Fern

Pterophyta, the Ferns
Scientific classification
Kingdom: Plantae Division: Pterophyta
Classes
Marattiopsida Osmundopsida Gleicheniopsida Pteridopsida

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

Table of contents

1 Fern life cycle 2 Fern structure 3 Classification 4 Economic Uses 5 External Links

Fern life cycle

The life cycle of a typical fern consists of two distinct stages (see alternation of generations) and proceeds as follows:

1. Sporophyte produces spores
2. Spores develops into a prothallus (gametophyte)
3. Prothallus produces gametes
4. Male gamete fertilizes female gamete
5. The fertilized gamete (embryo) grows into a sporophyte (the "fern")

Fern structure

A sporophytic fern consists of:

• Rhizome: Creeping stem, sometimes underground, absorbs nutrients, anchors plant
• Frond ("fern leaf"): green, photosynthesizes
  • Spores develop on surface (usually underside)
• Petiole: stem-like part of leaf
  • When young, it is curled into a fiddlehead

A gametophytic fern contains:

• Thallus: green, photosynthesizes
  • contains gametes
• Rhizoids: root-like stems

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 Pterophyta or Filicophyta. This may be subdivided into four main groups, or classes (or orders if the ferns are considered as a class):

• Marattiopsida
• Osmundopsida
• Gleicheniopsida
• Pteridopsida (or Filicopsida)

The last group includes most plants familiarly known as ferns. A group of plants termed ophioglossoids 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 and grape-ferns.

A more complete classification scheme follows:

• Kingdom: Plantae
  • Division: Pterophyta
    • Class: Marattiopsida
      • Order: Marattiales
      • Order: Christenseniales
    • Class: Osmundopsida
      • Order: Osmundales (the flowering ferns)
    • Class: Gleicheniopsida
      • Subclass: Gleicheniatae
        • Order: Gleicheniales (the forked ferns)
        • Order: Dipteridales
        • Order: Matoniales
      • Subclass: Hymenophyllatae
        • Order: Hymenophyllales (the filmy ferns)
      • Subclass: Hymenophyllopsitae
        • Order: Hymenophyllopsidales
    • Class: Pteridopsida
      • Subclass: Cyatheatae
        • Order: Cyatheales (the tree ferns)
        • Order: Plagiogyriales
        • Order: Loxomales
      • Subclass: Schizaeatae
        • Order: Schizeales (including the climbing ferns)
        • Order: Marsileales (the water-clovers, mosquito fern, water-spangle)
      • Subclass: Pteriditae
        • Order: Lindseales
        • Order: Pteridales (including the brakes and maidenhairs)
        • Order: Dennstaedtiales (the cup ferns)
        • Order: Hypolepidales (including bracken)
      • Subclass: Polypoditae
        • Order: Aspleniales (the spleenworts)
        • Order: Athyriales (including the lady ferns, ostrich fern, maiden ferns, etc.)
        • Order: Dryopteridales (the wood ferns and sword ferns)
        • Order: Davalliales (including the rabbits-foot ferns and Boston ferns)
        • Order: Polypodiales (including the rock-cap ferns or Polypodies)

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:

• Dryopteris filix-mas -- male fern, used as a vermifuge
• Rumohra adiantoides -- floral fern, extensively used in the florist trade
• Osmunda regalis and Osmunda cinnamomea -- royal fern and cinnamon fern, respectively, the root fiber being used horticulturally; the fiddleheads of O. cinnamomea are also used as a cooked green
• Matteuccia struthiopteris -- ostrich fern, the fiddleheads used as a cooked green in North America
• Pteridium aquilinum -- bracken, the fiddleheads used as a cooked green in Japan
• Diplazium esculentum -- vegetable fern, a source of food for some native societies
• tree ferns, used as building material in some tropical locales

In addition, a great many ferns are grown horticulturally.

External Links

• Filicopsida at Tree of Life web project
• A classification of the ferns and their allies