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''Potamogeton friesii'', known as flat-stalked pondweed,〔 or Fries' pondweed, is an aquatic plant in the genus ''Potamogeton''. It grows mainly in mesotrophic to eutrophic rivers, lakes, ponds and ditches, rarely in brackish water. It occurs in North America, Europe, western Asia and a few scattered locations elsewhere in Asia. ==Description== Flat-stalked pondweed grows annually from turions and seed, producing branching plants with slender, flattened stems that are well-branched. The submerged leaves are long, rather grass-like, sessile, and translucent. The leaf tips are mucronate (i.e. with the midrib extending out of the leaf, giving a pointed appearance).〔 Abundant turions are produced along the stem, especially in autumn as the plant disintegrates. Flat-stalked pondweed could be confused with other fine-leaved pondweeds within its range, especially ''Potamogeton obtusifolius''〔 but potentially also ''P. pusillus''. The combination of open stipules, rounded tips to the leaves, dense flower spikes and a tendency to produce a mass of bushy growth at the surface all help to distinguish this plant, but use of a botanical key or flora is recommended. ''Potamogeton friesii'' is diploid, with 2n=26.〔 Two hybrids of ''Potamogeton friesii'' have been described, with P. crispus (''P''. × ''lintonii'' Fryer) and P. acutifolius (''P''. × ''pseudofriesii'' Dandy & G.Taylor).〔 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 friesii」の詳細全文を読む スポンサード リンク
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