12 INTRODUCTION 



have had a great deal to do with making your own life 

 what it is. 



Plants make little stir in the world. They are silent. 

 Where they grow, there they remain. Yet they have had 

 even more to do with the making of history than kings 

 and armies have had with all their wars and commotion. 

 This is not just because men have depended upon plants 

 for food and shelter and clothing; it is not just because 

 the abundance of plants has made plenty, and the lack of 

 plants has made famine. Even more than all that, it is 

 because plants have changed. As men have changed, so 

 plants too have changed. There is a history of plant life 

 as well as a history of human life. These two histories 

 have gone along together, and each has had a great effect 

 upon the other. 



The changes in plant life have been of two great kinds. 

 First, there are those which have been caused by nature 

 alone, and the history of these changes is a very ancient 

 history. It is far older than the history of man ; it runs 

 down to to-day, and it is still going on. Men change from 

 generation to generation, and so do plants. 



The second great kind of changes in plants is found in 

 those which have been wrought by man working with na- 

 ture. The history of these changes is that of the cultiva- 

 tion of plants, and it is this kind of change which has had 

 most to do with affecting human affairs. By means of 

 cultivation the plants which now you see in the fields have 

 been derived from ancestors which, in ancient days, grew 

 wild upon the plains and in the forests. And in those 

 ancient days our own ancestors roamed over the plains 

 and through the forests. Civilization has made us very 

 different from our savage forefathers. In like manner 



