Lichen

A lichen is a symbiotic relationship between a fungus and an alga. By convention, a lichen is referred to by the name of its fungal component.

Tasmania has something over 1300 lichens, around 150 of which are endemic. For field identification purposes, lichens are best grouped according to their structural form.

Is it byssoid, crustose, foliose, or fruticose?

• Byssoid – Wispy, like teased wool
• Crustose – Form a crust which strongly adheres to rock, tree, or bark
• Foliose – Characterised by flattened leaf-like structures (thalli)
• Fruticose – Looks like shrubby or bushy coral

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This site is a photographic field guide rather than a rigorous biological classification of Tasmanian lichens. 
For further information on the formal classification of  lichens, see this article from the Australian National Botanic Gardens.
For an interesting discussion of early interest in the lichens of Tasmania, and a full description of known species at the end of the 19th century, see this 1892 article by Rev. Francis Wilson, from the Royal Society Collection