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Osmundaceae is the only fern
Fern

A fern is any one of a group of about 20,000 species of plants classified in the phylum or division Pteridophyta, also known as Filicophyta....
 family of the order Osmundales; an order in the class Polypodiopsida or in some classifications the only order in the class Osmundopsida. This is an ancient (known from the Upper Permian
Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Roderick Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom...
) and fairly isolated group that is often known as the "flowering ferns" because of the striking aspect of the ripe sporangia in Osmunda and Osmundastrum. In these genera the sporangia are borne naked on non-laminar pinnules, while Todea and Leptopteris bear sporangia naked on laminar pinnules.






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Osmundaceae is the only fern
Fern

A fern is any one of a group of about 20,000 species of plants classified in the phylum or division Pteridophyta, also known as Filicophyta....
 family of the order Osmundales; an order in the class Polypodiopsida or in some classifications the only order in the class Osmundopsida. This is an ancient (known from the Upper Permian
Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Roderick Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom...
) and fairly isolated group that is often known as the "flowering ferns" because of the striking aspect of the ripe sporangia in Osmunda and Osmundastrum. In these genera the sporangia are borne naked on non-laminar pinnules, while Todea and Leptopteris bear sporangia naked on laminar pinnules. Ferns in this family are larger than most other ferns.

Ferns of this family form heavy rootstocks with thick mats of wiry roots. Many species form short trunks; in the case of the genus Todea
Todea

The fern genus Todea is known from only two living species. Todea barbara L., known as the king fern, is native to South Africa, New Zealand, and Australia while Todea papuana H....
, they are sometimes considered as tree ferns because of the trunk, although it is relatively short.

The leaf
Leaf

In botany, a leaf is an above-ground plant Organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin, to expose the cells containing chloroplast to light over a broad area, and to allow light to penetrate fully into the tissues....
 tissue ranges from very coarse, almost leathery in the case of the Cinnamon fern
Cinnamon fern

Cinnamon Fern , is a species of eusporangiate fern in the family Osmundaceae. It is native to the Americas and eastern Asia, growing in swamps, bogs and moist woodlands....
 (Osmundastrum cinnamomeum), to delicate and translucent, as in the case of the genus Leptopteris.

Recent research on this family has significantly changed our understanding of the relationships of its species. The most striking finding is that O. cinnamomeum, despite its apparent similarity to Osmunda claytoniana, is actually the most anciently-derived species of the family, and so is a sister clade to the clade that comprises Osmunda, Todea, and Leptopteris (Jud et al. 2008), (Metzgar et al. 2008).