" 
28 R. A. Emerson: 
masking effect of the green color, is not known. Certainly red pigments 
develop first in the chlorophyll-free epidermal cells.? 
Czartkowski (1914) suggested, in connection with the account of his 
study of the relation of nutrient elements to color development, that 
lack of nitrogen may check protein synthesis, thus leaving unused the 
carbohydrates that would otherwise be used in growth, and that the 
excess of carbohydrates may favor anthocyanin formation. He was 
unable to understand why a lack of phosphorus or of sulfur did not like- 
wise influence color development, since these elements also are necessary 
to protein synthesis. Lack of phosphorus does apparently bear some 
relation to color development in maize, but the writer’s tests afforded 
little or no evidence of such a relation between a lack of sulfur and pigment 
formation. If lack of nitrogen induces anthocyanin formation thru the 
checking of growth, thus allowing an accumulation of carbohydrates, it 
is not clear why other means of checking growth, such, for instance, as 
dry soil, do not also favor pigment formation, unless these other growth- 
checking factors at the same time limit photosynthetic activity. It is 
of interest to recall in this connection that plant colors of maize — brown 
no less than the red-purple series — develop first in the older parts where 
growth first ceases, such as the lower sheaths and the upper parts of the 
internodes of the culm. 
SUMMARY 
Whatever is the final outcome of studies of the relation of environmental 
factors to plant-color development in maize, enough has been noted to 
indicate a very complex relation. What is more complex than this chain 
of events — a chain that lacks many links in the way of particular chemical 
reactions: cold, wet soil checks or inhibits nitrification; lack of nitrogen 
in available form limits protein synthesis, which in turn allows an accumu- 
lation of carbohydrates; an excess of carbohydrates favors anthocyanin 
formation. The result is that young maize plants in cold, wet. soil 
become highly colored. But to all this must be added the factor of 
sunlight, without which no red color develops in the leaves of young 
plants. And not the least consideration is the important fact that only 
plants of certain genetic constitutions show this color reaction to wet 
soils. It is to be hoped that some day, thru the coordinated efforts of 
2 The histology of color development of the several planiecolcn tvpes has been investigated by Dr. E. G. 
Anderson, but the observations have not been published. 
