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''Osmunda claytoniana'', the interrupted fern, is a fern native to Eastern Asia and eastern North America, in the Eastern United States and Eastern Canada. The specific epithet is named after the English-born Virginian botanist John Clayton.〔Fernald's "Gray's Manual of Botany" (1950)〕 "Interrupted" describes the gap in middle of the blade left by the fertile portions after they wither and eventually fall off.〔University of Wisconsin-Madison Arboretum, (Interrupted fern profile )〕 The plant is known from fossils to have grown in Europe, showing a previous circumboreal distribution. Fragmentary foliage resembling ''Osmunda claytoniana'' has been found in the fossil record as far back as the Triassic, and is known as †''Osmunda claytoniites''. ''O. claytoniana'' is a paramount example of evolutionary stasis. Paleontological evidence indicates it has remained unchanged, even at the level of fossilized nuclei and chromosomes, for at least 180 million years. ==Distribution== ;North America In eastern North America it occurs in: the Great Lakes region; eastern Canada - in southern Manitoba, Ontario, Quebec (north to tree line); and east to Newfoundland; eastern United States - upper New England south through the Appalachian Mountains and Atlantic seaboard, into the Southeastern United States in Georgia and Alabama; and west across the Southern United States to Mississippi River, and back up the Mississippi embayment through the Midwestern United States to the Great Lakes. ;Asia In eastern Asia, the fern is found in the subtropical and temperate Asia in: the Eastern Himalaya, South Central China and Eastern China, Taiwan, the Korean Peninsula, the Ryukyu Islands, and Japan. 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「Osmunda claytoniana」の詳細全文を読む スポンサード リンク
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