1 20 VARIATION 



and De Vries considered that the strain was now pure and that 

 " no further selection could be of any avail." 



One of these two plants was distinguished. by producing two 

 secondary heads with twenty -two rays, whereas generally only 

 the terminal head reached so many as twenty-one, the other 

 retrograding often as low as to thirteen. This exceptional 'plant 

 was distinguished only by these two secondary heads. Its ter- 

 minal head had but twenty-one rays, and the average of all its 

 heads was not exceptionally high ; but no other plant out of 

 hundreds had ever produced secondary heads with more than 

 twenty-one rays, and it was from this plant that the double- 

 flowering line developed three years later. 



This plant appeared in 1896. Its seed was sown in 1897. 

 The largest number of rays in the terminal head suddenly 

 increased from twenty-one to thirty-four; next year (1898), to 

 forty-eight; next (1899), to sixty-six; and during this time the 

 general average for all the heads increased remarkably. No 

 indication of doubling had, however, yet appeared. The im- 

 provement was such as follows selective breeding with fluctuat- 

 ing variability, improvement by gradual change and without 

 mutations. 



Late in the season (September) of this year (1899), how- 

 ever, three secondary heads appeared on one plant with a few 

 ray florets scattered over the disk. The mutation anxiously 

 awaited for seven years had suddenly appeared in this small, 

 belated way toward the close of the growing season, and in 

 a manner that would have escaped the attention of any but 

 the most painstaking investigator, 1 and that would have invited 

 extermination in nature. 



This was in 1899. The heads were of course pollinated with 

 other and inferior flowers, but in 1900 the highest number of 

 rays rose to one hundred, and in 1901 reached two hundred. 

 He remarks, " Such heads are as completely double as are 



1 The student will note that every flower of thousands of plants was carefully 

 examined, and that in every case the foundation of the mutation was in an incon- 

 spicuous plant, certain to be overlooked by casual observers. The obvious lesson 

 is that only the most careful and systematic examination will detect the founda- 

 tion stock, so easily does it escape notice in the general mass and so readily is it 

 1 )st unless isolated and protected. 



