The Making of Species 
ordinary type. Moreover, I brought them under 
such conditions as are necessary for the full 
development of their character; and last, but 
not least, I have tried to improve their char- 
acter as far as possible by a very rigid and 
careful selection. . . . By this method [| 
brought my strain within two years up to an 
average of nearly go per cent. of the seedlings 
with a divided primary leaf (such seedlings 
averaging five leaves in the adult)... . This 
condition was reached by the sixth generation 
in the year 1894, and has since proved to be the 
limit, the figures remaining practically the same 
through all the succeeding generations... . I 
have cultivated a new generation of this race 
nearly every year since 1894, using always the 
strictest selection. This has led to a uniform 
type, but has not been adequate to produce 
further improvement.” Similarly, De Vries 
found in the bulbous buttercup (Ranunculus 
bulbosus) a strain varying largely in the 
number of petals; therefore he tried by 
means of continuous selection of those flowers 
having the largest number of petals to pro- 
duce a double flower, but was not able to do so. 
He succeeded in evolving a strain with an 
average number of nine petals, some individuals 
having as many as twenty or thirty; but even 
by breeding only from these last he could not 
increase the average number of petals in any 
70 
