Equisetum is the only living
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
in the
Equisetaceae, a
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
of vascular plants that reproduce by spores rather than seeds. They are commonly known as
horsetails.
Equisetum is a "
living fossilLiving fossil is an informal term for any living species of organism which appears to be the same as a species otherwise only known from fossils and which has no close living relatives. These species have all survived major extinction events, and generally retain low taxonomic diversities...
," as it is the only known genus of the entire
classIn biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
EquisetopsidaEquisetopsida, or Sphenopsida, is a class of plants with a fossil record going back to the Devonian. Living species are commonly known as horsetails and typically grow in wet areas, with needle-like leaves radiating at regular intervals from a single vertical stem...
, which for over one
hundred million"Hundred Million" is the most popular single from the album Detox by the Canadian band Treble Charger. The song features backing vocals by Deryck Whibley and percussion by Steve Jocz, both from from Sum 41. This was the band's last successful single before their break-up.-Music video:The video...
years was very diverse and dominated the
understoryUnderstory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
of late
PaleozoicThe Paleozoic or Palaeozoic Era is the earliest of three geologic eras of the Phanerozoic eon...
forests. Some Equisetopsida were large
treeA tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s reaching to 30 meters tall; the genus
CalamitesCalamites is a genus of extinct arborescent horsetails to which the modern horsetails are closely related. Unlike their herbaceous modern cousins, these plants were medium-sized trees, growing to heights of more than 30 meters...
of family
CalamitaceaeCalamitaceae is an extinct family of plants related to the modern horsetail. Some members of this family attained tree-like stature during the Carboniferous Period...
for example is abundant in
coalCoal is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
deposits from the
CarboniferousThe Carboniferous is a geologic period and system that extends from the end of the Devonian period, about 359.2 ± 2.5 Ma , to the beginning of the Permian period, about 299.0 ± 0.8 Ma ....
period.
A superficially similar but entirely unrelated
flowering plantThe flowering plants or angiosperms are the most diverse group of land plants. The flowering plants and the gymnosperms are the only extant groups of seed plants...
genus, mare's tail (
HippurisHippuris, the Mare's tail, was previously the sole genus in the family Hippuridaceae. Following genetic research by the Angiosperm Phylogeny Group, it has now been transferred to the family Plantaginaceae, with Hippuridaceae being reduced to synonymy under Plantaginaceae.It includes one to three...
), is occasionally misidentified and misnamed as "horsetail".
Etymology
The name "horsetail", often used for the entire group, arose because the branched species somewhat resemble a
horseThe horse is a hoofed mammal, a subspecies of one of seven extant species of the family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
's tail. Similarly, the scientific name
Equisetum derives from the
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
equus ("horse") +
seta ("bristle").
Other names include
candock for branching individuals, and
scouring-rush for unbranched or sparsely branched individuals. The latter name refers to the plants'
rushJuncus is a genus in the plant family Juncaceae. It consists of 225 to 300 species of grassy plants commonly called rushes. They occur in all wet regions of the world, but rarely in the tropics...
-like appearance, and to the fact that the stems are coated with abrasive
silicateA silicate is a compound containing an ion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate , [SiF6]2−, but the silicate species that are encountered most often...
s, making them useful for scouring (cleaning) metal items such as cooking pots or drinking mugs, particularly those made of
tinTin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead, like the two possible oxidation states +2 and +4...
. In German, the corresponding name is
Zinnkraut ("tin-herb"). Rough Horsetail
E. hyemale is still boiled and then dried in
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, to be used for the final polishing process on
woodcraftWoodcraft is a recreational/educational program devised by Ernest Thompson Seton in 1902, for young people based on camping, outdoor skills and woodcrafts. Thompson Seton's Woodcraft ideas were incorporated into the early Scout movement, but also in many other organisations in many countries.In the...
to produce a smoother finish than any
sandpaperSandpaper is a form of paper where an abrasive material has been fixed to its surface.Sandpaper is part of the "coated abrasives" family of abrasive products. It is used to remove small amounts of material from surfaces, either to make them smoother , to remove a layer of material , or sometimes to...
.
Distribution, ecology and uses
The genus
Equisetum is near-
cosmopolitanIn biogeography, cosmopolitan distribution is a state of being found almost anywhere around the world. A cosmopolitan biological category, e.g. genus, may be called a cosmopolite.Examples of cosmopolitan species:* Humans* House dust mite...
, being absent only from
AustralasiaAustralasia is a region of Oceania: Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes . He derived it from the Latin for "south of Asia" and differentiated the...
and
Antarctica| style="border-top:solid 1px #ccd2d9; padding:0.4em 1em 0.4em 0; vertical-align:top;" | 14,000,000 km
2 280,000 km
2 13,720,000 km
2 |-! style="border-top: solid 1px #ccd2d9; padding: 0.4em 1em 0.4em 0; vertical-align: top;...
. They are
perennial plantA perennial plant or perennial is a plant that lives for more than two years. When used by gardeners or horticulturalists, this term applies specifically to perennial herbaceous plants...
s, either
herbaceousA herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
and dying back in winter as most temperate species, or
evergreenIn botany, an evergreen plant is a plant having leaves all year round. This contrasts with deciduous plants, which completely lose their foliage for part of the year....
as most tropical species and the temperate species Rough Horsetail (
E. hyemale), Branched Horsetail (
E. ramosissimum), Dwarf Horsetail (
E. scirpoides) and Variegated Horsetail (
E. variegatum). They mostly grow 0.2-1.5 m tall, though the "
giant horsetailGiant horsetails are usually living species of horsetail that grow to very large sizes, more than 1.5 meters .The following species are commonly known as "giant horsetails":* Equisetum giganteum...
" are recorded to grow as high as 2.5 m (Northern Giant Horsetail,
E. telmateia), 5 m (Southern Giant Horsetail,
E. giganteum) or 8 m (Mexican Giant Horsetail,
E. myriochaetum), and allegedly even more.
Many plants in this genus prefer wet
sandSand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters. An individual particle in this range size is termed a sand grain...
y
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
s, though some are semi-
aquaticAquatic plants — also called hydrophytic plants or hydrophytes — are plants that have adapted to living in or on aquatic environments. Because living on or under water surface requires numerous special adaptations, aquatic plants can only grow in water or permanently saturated soil...
and others are adapted to wet
clayClay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired...
soils. The stalks arise from
rhizomeIn botany, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
s that are deep underground and almost impossible to dig out. The Field Horsetail (
E. arvense) can be a nuisance
weedA weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-made settings such as gardens, lawns or agricultural areas, but also in parks, woods and other natural areas. More specifically, the term is often...
, readily regrowing from the rhizome after being pulled out. It is also unaffected by many
herbicideA herbicide is a substance used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant hormones...
s designed to kill seed plants, however, as E. arvense prefers an acid soil,
limeAgricultural lime, also called garden lime or liming, is a soil additive made from pulverized limestone or chalk. The primary active component is calcium carbonate...
may be used to assist in eradication efforts to bring the soil
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
to 7 or 8.
If eaten in large quantities, the foliage of some species is
poisonIn the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism...
ous to grazing animals, including (somewhat ironically given its common name) horses. On the other hand, the young fertile stems bearing strobili of some species are cooked and eaten by humans in
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, although considerable preparation is required and care should be taken. The dish is similar to
asparagusAsparagus officinalis is a flowering plant species in the genus Asparagus from which the vegetable known as asparagus is obtained. It is native to most of Europe, northern Africa and western Asia...
and is called tsukushi.
The leaves are used as a dye and give a soft green colour. An extract is often used to provide silica for supplementation.
Anatomy
In these plants the
leavesIn botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In...
are greatly reduced and usually non-photosynthetic. They contain a single, non-branching vascular trace, which is the defining feature of
microphyllThe terminology of fossil plants is in places a little confusing. In the discipline's 200+ year history, certain concepts have become entrenched, even though improved understanding has threatened the foundations upon which they are based...
s. However, it has recently been recognised that horsetail microphylls are probably not primitive like in
LycopodiophytaThe Division Lycopodiophyta is a tracheophyte subdivision of the Kingdom Plantae. It is the oldest extant vascular plant division at around 420 million years old, and includes some of the most "primitive" extant species...
(clubmosses and relatives), but rather advanced
adaptationAdaptation is the process whereby a population becomes better suited to its habitat. This process takes place over many generations, and is one of the basic phenomena of biology....
s, evolved by the reduction of a megaphyll. They are therefore sometimes actually referred to as megaphylls to reflect this
homologyIn evolutionary biology, homology refers to any similarity between characteristics of organisms that is due to their shared ancestry. The word homologous derives from the ancient Greek ομολογειν, 'to agree'. There are examples in different branches of biology...
.
The leaves of horsetails grow in
whorlWhorl is a type of spiral pattern.Other meanings of whorl include:* Whorl , a single, complete 360° turn in the spiral growth of a mollusc shell...
s fused into nodal sheaths. The stems are green and
photosyntheticPhotosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of Bacteria, but not in Archaea...
, and distinctive in being hollow, jointed and ridged (with sometimes 3 but usually 6-40 ridges). There may or may not be whorls of branches at the nodes; when present, these branches are identical to the main stem except being smaller and more delicate.
Spores
The
sporeIn biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions...
s are borne under sporangiophores in
strobiliA strobilus is an organ of many plants that contains the reproductive structures. Strobili are ordinarily called cones in many of these groups...
, cone-like structures at the tips of some of the stems. In many species the cone-bearing stems are unbranched, and in some (e.g. Field Horsetail,
E. arvense) they are non-photosynthetic, produced early in spring separately from photosynthetic sterile stems. In some other species (e.g. Marsh Horsetail,
E. palustre) they are very similar to sterile stems, photosynthetic and with whorls of branches.
Horsetails are mostly homosporous, though in the Field Horsetail smaller spores give rise to male prothalli. The spores have four
elaterAn elater is a cell that is hygroscopic, and therefore will change shape in response to changes in moisture in the environment. Elaters come in a variety of forms, but are always associated with plant spores...
s that act as moisture-sensitive springs, assisting spore dispersal after the sporangia have split open longitudinally.
Evolution and systematics
The
EquisetopsidaEquisetopsida, or Sphenopsida, is a class of plants with a fossil record going back to the Devonian. Living species are commonly known as horsetails and typically grow in wet areas, with needle-like leaves radiating at regular intervals from a single vertical stem...
were formerly regarded as a separate division of spore plants and also called Arthrophyta or Sphenophyta; today they have been recognized as rather close relatives of the typical ferns (
PteridopsidaThe Pteridopsida is a class of plants in the Division Pteridophyta that includes all the leptosporangiate ferns. In the recent 2006 classification by Smith et al. the class is renamed Polypodiopsida...
) and form a specialized lineage of the Pteridophyta.
As mentioned above, all living horsetails are placed in the
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
Equisetum. But there are some
fossilFossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
that are not assignable to the modern genus:
- Pseudobornia contains the oldest known Equisetaceae; it grew in the late Devonian
The Devonian is a geologic period and system of the Paleozoic era spanning from . It is named after Devon, England, where rocks from this period were first studied....
, about 375 million years ago.
- Equisetites is a "wastebin taxon
Wastebasket taxon is a term used in taxonomic circles to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined by their lack of one or more distinct character states or by their not belonging to one or more other taxa...
" uniting all sorts of large horsetails from the MesozoicThe Mesozoic Era is one of three geologic eras of the Phanerozoic eon. The division of time into eras dates back to Giovanni Arduino, in the 18th century, although his original name for the era now called the "Mesozoic" was "Secondary" The Mesozoic Era is one of three geologic eras of the...
; it is almost certainly paraphyletic and would probably warrant to be subsumed in Equisetum. But while some of the species placed there are likely to be ancestral to the modern horsetails, there have been reports of secondary growthIn many vascular plants, secondary growth is the result of the activity of the vascular cambium. The latter is a meristem that divides to produce secondary xylem cells on the inside of the meristem and secondary phloem cells on the outside...
in other Equisetites, and these probably represent a distinct and now-extinct horsetail lineage. Equicalastrobus is the name given to fossil horsetail strobili, which probably mostly or completely belong to the (sterile) plants placed in Equisetites.
Species
The living members of the genus
Equisetum are divided into two distinct lineages, which are treated as subgenera. Hybridogenic species are common, but such hybridization has only been recorded between members of the same subgenus.
In addition, there are numerous ill-determined populations. One of them, the Kamchatka Horsetail ("Equisetum camtschatcense"), is an
ornamentalOrnamental plants are typically grown in the flower garden or as house plants. Most commonly they are grown for the display of their flowers. Other common ornamental features include leaves, scent, fruit, stem and bark. In some cases, unusual features may be considered ornamental, such as the...
forming imposing stands of these archaic plants.
Subgenus
Equisetum
- Equisetum arvense
Equisetum arvense, commonly known as the Field Horsetail or Common Horsetail, is a rather bushy perennial with a rhizomatous stem formation native to the northern hemisphere. These horsetails may have sterile or fertile stems. Sterile stems start to grow after the fertile stems have wilted...
L. - Field Horsetail, Common Horsetail or "giant horsetail"
- Equisetum bogotense
The Andean Horsetail is a herbaceous perennial that reproduces through spores. It has thicker less bushy whorled branches, and a silica rich rhizomatous stem, which roots grow out of, under ground. This stem is a dull dark brown color with glabrous growth aside from the sheathed segments...
KunthCarl Sigismund Kunth , also Karl Sigismund Kunth or anglicized as Charles Sigismund Kunth, was a German botanist...
- Andean Horsetail or "giant horsetail"
- Equisetum diffusum
The Himalayan Horsetail is a perennial that averages at 10-25 inches. The plant is silica rich and has a rhizomatous stem. This shiny brown stem can have many small hair-like roots and may also grow tubers.-External links:...
L. - Himalayan Horsetail
- Equisetum fluviatile L. - Water Horsetail
- Equisetum palustre
Equisetum palustre, the Marsh Horsetail, is a plant species belonging to the division of horsetails .- Description :...
L. - Marsh Horsetail
- Equisetum pratense
Equisetum pratense, commonly known as Meadow Horsetail, Shade Horsetail or Shady Horsetail, is a plant species belonging to the division of horsetails . Shade Horsetail can be commonly found in forests with tall trees or very thick foliage that can provide shade. They also tend to grow closer and...
Ehrh.Jakob Friedrich Ehrhart was a German botanist, a pupil of Carolus Linnaeus at Uppsala University, and later Director of the Botanical Garden of Hannover, where he produced several major botanical works between 1780-1793. Ehrhart was the first author to use the rank of subspecies in botanical...
- Meadow Horsetail, Shade Horsetail, Shady Horsetail
- Equisetum sylvaticum L. - Wood Horsetail
- Equisetum telmateia
Equisetum telmateia is a species of Equisetum with an unusual distribution, with one subspecies native to Europe, western Asia and northwest Africa, and a second subspecies native to western North America...
Ehrh.Jakob Friedrich Ehrhart was a German botanist, a pupil of Carolus Linnaeus at Uppsala University, and later Director of the Botanical Garden of Hannover, where he produced several major botanical works between 1780-1793. Ehrhart was the first author to use the rank of subspecies in botanical...
- Great Horsetail, Northern Giant Horsetail
Subgenus
Hippochaete
- Equisetum giganteum
Equisetum giganteum is a species of horsetail native to South America and Central America, from central Chile east to Brazil and north to southern Mexico....
L. - Southern Giant Horsetail or "giant horsetail"
- Equisetum myriochaetum Schlect. & Cham.
Adelbert von Chamisso was a German poet and botanist.He was born Louis Charles Adélaïde de Chamissot at the château of Boncourt at Ante, in Champagne, France, the ancestral seat of his family...
- Mexican Giant Horsetail or "giant horsetail"
- Equisetum hyemale
Equisetum hyemale is a species of horsetail native to moist forests, forest edges an stream banks, swamps, fens throughout the Holarctic Kingdom...
L. - Rough Horsetail, Scouringrush Horsetail
- Equisetum laevigatum
Equisetum laevigatum is a species of horsetail known by the common names smooth scouring rush and smooth horsetail. This plant is native to much of North America except for northern Canada and southern Mexico. It is usually found in moist areas in sandy and gravelly substrates. It may be annual or...
A. BraunAlexander Carl Heinrich Braun was a German botanist from Regensburg, Bavaria.He studied botany in Heidelberg, Paris and Munich. In 1833 he began teaching botany at the Polytechnic School of Karlsruhe, staying there until 1846...
- Smooth Horsetail
- Equisetum ramosissimum Desf.
René Louiche Desfontaines was a French botanist.Desfontaines was born near Tremblay in Brittany. He attended the Collège de Rennes and in 1773 went to Paris to study medicine. His interest in botany originated from lectures at the Jardin des Plantes given by Louis Guillaume Lemonnier...
- Branched Horsetail
- Equisetum scirpoides Michx.
André Michaux was a French botanist and explorer.-Biography:Michaux was born near Versailles. After the death of his wife he took up the study of botany and was a student of Bernard de Jussieu. In 1779 he spent time studying botany in England, and in 1780 he explored Auvergne, the Pyrenees and...
- Dwarf Horsetail
- Equisetum variegatum
Equisetum variegatum is a horsetail native to the Northern Hemisphere.-Description:...
Schleich. ex Weber & MohrCharles Theodor Mohr was a pharmacist and botanist of German descent who lived and worked in the Americas.-Early life:...
- Variegated Horsetail
Named hybrids
Hybrids between species in subgenus
Equisetum
- Equisetum × bowmanii C.N.Page (Equisetum sylvaticum × Equisetum telmateia)
- Equisetum × dycei C.N.Page (Equisetum fluviatile × Equisetum palustre)
- Equisetum × font-queri Rothm. (Equisetum palustre × Equisetum telmateia)
- Equisetum × litorale Kühlew ex Rupr. (Equisetum arvense × Equisetum fluviatile)
- Equisetum × mildeanum Rothm. (Equisetum pratense × Equisetum sylvaticum)
- Equisetum × robertsii Dines (Equisetum arvense × Equisetum telmateia)
- Equisetum × rothmaleri C.N.Page (Equisetum arvense × Equisetum palustre)
- Equisetum × willmotii C.N.Page (Equisetum fluviatile × Equisetum telmateia)
Hybrids between species in subgenus
Hippochaete
- Equisetum × ferrissii Clute (Equisetum hyemale × Equisetum laevigatum)
- Equisetum × moorei Newman (Equisetum hyemale × Equisetum ramosissimum)
- Equisetum × nelsonii (A.A.Eat.) Schaffn. (Equisetum laevigatum × Equisetum variegatum)
- Equisetum × schaffneri Milde (Equisetum giganteum × Equisetum myriochaetum)
- Equisetum × trachydon A.Braun (Equisetum hyemale × Equisetum variegatum)
External links