Collema flaccidum (Ach.) Ach.

A conspicuous genus member with wide lobes and squamulose isidia. It has a wide ecological amplitude – grows on tree trunks and on mossy siliceous to calcareous rocks. Besides, it may be found also on periodically inundated stones in clear brooks. Collema flaccidum is widespread and locally common in Europe. In the past, the species used to be common even in the Czech Republic, but its number of localities has significantly decreased. Nowadays, it is sparse in the country, occurring mainly on rock substrates. As the epiphyte it is very rare, declined as a result of substate acidification in the second half of the 20th century.

Ascomycota → Lecanoromycetes → Peltigerales → Collemataceae → Collema