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Ferns. The plants included under this name comprise an entire order, made up of several
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distinct families. They include plants varying in size from a hair- like creeping stem
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bearing a few simple, moss-like leaves, to tall trees 80 or more feet in height, with a stem
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or trunk nearly a foot in diameter. Singularly enough, the extremes in size are both found
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in tropical regions, in which most of the species abound. Most of the ordinary native
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species, as well as the larger part of those in cultivation, consist of an erect underground
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stem or rootstock with leaves, often called fronds, clustered in dense crowns, or in the
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cases of creeping stems with scattered leaves. In gardening parlance, other plants are
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sometimes called ferns, as species of lycopodium and selaginella, as well as oa em Asparagus
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plumosus.
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In the life of an individual fern plant, two distinct phases occur, represented by two
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separate and unlike plants. The ordinary fern plant represents the asexual phase of growth
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(sporophyte), producing its spores normally in spore-cases, which are borne in masses on the
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back or margin of the leaf, or in. a few cases are grouped in spikes or panicles, or in rare
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cases spread in a layer over the entire under surface of the leaf. The sexual stage
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(gamelophyte) develops from the germinating spore, and consists of a tiny usually scale-like
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green heart- shaped prothallus, which bears the sex- organs (archegonia, female, and
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antheridia, male) on the under surface. After fertilization in the archegonium, the egg
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develops directly into a young fern plant. Many ferns also propagate vegetatively by runners
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or offsets, by bulblet-like buds, and in certain species the tips of the leaves bend over
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and take root, as in our common walking-leaf (Camptosorus, which see).
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Ferns frequently hybridize. The crossing takes place naturally in the prothallium stage.
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They are not crossed by hand, as are the seed-plants, but from the accidental mixing when
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prothallia of allied species are growing together. It is a hybrid between two native
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species; it has been found in the wild in several parts of New England.
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Great diversity has existed in the matter of the separation of the ferns into genera.
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Hooker, relying mainly on artificial characters drawn largely from the sorus, recognized
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about seventy genera only, many of them heterogeneous groups of plants with little
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resemblance in structure, habit or natural affinities. John Smith, relying on stem
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characters, Presl on variation in venation and habit,Fee, Moore,and others, have recognized
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a much greater number of genera, ranging from 150 to 250, or even more. In the very unequal
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treatment by Diels in Die Naturlichen Pflanzenfamilien (Engler & Prantl), some 120 genera
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are recognized. A somewhat similar difference prevails in regard to the number of species.
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The Synopsis Filicum of Hooker and Baker (1874), supplemented by Baker's New Ferns (1892),
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recognizes some 2,700 species. It is the too prevailing tendency in this work (1) to fail to
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recognize many valid species which have been described by German and French botanists, and
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(2) to mass under one name very diverse groups of species from distant quarters of the world
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from 8 to 10 species not infrequently appearing as a single so-called "variable species."
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The most recent book dealing with the whole order of ferns, the Index Filicium by Carl
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Christensen, recognizes approximately 150 genera and 6,000 species, and this number is
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continually increased as the result of further tropical exploration and more careful study.
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New forms are constantly coming in from the less-explored parts of the world, and within the
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last few years several new species have been described from the United States, including
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some from the better-known parts. Of this number some 200 species are in occasional
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cultivation in America, but the species that form the bulk of the fern trade do not exceed
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two dozen. In Europe several hundred species have long been in cultivation. Most of the
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species thrive best in the mountain regions of the tropics, the mountains of Jamaica and
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Java having nearly 600 species each, and the Andes also a large number. About 165 species
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are native in the temperate United States, representing some thirty-five genera; our native
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species are so widely distributed that usually not more than twenty-five to fifty will be
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found within the limits of one state, and the common species of the best locality do not
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number more than twenty. Recent explorations in southern Florida have discovered in that
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state the presence of a considerable number of West Indian species not found elsewhere in
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the United States.
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The ferns are commonly classified as part of a group of spore-bearing plants, with vascular
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(woody) tissue in stem and leaves; this group is technically known as the Pteridophytes, and
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is ordinarily divided into three orders; viz., the Equisetales, including the horsetails'
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and scouring rushes; the Lycopodiales, including the selaginellas and the club mosses, or
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ground pines; and the Filicales, including the true ferns and their nearer allies. The
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Lycopodiales and Equi- setales are really not as closely related to ferns as this grouping
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would indicate.
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It should be noted that neither the family nor the generic limitations are in a settled
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condition. The researches of Bower, Lang, Jeffrey, and others have resulted in some changes
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of classification which are not included below because they are not complete enough. Their
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conclusions are undoubtedly correct but are not at present usable.
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The families of the order Filicales may be distinguished as follows:
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1. Ophioglossaceae. Adder's-Tongue Ferns. Herbaceous small ferns with the sporangia borne in
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spikes or panicles on highly modified divisions of the large fleshy foliage lvs.; prothallium
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tuberous, subterranean, without chlorophyll.
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2. Marattiaceae. Coarse ferns with large fleshy sporangia on the under surface of the lf.,
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arranged in circular or boat-shaped receptacles; prothallium above ground, green.
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3. Hymenophyllaceae. Filmy ferns. Sporangia attached to a thread-like receptacle arising in
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a cup at the end of the lf.: ring complete, horizontal or oblique.
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4. Osmundaceae. Flowering ferns. Coarse swamp ferns developing copious green spores early in
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the season: sporangia in panicles at the apex or middle of the lf. or on separate lvs.
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5. Schizaeaceae. Upright or climbing ferns with ovate sporangia, which open vertically.
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6. Gleicheniaceae. Terrestrial ferns with lvs. of firm texture and usually of indeterminate
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growth: sporangia opening vertically, in clusters of 3-6.
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7. Ceratopteridaceae. Aquatic ferns with succulent foliage: sporangia very large, scattered,
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with a broad ring: lvs. of 2 sorts, the sterile usually floating.
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8. Cyatheaceae. Mostly tree ferns with sessile or short-stalked sporangia in conspicuous
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receptacles, opening obliquely.
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9. Polypodiaceae. Ferns with stalked sporangia, which burst transversely: sori covered with
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a membranous indusium or sometimes naked. This family contains three-fourths of all the
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ferns.
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10. Marsiliaceae. Small plants rooting in mud, the lvs. either quadrifoliate or reduced to
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mere filamentous petioles: sporangia borne in oval conceptacles on the leaf-stalks. Often
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aquatic, with the leaves floating on the surface of water in pools or lakes.
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11. Salviniaceae. Small or minute plants with the aspect of liverworts, floating on the
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surface of pools: sporangia in mostly spherical conceptacles.
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The literature on the ferns is very extensive, since they have ever been attractive plants
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in cultivation. Many of the species have been illustrated in elaborate treatises by Schkuhr,
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Kunze, Hooker, Greville, Blume, Fee, Mettenius, Moore, and others. Our native species have
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been illustrated in the two quarto volumes of D. C. Eaton, "The Ferns of North America." A
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valuable summary of the more common fern species is found in Dr. Christ's "Die Farnkrauter
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der Erde" (1897), and a recent structural and morphological treatment is by Sadebeck, in
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Engler & Prantl: "Die Naturlichen Pflanzenfamilien." Schneider's "Book of Choice Ferns" is
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the most complete treatise on the species under cultivation. A useful American horticultural
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manual is Robinson's "Ferns in Their Homes and Ours." An excellent little handbook for the
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wild species of this country is Underwood's "Native Ferns and Their Allies."
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L. M. Underwood.
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R. C. Benedict.
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}}
{{dablink|This article is about the family of pteridophyte plants. For the environmental organisation, see [[FERN (NGO)]]. For the letter of the [[Ogham]] alphabet, see [[Fern (letter)]]. }}
{{dablink|This article is about the family of pteridophyte plants. For the environmental organisation, see [[FERN (NGO)]]. For the letter of the [[Ogham]] alphabet, see [[Fern (letter)]]. }}
{{Taxobox
{{Taxobox