Floating fern family
| Floating fern family | ||||||||||||
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Common swimming fern ( Salvinia natans ), illustration |
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| Systematics | ||||||||||||
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| Salviniaceae | ||||||||||||
| Rchb. |
The swimming fern family ( Salviniaceae ) belongs to the fern family .
features
Roots are present ( Azolla ) or absent ( Salvinia ). The stem axis is a protostele that is dichotomously branched. The leaves are sessile, alternate and small (1 to 25 millimeters). The leaf shape is elongated with a whole leaf margin. The leaf nerve is free ( Azolla ) or anastomosing ( Salvinia ).
The plants are heterospore : there are large megaspores and small microspores. Germination takes place in the spores.
The basic chromosome number in Salvinia is x = 9 (the smallest known in ferns), in Azolla x = 22.
Occurrence
The family is sub-cosmopolitan. They are free-swimming species.
Systematics
Today the two genera Salvinia and Azolla , which have long been run as separate families, are combined in this one family :
- Swimming ferns ( Salvinia Ség. ), With around 10 to 13 species.
- Algae ferns ( Azolla Lam. ), With about 5 to 6 species.
The family has been known for fossils since the Cretaceous .
literature
- Alan R. Smith, Kathleen M. Pryer, Eric Schuettpelz, Petra Korall, Harald Schneider, Paul G. Wolf: A classification for extant ferns. In: Taxon. Volume 55, No. 3, 2006, ISSN 0040-0262 , pp. 705-731, abstract, PDF file .
- David John Mabberley: The Plant Book. A portable dictionary of the higher plants. Cambridge University Press, Cambridge u. a. 1987, ISBN 0-521-34060-8 .
Individual evidence
- ↑ a b Michael Hassler, Bernd Schmitt: World Ferns. Checklist of Ferns and Lycophytes of the World. Version 5.4.1, September 2015. ( online; enter the generic name in the search mask). Karlsruhe 2015.
