344 THE SELF-FERTILIZATION OP PLANTS. 



enhance the fertility; or, where the parents are self- 

 impotent, restore the reproductive power. 

 As Darwin has said : 



" It is not that the varieties which differ largely in 

 some one point, do not differ at all in other points. 

 The laws of Correlation, the importance of which 

 should not be overlooked, will ensure some differ- 

 ences." 



The slightly different conditions of plants, growing 

 along side of each other, will entail a dissimilarity of 

 development, which will furnish occasion for good 

 from a cross between them. This applies, not merely 

 to different plants, but even to the different sets of re- 

 productive elements, growing upon the same plant! 

 By' the following remarks, Darwin shows, what little 

 differences, in the conditions, entail different modifica- 

 tions of the specific type : 



"Even the seeds," he says (p. 304, Vol. ii, Animals 

 and Plants, &c), "nurtured in the same capsule, are 

 not subjected to absolutely uniform conditions, as they 

 draw their nourishment from different points." 



This explains the reason of cases like the following, 

 where the action of the same pollen is widely different, 

 according as it is placed upon the stigma of the same 

 flower, upon the stigma of a flower on the same twig, 

 upon the stigma of a flower on another bough, or upon 

 the stigma of a flower on a different plant. It is pos- 

 sible for Darwin to see, that, in many such cases, the 

 good derived, is in proportion to the differences between 

 the organisms, or to the differences between the parts, 

 of organisms, contributing the reproductive elements. 



