8 BULLETIN 183, U. S. 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. 
Gernhnation 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 gram, 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 slightly. Brown and Mor- 
ris 1 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 laminae 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 
i Brown, H. T., and Morris, G. H. Researches on the germination of some of the Gramineae, part 1, 
Journal, Chemical Society [London], v. 57 (Transactions), p. 458-528, 1890. 
