228 
THE PLANT WORLD. 
embryo. Without the aleurone layer, again, lies the pericarp, 
which is, as one may see, torn and ragged and therefore incom¬ 
plete. This is due to its adhesions to the chaff, which when torn 
away took some of the pericarp with it. The whole series of 
tissues is shown in the next figure (Fig. 44), which is taken from 
a hand section. It is not very thin, and in consequence does 
not show the minutiae very distinctly. It does, however show 
distinctly the chaff ( sp .), the pericarp {Per) and the aleurone 
layer (a/), with the starchy endosperm, of course, within. It 
is thus clear that, if the origin of the pericarp has been cor¬ 
rectly traced, the barley-corn is a caryopsis, i. e., a seed (= endo¬ 
sperm and embryo) enclosed by a tightly investing ovary wall 
or pericarp, the whole covered by the two chaffy paleae or “spelt,” 
as they are called by the brewers.* 
The remainder of the endosperm is composed of cells, less 
regular in form than those of the 
aleurone layer, which, with the ex¬ 
ception of some of the outer ones, 
immediately beneath the aleurone 
layer, from which starch is absent, 
are all packed with starch. These 
may be seen in Fig. 43, in which 
the cells with very dark contents 
(starch stained with iodine) are 
seen not to come quite up to the 
regular, thick-walled aleurone cells. 
The lighter irregular portion thus 
distinguished is composed of the 
cells referred to, which do not contain starch. 
Returning to Figs. 40 and 41 we note that the embryo lies 
against the endosperm. The part which touches the endosperm 
is the scutellum {Sen, Fig. 41), an organ which secretes digestive 
principles and absorbs the food materials from the endosperm 
after they have been digested, and thus prepared for the use of 
the sprouting plantlet. The part especially active in secretion 
is the epithelium, a layer of columnar cells {sen. epi Fig. 42. It 
may be traced also in Figs. 41 and 42.) Fig. 42 shows also very 
nicely some of, the remnants of the disintegrated endosperm. This 
* From the German Spelze . 
Fig. 44. A portion of trans¬ 
verse section through the chaff 
(Sp.), pericarp (Per.) and 
endosperm. Al., the aleurone 
layer, under which is the starch- 
containing tissue. 
