Em′bryo (in plants), a plant in the earliest
stages of its development. In Spermatophytes
Embryo of capsella, showing superior (below) and embryo (above) in various stages of development.
the name
is restricted to
the development
within the seed.
Taking the bean
embryo as an
illustration, it
consists of a
small stem, once
called the caulicle,
but now
known as the
hypocotyl, from
the lower end of
which the root
develops, and at
the upper end
two large and fleshy leaves appear (the halves
of the bean), called the cotyledons.
Between the cotyledons a little bud is
apparent, called the plumule, in which
the subsequent leaves are more or less
formed, and which is to develop into
the shoot when the embryo escapes from
the seed. Such an embryo represents the
common form among the dicotyledons.
Among the monocotyledons, as in corn, the
same parts appear, but the single large
cotyledon is terminal on the hypocotyl, and the
stem tip comes out at one side. Among the
conifers, as in pines, a rosette of cotyledons
may appear, in the center of which is the
plumule. In the development of the
embryos of seed-plants a temporary organ,
called the suspensor, usually appears. It
generally is a more or less elongated
filament of cells, which at its tip
bears the cell which is to form the
real embryo, and by its growth places
this cell in a better position in reference
to the food-supply which is forming in
the seed.