SEEDS AND FRUITS. 133 
Comparison of cross and longitudinal sections shows that we have 
here a straight embryo lying in the centre of the seed, with its 
radicle pointing towards the caruncle, and a pair of flat, beauti- 
fully veined seed-leaves closely pressed together. There is no 
evident plumule. Surrounding the embryo is a cheesy substance, 
the albumen, which fills up the space between it and the seed- 
coat. With care, it can be scraped away, leaving the embryo 
entire. The seeds of violet can be understood after examina- 
tion of the preceding, but the embryo is much smaller in propor- 
tion (cf. fig. 53), while in buttercup (fig. 30) and larkspur most 
of the seed is occupied by albumen. In all these 
cases the nutritive matters are formed in the 
embryo sac, which increases in size and fills up 
the whole of the space within the seed-coat. Such 
albumen is called endosperm. In a few cases, 
however, the embryo sac, with its contained endo- 
sperm, is comparatively small. Most of the albu- 
men is in this case perisperm, and belongs to the 
nucellus. 
Examine now a grain of maize (Indian-corn). ,,, pia 
This is really a fruit, as it includes the wall of © of “Albuminous 
the ovary, here dry and closely adherent to the SSh,yo eu 
seed. A little pointed projection on the broad end — rounded by en- 
of the grain is the remains of the style. The yellow ‘°°?"™ 
part of the grain is endosperm, but on one side, near the pointed 
base, is a whitish patch. This is the embryo, situated, as in all 
grasses, outside the endosperm. It can be detached from a soaked 
grain; and careful scrutiny will show that radicle and plumule 
are wrapped up in a single seed-leaf or cotyledon, part of which is 
closely applied to the endosperm, and receives the special name 
of scutellum. By cutting through a grain longitudinally, taking 
care to halve the embryo, the relation of parts will readily be 
understood, and a loose, white region of the endosperm will be 
seen (fig. 54). Grains of wheat, barley, and oat may usefully be 
compared with maize. All of them possess a single seed-leaf, 
which is a leading character of monucotyledons. A date-stone 
is a monocotyledonous seed of different type. Here the endo- 
sperm is horny, and composed of thickened cellulose cell-walls. 
On one side of the stoneis a groove; in the centre of the opposite 
side the micropyle will be found as a small depression. By cut- 
ting the seed transversely across through this, a small embryo will 
be found, its radicle directed towards the micropyle. The cotyle- 
don is sheath-like, and encloses a microscopic plumule. 
A huge seed belonging to the same class of plants is the cocoa- 
nut. The hard shell does not belong to the seed, the coat of 
