xv STEUGGLE WITH DISEASE 179 



Then we saw that, partly as a more or less 

 unconscious result of cultivation, and partly by 

 deliberate effort, man has been, and is, improving 

 his plants, so that they become better fitted for 

 new countries, so that they produce more and more 

 abundantly. But this is not nearly all ; we have 

 still to consider what is in some ways the most 

 interesting point about the cultivated plants the 

 desperate struggle man has had to wage with plant 

 diseases. 



We have seen already what wonderful things he 

 has done. He has toiled continuously to wrest her 

 secrets from Nature, and, with every problem he has 

 solved, he has become more skilful in bending her 

 to his will. But it is not an easy task, and every 

 now and then Nature takes her revenge on a big 

 scale. Man brings the potato from America to 

 Ireland, where wheat grows badly because of the 

 damp climate. Here the potato grows abundantly, 

 and becomes the staple diet of many of the people. 

 Then Nature rebels, and sends a deadly disease ; the 

 potatoes are blackened and destroyed, and thousands 

 of people are brought suddenly within sight of 

 starvation. 



For thousands of years man grows the vine 

 superbly in the sunny parts of Europe, until the 

 skill of the cultivators becomes a proverb, and the 

 wine is world-famous. Then an insignificant little 



