It is fitting to follow photos of fungi (over the last two days) with LICHENS as lichens are an extraordinary symbiotic living combination of fungi and algae (or occasionally special bacteria). It is the latter which provide food (simple sugars) through photosynthesis for the fungal part of lichens.

Many unrelated and very different fungi form lichens, the majority being cup-fungi although a fifth of all known fungi can form lichens.

Lichens live for hundreds and even thousands of years. Some crustose lichens (which grow flat on rock surfaces) in the Arctic regions are believed to be up to 9,000 years old, growing at a rate of about 0.5mm a year! Keeping track of their growth is a good indicator of climate changes and the quality of the air. Someone I know used to go to Norway every few years through most of his life to measure the growth of specific crustose lichens.

I love the abstract pictures created by the colours and patterns of crustose lichens, especially when they are growing on equally beautiful multi-coloured rocks.