34° BOTANICAL GAZETTE [NOVEMBER 
of the leaf-blade, and in the cortex of stem and petiole. In 
26 cases of loss, the conditions had changed since spring from 
sunny to shady. This would make it seem as if red might be 
a protection from intense sunlight, but in 28 cases of appearance 
of color 13 were found in conditions which had changed from 
sunny to shady, and 5 were found in conditions which had 
changed from wet to dry. One might conclude that change of 
conditions favors change in color, from green to red or red to 
green, as has been asserted by others. 
Most of the plants with red color were gathered in dry 
sunny places. This does not accord with observations of Stahl, 
who finds in moist or shady places the most noticeable red col- 
oring. His theory does not seem applicable to the facts just 
given, for the conditions of sunlight and warmth in this case 
favor photosynthesis and conduction, also transpiration. The 
percentage is so large it could not be due to collecting more 
specimens in the spring or fall, when the temperature is lower, 
and thus be due to increased sugar concentration according to 
Overton’s theory. 
Taking the whole number of cases, the red color gives the 
largest percentages for stems and petioles, really the conducting 
parts of the shoot. One might think with Stahl that some 
advantage is derived from red color in photosynthesis and pas- 
sage of food material, but again why this is needed in most of 
these cases is not so clear, since conditions were already suffi- 
ciently favorable for transpiration, etc. The large amount of 
color in the cortex seems to favor Stahl’s theory also. If we 
apply Pick’s theory, that the red color protects the conducting 
parts from the injurious effects of light upon the changing sub- 
stances in them, we seem to have a strong argument in its favor, 
for the majority of the cases noted were recorded in dry, sunny 
places. 
In wet shady places only is the percentage of cases of red _ 
color in the leaves greater than in the stems and veins. In 
Stahl’s paper most attention is paid to color in leaves, so here is 
an agreement, if only a slight one, with his theory of the need 
of warmth to increase transpiration. 
UR eR I AIRoCtreRe ne none. 
