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cylinder of the stem occur two circles of cavities, the outer
one consisting of large openings, those of the inner minute,
and alternating with the larger. The central cavity is very
large, the tissue of the stem being reduced to a very narrow
ring.
This is a widely-dispersed and rather common plant, occurring
on moist banks and in muddy places, by the sides
of streams and the margins of muddy pools. The nature of
the soil would seem to be of small importance provided it
has its necessary degree of moisture, for it is recorded as
occurring both in sandy and in clayey soils, as well as in
muddy pools. It is frequent in Ireland; and is found both
in Scotland and AYales.
E q u ise tum um buo sum , Willdenow.—The Shady Horsetail.
This species of Horsetail was formerly named E. Brum-
mondii by Sir W. J. Hooker, after Mr. T. Drummond, who
first discovered it as a native of Britain, but it proves to be
the same which Willdenow had previously called E. wm-
broswm. It is a very interesting and distinct plant, intermediate
in its general characteristics between E. arvense and
E. sylvaticum, hut perfectly distinct from both.
Erom its long, dark-coloured, creeping, underground stem
are produced, at the joints, whorls of slender fibrous roots.
and from buds organized at the same points arise the aerial
stems. These are quite dissimilar in their appearance, some
being short, quite simple, and terminating in a cone-like
head of spore-cases; others being without fructification,
taller, and producing several whorls of long, crowded, slender
branches; whilst a third kind, of ' common though not
constant occurrence,’ produce whorls of branches and cones
also. In the production of these three kinds of stems it
serves to connect, through E. sylvaticum, that group in
which the fertile and barren stems are successive and altogether
unlike, with that in which any of the stems indifferently—
at least as to external appearances—bear the fructification,
all being of similar habit.
The fertile stems grow about six inches high, and are
quite branchless; they are of a pale yellowish-green, having
numerous joints, the large loose funnel-shaped sheaths produced
at these points, almost covering the stem, as usually
described and figured, but in our specimens they are much
less crowded, a space of from haK an inch to an inch occurring
between the adjoining sheaths. These sheaths are
still paler-coloured than the stem, often almost white, with a
dark ring below the teeth, which are awl-shaped, pale browu,
with pale-coloured membranous margins; the teeth are
*
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