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''Posidonia oceanica'' (commonly known as Neptune Grass or Mediterranean tapeweed) is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free floating and known in Italy as "the olive of the sea" (''l'oliva di mare''〔(【引用サイトリンク】title=''Posidonia oceanica'' )〕). Balls of fibrous material from its foliage, known as ''egagropili'', wash up to nearby shorelines. ==Description== ''P. oceanica'' is a flowering plant which lives in dense meadows or along channels in the sands of the Mediterranean. It is found at depths from , according to water clarity. Subsurface rhizomes and roots stabilize the plant while erect rhizomes and leaves reduce silt accumulation. The leaves are ribbon-like, appearing in tufts of 6 or 7, and up to long. Average leaf width is around . The leaves are bright green, perhaps turning brown with age, and have 13 to 17 parallel veins. The leaf terminus is rounded or sometimes absent because of damage. Leaves are arranged in groups, with older leaves on the outside, longer and differing in form from the younger leaves they surround. The rhizome type stems are found in two forms: one growing up to beneath the sand and the other rising above the sand. All stems are approximately thick and upright in habit. This arrangement of the rhizomes eventually forms a mat; the surface contains the active parts of the plant, whereas the center is a dense network of roots and decomposing stems. The flowering plant's common name is Neptune grass. In 2006 a huge clonal colony of ''P. oceanica'' was discovered south of the island of Ibiza. At across, and estimated at around 100,000 years old, it may be one of the largest and oldest clonal colonies on Earth. 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「Posidonia oceanica」の詳細全文を読む スポンサード リンク
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