The Linnaean classification system is used to identify plants in a hierarchal order that explains their relationship to other living organisms. This taxonomic system relies on increasingly more specific categories to identify living things, including ferns. Biologists, scientists and gardeners alike use this system to categorize and identify ferns.
All ferns belong to the Linnaean Plantae kingdom. This identifies them as plants, as opposed to minerals or animals.
The Phylum, or division, lets you know what kind of organism the plant is. Ferns belong to the Tracheophyta division, or the vascular plant phylum. This means that ferns have vascular systems that cycle throughout the plant.
Ferns belong to one Linnaean class, Pteridophyta. These are the horsetail plants and true ferns, sometimes called ferns and fern allies. This class was originally called Filices. It is also referred to as Filicophyta. Another fern taxonomic class exists, called Pteriospermatophyta. This class consists entirely of extinct ferns with seeds, known only from fossils.
Ferns are split up into four distinct taxonomic families. Psilotopsida consists of just under 100 distinct plants and contains the whisk ferns and ophioglossoid ferns. Equisetopsida contains the horsetail ferns and about 15 distinct plants. Mattiopsida contains just over 150 distinct species. Plants in the Mattiopsida family are distinguished by super-sized fronds and fleshy root stocks. The largest Linnaean family of ferns, with more than 9,000 distinct plants, is Polypodiopsida, or the leptosproangiate ferns.
Ferns in the Mattiopsida family are classified in the Marattiales order. Plants in the Psilotopsida family fall under one of two categories: psilotales or ophioglossales. Psilotales lack true leaves, but are molecularly similar to ophioglossales. Ophioglossales produce only one leaf at a time and depend on fungi for energy. The Equisetopsida family contains only one order: Equisetacale. All horsetail ferns belong to this order. The Polypodiopsida family contains eight distinct orders. Osmundales ferns produce showy flowers. Hymenophyllales is the family of bristle ferns consisting of darkly foliaged plants that prefer humid environments. Gleicheniales are tropical ferns, linked on a molecular basis by twisted or curved cell walls. Schizaeales ferns appear with non-fern-like leaves and a trailing habit. Salvinales ferns are water ferns. Cyatheales ferns are tree-like with rigid trunks and large spreads. Polypodiales ferns reproduce via spores and have a ring-like stem interrupted by stalks.
The genus is the "generic" name of the Linnaean classification system. Each order has at least one genus, which further subdivides the plants. The genus name is included in the Latin name of the plant. For example, the male fern is called Dryopteris filix-mas. The word "Drypoteris" is the fern's genus. This name is always capitalized and always precedes the species name. If the exact species is unknown, plants may be referred to by their genus name followed by the abbreviation "spp." The abbreviation stands for the phrase "several species," meaning several species within that particular genus. The term Campyloneurum spp., for example, can refer to any selection or all of the ferns in the Campyloneurum, or strap fern, genus.
The species name is the most specific name given to a plant. It is the name of that plant, and that plant only. It is given in conjunction with the genus classification in order to identify the plant with 100 percent accuracy. In the example of Drypoteris filix-mas, the words "filix-mas" is the species name.