550 Length of the Fruit in Oenothera Lamar ckiana. 



derived from the aoove experiments, collected in a single 

 table. The numbers signify millimeters as before. 



FRUIT LENGTH OF OENOTHERA LAMARCKIANA. 



Date 5 Qi ^ Qz 



Original form, Hilversum 1893 — 1.9 24.1 2.0 



" culture 1891 — 1.3 25.2 1.5 



Long fruited race 1892 32.6 2.6 33.4 2.4 



1893 42.6—43.0 2.3 31.4 2.6 



1894 37.0—41.0 3.2 31.6 2.4 

 Short fruited race 1892 20.6 2.5 29.9 2.6 



1893 23.2—23.4 3.9 26.5 3.3 



1894 15.6—21.4 2.7 24.2 5.2 



^ I regard the following generalizations as the most im- 



portant results of these experiments, combined with the 

 results detailed in the next section (Fig. 116 D) : 



1. The variation of the length of the fruit follows 

 the Ouetelet-Galton law (Fig. 116 A-D). Each curve 

 is determined by three values. The median, M, or the 

 mean value, and the two quartiles Qi and Q2 within 

 which fall half of the deviations from the mean. 



2. The mean fruit-length is much influenced by nu- 

 trition as well as by selection, and more by a single 

 manuring of the parent-plant than by a once or twice 

 or even thrice repeated selection of long-fruited plants 

 as seed-parents (long-fruited race 1891-1894). It is 

 influenced even more by a few years of cultivating the 

 seedlings in pots, and the addition of much manure to 

 the pots of the seedlings (pot-culture without selection 

 1892-1894, §5). 



3. The amplitude of variation f g = ^^"*" ^| increases 



only slightly, so long as nutrition and selection work 

 in the same direction. But as soon as they work in oppo- 

 site directions the multiformity of affecting causes in- 



