No. 604] 



LINKAGE IN MAIZE 



231 



suits correspond with the theoretical when a linkage on a 

 4 : 1 basis is assumed. Considering only the classes from 

 purple seeds (first two columns in Table IV), the agree- 

 ment is perfect. These classes are not disturbed by the 

 aleurone situation and consequently ought to show the 

 gametic ratio directly. 



Determination of the Aleurone Factor concerned in 

 THE Linkage 



It has been shown from four independent sources that 

 the G factor is linked with one of the five aleurone factors, 

 which has been termed the R factor. It now becomes nec- 

 essary to prove that it really is the R factor that is in- 

 volved. From the aleurone ratios observed in this ex- 

 periment, &s well as from evidence from related plants, it 

 is certain that the inhibiting factor I is lacking, with the 

 exception of the last cross described (Table IV). It is 

 also obvious that the P factor, which produces purple 

 color when C, R and A are present, must be homozygous 

 (PP) in both parents of the first cross since the color in 

 the colored grains is a deep purple with no trace of red. 

 This leaves only C, R and A to be considered. 



In order to facilitate the presentation of the proof that 

 the R factor is the one concerned. Table V has been pre- 

 pared. In this table, the zygotic formulae of the F^ plants 

 of the first back cross (see Table I) are listed and the 

 plants that were tested are noted in the last column. The 

 factors are merely assumed as here given. 



TABLE V 



X 3468 (10) 

 Parental Formulce: GgRrCCAA X ggrrCcAA 









GgRrCCAA . 

 GgRrCcAA 

 ggRrCCAA . 



ggRrCcAA 



GgrrCCAA 1 



GgrrCcAA 1 



ggrrCCAA 

 ggrrCcAA 1 



Purple 





( I Wo) (11) (31) (83) 

 ] iL'l . m) (29^, (43) (45) 



