80 THE EVOLUTION OF THE FLOWERS 



cross-fertilized would have the advantage. Natural 

 selection would foster and increase every trick and 

 apparatus that led most surely to cross-fertilization. 



To work out this principle in the world of flowers, 

 and explain the wonderful variety of flower structures, 

 would require a whole large volume, or series of 

 volumes. One must consult botanical works. Here 

 we can only consider broad features of the evolution 

 of nature. One of these is that the great outpouring 

 of the flowers came naturally after the severe chill 

 had removed the large imperfectly-flowering plants of 

 "the Middle Ages," along with the monstrous reptiles 

 and other mediaeval types; and that with the expan- 

 sion of the flowers came the spread of the bees and 

 wasps and butterflies. 



You may think that flies and butterflies cannot be 

 fossilized, and so the man of science must be guessing 

 what happened millions of years ago. He often does 

 guess, though he is always careful to tell you that it 

 is only a guess, until he has found positive evidence 

 to prove that his guess was right. But here we have 

 direct evidence. Did you ever see a piece of amber 

 with a fly in it? There is a shop near the British 

 Museum in London where you can buy one at any 

 time. That fly may be two or three million years 

 old. Amber is more or less fossilized resin; and 

 ages ago the fly stuck on the resin, as it oozed from 

 the tree, and was covered over with fresh outpours of 

 resin. Then the tree died and the resin broke off; 



