XIV 



ECONOMICAL 



159 



the rest was comparatively simple, and in a few years he 

 has been able to build up a strain of wheat which com- 

 bines the cropping capacity of the best English varieties 

 with the hardness of the foreign kinds, and at the same 

 time is completely immune to rust. This wheat has al- 

 ready been shown to keep its qualities unchanged for sev- 

 eral years, and there is little doubt that when it comes to 

 be grown in quantity it will exert an appreciable in- 

 fluence on wheat-growing in Great Britain. 



It may be objected that it is often with small differ- 

 ences rather than with the larger and more striking ones 



300 



200 



4 6 8 10 12 14 16 18 20 



"Weight of individual seeda 



FIG. 30. 

 Curves to illustrate the influence of selection. 



that the breeder is mainly concerned. It does not matter 

 much to him whether the colour of a pea flower is purple 

 or pink or white. But it does matter whether the plant 

 bears rather larger seeds than usual, or rather more of 

 them. Even a small difference when multiplied by the 



