520 Influence of Nutrition and Selection. 



The truth of the theory put forward by Schindler 

 and Von Proskowetz that it is impossible to unite many 

 good quahties in one individual, depends partly on the 

 absolute productive capacity and partly on the correct 

 nourishment of the individual qualities at the sensitive 

 period of their development. Johannsen's exhaustive 

 and epochmaking researches into the correlation between 

 seed-weight and nitrogenous contents of barley point in 

 the same direction. The heavier the grain the greater 

 is the amount of nitrogen Vv^hich depreciates the value 

 of the grain. ^ Evidently both vary in the same direc- 

 tion under the influence of high nutrition. But if the 

 sensitive periods for the two should not coincide, the 

 supply of nutriment might be so managed that the weight 

 of the seed is increased without effecting a corresponding 

 increase in those constituents of the seed which are rich 

 in nitrogen. At present it is not possible to do this 

 directly, but Johannsen succeeded in getting a much 

 better harvest without having increased its proportion of 

 nitrogen, by selecting the one value in a positive direc- 

 tion and the other in a negative one. 



A further series of experiments is necessary before 

 the conclusions (important alike to the pure and applied 

 biologist) based on these remarkable results can be re- 

 garded as thoroughly established. I am simply using 

 them here as a proof of the relation between nutrition 

 and selection in general. 



For there is yet another method of studying the re- 

 lation between manuring and selection. We can alter 

 both factors; and allow them to operate either in the 



*W. Johannsen, Ueher die VariahiUtat der Gerste mit heson- 

 dercr Ri'icksicht auf das Verhaltyiiss zwisclien Korncrgewiclit und 

 Stickstoffprocent. Meddelelser fra Carlsberg Laboratoriet, Bd. 4, 

 Heft 4, 1899. 



