Arginase, which acts as a fungal lectin, is secreted from Evernia prunastri thalli mainly during spring although it also appears in the medium during the winter. However, urease, which be haves as a lectin ligand, is only secreted during the autumn and winter. In parallel, aplanosporangia formation and the release of small, young algal cells inside the thallus, occurred under short-day con ditions and low temperature values. Thus, the synchronization of the production of the lectin ligand and algal cell division supports the recognition of new algal cells by the mycobiont forming the thallus. Evernia prunastri, algal division, aplanosporangia, arginase, lectin, urease.