Usnea
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 Usnea australis
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Usnea is a common and scientific name for several species of lichen in the family Parmeliaceae, that generally grow hanging from tree branches, resembling grey or greenish hair. It is sometimes referred to as Old Man's Beard, Beard Lichen, or Treemoss. Usnea looks very similar to Spanish moss, so much so that the plant's Latin name is derived from it (Tillandsia usneoides, the 'Usnea-like Tillandsia').
Usnea grows in damp forests all over the world. Like other lichens it is a symbiosis of a fungus and an alga. The fungus is an Ascomycota.
Many species have been described. A monography by Józef Motyka from 1947 distinguished 451 species. Many of these are now regarded as morphological varieties and adaptions to local circumstances. The taxonomic categorisation is not yet solved. The number of recognised species in Finland is decreasing for this reason, from 34 in 1951 to 25 in 1963 and only 12 in 2000. It is now noted as including more than 600 species and being one of the largest genera within the Parmeliaceae.(Ref. Wirtz, N. et al 2006.)
Usnea is very sensitive to air pollution, especially sulfur dioxide. Under bad conditions they may grow no larger than a few millimetres, if they survive at all. Where the air is unpolluted, they can grow to 10-20 cm long.
Usnea has been used medicinally for at least 1000 years. Usnic acid (C18H16O7), a potent antibiotic and antifungal agent is found in most species. This, combined with the hairlike structure of the lichen, means that Usnea lent itself well to treating surface wounds when sterile gauze and modern antibiotics were unavailable.
[edit] Species
Some of the species of Usnea include:
- Usnea barbata
- Usnea dasypoga
- Usnea florida
- Usnea hirta
- Usnea longissima
- Usnea rubicunda
- Usnea rubiginea
- Usnea subfloridana
[edit] References
Kirtz, N., Printzen, C., Sancho, L.G. and Lumbsch, H.T. 2006. The phylogeny and classification of Neuropogon and Usnea (Parmeliaceae, Ascomycota) revisited. Taxon 55(2):367 - 376.
[edit] External links
- Pekka Halonen, Studies on the lichen genus Usnea in East Fennoscandia and Pacific North America (PDF)
