144 The Flower 



all the flowers had to offer insects would soon learn 

 that no food was to be had there and would not come 

 again. Food is, however, supplied in the shape of 

 pollen which bees use to make bread for their young, 

 and, besides this, many of these flowers bear a store of 

 honey right down inside the corolla. Insects come for 

 the honey, and, while they are sucking it, brush against 

 the stamens, and carry away some of the pollen dust on 

 their heads when they go. When they visit the next 

 flower some of this pollen will probably be knocked off 

 on to the top of the pistil which is made sticky on 

 purpose to hold it. In this way insects of all sizes, or 

 even, in the case of tropical flowers, tiny humming 

 birds, fly from flower to flower unconsciously fertilising 

 them in return for the honey they give. 



The wind is, of course, a far less certain fertilising 

 agent than are these insects. It will blow the pollen 

 off flowers and will carry it away in the air and scatter 

 it in all directions. Therefore besides being very light, 

 the pollen of such flowers must be produced in enormous 

 quantities, for, although some of it will fall on other 

 flowers, a great deal will be wasted. Pine trees show 

 this very well, and in some places where forests of them 

 grow such a cloud of pollen falls in spring as quite to 

 colour the ground and make the country people think 

 there has been a sulphur shower. In flowers fertilised 

 by the wind the pistil is often branched or hairy so that 

 it will hold the pollen that is blown on to it, and the 

 calyx and brightly coloured corolla which in our first 

 class of flowers served to protect the pollen and to 

 attract insect visitors, are found to be absent. They 

 would be not only useless but in the way, since they 

 would keep the wind off. That is why many tree flowers 



