The Ferns (Filices) are a natural order of cryptogamous or flowerless plants, forming the highest group of the acrogena or summit-growers. They are leafy plants, the leaves, or more properly fronds, arising from a rhizome or root-stock, or from a hollow arborescent trunk, and being circinate in vernation, a term descriptive of the manner in which the fronds are rolled up before they are developed in spring, having then the appearance of a bishop's crosier. On the veins of their lower surface, or their margins, the fronds bear small vessels named sporangia, containing spores. These spore-cases are arrangod in clusters, named sori, which are either naked or covered with a layer of the epidermis, which forms an involucre or indusium. When the spores germinate they produce a cellular structure of a leafy description, called the pro-embryo, or prothallus, upon which are developed organs which have received the names of antheridia and archegonia. When produced upon the prothallus these organs do not immediately give origin to a germinating spore, but from their mutual action proceeds a distinct cellular body, destined at a later period to develop into a fruit-bearing frond.
Ferns have a wide geographical range, but are most abundant in humid, temperate, and tropical regions. In the tropical forests the tree-ferns rival the palms, rising sometimes to a height of 15 or 18 metres. Ferns are very abundant as fossil plants. The earliest-known forms occur in Devonian rocks. Various systems of classification for ferns have been proposed over time. The order is usually divided into six or eight suborders or tribes distinguished by differences in the structure of the sporangium. The generic characters are founded on the position and direction of the sori and on the venation. The largest division is that of the Polypodiaceae, to which nearly all British ferns belong, such as the polypody, the lady-fern, the bracken, the hard-fern, the spleenwort, the maiden-hair, the hart's-tonguefern, etc. The royal fern, however, belongs to the Osmundaceae. A few of the ferns are used medicinally, mostly as demulcents and astringents. Some yield food. Pteris esculenta is the edible bracken of New Zealand. Research Ferns
Polypody (Polypodium vulgare) is a perennialfern of the family Polypodiaceae, common to Britain and Europe. It has a creeping, slightly flattened, branched rhizome, which bears numerous red-brown scales. Every year new fronds rise alongside the old ones. The fronds are simple, long- stalked, smooth and pinnately divided with lanceolate segments, rounded at the tip. Clusters of spore cases are arranged in two rows on the undersides of the upper segments, coloured orange at first and then later brown. Research Polypody
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Matt and Leela Probert
Abbreviations
Research Ferns
