xiv Preface. 



had previous experience. He very wisely said, that 

 whether the hypothesis turned out to be a correct one 

 or not, one thing was plain, that the amount of evidence 

 I had to give in its support was not enough for the 

 purpose. I left the matter therefore for the time alone, 

 and promised myself to hunt for further evidence, when 

 my next year's holiday should come. But before that 

 time came, this essay of Kerner made its appearance, 

 rendering all further evidence unnecessary. He shows,' 

 by a mass of evidence which cannot but enforce con- 

 viction, that a viscid stem or viscid calyx is only one 

 amongst many contrivances, by which useless insects 

 are excluded from the nectaries. The general result of 

 his essay is to show, that, as the presence of nectar in 

 a flower implies most surely cross-fertilisation by the 

 agency of suitable animals, so also does it, with almost 

 equal certainty, imply the presence of some or other 

 contrivance by which that nectar shall be preserved 

 from unsuitable ones. 



The simplicity of some of the contrivances, and the 

 ingenuity of others, and the variety of methods by 

 which the same end is attained, are most striking. And 

 if the reader derive but half the pleasure that I have 

 done from their study, he will feel grateful for having 

 Kerner's essay made readily accessible to him. 



THE EDITOE. 



OdoUr, 1878. 



