INTRODUCTORY 263 



from the anther to the stigma of the same flower ; this is 

 called selfwpollination or close-pollination. It may also be 

 transferred to the stigmas of other flowers; this is cross- 

 pollination. 



This cross-pollination is one of the most wonderful things 

 about plants. The thing about it which makes us wonder 

 is the way in which it is accompUshed. It is a thing 

 which the plant cannot accomplish for itself. It is a 

 thing which is accomphshed entirely outside of the plant. 

 It is a process which is essential to the perpetuation of 

 most seed plants, and yet it is a process which the plant 

 alone is powerless to accomplish. It is a process over 

 which the plant itself or the pollen itself has no direct 

 control. And yet this cross-polhnation, — this transfer of 

 pollen from one plant to another, this long movement to 

 a small and distant goal by bodies which themselves are 

 entirely without power to move, — occurs each season 

 as a regular feature of the plant's Hfe, as regular as the 

 respiration or the photosynthesis which goes on inside of it. 



There are two agencies of the outside world by which 

 principally poUen is carried from flower to flower. One 

 of these agencies is the wind; the other is insects. 



It is the fragrance and the bright colors of flowers which 

 make them conspicuous. These are the features which 

 make them attractive to us, and it is believed that these 

 features also make them attractive to insects. Many 

 flowers contain nectar, a sweet liquid which is a favorite 

 food of insects. Bees make honey of it. Some insects eat 

 pollen, and in eating it they are sure to carry some of it 

 about from flower to flower. It is believed that the odors 

 and bright colors of flowers act as signals to insects that 

 nectar or pollen may be found, and are thereby of advantage 



