Relatively little is known about the fungi and lichens of the Outer Hebrides. The most comprehensive work is a summary of the collections made over a thirty year period by RWG Dennis (Fungi of the Hebrides, 1986). Currently over 1300 species of fungi and lichens recorded in the Outer Hebrides are listed on the NBN Atlas Scotland, but this is probably not a complete list. This indicates the species diversity but we have very little information on their distribution.
Lichens are composite organisms comprising a fungus, an alga and/or cyanobacterium or more rarely a yeast. This complex relationship enables lichens to colonise a very wide range of habitats. They exhibit a diverse range of forms with either a crustose, leafy (foliose) or branched (fruticose) structure and are usually attached to a substrate such as a tree branch or rocky outcrop, fence posts or roof tiles.
This site is a catalogue of over 430 species recorded in the islands illustrated with photographs taken in the field together with images of their microscopic structure.
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