When washed or blown away, or carried by insects, they grow into new lichens. Sometimes the fungal partners make their own fruiting bodies. These vary in appearance, resembling small volcanoes, cups or jam tarts. When these burst, the fungal spores are dispersed but if they do not pair up with the correct algal cells they cannot develop. The algal cells, on the other hand, are able to live independently.
Lichens grow on rocks, walls, trees, fences, roofs and on the ground, as well as on leaves.
They are limited by light, needed by the algae for photosynthesis, and also need clean air. The presence of sulphur dioxide. These plants are therefore good indicators of a clean environment. Since some are more tolerant of pollution than others, the type of lichen growing can tell us how bad the pollution is. Lichens are very hardy in natural conditions, living in the tropics, on mountain tops, in salty seashore splash zones and even polar regions, where they survive temperatures well below freezing.