Scrambled-egg lichen  (Fulgensia fulgens)

Alga:  a collection of taxonomically unrelated groups that share some common features but are grouped together for historical reasons and for convenience. They are of simple construction, and are mainly photoautotrophic, obtaining all their energy from light and carbon dioxide, and possess the photosynthetic pigment, chlorophyll A. They range in complexity from microscopic single cells to very complex plant-like forms, such as kelps. Algal groups include blue-green algae (cyanobacteria), red algae (rhodophyta), green algae (chlorophyta), brown algae and diatoms (chromista) as well as euglenophyta.
Calcareous: containing free calcium carbonate, chalky.
Cyanobacteria: a group of bacteria that are able to photosynthesise and contain the pigment chlorophyll. They used to be known as ‘blue-green algae’. They are thought to have been the first organisms to produce oxygen; fossil cyanobacteria have been found in 3000 million year old rocks. As they are responsible for the oxygen in the atmosphere they have played an essential role in influencing the course of evolution on this planet.
Eutrophication: nutrient enrichment of aquatic or terrestrial ecosystems.
Fungus: fungi are one of the taxonomic kingdoms, separate from plants and animals. They obtain nutrients by absorbing organic compounds from the surrounding environment.
Symbiotic: relationship in which two organisms form a close association, the term is now usually used only for associations that benefit both organisms (a mutualism).
Thallus: type of simple plant body that does not have stems, leaves and roots.

1. National Biodiversity Network Species Dictionary (September 2002)
   http://www.nhm.ac.uk/nbn
   
2. Dobson, F. (2000) Lichens. An illustrated guide to the British species. The Richmond Publishing Co. Ltd., Slough.
   
3. JNCC Plant Status Information (September 2002):
   http://www.jncc.gov.uk/species/pstatus/p4_1_3.htm
   
4. Purvis, O. W., Coppins, B. J., James, P. W. & Moore, D. M. (1992) The lichen flora of Great Britain and Ireland. Natural History Museum Publications. The British Lichen society, London.
   
5. Duckworth, J. & James, P. W. Lichens as indicators of terrestrial eutrophication in the UK (September 2002):
   http://www.plantaeuropa.org/html/conference_2001/docs/Duckworth%20-%20LICHENS%20AS.doc
   
6. Church, J.M., Coppins, B.J., Gilbert, O.L., James, P.W. & Stewart, N.F. (1996) Red Data Book of Britain and Ireland: lichens. Volume 1: Britain. The Joint Nature Conservation Committee, Peterborough.
   
7. Gilbert, OL (2000) Lichens. HarperCollins, London (No 86 New Naturalist Series).
   
8. Hill, D. J. (2002) Pers. comm.