Phylum Versus Division

• A phylum is a taxonomic classification ranked below Kingdom and above Class. The term phylum is used primarily to refer to animals. Plants, including ferns, are normally classified in divisions, rather than in phyla. However, divisions occupy the same taxonomical place and function as phyla.
  
  

Nomenclature

• Historically, ferns were classified as part of the Filices class, or plants with few large leaves. However, modern taxonomy places the ferns in their own phylum or division. This division is called the Pteridophyta. It may also be referred to as the Filicophyta or the Polypodiophyta. When this phylum is treated as a subdivision of the Tracheophyta, or vascular plants, it may be referred to as the Polypodiopsida.
  
  

Orders

• The fern phylum contains four main orders: the Polypodiales, Hydropteridales, Marattiales and Ophioglossales. The Polypodiales include the wood ferns, tree ferns, maidenhair ferns, marsh ferns and bracken ferns. The Hydropteridales include water clover, azolla and floating ferns. The Marattialies contains only vessel ferns, while the Ophioglossales, or snake-tongue ferns, contain the adders tongues, grape ferns and moonworts.
  
  

Types

• Ferns come in two major types: the eusporangiate ferns and the leptosporangiate ferns. Eusporangiate fern spores arise from several epidermal cells, called sporangia. These plants tend to have relatively small root systems and produce large numbers of spores. Leptosporangiate ferns make up a larger group, and produce spores from only one epidermal cell, or sporangium.
  
  

Fern Allies

• Fern allies are plants that closely resemble true ferns, but do not share all the same characteristics. This group includes the clubmosses and their relatives, horsetails and scouring-rushes, and whisk ferns. Fern allies also reproduce via spores, but may not have leaves the way ferns do. These plants are sometimes grouped with ferns under the term pteridophyte.