Cyatheaceae
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Cnemidaria |
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The Cyatheaceae is a family of fern that includes the world's tallest tree ferns, which reach heights up to 20 m. They are also very ancient plants, appearing in the fossil record in the late Jurassic, though the modern genera likely appeared in the Tertiary.
All Cyatheaceae have scales instead of hairs, which are common in members of the family Dicksoniaceae. Their fronds are also very large, some of the largest in the plant kingdom. Some species have fronds reaching 3-4 m in length, and have a final crown width of some 6 m. The sori (spore clusters) also occur away from the margins of the pinnules (individual leaves), and are elongate or rounded.
Most Cyatheaceae are terrestrial, with one sometimes being epiphytic and others having a creeping habit, but these are exceptions to the family norm.
Since the exact number of species is not known, classification of the Cyatheaceae has had a long and controversial history, and is still undergoing revision. Three tentative clades have been developed: Alsophila, Cyathea, and Sphaeropteris. These are frequently used as genus names. There is one additional genus, Cnemidaria. It is likely that in time the Cyathea will be split into additional genera.
[edit] References
- Braggins, John E. and Large, Mark F. Tree Ferns. Timber Press (2004). ISBN 0-88192-630-2
