No. 604] 



LINKAGE IN MAIZE 



227 



zygOTis for as many of the non-linked factors as possible. 

 Fortunately, the plants used in this experiment were 

 homozygous for A, P and i, as will be shown later. This 

 left only C and R, giving either 3:1 or 9:7 ratios of 

 purple to colorless grains. The aleurone segregation on 

 the ear proved to be exceptionally distinct because the 

 factors A and P were homozygous. 



The other factor involved in the linkage is concerned 

 with chlorophyll development in the mature plant. It is 

 one of at least seven factors necessary for the production 

 of full, normal green color in maize, and it has been termed 

 the G factor. Its allelomorph g produces a distinct yellow 

 or golden color in the leaves and stalk of the mature corn 

 plant. This color is comparable with that of the familiar 

 golden-leaved shrubs. It has been described and its in- 

 heritance discussed by Emerson (1912) and Miles (1915). 

 Suffice it to say that it is a simple recessive to normal 

 green. 



During the summer of 1914, a green plant heterozygous 

 for R and G was pollinated by a golden plant that lacked 

 aleurone color. The cross can best be described by the 

 following factors: 



GgRrCCAAPPii ggrrCcAAPPii 

 3472 (11) " ^ 34G8 (10) ' 

 Proof for the correctness of these formulje will be given 

 later. 



A selfed ear of the female parent bore a 3:1 ratio 

 (271:88) of purple to colorless grains, showing that only 

 one aleurone factor was heterozygous. The male parent 

 was likewise selfed and -howed no aleurone color. On the 

 ear of this cross there were 67 purple and 55 colorless 

 grains, approximating a 1 : 1 ratio. 



The purple seeds on this ear were planted separately 

 from the colorless seeds. From the field counts of this 

 planting, which are given in Table I, it is seen that the 

 1:1:1:1 ratio of independent inheritance is noticeably 

 modified. 



The observed numbers in the four classes give a ga- 



