254 The Pedigree Families. 



number of new forms amounted to between 1 and 2 % 

 of the total cultivated. 



In other words : The new elementary species arose 

 from the parent form in a ratio of 1-2 %. Sometimes 

 more than, but oftener less than, this value. And this 

 ratio was maintained throughout the whole course of 

 my experiment, so far, at least, as the difference in the 

 methods of investigation which have been employed at 

 different times permit me to estimate it. 



This figure, 1-2 %, is more probably too small than 

 too large. For it was only in the years 1895 and 1896 

 that I went to the labor of determining it accurately. In 

 previous years the average was considerably lowered by 

 other circumstances, the most important of which was 

 the omission of such forms as O. ohlonga, O. nihrinervis 

 and O. scintiUans which at that time I could not recognize 

 in their early stages. The table on page 224 shows, for 

 the two years 1895 and 1896, 22,000 individuals of La- 

 marckiana and 711 of the new forms. That is, more than 

 3 %. 



O. laevifolia and 0. brevistylis formed far smaller 

 a percentage than 3 % of the number of Oenotheras 

 growing on the original field at Hilversum ; yet they, 

 obviously, arose in quantities sufficient for them to main- 

 tain themselves. We may conclude therefore that a yearly 

 appearance in the proportion of from 1 to 3 % would be 

 sufficient for the establishment of a new species.^ 



V. The nezv characters have nothing to do with in- 

 dividual variability. Oenothera Lamarckiana exhibits a 

 degree of fluctuating variability in all its characters 

 which is certainly not less than that exhibited by other 

 plants. The new species fall right outside the range of 



^Compare the calculations of Delboeuf, as given above (I §28). 



