The growth and development of several lichens under natural conditions are studied with the SEM. The results permit observations on the influence of the microclimate and of pollution on thalline development and on some principles of lichen systematics.

No abstract

No abstract

A possible source of Trebouia algae for lichens are the thalli of lichens that are attacked by another mycobiont that captures the algae for its own symbiotic use. Such a process is described for Fulgensia bracteata living in parasitic association with Toninia caeruleonigricans. The development of the thalli of Toninia and the parasitic attack of Fulgensia are analysed in detail. The infection of Toninia is achieved by ascosporcs and can be demonstrated by the presence of secondary lichen substances typical for Fulgensia, which occur in infected thalli of Toninia. Fulgensia also overgrows other lichens, but these thalli are not invaded. The special abilities of Toninia and various methods for distribution and regeneration compensate for the parasitism and the association remains stable. The ecology of the small developmental stages of Toninia and Fulgensia shows important differences.R6um6 : Chez les lichens, une source possible d'algue Trebouia pour la formation du lichen reside dans les thalles de lichens qui sont attaquCs par un autre mycobionte, lequel s'approprie des algues de I'h8te pour ses propres fins symbiotiques. Les auteurs decrivent ce procCdC chcz le Fulgensia bracteata vivant en parasite avec le Tonnia caeruleonigricans. 11s analysent en d6tails le d6veloppement du thalle du Toninia et l'attaque parasitaire du Fulgensia. L'infection du Toninia est rkaliste par des ascospores et peut &re dCmontrCe par la presence de mktabolites lichkniques secondaires typiques du Fulgensia, lesquels se retrouvent dans les thalles infect& du Toninia. Le Fulgensia peut Cgalement attaquer d'autres lichens mais sans en envahir les thalles. Les capacitCs speciales du Toninia ainsi que diffkrentes mtthodes de distribution et de reginbration compensent pour le parasitisme et l'association demeure stable. L'Ccologie des premiers stades de dtveloppement du Toninia et du Fulgensia montrent des diffirences importantes.

No abstract