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''Potamogeton natans'' (broad-leaved pondweed, floating pondweed, floating-leaf pondweed) is an aquatic species in the genus ''Potamogeton'' native to quiet or slow-flowing freshwater habitats throughout the Holarctic Kingdom. ==Description== It produces both floating and submersed leaves on the same plant. The floating leaves are ovate to oblong-ovate and almost always cordate at the base. They are dark green, leathery, opaque, with translucent longitudinal veins. They are 5 to 10 cm long, pointed at the tips, and rounded at the base. The stipules are 4 to 17 cm long. The submerged grass-like structures are called phyllodes, are actually modified leaf stalks. The stems are cylindrical, without many branches, and grow from 1 to 2 metres. The main difference between this species and other pondweeds is a discoloured flexible joint just below the top of the long leaf stalk. The flower spikes are dense, and cylindrical. They are 5 to 10 cm long, pointed at the tip and rounded at the base. It flowers from May to September. The fruits are 4 to 5 mm long and obovate. 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 natans」の詳細全文を読む スポンサード リンク
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