LUTHER BURBANK 



cherries, pears, walnuts, and perhaps chestnuts, 

 which are resistant to blight. 



Because of the value to be secured from crops 

 which need not be rotated, too much emphasis 

 cannot be placed upon the importance of develop- 

 ing new plants for this purpose which are resistant 

 to the various pests. 



It will almost always be found that in fields 

 badly affected with some disease or insect there 

 are one or more plants which are not affected as 

 seriously as the rest of the crop. By selecting such 

 plants and perpetuating them by seeds or division, 

 a new variety may eventually be produced that is 

 resistant to the particular disease or insect which 

 caused the damage. 



If resistant plants were developed many old 

 field and garden soils which have become worth- 

 less for certain plants could be made to produce 

 profitable crops. Such soils are quite often thor- 

 oughly infested with numerous insects and diseases 

 and the failure of crops is due more to this than 

 to the lack of proper chemical elements. 



It is possible to get resistant varieties of vege- 

 tables, grains, flowers, and trees and the process is 

 the same in all cases. 



Nature practices rotation of crops in the forest. 

 A forest of hardwood trees is almost always re- 

 placed by soft wood trees. After these have grown 



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