136 THE EVOLUTIONIST AT LARGE, 



The male and female flowers of dog's 

 mercury have taken to living upon separate 

 plants. Why is this ? Well, there was no 

 doubt a time when every blossom had both sta- 

 mens and pistil, as dog-roses and buttercups 

 always have. But when the plant took to 

 wind fertilisation it underwent a change of 

 structure. The stamens on some blossoms 

 became aborted, while the pistil became 

 aborted on others. This was necessary in 

 order to prevent self-fertilisation ; for other- 

 wise the pollen of each blossom, hanging out 

 as it does to the wind, would have been very 

 liable to fall upon its own pistil. But the 

 present arrangement obviates any such con- 

 tingency, by making one plant bear all the 

 male flowers and another plant all the female 

 ones. Why, again, are the petals green ? I 

 think because dog's mercury would be posi- 

 tively injured by the visits of insects. It has 

 no honey to offer them, and if they came to 

 it at all, they would only eat up the pollen 

 itself. Hence I suspect that those flov 



