2 BULLETIN 183, U. S. DEPARTMENT OF AGBICULTURE. 



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 large 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 

 gram, both at rest and in germination, was outhned. 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 

 speciahzed productions of Europe were compared in structure and in 

 the details of germination. A persistent agreement between malting 

 quahty 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 

 earher 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. Envel- 

 oping the seed is a covering of several layers wliich, 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 aU but a few forms the glumes are grown 

 fast to the caryopsis, and the grain presents the appearance shown in 

 figure 1. Wliile 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. 



