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The section of the stem shows a small central cavity, an
exterior surface of rather prominent ridges, each channelled
so as to form two projecting angles, and a circle of moderatesized
cavities occurring about the centre of the tissues.
Insensibly merging into the form just described appears
to be another, that sometimes called E. arenarium, which,
in its extreme state, is smaller and more slender, its stems
always procumbent, and not having more than six furrows ;
in this form the teeth of the sheaths are said to be wedge-
shaped, but we do not detect any differences in respect to the
teeth between specimens having the erect and the prostrate
habit of growth.
Another form, which is perhaps at least a permanent
variety, and may prove to be specifically distinct, is the
plant called E. Wilsoni by Mr. Newman. With this we
are entirely unacquainted, except through books, in which
it is described as being stouter, taller—three feet high— and
smoother than the larger form of E. variegatum. The section
of its stem also differs materially; the central cavity
and the ring of cavities occurring in the cylinder of the stem
being much larger, and the latter differing in form from
those of E. variegatum. This variety grows in water, at
Mucruss, in the immediate vicinity of the Lakes of Killarney.
The steins are generally simple, but sometimes
sparingly branched; they have about ten furrow’s, with
broad intermediate ridges,, on which the siliceous particles
are far less prominent, so that the stems are not nearly so
rough as in the allied E. variegatum, Machayi, &c. The
sheaths are scarcely larger than the stem, and are entirely
green, except a narrow, black, sinuous ring at the margin ;
the teeth are short, generally blnnt, and have obscure membranous
margins. No mention is made of the deciduous
bristle which occurs in the allied plants. The cone is
small, black, terminal, and apiculate, and, as occurs in the
allied kinds, its sheath is larger and looser than the rest,
the teeth also longer, and their membranous edges dilated
and conspicuous. Such is the substance of Mr. Newman’s
account of it in his ' History of British Eerns.’
The present species is rather a local plant, but is widely
dispersed in the three kingdoms, the larger forms growing
on the margins of lakes, canals, rivers, ditches, &c., the
smaller prostrate examples occurring on the sandy sea-coasts.
The Equisetums appear to submit readily to cultivation;
at least we have found no difficnlty in inducing those of
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