MORPHOLOGY OF THE BARLEY GRAIN. 
9 
smaller while still retaining their uniform shape, but by the corrosive 
action of a powerful digestive diastase. The grains become irregu- 
larly pitted and are rapidly absorbed. 
The cells first affected are those in contact with the scutellum. 
According to Brown and Morris the first visible change in the appear- 
ance of the starch grains in the endosperm cells is coincident with 
the first appearance of starch in the cells of the scutellum, imme- 
diately back of the epithelial layer. After the first layer of endo- 
sperm cells has been broken through, the process gradually extends 
through the remainder of the endosperm. The action takes place 
along three lines: (1) It slowly proceeds directly into the mass of 
the starch endosperm; (2) it moves with more rapidity through the 
area immediately adjacent to the aleurone layer; and (3) it follows 
along the furrow at an even greater rate. The course of attack is 
thus directly opposite to that of the infiltration of starch. The cells 
last to receive deposits of starch are the regions of most rapid deple- 
tion. At the end of four or five days' slow germination, the path 
of affected tissue appears in longitudinal section as more or less 
of a crescent, the horns well advanced beneath the aleurone layer. 
Indeed, the crescent is already apparent in Plate II, figure 2, where 
germination was arrested at the end of the second day. 
As germination advances, the tissues earlier affected become almost 
entirely liquefied and the diastatic and cytatic action proceeds to 
the reduction of the remaining endosperm areas. The last parts 
to yield are the dense deposits in the center of the flanks of the grain 
and especially those farthest from the scutellum. The epithelial 
layer undergoes some significant modification during this progressive 
starch solution. As previously noted, the cells first elongate slightly 
and certain changes take place in the protoplasm. Later there 
occurs (and more or less rhythmically reoccurs) a deposit which 
gathers in the outer ends of these cells. When the digestion is almost 
complete, the epithelial cells undergo a sudden elongation, attaining 
a length almost four times that which marked their former condition. 
In the process of malting, the aleurone layer is not affected. It is 
found intact in brewers' grains even after they have endured the 
heating and strong diastatic action of the mash tub. In normal 
growth it is only when the plant has developed to the point of exhaust- 
ing the starch endosperm that this layer begins to disintegrate and 
is absorbed by the plant. 
CONVERSION OF THE ENDOSPERM. 
The morphological changes in the endosperm are, of course, only 
the visible effects of the essential actions, which are enzymatic. 
The disintegration of the cell walls is a chemical transformation of 
cellulose to sugar and other compounds. The breaking down of the 
75719°— Bull. 183—15 2 
