76 SCIENCE PRIMERS, [xx. 



XX. -FERTILIZATION. 



117. Though stamens and pistil frequently occur in 

 the same flower, it does not follow that the pistil of 

 such a flower is fertilized by its own stamens. On 

 the contrary, it has been proved by many careful 

 observations and experiments that nature has pro- 

 vided that pistils should be fertilized by pollen from 

 other flowers, or from the flowers of other plants. 

 Hence some plants bear stamens and pistils on 

 separate flowers of the same individual (oak, hazel); 

 others have stamens and pistils on different individuals 

 (willow) ; in others again, when stamens and pistil 

 occur in the same flower, they do not become mature 

 at the same time; and in still others, when stamens 

 and pistil do occur in the same flower and are mature 

 at the same time, they are so placed in reference to 

 one another or to the corolla &c., that the pollen 

 cannot reach the pistil. 



1 1 8. It has also been proved, that, as a rule, a pistil 

 fertilized by the pollen of another flower, or that of 

 another individual of its own kind, produces more and 

 larger seeds which grow into stronger plants, than if 

 it had been fertilized by the pollen of its own flower. 



119. These and many other observations tend to 

 prove that the elaborate structures, colours, scents, 

 honeyed secretions, and other attractions of the corolla, 

 stamens and pistil, and their adjustments to one 

 another and to the forms and habits of insects, are all 

 intended to prevent flowers from being fertilized by 

 their own pollen, and to facilitate their being fertilized 



