Hutchison: Heritable Characters of Maize 



LATERAL VIEWS OF SHRUNKEN AND NON-SHRUNKEN KERNELS FROM 



A SINGLE EAR 



The two rows at the left are non-shrunken kernels; in the middle two rows the indentation is 

 from the sides of the kernels, and in the two rows at the right the indentation has taken the form of 

 a deep crease. The latter character is shown better in the kernels in the centre of Fig. 24. (Fig. 23.) 



the C c and Sh sh factor pairs. A homo- 

 zygous red aleurone shrunken plant of 

 the genetic constitution C C sh sh was 

 crossed with a colorless aleurone non- 

 shrunken plant of the constitution c c 

 Sh Sh. An Fi plant of this cross, grown 

 in the greenhouse during the winter of 

 1918-19, was selfed giving a small F2 

 progeny. On this ear shrunken and 

 non-shrunken kernels were found as 

 well as colored and colorless but all of 

 the shrunken kernels were also colored. 

 This clearly indicated that the Sh sh 

 and C c factor pairs are linked. To 

 definitely establish the fact the writer 

 in 1919 made a number of backcrosses 

 between Fi plants and the double 

 recessive. Twenty-eight such back- 

 crossed ears gave progenies totaling 

 8,326 kernels distributed as follows: 



The parental combinations of the 

 characters concerned in this cross are 

 in great excess, there being 8,041 

 kernels of these combinations and only 

 284 of the other two. This is very far 

 from equality which is expected with 

 independent inheritance. It is evident 

 that the factor pair Sh sh belongs to the 

 same linkage group as C c and Wx wx, 

 with a crossover percentage in this 

 case of approximately 3 . 4 for Sh sh and 

 C c. In Figure 21 two such backcrossed 

 ears are illustrated. It will be noted 

 that most of the colored kernels are 

 shrunken and most of the colorless ones 

 are smooth. A few kernels of the 

 opposite combinations, however, are to 

 be found on each of these ears. 



The ear on the left in Figure 22 illus- 

 trates the coupling series of these two 

 factor pairs. In this case the parental 

 combinations were C Sh and c sh. This 

 ear is the result of pollinating an Fi 



