Effect of Selection Obliterated by Nutrition. 561 



The following values have been calculated from this table : 



Year Seed parent Qi 



1892 



1893 



1894 



Increase 1892—1893 



1893—1894 



12—16 

 10—13 



1.5 

 3.6 

 4.5 



Af 



18.3 

 21.2 

 25.2 



3.6 

 3.5 

 4.4 



M 



0.14 

 0.17 

 0.18 



4-2.1 4-2.9 -0.1 

 4-0.9 4-4.0 +0.9 



The amplitude of variation also increased exactly as it 

 did in the short-fruited race of Oenothera Lamarckiana 

 under similar conditions. 



The value 0/M renders possible a comparison be- 

 tween the amplitude of variation in this case and in 0. 



J,i 66 3S !iO U2 



Fig. 117. Anethnm gravcolcns. Curves of the rays of the 

 temiinal umbel. The numbers under the abscissae refer 

 to the rays of the primary umbel. In accordance with 

 the rule discussed on page 527 the number of ordinates 

 is half the number of groups in the table. The figure 8 

 therefore means eight and nine rays and so forth. 



A. (56 plants) Curve of 1892, irregular on account of 

 the small number of individuals. It is also asymmet- 

 rical being drawn out more to the right. 



B. (518 plants) Curve of the following generation 

 1893. As a result of nutrition and selection it has be- 

 come nearly symmetrical. 



Lamarckiana, where it was 0.08 (p. 531). The number 

 of umbel-rays is therefore, when measured in this way. 

 twice as variable as the fruit-length in Oenothera. 



The asymmetrical curve of the year 1892 ((?2>(?i) 



