XXVI INTRODUCTION 



flowers themselves. In some cases the anthers were ripe 

 and shedding their pollen (Plate I., Fig. 3) long before the 

 stigma was open to receive it, and by the time the stigma 

 had opened the anthers were withered (Plate I., Fig. 4). 

 Of what use could an insect be to transfer the pollen from ripe 

 stamens to a hard green stigma ? And of what avail was its 

 presence in a flower where the stigma was freshly prepared 

 to receive pollen but where the anther sacs were empty ? 

 All that Sprengel's idea lacked was "wings"; the insects did 

 brush the pollen from the anthers, but they had to fly to 

 another flower of the same species to find a welcome for it. 

 Thus Sprengel's great work lay unnoticed till Darwin, on 

 reading it nearly one hundred years later, divined the whole 

 truth, namely, that the reason many flowers were so con- 

 structed that they could not fertilise themselves was because 

 they could be better fertilised by pollen from other blossoms 

 of their kind. That insects played an important role in the 

 transference of this pollen was evident. 



When Darwin in his "Origin of Species" stated that no 

 higher plant could fertilise itself for a perpetuity of generations 

 without a cross with some other individual, he called up on 

 himself a shower of blame and abuse for propounding such a 

 doctrine without giving ample facts ; for the botanical world 

 at large held the opinion that when the stamens were so 

 admirably set around the stigma it would be a waste of good 

 logic to argue that the pollen did not fertilise its own flower. 

 Had not Sprengel showed that the insect, attracted by 

 markings and spots, perfume and honey, brushed the pollen 



