The horsetails comprise 15 species of plants in the genus Equisetum. This genus is the only one in the family Equisetaceae, which in turn is the only family in the order Equisetales and the class Equisetopsida. This class is now usually placed as the sole member of the Division Equisetophyta, though some authorities place it instead in the Division Tracheophyta or Archeophyta. The plants in the genus Equisetum are considered fern allies. Other classes and orders of Equisetophyta are known from the fossil record, where they were important members of the world flora during the Carboniferous period. See genus (mathematics) for the use of the term in mathematics. ... Classes Equisetopsida The division Equisetophyta is a taxon in the kingdom Plantae containing primitive land plants. ... Divisions Non-seed-bearing plants Equisetophyta Lycopodiophyta Psilotophyta Pteridophyta Superdivision Spermatophyta Pinophyta Cycadophyta Ginkgophyta Gnetophyta Magnoliophyta The vascular plants are those plants that have specialized cells for conducting water and sap within their tissues, including the ferns, clubmosses, horsetails, flowering plants, conifers and other gymnosperms, but not mosses, algae, and... Fern ally is a general term covering a somewhat diverse group of vascular plants that are not flowering plants and not true ferns. ... FOSSIL is a standard for allowing serial communication for telecommunications programs under DOS. FOSSIL stands for Fido Opus Seadog Standard Interface Layer and was made by a group of Fidonet sysops to make their software work on different machines. ... The term flora has several meanings in English: Flora is a collective term for plant life; as distinct from Fauna (animals). ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 340 million years ago (mya), to the beginning of the Permian period, about 280 mya. ...

Vegetative stem: N = node, I = internode, B = branch in whorl, L = fused megaphylls

The name horsetail arose because it was thought that the stalk resembled a horse's tail; the name Equisetum is from the Latin equus, "horse", and seta, "bristle". Other names, rarely used, include candock (applied to branching species only), and scouring-rush (applied to the unbranched or sparsely branched species). The name scouring-rush refers to its rush-like appearance and, because the stems accumulate abrasive silica, their being used for scouring cooking pots in the past. Lighten image (hope this is an improvement). ... Lighten image (hope this is an improvement). ... Latin is the language that was originally spoken in the region around Rome called Latium. ... Candock is a common name of two different plants, horsetail and water lily. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ...

The genus is near-cosmopolitan, being absent only from Australasia and Antarctica. They are winter-deciduous (temperate species) or evergreen (some tropical species), and are mostly 0.2-1.5 m tall, though E. telmateia can exceptionally reach 2.5 m, and the tropical American species E. giganteum 5 m, and E. myriochaetum 8 m. Australasia is the area that includes Australia, New Zealand, New Guinea, and the many smaller islands in the vicinity, most of which are the eastern part of Indonesia. ... Deciduous forest after leaf fall Deciduous means temporary or tending to fall off (deriving from the Latin word decidere, to fall off). ... This article is about plant types. ...

These are plants without conspicuous leaves, but with hollow, jointed, ascending stems that may or may not have side-branches radiating out from the nodes, depending on species. The stem is ridged and grooved, with from (3-) 6-40 ridges. The leaves are minute, pointed-triangular, and form in a whorl at each node on the stem; there is one leaf for each ridge on the stem. In botany, a leaf is an above-ground plant organ specialized for photosynthesis. ...

The spores are borne in a cone-like structures (strobilus, pl. strobili) at the tip of some of the stems. These reproductive stems are often unbranched, and in some species are non-photosynthetic and produced early in spring separately from photosynthetic sterile stems. Horsetails are mostly homosporous, though in E. arvense, smaller spores give rise to male prothalli. The eusporangia have an annulus that act as a moisture-sensitive spring, ejecting the spores through a weak spot of the sporangia. The term spore has several different meanings in biology. ... Leaf. ... In plants, a characteristic where the plant produces only one kind of spore. ... A sporangium (pl. ...

Strobilus of E. telmateia, terminal on an unbranched stem

Many plants in this genus prefer sandy soils, though some are aquatic and others adapted to wet clay soils. One horsetail, E. arvense, can be a nuisance weed because it readily regrows after being pulled out. The stalk-producing rhizome is deep underground and almost impossible to dig out. It is also unaffected by many herbicides designed to kill seed plants. The foliage is poisonous to grazing animals if eaten in large quantities. Download high resolution version (500x861, 75 KB)Equisetum telmateia (ID by MPF) cone photographed by Eric Guinther in Portland, Oregon (along roadway just upslope of the zoo) on April 25, 2004. ... Download high resolution version (500x861, 75 KB)Equisetum telmateia (ID by MPF) cone photographed by Eric Guinther in Portland, Oregon (along roadway just upslope of the zoo) on April 25, 2004. ... Patterns in the sand Sand is an example of a class of materials called granular matter. ... For the heavy metal band see Soil (band) Soil is the layer of minerals and organic matter, in thickness from centimetres to a metre or more, on the land surface. ... Clay is a generic term for an aggregate of hydrous silicate particles less than 4 μm (micrometres) in diameter. ... Dandelions, shown here in proliferation, are commonly thought of as weeds. ... In botany, a rhizome is a horizontal, usually underground stem of a plant that often sends out roots and shoots from its nodes. ... A herbicide is a pesticide used to kill unwanted plants. ... The spermatophytes comprise those plants that produce seeds. ... The skull and crossbones symbol traditionally used to label a poisonous substance. ...

The horsetails were a much larger and more diverse group in the distant past before seed plants became dominant across the earth. Some species were large trees reaching to 30 m. The genus, Calamites (Family Calamitaceae), is abundant in coal deposits from the Carboniferous period. The spermatophytes comprise those plants that produce seeds. ... The coniferous Coast Redwood, the tallest tree species on earth A tree can be defined as a large, perennial, woody plant. ... Species See text Calamites is a genus of extinct arborescent (tree-like) horsetails to which the modern horsetails (genus Equisetum) are closely related. ... Coal is a fossil fuel extracted from the ground either by underground mining, open-pit mining or strip mining. ...

The superficially similar flowering plant, Mare's tail (Hippuris vulgaris), unrelated to the genus Equisetum, is occasionally misidentified and misnamed as a horsetail. Classes Magnoliopsida - Dicots Liliopsida - Monocots The flowering plants (also angiosperms or Magnoliophyta) are one of the major groups of modern plants, comprising those that produce seeds in specialized reproductive organs called flowers, where the ovulary or carpel is enclosed. ... Species Hippuris montana Hippuris tetraphylla Hippuris vulgaris Hippuridaceae is the Mares tail family. ...

External links

• UK National Collection (http://www.btinternet.com/~pigott/equisetum/) - includes a taxonomic list of all known species and hybrids
• The Wonderful World of Equisetum (http://members.eunet.at/m.matus/)
• Giant horsetails (http://www.fiu.edu/~chusb001/giant_equisetum.html)
• Equisetum hyemale (http://www.floridata.com/ref/e/equi_hye.cfm)
• Horsetail size (http://www.fiu.edu/~chusb001/GiantEquisetum/HowLarge.html)