PRINCIPLES AND METHODS OF PLANT-BREEDING 139 



of four or five years, interesting results are to be observed. Descendants 

 of only three or four of the original ears will be represented in the breed- 

 ing plot at the end of that time. The others will drop out. It would 

 seem that our best strains of corn descend from especially striking ancestors, 

 just as breeds of stock or single herds contain almost exclusively the blood 

 of some exceptional progenitor. It would take many years to accomplish 

 such a result by mass selection. Mr. Reid spent practically his whole 

 lifetime in producing the Dent corn which bears his name. He might 

 have accomplished his purpose in much less time had he practiced individual 

 selection. 



The method of individual selection can be applied to any crop; the 

 principle is always the same. Some unit, such as head, plant, or tuber, 



FIG. 79. Harvesting individual rows of oats 



is taken as the basis, planted in such a manner that the comparison of 

 the individuals may be easy, and the seed kept separate (Fig. 79). It 

 is true that difficulty arises with some plants, such as corn, because of 

 cross-pollination. This difficulty is not serious from a practical stand- 

 point and is not to be considered in many of our crops, such as oats, wheat, 

 rye, barley, peas, beans, potatoes, and other plants that are either self- 

 fertilized or are propagated by cuttings. A leading authority on plant- 

 breeding has said that, as far as our cereals are concerned, there are enough 

 different types, already existing, to supply almost any demand that may 

 be made. It is unnecessary to resort to hybridization. It is only necessary 

 to examine a large enough number of individuals to find the desired one. 



