496 Mutations 



order to isolate the reputed pure grandiflorum 

 type. During the beginning of the flowering- 

 period I ruthlessly threw away all plants dis- 

 playing less than 21 rays in the first or terminal 

 head. But this selection was not to be consid- 

 ered as pure, because the 13-rayed race may 

 eventually transgress its boundary and come 

 over to the 21 and more. This made a second 

 selection necessary. On the re-selected plants 

 all the secondary heads were inspected and 

 their ray-florets counted. Some individuals 

 showed an average of about 13 and were de- 

 stroyed. Others gave doubtful figures and 

 were likewise eliminated, and only 6 out of a 

 lot of nearly 300 flowering plants reached an 

 average of 21 for all of the flowers. 



Our summer is a short one, compared with the 

 long and beautiful summer of California, and it 

 was too late to cut off the faded and the open 

 flowers, and await new ones, which might be 

 purely fertilized after the destruction of 

 all minor plants. So I had to gather the seed 

 from flowers, which might have been partially 

 fertilized by the wrong pollen. This however, 

 is not so great a drawback in selection experi- 

 ments as might be supposed at first sight. The 

 selection of the following year is sure to elim- 

 inate the offspring of such impure parentage 



