Fern allies are a diverse group of seedless

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They ...

s that are not true

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...

s. Like ferns, a fern ally disperses by shedding

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

s to initiate an

alternation of generations Alternation of generations (also known as metagenesis or heterogenesis) is the predominant type of life cycle in plants and algae. It consists of a multicellular haploid sexual phase, the gametophyte, which has a single set of chromosomes alt ...

Classification

Originally, three or four groups of plants were considered to be fern allies. In various classification schemes, these may be grouped as classes or divisions within the plant kingdom. Fern allies and ferns were sometimes grouped together as division

Pteridophyta A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as " cryptogams", meaning that their means of reproduction is hidden. Ferns ...

. Another traditional classification scheme of living plants is as follows (here, the first three classes are the "fern allies"): *Kingdom:

Plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...

ae **Division

Tracheophyta Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They a ...

(vascular plants) ***Class Lycopsida,

clubmoss Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching ...

es and related plants (fern-allies) ***Class

Sphenopsida Equisetidae is one of the four subclasses of Polypodiopsida (ferns), a group of vascular plants with a fossil record going back to the Devonian. They are commonly known as horsetails. They typically grow in wet areas, with whorls of needle-like ...

or Equisetopsida,

horsetail ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass ...

s and scouring-rushes (fern-allies) ***Class Psilopsida,

whisk fern ''Psilotum'' is a genus of fern-like vascular plants. It is one of two genera in the family Psilotaceae commonly known as whisk ferns, the other being ''Tmesipteris''. Plants in these two genera were once thought to be descended from the ear ...

s (fern-allies) ***Class Filices or Pteropsida, true ferns ***Class Spermatopsida (or sometimes as several different classes of seed-bearing plants) More recent evidence shows that the class Filices, as described above, is not

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

. The following classification represents a consensus view (although different authors may use different names for the various groups): *Kingdom Plantae
Subkingdom Tracheobionta **Division

Lycopodiophyta The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plantae. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldes ...

***Class

Lycopodiopsida Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

, clubmosses ***Class Selaginellopsida,

spikemoss ''Selaginella'' is the sole genus of vascular plants in the family Selaginellaceae, the spikemosses or lesser clubmosses. This family is distinguished from Lycopodiaceae (the clubmosses) by having scale-leaves bearing a ligule and by having ...

es ***Class

Isoetopsida Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

quillwort ''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...

s and scale trees **Division

***Class Equisetopsida, horsetails and scouring-rushes ***Class Psilotopsida,

s, adders'-tongues and

moonwort ''Botrychium'' is a genus of ferns, seedless vascular plants in the family Ophioglossaceae. ''Botrychium'' species are known as moonworts. They are small, with fleshy roots, and reproduce by spores shed into the air. One part of the leaf, the ...

s ***Class

Marattiopsida Marattiaceae is the only family of extant (living) ferns in the order Marattiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Marattiales is the only order in the subclass Marattiidae. The family has six genera and abou ...

, marattioid ferns ***Class

Pteridopsida The Polypodiidae, commonly called leptosporangiate ferns, formerly Leptosporangiatae, are one of four subclasses of ferns, and the largest of these, being the largest group of living ferns, including some 11,000 species worldwide. The group has ...

, leptosporangiate ferns (also called Polypodiopsida or Filicopsida) **Division

Spermatophyta A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryophytes or land plants. They inc ...

(or as several different divisions of seed-bearing plants) Note that in either scheme, the same basic groups are recognized (Lycopodiophyta, Equisetopsida, Psilotopsida), but in the most recent scheme only the Lycopodiophyta is not classified with the ferns.

Relationships

Historically, several groups of plants were considered "fern allies": the

es,

es, and

s in the Lycopodiophyta, the

s in

Psilotaceae Psilotaceae is a family of ferns (class Polypodiopsida) consisting of two genera, ''Psilotum'' and '' Tmesipteris'' with about a dozen species. It is the only family in the order Psilotales. Description Once thought to be descendants of early v ...

, and the

s in the

Equisetaceae Equisetaceae, sometimes called the horsetail family, is the only extant family of the order Equisetales, with one surviving genus, ''Equisetum'', which comprises about twenty species. Evolution and systematics Equisetaceae is the only survivin ...

. Similarly, three discrete groups of plants had been considered ferns: the adders-tongues,

s, and grape-ferns ( Ophioglossales), the

Marattiaceae Marattiaceae is the only family of extant (living) ferns in the order Marattiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Marattiales is the only order in the subclass Marattiidae. The family has six genera and about ...

, and the leptosporangiate ferns. More recent genetic studies have shown that the Lycopodiophyta are only distantly related to any other

s, having radiated evolutionarily at the base of the vascular plant

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

, while both the whisk ferns and horsetails are as much true ferns as are the Ophioglossoids and Marattiaceae. The Marattiaceae are a group of tropical ferns with a large, fleshy rhizome, and are now thought to be a sister group to the main group of ferns, the leptosporangiate ferns. The whisk ferns and Ophioglossids are demonstrably a clade, however, the relationships between this group, the leptosporangiate ferns+marattiaceae, and the horsetails remains uncertain.

References

External links

Common Ferns and Fern-Ally Species
{{Webarchive, url=https://web.archive.org/web/20120513154126/http://www.borealforest.org/ferns.htm , date=2012-05-13

(uses frames)

*Lord, Thomas R. (2006). Ferns and Fern Allies of Pennsylvania. Indiana, PA: Pinelands Pres

Cryptogams