Confidence: I'm as sure as I can be.
Notes: These are tha basal squamules of C. polydactlya, very greyish, with deeply indented margins and sorediate (powderey) at the margins and beneath. Not usually wise to identify a Cladonia from squamules alone, they are difficult enough when fruiting, but I see a lot of this and it is common in this state on nutrient-poor tree trunks. I am puzzled by the suggestion that this is wet - it (and other lichens) would be much more green if wet. This is the correct colour for C. polydactyla when merely dampish to dry.