Gymnocarpium dryopteris, the western oakfern, common oak fern, oak fern, or northern oak fern, is a deciduous fern of the family Cystopteridaceae. It is widespread across much of North America and Eurasia. It has been found in Canada, the United States, Greenland, China, Japan, Korea, Russia, and most of Europe.
It is a seedless, vascular plant (with xylem and phloem) that reproduces via spores (not seeds or flowers) and have a life cycle with alternating, free-living sporophyte and gametophyte phases.
Description
Gymnocarpium dryopteris has small, delicate fronds up to 40 cm (16 inches) long, with ternately-compound pinnae (leaves). Each petiole grows from one node on a creeping rhizome. Fronds occur singly. On the underside of matured pinnae the naked sori can be found (the Latin generic name gymnocarpium means "with naked fruit"). The species grows in coniferous woodlands and on shale talus slopes.
In cultivation in the UK this plant and the cultivar "Plumosum" have gained the Royal Horticultural Society's Award of Garden Merit.
Life-cycle
Like most plant species, oak fern alternates generations, where there is a diploid generation in the form of a sporophyte (which produces spores), and is followed by a haploid generation in the form of a gametophyte (which produces gametes). The sporangia are found in clusters on the underside of the leaf, called sori. Each sporangium produces multiple sporocytes, with each sporocyte dividing twice, giving rise to four non-sexual spores. Often found in drainage areas, ditches and north-facing slopes, it thrives in soils that are well-drained and have a ph of 4.5-6.4. This fern occurs at elevations of along moderately steep slopes with north, east and west aspects.
Gallery
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File:Gymnocarpium dryopteris 6028.JPG|The leaf of the fern Gymnocarpium dryopteris, showing sori (groups of sporangia).
File:Pteridophyte lifecycle.jpg|Life cycle of a pteridophyte.
File:Gymnocarpium dryopteris 6035.JPG|Gymnocarpium dryopteris shown in the middle of the image, surrounded by sword ferns (Polystichum munitum).
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