well and produce large 

 )iclds in one locality may be distinctly 

 inferior in another. This feature of 

 hybrid corn production giv'es the prob- 

 lem some local flavor and makes it 

 necessar\- to study the behavior of in- 

 di\idual hybrids under given sets of 

 conditions before their adaptabilit}^ 

 and usefulness can be determined. 



To whichever of the genetic bases 

 heterosis is related, it has its roots in 

 the changes wrought by evolution. The 

 phenomenon presents an attractive 

 field for investigation of the part 



267 



placed by specific factors in evolu- 

 tionar\' change. Our studies of heterosis 

 contribute to several fields of knowl- 

 edge. In addition, the practical use- 

 fulness of these effects of h\briditv is 

 tremendous. Can we but learn enough 

 of their nature and development we 

 can make available the gifts of hvbrid- 

 ity in many important crop plants and 

 domestic animals. The bequest might 

 go far toward meeting the food and 

 energy demands which increasing 

 populations are imposing upon the 

 world. 



QUESTIONS 



1. What is meant by heterosis? 3. Describe the "double cross" in corn. 



2. What has heterosis contributed to the 4. Why did the Indians plant variously- 

 vvorld's food supply? colored corn grains together? 



