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''Potamogeton crispus'', the curled pondweed or curly-leaf pondweed, is a species of aquatic plant native to Eurasia but an introduced species and often a noxious weed in North America. ==Description== Curled pondweed is a rhizomatous perennial herb producing a flattened, branching stem up to a meter long. The leaves are linear or oblong in shape. Only submerged leaves are produced, which are sessile, linear or oblong in shape, 25–95 mm long and 5–12 mm wide.〔 The leaves may be bright green, olive green or (especially later in the season) brownish and have noticeably serrated margins, a feature that distinguishes them from other pondweeds. The leaves usually have wavy edges but this is not always apparent, especially on new growth.〔 Turions occur in leaf axils and at stem tips. The inflorescence is a short spike of flowers emerging above the water surface. It flowers from May until October.〔 The turions of the plant develop along with the fruits and germinate, leaving the newly sprouted plants to overwinter.〔 Although quite variable, ''P. crispus'' is usually a straightforward plant to identify. Hybrids with various other pondweeds are recorded, but these do not usually closely resemble ''P. crispus''. There are described hybrids with ''Potamogeton trichoides'' (''P''. × ''bennettii'' Fryer), ''P.perfoliatus'' (''P''. × ''cooperi'' (Fryer) Fryer), ''P. alpinus'' (''P''. × ''olivaceus'' Baagøe ex G.Fisch.), ''P.lucens'' (''P''. × ''cadburyae'' Dandy & G.Taylor), ''P. praelongus'' (''P''. × ''undulatus'' Wolgf.), ''P. ochreatus'' (''P''. × ''jacobsii'' Z.Kaplan, Fehrer & Hellq.) and ''P. friesii'' (''P''. × ''lintonii'' Fryer).〔 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「potamogeton crispus」の詳細全文を読む スポンサード リンク
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