MORPHOLOGY OF THE BARLEY GRAIN. 
17 
a submersion for several months in this killing fluid a Living embryo 
is able to effect the usual processes of conversion. 
That the functions of the scutellum are localized in the epithelial 
layer is readily shown by experiment. The removal of this layer 
immediately results in an absolute loss of the scutcllum's power of 
digestion. It is so fully incapacitated that no visible corrosion is 
effected upon a contact surface of starch, when previously such effect 
was very marked. An epithelial layer, even when not connected with 
the embryo, seems able to accomplish a slight change, even though 
no provision for the removal of the products of conversion is made. 
The exact way in which the epithelial layer produces diastase is 
not known. The change in the plasma, the elongation of the cells, 
and the peculiar granular deposit that accumulates at their outer 
ends are all probably connected with the exercise of this function. 
Indeed, Torrey has gone so far as to assert that this is a deposit of 
actual enzymatic substance. He asserts that it appears, gathers at 
the outer end of the cell, and then passes into the endosperm, that 
the cell stays clear for some time, and that the same phenomena are 
then repeated. The writers have not verified this statement beyond 
noting that the deposit varied greatly in individual grains which were 
killed at different stages of germination. Sometimes the entire end 
of the cell was clouded and the outer end heavily charged with a 
coarse granular deposit, and at other times it was entirely free. 
LOCATION OF DIASTASE SECRETION. 
There are two diastases present in the barley grain: One of trans- 
location, capable of only weak action; and one of digestion, capable 
of powerful corrosion. 
The endosperm is incapable of self-digestion other than the slight 
action of the diastaste of translocation. 
The aleurone layer is made up of highly vital cells, which persist 
until the starch endosperm has been almost completely absorbed. 
The most rapid starch conversion is next to this layer. 
These facts are not sufficient to ascribe any secretive function to 
the aleurone layer, the rapid dissolution next to this tissue being due 
to the fact that from their nature the adjacent cells are easier to 
break down than the ones in the central part of the endosperm. An 
even more rapid corrosion follows the furrow, although it is largely 
composed of inactive and dead cells. No corrosion is to be found next 
to the aleurone layer except as the changes move outward from the 
scutellum. The absence of means to remove the products of conver- 
sion at the distal end should not prevent the first stage of conversion 
taking place if the aleurone layer were an active enzymatic organ. 
That the scutellum is active in enzym secretion is shown by the 
fact that the first changes occur in the layer of endosperm in contact 
