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PLANT CoLors IN MatzE 131 
It will be recalled (Emerson, 1918) that for the development of any 
aleurone color, the presence of three dominant factors, A, C, and R, 
and also of a duplex recessive factor pair, 77, is necessary. The Pr pr 
pair has no visible expression except when associated with this combination 
of the other factors, and then it determines whether the color shall be 
purple or red. So far as is now known, the plant-color situation with 
respect to complementary factors is not quite so complex. Something of 
the same sort is seen, however, in the fact that no anthocyanic pigment 
ordinarily develops except either in the presence of A and R’, 7”, or r™, 
or in the presence of A, B, and R’ R’ or r’r’. With the first of these 
combinations, the pairs Bb and Pl pl determine the particular color 
type of the purple-red series. Two of these types, purple and dilute 
purple, are modified further by Pr pr, and the intensity of their color 
depends also on the member of the R series present, r” exerting a more 
pronounced effect than R’ or 7’. One type at least, sun red, is influenced 
somewhat by Cc. With the second combination, A, B, and R’ R’ or 
r’ rv’, the pair Pl pl determines whether the type shall be purple or sun 
red. For the formation of the non-anthocyanic (flavonol) pigment, brown, 
the interaction of aa with either B or Pl is essential, and usually very 
little color develops except when both B and Pl are present. Brown is 
made more intense by the presence of r™. 
Of the factors concerned with plant colors of maize, the Aa pair is 
one of the most fundamental, since it differentiates sharply the antho- 
eyanins of the purple-red series, A B Pl, A Bpl, Ab Pl, Abpl, from 
the non-anthocyanic brown, aBPl, and the slightly brown or green 
aBplandab Pl and the wholly green ab pl. Without A no anthocyanin 
shows in either the aleurone or the other parts of the plant. A second 
fundamental pair is Pl pl, which differentiates the sun colors from those 
that develop in local darkness. Purple (A B Pl), dilute purple (A b Pl), 
and brown (a B Pl) are all able to .develop in darkness; while sun red 
(A B pl), dilute sun red (A b pl), and the slight brown sometimes seen 
in a B pl, do not develop except in the presence of light. Whether or not 
the slight brown sometimes present in ab Pl forms in darkness has not 
been determined. To the Pr pr pair is due a definite qualitative difference 
in the colors formed which is presumably associated with a difference in 
chemical composition of the pigments. In the presence of Pr aleurone 
color is purple, and with pr it is red, and a similar difference, tho not always 
