| General Appearance: Pale gray to greenish-gray patches composed
of flat, overlapping branches and lobes; the patches commonly 2-7
cm (1-3 in) across, but often smaller on twigs.
Thallus: Foliose, consisting of flat, overlapping branches which are tightly attached to the bark; the branches 2-5 mm (1/8-1/4 in) wide. Upper surface pale gray or greenish gray when dry; greenish-gray when wet; smooth with raised whitish ridge-like folds (Fig. A) (use a hand lens. ) Lower surface dark brown to blackish, covered with blackish rhizines over the entire lower side. Apothecia: Rare. Soredia: Developing at margins and on raised folds on upper surface (Fig. B) (Use a hand lens. ) Isidia: Lacking. Comments: The broken network of white ridges on the upper surface of the lobes distinguishes this species from other species of gray, foliose lichens. Parmelia sulcata is common and widespread. It is relatively tolerant of pollution, so it is found in all but the dirtiest areas. Nevertheless, studies by LeBlanc and Rao (1973) indicate that amounts of sulfur dioxide ranging from 0.01 to 0.03 parts per million in the atmosphere result in serious damage or death in this species. |
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