546 Length of the Fruit in Oenothera Lamarckiana. 



The mean fruit-length has therefore, in spite of rigid 

 selection not only not increased but actually decreased. 

 Selection can do no more than, to use Hallett's expres- 

 sion, fix the fruit-length attained by high nutrition : and 

 it barely manages that. 



The quartiles have remained pretty constant since 

 1892; the curve has remained practically symmetrical 

 and its amplitude has neither increased nor decreased 

 much. 



The increase in the mean fruit length was effected 

 (in 1892) without any regression; but after that the 

 selection was accompanied by a heavy regression; that 

 is to say, the value of M, reached in the years 1893 and 

 1894, fell far short of the M of the selected seed-pa- 

 rents {S). :1c * * 



We now come to the continuation of the short-fruited 

 race in the two years 1893-1894. 



Like the long-fruited culture, this was continued for 

 two more years under normal conditions of manuring 

 and by selecting seeds from very short-fruited plants, 

 for raising the next generation. In § 3 it was shown 

 that short-fruited plants were as a rule ill-favored, i. e., 

 poorly nourished ones. In this way selection would 

 very soon counteract the effect of the heavy manuring 

 of 1891. And the mean fruit-length has, as a matter 

 of fact, undergone a marked diminution in these two 

 years, whereas the amplitude of variation has, on the 

 other hand, increased considerably. 



