Neo-Mendelism 79 



two extreme parent types in the hope of obtaining a 

 hybrid combining the desirable characters of the two 

 parents. If the material is corn, he might use one 

 parent with large grains but few in number, while the 

 other parent has many grains but small ones. Such 

 quantitative characters as these would be determined 

 by cumulative factors, and the hybrid would be inter- 

 mediate in respect to both of these characters, that is, 

 the grains would be of medium size and medium number. 

 No matter how many crosses he made, he would always 

 get this result and not the desired combination of large 

 grains and many of them. 



Suppose now that these intermediate hybrids are 

 inbred in the hope of obtaining the desired combination 

 in the F2 generation. It will be realized that the chances 

 of obtaining a plant combining the two extreme char- 

 acters of large grains and numerous grains would depend 

 upon the number of factors that enter into the make-up 

 of these quantitative characters. Assume that there are 

 five factors in each case. The mathematics of the situa- 

 tion would show that in order to get the desired pure 

 type from a cross between two parents, each having 

 their desirable character determined by five cumulative 

 factors, it would require 100 acres of corn to have an 

 even chance of getting one such individual in the Fj 

 generation. It is altogether unlikely that any farmer 

 would use 100 acres and a corresponding amount of labor 

 on such an extreme chance. Even if he did, it would be 

 very problematical whether he would be able to select 

 the proper solitary individual on his 100 acres. Even 

 an agricultural experiment station would not feel justified 

 in conducting such an experiment. 



