Lichens are dual organisms; a fungus and one or more algae in a stable, mutually beneficial (symbiotic) partnership. The fungus provides the visible, structural form and protects the algae from extremes of light and temperature. Algae are capable of photosynthesis and some of the sugars produced provide the fungus with energy for growth and reproduction.
Some lichens can live for many hundreds of years and being sensitive to pollution levels they are important enviromental indicators.
Lichen identification can be very confusing to begin with as there are many similar species but Paul Whelan has recently published a very helpful introduction to the Lichens of Ireland
The first step is to start noticing them and to recognise the different growth forms shown below. Reproductive features, the apothecia (fruiting bodies), isidia (tiny outgrowths) or soredia (often sperical and powdery) are important details that aid identification. (See Glossary) Photographs help but often can't provide an accurate identification as this can require a hand lens, simple chemical tests, microscopic examination or even Thin Layer Chromatography.
Please use the menu bar or the links below to see lichens by growth form, habitat or access species with the A-Z Index.
Crustose, Leprose Squamulose Foliose Cladonia Fruticose, Filamentous
The Burren (limestone) Acidic uplands Coastal Urban, churchyard Trees, wood 'Western oceanic'
For photographs of Fungi, lichenicolous fungi and algae, seaweed, slime moulds and galls please follow the links.
Photographs and details of Wildflowers, Grasses, Sedges and Rushes found in Ireland are at www.irishwildflowers.ie