Fern ally
Encyclopedia
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s that are not true fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s. Like ferns, a fern ally disperses by shedding spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s to initiate an alternation of generations
Alternation of generations
Alternation of generations is a term primarily used in describing the life cycle of plants . A multicellular sporophyte, which is diploid with 2N paired chromosomes , alternates with a multicellular gametophyte, which is haploid with N unpaired chromosomes...
.
Classification
There were originally three or four groups of plants 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. Another traditional classification scheme of living plants is as follows (here, the first three classes are the "fern allies"):- Kingdom: PlantPlantPlants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
ae- Division TracheophytaVascular plantVascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
(vascular plants)- Class LycopsidaLycopodiophytaThe Division Lycopodiophyta is a tracheophyte subdivision of the Kingdom Plantae. It is the oldest extant vascular plant division at around 410 million years old, and includes some of the most "primitive" extant species...
, clubmosses and related plants (fern-allies) - Class Sphenopsida or Equisetopsida, horsetailHorsetailEquisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.Equisetum is a "living fossil", as it is the only living genus of the entire class Equisetopsida, which for over one hundred million years was much more diverse and...
s and scouring-rushes (fern-allies) - Class Psilopsida, whisk ferns (fern-allies)
- Class FilicesFernA fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
or Pteropsida, true ferns - Class Spermatopsida (or sometimes as several different classes of seed-bearing plants)
- Class Lycopsida
- Division Tracheophyta
More recent evidence shows that the class Filices, as described above, is not monophyletic. The following classification represents a consensus view (although different authors may use different names for the various groups):
- Kingdom Plantae
Subkingdom TracheobiontaVascular plantVascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
- Division LycopodiophytaLycopodiophytaThe Division Lycopodiophyta is a tracheophyte subdivision of the Kingdom Plantae. It is the oldest extant vascular plant division at around 410 million years old, and includes some of the most "primitive" extant species...
- Class LycopodiopsidaLycopodiopsidaLycopodiopsida is a class of plants often loosely grouped as the fern allies. Traditionally the group included not only the clubmosses and firmosses, but also the spikemosses and the quillworts...
, clubmosses - Class Selaginellopsida, spikemossSpikemossSelaginella is a genus of plants in the family Selaginellaceae, the spikemosses. Many workers still place the Selaginellales in the class Lycopodiopsida . This group of plants has for years been included in what, for convenience, was called "fern allies". S...
es - Class IsoetopsidaIsoetopsidaThe Isoetopsida is a class of the Lycopodiophyta. All living plants belong to the genus Selaginella in the Selaginellales or to Isoetes in the order Isoetales. In the past, members of this group have sometimes been placed in the class Isoetopsida, sometimes in the Selaginellopsida or Lycopodiopsida...
, quillworts and scale treesLepidodendronLepidodendron is an extinct genus of primitive, vascular, arborescent plant related to the Lycopsids . It was part of the coal forest flora. They sometimes reached heights of over , and the trunks were often over in diameter, and thrived during the Carboniferous period...
- Class Lycopodiopsida
- Division PteridophytaFernA fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
- Class EquisetopsidaEquisetopsidaEquisetopsida, or Sphenopsida, is a class of plants with a fossil record going back to the Devonian. They are commonly known as horsetails...
, horsetails and scouring-rushes - Class PsilotopsidaPsilotopsidaPsilotopsida is a class of fern-like plants. It should not be confused with the obsolete class Psilophytopsida. As circumscribed by Smith et al. Psilotopsida contains two families, Psilotaceae and Ophioglossaceae, placed in orders Psilotales and Ophioglossales, respectively...
, whisk ferns, adders'-tonguesOphioglossumOphioglossum is a genus of about 25-30 species of Ophioglossales in the family Ophioglossaceae, with a cosmopolitan but primarily tropical and subtropical distribution. The name Ophioglossum comes from the Greek, and means "snake-tongue".Adders-tongues are so-called because the spore-bearing stalk...
and moonwortMoonwortMoonworts are ferns, seedless vascular plants, of the genus Botrychium, sensu stricto. They are small, with fleshy roots, and reproduce by spores shed into the air. One part of the leaf, the trophophore, is sterile and fernlike; the other, the sporophore, is fertile and carries the clusters of...
s - Class MarattiopsidaMarattiopsidaClass Marattiopsida is a group of ferns containing a single order, Marattiales, and family, Marattiaceae. Class Marattiopsida diverged from other ferns very early in their evolutionary history and are quite different from many plants familiar to people in temperate zones. Many of them have massive,...
, marattioid ferns - Class Pteridopsida, leptosporangiate ferns (also called Polypodiopsida or Filicopsida)
- Class Equisetopsida
- Division Spermatophyta (or as several different divisions of seed-bearing plants)
- Division Lycopodiophyta
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
Another way of looking at this relationship is as follows. Several groups of plants were considered "fern allies": the clubmosses, spikemossSpikemoss
Selaginella is a genus of plants in the family Selaginellaceae, the spikemosses. Many workers still place the Selaginellales in the class Lycopodiopsida . This group of plants has for years been included in what, for convenience, was called "fern allies". S...
es, and quillworts in the Lycopodiophyta, the whisk ferns in Psilotaceae
Psilotaceae
Psilotaceae is a family of fern-like plants consisting of two genera, Psilotum and Tmesipteris. The two genera are very different and in the past Tmesipteris has been placed in its own family, Tmesipteridaceae, but most classifications continue to treat it in Psilotaceae...
, and the horsetail
Horsetail
Equisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.Equisetum is a "living fossil", as it is the only living genus of the entire class Equisetopsida, which for over one hundred million years was much more diverse and...
s in the Equisetaceae
Equisetaceae
Equisetaceae, sometimes called the horsetail family, is the only extant family of the class Equisetales, with one surviving genus, Equisetum, which comprises about twenty species.- Evolution and systematics :...
. Traditionally, three discrete groups of plants had been considered ferns: the adders-tongues
Ophioglossum
Ophioglossum is a genus of about 25-30 species of Ophioglossales in the family Ophioglossaceae, with a cosmopolitan but primarily tropical and subtropical distribution. The name Ophioglossum comes from the Greek, and means "snake-tongue".Adders-tongues are so-called because the spore-bearing stalk...
, moonwort
Moonwort
Moonworts are ferns, seedless vascular plants, of the genus Botrychium, sensu stricto. They are small, with fleshy roots, and reproduce by spores shed into the air. One part of the leaf, the trophophore, is sterile and fernlike; the other, the sporophore, is fertile and carries the clusters of...
s, and grape-ferns (Ophioglossales
Ophioglossales
Ophioglossales are a small group of pteridophyte plants. Traditionally they are included in the division Pteridophyta, the ferns, originally as a family and later as the order Ophioglossales...
), the Marattiaceae
Marattiopsida
Class Marattiopsida is a group of ferns containing a single order, Marattiales, and family, Marattiaceae. Class Marattiopsida diverged from other ferns very early in their evolutionary history and are quite different from many plants familiar to people in temperate zones. Many of them have massive,...
, and the leptosporangiate
Sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
ferns. More recent genetic studies have shown that the Lycopodiophyta are only distantly related to any other vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s, having radiated evolutionarily at the base of the vascular plant clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
, 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 these this group, the leptosporangiate ferns+marattiaceae, and the horsetails remains uncertain.
External links
- Common Ferns and Fern-Ally Species
- A Classification of the Ferns and Fern-Allies (uses frames)
- Non-seed plant images at bioimages.vanderbilt.edu
- Lord, Thomas R. (2006). Ferns and Fern Allies of Pennsylvania. Indiana, PA: Pinelands Press http://www.paferns.com