PLANTS AND MAN 
transplanted to far continents through the mistaken idea 
that they would be a help against insect pests. Rabbits 
were introduced into countries where they had never 
existed and became destructive to cultivation. 
Finally man has created new varieties of fruits and 
vegetables and flowers. Since plants play a highly im¬ 
portant role in the feeding of man and domestic animals, 
great energy and much money are devoted to research 
in agriculture, horticulture, and silviculture. We cannot 
imagine how far-reaching the changes in plant life may 
be, as a result, in the course of the next few centuries. 
Human population is steadily increasing, and starvation 
will ultimately face the human race if it is unable to 
increase its food supply in proportion. If a new glacia¬ 
tion should occur, however, all our calculations would 
be upset and man would probably be impotent against 
the superior power of Nature. 
There is no rest or standstill in the march of evolution, 
and the plant world will change as it has always changed 
in the course of the past hundreds of millions of years. 
Compared with this march of events in a well-nigh endless 
time, our own human observation seems infinitely small. 
Just as astronomy gives us a glimpse of boundless space, 
so the history of the earth and of its flora and fauna 
opens before us a vista of the boundlessness of time. 
115 
