The New Student's Reference Work/Cell
Cell (in plants), the unit of structure in the bodies of plants and animals. The bodies of the smallest plants consist of a single cell, while those of the more complex plants consist of very many cells. The free cell is approximately globular in outline, but if pressed upon by neighboring cells it may become variously modified in form.
PLANT CELLS OF DIFFERENT AGES
Bounding the ordinary plant-cell,
there is a thin elastic wall composed
of a substance called cellulose. This cell-wall
forms a delicate sac within which
there exists the living substance called
protoplasm. It is this substance which
is alive and works, and has really formed
the cell-wall about itself. The protoplasm
of a living cell is organized into various
ULOTHRIX, SHOWING THE FORMATION, ESCAPE AND BEHAVIOR OF SWIMMING CELLS
structures,
which have
different duties.
One of the most
conspicuous
structures is a
more compact
mass of
protoplasm, usually of
spherical form,
which is called
the nucleus. The
nucleus is
imbedded in the
less dense
protoplasm, which
receives the general name cytoplasm. In
addition to its power of growth the living
cell is also able to divide itself into
two cells. The process of ordinary cell-division
is an exceedingly complicated one, and
is known as mitosis or karyokinesis. It
is this power of self-division which enables
a single cell, such as an egg, to produce
eventually a complex body composed of
numerous cells.