76 THE EVOLUTION OF THE FLOWERS 



spread of our higher flowering trees. This is simple 

 when one learns why a tree sheds its leaves in the 

 winter. The leaves are more or less the lungs of 

 the tree. Through them it gives off moisture. In the 

 winter, however, it receives little or no moisture from 

 its roots, according to the state of the ground, and 

 the leaves are sacrificed in order to preserve the 

 moisture in the tree. Here, again, one sees the last 

 term of a long evolution. The various steps of it 

 have been lost. It may have taken place on *'the 

 Lost Atlantis." ^ In any case, when we do find these 

 "deciduous" (leaf -shedding) trees appearing in the 

 Chalk Period, we know the meaning. The earth is 

 growing colder ; winter has begun. 



But the great chill which killed the reptiles and 

 opened the reign of the birds, mammals, and flowering 

 plants melted away again like its predecessors. The 

 temperature of even the northern hemisphere rose so 

 high that magnolias, figs, and bamboos flourished in 

 Greenland, where men can now barely wrest their 

 remains from the frozen soil. Palms and aloes 

 flourished in France. Warm-loving animals wandered 

 as far north as Scotland. It was not so warm as it 

 had been in the earlier periods, and from this point 

 onward the earth becomes increasingly cooler; but 



^ I use the name fancifully for the continent which so long did 

 exist across the North Atlantic. But it disappeared before the 

 coming of man, or at least long before civilization, and there is no 

 foundation for the Greek legend of a Lost Atlantis. 



