No. 613] SHORTER ARTICLES, DISCUSSIONS, REVIEWS 59 



heritance to know which of the aleurone factors is concerned in 

 tbifl linkage. This may be determined, where the inhibitory 

 factor I is not concerned, by crossing plants grown from either 

 colorless waxy or colorless corneous grains taken from families 

 showing linkage with plants that are homozygous recessive in 

 turn for one of the aleurone factors and homozygous dominant 

 for the remaining factors. Plants of this nature were available 

 in Professor Emerson's aleurone testers. 



At least five factors are now known to be concerned with de- 

 velopment of aleurone color. They are known as the A, C, R, 

 Pr and / factors. A, C and R are necessary for the development 

 of red. The dominant Pr factor changes red to purple. That 

 the Pr factor is not concerned in this linkage is evident from 

 the fact that the linkage relation is observed in segregations of 

 colored and non-colored aleurone and waxy and corneous endo- 

 sperm regardless of whether they are purple or red, and from 

 the fact that only red aleurone seeds were used in obtaining the 

 back cross data which show the linkage. That the inhibitor is 

 not involved is inferred from the fact that the segregation on 

 the original parent ear was 195 corneous colored, 95 corneous 

 colorless, 95 waxy colored and 15 waxy colorless which is ap- 

 proximately a 3 : 1 segregation of colored to colorless aleurone. 

 The relation of the A, C and R factors to waxy endosperm re- 

 mains to be accounted for. This may be determined as stated 

 above by the use of aleurone testers, which are named for the 

 pair of factors which is homozygous recessive. The following 

 diagram explains the method of testing for these factors. 



If the C factor were linked with the factor for waxy endosperm 

 no color should appear in the F 1 from a cross between the C 

 R and A testers colored ears should be obtained. Crosses of this 

 nature were made in 1916 and 1917 with the following results: 



