332 BOTANY. [ch. xvi. 



heterostyled plants is of importance as showing that ste- 

 rility is no test of specific distinctness, and that it depends 

 on differentiation of the sexual elements which is independ- 

 ent 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. 



