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Woodwardia virginica
''Woodwardia virginica'' (Virginia chain fern, Woodwardie de virginie) is a leptosporangiate fern with long creeping, scaly, underground stems or rhizomes which give rise to tall (up to about 4 feet, 120 centimetres) widely separated, deciduous, single leaves. In contrast, the leaves of ''Osmundastrum cinnamomeum'', which can be mistaken for ''W. virginica'', grow in a group from a crown. Also in contrast to ''O. cinnamomeum'' the leaves are monomorphic without distinct fertile fronds. The lower petiole or stipe is dark purple to black, shiny and swollen, the upper rachis is dull green. The leaf blade is green and lanceolate, composed of 12 to 23 paired, alternate pinnatifid pinnae. The pinnae are subdivided into 15 to 20 paired segments that are ovate to oblong. The lower rachis is naked for about half its length. The sori or spore-producing bodies are found on the underside of the pinnae and are long and form a double row which outlines the major veins of the pinnae. In common with all ferns, ''W. virginica'' exhibits a gametophyte stage in its life cycle (alternation of generations) and develops a haploid reproductive prothallus as an independent plant. The spores are produced in red-brown sori which line the spaces (areolae) between the costa and costules. Further photographs can be found at the Connecticut Botanical Society and Ontario Ferns websites.
==Taxonomy==
''W. virginica'' has been found as a fossil in the Middle Miocene of Central Washington state. At that time it apparently grew in similar habitats and was associated with similar species to the present.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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