684 Wisconsin Academy of Sciences, Arts, and Letters. 
They are highly refractive in water, and the stains are removed 
from them with greater difficulty than; from the layers which 
are not so dense. 
ANALYSIS OF STRUCTURE BY CORROSION AND SOLUTION. 
Blocks of starch-bearing tissues were taken from a rhizome 
of Canna in a region which had recently produced a vigorous 
shoot. The material was fixed, imbedded and sectioned in the 
ordinary way and Flemming’s triple stain was used. 
Many of the large eccentric grains were found still enclosed 
by pjastids and invariably showed corrosion. Where the 
plastid is thickest the corrosion of the grain appears the great¬ 
est in exrent, and frequently the broader posterior end of the 
grain beneath the thicker part of the plastid is reduced to a 
mere point (Fig. 39). Occasionally grains appear in which 
solution has taken place at both ends more strongly than in the 
middle. In such cases a spindle-shaped grain results. Fre¬ 
quently the anterior end is reduced to a point and takes the 
orange stain (Fig. 30). 
In these large eccentric grains from Caima, the corrosion 
in the plastid seems to be upon the surface of the grain only, 
andj all the layers of the grain which reach the surface seem to 
suffer from the action of the diastase in nearly the same degree. 
A slight difference in the rapidity of solution in certain la} r ers 
is noticed, however, in some preparations. The pale violet lay¬ 
ers are acted upon with the greatest rapidity. The ends of the 
dark violet layers project farther on the corroded margin than 
do the ends of the light layers (Fig. 39). 
The appearance of these corrosion channels in the wheat 
starch is similar to that of the figures which Groldschmidt has 
described as forming in CaC0 3 spheres when treated with HC1, 
as will be noted further below. 
Starch grains artificially corroded by solutions of diastase 
are more favorable material for making observations on the be¬ 
havior of the different layers of grain. If slides with sections 
of starch-bearing tissues are placed in a tube of diastase solu¬ 
tion, to which a few drops of chloroform are added to prevent 
bacterial growths, the corrosion usually takes place in two or 
