196 
Journal of Agricultural Research voi. xxiii, no. 3 
micropyle (p) is the aleurone layer (1), which comprises a single layer 
of cells. 
Between the hilum, the starch-bearing endosperm, and the proximal 
end of the scutellum lies a light-colored mass of large, irregular, com¬ 
pressed, empty endosperm cells (r). 
The coverings of the caryopsis consist of the fused product of the peri¬ 
carp and inner integument—the latter of a single layer of cells which, at 
the distal end of the caryopsis, are much elongated and have very thick 
inner walls. The figure shows these elongated cells of the inner integu¬ 
ment (s), a portion of one of the persistent styles (n), and the pedicel (o), 
with portions of the adhering lodicules. Usually, however, the caryopsis 
breaks from the pedicel at a point just distal to the insertion of the 
lodicules, so that these are not present on the hulled caryopsis. 
The outer integument and nucellus have entirely disappeared in the 
mature caryopsis, with the possible exception of a portion of the former 
overlying the micropyle. 
As already stated, complete or partial removal of the coverings over 
the embryo greatly increases the readiness with which Johnson grass 
caryopses germinate. 
III. DETAIL OF THE PERICARP AND INNER INTEGUMENT 
Figure 3 represents the pericarp and inner integument of a Johnson 
grass caryopsis as seen in cross section about midway from the proximal 
end to the distal end of the caryopsis. 
The drawings in this figure were 
made with camera-lucida and oil im¬ 
mersion lens from paraffin sections 
15 7r in thickness, stained with iron 
alum haematoxlyin. The material 
used had not been bleached or other¬ 
wise altered before embedding in the 
paraffin. Figure 3, A, was drawn from 
the flat (endosperm) side of the cary¬ 
opsis opposite the end of the scutellum, 
and figure 3, B, from the rounded side 
over the end of the embryo (1) and 
adjacent endosperm cells (2). 
The pericarp consists of several 
layers of cells of which only the outer 
epidermis (a) and the inner epidermis (b) are clearly distinguishable. 
The intervening layers consist of greatly compressed thin-walled cells, in 
which narrow cell lumena and intercellular spaces appear only at irregular 
intervals. One of these layers is the chlorophyll-bearing layer of the 
earlier stages of development of the caryopsis and in the mature fruit 
frequently contains starch grains. The outer epidermis is continuous 
and slightly undulating in surface contour and consists of rather large 
rectangular cells, with relatively thin walls and large lumena. The 
inner epidermis, as in other Gramineae, is fragmented longitudinally into 
long tubular cells, extending lengthwise of the caryopsis and connected 
with each other by their end walls, occasionally by their lateral walls, and 
by cells extending diagonally at infrequent intervals. In cross section 
these cells usually appear circular or broadly elliptical as in figure 3. 
The inner integument (c) is a single-cell layer, continuous except at 
the hilum. The cells are much larger than any of the cells of the pericarp. 
Fig, 3.—Cross sections of the fused pericarp and 
inner integument of Johnson grass caryopsis: 
A, from flat (endosperm) side of caryopsis at a 
point opposite the end of the scutellum; B, from 
rounded (embryo) side over the end of the 
embryo (i) and adjacent portion of the 
endosperm (2), showing outer epidermis of 
the pericarp (a), inner epidermis of the peri¬ 
carp (b), inner integument (c), its inner walls 
(d), its side walls (e), and its outer walls and 
solidified contents of the cells (f) X 325. 
