THE POLYPODIES
There must be very few people, indeed, who are not familiar with the
leading British representatives of the sub-family _Polypodieæ_. It is
difficult, indeed, to make a journey in any part of the country without
sooner or later coming across some plants of the Common Polypody. Some
other species of the genus _Polypodium_ are not uncommon in certain parts
of the country.
_Polypodium vulgare._ Here the generic name is derived from two Greek
words—_polys_, “many,” and _pous_, “a foot.” This has been given to the
plant on account of the fact that the creeping and branching rhizomes
from which the fronds arise are in some way suggestive of feet. The
specific name, of course, means “common.” The Common Polypody.
This species has a creeping root-stock which in its young days is covered
with brown scales. From the underside there grow masses of fibrous roots,
which often spread for a considerable distance. The rhizome may be very
much branched, and from it alternately on either side arise the fronds.
These may be quite short—about five or six inches—or, on the other hand,
they may be as much as one or two feet in length. The stipes is usually
about the same length as the leafy portion of the frond and is of a plain
green colour. The general outline of the leafy part of the frond is
lanceolate, tapering to a point, broad in the centre and narrowing
slightly at the base. The frond of the Common Polypody is cut in a
pinnatifid manner. The lobes, which are more or less rounded at the tip,
are separated by openings in which the leafy portion is cut almost down
to the rachis. Now and again the margin of the lobes is somewhat toothed.
[Illustration: Polypodium vulgare. The Common Polypody.]
On the back of the frond are to be found the sori. These are disposed on
both sides of the mid-ribs of the lobes; they are circular in shape and
have no indusia or covering of any kind. When the sporangia are young the
sori are of a very pale yellow colour; this changes to a rich
golden-brown as the capsules mature. The sori are mostly confined to the
upper portion of the frond, and on account of their bright colouring add
very much to the appearance of the leaf. There are a large number of
varieties of the Common Polypody.
[Illustration: Enlargement of the sori on the frond of Common Polypody.]
The Common Polypody will, of course, grow in almost any position. It
often finds a home amongst the branches of old oak trees, whilst it seems
to be equally happy on the wall or the hedge-bank. It is of fairly easy
culture in the garden, though the plant likes a well-drained situation.
The Common Polypody is an evergreen species.
[Illustration: Polypodium phegopteris. The Beech Fern.]
_Polypodium phegopteris._ Here the specific name is formed of two Greek
words—_phegos_, “a beech,” and _pteris_, “a fern.” This is, of course, a
rendering of the popular name, though why the species has been called the
Beech Fern nobody seems to know. Certainly the species is not like a
Beech, neither can it be said to grow in association with this tree. The
Beech Fern or Mountain Polypody.
This species has a slender creeping rhizome from which arise the dainty
light green fronds. The fronds vary from about six inches to a foot in
length; the stipes is longer than the leafy portion, and is of a light
green colour. The outline of the leafy part is triangular in form, and on
either side of the rachis are the tapering pinnæ. At the top the frond is
pinnatifid, whilst the lower pinnæ are deeply cut. A very distinctive
feature of the Beech Fern is the way in which the lower pair of pinnæ
point downwards away from the tip of the frond.
Nearly the whole of the underside of the frond bears the sori. These are
placed quite near to the margins of the lobes of the pinnæ. Like all the
Polypodies the clusters of sporangia have no indusia.
The Beech Fern cannot be called a common species, though it is often
abundant in certain localities. It is much more frequent in Scotland than
elsewhere, and may be looked for hopefully in almost any moist wood. It
also occurs abundantly in some parts of the North of England. Unless the
Beech Fern can be given a moist position it is not an easy plant to grow
in the open garden. It is, however, successfully cultivated in the
greenhouse. The plant dies down in the winter, and the new fronds do not
appear until somewhat late in the spring.
_Polypodium dryopteris._ Here the specific name is derived from two Greek
words—_drus_, “an oak,” and _pteris_, “a fern.” Here again it is not easy
to see a resemblance between this fern and an oak, unless it be that the
newly-developing fronds are in colour something like the delicate green
of the tree when it is decked in its new foliage. The Oak Fern or
Three-branched Polypody.
This plant has a thin creeping rhizome from which the fronds arise. The
stipes is of a pale green colour, and it is usually longer than the leafy
portion. Actually the frond is divided into three branches, each of which
is triangular in shape and pinnate towards the base, becoming pinnatifid
at the tip. The pinnæ are deeply segmented. The unrolling of the frond is
a very novel feature of this Fern, each branch at this time appearing to
be like a small coil of wire. In its early days the golden green colour
of the frond is very much pronounced, but as the leaf ages a deeper tone
is assumed.
The sori are disposed near to the margins of the lobes of the leaves, and
these are circular and without indusia. The lower pinnæ of the Oak Fern
do not point downwards, as is seen in the case of the Beech Fern.
The Oak Fern is common in many parts of Scotland, and is to be seen
carpeting the ground of many a moist wood. It also occurs in England
chiefly in the northern counties. In some parts of Wales it is to be
found in plenty, but the species is said to be rare in Ireland. The Oak
Fern grows in a damp and shady spot in the garden, though it is often
more happy in a pot. The fronds of the plant die down in winter, and the
fresh ones do not start until late in the spring.
In some books a species called _Polypodium calcareum_ (The Limestone
Polypody) is described. In some quarters this plant is regarded as a
variety of _P. dryopteris_, as it is similar in some respects. Mr. C. T.
Druery considers it to be a distinct species. The chief points of
difference are said to be the following. The whole plant is larger in
growth, whilst the green of the fronds is not such a golden colour, even
in the early days. Also the pinnæ are not arranged so definitely in the
form of three branches, as is to be observed in the case of the Oak Fern.
Finally, the unrolling of the frond does not present the appearance of
three little balls, seeing that each pinnæ unfolds separately. The
Limestone Polypody occurs chiefly in the North of England.
_Polypodium alpestre._ The Alpine Polypody. This is a most remarkable
species, in that it bears a singular resemblance to the Lady Fern. By
some authorities it is positively regarded as a Mountain form of the Lady
Fern. The reason for linking the species with the Polypodies is found in
the rounded sori, which have no indusia. The Alpine Polypody has a short
tufted root-stock, and from this arise the fronds, which may be a foot or
even more in height. The stipes is very short when compared with the
leafy portion, and it is covered with brown scales. The general outline
of the fronds is broadly lanceolate, and they are twice divided. The
pinnæ are arranged in alternation on either side of the rachis, and these
are divided into pinnules with blunt points. The pinnules have toothed
edges. The sori are chiefly situated near to the inside border of the
pinnules. Those who consider that the Alpine Polypody is a form of the
Lady Fern call the species _Pseudathyrium alpestre_.
The Alpine Polypody seems to be exclusively confined, as far as the
United Kingdom is concerned, to the highlands of Scotland. It is
sometimes to be found at an altitude of four thousand feet above
sea-level. In spite of its restricted locality the Alpine Polypody is an
easy subject for the garden, if it can be provided with a well-drained
situation.