PLANT Contors IN MaAtIzE 71 
with dilute sun reds are listed in table 34, group 2. These progenies 
consisted of four color types, weak purple, weak sun red, dilute purple, 
and dilute sun red, in the numerical relations given below: 
Weak Weak Dilute Dilute 
Color types _ purple sun red purple sun red Total. 
Ib IIb IIIa IVa 
Mosenvedtrty sc: tcl csc. 8 481 526 460 5a 2,004 
Malema tediy tas soa.co, fo. a 501 501 501 501 2,004 
WeKENCEf.. 2. ke... es —20 +25 —41 +36 0 
The deviations from equality of the four classes expected of a dihybrid 
are so great that they would not occur by chance alone more than once 
in twenty trials, P equaling 0.05. Dr. Anderson’s notes indicate that 
there was considerable difficulty, in the case of two of the cultures, in dis- 
tinguishing dilute purple from dilute sun red. Whether this difficulty 
may account in part for the poor fit is not known. The outstanding fact, 
however, is the appearance of the four classes and no others. Since 
weak sun red is known to differ from dilute sun red by the factor pair 
B” 6, the inference is clear that weak purple differs from dilute purple by 
the same pair and by no others. The formulae assumed for the 
four color types are, therefore, A BY” Pl, A B” pl, Ab Pl, and A 6 pl, 
respectively. | | 
If the foregoing conclusion is correct, crosses of weak sun reds with 
dilute purples should give weak purples in F,; and the same four color 
classes in F2 as are noted above for crosses of weak purple with dilute sun 
red. A single cross of a dilute purple with a homozygous weak sun red 
resulted in 18 weak purple plants. Two crosses of dilute purples with 
weak sun reds heterozygous for B” 6 gave 12 weak purples and 11 dilute 
purples. That the production of weak purples in these crosses was not 
due to the 6 or Pl factors of the dilute purple parents is evidenced by the 
fact that crosses of the same dilute purple individuals with sun reds 
gave full purples in F;. One of the F; weak purples, A A BY 6 Pl pl, 
of the above crosses was backcrossed with dilute sun red, A b pl, with the 
result (table 34, group 3) shown below. The expected equality of the 
