Lichen, a partnership between a fungus and an alga.

There are more than 1.700 species of lichen in Britain.  They are widespread and may be very long-lived, and have been used for making dyes or perfumes as well as traditional medicines.  They can be eaten (poisonous ones are generally yellow),-  in Northern Europe as an emergency food and in North America, Korea and Japan  as traditional foods. Lichens have been used to extract purple and red colours, and have been used to treat wounds in Russia in the mid 20th century. Most importantly lichens give an indication of  good  air quality.

1. Lichen on flat stone by the sea.      2. Yellow lichen on branch by the sea.      3.  Lichen on stone by the sea.