No. 604] 



LINKAGE I\' MAIZE 



{R, C, and as can be seen from their records in Table 

 VI. Plant (41) is a golden t^^e from colorless seed. 



TABLE VII 



Showing the Tests for the Presence of Aleuroxe Factors 



1. A tester (BECCaa) X 3954 (32) . 



2. C tester (REccAA) X 3954 (32) . 



3. i? tester (rrCCAA) X 3954 (32) . 



4. 3954 (34) X C tester (BEccAA) . 



5. 3954 (31) X -B tester (rrCCAA) . 



6. 3954 (41) (rrCcAA) X 3954 (31) 



450 purple 

 72 " : 69 colorless 

 7 " : 11 " 

 205 " :217 " 

 212 " :249 " 



The data in Table VII prove several things, namely : 



1. That the factors A, C and R must be present in all 

 the plants tested, because color was produced in some of 

 the Fi grains of each cross. 



2. That it is the R factor that is linked with G. This 

 is demonstrated in tlie fifth cross. Plant (31) was a green 

 plant from purple seed bearing an ear with a 3 : 1 aleurone 

 ratio, showing that it was heterozygous for the one aleu- 

 rone factor that is involved in the linkage. The test clearly 

 proves it to be the B factor, the aleurone ratio from the 

 fifth cross approximatiiig tlio theoretical 1:1 proportion. 



3. That the assiiitiptioiis made in Table V as to the 

 genot>T)ic formul.T of tlie Fj plants are correct. This 

 statement follows from a series of deductions. First, one 

 aleurone factor of the three concerned must be homo- 

 zygous (dominant) in all the plants, because the aleurone 

 ratios observed permit only two heterozygous factors at 

 the most (9:7 ratios). Since the C factor is heterozy- 

 gous in plants (32) and (34), and the R factor heterozy- 

 gous in plant (31), while A is homozygous in plant (32), 

 it is obvious that only the A factor could be homozygous 

 (dominant) in all the F^ plants. Second, one of the re- 

 maining factors {C or R) must be homozygous (domi- 

 nant) in some plants and heterozygous in others to ac- 

 count for the 3:1 and the 9 : 7 ratios, respectively. The 

 second and fourth crosses in Table VII indicate that C is 

 heterozygous in plants (32) and (34), whereas the fifth 



