Volume 56A provides treatments of Pertusaria and Lecanora, two of the most speciose and ecologically significant, crustose genera on rock and bark in Australia. Pertusaria, second only to Xanthoparmelia (Parmeliaceae) in terms of the diversity of Australian species, exhibits a high degree of species endemism and is often dominant in tropical, temperate and alpine communities in eastern Australia. The Australian species of Lecanora occur on rock, soil, and on trunks and canopy branches of trees in all ecosystems; some are especially prominent in the comparatively species-poor lichen floras of semi-arid and arid regions. Also included here is Usnea, a genus of robust and often luxuriant lichens ranging from almost rigid tufts on exposed, alpine rocks to metre-long skeins hanging from the canopies of temperate rainforest trees.
Complete or partial accounts of nine families are provided in Volume 56A, including 17 genera and 287 species and infra-specific taxa. This brings to 1168 the number of Australian lichen species and infra-specific taxa treated in the four volumes published.