26 R. A. EMERSON 
no red. Moreover, the dying of the lower leaves due to excessively dry 
soil, or of the upper leaves from intense heat, is not accompanied by the 
development of red pigment. 
In similar tests with cuttings of Tradescantia viridis and T. lockensis 
grown in distilled water, in complete nutrient solutions, and in solutions 
each lacking one nutrient element, namely, N, P, K, Ca, Mg, or S, 
Czartkowski (1914) found that after five weeks red color appeared in 
the newly developed leaves in the cases of only distilled water and nitrogen- 
free solutions. He states, however, that Susuki reported a similar effect 
on plants of Hordeum from a lack of phosphorus. It will be recalled 
that in the writer’s tests with maize, lack of nitrogen gave the most pro- 
nounced effect and lack of phosphorus induced considerable color develop- 
ment, while lack of sulfur seemed for a time to have an effect but no 
effect was apparent later. 
From the results of the tests reported above, it is apparent that the 
reddening of young plants in flooded fields, as well as the intensification 
of color in older plants grown on poorly drained heavy soils, is not due 
to any direct effect of the excess of water in the soil or to a direct effect 
of the somewhat lower temperatures accompanying such conditions, but 
rather, perhaps, to the lessened fertility of cold, wet soils or to inability 
of the plant to obtain adequate nutrients under such conditions. An 
excess of water not only may remove certain nutrient salts from the soil, 
but also may prevent or greatly check nitrification. Moreover, under 
these conditions the soil solution is probably less concentrated. The 
reddening of young plants in cold, wet soils in spring, the greater develop- 
ment of color in plants maturing in the cool weather of late autumn, and 
the excessive development of red in plants on very light sandy soils, are 
possibly all due to the plants’ inability to get from such soils an adequate 
supply of nutrient salts, particularly of nitrates. 
RELATION OF CARBOHYDRATES TO COLOR 
Several authors, notably Wheldale (1911), have discussed the relation 
of sugars to the production of anthocyanins in plants. Knudson (1916: 
24, 62) found that maize and vetch grown in nutrient solutions containing 
certain sugars developed markedly more red color than did plants grown 
in sugar-free solutions. The writer has observed repeatedly an apparent 
relation between an excess of carbohydrates and the development of red 
