PLANT-BREEDING 319 
these plants, therefore, selection may be able to develop 
a race remarkably free from this particular disease. This 
method of combating disease may sometimes prove more 
effective than any attempt to save the plants that are sub- 
ject to it. 
The story of the development of the best-known varie- 
ties of cultivated plants is a very interesting one, telling 
how promising varieties have been discovered, and with 
what wonderful patience they have been developed into 
usefulness. The recent great increase in knowledge of the 
principles of plant-breeding has made the development of 
desirable varieties more definite and rapid than it has ever 
been before. 
