found on Snowdon, and is well known by the guides of that district as growing there.

This little fern is said to do well in a fernery, in a sheltered part. It must not be kept very wet. Neither this fern nor its variety seems to bear confinement in closed cases or frames, as they require a free circulation of air, without which they become feeble and die.

VARIETY.

WOODSIA ILVENSIS HYPERBOREA (fig. 20), or Alpine Fern, called by Newman Woodsia alpina, although considered as a distinct species by some writers, does not differ so materially from Woodsia ilvensis as to constitute more than a variety. It is known by its narrower fronds, being of a thinner texture, less hairy and scaly; while the pinnæ are less opposite, and shorter, and more triangular in their general outline.

It is a very rare species, found in the fissures of Alpine rocks, mostly in places little visited.

ON THE

STRUCTURE AND FUNCTIONS OF FERNS.

THE Vegetable Kingdom is divided into two great groups of plants-those with flowers and those without,-technically, Phanerogamia and Cryptogamia. The ferns belong to the latter group. They are easily distinguished from the mosses, horsetails, fungi, lichens, and algæ, with which they are associated, by their large size and leafy character. The part of the fern which, from its green colour and general form, resembles a leaf, is called a frond. Although ferns have no proper flowers, they have organs which perform the functions of flowers in higher plants. These organs are seldom seated on a separate stem or stalk, but are placed on the edges and under-side of the fronds.

Ferns, like other plants, have roots and stems. The roots of ferns are composed of small fibres, which are sent down from the stem, and they perform the same functions in ferns as in other plants. They serve to keep the plant in the soil in which it grows, and are also endowed with the property of absorbing from the soil the food which the plant requires for its nutrition.

The stem of a fern consists of a mass of tissue, from which the stalks of the fronds proceed upward, and the root downward. In British ferns, these stems seldom rise up into the air, but are either buried in the earth, or lie prostrate upon it: in the common

polypody and the spleenwort they attain a considerable size. When out of the ground, they are covered with scales and hairs, and present a very shaggy appearance. In some cases, as in the common brakes and the Flowery Fern, the stem rises erect in the air, and bears its fronds in the same way as higher plants bear their leaves. It is in tropical ferns that these stems attain their greatest size, and rise above the ground forty or fifty feet in height. Such ferns are called tree-ferns. But the nature of this stem is the same in all cases: it consists of a mixture of woody and cellular tissue, constituting the basis of the fronds; and in cases where the stem is perennial, it consists of the remains of the successive annual developments of the fronds.

The fronds vary much in form, and the stalk on which they are placed is called the stipes. They vary in size, and also in duration: they usually, however, come up in the spring, and die down in the

autumn.

The frond, like the leaf, is divided into the blade and stalk, or stipes. The woody tissue of which the stipes is formed is continued into the blade, and constitutes there the veins or ribs. The middle portion, which runs up the whole frond, is called the midrib.

The same terms are applied to the shape of the frond as to the leaf. When the blade is undivided, as in the Hart's-tongue, it is called entire; when the frond is scalloped out, and the indentations do not reach the midrib, the frond is said to be pinnatifid; when the indentations reach the midrib, and leave a series of little leaflets, or pinne, the frond is said to be pinnated. The pinne may be again divided down to their veins or ribs, and the frond is then said to be twice-cut, or bi-pinnate. When this occurs a third time, it is tri-pinnate; and when oftener, the frond is said to be decompound. This latter does not, however,

often occur in British species. The more vigorous specimens of the Common Brakes occasionally present it.

When the fronds are first formed in the bud, they are rolled up in a peculiar way. The whole frond is rolled up from the point to the base, upon itself; and when it is divided into pinnæ, each pinna is rolled in the same way upon itself. This arrangement occurs in other plants, and is called circinate. All British ferns, with the exception of the Adder's-tongue and Moonwort, have this circinate arrangement of their fronds.

The veins or ribs of the fronds are variously arranged, forming sometimes good characters for the distinction of species. These veins are never netted, as they are in the majority of flowering plants, but they are often forked, or dichotomous. It is upon the veins of the under-part of the frond that the organs of fructification are placed; and this part is called the receptacle.

The organs of fructification consist of a number of little capsules, called seed-cases, spore-cases, sporangia, or thecæ. These are collected together in little clusters, which are called sori. The sori are placed upon the receptacle. When the sori are placed on the under-part of the frond, they are called dorsal; but when on the edge of the frond, marginal. They are never placed on the upper surface of the frond alone. Sometimes the whole frond is converted into a receptacle, as in the case of the Flowering Fern, the Adder's-tongue, and some others.

The spore-cases are mostly small, slightly ovate bodies, with a single cavity. They are surrounded with a ring, one end of which is fixed to the receptacle. When the spores contained in the inside have reached maturity, the elasticity of the ring causes the spore-case to burst transversely, and the spores are