Pteridophytes (Spore Producing Plants: Ferns and More) • Earth.com

Interrupted Fern

(Claytosmunda claytoniana claytoniana)

galery
en

Description

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."Interrupted" describes the gap in middle of the blade left by the fertile portions after they wither and eventually fall off.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.Osmunda claytoniana fronds are bipinnate,40?100 cm (16?39 in) tall and 20?30 cm (8?12 in) broad,the blade formed of alternate segments forming an arching blade tightening to a pointed end.The lower end is also slightly thinner than the rest of the frond because the first segments are shorter.Three to seven short,cinnamon-colored fertile segments are inserted in the middle of the length,giving the plant its name.In their absence,the plant in all its stages appears similar to Osmundastrum cinnamomeum (cinnamon fern).The base of the segments distinguishes the two species: where O.cinnamomeum has typical felt-like hairs,the few hairs present on O.claytoniana are extremely short,usually requiring a magnifying glass to see well.Like other species in the family Osmundaceae,it grows a very large rhizome,with persistent stipe bases from previous years.It forms small,dense colonies,spreading locally through its rhizome,and often forming fairy rings.

Taxonomic tree:

Domain:
Kingdom: Plantae
Phylum: Pteridophyta
Class: Polypodiopsida
Order:Osmundales
Family:Osmundaceae
Genus:Claytosmunda
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