2 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE. 
sidered to be one of the most important functions of the malting pro- 
cess. In small-berried malts the excess of diastase is often used in 
brewing to convert quantities of inert starch in addition to that found 
in the grain itself. In some large-berried malts it may be so used; 
in others, it is best used in conjunction with the other ferments to 
convert a Jarge endosperm and thereby obtain a high percentage of 
extract. 
The possibility of this improvement in quality was the cause of the 
special study made of this grain. Early in the investigation it was 
realized that the desirability of any barley must rest largely on its 
morphology, because the physiological changes must owe their 
origin to morphological sources. An extensive study of the barley 
grain, both at rest and in germination, was outlined. It was later 
found that the investigation had to be extended to include the 
embryology of the grain, in order to explain certain features of its 
resting condition. The Office of Foreign Seed and Plant Introduction, 
where a large part of these investigations was carried on, was of great 
service in obtaining for study samples of barleys from almost every 
country of the world. The primitive barleys of Asia and the most 
specialized productions of Europe were compared in structure and in 
the details of germination. <A persistent agreement between malting 
quality and morphological structure was found throughout the 
observations, and the conclusions pointed toward a hopeful method 
for securing a better quality in this grain. 
A brief report which discussed the secretion of diastase and cytase 
in the barley grain was made by the-senior writer! in 1908. Such 
statements in this paper as relate to the histological phase of secre- 
tion are also based upon his studies. 
STRUCTURE OF THE BARLEY GRAIN. 
A ripened grain of barley is a very complex structure. It con- 
tains not only the usual essential members of growth, but certain 
adhering layers of tissue which remain from organs functional at 
earlier periods of development. The gross anatomy of the grain 
may be separated into three divisions: The seed proper contains the 
young plantlet and the food stored for its use in germination. Envyel- 
oping the seed is a covering of several layers which, because it includes 
the remains of both the ovary walls and the integuments, has been 
given the name of caryopsis. In most of the cereals this caryopsis is 
freed from the glumes or floral leaves by thrashing. With barley this 
is not usually the case. In all but a few forms the glumes are grown 
fast to the caryopsis, and the grain presents the appearance shown in 
figure 1. While the relation of the parts is more apparent when con- 
sidered in the order enumerated, a study of the structure more logic- 
1 Mann, Albert. A new basis for barley valuation and improvement. U.S. Department of Agriculture, 
Bureau of Plant Industry Circular 16, 8 p., 3 fig., 1908. 
