ture of the full-grown sporophyte, but
almost any other common fern will answer. The maiden-hair fern is
common in rich woods, and may be at once recognized by the form of its
leaves. These arise from a creeping, underground stem (Fig. 67, _C_),
which is covered with brownish scales, and each leaf consists of a
slender stalk, reddish brown or nearly black in color, which divides
into two equal branches at the top. Each of these main branches bears
a row of smaller ones on the outside, and these have a row of delicate
leaflets on each side (Fig. 67, _E_). The stem of the plant is
fastened to the ground by means of numerous stout roots. The youngest
of these, near the growing point of the stem, are unbranched, but the
older ones branch extensively (_C_).

On breaking the stem across, it is seen to be dark-colored, except in
the centre, which is traversed by a woody cylinder (fibro-vascular
bundle) of a lighter color. This is sometimes circular in sections,
sometimes horse-shoe shaped. Where the stem branches, the bundle of
the branch may be traced back to where it joins that of the main stem.

A thin cross-section of the stem shows, when magnified, three
regions. First, an outer row of cells, often absent in the older
portions; this is the epidermis. Second, within the epidermis are
several rows of cells similar to the epidermal cells, but somewhat
larger, and like them having dark-brown walls. These merge gradually
into larger cells, with thicker golden brown walls (Fig. 67, _I_).
The latter, if sufficiently magnified, show distinct striation of
the walls, which are often penetrated by deep narrow depressions or
"pits." This thick-walled tissue is called "stony tissue"
(schlerenchyma). All the cells contain numerous granules, which the
iodine test shows to be starch. All of this second region lying
between the epidermis and the fibro-vascular bundle is known as the
ground tissue. The third region (fibro-vascular) is, as we have seen
without the microscope, circular or horse-shoe shaped. It is sharply
separated from the ground tissue by a row of small cells, called the
"bundle sheath." The cross-section of the bundle of the leaf stalk
resembles, almost exactly, that of the stem; and, as it is much
easier to cut, it is to be preferred in studying the arrangement of
the tissues of the bundle (Fig. 67, _G_). Within the bundle sheath
(_sh._) there are two well-marked regions, a central