The cryptogamic flora of a small isolated natural fragment of rainforest in south-eastern Tasmania has retained its rainforest character but has been modified in comparison to the flora of large, well-buffered rainforest stands. There is a high proportion of widespread wet forest species and many typical rainforest lichens and bryophytes are absent or represented only by depauperate and/or sterile individuals. The relative proportions of hepatics to mosses is reversed compared with that normally found in rainforest and there is a much lower diversity in the bryophyte flora. In spite of these modifications, the flora of the rainforest fragment is quite distinct from that of the surrounding sclerophyll vegetation. The community acts as a refuge for many species and contributes significantly to the overall biodiversity of the area. The site is very important for biological conservation but the data suggest that the ecosystem is extremely fragile and must be protected from future disturbance if its rainforest flora is to survive. The new combination, Bacidia vallatula (Jatta) Kantvilas, is proposed, and the lichen Byssoloma subdiscordans (Nyl.) P. James is recorded from Tasmania for the first time. ADDITIONAL KEY WORDS: Bacidia - bryophytes - Byssoloma - fragmentation - lichens - Nothofagus - refugia.