PLANT Coors IN MAIZE 67 
Interrelations of sun red IIa, weak sun red IIb, and dilute sun red IVa 
Numerous crosses of weak sun reds, IIb, with dilute sun reds, IVa, 
have given weak sun reds in F; and approximately three weak sun reds 
to one dilute sun red in F», just as crosses of strong sun red with dilute 
sun red give three strong to one dilute sun red (table 24, group 1, page 138). 
Records of such crosses are given in table 32 (page 144). Twelve Fy, 
progenies, totaling 1729 individuals, showed the two types in the relation 
1300:429, almost exactly a 3:1 ratio, the deviation being 3.3 + 12.1. 
The data for F; of these crosses are like those for crosses of strong sun red 
with dilute sun red (table 25). One weak sun red F:, bred true in F3 
with a total of 77 weak sun red offspring (table 33, group 1). Four others 
gave both weak and dilute sun reds (group 2), in the relation 128:54, a_ 
deviation of 8.5 + 3.9 from a 3:1 ratio. One dilute sun red bred true 
(group 3), with 95 dilute sun red plants in F;. 
A cross of weak sun red, IIb, with strong sun red, Ila, gave strong sun 
red in F, and the two parent types in F2 in the relation 71:16, a deviation 
from the 3:1 ratio of 5.75 + 2.72. There is, therefore, nearly one chance 
in six that the cbserved deviation may be due to errors of random sampling, 
P equaling 0.16. : 
In none of these crosses, strong with weak, weak with dilute, and strong 
with dilute sun red, have other than the parent types appeared in F%. 
If weak sun red is due to the action of some additional modifying factor, 
not heretofore considered, types other than those of the parents should 
have occurred in some of the crosses. The natural conclusion, therefore, 
is that weak sun red, IIb, is due to an allelomorph of B and b, the pair 
concerned with the difference between sun red, Ila, and dilute sun red, 
IVa. This third allelomorph, responsible for weak sun red, may well be 
designated B”. 
Further evidence in support of the assumption that an allelomorph of 
B and 6 is concerned with weak sun red is afforded by linkage studies 
involving strong, weak, and dilute sun red with leaf type. Evidence has 
been offered (page 63) to show that Bb and Lg lg are linked with about 
30 to 33 per cent of crossing-over. 
A single progeny, 8252, from a sun red plant heterozygous for leaf type 
and plant color backcrossed to liguleless weak sun red, contained 108 
sun red and 109 weak sun red plants. Of the normal-leaved plants 80 
