252 VEGETABLE PHYSIOLOGY 
or nodule of secreting cells, which must be regarded as a 
rudimentary gland, though it is not provided with any 
definite outlet or duet. 
In the seed of the cereal grasses there is a special organ 
separating the embryo from the endosperm. This structure, 
which is a modification of part of the cotyledon, is known 
as the scutellum (fig. 119); its function is to effect the 
absorption of the nutritive material of the endosperm, and 
supply it to the growing embryo. This scutellum is covered 
on its outer face, which is in contact with the endosperm, 
by a layer of cylindrical cells, whose long axis is at right 
Fie. 120.—Srction oF PoRTION OF 
ScurELLUM oF BARLEY, SHOWING 
p, plumule; 7, radicle; s, scutellum. THE SECRETING EPITHELIUM. 
Fia. 119.—Srcrion oF Oat-GRaAIN. 
angles to the surface (fig. 120). These cells are very 
granular in appearance, and form a very marked secreting 
tissue, producing two enzymes, which are subsequently 
discharged into the endosperm to effect the digestion which 
must precede absorption. The aleurone layer of the same 
grain (fig. 121), which has already been described, is also 
a secreting layer, resembling the outer layer of the scutellum 
in several respects. 
The tentacles of the leaves of Drosera, to which allusion 
has already been made, are very definitely secreting struc- 
tures; in addition to preparing an enzyme they produce 
a weak acid, both of which are present in the glairy material 
that they pour out over the captured insect. These tentacles 
