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thumb ''Taeniocrada'' is a genus of extinct plants of Devonian age (). It is used as a form genus for fossil plants with leafless flattened stems which divided dichotomously and had prominent midribs regarded as containing vascular tissues.〔 It has been suggested that some species assigned to this genus were aquatic.〔 ==Description== Key features of the original definition of the genus ''Taeniocrada'' were that it possessed leafless flattened stems with prominent midribs which appeared to contain vascular tissues. As more species were added to the genus, its definition became less clear.〔 Three of the better-known species are ''T. decheniana'', ''T. dubia'' and ''T. stilesvillensis''. ''Taeniocrada decheniana'', from the Lower Devonian,〔 had separate fertile stems which repeatedly branched in a dichotomous fashion ending in sporangia between 3 and 7 mm long. A few sporangia were borne on the sides of stems. The species was found in dense stands. It has been suggested that it was aquatic or semi-aquatic because it apparently did not have stomata on the flattened stems.〔 ''Taeniocrada dubia'', from the Lower Devonian,〔 was originally considered to be a rhyniophyte, i.e. a very early vascular plant, but this has been questioned. The central strand appears to have been composed of tubes of differing diameters with helical thickenings which were part of the original cell wall, rather than being produced as the cell matured as would be the case in the xylem of vascular plants.〔 ''Taeniocrada stilesvillensis'', from the Upper Devonian of New York, had stems which divided either into two equal branches (i.e. dichotomously) or so that one branch was more of a 'main stem' than the other (i.e. pseudomonopodially). Ridges along the stem bore hair-like structures. True vascular tissue was present.〔 A further nine species still considered to be part of the genus are listed and in some cases briefly described by Taylor (1986).〔 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「Taeniocrada」の詳細全文を読む スポンサード リンク
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