[in French with French, Esperanto and English abstract: ] The minimal area of a licheno-bryophytic community (Toninio-Psoretum decipientis Stodiek) is studied hy two methods : - the method of the species-area curve; - the method of the mean similarity-area curve. Only the last method proved to be satisfactory and showed the determination of the qualitative minimal area (250-500cm2) and the quantitative minimal area (500-1000cm2).