688 Wisconsin Academy of SciencesArts, and Letters. 
41), and on these corroded surfaces there appears an orange- 
staining area in which no lamination whatever is present, com¬ 
parable in this respect to the orange-stained central portion of 
the mature Canna grains already mentioned. Where the outer 
starch layers are still intact, no additional orange-staining 
substance appears. This appears to he a further hit of evi¬ 
dence that the inner portion of mature starch grains has un¬ 
dergone some change. 
SWELLING AND SOLUTION. 
If starch grains are treated with various reagents, they 
swell and give some very curious and interesting figures. It 
is a question whether the swelling caused by such reagents as 
potassium hydroxide, acetic acid, chromic acid, chloral hy¬ 
drate or hot water is due to imbibition of the reagent between 
the particles of starch substance or to molecular changes in the 
particles themselves. 
Potato starch grains treated with chromic acid (15%) show 
at first a slight enlargement of the hilum crack; then the for¬ 
mation of fine radiating cracks, arranged like the barbs of a 
feather, beginning at the hilum and extending to near the pos¬ 
terior end of the grain. Frequently this area of radiating 
lines runs part way toward the opposite end of the grain from 
the hilum and then divides, forming a V-shaped figure. 
This area spreads and draws toward the margin, and an open¬ 
ing is formed in the central part of the grain. Further, the 
grain continually increases in size till the outer layers are rup¬ 
tured. This usually takes place at a point near the hilum. 
The whole interior of the grain is dissolved out, and the layers 
at the posterior end and extending part way down the sides are 
all that remain. The limits of these layers show very sharply, 
and in some of them fine radial lines appear. 
If a potato starch grain is treated with potassium hydroxide 
(10%), a crack forms, beginning at the hilum and extending 
toward the posterior end of the grain (PI. XL, Figs 44-50). 
Xarrow radiating cracks gradually extend from the central 
crack toward the periphery. The hilum crack enlarges, and at 
