96 



Plant-Breeding 



transmitted to it. We have said that this office of sex to 

 induce variation is more important than the mere fact of 

 reproduction of a complex organization ; for it must be 

 borne in mind that the complexity of organization is 

 itself a variation and adaptation made necessary by the 

 increasing struggle for existence. 





FIG. 30. Extreme variability in the shape of the leaves of hybrid 

 poppies. Second generation from a cross between the Bride variety 



r^rvlTlm Tvrf-ir-vr-vtr o-rrl -fVio O-nion-fol r-i/-kr\-r\tr 



puppies. oecuiiu gtmerauou irum a cross ut; 

 of the Opium poppy and the Oriental poppy, 



If, therefore, the philosophy of sex is to promote variation 

 by the union of different individuals, it must follow that 

 the greatest variation must come from parents consider- 

 ably unlike each other in their minor characters (Fig. 30) . 

 Thus it comes that in-breeding tends to weaken a type 

 and cross-breeding tends to strengthen it. At this point 

 we meet that particular subject that we wish to discuss. 



