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 I 

 brought my strain within two years up to an 

 average of nearly 90 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, an< ^ 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 (Rammculus 

 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 



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