Hypogymnia on oak twigs and trunks

Hypogymnia on oak twigs and trunks

Observation - Hypogymnia on oak twigs and trunks - UK and Ireland. Description: Blue-grey,slightly ridged foliose lichen, though difficult to decide between H physodes and H tubulosa

Blue-grey,slightly ridged foliose lichen, though difficult to decide between H physodes and H tubulosa