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. 
