198 
Journal of Agricultural Research 
Vol. XXIII, No. 3 
The aleurone layer (b) is of relatively thick-walled cells, but the walls 
are not pigmented. Its thick walls, continuity, and persistent adherence 
to the integument are of interest in connection with the suggested pro¬ 
tective roll of this layer in grass caryopses (7). 
C 
Fig. 4.—Median sagittal section through the coverings of a Johnson grass caryopsis at 
its distal end: A, flat, or endosperm side of caryopsis; B, embryo side of caryopsis; 
C, base of style, (a) inner integument, (i) inner walls of its cells, (2) inward thicken¬ 
ings of same, (3) end walls showing folds, (b) aleurone layer, (c) outer epidermis of 
pericarp. X 100. 
Of the pericarp only its outer epidermis (c) is clearly and definitely 
distinguishable in freezing microtome sections. The figure shows the 
base of one of the persistent styles (C). 
MICROPYLE AND SURROUNDING STRUCTURES 
Figure 5 represents a median sagittal section through the micropyle 
of a Johnson grass caryopsis. The position of the micropyle with refer¬ 
ence to other structures can be seen by comparing this figure with figure 
2. The aleurone layer (fig. 2, 1 ; 5, a) on the embryo side of the caryopsis 
extends several cells beyond the proximal end of the scutellum (fig. 2, a; 
5, b), but falls several integument cells short of reaching the micropyle. 
The micropyle itself (fig. 5, c) is closed by the cells of the inner inte¬ 
gument (d,d) which has so crowded in from all directions as to become 
turned back upon itself externally, the cells from opposite directions 
coming together but without the walls fusing. The inner cells of the 
double layer thus formed (e) are greatly elongated in a radial direction 
and have very heavy, densely pigmented inner walls. The cells of the 
outer layer (f) are considerably shorter and their outer (morphologically 
inner) walls are thick and heavily pigmented. On the side toward the 
hilum this reversed layer of inner integument cells extends within 2 or 
3 cells of the edge of the hilum (g) and forms a conspicuous hump. In 
