Tree fern
| Tree fern (Cyatheales) | |
|---|---|
 |
|
| Dicksonia antarctica | |
| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pteridophyta |
| Class: | Polypodiopsida / Pteridopsida (disputed) |
| Order: | Cyatheales |
| Families | |
The order Cyatheales, which includes the tree ferns, is a taxonomic division of the fern class, Polypodiopsida. No clear morphological features characterize all of the Cyatheales, but DNA sequence data indicate the order is monophyletic. Some species in the Cyatheales have tree-like growth forms, but others have rhizomes.
Some species have scales on the stems and leaves, while others have hairs. However, most plants in the Cyatheales are tree ferns and have trunk-like stems up to 10 metres (33 ft) tall. It is unclear how many times the tree form has evolved and been lost in the order.
In general, any fern that grows with a trunk elevating the fronds (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, as well as temperate rainforests in South Africa, Australia, New Zealand, 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 spores developed in sporangia on the undersides of the fronds.
The fronds of tree ferns are usually very large and multiple-pinnated, 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.
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Wikipedia