450 Plant-Breeding 



EXERCISE 21 



Corn Selection Laboratory Study 



Purpose. To give the student an understanding of the 

 qualities that constitute a good ear of corn ; to teach the bene- 

 fits and dangers of cross-pollination. 



Material. For each student : 1 tape measure ; 1 scalpel ; 

 1 hand lens; 10 ears of corn selected from a row in breeding 

 plot; samples of various types and colors of corn. These 

 should have been shelled and soaked in water for 24 hours pre- 

 vious to this laboratory period in order to render them easy to 

 dissect. Cobs of corn bearing mixed kernels to illustrate zenia ; 

 scales ; data sheets ; germinator. 



Program. The instructor should first explain the purpose 

 of the practicum and outline the afternoon's work. He should 

 explain the structure of a kernel of corn, calling attention to 

 the difference between the various types of corn and the ad- 

 vantage of certain shaped kernels. Fecundation should be 

 thoroughly discussed, and its effect in causing zenia. Illustrate 

 with diagrams, charts, and specimens. 



Discuss the dangers of mixing varieties by close planting. 

 The danger of close fertilization and the stimulus resulting from 

 cross-fertilization should also be discussed. 



The advantage and manner of making germination tests 

 should be explained. 



The student should remove 6 kernels from each ear and place 

 them in the germinator to be examined later, at which time he 

 should record the percentage of germination. 



Questions and problems concerning zenia printed on the 

 outline sheet should be answered in a written report. 



Laboratory Directions for Corn Study 



1. Complete taking data on 10 ears of corn. Compare with 

 remnant half of parent ear. From your data select the best 

 3 ears for breeding purposes. 



