which composed the
entire plant, while, on the other hand, no such view was taken of the
elementary parts of animals."

ROBERT BROWN AND THE CELL NUCLEUS

In the year 1833 a further insight into the nature of the ultimate
particles of plants was gained through the observation of the English
microscopist Robert Brown, who, in the course of his microscopic studies
of the epidermis of orchids, discovered in the cells "an opaque spot,"
which he named the nucleus. Doubtless the same "spot" had been seen
often enough before by other observers, but Brown was the first to
recognize it as a component part of the vegetable cell and to give it a
name.

"I shall conclude my observations on Orchideae," said Brown, "with a
notice of some points of their general structure, which chiefly relate
to the cellular tissue. In each cell of the epidermis of a great part
of this family, especially of those with membranous leaves, a single
circular areola, generally somewhat more opaque than, the membrane of
the cell, is observable. This areola, which is more or less distinctly
granular, is slightly convex, and although it seems to be on the surface
is in reality covered by the outer lamina of the cell. There is no
regularity as to its place in the cell; it is not unfrequently, however,
central or nearly so.

"As only one areola belongs to each cell, and as in many cases where it
exists in the common cells of the epidermis, it is also visible in the
cutaneous glands or stomata, and in these is always double--one being on
each side of the limb--it is highly probable that the cutaneous gland is
in all cases composed of two cells of peculiar form, the line of union
being the longitudinal axis of the disk or pore.

"This areola, or nucleus of the cell as perhaps it might be termed,
is not confined to the epidermis, being also found, not only in the
pubescence of the surface, particularly when jointed, as in cypripedium,
but in many cases in the parenchyma or internal cells of the tissue,
especially when these are free from the deposition of granular matter.

"In the compressed cells of the epidermis the nucleus is in a
corresponding degree flattened; but in the internal tissue it is often
nearly spherical, more or less firmly adhering to one of the walls,
and projecting into the cavity of the cell. In this state it may not
unfrequently be found in the substance of the column and in that of the
perianthium.

"The nucleus is manifest al