

4 
LINDSTROM, GENETICAL RESEARCH WITH MAIZE aoe 
factors is the Zi pair, the dominant factor J being an inhibitor that sup- 
presses all color no matter if all the dominant color factors are present. 
The genetic formulae for aleurone color can be expressed as follows: 
Purple — AA CC RR PrPr u 
Red — AA CC RR prpr ü 
Colorless — AA CC RR PrPr II 
RAA CC err PrPr ü 
SAA co RR PrPr u 
— aa CC RR PrPr u 
— any other combination of Aa, Cc, kr, Pr, pr, and An 
For example any of the following genotypes when selfed give 3 : 1 ra- 
tios of colered: colorless grains, Aa CC RR (Pr Pr or pr pr), AA Cc RR, 
or AA CC Ry. Ratios of 9 colored to 7 colorless obtain when Aa Cc RR, 
AA Cc Rr, or Aa CC Rr are selfed. When a plant that is heterozygous 
for all three fundamental factors Aa Cc Rr is selfed the progeny consists 
of 27 colored: 37 colorless grains. The colored grains are purple or red 
according to the presence of Pr or pr. (Emerson 1918). 
The presence of the inhibiting factor in a heterozygous condition 
produces many peculiar ratios. The actual reality of the different color- 
less aleurone genotypes (4 Cr, Ac R,aC R, etc.), has been proven by 
extensive tests. Crossing of two pure white varieties gives purple aleu- 
rone color under certain and predictable circumstances. 
In addition to the five factor pairs noted above there are at least six 
others that exert secondary effects, such as mottling, intensification, 
stippling, blotching, and other pattern effects. An interesting pheno- 
menon is shown by the Ry factor pair. When RR is pollinated by 
vvé the aleurone color is fully developed if the other necessary factors 
are present. However when À comes in from the pollen (772 x RR 8), 
giving an endosperm nucleus of vrR, it seems that this single dose of R 
is not capable of developing full color but instead a mottled or partial 
development of color is produced. 
Endosperm color. — Belonging to the endosperm proper (not inclu- 
ding the aleurone layer) is another series of colors. These are the yel- 
lows and white, a system that is entirely independent of the aleurone 
colors. That is yellow endosperm color may or may not be covered by 
purple aleurone color. 
There is one fundamental or common factor pair (Yy) controlling 
