The Fern reference article from the English Wikipedia on 24-Apr-2004
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Fern

A newer version of this article is available: see Fern at Schools Wikipedia
Pteridophyta, the Ferns
Tree fern
Tree fern
Scientific classification
Kingdom:Plantae
Division:Pteridophyta
Classes

Fern, or pteridophyte, is any one of a group of some twenty thousand species of plants classified in the Division Pteridophyta, formerly known by some as Filicophyta. A fern is defined as a vascular plant that lacks seeds, and that reproduces by shedding spores to initiate an alternation of generations. New fronds arise by circinate vernation (leaf formation by unrolling).

Table of contents
1 Fern life cycle
2 Fern structure
3 Classification
4 Economic uses
5 Misunderstood names
6 External links and references

Fern life cycle

The life cycle of a typical fern consists of two distinct stages or generation phases (see alternation of generations), proceeding as follows:

  1. A sporophyte phase that produces spores by meiosis
  2. A spore grows by cell division into a haploid prothallus (a gametophyte phase)
  3. Prothallus produces gametes
  4. Male gamete fertilizes a female gamete
  5. The fertilized gamete (zygote) grows by cell division into a diploid sporophyte (the "fern")

Fern structure

A sporophytic fern consists of:

A gametophytic fern contains:

Classification

Ferns have traditionally been grouped in the class Filices, but some modern classifications assign them their own division in the plant kingdom, which may be known as Pteridophyta. This may be subdivided into four main groups, or classes (or orders if the ferns are considered as a class):

The last group includes most plants familiarly known as ferns. A group of plants in the Ophioglossophyta was once considered among the true ferns, but is now regarded as an isolated group (see "fern-allies." These are species formerly grouped in the family Ophioglossaceae: adders-tongues, moonworts and grape-ferns.

A more complete classification scheme follows:

Economic uses

Ferns are not as economically important as, say, cereal grains, with one possible exception. Ferns of the genus Azolla, which are very small, floating plants which do not look like ferns, and are called mosquito fern, are used as a biological fertilizer in the rice paddies of southeast Asia.

Other ferns with economic significance include:

In addition, a great many ferns are grown horticulturally. The leatherleaf fern or fancy fern, Rumohra adiantoides, is an especial favorite among florists who use its cut fronds in flower arrangements.

Misunderstood names

Several non-fern plants are called "ferns" and are sometimes popularly believed to be ferns in error. These include: In addition, the book Where the Red Fern Grows has elicited many questions about the mythical "red fern" named in the book. There is no such known plant, although there has been speculation that the Oblique grape-fern, Sceptridium dissectum, could be referred to here, because it is known to appear on disturbed sites and its fronds may redden over the winter.

External links and references