MORPHOLOGY OF THE BARLEY CHAIN. 
31 
than are the imported pedigreed strains. In one case there is a con- 
siderable number of subvarieties from which to choose; in the other, 
there is a single type that has shown superior adaptation to a widely 
different condition of soil and climate. In any case, whether the 
means be the acclimatization of established varieties or the produc- 
tion of new ones, the problem is not one of the country at large, but 
is more or less local. It is also a problem in which only the first steps 
of progress have been made in this country. 
SUMMARY. 
The integuments that envelop the ripened seed of barley arise from 
four sources: The nucellus, the true integuments, the walls of the 
oYary, and the glumes. Of these, only one has any function other 
than the protection afforded by dead tissue. The investing mem- 
brane of the nucellus develops into the semipermeable membrane, 
which is found to have remarkable selective powers. 
In the development of the barley grain the endosperm develops 
earlier and more rapidly than the embryo, but it is the last to be 
completed, inasmuch as starch infiltration continues until the parent 
plant has ceased to live. The first starch is laid down in the center of 
the flanks of the grain. Infiltration of starch takes place in cen- 
trifugal order. At maturity the starch is less dense about the periph- 
ery of the endosperm than in the center. The embryo occupies a 
lateral position with reference to the endosperm at the proximal end 
of the grain. The epithelial layer is not functional until near 
maturity. 
Germination is the continuation of the growth of the embryo 
which was arrested by the maturation of the seed. In its growth the 
embryo utilizes the food stored in the endosperm. 
The conversion of the endosperm is effected by enzyms secreted by 
the epithelial layer of the scutellum. The cells first affected are those 
in contact with the epithelial layer. Conversion proceeds from the 
proximal end slowly toward the distal end, working more rapidly 
through the layers lying immediately beneath the aleurone layer. 
Cytase and diastase must both proceed from the scutellum, and the 
proteolytic ferments most probably owe their origin to the same organ. 
The aleurone layer is not a secreting organ. Its function is prob- 
ably mainly a protective one, although the absorption of its highly 
nitrogenous contents by the germinating plantlet occurs at a very 
opportune time in its development. 
The greater diastatic power of small-berried barleys is due to the 
fact that the secreting area is proportionately larger. The area of the 
epithelial layer as a part of the surface of a spheroid must decrease 
less rapidly than the volume of the endosperm as the size of the 
barley grain is lessened. 
