A PKOOLC 1 OF SUNFLOWER BREEDING 



In 1910, Mrs. Cockerell found near Boulder, Colo., a mutant from the familiar yellow sun- 

 flower. Its rays were suffused with chestnut red, which proved on examination to be due 

 to anthocyan, a pink pigment that appeared chestnut because of its background. As 

 there was but one of these mutants, and the sunflower is sterile with its own pollen, 

 it had to be crossed back to the ordinary yellow form; when the seeds of this cross were 

 grown, it was found that about half of the flowers had red rays. One of the forms isolated 

 is shown above, and was named bicolor ; in red forms of another species the pattern was 

 reversed, the dark pigment being at the tips instead of the bases of the rays. It is 

 evident from the photograph that there is a pattern factor which controls the distribu- 

 tion of the dark pigment. The presence of this factor would not be suspected in an 

 ordinary yellow sunflower, although it is certainly there. The incident illustrates the fact 

 that one can never know, from mere inspection, all the factors that any plant or animal 

 has inherited, for many of them cannot get expression except under certain rare con- 

 ditions. (Fig. 5.) 



