POLYPODIUM, in botany; a genus of the order of filices, belonging to the cryptogamia class of plants. The fructifications are in roundish points, scattered over the inferior disc of the frons or leaf. There are 65 species, of which the most remarkable is the filix mas, or common male fern. This grows in great plenty throughout Britain in woods and stony uncultivated soils. The greatest part of the root lies horizontally, and has a great number of appendages placed close to each other in a vertical direction, while a number of small fibres strike downwards. The leaves are a cubit high, and grow in circular tufts. They are at first alternately pinnate, the pinnæ increasing in size from the base towards the middle, and afterwards gradually decreasing upwards to the summit of the leaf. These pinnæ are again pinnatifid, or subdivided almost to the nerve into obtuse parallel lobes, crenated on the edges. The stalks are covered with brown filmy scales. The fructifications are kidney-shaped, and covered with a permanent scaly shield or involucre. The capsules are of a pale brown, surrounded with a saffron-coloured elastic ring.
This fern has nearly the same qualities, and is used for most of the same intentions, as the pteris aquilina. They are both burnt together for the sake of their ashes, which are purchased by the soap and glass-makers. In the island of Jura are exported annually 150 L. worth of these ashes.
Gunner relates, in his Flor. Norveg. that the young curled leaves, at their first appearance out of the ground, are by some boiled and eaten like asparagus; and that the poorer Norwegians cut off those succulent laminae, like the nails of the finger at the crown of the root, which are the bases of the future stalks, and brew them into beer, adding thereto a third portion of malt, and in times of great scarcity mix the same in their bread. The same author adds, that this fern cut green, and dried in the open air, affords not only an excellent litter for cattle, but, if infused in hot water, becomes no contemptible fodder to goats, sheep, and other cattle, which will readily eat and sometimes grow fat upon it: a circumstance well worth the attention of the inhabitants of the Highlands and Hebrides, as great numbers of their cattle, in hard winters, frequently perish for want of food.
But the anthelmintic quality of the root of the male fern is that for which it is chiefly to be valued, and of
which an account is given under the article MEDICINE, p. 343. col. 2.
The polypodium oreopteris is only remarkable because it has been confounded by most of the English botanists with the species which we have now described, and the polypodium thelypteris. It has a large scaly root, wrapped and tied together with small strong fibres, not to be separated without difficulty. The fructifications are on the margins both when young and old, and never run into one another: the lobes are oval and plain. It is four times as large as the thelypteris, and grows in dry woods, moors, or hills, and very seldom near water; all which characters are widely different from those of the species with which it has been confounded. It is to be found both in England and Scotland, in the latter place very plentifully. See Linnean Transactions, vol. 1. p. 181.