No. 531] THE GENOTYPE HYPOTHESIS 



173 



pare only the F 2 generation of cross of which the F, 

 generation is given. If this were granted our conclu- 

 sions in regard to segregation would be the same. It 

 might be said, however, that sufficient records were made 

 of the F x generations of the other crosses to know that 

 they differed but little from the family of which the data 

 were recorded. In addition, it is a fact that general 



? K P K P 



populations of the two parents were studied, and their 

 variation was undoubtedly greater than would have been 

 that of the inbred progeny of the three parent plants 

 of either variety. 



An additional cross between Tom Thumb pop maize 

 and a small purple flint is illustrated in Fig. 6. The ears 

 pictures show the average size of the two parents and 

 the Fj generation, and extremes of the F 2 generation. 



In conclusion there are two points I wish to notice. 

 Unquestionable segregation in size characters has been 

 shown by comparison of the F t and F 2 generations. It 

 can scarcely be doubted that some of these segregates 

 will breed as true as the parent forms, yet one can 



