fern any plant of the division Polypodiophyta. Fern species, numbering several thousand, are found throughout the world but are especially abundant in tropical rain forests. The ferns and their relatives (e.g., the club moss and horsetail ) are the most primitive plants to have developed a true vascular system (see plant ). The asparagus fern and shrub sweet fern (see bayberry ) of florists are not true ferns.

Common Species

The majority of the common living ferns are members of the polypody family (Polypodiaceae), usually characterized by the familiar triangular fronds subdivided into many leaflets (pinnae) and smaller pinnules. A popular house fern, a drooping-leaved variety of Nephrolepis exaltata, a tropical sword fern, is called the Boston fern (var. bostoniensis ) because it was first found in a shipment of sword ferns received in Boston. The maidenhair ferns ( Adiantum ), with a few species native to North America, were formerly used as a cure for respiratory ailments. The Brazilian A. cuneatum and its numerous varieties are now the major greenhouse ferns in North America. The most familiar of all woodland ferns, found the world over, is Pteridium aquilinum, the common bracken , or brake (names also applied to other similar ferns, especially species of Pteris ). Other North American woodland ferns include the Christmas fern ( Polystichum acrostichoides ), a dark-green evergreen plant; the walking fern ( Camptosorus rhizophyllus ), native to limestone areas and named for its characteristic vegetative reproduction, in which new plantlets root from the tips of the elongated fronds; and the common polypody ( Polypodium vulgare ), called also wall, or boulder, fern, a low, matted plant that is the most common of the rock-inhabiting ferns. Also included in the polypody family are many of the mostly tropical fern epiphytes . Some ferns of other families are aquatic. Among the better known aquatic genera are Marsilea and Salvinia, cultivated in aquariums; giant salvinia, S. molesta, native to South America, and common salvinia, S. minima, native to Central and South America, are prolific aquatic weeds in some S U.S. lakes. The adder's-tongue ferns ( Ophioglossum ) and rattlesnake ferns ( Botrychium ) belong to the most primitive fern family ( Ophioglossaceae ) and bear sporangia not in sori but in spikes arising from the leaves. Dicksonia, Cibotium, and Cyathea are the tree fern genera most frequently seen in greenhouses and conservatories.

Ancient Ferns

During the Carboniferous era, ancestors to modern ferns were the dominant vegetation of the earth; they contributed to the coal deposits then being formed. Ancient ferns were probably similar to the tree ferns, a declining race found today only in a few tropical areas. Their fronds are clustered at the top of a treelike trunk, sometimes 30 or 40 ft (9-12 m) in height, rather than growing directly from the rootstalk as do those of most temperate ferns.

Reproduction

Ferns reproduce by an alternation of generations (see reproduction ), the fern itself being the sporophyte, which produces asexual spores. In most ferns the sporangia ( spore -bearing sacs) are borne in clusters (called sori), which appear as brown dots or streaks on the underside of the leaves. Although no present-day ferns reproduce by seeds, there are fossils of some fernlike plants that were seed-producing, and it is believed that the seed plants (e.g., the gymnosperms and true flowering plants) evolved from fernlike ancestors.

Uses and Lore

The tree ferns (families Dicksoniaceae and Cyatheaceae) are the only living ferns of any commercial importance other than as ornamentals. In the tropics the trunks are employed in construction, and the starchy pith was formerly eaten by the Maoris and other native groups. The dense root systems are widely used as a substrate for growing orchids; many populations of tree ferns are destroyed for this purpose. Dense golden hair covers the base of the leaf stalks and buds in many species and is exported as "pulu" for mattress and pillow stuffing and for packing material. A large number of fern species are used medicinally by local populations, especially in the tropics.

Numerous superstitions have arisen about ferns. The mythical "fern seeds," believed to be produced by the male fern ( Dryopteris filix-mas ) and by the lady fern (formerly a name for the common bracken but now applied to Athyrium filix-femina ), were reputed to create invisibility if eaten by a member of the appropriate sex. The bracken was also considered protection against goblins and witches because the broken stem and root appear to be marked with a C, symbolizing Christ.

Classification

Ferns are classified in the division Polypodiophyta , class Polypodiopsida.

Bibliography

See G. M. Smith, Cryptogamic Botany, Vol. II (2d ed. 1955); B. Cobb, A Field Guide to the Ferns (1956); F. S. Shuttleworth and H. S. Zim, Non-flowering Plants (1967); F. E. Round, Introduction to the Lower Plants (1969); D. L. Jones Encyclopedia of Ferns (1987).

Ferns

Ferns, like the more familiar seed plants, have stems, roots, and large, highly veined leaves. Ferns do not reproduce by seeds, however, and have several other distinctive features. The leaf of a fern is called a frond and, in many species, the green blade is divided into segments called pinnae. The leaves of most ferns have a distinctive juvenile stage called a fiddlehead, where all the segments are curled in a manner resembling the end of a violin's neck. Most ferns have underground stems called rhizomes and the only parts of the fern plant visible above ground are the leaves. Some tropical ferns, called tree ferns, have erect, unbranched stems up to 20 meters tall with all of the fronds arising from the tip. Ferns are perennial plants and some may grow for many years, but, as they lack annual growth rings, their age is not easily determined. However, in 1993, researchers using molecular genetic markers found some individual bracken fern (Pteridium aquilinum ) plants more than 1 kilometer across. Researchers estimated that these ferns took more than 1,180 years to grow to this size, possibly putting them among the oldest living plants on Earth.

Ferns and seed plants are similar in having two kinds of plants present in their reproductive life cycle, but overall ferns reproduce very differently than seed plants. The familiar fern plant, described in the preceding paragraph, is the sporophyte (spore-bearing phase). Fern fronds bear organs known as sporangia. Inside each sporangium certain cells undergo reduction division, or meiosis, which yields haploid spores that have one set of genes for the fern. All of the cells in the sporophyte fern plant itself are diploid, having two sets of genes. The sporangia of most ferns are very small, scalelike, and contain only sixty-four spores, but some ferns have large sporangia containing hundreds of spores. A typical fern sporophyte plant may produce up to one billion spores per year. When the sporangia open, the spores are shed into the air and dispersed. While most fern spores land within one hundred meters of the fern producing them, some may be spread very far. Fern spores have been recovered from the upper atmosphere in samples collected by airplanes and weather balloons.

When the single-celled fern spore lands on a suitable substrate , it may undergo mitotic cell division and develop into a very different kind of plant. The plant that grows from a fern spore, called the prothallus, is barely visible to the naked eye. It resembles a tiny, heart-shaped ribbon and lacks any stems, roots, leaves, or internal food- or water-conducting tissues. Reproductively, this small, independent fern plant is critical because it bears the sex organs. Although the basics of sexual reproduction in ferns were discovered in the nineteenth century, many crucial details are still being clarified. A single fern gametophyte may produce both sperm-bearing sex organs, called antheridia, and egg-bearing sex organs, known as archegonia, but frequently an individual gametophyte has only one type of sex organ. Fertilization occurs when a sperm swims to unite with an egg to form a diploid zygote, which then develops into the sporophyte.

Whether the individual gametophyte plants in a population are bisexual or unisexual is very important because it is basic to determining the degree of genetic variation possible in the sporophyte generation produced. A single bisexual gametophyte can fertilize its own eggs and produce a new sporophyte plant, but such a sporophyte would be highly inbred because both the sperm and egg producing it would be genetically identical. Most ferns control the sexual expression of the individual plants in a gametophyte population so that each plant is either male or female. Thus, fertilization usually requires two gametophytes that are close enough for sperm to swim in water between them. Receptive archegonia secrete a sperm attractant to help the sperm find its way. When genetic material from two different gametophytes is mixed in the zygote, the sporophyte that develops has more genetic variation than one arising from a single gametophyte. If the entire fern sporophyte population is reproduced this way, it may be more likely to survive because some of its members may have inherited the traits needed to endure unforeseen changes in its environment. On the other hand, a distinct survival advantage arises when a single fern spore, dispersed a long distance, can produce a sporophyte from one gametophyte, because this permits rapid colonization of distant, favorable habitats.

Although factors regulating fern spore germination and development are fairly well known from laboratory studies, relatively little is known about how ferns actually reproduce in their environments. Most fern spores germinate readily on moist soil. Germination often requires red light that is absorbed by a pigment in the spore. Calcium ions are important to germination, and red and blue light control the pattern of gametophyte development. Fern spores are known to persist in the soil, forming spore banks. These factors and many more interact in complex ways in the field. Ecologically, most fern species are found in habitats where moisture is readily available, permitting gametophytes to grow and sperm to swim to eggs in water. Those concerned with preserving a rare fern species at a site must understand that if the locality does not provide safe sites for the independent gametophytes, with their distinct ecological requirements, the species cannot reproduce and the sporophytes will eventually die off.

Moist, tropical mountain forest communities contain the largest number of fern species. Of the approximately 12,000 fern species worldwide, about 75 percent are tropical. The flora of North America, north of Mexico, contains about 350 fern species, whereas southern Mexico and Central America have about 900. A few ferns are occasionally eaten. However, some, like bracken fern, contain poisons or carcinogens. Ferns are present in most plant communities but dominant in few.

see also Epiphytes; Seedless Vascular Plants.

James C. Parks

Bibliography

Burnie, David. How Nature Works. Pleasantville, NY: Reader's Digest, 1991.

Jones, David. Encyclopaedia of Ferns. Melbourne: Lothian Publishing Co., Ltd., 1987.

Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants, 6th ed. New York: W. H. Freeman and Company, 1999.

Tryon, Rolla, and Alice Tryon. Ferns and Allied Plants. New York: Springer-Verlag,1982.

Fern

Many occult beliefs have adhered to the common fern. In ancient times the fern was thought not to have seed. Later on, people thought that the seed was invisible, and if a man could find this invisible seed, it would confer the power of invisibility upon him. The fern was also believed to flower at midnight on St. John's Eve, one of the more magical days of the year in medieval Europe. Legend said that anyone who gained possession of the flower would be protected from all evil influences and would obtain a revelation of hidden treasure.

fern Non-flowering plant. Ferns grow mainly in warm, moist areas; there are c.10,000 species. The best-known genus Pteridium (bracken) grows on moorland and in open woodland. Ferns are characterized by two generations: the conspicuous sporophyte, which possesses leafy fronds, stems, rhizomes and roots, and reproduces by minute spores usually clustered on the leaves; and the inconspicuous gametophyte, which resembles moss and produces sperm and ova. Phylum Filicinophyta. See also alternation of generations

Fern ♀ From the vocabulary word denoting the plant (Old English fearn). Modern use of this word as a given name dates from the 19th century, when it is also recorded occasionally as a boy's name in the United States. In some instances the given name may be a transferred use of the surname derived in the medieval period from the vocabulary word.

fern OE. fearn = MDu. væren (Du. varen), OHG. (G.) farn :- WGmc. *farna :- IE. *porno-, whence Skr. parṇá- wing, feather, leaf; rel. further to Lith. papártis, Russ. páporotnik, (O)Ir. raith (:- *pratis). The prim. meaning is doubtless ‘feathery leaf’; cf. also Gr. pterón feather, pteris fern.

fern / fərn/ • n. (pl. same or ferns ) a flowerless plant (class Filicopsida, division Pteridophyta) that has feathery or leafy fronds and reproduces by spores released from the undersides of the fronds. DERIVATIVES: fern·y adj.

Fern Ang. ‘(Place of) alders’. Gaelic fearn.

Ferns (Fearna) Wexford. ‘Place of alders’.

Fern

a huge quantity or number, 1300.

ferns See Filicinophyta.

ferns See PTEROPSIDA.

fern See FILICOPSIDA.

fern •adjourn, astern, Berne, burn, churn, concern, discern, earn, fern, fohn, kern, learn, Lucerne, quern, Sauternes, spurn, stern, Sterne, tern, terne, Traherne, turn, urn, Verne, yearn •Bayern • Blackburn • heartburn •Hepburn • Raeburn • Swinburne •Gisborne, Lisburn •sideburn • sunburn • Bannockburn •lady-fern • Vättern • extern •cittern, gittern •Comintern • taciturn •nocturn, nocturne •U-turn • upturn