CHAPTER SEVEN 



THE IMPROVEMENT OF CROP PLANTS 



Whoever makes two blades of grass grow on a spot of ground where 

 only one grew before deserves well of mankind. 



JONATHAN SWIFT 



THE term " plant improvement " does not refer to 

 the improvement that is made by giving the crops better 

 care and richer soil. It refers to the development of 

 better varieties which, with equally good care and soil, 

 will yield more profitable crops than the old varieties. 



Improved The fine mellow apples which we enjoy today are 



fa^' le known to be descended from very different apples that 

 were cultivated by the Romans. Those earlier apples 

 grew in clusters instead of singly, and they were very 

 small. Pliny, the Roman naturalist, describes them 

 as being sour enough to take the edge off a knife. Both 



The potato; the potato and the tomato as found growing in America 

 when Europeans came were much inferior to those we 

 now have. The wild types of both of these still grow in 

 South America, and they are scarcely fit for human 

 food. Figure 68 shows the wild tomato from which 

 the cultivated varieties have been derived. It grows 

 \ under almost desert conditions and abundantly bears 

 fruit of the size of a marble. 



Methods Seed selection and plant breeding. It is not only 



interesting but it is important for us to. know the methods 

 by which improvements have been made in crop plants, 

 for if we know what has been done we shall be better 

 able to do our share in carrying the work of improve- 

 ment still farther. Two principal methods have been 



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