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| image = Equisetopsida.jpg | image_caption = "Candocks" of the Great Horsetail (''Equisetum telmateia'' subsp. ''telmateia''), showing whorls of branches and the tiny dark-tipped leaves | image_width = 240px | genus = ''Equisetum'' | genus_authority = L. | subdivision_ranks = Species | subdivision = see text }} ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.〔''Sunset Western Garden Book,'' 1995:606–607〕 ''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 dominated the understory of late Paleozoic forests. Some Equisetopsida were large trees reaching to 30 meters tall.〔(【引用サイトリンク】publisher=Florida International University )〕 The genus ''Calamites'' of the family Calamitaceae, for example, is abundant in coal deposits from the Carboniferous period. A superficially similar but entirely unrelated flowering plant genus, mare's tail (''Hippuris''), is occasionally referred to as "horsetail", and adding to confusion, the name mare's tail is sometimes applied to ''Equisetum''. It has been suggested that the pattern of spacing of nodes in horsetails, wherein those toward the apex of the shoot are increasingly close together, inspired John Napier to discover logarithms. ==Etymology== The name "horsetail", often used for the entire group, arose because the branched species somewhat resemble a horse's tail. Similarly, the scientific name ''Equisetum'' derives from the Latin ''equus'' ("horse") + ''seta'' ("bristle"). Other names include candock for branching individuals, and snake grass or scouring-rush for unbranched or sparsely branched individuals. The latter name refers to the rush-like appearance of the plants, and to the fact that the stems are coated with abrasive silicates, making them useful for scouring (cleaning) metal items such as cooking pots or drinking mugs, particularly those made of tin. In German, the corresponding name is ''Zinnkraut'' ("tin-herb"). Rough horsetail ''E. hyemale'' is still boiled and then dried in Japan, to be used for the final polishing process on woodcraft to produce a smoother finish than any sandpaper. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「equisetum」の詳細全文を読む スポンサード リンク
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