48
about twenty—from twelve to twenty—in number, equalling
tlie ribs on the sheath. These fertile stems are very slightly
striated.
The barren stems grow erect to the height of eighteen
inches or more, and have their surface disposed in about
twenty sharp ridges, with corresponding furrows, the ridges
being coated with prominent siliceous warty particles, so
that the stems become very rough. The few lower joints
are without branches, but in all the upper part of the stem
they produce whorls of from ten to sixteen branches, which
are simple, and at first drooping, but eventually take a spreading
or slightly ascending direction. The sheaths of these
barren stems are much smaller than those of the fertile, less
funnel-shaped, and more closely set to the stem, and their
teeth are also fewer, shorter, and blunter; but in respect of
colour they do not materially differ. The branches, which are
slender, and about four inches long, are three- or four-ribbed,
and have loose sheaths, which terminate in three or four short,
acute, membranous-edged, faintly brown-tipped teeth; the
ribs of the stem extend upwards into the teeth, one entering
each, but they do not quite reach the apex.
The fructification forms a moderate-sized, terminal, oval,
cone-hke head; at first sessile in the uppermost sheath, but
becoming elevated on a short stalk. The scales are from
forty to fifty in number, and are of a pale brown colour,
bearing numerous whitish spore-cases.
The branched fertile stems have their sheaths smaller
than the simple fertile ones, but larger than the barren ones.
Several of the uppermost joints produce whorls of branches,
and the stem is terminated by a cone of fructification. In
these cases, however, the number of branches is less than
that produced by the ordinary barren stems, and the cone is
smaller than those produced by the ordinary fertile stems.
In fact, the parts seem intermediate.
The section of the stem of this species is very different
from that of any other, though having most resemblance to
those of E. arvense and E. sylvaticum. The exterior shows
a series of sharp ridges with angular furrows; the central
cavity rather exceeds a third of the whole diameter; the
cylinder of the stem is then pierced by three circles of cavities—
one of longish oblong openings opposite the furrows,
one of minute pores exterior to these and opposite the ridges,
and another of minute pores on their inner side also opposite
the ridges.
Probably this species is tolerably plentiful in moist shady
woods, which are the situations it affects, but it has as yet
H
in