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Fern, or pteridophyte, is any one of a group of some twenty thousand species of plants. A fern is defined as a vascular plant that reproduces by shedding spore to initiate an alternation of generations, and forms new fronds by circinate vernation.
A group of plants that may be termed ophioglossoids was once considered to be true ferns, but is now known to be an isolated group. These include plants traditionally grouped in the family Ophioglossaceae, including adders-tongues and grape-ferns. These are now considered to be "fern-allies."
Fern's life cycle consists of two distinct stages:
A typical life cycle:
A sporophytic fern contains
A gametophytic fern contains:
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):
The last group includes most plants familiarly known as ferns.
A more complete classification scheme follows:
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.
Pterophyta, the Ferns
Scientific classification
Kingdom: Plantae
Division: Pterophyta Classes
Table of contents
1 Life cycle
2 Structure
3 Classification
4 Economic Uses
Life cycle
Structure
Classification
Economic Uses