[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.