296 'DIFFERENT FORMS OF FLOWERS 



sesses both the sexual elements. The difference is that in 

 the case of the primrose it is perfect fertility, and not simply 

 fertility, that depends on the mutual action of the two sets of 

 individuals. 



The work on heterostyled plants has a special bearing, to 

 which the author attached much importance, on the problem 

 of origin of species.* 



He found that a wonderfully close parallelism exists 

 between hybridisation and certain forms of fertilisation 

 among heterostyled plants. So that it is hardly an exag- 

 geration to say that the " illegitimately " reared seedlings are 

 hybrids, although both their parents belong to identically the 

 same species. In a letter to Professor Huxley, given in the 

 second volume (p. 384), my father writes as if his researches 

 on heterostyled plants tended to make him believe that 

 sterility is a selected or acquired quality. But in his later 

 publications, e.g. in the sixth edition of the ' Origin,' he 

 adheres to the belief that sterility is an incidental rather than 

 a selected quality. The result of his work on heterostyled 

 plants is of importance as showing that sterility is no test 

 of specific distinctness, and that it depends on differentiation 

 of the sexual elements which is. independent of any racial 

 difference. I imagine that it was his instinctive love of 

 making out a difficulty which to a great extent kept him 

 at work so patiently on the heterostyled plants. But it 

 was the fact that general conclusions of the above character 

 could be drawn from his results which made him think his 

 results worthy of publication."!* 



The papers which on this subject preceded and contributed 

 to * Forms of Flowers ' were the following : 



" On the two Forms or Dimorphic Condition in the Species 

 of Primula, and on their remarkable Sexual Relations." Linn. 

 Soc. Journal, 1862. 



* See ' Autobiography,' vol. i. f See ' Forms of Flowers,' p. 243. 

 p. 97. 



