The Narrow-leaved bur-reed (Sparganium angustifolium) belongs to the family Sparganiaceae. It is a perennial herb that is distributed in Hokkaido, Iwate and Nagano prefectures of Honshu in Japan, as well as in Europe, Siberia and Alaska. It is a submerged to floating aquatic perennial that grows in alpine lakes and marshes, and can reach about 80 cm in height. When the leaves reach the surface of the water, they become floating, reach a length of 2 m, are linear and gradually become thinner, and the tips are rounded. From July to August, the unbranched flower stalks are exposed to the surface of the water, and 2 to 5 female axillary or superaxillary flower heads and 2 to 3 male flower heads are attached separately. The fruits are aggregate fruits, and each fruit is spindle-shaped and floats on the surface of the water.