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Potamogeton natans

Potamogeton natans

Potamogeton natans

Potamogeton natans

Potamogeton natans

わが国の中部地方以東から北海道、それに北半球の温帯域に分布しています。池沼や河川に生え、高さは2〜3メートルになります。水中の地下茎から茎を伸ばし、浮葉と沈水葉をつけます。浮葉は長楕円形で長さ5〜12センチ、沈水葉は線形で長さ12〜30センチです。5月から8月ごろ、花茎に穂状花序をだします。果実は長さ4〜5ミリで、倒卵形です。 
ヒルムシロ科ヒルムシロ属の多年草で、学名は Potamogeton natans。英名は Broad-leaved pondweed。 
The Broad-leaved pondweed (Potamogeton natans) belongs to Potamogetonaceae (the Pondweed family). It is a perennial herb that is native eastward from Chubu district of Honshu to Hokkaido, and widely in the temperate area of the Northern Hemisphere. This herb grows in ponds and streams, and it can reach 2-3 m in height. The stems are borne from aquatic rootstocks and pruduce both floating and submersed leaves. The floating leaves are 5-12 cm long and oblong, and the submersed leaves are 12-30 cm long and linear. The spikes are borne on the flowering stalks from May to August. The fruits are 4-5 mm long and obovate. 
福島県檜枝岐村「浅湖(あさみ)湿原」にて、2013年08月25日撮影。 

Shu Suehiro
shu@botanic.jp