THE GENETIC RELATIONS OF PLANT COLORS IN MAIZE! 
R. A. EMERSON 
Under the designation ‘ plant colors” are included the colors other than 
those related to chlorophyll, commonly seen in, but not limited to, such 
external plant parts of maize as the culm, the staminate inflorescence, 
the husks, the leaf sheaths, and to some extent the leaf blades. In con- 
trast to this group are colors and color patterns related to chlorophyll or 
associated with the pericarp and the cob, the silks, the endosperm, the 
aleurone. The colors included in the group considered here are due to 
water-soluble pigments, but the same is true of some of the other color 
groups named above. Moreover, colors of the chlorophyll group (Lind- 
strom, 1918) are found in the same plant parts as are the “ plant ” colors 
considered in this account. The plant colors as a whole are closely 
interrelated, but they are closely related also to aleurone colors and to 
certain of the silk and pericarp colors. It is obvious, therefore, that, 
while this classification is a more or less natural one, it is based primarily 
on convenience. 
The term “ genetic relations ”’ in the title to this memoir is to include 
not merely an account of the genetic analysis of the material at hand by 
means of hybridization experiments — tho that constitutes the greater 
part of the paper — but also some consideration of the variations of the 
several color types induced by or associated with environmental diver- 
sities. Some little attention to matters of this kind was made necessary 
by the fact that presumably homozygous material exhibited marked 
variations in extent and intensity of pigmentation when grown under diverse 
conditions. Since, as will be apparent later, the principal differences 
between certain of the color types under investigation are apparently 
quantitative ones, and since the materials at best exhibit no little complex- 
ity with respect to factorial interrelations of a genetic nature, little progress 
could have been made without some notion of the response of particular 
color types to certain factors of the environment. But this study has 
1 Paper No. 78, Department of Plant Breeding, Cornell University, Ithaca, New York. 
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