A kind ofball seaweed（球藻）namedMarimo in Japanese is also known as Moss(苔蘚)Balls or Lake Balls in English. Such balls are only found in lakesin the northern hemisphere（半球）.The action of the wave occasionally（偶爾）turnsMarimo, so they can maintain（維持）theround shape. They grow very slowly—5 mm bigger each year. You canbuy small onesas souvenirs（紀念品）insome aquariums（水族館）.Also, pictures of Marimo are used to make relatedproductssuch as key rings, notebooks, letterpaper, postcards,and so on.