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Equisetum arvense, the field horsetail or common horsetail, is an herbaceous perennial plant in the Equisetidae (horsetails) sub-class, native throughout the arctic and temperate regions of the Northern Hemisphere. It has separate sterile non-reproductive and fertile spore-bearing stems growing from a perennial underground rhizomatous stem system.
Equisetum (/ ˌ ɛ k w ɪ ˈ s iː t əm /; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. [2]Equisetum is a "living fossil", the only living genus of the entire subclass Equisetidae, which for over 100 million years was much more diverse and dominated the understorey of late Paleozoic forests.
Equisetum praealtum, [1] the scouringrush horsetail, [2] is a species of Equisetum (horsetail) native to North America and northeastern Asia. [1] It was formerly widely treated as a subspecies or variety of the European and west Asian species Equisetum hyemale (rough horsetail), and still is by some authorities.
The green stems grow 50–150 cm tall and 2–8 mm thick. The leaf sheaths are narrow, with 15-20 black-tipped teeth. [2] Many, but not all, stems also have whorls of short ascending and spreading branches 1–5 cm long, with the longest branches on the lower middle of the stem.
In the only extant genus Equisetum, these are small leaves (microphylls) with a singular vascular trace, fused into a sheath at each stem node. However, the leaves of Equisetum probably arose by the reduction of megaphylls , as evidenced by early fossil forms such as Sphenophyllum , in which the leaves are broad with branching veins.
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Equisetum palustre, the marsh horsetail, [2] is a perennial herbaceous pteridophyte belonging to the subclass of horsetails (Equisetidae). It is widespread in cooler regions of Eurasia and North America .
Chemical Agents Warning Properties Latency Period Initial Symptoms Blister Agents Lewisite Gas: colorless Odor: geraniums Seconds to minutes