International Equisetological Association Equisetum, Equisetaceae
International Research Botany Group - International Botany Project - Non Profit Research Institute - Research Service
Botanical Team - IEA Promotes Research and Teaching of Taxonomy, Systematics and Phylogeny of Equisetum
Equisetum is the single surviving genus of a class of ancient vascular plants that dates back to the mid-Devonian period (350 + million years ago). Species (no hybrids): 15 (18), nearly worldwide. Plants with jointed stems and distinct nodes. Leaves small, fused into sheaths, tips remaining free, toothlike. Sporangia borne on peltate sporophylls aggregated in cones. Spores green, rather white in hybrids. Gametophytes green, terrestrial, unisexual, male gametophytes smaller than female.
The IEA is a non-profit scientific association which has as its aim the promotion of the developmental
study of Equisetum Biology (Equisetology). The aim of the IEA is to integrate enthusiasts and scientists working in Equisetum,
create a representation of the association and to popularize equisetological knowledge. The IEA acts as a platform for discussion
and cooperation of all enthusiasts and biologists using Equisetum as the objects of their experiments, pure and applied.
IEA has over 150 active members around the world, including many scientists.
The International Equisetological Association (IEA) was founded in 2008 and is dedicated to : the development of Equisetum biology; the distribution of Equisetum information; and international cooperation among Equisetologists and Pterydological organizations. The Association publishes the IEA Paper and organizes the World Equisetum Program, Research Service (WEP).
The IEA is a non-profit organization of multinational membership dedicated to the furtherance of all aspects of Equisetum. As an organization we support and promote education, research, and conservation in these areas. We operate as a formal 'science club' open to all professionals and enthusiasts. We are constantly growing and improving. Currently, we are primarily concerned popularization of research and the creation of networks of companies and researchers.
Themes / Objectives : Introduction to the Genus Equisetum and the Class Equisetopsida as a whole. Taxonomic Study of the Genus Equisetum. Tissue culture system for in vitro in Equisetum species. Influence of the nitrogen form on in vitro organogenesis in Equisetum species. Electron microscopy of dividing cells - spores and cells of Equisetum species. A study and comparison of the habitats of Equisetum species.
“Equisetum is the single surviving genus of a class of ancient vascular plants that dates back to the mid-Devonian period (350 + million years ago). Species (no hybrids): 15 (18), nearly worldwide. Plants with jointed stems and distinct nodes. Leaves small, fused into sheaths, tips remaining free, toothlike. Sporangia borne on peltate sporophylls aggregated in cones. Spores green, rather white in hybrids. Gametophytes green, terrestrial, not mycorrhizal, (bisexual), unisexual (heteromorphic), male gametophytes smaller than female. Equisetum cell walls with (1→3),(1→4)-ß-D-MLGs (Mixed-Linkage Glucans). SiO2 accumulation. However, stomata and the plant itself (Equisetum arvense) can develop normally in the total absence of silicic acid (Law & Exley 2011). Stem with intercalary meristem; n = 108, ancestral 1C genome = 17.08 pg, chondrome with C → U RNA editing (none), atp1 intron 0. Equisetum and its relatives may have been an important component in the diet of sauropod dinosaurs (Hummel et al. 2008; Pickrell 2019)” ..
“Equisetum may be sister to all other ferns, rps4 analysis, and also 4- and 5-gene analyses (Schuettpelz et al. 2006), analyses of several plastid genes (Rai & Graham 2010). Equisetum has no mitochondrial atp1 intron. I suggesting a clade [Psilotales + Equisetales]” ..
“The fossil record suggests that species morphologically of modern aspect appeared in the Mesozoic and all the characteristic synapomorphies of living Equisetum had evolved by the Lower Cretaceous 136 Ma ago” ..
‘’†Equisetum thermale [Channing, Zamuner, Edwards et Guido] confirms the hypothesis that Equisetum was established prior to the Cenozoic and have a history extending back to the Late Jurassic (Equisetum had developed the suite of adaptations required to colonize hot spring–influenced settings in Late Jurassic times and has maintained them for over 150 million years)’’ ..
“According to some authors, the genus Equisetum evolved in the Tertiary, arising from the much older genus Equisetites, dating from the Palaeozoic era - the Permian or the Carboniferous. The Triassic species Equisetites arenaceus was originally included in the genus Equisetum. Some fossil species of the genus Equisetites resemble modern horsetails so much that the generic distinctiveness between Equisetum and Equisetites has been questioned and it has been suggested that Equisetum may be considered the oldest modern vascular plant. More recent phylogenetic analyzes indicate the differentiation of the oldest species of the genus Equisetum at the end of the Triassic and the beginning of the Jurassic. At that time, several lines emerged with the fossil species known from Jurassic fossils: E. thermale, E. laterale, E. dimorphum. One contemporary species of E. bogotense comes from this period. The rest are represented by lines that split in the Cretaceous to form two groups represented by the modern subgenuses Equisetum and Hippochaete. The first of these subgenuses underwent strong differentiation at the end of the Cretaceous period, and the lines of its modern species come from this period. In this group, the only species with a shorter history are E. sylvaticum and E. telmateia, whose last common ancestor grew up in the Pliocene. Similarly, two periods of species differentiation occurred within the second subgenus. The first took place in the Eocene and is remembered by E. scirpoides, while the rest of the modern species only emerged in the Pliocene” ..
“In the Reveal system, the following genuses were distinguished from the genus Equisetum: Allostelites [Börner] and Hippochaete [J. Milde]. However, such a division is not used in the scientific literature” ..
“According to phylogenetic analyzes carried out by Jean-Michel Guillon, the most basal representative of the genus is Equisetum bogotense. Incorporating it in the Equisetum subgenus not including the Hippochaete subgenus makes this subgenus a paraphyletic taxa” ..
“Equisetaceae [Michx. ex DC.] The only modern representative is the genus Equisetum [L.] Fossil plants of this family are usually classified as Morphotaxon Equisetites. These include morphologically diverse plants known from different continents, found mainly in Triassic and younger rocks, rarely already Carboniferous” ..
“The first Equisetum-Equisetites species appeared in the upper Devon about 375 million years ago. The genus Equisetum can therefore be called living fossils” ..
“Equisetales [DC. ex Bercht. & J. Presl] Four families, of which only Equisetaceae have modern representatives. These plants occur on Earth from the Devonian, but played a special role in the Carboniferous vegetation. Plants of various sizes, from small herbaceous plants to extinct calamites reaching about 20 (30) m high. The following taxa are distinguished: Calamitaceae (+Asterocalamitaceae), Equisetaceae, Tchernoviaceae, Gondwanostachyaceae (Formerly: +Phyllothecaceae, +Schizoneuraceae). Fossil taxa with an unclear taxonomic position: Annularia, Schizoneura, Neocalamites, Spaciinodum” ..
“Equisetopsida [C. Agardh] The class is fossil, living representatives are classified in one genus - Equisetum. Taxonomy: Equisetidae [(Warm.) / Engl. & Gilg], Equisetales [(Dumort.) / DC. ex Bercht. & J. Presl], Equisetineae [Rabenh.], Equisetaceae [Michx. ex DC.], Equisetum [L.] /// Hyeniales, Hyeniaceae /// Sphenophyllales [Seward], Sphenophyllaceae, Cheirostrobaceae /// Calamitales, Calamitaceae [Unger]” ..
“Equisetophyta [D. H. Scott / B. Boivin] The group is fossil, living representatives are classified in one genus - Equisetum. Taxonomy: Equisetophytina [Reveal], Equisetopsida [C. Agardh]” ..
“Horsetails, Equisetophyta emerged from one trunk of Trimerophytes, Trimerophyta” ..
/ Radosław Janusz Walkowiak, 2008
“Trimerophyta is a cluster of fossil plants, very old terrestrial vascular plants that lived from early to middle Devonian. This group is paraphyletic; that is, it does not include all the descendants of a common ancestor. Trimerophytes were characterized by leafless shoots dividing pseudomonopodially, dichotomously or trichotomously, but one branch was more developed than the other, forming a sort of principal axis. The dichotomous branches shortened as they moved away from the main axis, creating tufted sporangia at the ends of only the side branches. Conductive bundles in trimerophytes were thicker than in rhyniophytes. Trimerophytes reached 1 m in height. Large trimerophytes were among the largest plants of the early Devonian. Trimerophytes descended from the oldest terrestrial plants - rhyniophytes, and gave rise to the extinct Cladoxylophyta, Psilotopsida, Polypodiopsida, Equisetopsida and extinct Progymnospermophyta. Classification of this group, orders: Pertica, Psilophyton, Trimerophyton, Dawsonites” ..
The genus Equisetum [L.] is divided into three distinct lineages, which are usually treated as three subgenus. Hybridization has only been recorded between members of the same subgenus.
Subgenus Paramochaete [Christenh. & Husby]
E. bogotense [Kunth] Andean horsetail, upland South America up to Costa Rica.
The most basal (phylogenetics) representative of the genus. 10–40 cm.
Subgenus Equisetum [L.]
E. arvense [L.] Field horsetail, common horsetail.
The plant is widespread. 10–100 cm.
Equisetum diffusum [D.Don.] Himalayan horsetail. Himalayan India
and China and adjacent nations above-about 450 m. 10–90 cm.
Equisetum fluviatile [L. em. Ehrh.] Water horsetail.
Temperate zone, mainly in the Northern Hemisphere.
Equisetum palustre [L.] Marsh horsetail. It is widespread,
mainly in cooler regions of Eurasia and North America.
Equisetum pratense [Ehrh.] Meadow horsetail, shade horsetail, shady horsetail.
The plant is widespread but is usually quite rare. 10-30(50) cm.
Equisetum sylvaticum [L.] Wood horsetail. Northern Hemisphere,
Eurasia and North America. 30-60 cm.
Equisetum telmateia [Ehrh.] Great horsetail, northern giant horsetail.
Europe, Asia Minor, North Africa and west coast of North America.
Equisetum telmateia [Ehrh.] subsp. telmateia. Great horsetail. Europe, western Asia, northwest Africa. Main stem is pale greenish white.
= Equisetum telmateia [Christenhusz et al. 2019]
Equisetum telmateia subsp. braunii [(Milde) Hauke] Northern giant horsetail. Western North America, from southeastern Alaska and western British Columbia south to California. Main stem is green.
= Equisetum braunii [Christenhusz et al. 2019]
Subgenus Hippochaete [(Milde) Baker]
Equisetum giganteum [L.] Southern giant horsetail. 200-500 cm.
South America and Central America, from central Chile east to Brazil and north to southern Mexico. Populations from northern Chile with very stout stems up to 3.5 cm diameter are treated as a separate species Equisetum xylochaetum [Mett.] / [Christenhusz et al. 2019]
Equisetum hyemale [L.] Rough horsetail, rough scouring rush, scouringrush horsetail (snake grass). Holarctic Kingdom, Europe, northern Asia and North America, Mexico, Central America in Guatemala. 30-150 cm.
The North American subspecies Equisetum hyemale ssp./var. affine [(Engelm.) A.A.Eat.] may be treated as a separate species Equisetum prealtum [Raf.] / [Christenhusz et al. 2019]
Equisetum laevigatum [A.Braun] Smooth horsetail, smooth scouring rush. 30-150 cm.
Native to much of North America except for northern Canada and southern Mexico.
It is usually found sandy and gravelly substrates.
Equisetum myriochaetum [Schltdl. & Cham.] Mexican giant horsetail. 450-800 cm.
Nicaragua, Costa Rica, Colombia, Venezuela, Ecuador, Peru, cental Mexico.
It is the largest horsetail species.
Equisetum ramosissimum [Desf.] Branched horsetail. 20-80(100) cm.
Asia, Europe, Africa, southwest Pacific islands.
E. ramosissimum [Desf.] subsp./var. ramosissimum is native through much of Asia, Europe, and Africa, with an introduced population in the southeast United States.
E. ramosissimum [Desf.] subsp. debile [(Roxb. ex Vaucher) Hauke] is found in southeast Asia and some Pacific islands
= E. ramosissimum [Desf.] var. huegelii [(Milde) Christenh. & Husby, 2019]
The type subspecies has more obvious branching from the aerial stem than subspecies debile.
Equisetum scirpoides [Michx.] Dwarf scouring rush, dwarf horsetail.
North Eurasia and North America, cool temperate zones. 3-30 cm.
It is the smallest horsetail species.
Equisetum scirpoides [Michx.] ssp. scirpoides (5-30 cm)
Equisetum scirpoides [Michx.] ssp. walkowiaki [R. J. Walkowiak, 2008]; (3-15/20 cm)
Equisetum variegatum [Schleich. ex F.Weber & D.Mohr] including ssp./var. alaskanum [A.A.Eat.] / [Christenhusz et al. 2019] Variegated horsetail, variegated scouring rush. 30-80 cm. It has a circumpolar distribution in the northern hemisphere (cool temperate zones), in the northern Europe, Asia, North America, Greenland, Iceland, Faroe Islands, in the Pyrenees, Apennines in Europe, Mongolia, Japan. It occurs in dune slacks, mountain flushes and beside lakes, rivers and canals.
Very well-researched † extinct species:
†Equisetum dimorphum [Elgorriaga] is an extinct horsetail species of the family Equisetaceae, and one of the oldest records of the genus Equisetum. It was found in rocks from the Lower Jurassic of Chubut, Argentina, among other plants as ferns, conifers and pteridosperms. Most closely related to a Equisetum laterale Phillips and Equisetites ferganensis Seward. Temporal range: Pliensbachian. This species was described in 2015 by a team led by Andres Elgorriaga. Morphological curiosity, the species to some extent similar to modern E. hyemale.
†Equisetum thermale [Channing, Zamuner, Edwards & Guido] is an extinct horsetail species in the family Equisetaceae described from a group of whole plant fossils including rhizomes, stems, and leaves. It is a near‐complete Equisetum-species of Late Jurassic age with excellent anatomical preservation. The species is known from Middle to Late Jurassic sediments exposed in the province of Santa Cruz, Argentina. It is one of several extinct species placed in the living genus Equisetum. Temporal range: Callovian – Tithonian. Fossils specimens of Equisetum thermale are highly detailed and complete. Channing and his team published their 2011 type description for E. thermale. The etymology of the chosen specific name thermale is in recognition of both the geology of the type location and as a reference to the original habitat of a hot spring. E. thermale show infrequent branching of the stems, a feature found only in Equisetum-Hippochaete. The stems of E. thermale grew up to 10 cm, and each of the nodes on the stem have up to twelve single veined leaves which correspond to the number of ridges on the stem. Morphological curiosity, the species to some extent similar to modern E. bogotense.
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 × mchaffieae [C.N.Page]; (Equisetum fluviatile × Equisetum pratense)
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)
Equisetum × ferrissii [Clute]; (Equisetum hyemale affine × Equisetum laevigatum)
Equisetum × moorei [Newman]; (Equisetum hyemale × Equisetum ramosissimum)
Equisetum × nelsonii [(A.A.Eaton) Schaffn.]; (Equisetum laevigatum × Equisetum variegatum)
Equisetum × schaffneri [Milde]; (Equisetum giganteum × Equisetum myriochaetum)
Equisetum × trachyodon [(A.Braun) W.D.J.Koch]; (Equisetum hyemale / affine × Equisetum variegatum)
(c) IEA, Radosław Janusz Walkowiak, 2008 - 2020