Lots of isidia on upper surface, white tomentous lower surface (so not Collema) Brodo (2016) Leptogium 1. Dry habitat, not submerged 4. Lower surface tomentose with mat of white hairs 5. Isidia present on upper surface 7. Thallus isidiate 9. Fine hairs absent, isidia cylindrical (?) 10. Surface of lobes wrinkled, isidia cylindrical L. pseudofurfur (hopefully) relatively abundant in this area! July 30, 2016: @catchang said these were walnut trees