DARWINISM STATED BY DARWIN HIMSELF. 



ADVANTAGES OF CROSS-FERTILIZATION. 



The Effects There are two important conclusions which 



of Cross and i^jjjj; i . • 



Self Fertili- mav De deduced from my observations : 1. 

 zation in the That the advantages of cross-fertilization do 

 Kingdom 6 no ^ f°U 0W from some mysterious virtue in the 

 page 443. mere union of two distinct individuals, but 

 from such individuals having been subjected during pre- 

 vious generations to different conditions, or to their having 

 varied in a manner commonly called spontaneous, so that 

 in either case their sexual elements have been in some de- 

 gree differentiated ; and, 2. That the injury from self- 

 fertilization follows from the want of such differentiation 

 in the sexual elements. These two propositions are fully 

 established by my experiments. Thus, when plants of 

 the Ipomma and of the Mimnlus, which had been self- 

 fertilized for the seven previous generations, and had been 

 kept all the time under the same conditions, were inter- 

 crossed one with another, the offspring did not profit in 

 the least by the cross. 



P a ^ ie cu " ous cases °f Plants which can fer- 



tilize and be fertilized by any other individual 

 of the same species, but are altogether sterile with their 

 own pollen, become intelligible, if the view here pro- 

 pounded is correct, namely, that the individuals of the 

 same species growing in a state of nature near together 

 have not really been subjected during several previous 

 generations to quite the same conditions. 



POTENCY OF THE SEXUAL ELEMENTS IN PLANTS. 



p It is obvious that the exposure of two sets 



of plants during several generations to differ- 

 ent conditions can lead to no beneficial results, as far as 



