Physcia austrocaesia

The thallus of Physcia austrocaesia is orbicular or spreading, closely attached or somewhat loosely attached at the margins, measuring 1–6 cm wide. Its lobes are typically 0.5–2.0 (up to 2.5) mm wide, contiguous, overlapping or occasionally separate, and feature irregular or pinnately branched, weakly to distinctly convex structures. The upper surface is light to medium or bluish grey, sorediate, and distinctively white-maculate (spotted) with somewhat raised spots (maculae), occasionally showing grey-white pruina at the tips. The lower surface ranges from off-white to pale brown or brown at the centre. Rhizines (root-like attachment structures) are simple or fasciculate (bundled) at the tips, varying from sparse at the edges to densely crowded and entangled centrally. They are coloured whitish, grey to brown, and measure 0.4−0.9 mm long.^[1]

Physcia austrocaesia is found in southern Australia and New Zealand. It typically grows on moist sandstone ledges along river banks within dry Eucalyptus-Callitris woodlands, adorned with numerous rock outcrops. This species is common in cool-temperate areas on rocks and occasionally on twigs. It is commonly found growing alongside other lichens including Buellia homophylia, B. procellarum, Lecanora pseudistera, Lecidea capensis, Parmotrema reticulatum, Ramboldia pertraeoides, Relicina sydneyensis, Rhizocarpon badioatrum, and various Xanthoparmelia species.^[1]