676 Wisconsin Academy of Sciences, Arts, and Letters i 
ers were found in a few grains. The pea starch showed no dif¬ 
ferentially stained peripheral layer in any case. It is quite 
possible in the case of these chemically pure starches that the 
method of preparation might remove in some cases any periph¬ 
eral transition layer. 
A short treatment with iodine in aqueous solution, in the 
case of Ganna starch, leaves the peripheral layer perfectly 
white, while the inner parts of the grain stain blue. If the io¬ 
dine acts for some time, the peripheral layer gradually acquires 
a blue color. With iron haematoxylin, in starch grains of Can - 
na\j potato and wheat, this layer does not stain, while the rest 
of the grain is colored in each case. With Correns’ silver ni¬ 
trate precipitation method, these starches show no precipitate 
in this peripheral region. These differences in staining 
qualities certainly show that either chemical or physical differ¬ 
ences exist between the body of the starch grain and this outer 
layer, and as this iayer is present especially in young grains 
and in grains in the process of solution, it may be properly 
called a transition layer. 
If the exact conditions and stage of growth from which the 
starch was taken could be ascertained in every case, the expla¬ 
nation of the presence or absence of a transition layer might be 
at once apparent. If the orange-staining peripheral layer is a 
transition substance, then we should expect to find it on starch 
grains from parts of plants which are not fully developed or 
where storage of starch is going on, such as growing tubers 
and rhizomes and unripe seeds and fruits, and an examination 
of the facts leads us to believe that such is the case. As noted 
above, in the rhizome of Canna the starch grains were proba¬ 
bly still in an actively growing condition. The Comma rhi¬ 
zome was from a growing plant, and the starch grains were 
probably still immature. 
The potato was one taken from the bin, and the condition 
of the plant, at the time the tuber was gathered is, of course, 
unknown; but of a number of potatoes which were apparently 
mature, none were found in which the starch grains did not 
show the peripheral layer in the majority of cases. It may be 
