Usnea subscabrosa
Usnea subscabrosa photo by Bob Klips
DIAGNOSTIC FEATURES: Very thick, hard cortex; isidia in small circular patches, medula K-, found on rock (at least in Ohio); compare with U. amblyoclada also found on rock but more shrubby and less pendant, K+ yellow turning red, and with U. mutabilis reddish medula.
ECOLOGY: General distribution is the southeastern US, extending into New Englan, usually growing on bark, more rarely on rock; recently found at several locations in Jackson County, growing on sandstone.