Envoy at 11:21, 21 October 2007

2007-10-21T11:21:21Z

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{{Taxobox
| color = lightgreen
| name = Tree fern (Cyatheales)
| image = Ferns.jpg
| image_width = 250px
| image_caption = ''Dicksonia antarctica''
| regnum = [[Plant]]ae
| divisio = [[Pteridophyta]]
| classis = [[Pteridopsida]]
| subclassis = [[Cyatheatae]]
| ordo = '''Cyatheales'''
| subdivision_ranks = [[family (biology)|Familes]] and [[Genus|Genera]]
| subdivision =
* '''[[Thyrsopteridaceae]]'''
** ''[[Thyrsopteris]]''
* '''[[Loxomataceae]]'''
** ''[[Loxoma]]''
** ''[[Loxsomopsis]]''
* '''[[Culcitaceae]]'''
** ''[[Culcita]]''
* '''[[Plagiogyriaceae]]'''
** ''[[Plagiogyria]]''
* '''[[Cibotiaceae]]'''
** ''[[Cibotium]]''
* '''[[Cyatheaceae]]'''
** ''[[Alsophila]]''
** ''[[Cyathea]]''
** ''[[Gymnosphaera]]''
** ''[[Hymenophyllopsis]]''
** ''[[Sphaeropteris]]''
* '''[[Dicksoniaceae]]'''
** ''[[Calochlaena]]''
** ''[[Dicksonia]]''
** ''[[Lophosoria]]''
* '''[[Metaxyaceae]]'''
** ''[[Metaxya]]''
}}

The order '''Cyatheales''' is a [[taxonomic]] division of the [[fern]] subclass, [[Cyatheatae]], which includes the '''tree ferns'''.

In general, any [[fern]] that grows with a trunk elevating the [[frond]]s (leaves) above ground level can be called a tree fern. However, the plants formally known as tree ferns comprise a group of large ferns belonging to the families [[Dicksoniaceae]] and [[Cyatheaceae]] in the order Cyatheales.

Tree ferns are found growing in tropical and subtropical areas, including cool to temperate [[rainforest]]s in [[Australia]], [[New Zealand]], [[Malaysia]], [[Lord Howe Island]], and other island groups nearby; a few genera extend further, such as ''Culcita'' in southern [[Europe]]. Like all ferns, tree ferns reproduce by means of [[spore]]s developed in [[Sporangium|sporangia]] on the undersides of the fronds.

[[Image:Dicksonia antarctica Cultivated GardenEngland.jpg|thumb|250px|left|Tasmanian tree fern (''Dicksonia antarctica'') in an English garden. The trunk is 60 cm (24 in) high.]]

The fronds of tree ferns are usually very large and multiple-[[pinnate]] but at least one type has entire (undivided) fronds. The fronds of tree ferns also exhibit [[circinate vernation]], meaning the young fronds emerge in coils that uncurl as they grow.

Unlike [[flowering plant]]s, tree ferns do not form new woody tissue in their trunk as they grow. Rather, the trunk is supported by a fibrous mass of roots that expands as the tree fern grows.

Some tree fern genera — for example ''Dicksonia'' and ''Cibotium'', but not ''Cyathea'' — can be transplanted by severing the top portion from the rest of the trunk and replanting it. If the transplanted top part is kept moist it will regrow a new root system over the next year. The success rate of transplantation increases to about 80% if the roots are dug up intact. If the crown of the [[Tasmanian tree fern]] ''Dicksonia antarctica'' (the most common species in gardens) is damaged, it will die because that is where all new growth occurs. But other clump-forming tree fern species, such as ''D. squarrosa'' and ''D. youngiae'', can regenerate from basal offsets or from "pups" emerging along the surviving trunk length. Tree ferns often fall over in the wild, yet manage to re-root from this new prostrate position and begin new vertical growth.

[[Image:Tree fern frond at Akatarawa.jpg|thumb|250px|left|Tree fern frond by the [[Akatarawa River]], [[New Zealand]]]]
It is not certain how many species of tree fern there are but it is likely to be around a thousand. More new species are discovered in New Guinea with each botanical survey. On the other hand, many species have become [[Extinction|extinct]] in the last century as forest habitats have come under pressure from human intervention.

== Other tree ferns ==
Outside of the Cyatheales a few ferns in other groups could be considered tree ferns, such as several ferns in the family [[Osmundaceae]] that can achieve short trunks under a metre tall and a few species in the genera ''Blechnum, Leptopteris, Sadleria'' and ''Todea'' could also be considered tree ferns in a liberal interpretation of the term.

The families that constitute Cyatheales have been relatively firmly established as a [[clade]] by [[DNA]] sequencing and morphological studies. The order [[Plagiogyriales]], which contains the family Plagiogyriaceae, is most closely related to the Cyatheales, not to the [[Osmundales]] as had been previously supposed.

[[Image:nzfern.arp.500pix.jpg|thumb|right|200px|Transplanted ''Dicksonia antarctica'' tree ferns at Combe Martin Wildlife and Dinosaur Park, North Devon, England.]]

== References ==
* Pryer, K.M., A.R. Smith, and J.E. Skog. 1995. Phylogenetic relationships of extant ferns based on evidence from morphology and rbcL sequences. ''American Fern Journal'' 85: 205-282.
* Braggins, John E. and Large, Mark F. ''Tree Ferns''. Timber Press (2004).
*Smith, A.R., K.M. Pryer, E. Schuettpelz, P. Korall, H. Schneider & P.G. Wolf 2006. {{PDFlink|[http://www.pryerlab.net/publication/fichier749.pdf A classification for extant ferns.]|420 [[Kibibyte|KiB]]}} ''Taxonomy'' '''55'''(3): 705-731.

==External links==
* [http://www.baumfarn.at/treefern Community: Care and propagation of Treeferns] (German/English)

{{commonscat}}

[[Category:Pteridophyta]]

Cyatheales - Revision history

Envoy at 11:21, 21 October 2007