This is especially the case in the lichens (symbiotic organisms composed of a fungal mycelium in association with algal cells), which are usually exposed to very severe fluctuations in external conditions.
Since about 1880 our knowledge of the species which can enter into such relationships has been materially extended, and the fungal constituents of the Lichens are known to include Basidiomycetes as well as Ascomycetes.
Still, the reindeer frequents it for its lichens, and on the drier slopes of the moraine deposits there occur four species of lemming, hunted by the Arctic fox (Vulpes lagopus).
This is particularly marked in certain lichens of shrubby habit.
~any Algae, lichens, and mosses are included among lithophytes, ai id also Saxifraga Aizoon, S.