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Family Betulaceae
Alnus glutinosa
Although the Alder is abundant by river-sides
and in all low-lying moist lands as far north
as Caithness, it is not so generally well known
at sight as the Oak, the Beech, and the Birch.
It is a small tree, ordinarily only thirty to
forty feet in height, with a girth from three
to six feet, though occasionally it reaches a
hundred feet in height. This is when it is growing
in moist loam, upon which rain or floods have
washed down good layers of humus from woods at
a higher elevation. If, with its roots thus cared
for, its head is in a humid atmosphere, the Alder
is in happy case. If it has had the misfortune
to get into a porous soil, though this may be
moist enough to please the Ash, the Alder merely
becomes a big bush.
The bark of the Alder is rough and black, and
the leaves, from two to four inches long, are
roundish with a wedged-shaped base. They have
a waved and toothed margin, and have short stalks.
They remain green long after the leaves of other
trees have fallen. In their young condition these
leaves are covered with hairs, and are sticky
to the touch, and when older they retain a distinct
suggestion of greasiness. There are bacteria nodules
on the roots.
The flowering of the Alder is similar to that
of the Birch, but the male catkins have red scales,
and each flower four stamens. These catkins are
erect at first, afterwards becoming lax and drooping.
The female spikes remain erect and have the fleshy
scales covered by red-brown bracts.
Seed is not produced until the Alder is twenty
years old, and the crop is repeated almost every
year after. The cones are ripe about October and
November, when they scatter their fruit, but the
empty ones persist in hanging to the branches
throughout the winter in numbers sufficient to
give the leafless tree a brown appearance from
a little distance. The immature male catkins are
in evidence at the same time.
The wood of the Alder is soft. Whilst the tree
is sliver its wood is white, but when cut and
exposed to the air it becomes red; finally, on
drying, it changes to a pinkish tint.
As timber it has not great reputation, except
for piles or other submerged purposes, when it
is said to be exceedingly durable. It has also
enjoyed a great reputation for making the best
charcoal for the gunpowder mills, and it is largely
used by the wood-turner, the wood-carver, and
the cabinet-maker.
There is a variety (incisa) of the Alder in which
the leaves are so deeply toothed that they bear
a close resemblance to those of the Hawthorn.
In some localities the tree is called the Howler
and Aller; the latter word apparently is from
the original Anglo-Saxon name.
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