Mann, Albert.

Morphology of the barley grain with
reference to its enzym-secreting areas.
1915.

} UNITED STATES DEPARTMENT OF AGRICULTURE
BULLETIN No. 183

Contribution from the Bureau of Plant Industry
WM. A. TAYLOR, Chief

i'ashington, D. C. PROFESSIONAL PAPER April 13, 1915

MORPHOLOGY OF THE
BARLEY GRAIN WITH REFERENCE TO
ITS ENZYM-SECRETING AREAS

By

ALBERT MANN, Plant Morphologist, and H. V. HARLAN,
Bee in Charge of Barley Investigations

CONTENTS

\

Function of the Aleurone Layer . . .

Greater Diastatic Power of Small-Berried
and High-Nitrogen Barleys . . . ». «

Efficiency of Conversion

American Barleys

Modifications Possible by Culture . .

Foreign Barleys

Summary .. . . e«

WASHINGTON
GOVERNMENT PRINTING OFFICE
1915

BULEE TIN: OF THE

;USDEPARTMENT OFAGRICULTURE

No. 183

Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief.
April 13, 1915.

(PROFESSIONAL PAPER.)
MORPHOLOGY OF THE BARLEY GRAIN WITH REFERENCE

TO ITS ENZYM-SECRETING AREAS.

By Arzert Mann, Plant Morphologist, Office of Agricultural Technology, and EE Vis
Harwan, Agronomist in Charge of Barley Investigations, O,ffice of Cereal. Investiga-
tions.

CONTENTS.

Page. Page.
introduc tionmessssn sees kewcctcssseeca see es 1 | Source of cytatie and proteolytic ferments...- 18
Structure/of the barley. grain 23.22. s252i<22 22 2 |. Function of the aleurone layer ..... .«---<8-* 18

Development of the barley grain...........-- 5 | Greater diastatic power of small-berried-and
Germinajtionias vaste ees sa nea Susu 8 of high-nitrogen barleys...-.-.---..-------- 19
Conversion of.the endosperm.........-:.----- On| Met CIENCY OMCONVErSIONS ease. =e see sacle 21
Résumé of the conclusions of other investi- American barley ssiesase sje ollie ecisieee a 27
PAL ONS tama Naeem Sse Ne Ra 10 | Modifications possible by culture.........--- 28
Source of diastatic ferments..............--- 12 | Foreign barleys......-.----- stan sh eeeoaaas 30
Location of dizstase secretion .......--..---- LMS SUM Any Saw aso vale see seraene miarecne Ace alelelers 31

INTRODUCTION.

The value of the barley crop to the American farmer depends upon
two factors, the yield per acre and the price per bushel. An increase
of revenue is as readily effected by one as by the other. The yield is
necessarily an agricultural problem; the price is also, within certain
limits. Although the daily price of any market product ordinarily
varies over a considerable range, higher values are placed upon those
offerings which most perfectly meet the requirements of consumers.
A superior quality is the equivalent of a greater quantity. The nearer
a farmer can come to producing a product ideally suited to its uses,
the higher will be the price which he will be able to command.

By far the greatest demand upon the barley crop is for the purpose
of malting. This operation consists essentially in the breaking down
of the cell walls of the endosperm of the barley grain so as to leave its
starch grains exposed to later enzymatic actions, and also in the
abundant production of these enzyms, both the diastatic and pro-
teolytic. The abundant formation of diastase has long been con-

Nortg.—This paper is intended for distribution to agronomists, station directors, brewery chemists, and
selected maltsters.

75719°—Bull. 183 —15——1

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.

MORPHOLOGY OF THE BARLEY GRAIN. 3

ally proceeds from the glumes inward. The glumes, the seed coat of the
caryopsis, and the seed proper, each consists of several kinds of tissue.
THE GLUMES.

The outer surface of the glume is protected by a heavy cuticle.
The cuticularization does not penetrate deeper than the first row of
cells. The three outer layers of cells have heavily reinforced (scler-
enchymal) walls, while the underlying layers are thin walled and more
variable. They are usually three or four in number. The vascular
bundles of the glume are normal leaf bundles

THE SEED COAT OF THE CARYOPSIS.

The term ‘‘seed coat of the caryopsis” is here used to include
groups of tissues from three separate origins: The pericarp, the
testa, and the semipermeable
membrane. The pericarp is the
remains of the ovary wall. Its
outer layer lies flat against the
glume and is united with it.
Beneath the layer in contact with
the glume are several layers of
parenchyma, consisting of much
flattened and often almost dis-
connected cells. Below this are
two layers of parenchyma that
formerly contained chlorophyll.
Though equally flattened through
pressure, they are in much better
condition as a layer. The cells.
of this tissue are almost at right
angles to those of the main pa-
renchyma region and tangential
to the erain. On the inside of F!G-1.—A grain of 2-rowed barley: A, Dorsal view;
the pericarp are sometimes found So igad sss
scattering fragments of the inner epidermis of the ovary, their cells
also elongated lengthwise with the grain.

The testa is the remnant of the inner of the two integuments that
once existed inside the ovary wall, the outer one having disappeared.
The cells of the testa are crushed almost to the point of disappearance,
being represented in the ripened grain by a mere line. In intimate con-
tact with the testa and much better preserved is the investing mem-
braneofthenucellus. Itconsists of moderately thickened cells flattened
bypressure. Onthe inside of this are occasional patches of partly reab-
sorbed cell walls, remnants of the nucellar tissue. According to Brown,!
the investing membrane of the nucellus probably forms the semiperme-
able membrane, though the inner integument may also be concerned.

1 Brown, A.J. On the existence of a semipermeable membrane inclosing the seeds of some of the Gram-
inee. Annals of Botany, v. 21, no. 81, p. 79-87, 1907.

4 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

THE SEED PROPER.

The external layer of the seed proper is the aleurone layer. It
assumes a greater importance in barley than in other grains. It
normally consists of a stratum of two or three rows of cubical cells
gorged with protein contents. Their appearance shows them to be
cells of unusual vigor and vitality. The greater part of the space
within the aleurone layer is occupied by the starch endosperm. This
is, as in all grasses, a typical storage tissue. Its cells are thin walled
and packed with starch granules. The
nuclei are feeble and distorted by the pres-
sure of the accumulated starch. At the
proximal end of the starch endosperm and
partly embedded in its tissue lies the embryo,
the morphology of which is observed with
ease but interpreted with difficulty. From
its nature, it must contain all the growing
elements of the plant to be, as well as a num-
ber of modified organs. The embryo lies
obliquely to the long axis of the grain, its
erowing point directed toward the distal end.
The true vegetative point 1s inclosed within
the first leaves of the plant. In barley these
are twisted, giving rise to the term “acro-
spire” in place of “‘plumule.” The plumule
sheath surrounds all the upper vegetative
portions. At the proximal end of the em-
bryo is found a single main radicle. A short
distance above, possibly at the first rudimen-
tary internode, are five to eight secondary
Fic. 2.—A high-grade barley gran Yootlets. When eight are present three are

with the glumestemoved to show laced on either side and two toward the
the embryo with its coilarlike

scutellum (s). The inner enve. front. ‘The space between the secondary
lopes have been removed from rootlets and the growing poimt serves as
the upper part of the grain.

a base for the attachment of the extra-
embryonic tissue, the scutellum, or shield (fig. 2), which includes prac-
tically all the remaining tissue. The origin and significance of this
body as well as of the epiblast (absent in this genus, but common in
grasses) has been variously interpreted. The scutellum is, however,
generally conceded to be an absorbing organ. It is made up of thin-
walled cells with large nuclei. Its inner surface rests directly upon
the mass of the endosperm, and this surface of contact consists of a
layer of elongated cells placed endwise to both the endosperm and
the rest of the scutellar body. This layer, which is known as the
epithelial layer, plays, according to the observations of the writers,
a large part in the chemical activities of germination.

Bul. 183, U. S. Dept. of Agriculture. PLATE |.

ar

PHOTOMICROGRAPH OF A LONGITUDINAL SECTION OF A BARLEY OVARY IMMEDIATELY
AFTER FERTILIZATION.

The two plumosestigmas do not appear. a. Outer epidermis of ovary; b, colorless parenchyma; ¢c,
chlorophyll-bearing parenchyma; d, inner epidermis of ovary; e, outer integument of ovule;
f, inner integument of ovule; g, external layer of the nucellus; h, nucellar tissue; i, group of en-
dosperm-forming cells of the young embryo sac.

Bul. 183, U.S. Dept. of Agriculture. PLATE II.

Th

Fia. 1.—LONGITUDINAL (DORSI-VENTRAL) SECTION OF A MATURE
BARLEY GRAIN.

a, Starch endosperm; 6, aleurone layer; c, area of starch endo-
sperm, adjacent to the scutellum, representing the initial
stage of the corrosion of the endosperm. This took place at
the close of the ripening ofthe grain. d-r, The embryo; d,
plumule with investing sheath; e, primary, and e’, secondary,
radicles; /,scutellum, the surface next to the endosperm covered
with the epithelial layer (g); 7, root cap of primary radicle.

FIG. 2.—LONGITUDINAL SECTION OF BARLEY GRAIN, SHOWING
THE STAGE OF ENDOSPERM CONVERSION AT THE END OF
THE SECOND DAY OF GERMINATION.

Thestarch endosperm is being broken down in the denseareas directly
in front of the epitheliallayer, (e), of the scutellum (s), and more
rapidly in the less dense areas adjacent to the aleurone layer, (a).
b, Clear fluid area produced during germination; c, corroded area of
starch endosperm; n, normal starch endosperm not yet attacked.

MORPHOLOGY OF THE BARLEY GRAIN.

Or

DEVELOPMENT OF THE BARLEY GRAIN.

An understanding of the office and behavior of the various organs
of the barley grain is greatly facilitated by observations upon their
origin and development. Some of these organs are functional
throughout the existence of the seed; others important in the early
stages afterwards disappear, while still others become so modified
as to be serviceable in a totally different way.

The flower of the barley plant is inclosed within the flowering
glumes, as in all grasses. It consists of a simple ovary containing a
single ovule. The stigma is two branched and plumose. Three
versatile anthers attached below the ovary fit into as many natural
angles in the glumes. On the dorsal side of the ovary are two
lodicules.

At the time of flowering, the ovary wall is a but slightly modified
vegetative structure. It consists of the usual epidermis, a colorless
parenchyma of several layers, a chlorophyll-bearing parenchyma, and
an inner epidermis. The chlorophyll layer is the only one in any
way exceptional. The cells of this le with their long axes at right
angles to that of the others and tangential to the grain. Inside the
ovary are two integuments which probably act as conductive tis-
sues to the growing pollen tube during fertilization. Each is formed
of two layers of thin-walled cells. The cells of the outer integument
are somewhat larger than those of the inner one and are much thin-
ner walled. The contrast between the two integuments is very
evident in Plate I. Inclosed by the two integuments is the nucellus,
which is in turn surrounded by its own investing membrane, con-
sisting of a single layer of cells. In the parenchyma mass of the
nucellus is the embryo sac, which before fertilization contains the
usual cight cells. At this stage of development the cells of all the
tissues are filled with plasma.

After fertilization the ovary increases in length and width. As
the essential parts of the developing seed are taking shape, certain
now useless portions of the enveloping structures become modified
and in some cases absorbed. The plasma gradually disappears from
the cells of the outer integument, the cell walls become transparent,
and finally dissolve and disappear. The inner epidermis is also
absorbed, although not always completely, as traces sometimes per-
sist at maturity. A little later, portions of the ovary wall begin to
weaken. The starting poimt is usually just outside the chlorophyll
layer, and the process advances outward through the overlying
parenchyma layers. At maturity this tissue is represented by a
compressed mass of almost disconnected cells. In the earlier stages
of growth it is this reduction of tissue that establishes the ‘‘green
ripeness” of Kudelka, the removal of the overlying cells bringing
the chlorophyll layer nearer to the surface, thus intensifying the

6 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

ereen color. The chlorophyll-bearing cells themselves become some-
what thickened and remain plainly discernible as a layer, even at
maturity. The inner integument does not disappear as does the
outer one. The cell walls undergo considerable modification and the
layer becomes crushed, so that it exists in the ripened fruit only as
a dull brown line. It is in the investing membrane of the nucellus,
however, that the greatest functional transformation occurs. The
cell walls of this delicate tissue become thickened, and the layer
quickly assumes, either independently or in conjunction with the
inner integument, the functions of a selective semipermeable mem-
brane. Brenchley states that even before the glumes are grown fast
to the fruit it is necessary to prick through this membrane to bring
about the entrance of killing fluids. The absorption of the nucellar
tissue begins almost immediately after fertilization has taken place.
It proceeds rapidly and is almost total, a small body persisting near
the funicle and fragments of collapsed cell walls in chance locations
elsewhere.

Of the tissues which envelop the seed, the semipermeable membrane
is the only one performing more than mechanical service. On the
other hand, all the growth within the embryo sac is of physiological
purpose in one or more ways. There are three important structures—
the aleurone layer, the embryo, and the starch endosperm (PI. II,
fig. 1). The three are associated in development and are intimately
related in later germination and growth. Preliminary to fertili-
zation, the nucleus of the embryo sac divides and redivides until
eight nuclei are present. The egg cell and two companion cells locate
near the micropyle. Two others unite to form a large nucleus near
the center, while the remaining three, the antipodal cells, pass to the
end opposite the egg cell.

Following fertilization, the egg cell begins the initial divisions of the
growth of the embryo, but its development is less rapid than that of
the large central nucleus, which is the source of the endosperm. The
earliest and most vigorous cell division of the endosperm-forming
tissue occurs near the distal end of the grain upon the ventral side and
adjacent to the antipodal cells which, according to Johannsen, have
by this time increased to the number of 30 or thereabouts. After the
first layer of endosperm cells has been formed, the growth continues
radially toward the center of the grain. The mature stage is always
found on the ventral side and particularly in the flanks of the
furrow. It is only after the embryo sac is entirely filled with cells
that the outer layer of the endosperm begins to differentiate. Al-
though at this time starch grains are infrequent throughout the
endosperm, its external layer begins to exhibit the proteolytic

1Johannsen, W. Om Frghviden og dens Udvikling hos Byg. Meddelelser, Carlsberg Laboratoriet,
Bd. 2, Hefte 3, p. 103-133, 3 pl., 1884. (French ed., p. 60-77.)

MORPHOLOGY OF THE BARLEY GRAIN. 7

character of the aleurone sheath. The first starch grains are formed
in the older areas of the endosperm near the distal end of the grain.
According to Brenchley,! this occurs on the sixth day after flowering
and in the middle of the flanks of the grain. On the seventh day,
scattering grains are apparent in two-thirds-of the length of the grain.
On the tenth day, the deposit is very heavy in the flanks and extends
almost to the embryo. It is not until the nineteenth day that the
main body of the starch is completed. The cells next to the aleurone
layer are the last of the endosperm tissue to fill with starch.

Accompanying this infiltration of starch are certain modifications
of the nuclei of the endosperm. Just before the first starch grains
are formed the nuclei become granular. For a time they are full of
vigor, with the starch grains arranged about them. As the process
advances, the nuclei gradually become distorted by pressure exerted
by the growing starch. The cells next the aleurone layer and near
the furrow are affected much later and to a lesser degree. As above
stated, the aleurone layer begins to differentiate soon after the embryo
sac becomes filled with new cells. It consists at first of a single
layer, increased to three as the endosperm mass grows. The cells
are arranged radially and present about the same appearance in
both cross and longitudinal section. In tangential section their
arrangement is very irregular. Their contents quickly show the
characteristic aleurone nature. The dense mass of glutinous and
fatty compounds, the aleurone grains themselves, and the large
nuclei are present in no other section of the endosperm. As the cells
approach maturity the walls become very thick and are seen to be
perforated with small canals.

It is only after the cells of the endosperm have divided many
times and the endosperm mass is beginning to take shape that the
embryo begins active development. At first it lies free in the sap
at the lower end of the embryo sac. Gradually the endosperm
becomes organized about it, and by the time the more prominent
divisions of the embryo have become differentiated the two are in
contact. The later growth of the embryo is at the expense of the
starch endosperm and during germination their relation is that of
parasite to host; but before the grain is matured this statement is
not entirely justified, in that, although numerous endosperm cells
are emptied of their contents and a mass of collapsed cell walls is
crowded before the upper angle of the scutellum, their reduction
takes place more in the manner of normal growth. The cell walls
are not broken down, and the removal of the starch is effected by
the processes typical of the diastase of translocation rather than by
that of the corrosive action of digestion.

1 Brenchley, W. E. Development of the grain of barley. Annals of Botany, v. 26, no. 103, p. 903-928,
22 fig., 1912.

8 BULLETIN 183, U. 8S. DEPARTMENT OF AGRICULTURE.

Within the embryo various tissues arise. A primary radicle and
from five to eight secondary rootlets, inclosed in their sheathing
tissues, are directed toward the proximal end of the grain. The
plumule within the plumule sheath points up over the endosperm
toward the distal end of the seed. Attached midway between the
root and plumule—that is, to the hypocotyl—by a wide ligament, or
umbilicus, is the scutellum. This organ spreads out over the
entire surface of the endosperm lying next to the embryo and has
on its inner or adjacent surface a layer of specialized cells—the

epithelial layer.
GERMINATION.

Germination is the continuation of the growth of the embryo,
arrested at the time of the maturation of the seed. The first step in
germination is a distension of the grain, due to the absorption of
water. In the resting stage most of the tissues of the embryo are
free from starch. When first brought under conditions favorable
for germination the few starch grains present disappear. Very
shortly, however, starch again becomes evident in tissues that were
perfectly free from it at maturity. In the outer layers of the scutel-
lum a marked deposit is soon apparent. As the process advances,
the cells of the epithelial layer elongate shghtly. Brown and Mor-
ris! noticed that one of the first changes in the grain was in the
appearance of the protoplasm of these cells. In the resting state
this is clear and finely granular. As the first steps of germination
are In progress it assumes a much coarser character and the cell
becomes cloudy. This condition obtains until the endosperm is
almost entirely absorbed.

The first actual formation of new tissue takes place in the primary
radicle. This breaks through the coleorhiza and is the first part of
the plant to emerge from the grain. The secondary rootlets are
slightly less advanced. The plumule develops more slowly, and
under restrained malting conditions it may be several days in reach-
ing less than the length of the grain.

In the endosperm, germination is, of course, a process of destruc-
tion. In the history of a single cell the walls first become thickened
as if distended with water. The laminz become distinct, the walls
become translucent, and disintegration sets in. Various investi-
gators have asserted that a complete obliteration of the walls takes
place, but the writers have not been able to arrive at this conclusion,
the walls always being discoverable to some extent, especially by
means of staining. As soon as they have been sufficiently weakened,
action begins upon the starch grains. Their dissolution in this case
is not by the translocation process, in which they gradually become

1 Brown, H. T., and Morris, G. H. Researches on the germination of some of the Graminex, part 1,
Journal, Chemical Society [London], v. 57 (Transactions), p. 458-528, 1890.

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 IT, 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 aiter 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

10 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

starch is the result of the action of maltose-forming diastase. The
disappearance of the plasmic network of the cells is due to its being
peptonized by proteolytic enzyms and thus made soluble for absorp-
tion. Chemistry has made known the processes by which these
changes are effected. It has found methods to increase the power
of the grain to digest these various substances. It has invented
ways of manipulation so as to secure the greatest efficiency of the
enzyms present. It has not, however, shown any way of increasing
the capacity of a grain to secrete enzyms, nor has it discovered any
modification of structure that would lead to a greater economy in
conversion.

It is only by a definite location of the sources of these energies
that a working basis for improvement of the barley grain can be
obtained. Not only must it be known which of the tissues are
concerned in these activities, but the extent and nature of the action
of each tissue must be understood. Upon this point there has been
much divergence of opinion. The disagreement has been not only
-as to the parts of the grain concerned, but also as to whether or not
the various enzyms are secreted by the same or by separate organs.
Since there are three areas in dispute and three enzyms to be ac-
counted for, the number of possible hypotheses has occasioned a
very considerable confusion.

RESUME OF THE CONCLUSIONS OF OTHER INVESTIGATORS.

Although the number of investigators who have been interested
in one or several phases of this subject is great, a brief statement of
their conclusions is necessary at this point.

Krabbe ! assigns all diastase secretion to the individual cells of the
endosperm, based on his assertion that diastase can not pass from
cell to cell.

Green? finds in Ricinus communis a marked ability of the endo-
sperm for self-digestion.

Hansteen * finds that the endosperms of Zea mays and Hordeum
vulgare are capable of self-digestion when products of conversion are
removed, that the aleurone does not supply the diastase, and that
the scutellum is capable of vigorous corrosion of adjacent starch.

Pond,‘ in an exhaustive chemical research, fails to discover any
ability for self-digestion in the date.

1 Krabbe, G. Untersuchungen tiber das Diastaseferment unter specieller Beriicksichtigung seiner
Wirkung auf Stiirkekorner innerhalb Pflanze. Jahrbiicher fiir Wissenschaftliche Botanik [Pringsheim],
Bd. 21, Heft 4, p. 521-561, pl. 13-15, 1890.

2 Green, J. R. On the germination of the seed of the castor-oil plant (Ricinus communis). (Abstract.)
Proceedings, Royal Society, London, v-. 47, no. 287, p. 146-147, 1890.

3’ Hansteen, Barthold. Ueber die Ursachen der Entleerung der Reservestoffe aus Samen. Flora, Bd.
79, p. 419-429, 1894.

4 Pond, R. H. The incapacity of the date endosperm for self-digestion. Annals of Botany, v- 20, no.
77, p- 61-77, 1906.

MORPHOLOGY OF THE BARLEY GRAIN. Ata

Puriewitsch! concedes no more power to the aleurone layer than to
the rest of the endosperm.

Torrey,’ in studies of germinating maize, attributes the secretion
of both cytase and diastase to the epithelial layer. He associates
the enzym with the production of a definite granular substance in
the epithelial cells the formation of which is coincident with the first
attack upon the endosperm cells. Incidentally, he attributes the de-
pleted layer of crushed cells, which is formed in the later stages of
growth, to pressure and not to the absorption of the still growing
endosperm by the expanding scutellum.

Van, Tieghem ? finds, among many things less pertinent to this dis-
cussion, that the embryo of Mirabilis jalapa is capable of utilizing
macerated endosperm as a nutritive substance.

Sachs * considers, except for minor details, that the relation of
embryo to endosperm is one of parasite to host.

Linz * finds that the removal of the aleurone layer of corn makes
little difference in the dissolution of the endosperm. He concludes
that this layer is not secretive.

Griiss° finds that the scutellum of barley is able to secrete abundant
diastase and to nourish itself upon starch supplied in place of the
endosperm.

Reed? looks upon the epithelial layer as containing the only
secreting cells in either Zea mays or Phoenix dactylifera, but concerns
himself mostly with the changes in nuclear and plasmic conditions.

Brown and Escombe § conclude that the scutellum of barley secretes
diastase, but that the production of cytase occurs in the aleurone layer,
but they donot find any power of secretion in a detached aleurone layer.

Green *® assigns the origin of cytase for the most part to the aleurone
layer, but attributes the production of the greater part of the diastase
to the scutellum.

Brown and Morris,!° in one of the most exhaustive investigations
to which these questions have been subjected, find the scutellum of

1 Puriewitsch, IK. Physiologische Untersuchungen iiber die Entleerung der Reservestoffbehilter.
Jabrbiicher fiir Wissenschaftliche Botanik [Pringsheim], Bd. 31, Heft 1, p. 1-76, 1897.

2Torrey, J. C. Cytological changes accompanying the secretion of diastase. Bulletin, Torrey Botan-
ical Club, v- 29, no. 7, p- 421-435, pl. 20, 1902.

3Van Tieghem, P. E. L. Recherches physiologiques sur la germination. Annales des Sciences Natu-
relles, Botanique, s. 5, t-. 17, p. 205-224, 1873.

4Sachs, Julius von. Lectures on the Physiology of Plants. Tr. by H. Marshall Ward. Oxford, 1887,
p-. 373.

5 Linz, F. Beitrige zur Physiologie der Keimung von Zea mais. Jahrbiicher fiir Wissenschaftliche
Botanik [Pringsheim], Bd. 29, Heft 2, p. 318, 1896.

6Griiss, J. Ueber die Secretion desSchildchens. Jahrbiicher fiir Wissenschaftliche Botanik[Pringsheim],
Bd. 30, Heft 4, p. 645-664, 1 fig., 1897.

7Reed, H. S. Study of the enzym-secreting cells in the seedlings of Zea mais and Phoenix dactylifera.
Annals of Botany, v- 18, no. 70, p- 267-287, pl. 20, 1904.

8 Brown, H. T.,and Escombe, F. On the depletion of the endosperm of Hordeum vulgare during germi-
nation. Proceedings, Royal Society, London, v- 63, no. 389, p. 3-25, pl. 1, 1858.

8 Green, J. R. Soluble Ferments and Fermentation. Cambridge [England], 1899, p. 29, 93.

10 Brown, H. T., and Morris, G. H. Researches on the germination of some of the Graminez, part 1.
Journal, Chemical Society [London], v. 57 (Transactions), p. 458-528, 1890,

12 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

barley capable of converting certain starches supplied in the place of
its endosperm. They find that excised embryos are able to grow
when the scutellum surface is grafted on endosperms in which life
is extinct. They consider the endosperm no longer a vital tissue
and claim that the aleurone layer does not secrete enzyms, assigning
cytase, as well as diastase, to the scutellum.

Ling supports Griiss, as opposed to Brown and Morris, regarding
the extent of the dissolution of cell walls in conversion. The latter
attribute the ‘‘mealiness” of malt to a marked dissolution of the
cell walls. Griiss holds that the walls become merely transparent.
Ling finds the walls present in all parts of the endosperm, although
affected by cytase.

Vines,’ while working with yeast and agarics, assumes that similar
enzyms exist in other plants. He finds two classes of enzyms: (1)
Those that peptonize and (2) those that peptolyse.

Beaven,’ while only incidental to the subject of his paper, remarks
that the starch endosperm of barley is built up in centrifugal order
and that its outer layer is easily broken down.

Gibbs * states that in the Alsinoidex the greatly reduced endo-
sperm is active only as an absorptive organ of the food material
which is here stored in the perisperm.

Ellrodt® finds that small-berried malts give a higher diastatic
power per gram of original material than do large-berried ones.

Brown ° finds that the semipermeable membrane exercises a
selective action, allowing water to enter the grain, but absolutely
excluding most substances in aqueous solutions. The absorption
is uniform in all parts of the grain.

SOURCE OF DIASTATIC FERMENTS.

On account of the fact that starch is the form in which most of the
convertible material is stored, its digestion has received a great
amount of attention. The process has been ascribed to three sources:
(1) To a secretion of the endosperm itself; (2) to a secretion by the
aleurone layer; and (3) to a secretion by the scutellum.

The theory of the self-digestion of the starch endosperm has been
conspicuously championed by only two men, namely, Hansteen 7

1 Ling, A. Presence of cell walls in the endosperm of malts. (Abstract.) Brewers’ Journal [New York],
v. 29, no. 10, p. 440, 1905.

2 Vines, S. H. Proteases of plants. Annals of Botany, vy. 18, no. 70, p. 289-317, 1904.

3 Beaven, E. 8. Varieties of barley. Journal, Federated Institute of Brewing, v. 8, no. 5, p. 542-600,
12 fig., 1902.

4 Gibbs, L. 8. Notes on the development and structure of the seeds in Alsinoidew. Annals of Botany,
vy. 21, no. $1, p. 25-55, 4 fig., pl. 5-6, 1907. Abstract in Botanical Gazette, v. 43, no. 5, p. 349-340, 1907.

° Ellrodt, G. Unterschied des Diastasegehaltes von Malzen aus grossk6rnigen und kleinkérnigen Gersten.
Wochenschrift fiir Brauerei, Jahrg. 23, no. 20, p. 243-244, 1906; also in Zeitschrift fiir Spiritusindustrie,
Jahrg. 29, no. 23, p. 209-210. Abstract ia American Brewers’ Review, v. 20, no. 7, p. 379, 1906.

6 Brown, A. J. On the existence of a semipermeable membrane inclosing the seeds of some of the Gram
inee. Annals of Botany, v. 21, no. 81, p. 79-87, 1907. ;

7 Hansteen, Barthold. Ueber die Ursachen der Entleerung der Reservestoffe aus Samen. Flora,
Bd. 79, p. 419-429, 1894,

MORPHOLOGY OF THE BARLEY GRAIN. 13

and, later, Pfeffer + in his review of Hansteen’s work. The work of
Hansteen is of some significance. He found that when the products
of conversion were constantly removed, the endosperm was able to
digest itself. His conclusion, however, that the endosperm is entirely
capable of self-digestion is rather too sweeping, especially since he
himself found a very active secretion of diastase in the scutellum, the
existence of which function is hard to understand if it be superfluous.
It is much more probable that the method used by Hansteen merely
exaggerated the normal action of such diastase as would naturally
be expected to be present in the endosperm of the ripened grain,
for a certain minute amount of diastase is necessarily present in the
cells of the endosperm to carry on the process of starch infiltration.
This is, however, merely that phase of diastase needed for the trans-
location of the starch while the barley grain is forming. Indeed,
according to the figures of Brenchley, the amount of diastase in the
vrowing grain decreases as the grain approaches maturity. It is
even reasonable to expect that not only would traces of this enzym
remain potentially functional in the endosperm of the ripened seed,
but that the cells of this endosperm, once able to produce this fer-
ment, would retain such ability to some degree, even in their less
active condition. The effect of such small quantities of local diastase
is not, however, to be confused with the vigorous attack that actually
takes place in the process of germination. The conclusions of the
writers are supported by those of many investigators, as above cited.

The theory that the aleurone layer is active in endosperm reduc-
tion has more in its favor than has that of the self-digestion of the
endosperm. The aleurone layer is obviously high in vital energy.
Its cells have the unmistakable aspect of active protoplasm. Their
nuclei are large and present a sharp contrast to the distorted plasmic
centers of the endosperm cells. The aspect of this layer during
germination also lends much to the support of the hypothesis of its
being functional. As previously noted, it is not digested with the
endosperm, but persists until the endosperm is almost entirely ab-
sorbed. When germination is carried only to that point where the
purposes of malting have been attained, the aleurone layer is still
intact. As shown in figure 3, almost perfect sections of this tissue
may be obtained from ordinary dried brewers’ grains, in which the
entire starch endosperm has been destroyed. In still further support
of the idea, the disintegration in a newly germinating seed proceeds
most rapidly directly adjacent to the aleurone layer. At certain
stages this diastatic movement may be seen to have progressed
until the thickest part of the endosperm is in a way surrounded with
digested starch cells.

1 Pfeffer, Wilhelm. Untersuchungen von Herrn Barthold Hansteen im botanischen Institut ausge-
fiihrten, tiber die Ursachen der Entleerung der Reservestoffe aus Samen. Berichte, Koniglich Sachische
Gesellschaft der Wissenschaften, Leipzig. Mathematisch-physische Classe, Bd. 45, p. 421-428, 1893.

14 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

Tangl* has shown that the thickened cell walls in the endosperm
of many seeds are provided with openings, so that the cell contents
are not isolated but in intimate contact. This is true of the aleurone
layer of barley, and the layer is in consequence more nearly a unit
than might be supposed.

The accumulative importance of these and other facts has caused
many authors to assert that the aleurone cells have a very important
secretive function. The views of the individual experimenters who
are inclined to this opinion are too numerous to discuss separately.
The points of variance between them and the writers are few and
turn largely on the
interpretation of
specific phenomena.

These differences
really center around
a single fact. When
the breaking down
of the starch endo-
sperm once com-
mences next to the
scutellum, it follows
rapidly through the
cells immediately
beneath the aleurone
layer. This point is
frankly admitted,
but is far from being

=]

‘1G. 5.—Section of piece of “brewers’ grain,’ that is, of a barley grain
that has passed through both the malting and the mashing processes.
The aleurone layer remains unchanged. The cell contents are a proof of aleurone

slightly shrunken by heating in the mash tub. The starch endo-

sperm is fully depleted of its contents. activity. It has other

interpretations more
consistent with the general facts of germination. These cells adja-
cent to the aleurone layer are markedly different from those of the
rest of the endosperm. They are younger. The starch endosperm
is laid down and its cells filled in centrifugal order, so that its
outer areas are the latest in formation and the latest in starch infil-
tration. They are also less gorged with starch. <A grain of barley
is not definitely limited in growth. In a way its growth is inde-
terminate, its development progressive until stopped by the act of
ripening, a stage in which the failure of the supply of food is a marked
factor. As may be seen in Plate III, the outer cells must from their
very nature be younger and less filled with starch, their walls less
desiccated, and their nuclei in a more nearly normal condition than
those of the more thoroughly matured storage cells. A cross section

1Tangl, Eduard. Ueber offene Communicationen zwischen den Zellen des Endosperms einiger Samen.
Jahrbiicher fiir Wissenschaftliche Botanik [Pringsheim], Bd. 12, Heft 2, p. 170-189, pl. 4-6 [1880].

MORPHOLOGY OF THE BARLEY GRAIN. 15

of a ripe barley grain treated with Millon’s solution presents a strongly
colored band just inside the aleurone layer and completely sur-
rounding the rest of the endosperm, showing the relatively high
proteid and low carbohydrate content of this region. The cell
contents, therefore, are obviously not identical with those beneath.

It is but reasonable to suppose that these young and loosely filled
cells would be more easily broken down and that diastase, acting
from the proximal end of the grain, even if distributed equally over
the surface of the endosperm, would advance most rapidly along this
area of least resistance. A strong point against the aleurone theory
of digestion is the fact that the cells of the endosperm first affected
are those next to the scutellum, as shown in Plate IV. If the aleurone
layer is active, why should not this take place uniformly in those
cells lying directly beneath that layer? Sections made through
erains germinated at high temperatures show the proximal end of
the endosperm to be in complete solution, while the cells next to the
aleurone layer toward the distal end of the grain are entirely un-
affected. This can not be due to a lack of water, for water can be
shown to pass readily through the walls of all parts of the grain.
One or two authors have attempted to ascribe this condition to a
certain inexplicable stimulus which proceeds from the growing
plantlet and passes through the connected plasma of the aleurone
cells, inciting them to successive action. Such theory fails to explain
why the movement advances much more rapidly along the furrow
than elsewhere. The cells in this region are for the most part dead
tissue and would be incapable of aiding the aleurone layer or of car-
rying any stimulus. However, since the region of the furrow con-
tains the conducting tissue during the development of the grain and
since it leads past the scutellum, it is readily seen that it could be still
instrumental in carrying secretions from that source, although inca-
pable of conveying stimuli.

A more plausible defense of the theory of aleurone secretion has
been advanced in the statement that the enzyms are able to work only
when the products of their conversion are removed, and that the
scutellum as an absorbing organ is responsible for the fact that the
action commences adjacent to it and can not proceed elsewhere,
except as the process of removal becomes effective. This theory is
not borne out by observations, in that the lack of a means of removal
would not prevent the preliminary stages of dissolution from taking
place at all points in contact with the aleurone layer. No such effect
occurs. Moreover, the percentage of maltose necessary to the in-
hibition of diastatic action is very high, certainly not less than 30
per cent. That this percentage is seldom reached is shown by the
fact that the cells first acted upon while in a partial state of conver-
sion pass on to the point of complete dissolution, even though they

16 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

are gorged not only with their own products of conversion but with
those of the cells lying beyond them.

As must be evident frem the writers’ opposition to the theories of
self-digestion and of aleurone activity, their investigations have been
overwhelmingly in favor of placing the entire function of diastase
secretion during germination upon the scutellum. Morphological
examinations have been made of thousands of barley grains at all
stages of germination. These have been repeated with a large num-
ber of varieties and types of barleys grown under varying conditions
in America and of seed imported from all parts of the world. In all
cases, the dissolution of the endosperm is effected in the same manner.
The corrosion commences with the parts directly in contact with the
scutellum. The action begins as quickly in front of the cells in the
center of the scutellum as it does in those next to its periphery and
therefore in juxtaposition to the aleurone layer. All later action is
such as would occur if the scutellum were the only source of diastase.
A grain from which the aleurone layer is removed is converted in the
usual manner. Moreover, the very appearance of the scutellum is
convincing. On its surface is the epithelial layer, which is typically
glandular. There are in plant growth no tissues that closely resemble
specialized secreting tissues, and seldom is there a more unmistakable
development of this than the epithelial layer, as shown in Plate V,
figure 1.

Most investigators have recognized the secreting power of the
scutellum; indeed, none have denied such function, even when
attributing to it only a subsidiary activity. Numerous experiments
have been made in the past and many of them repeated by the
writers. A grain from which the embryo is removed will not show
any tendency to germination, even though all external conditions,
such as light, heat, and moisture be made favorable and ample pro-
vision for the removal of conversion products be made. On the other
hand, and under proper artificial conditions, the scutellum is able to
support itself and to supply food for the growth of the plumule and
radicle independent of the endosperm. Morris and Brown, Hansteen,
Pfeffer, and numerous others have shown the ability of the embryo
(with the scutellum) to digest the starch supplied toit. This has been
demonstrated in numerous ways. The starch has been furnished in
the form of macerated endosperm and in the form of a mixture of
starch and plaster. In every case, the scutellum was able to corrode
the material supplied and to promote a considerable growth in the
plantlet. The embryo is also able to utilize an endosperm which is
entirely without living protoplasm. An excised embryo from a
healthy, vital grain can be grafted upon a dead endosperm with per
fect success. Such endosperm may be prepared in any way desired,
even by prolonged soaking in absolute alcohol; that is to say, after

Bul. 183, U. S. Dept. of Agriculture. PLATE III.

PHOTOMICROGRAPH OF A LONGITUDINAL SECTION OF A PORTION OF A BARLEY GRAIN
IN THE EMBRYONIC STATE.

a, Inner area of the endosperm, with starch grains; b, outer and younger area just forming, with few
state grains and large nuclei; c. aleurone layer; d, integuments and pericarp; g, fragments of
glumes.

Bul. 183, U. S. Dept. of Agriculture. PLATE IV.

PHOTOMICROGRAPH OF A PART OF THE SCUTELLUM AND ENDOSPERM OF A GERMI-
3 NATING BARLEY GRAIN.

The initial stage of germination is shown. Enzymatic action has begun in front of the epithelial
layer (a), but not next the aleurone (0).

MORPHOLOGY OF THE BARLEY GRAIN. 7

a submersion for several months in this killing fluid a living embryo
is able to effect the usual processes of conversion.

That the functions of the scutellum are localized in the epithelial
layer is readily shown by experiment. The removal of this layer
immediately results in an absolute loss of the scutellum’s power of
digestion. It is so fully incapacitated that no visible corrosion is
effected upon a contact surface of starch, when previously such effect
was very marked. An epitheliallayer, even when not connected with
the embryo, seems able to accomplish a slight change, even though
no provision for the removal of the products of conversion is made.

The exact way in which the epithelial layer produces diastase is
not known. The change in the plasma, the elongation of the cells,
and the peculiar granular deposit that accumulates at their outer
ends are all probably connected with the exercise of this function.
Indeed, Torrey has gone so far as to assert that this is a deposit of
actual enzymatic substance. He asserts that it appears, gathers at
the outer end of the cell, and then passes into the endosperm, that
the cell stays clear for some time, and that the same phenomena are
then repeated. ‘The writers have not verified this statement beyond
noting that the deposit varied greatly in individual grains which were
killed at different stages of germination. Sometimes the entire end
of the cell was clouded and the outer end heavily charged with a
coarse granular deposit, and at other times it was entirely free.

LOCATION OF DIASTASE SECRETION.

There are two diastases present in the barley grain: One of trans-
location, capable of only weak action; and one of digestion, capable
of powerful corrosion.

The endosperm is incapable of self-digestion other than the slight
action of the diastaste of translocation.

The aleurone layer is made up of highly vital cells, which persist
until the starch endosperm has been almost completely absorbed.

The most rapid starch conversion is next to this layer.

These facts are not sufficient to ascribe any secretive function to
the aleurone layer, the rapid dissolution next to this tissue being due
to the fact that from their nature the adjacent cells are easier to
break down than the ones in the central part of the endosperm. An
even more rapid corrosion follows the furrow, although it is largely
composed of inactive and dead cells. No corrosion is to be found next
to the aleurone layer except as the changes move outward from the
scutellum. The absence of means to remove the products of conver-
sion at the distal end should not prevent the first stage of conversion
taking place if the aleurone layer were an active enzymatic organ.

That the scutellum is active in enzym secretion is shown by the
fact that the first changes occur in the layer of endosperm in contact

18 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

with it, and all later progress in conversion is made from it toward
the distal end of the grain.

The embryo is able to feed upon starch substituted for its normal
endosperm. Living embryos are able to grow when grafted on
endosperms which have been previously killed.

The function of enzym secretion in germination is localized in the
epithelial layer of the scutellum. Embryos from which this layer
has been removed are unable to convert starch.

SOURCE OF CYTATIC AND PROTEOLYTIC FERMENTS.

The location of the secretion of diastase is not the only point in the
physiology of the grain upon which investigators have differed. Some
authorities who have placed this function in the scutellum have
ascribed the formation of cytase and of the proteolytic enzym to
other sources.

With cytase, if the conclusions of the writers be correct, the ques-
tion is soon settled. If starch conversion starts next to the embryo
and moves toward the distal end of the grain, cytase must also be a
product of the epithelial layer. The breaking down of the cell walls
must always precede the action of diastase. The diastase of digestion
seems to be unable to pass readily through unmodified cell walls, and
most certainly the cell walls are not affected much beyond the
depleted zone. These two enzyms, then, must of necessity not only
be associated in the changes which occur in the endosperm, but must
proceed from a common source.

The proteolytic ferments would appear from analogy to present
no differences from the other two. Proteolytic action certainly does
not occur in any part of the endosperm not yet reached by cytase
and diastase. If the proteolytic ferments are secreted by the aleurone
layer they do not become operative until the cytase has moved
forward from the scutellum and has broken down the cell walls.
This lack of plausibility is not proof, but, on the other hand, there is
no reason for thinking that there is more than the single source of
enzymatic secretion. In one or two other grasses any other origin
than the scutellum is apparently impossible, because the aleurone
layer is digested almost as readily as the starch endosperm. In these
cases, at least, the secretion must be a product of the scutellum, and
in barley every indication short of absolute proof insists on the same
conclusion. In the opinion of the writers, the scutellum as a feeding
organ is endowed with all the functions of digestion, being able to
utilize all foods occurring in its natural storehouse, the endosperm.

FUNCTION OF THE ALEURONE LAYER.

These conclusions leave unexplained one very evident fact. The
aleurone layer is obviously a vital tissue... Its cells are in no way
simular to those of the starch endosperm beneath it. This marked

MORPHOLOGY OF THE BARLEY GRAIN. 19

difference can not be without a purpose, and fortunately this pur-
pose is easily explained without the necessity of having recourse to
any theory of secretion. The aleurone layer undoubtedly exercises
a strong protective function. In rainy weather, fungi are invariably
to be found investing the barley grain and feeding upon the feebly
active cells of its envelopes. Their hyphe often run through all the
investing layers of the seed without bemg able to penetrate the
aleurone layer. Whether or not it be the vital resistance of its pro-
toplasm, the mere mechanical obstacle of its heavily cuticularized
walls, or both, this tissue is an effective barrier to the inroads of
molds and bacteria. The fact that such protection is of absolute
necessity is readily appreciated. Within the endosperm is stored the
food upon which the future development of the embryo is absolutely
dependent. Even the perpetuation of the species rests upon the
proper conservation of this reserve food material. This mass of
readily assimilated compounds is an ideal food for all sorts of sapro-
phytic and parasitic organisms. It is therefore not surprising to find
built around this material a specialized tissue with a highly protective
function.

The aleurone layer serves a second purpose, but one which alone
would hardly justify its existence, in that it appears to be more
opportune than essential. When the plant is first establishing itself
in the soil, it utilizes the starch endosperm, a material rich in carbo-
hydrates, which seems to meet all the requirements cf early growth.
When once its green leaves are exposed, however, photosynthesis is
able to supply all its needs for starch. With nitrogenous food mate-
rial the problem is more difficult. A considerable extension of feed-
ing surface in the roots is necessary before such material can be pro-
cured in any quantity. The starch endosperm contains an extremely
limited amount of nitrogenous matter and that stored in the embry-
onic tissues is soon exhausted. The breaking down of the aleurone
layer and the utilization of its highly nitrogenous cell contents comes
at the critical period in the life of the plantlet when this material is
of especial value. This may account for the extra thickness of this
layer in certain genera of grasses, of which Hordeum is one of the
most notable examples.

GREATER DIASTATIC POWER OF SMALL-BERRIED AND OF HIGH-
NITROGEN BARLEYS.

It is interesting to note that the theory of scutellar secretion con-
forms nicely to an apparently satisfying explanation of a widely rec-
ognized fact in the utilization of barley malt. Distillers have long
known that their requirements are best met by a malt of high dia-
static power and that small-berried barleys of high nitrogen content
are best adapted to produce such malt. With those brewers who
are producing a beer in the manufacture of which malt adjuncts, such

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 grain 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
erain 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 grain 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 in the ratio of the

MORPHOLOGY OF THE BARLEY GRAIN. 21

secreting surface to the starch endosperm. The growth of the grain
in such cases is not normal. The stimulation of the vegetative
growth has been greater than the later starch infiltration could
balance. The embryo and general structure of the grain have
attained large proportions, but the starch infiltration has been incom-
plete. A normally grown and matured grain of 2-rowed barley pos-
sesses a highly developed starch endosperm. Although this endo-
sperm is the first part of the grain to commence active growth, it is
the last to be completed in the process of ripening. If any feature of
climate or culture interferes with the process of starch deposition, the
grain remains high in nitrogen content. This excess is due more to
the absence of starch than to the presence of nitrogen. There is,
then, a large scutellum without the corresponding bulk of starch.
The enzymatic secretions intended for the conversion of a large endo-
sperm are more than sufficient for the reduced starch content, and
both diastatic power and nitrogen content are higher than usual.

In substantiation of this view, measurements were made upon two
samples of Princess barley. These were grown at Huntley, Mont.,
in 1911. One sample was produced upon dry land, while the second
came from a neighboring plat which had been irrigated. The thou-
sand-berry weight of the irrigated barley was 45.5 grams, while that
from the dry-land plat was only 30.1 grams. The scutellums in
either case were quite uniform. Those from the irrigated sample
averaged a little less than 2.6 millimeters in diameter, while those
from the dry-land sample fell to 2.4 millimeters. The scutellar areas
were, then, 5 square millimeters for the one and 4.3 square millimeters
for the other. That is to say, under such conditions that the grain
did not develop to its fullest extent the scutellar area was reduced
approximately 14 per cent. However, at the same time, the total
reduction of the grain was 33 per cent. As the hulls are more or less
a constant factor, the actual reduction of. endosperm was probably
far in excess of 33 per cent. This case is but a slight exaggeration of
the conditions of incomplete development that usually obtain over a
considerable part of the upper Mississippi Valley. The scutellum of
2-rowed barleys in this section is, for the most part, likely to be rela-
tively a greater part of the grain than is normally the case in this
group. Such barleys grown in this section are likely to show a much
greater converting power than has been suspected.

EFFICIENCY OF CONVERSION.

If the conclusions of the writers be correct, the application of these
facts to barley production and utilization is of much importance.
If the secretion of enzyms takes place in the epithelial layer, the
eross morphology of the grain must govern its behavior in germi-
nation, including that modified form of germination known as

22 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

malting. The perfection with which an endosperm undergoes diges-
tion depends upon the amount of diastase present and upon the
location of the endosperm with reference to the diastatic source.
It is the aim of malting to carry the disintegration of the en-
dosperm only to that pomt where cytatic action has been com-
pleted and where diastase formation has reached a large total which
has been distributed through the grain. Very little starch conversion
is desired in the process of malting. Indeed, none is desired, since
the sugars thus produced are in part absorbed by the growing plant
and not only lost but changed into undesirable products. The low
temperatures at which the grain is malted are for the purpose of
restraining this con-
version. Every effort
is made to prevent
the absorption by the
plantlet of the con-
tents of the proximal
region of the endo-
sperm before the
enzymatic secretions
have reached its dis-
tal end and have per-
meated the dense
starch areas in the
upper flanks of the
grain. When this is
attained the embryo
is killed to prevent
any further absorp-
tion. The object of
malting is, therefore,
Fic. 4.—Two grains of aBohemian barley; a broadly oval-shaped grain to subject all parts
well adapted to malting with little loss. of the endosperm to
the initial effects of enzyms with as little loss as possible. The ideal
condition would be a simultaneous attack upon every cell wall and
every grain of starch. This is impossible with the source of the
action localized at one extremity of the grain. However, the coordi-
nation of the scutellum with the endosperm has a marked effect.
The shape of the grain with reference to the size and shape of the
associated embryo has in more than one variety been the deciding
factor between a good and a poor malting barley. If the great mass
of the starch be near the embryo, as in the short, thick grain shown
in figure 4, the disintegration of the endosperm is readily and uni-
formly accomplished, but if it be distant, as in long, slender grains,
the complete modification of the endosperm mass can not be accom-

MORPHOLOGY OF THE BARLEY GRAIN. 23

plished without great loss. That is, the more nearly a grain ap-
proaches a sphere in shape, the less need be the loss in malting; and
the greater the ratio of the longer axis of the grain to the shorter the
more difficult becomes the malting. In extreme types, such as the
Chinese barley shown in figure 5, efficient malting is impossible. If
the process is stopped in a reasonable time, there remains an unaffected
portion at the distal extremity, whereas if germination is continued
until this portion becomes softened, the entire proximal end will have
been utilized by the plant. The 2-rowed barleys from Smyrna are
less marked examples of the same defect. They are almost ideal in
character, considered
from the standpoint of
high extract alone, ex-
cept for their unfortu-
nately long grain. The
shape of the grain makes
this barley difficult to
malt, and the extract is
probably measurably
less than would be the
case if the same seed
contents were differently
arranged. Barleys with
long grains and with
pointed ends are to be
avoided for malting pur-
poses, if yield of extract
be even of secondary
interest.

The amount of diastase
present in any type of
barley must depend upon
the area and vigor of the F!G- 5.—Two grains of a Chinese barley, a spindle-shaped grain

: 6 very difficult to malt.

secreting surface. If the ;

secreting surface be large, enzymatic action should be ample. As
previously pointed out, the proportion of the secreting surface must,
by the laws of geometry, increase as the size of the berry decreases.
Thus, in small-berried barleys the diastatic power will be high, regard-
less of the nature of its endosperm. If, in addition, the endosperm be
dwarfed by a lack of normal starch infiltration, resulting in a high-
nitrogen grain even for its class, the excess of diastase becomes still
greater and results in a malt adapted to the use of distillers. The
question of increasing this function in such barleys thus seems super-
fluous. Nevertheless, as will be shown later, even in the case of the

24 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

Manchuria and Oderbrucker barleys, the nature of the secreting sur-
face is of importance.

As the size of the grain increases, the efficiency of the converting
power becomes a vital question. The relative decrease of the sur-
face of the epithelial layer, together with the increased percentage
of starch in the endosperm, makes an adequate amount of diastase
of the utmost importance, especially if it be desired to convert
starch in addition to that already in the endosperm. ‘To have the
largest contact area, the embryo must completely occupy the prox-
imal end of the grain, and the grain itself must be as broadly oval
as possible in order to provide for this maximum expansion. When
these conditions are fulfilled, the resulting scutellum is a broad organ,
reaching well over the shoulders of the grain and resting in a shallow,
saucer-shaped depression in the endosperm.

To test the accuracy of this conclusion, examinations have been
made of almost every commercial barley in the world. Several of
the types found are shown in Plate V, figure 2, and in Plates VI and
VII. In all cases where the grains were large, the varieties recog-
nized as superior malting barleys each possessed a scutellum of the
above type. On the other hand, barleys known to be inferior for
malting were invariably characterized by the other extreme of
scutellum, that is, by one which did not reach out over the shoulder
of the grain. Usually a slight compensation for defective breadth
of scutellum was offered by its being deeply sunken in the endosperm.
This addition of surface was shght, as it must be readily realized that
the increase of the few degrees of surface secured could not offset the
very considerable decrease of diameter. The comparative area of
the spherical surface of the large scutellum is actually greater than
that of the slightly elongated, small one, so that the broad, flat type
of necessity presents the greater secreting surface.

There seems to be a more or less definite correlation between the
shape of the scutellum and the form of the grain. A long, pointed
grain is almost invariably accompanied by a narrow, deeply sunken
scutellum. Of course, the fact that the proximal end was reduced
would of necessity cause a like reduction of the embryo. However,
even more than such inevitable restriction usually occurs. In such
grains the borders of the scutellum in a moistened grain do not ordi-
narily protrude at the points of contact with the aleurone layer, but
are even more narrow than the available space requires. In a very
few types, as the Smyrna, this is not wholly true.

While the most important factor of enzymatic production is thus
seen to be the surface area of the secreting organ, there is still an
additional element. There may be a difference in the quality of the
secreting tissue. In other words, the epithelial layer varies with
reference to the character of its cells. In some barleys it is made up
of short, broad cells; in others the units are long and narrow. (See

Bul. 183, U. S. Dept. of Agriculture. PLATE V.

Fig. 1.—PHOTOMICROGRAPH OF THE SCUTELLUM OF A GERMI-
NATING GRAIN WITH ITS EPITHELIAL LAYER.

In the ends of the cells of the epithelial layer (¢) is to be seen the
black deposit, thought by Torrey to be diastase. In front of the
epithelial layer the endosperm has been reduced to a milky
polution, while the scutellar cells back of it are obviously highly
vital.

Fic. 2.—TWO GRAINS OF FINNISH BARLEY.

A grain of undesirable spindle shape and a small, insufficient
scutellum.

Bul. 183, U. S. Dept. of Agriculture. PLATE VI.

Fia. 1.—TWo GRAINS OF PLUMAGE BARLEY.

This barley was originated by E.S. Beaven, Warminster, England.
It is a grain of desirable oval shape and has a broad, ample scutellum,
a combination of characters adapted to secure the highest percentage
of malt extract.

Fig. 2.—TWO GRAINS OF AN ASIATIC BARLEY.
A grain of fairly oval shape, but witha small, insufficient scutellum.

MORPHOLOGY OF THE BARLEY GRAIN. 25

fig. 6.) Given the same area in contact with the endosperm, the
epithelial layer composed of long cells will have a much greater cubical
content. Also, if the cells be narrower, their total number will be
greater in a given area. If Torrey’s conclusion that the nucleus is
the final organ to which secretion is due is correct, this increase in the
number of cells and in the consequent number of nuclei is an actual
increase in secreting power. In any ease, it is reasonable to assume
that a greater number of cells with a greater plasmic content is more
efficient than a smaller number of celis with a smaller plasmic content.
The existence of this type
of epithelial layer in the
most prized malting bar-
leys gives corroboration to
this belief. The long, nar-
row cell prevails in the bet-
ter sorts, but becomes less
prominent as the quality
decreases.

An ideal grain of barley,
then, is one possessing a
relatively short longitudi-
nal and a correspondingly
long transverse diameter,
with both the distal and
proximal ends broadly oval.
It contains an embryo with
a large scutellum reaching
over the edges of the endo-
sperm and an_ epithelial
layer composed of long,
narrow cells.

An inferior grainof barley

Fig. 6.—T wo types of epitheliai layers: A, An inferior epithelial
layer of short, broad cells; B, an eilicient epithelial layer of
is elongated and is pointed long, narrow cells. (Camera lucida drawings of actual

¢ specimens. )
at both ends. It contains

an embryo with a narrow scutellum the epithelial layer of which is
made up of short, broad cells.

A barley having the most perfect construction for the production of
enzyms may still fall short of its highest efficiency. The size and the
quality of the secreting surface are the structural factors of potential
energy, but they are limited by a third element, namely, condition.
If they are not in the highest state of vital energy, their maximum
efficiency will not be realized; and, furthermore, this vital energy
must be in a certain state of activity not entirely understood and
difficult to define, which may be designated, for want of a better
term, as ‘‘potency.’’ For example, at the time of the maturity of the

26 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

grain the protoplasm of the cells of the embryo is active and possessed
of all the vitality of newly formed tissue, yet barley germinates very
imperfectly at this time. The epithelial layer will attack the endo-
sperm, even under the most favorable conditions of moisture, tem-
perature, ete., only in a weak, erratic manner. The cells do not seem
ready to exert their full force. In fact, it is only after a certain
period of rest that the grain displays its full germinative potency and
becomes thoroughly re-
sponsive to germinative
influences.

It has been noticed
that the “sweating”
process in the curing of
barley is closely con-
nected with this change
in the internal energy of
the grain. If grain be
sweated in the stack,
both the percentage and
the vigor of its germina-
tion are increased to the
maximum. Any other
method of treatment
after cutting is inferior,
the changes being
brought about under
more adverse conditions.
If the curing process
takes place in the shock,
it occurs irregularly and
imperfectly and at the
same time the grain is

FiG. 7.—Two grains of barley from a commercial sample, showing exposed to the weather.
the extremes of variation to be found in barleys as grown at pene B cary aS :
present in this country. Economical malting ofa barley that If it Oca an the bin,
contains any considerable percentage of such extreme shapes there 1s danger of over-

ae a heating and consequent
damage. The vigor of germination may be affected in this way even
when there is no visible indication that deterioration has occurred.
Of course the injury is likely to be more serious and even to make
the use of the barley for malting purposes impossible.

These various factors of efficiency in the conversion of the barley
erain, when applied to commercial malting operations, presuppose
pedigreed barley. The efficiency of the ordinary market barley may
be increased by careful culture, but it will never become really supe-
rior. The commercial varieties as they are sold in the markets are
composed of many subvarieties (fig. 7). The Manchuria, the Oder-

MORPHOLOGY OF THE BARLEY GRAIN. oN

brucker, and the Bay Brewing usually represent mere group names for
general types of barley that are in no sense pure varieties. From each
of them many widely different strains may be isolated. Some of these
are early and some late, some are large berried and some small ber-
ried, some germinate quickly and some slowly. When such a mix-
ture is malted, it is obvious that the malt must be lacking in uni-
formity. Some of the acrospires will be protruding and some barely
started. Some of the grain will be overmalted and some undermalted.
The percentage of extract must necessarily be much lower than might
be procured from any one element of the mixture if the elements were
separated.

The purifying of the common commercial varieties will result in a
more uniform malt and a higher percentage of extract. Any further
step toward a greater efficiency must fall back on the use of 2-rowed
barley. For botanical reasons, a 6-rowed variety can never be made
as uniform in the size and character of its grain as a 2-rowed. Cer-
tain usages in manufacturing not germane to this discussion may
demand 6-rowed varieties, but, considered only from the standpoint
of yield of extract, the 2-rowed sorts will always remain superior.

AMERICAN BARLEYS.

The application of the factors of endosperm conversion to Ameri-
can conditions is more simple than the diversity of production and
demand might indicate. There are in the United States but three
main barley-producing areas, the Pacific coast region, the Rocky
Mountain irrigated sections, and the upper Mississippi Valley. In
the three Western States, California, Oregon, and Washington, the
climatic conditions are such that a barley peculiar to that section is
produced. The dry, sunny ripening season results in a starchy grain
of very low nitrogen content. This is true regardless of variety,
though variety exercises a noticeable influence. As a whole, all vari-
eties of this district are large grained. Even the common California
barley, which is 6-rowed, possesses a grain of greater size than many
of the 2-rowed varieties grown elsewhere. Indeed, even when grown
in the Plains States it maintains its relatively high thousand-berry
weight. Regardless of variety, the problem in the West is, therefore,
to secure all the enzymatic development possible. The large amount
of starch endosperm to be converted makes this desirable. Although
any grain possesses enough diastatic power for the conversion of its
own endosperm, for malting purposes an excess is useful even though
it is not used for the conversion of additional starch. A more uni-
form malt can be made by holding back a powerful diastase that
evenly floods the endosperm than by the action of a lesser quantity
that must pass from cell to cell in a more fitful attack.

In the Rocky Mountain area, the starch formation is usually not so
pronounced as nearer the coast. The secreting surfaces in most vari-

28 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

eties are satisfactory, even to the extent of supplying surplus malting
energy.

The upper Mississippi Valley is a section of high-nitrogen barleys.
For the most part the crop is of the small-berried 6-rowed Manchuria
or Oderbrucker type. It is in this region that the greatest divergence
of demand is felt. A majority of the malt consumers of the North-
west use malt adjuncts. Indeed, this custom may be said for all
intents and purposes to be universal. They demand a barley of high
diastatic power, so as to convert the various forms of grits added to
the normal starch endosperm of the malt. This demand is not in
conflict with the facts of scutellar secretion. The diastatic power of
small-berried barleys is simply a matter of the shape and size of the
scutellum. If this power can be increased in any barley, it can also
be increased in Manchuria barley. <A greater diastatic power would
allow the use of a grain with a larger starch endosperm and would
result in a higher percentage of extract without any loss in the desired
excess of diastatic energy. The Manchuria as it is sold on the Chi-
cago markets does vary considerably in this respect. The compari-
son of a good-malting Manchuria with a poor-malting Manchuria bar-
ley showed that in the good barley 83 per cent of the grains had a
scutellum of desirable type, while in the poor barley only 16 per cent
were of this type.

Two-rowed barleys grown in the upper Mississippi Valley are likely
to be much more vigorous in enzymatic action than has been thought.
From all the tests of the writers these barleys are shown to be of
rather high nitrogen content. This means that the grain possesses
an embryo stimulated to a growth such as would provide diastase for
an exceptionally large endosperm. It also means that such an endo-
sperm has not been developed, that much of the space in the starch
cells is occupied by proteid contents, and that these cells will be com-
paratively easily broken down. Such being the case, it is more than
probable that 2-rowed barleys grown in Wisconsin, Minnesota, Lowa,
and the Dakotas will be found to be able to convert a considerable
amount of added starch, if handled so as to develop their greatest

efficiency.
MODIFICATIONS POSSIBLE BY CULTURE.

The scope of this bulletin does not admit of a full consideration of
one subject intimately connected with barley structure, namely, the
great changes produced by different methods of cultivation, for a full
understanding of this subject would involve a discussion of principles
of plant breeding and methods of barley farming too extensive to
be herein included. But at least a brief statement of the correlation
between the two is necessary at this point. It may be said in general
that efforts to obtain by means of culture barleys of high enzymatic

Bul. 183, U.S. Dept. of Agriculture. PLaTE VII.

Fic. 1.—TWo GRAINS OF AN ABYSSINIAN BARLEY.

This is a fairly well-proportioned grain with a fairly ample scutellum.

Fic. 2.—Two GRAINS OF STANDWELL BARLEY.

The broad scutellum and the thick oval grain are adapted to secure a
very high percentage of malt extract.

Bul. 183, U. S. Dept. of Agriculture. PLATE VIII.

Two SAMPLES OF PEDIGREED PrRimuS BARLEY GROWN THE
SAME SEASON AT DIFFERENT POINTS IN THE UNITED
STATES, SHOWING THE EFFECT OF SOIL AND CLIMATE ON
THE SCUTELLUM.

In Athe scutellum has degenerated, while in B it has remained of
desirable shape.

MORPHOLOGY OF THE BARLEY GRAIN. 29

power will be most likely to succeed if they are directed separately
toward the four factors of efficiency, viz: (1) The shape of the grain,
(2) the size of the scutellum, (3) the quality of the epithelial layer,
and (4) the vital energy of the mature grain. All of these factors but
the last are varietal characters. Fortunately, varieties of extreme
inferiority are for the most part already eliminated because of their
low yield. The only decidedly inferior ones often met with in actual
cultivation in America are certain Russian barleys with long, thin
grains, a few winter varieties of similar character, and hooded sorts
that probably are abnormal in form because of the lack of the func-
tional activity of the beard.

Among the varieties the normal qualities of which are desirable,
it not infrequently happens that the actual product is far from
perfect; for ideal shape is largely a matter of development, even in a
variety in which such is possible, and not only a matter of develop-
ment but of ideal development. If the conditions of soil and cultiva-
tion are satisfactory and the climate such as will allow a correct
maturation, the whole crop will consist of good, uniform seed. If
these conditions do not prevail, a faulty product will result. Soil and
cultivation are under the control of the farmer, at least to a limited
extent, and it is the neglect of these limited influences that is respon-
sible for much of the inferior barley produced. The English farmer
has a saying that “barley isa gentleman;”’ that is to say, if the ideals
of structure in this grain and the delicately balanced physiological
functions based on structure are to be secured, barley, above all other
crops, can not be treated with indifference.

The more general influences affecting adversely the cultivation of
the best grades of barley by the American farmer may be briefly
outlined as follows: (1) Overstimulation of purely vegetative growth
by improper soil and fertilization, (2) unfavorable climatic conditions
during the growing period, the factor which explains why the southern
limit of good barley cultivation in the Mississippi Valley is so far
north, and (3) improper methods of harvesting and curing the barley
crop.

It is probable that the part of the barley grain most quickly and
extensively modified by changes in the conditions of cultivation is
that organ which occupies so prominent a place in these discussions—
the scutellum or malting organ. Under adverse conditions or when
vegetative development is unduly accelerated, the scutellum of even
the best pedigreed barleys does not retain its excellence. (See PI.
VIII.) The difference between a barley having a good scutellum
and one having a poor scutellum is therefore not that the good one is
constant, but that under favorable conditions it and it alone will prove
to be superior. Normality of development is the means of attaining

30 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

the highest success in any form, and any methods that will secure
normal development will secure an ideal shape of scutellum, so far
as the barley under consideration is capable of such development.

To what extent ideals in barley morphology, and especially in the
form of the scutellum, may be affected by breeding, is not as yet fully
known. ‘There are many barleys which never produce a desirable
malting organ. There are others which, under favorable conditions,
invariably do. These facts indicate a usable varietal difference.
Whether or not experiments in breeding such hopeful varieties will
result in stable forms of seutellum having ideal shape and in epithelial
layers having maximum enzymatic power can not at present be stated.
But it is safe to assume a priori that these organs are as plastic and
capable of improvement as those other parts of the barley plant, such
as the shape of the head, the rigidity of the straw, etc., which have
been so extensively modified by modern breeding methods. And
when these morphological changes are brought about, the writers
are certain that the functional qualities which these studies have
demonstrated to be correlated with them will show a truly parallel
improvement.

In the trials at St. Paul, Minn., in cooperation with the Minnesota
Agricultural Experiment Station, a 6-rowed strain with an unusually
large scutellum has been isolated from a mixed culture. As it was
weak in point of yield and in strength of straw, crosses were made
with it upon the Manchuria variety. The large scuteilum was trans-
mitted to the F, hybrids. In the F, generation the large scutellum
was retained, but correlated with the weakness of straw and lesser
yield of the better malting parent. One or two plants, however,
seemed to be more intermediate in character, and if these breed true
in the third generation they may form the basis for a superior strain.

FOREIGN BARLEYS.

A word should be said upon the question of the importation of
foreign barleys. Barleys of superior quality are readily found
abroad, and it would seem a simple matter to select the ones which
most nearly satisfy American requirements and to import them for
dissemination in this country. The results are, however, uniformly
disappointing. The quality of such barleys is in a large part due to
their adaptation to their local climatic and soil conditions. Trans-
ferred to this country they at once present other characters. In time
they become acclimated, but with a few exceptions, such as the
Svalof Svanhals, their performance is far from encouraging. The
truly successful barleys of the future must be bred in this country.
It may be that they will come from foreign stocks; indeed, there are
no native sources of seed. New introductions of mixed races are, as
a whole, much better material for the selection of breeding strains

MORPHOLOGY OF THE BARLEY GRAIN. ait

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
ovary, 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-
trifugalorder. 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.

On BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE.

The efficiency of conversion depends upon the shape and compo-
sition of the grain and upon the relative quantity of diastase secreted.
The quantity of diastase in turn is dependent upon the size, vigor,
and condition of the epithelial layer. The greatest secreting area for
a given grain is secured with a scutellum extending well over the
edges of the adjacent endosperm, the greatest vigor in an epithelial
layer of long, narrow cells, the highest condition of efficiency in a
well-matured, well-cured grain.

The ideal grain of barley is one that is broadly oval with a seutellum
of the type described. If a large yield of malt extract is desired, the
size of the grain should be large; if diastase be the main consideration,
the size should be smaller.

Barley grains with pointed ends and a narrow scutellum are to be
avoided. Poorly matured grain should also be avoided.

The highest type of the barley grain is secured only when climate,
culture, and variety are all favorable.

Pedigreed varieties are essential for securing barleys of superior
morphological and physiological quality. Such varieties must for the
most part be produced in this country, as imported pedigreed stocks
are seldom satisfactory.

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AT

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V

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1915

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