[Vor. 4 
186 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
hydrate content. Tests were therefore made for starch and 
sugar as described below. 
The material to be examined was cut into thin sections, 
consisting entirely of either lighter or darker tissue, or, in 
order to make the comparison more striking, in part of dark 
tissue and in part of light tissue. 
Starch.—Tests for starch were made by mounting the sec- 
tion in water and drawing the slide through the flame of a 
miero-burner until the drop of water began to simmer. This 
not only killed the cells, but also expelled the air from the 
intercellular spaces, thus making observation easier. A drop 
of 75 per cent alcohol and a drop of standard iodine were 
then added, after which the section was examined under the 
microscope and the amount of starch noted. In general, it 
may be stated that whenever cells of the same section com- 
posed of different leaf areas, or cells of the same section 
representing adjacent differentiated areas were compared, 
there was an excess of starch in the dark green tissue. When 
testing for starch in the manner described, one cannot mis- 
interpret the observations. It would be aside the point to 
offer the criticism that the difference in starch content may 
be attributed to the location of the tissue tested in different 
parts of the plant, to a probable shading of one tissue and 
not the other, to a difference in the age and therefore a dif- 
ference in the storage and in the photosynthetic activity, or 
to other environmental factors. Any difference exhibited in 
cells of the same section representing different areas must 
be due to factors inherent in the tissue. This excess of starch 
in the green tissue was noticed regardless of the time of day 
when tests were made. 
Woods (’02) cites an experiment which led him to conclude 
that starch was not translocated readily from the chlorotic 
areas, and attributed this fact to the inhibitory action ex- 
erted on diastase by oxidizing enzymes. The leaves were 
picked early in the morning and tested for starch by im- 
mersing in boiling water for one minute, decolorizing with 
alcohol, treating with iodine solution, and examining by trans- 
mitted light. A darker color, presumably, was assumed by 
