The Operation of Nutrition and Selection. 537 



I have confined myself to positive changes, but with re- 

 gard to selection to both positive and negative ones; and 

 I have also studied the effect of high nutrition continued 

 through a number of generations without selecti(jn. 



High nutrition has proved itself superior to the most 

 stringent selection (Fig. 116). Even when combined 

 with negative selection it has improved the mean H^ig. 

 116B) and positive selection has, in combination with it. 

 only been able to achieve very little more (Fig. 116Cj. 

 And without any selection at all an exceptionally high 

 nutrition has had a far better result than the first two 

 combinations (Fig. 116 D). 



Fig. 116 shows the main result of this whole series 

 of experiments. The curves B (negative selection) and 

 C (positive selection) are taken from the first year; tliis 

 was done because the two following years brought no 

 further progress in the same direction in spite of con- 

 tinued selection. The experiments extend over three 

 generations ; but all nine curves have not been included 

 since this would have rendered the figure practically un- 

 intelligible. 



For this experiment, seeds of the laez'ifoIia-\mm\y 

 (p. 273) were sown in 1891 and some of them highly 

 manured with horn-flour (steamed and crushed horns 



verted into percentages. The distance of the ordinates apart is 7.5 

 mm. The height of the ordinates is 1% ^2 mm. 



A. (123 plants) The original curve of the mean fruit-length after 



the first apphcation of nitrogenous manure in 1891. 

 B and C. The result of manuring the mother-plant in 1891. 

 B (78 plants) The next generation after selection of short-fruited 

 seed-parents. The curve has nevertheless shifted distinctly to 

 the right. 1892. 



C. (147 plants) The same generation as B. but after selection c^f 



long-fruited secdparents ; the curve has only shifted a little 

 more than B. 1892. 



D. After three years of cultivating the seedlings in pots. i. e.. by 



the most effective form of nutrition, but without selection. The 

 curve has shifted to the right far more than C". 1894 (88 plants). 



