Thallus: fruticose, shrubby, erect, often forming ragged clusters, up to 2 cm long branching: simple or sparingly branched from a narrow or expanded holdfast branches: flat or +inflated, solid but often secondarily subfistulose, irregular in thickness in cross section, up to 3(-5) mm wide surface: greenish yellow, shiny, irregularly inflated, sorediate soredia: granular, subcorticate, 0.4-0.5 mm in diam, in terminal or submarginal, labriform or developed in terminal helmet-shaped soralia pseudocyphellae: common, ellipsoid, occasional, laminal, +depressed cortex: thin; chondroid strands: common, continuous, smooth Apothecia: not observed Pycnidia: not observed Spot tests: cortex K-, C-, KC+ yellow, P-; medulla K-, C-, KC-, P- Secondary metabolites: cortex with usnic acid (major); medulla with evernic (major) acid and obtusatic acid (major). Substrate and ecology: on rock (for Sonoran specimens), elsewhere also on bark World distribution: cosmopolitan Sonoran distribution: Arizona, southern California, and Chihuahua, Notes: Ramalina pollinaria is very variable in morphology. Thalli growing on rocks usually form a extending sward with simple or sparingly branched laciniae with terminal helmet-shaped or labriform soralia that gives secondarily fistulose appearance. When growing on bark, it usually has a delimited holdfast and is dichotomously or irregularly branched. Ramalina pollinaria might be confused with R. obtusata or R. baltica, neither of which occurs in the Greater Sonoran region, as they often have similar inflated or labriform soralia and produces evernic and obtusatic acids. However, R. obtusata differs in having fistulose laciniae and R. baltica differs in having delimited holdfasts and dull green branches without striation of chondroid strands. In addition, the latter two species are basically corticolous species whereas R. pollinaria grows mainly on rock. Specimens previously determined as R. obtusata have redetermined as R. pollinaria. Ramalina pollinaria also resembles R. chihuahuana that differs in having marginal soralia and in producing divaricatic acid.