20 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE. 
as corn grits or brewers' rice, are used in conjunction with malt, the 
same type of malt is popular, although an extreme development of 
diastase is not here demanded, because the additional amount of 
starch to be converted is less. 
The explanation of the greater enzymatic power of small-berried 
barleys seems simple. The diastase-secreting surface is confined to 
the epithelial layer. The proportion of epithelial surface to volume 
of endosperm should also represent the ratio of diastase to starch. 
For the purpose of illustration, the shape of the barley gram may be 
considered as a sphere, while the curve of the scutellum may be 
taken to represent that of a second sphere partly included in the first. 
If the size of the grain is made greater, its volume is increased much 
more rapidly than the area of the surfaces of the spheres, according 
to well-known laws of geometry. That is to say, for any increase in 
the size of the grain the increase in the area of the surface of the 
scutellum is much less proportionately than the increase in the vol- 
ume of either the embryo or the endosperm; and, conversely, as a 
grain decreases in size the epithelial surface decreases much less pro- 
portionately than the bulk of its endosperm. It is therefore but 
natural that the diastase production in a small grain should be rela- 
tively greater than in a large one and often greatly in excess of the 
needs for conversion. 
The relation of diastatic power to nitrogen content is a slightly 
more complex problem. In general, barleys high in nitrogen are 
also high in enzymatic power. The case varies somewhat with con- 
ditions. In the small-berried barley the same facts apply as in the 
ratio of scutellar surface to endosperm. The aleurone layer is one of 
the great sources of nitrogen in the barley grain. This layer is 
almost invariably three cells deep. If the grain be very small, the 
two or three layers of cells completely encircling the starch endosperm 
form a very considerable part of the grain. Since they are high in 
nitrogen, this element tends to represent a higher and higher percent- 
age of the total as the diameter of the grain is progressively reduced. 
In a very small gram the percentage of nitrogen is therefore likely 
to be high, even though the starch endosperm be ever so mealy, the 
deciding factor being, of course, the great proportion of the aleurone 
layer. 
There is, however, among the 2-rowed barleys a different situation, 
in that climate and culture assume a greater importance. Barley- 
growing areas are often conspicuous for their production of high- 
nitrogen barleys. Indeed, the crops of any section vary in this re- 
spect from year to year. It is almost invariably the case that these 
high-nitrogen crops are also high in diastatic power, often possessing 
an enzymatic potency almost equal to that of the small-berried sorts. 
In these cases, also, the explanation is found hi the ratio of the 
