EDITOR'S PREFACE. 



The year 1862 will ever be a memorable date in the 

 annals of botany, as that in which Mr. Darwin pub- 

 lished his classical work on the fertilisation of Orchids, 

 and in so doing disclosed a wide and unexplored region 

 to the research of physiological botanists. Since then 

 a huge mass of observations has been gradually ac- 

 cumulating, the general result of which is to con- 

 firm with great certainty the truth of the Darwinian 

 generalisation, that, so far at any rate as plants are 

 concerned, " Nature abhors perpetual self-fertilisation." 

 It has been shown that in the vast majority of flower- 

 ing plants — exceptions may here be disregarded — 

 appliances exist which will at any rate secure a more 

 or less frequent intercross, and that in many of them, 

 moreover, these appliances completely exclude the 

 possibility of self-fecundation. 



The agency by which this result is obtained, and 

 the pollen transported from one flower to another, may 

 be either inanimate or animate. 



In the former case it is the wind, or exceptionally 

 (Valisneria spiralis) water. Plants thus fertilised pre- 

 sent certain peculiarities. Their pollen, for instance, 

 is dusty, so as to be easily diffused by a slight current. 



