Denniston—Growth and Organization of the Starch Grain. 685 
three days if the temperature isi kept at about 40° C. The 
principal difficulty in the use of this method lies in the loss of 
sections in the diastase, but usually a sufficient number remain 
to give a few corrosion figures. 
The large eccentric grains of Ganna (PL XXXVIII, Pig. 
28), treated in this manner for two days, show a strongly mark¬ 
ed peripheral orange layer except for one or two small areas, 
usually on the posterior end. The conspicuous outer dense lay¬ 
ers have been dissolved in a number of spots, but remain fairly 
intact. Considerable substance has been removed from the in¬ 
terior of the grain, and parts remaining in the interior of the 
grain quite generally take the orange stain (Figs. 26, 27). 
In some cases, the inner portions of the Ganna grain have been 
completely dissolved and there remains only a shell made up of 
parts of the outer violet layers (Fig. 29). 
The highly refractive layers in the unstained grain contain, 
as we have seen, a relatively small amount of water, and these 
are the layers which would naturally be expected to: be most re¬ 
sistant to the action of diastase. We have found that in some 
cases the refractive layers of the unstained grain are not homo¬ 
geneous but consist of a number of layers. Some of these com¬ 
ponent layers take a deeper and some a paler color. Evidence 
of the same condition is found in corroded grains, and in every 
case the parts which are stained most deeply with gentian vio¬ 
let are least acted upon by the diastase. 
In oval starch grains from germinating wheat and barley 
which are enclosed by the plastid and which show the effect of 
diastase action, the corrosion 'does not take place evenly around 
the periphery, but peculiar pits and canals are formed begin¬ 
ning at the periphery and extending irregularly into the cen¬ 
ter of the grain. 
In the later stages of corrosion there seems to be a tendency 
on the part of the corrosion channels to follow concentric lines 
in the interior of the grain. An effort was made to learn 
which layers were most attacked but without success. The in¬ 
terior of the grain takes an almost uniform stain after diastase 
action has gone on for some time. In the earlier stages of 
diastase action, however, in certain wheat grains in which the 
