106 A GRAIN OF BARLEY. 
we will consider that first of all, as it forms the bulk of the 
contents of the barley endosperm. 
It has long been known that during the complex chemical 
changes which go on during the germination of starch-containing 
seeds, a peculiar soluble ferment, diastase, is produced.* This 
ferment, under certain well ascertained conditions, is able to 
convert starch into sugar, and the nature of this sugar, which 
is known as ma/tose, was first established by the well-known 
work of our respected Member, Mr. C. O'Sullivan, F-.R.S. 
It is to the presence of this sugar maltose that malt-wort 
mainly owes its sweet taste and fermentability. During the first 
process of brewing, the mashing, (which consists, as you know, 
in infusing the malt with hot water), the diastase acts upon the 
starch of the grain, and converts it to a great extent into 
maltose. This chemical change, which is brought about with 
great rapidity at the comparatively high temperature of the 
mashing process, is carried on more slowly, but still very 
completely, during the germination of our barley grain; and 
if we allow the growth to continue we find that the endosperm 
is gradually emptied of all its starch, which has passed into the 
tissues of the young plant in the form of sugar. 
It is generally supposed that the active ferment diastase, 
which produces this transformation of the starch, has its 
origin in the growing embryo. If this is the case it must make 
its way through the epithelial layer of the scutellum, and the 
adjoining layers of compressed and emptied cells of the 
endosperm before it can reach the starch-containing cells. There 
are certain difficulties connected with this explanation of the 
facts, of which by far the greatest is the extreme non-diffusibility 
of diastase. It may be after all that the ferment which breaks 
down the starch-granules has its origin in the starch-containing 
cells themselves, by a change in the residual protoplasm of 
these cells. It is not improbable that the initiating cause of this 
“change may prove to reside in the small quantity of vegetable 
_ ™ Diastase exists ready formed in most starch-containing seeds, but it always 
increases in amount on germination. 
