GENETICS IN RELATION TO AGRICULTURE 



The Illinois Station experiments have included selection for many 

 other characters of the corn plant in more recent years. One of the most 

 striking results was obtained by selecting for height of ear on the plant. 

 Data on which to base selection were secured by measuring several 

 hundred stalks in the oil and protein plots, noting height of ear above the 

 ground, total height of stalk, apparent number of internodes below the 



'96 '97 '98 '99 '00 '01 '02 '03 '04 '05 '06 '07 '08 '09 '10 '11 '12 '13 '14 '15 



Year of Selection 



FIG. 133. Two graphs representing the effects of selection for high and low oil content in 

 the Illinois Station corn experiments. (Data from Castle.) 



ear and number of internodes above the ear. Fig. 135 shows the result 

 of selecting for high and low ears during five generations. Similar results 

 were obtained from selection in the case of position of ear at maturity 

 and total yield. 



The striking results of these carefully conducted experiments have 

 been cited by various authors as evidence par excellence for the most 



16 

 15 



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8 13 



3 10 



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8 

 7 



'96 '97 '98 '99 '00 '01 '02 '03 '04 '05 '06 '07 '08 '09 "10 '11 '12 '13 '14 "15 



Year of Selection 



FID. 134. Two graphs representing the effects of selection for high and low protein con- 

 tent in the Illinois Station corn experiments. (Data from Castk.) 



diverse conceptions of the rdle which selection plays in evolution and 

 breeding. Thus the earlier allusions of Hopkins and Smith, the discus- 

 sion in E. Davenport's text on breeding, and the recent treatment by 

 Castle all seem to attribute a peculiar creative power to selection which 

 meets with a certain "response" on the part of the plant. This is in line 

 with the Darwinian idea that all fluctuating variations are heritable and 

 that the continuous selection of minor fluctuations in a certain direction 

 is always effective in shifting the type. 



