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been met with only in a limited number of localities in
Ireland, Scotland, and the north of England.
E q u ise tum va r ieg a t um , Weier and Mohr.— The Variegated
Eough Horsetail.
This species is found on the banks of rivers and lakes, and
in sandy places near the sea. There is considerable variation
among the plants classed under this name, and met with in
these different localities, the differences appearing to be
permanent under cultivation, but we have not yet sufficient
evidence to treat them as distinct species. We, therefore,
include as varieties or forms of variegatum, the dwarf procumbent
plant sometimes called E. arenarium, and the tall
stout erect form which has been named E. Wilsoni.
This is one of the species whose stems are all similar, and
almost quite unbranched. It extends by means of a widely
creeping underground stem, rooting in whorls like the other
species, and producing numerous above-ground stems, often
springing from joints in such close proximity, that they
appear in dense tufts. Though so numerously branched
just beneath or at the surface of the soil, it is not usual that
any branches are produced on the exposed part of the stems,
but this sometimes does occur, such branches not growing
in whorls, but springing singly from the joints, and having
much similarity to the stem itself; it is the erect form of
the species, chiefly, which thus becomes branched. The
stems grow about a foot high, and, in what is taken as the
typical plant, their surface is very rough, and impressed
with from four to ten furrows, with alternating, rather prominent
ridges, each ridge margined on both sides, with a
line of minute siliceous points, which give it the appearance
of being grooved, and impart the peculiar roughness to the
stems. The sheaths are slightly enlarged towards their
margin, ribbed like the stem, green in the lower part, black
above, and terminating in a fringe of black teeth, equalling
the ribs in number; in form ovate, with a broad white
membranous border, and tipped by a deciduous bristle.
Sometimes the contrast between the black ring and teeth,
and the white border to the latter, is very conspicuous.
A certain number of the stems, usually the most vigorous,
terminate in a cone of fructification. This is small, elliptic,
crowned by a prominent point or apiculus. It is usually
black, and sessile in the uppermost sheath, but sometimes
elevated on a short stalk. All the stalked cones we have
seen have been much paler in colour than the sessile ones.
The scales are about twenty in number, and the spore-cases
are whitish.
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