RIDDLES IN FLOWERS 
207 
the solution of all these floral riddles. The insect 
explained it all. The bright colors and fra- 
grance were intended to attract him, and the 
nectar to reward him, and while thus sipping he 
conveyed the pollen to the stigma and fertilized 
the flower. 
But now Sprengel himself was met with most 
discouraging opposition to his theory, showing 
that he had guessed but half the secret after all. 
Flowers by the hundreds were brought to his 
notice, like that shown in Diagram C, in which 
the insect could not transfer the pollen from 
anther to stigma, as the stigma is closed when 
the pollen is ripe, and like that in Diagram D, 
which does not open until the pollen is shed. 
For seventy years this astonishing fact puzzled 
the world, and was at last solved by the great 
Darwin, who showed that nearly all flowers shun 
their own pollen, and are so constructed, by thou- 
