THE PROBLEM 41 



fully into the characters which distinguish the 

 Angiosperms, so that we may be better able to 

 compare them with other classes of plants. 



The first great characteristic of Angiosperms 

 is that they alone, among plants now living, 

 possess true flowers. What is a flower? In 

 ordinary lif e our idea of a flower is associated with 

 bright colour and often with a sweet scent. 

 But we now know that colour and scent are not 

 there merely to give pleasure to us, but that they 

 are of important service to the plant, by attract- 

 ing the visits of insects. Sometimes, in fact, 

 neither the colour nor the scent is by any means 

 pleasing to ourselves, for they, may serve to attract 

 such insects as carrion flies, which have very 

 different tastes from our own; this is the case 

 in the Rafflesia, mentioned above, and many 

 of the Arum family. The visits of insects (and 

 in a few cases of other animals, such as Humming- 

 Birds) are chiefly of use to the plant, as Darwin 

 showed, by bringing about cross-fertilisation 

 between different flowers or different individuals. 

 In other words, a typical flower is an organ of 

 sexual reproduction, adapted to crossing by means 

 of animal visitors, especially insects. The nu- 

 merous cases in which the "short circuit" method 

 of self-fertilisation has been resorted to, do not 

 affect the main conclusion, for in many of these 

 cases the flower has evidently once been adapted 



