No. 518] 



VARIATION 



67 



Fully fifteen different yellow varieties of maize have 

 been crossed with various white varieties, in which the 

 crosses have all given a simple mono-hybrid ratio. In the 

 other cases that follow it is seen that there is a di hybrid 

 ratio. 



No. 5-20, a pure white eight-rowed flint, was pollinated 

 by No. 6, a dent pure for yellow endosperm. An eight- 

 rowed ear w T as obtained containing 159 medium yellow 

 kernels and 145 light yellow kernels. The pollen parent 

 was evidently a hybrid homozygous for one yellow which 

 we will call Y x and heterozygous for another yellow Y 2 . 

 The gametes Y t Y 2 and Y l fertilized the white in equal 

 quantities, giving a ratio of approximately one medium 

 yellow to one light yellow. The F 2 kernels from the dark 

 yellow were as follows : 



Table I. 3 



F 2 Seeds from Cross of No. 5-20. White Flint X No. YELLOW Dent. 

 Homozygous for T, and Heterozygous for F s 

 Dark Seed* II <t croriianns for f-lnth Ytllows Planted 



The ratios of light yellows to dark yellows is very arbi- 

 trary, for there was a fine gradation of shades. The ratio 

 of total yellows to white, however, is unmistakably 15 : 1. 



In the next table (Table II) are given the results of F 2 

 kernels from the light yellows of F x . Only ear No. 8, 

 which was really planted with the dark yellows, showed 

 yellows dark enough to be mistaken for kernels containing 



