326 THE STRUCTURE OF FLOWERS. 



This concludes his experiments with English plants ; and 

 though crossing did little or no good, and the first average 

 of heights, viz. 100 : 82, he thinks were accidental, the 

 converse proposition, that self -fertilisation was injurious, is 

 in no way proved. It would be just as logical to say that, 

 since the self-fertilised plants grew more vigorously after 

 both were cut down, that crossing must have weakened the 

 constitution of the crossed seedlings. Or, again, from the 

 second year's results, we might justly conclude that the two 

 effects were quite identical. 



He next experimented with seed the parents of which 

 had been cultivated in Brazil, in which country Fritz 

 Miiller had found them to be " absolutely self-sterile with 

 pollen from the same plant, but perfectly fertile when ferti- 

 lised with pollen from any other plant." Seeds raised from 

 these in England " were found not to be so completely self- 

 sterile as in Brazil." The average number of seeds produced 

 in the capsules borne on the intercrossed and self-fertilised 

 plants of Brazilian origin were 80 and 12 respectively in the 

 first year; that is in the ratio of 100 : 15. 



With regard to the second generation, or grandchildren, 

 next raised, Mr. Darwin ob&erves : " As the grandparents in 

 Brazil absolutely required cross-fertilisation in order to 

 yield any seeds, I expected that self- fertilisation would have 

 proved very injurious to these seedlings, and that the crossed 

 ones would have been greatly superior in height and vigour 

 to those raised from the self-fertilised flowers. But the 

 result showed that my anticipation was erroneous ; for as in 

 the last experiment with plants of the English stock, so in 

 the present one, the self- fertilised plants exceeded the crossed 

 by a httle in height, viz., as 100 : 101." 



In the next year the average number of seeds per capsule 

 of the crossed and self-fertilised was as 100 : 86"6 ; so that the 



