Puant Cotors IN Maize 17 
and dilute sun red plants, in which the same reactions may possibly be 
brought about thru the action of sunlight. 
Usually a single thickness of black paper, such as is employed to pro- 
tect photographic plates from light, is sufficient to prevent the develop- 
ment of color in sun red plants (Plate VIII, 4). That more intense light 
is necessary for the production of sun red pigment than for the production 
of chlorophyll is shown by the almost entire absence of red color in all 
but the outer husks, while even the innermost husks are somewhat green 
(Plate V, 3). The pigments of purple and brown plants, on the contrary, 
develop well even when there is too little. light for the formation of chloro- 
phyll (Plate VIII, 1 and 2). 
That the effect of light on color development is a definitely local one is 
shown by the sharp line of demarcation between colored and colorless 
areas in culms, husks, and sheaths partly exposed and partly protected 
by overlapping sheaths or husks (Plate V, 3). Even a single piece of 
wrapping cord tied closely about a young ear, sheath, or culm of a sun 
red plant is sufficient to prevent the development of color beneath it. 
Evidently sun red pigment does not diffuse appreciably from the cells in 
which it forms. It is not meant to suggest by these observations that 
sunlight has no effect other than a local one on color development. On 
the contrary, there is evidence that the development of sun red color is 
influenced by the presence of an abundance of carbohydrates which in 
turn are dependent on sunlight for their formation. 
A striking example of the relation of sunlight to color development is 
afforded by the barred pattern seen in the husks of some weak sun red 
plants (Plate V, 4). The pattern consists of alternate bars of red and green 
parallel to the upper margin of the overlapping husk next below them. By 
tracing in pencil on each exposed husk of a rapidly growing ear the margin 
of the husk overlapping it, it has been ascertained with certainty that the 
red bars correspond to the areas that are pushed out from under the over- 
lapping husk between early morning and late afternoon, while the green 
bars correspond to the areas pushed out during the late afternoon and 
night. Why color develops in only those parts of the husk that receive 
the sunlight when first exposed to the air, and not in the parts exposed 
some hours previously, is not known. Another illustration of the effect of 
sunlight on freshly exposed husks was seen in a very light type of weak 
sun red (Plate V, 5). Of two ears on the same culm, both very lightly 
