Variation and Heredity 



471 



Summarizing the extreme variations in these qualities at 

 the beginning and close of the periods, the table on the 

 next page is suggestive. 



286. Pure lines. Johannsen has employed the term 

 " pure line " to denote the offspring of a single individual 

 .produced by self-fertilization (thus isolating a type, 

 genotype). With pure lines he has conducted extensive 

 selection experiments, and the results for quantitative 

 characters stand in contrast to those obtained by selec- 

 tion in an ordinary population. Selection within a pure 

 line, from modal individuals and from those showing the 

 greatest deviation, yield offspring the averages of which 

 are the same. According to this, selection within the 



TEN GENERATIONS OF BREEDING CORN FOR INCREASE AND DECREASE 



OF OIL 



