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55. Lecidea
tessellata [mosaic, tiled]. |
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When well
developed, this lichen is unmistakable, its black, flat apothecia
on a level with the gray areoles, suggesting nothing less than a
mosaic pavement, hence its name. Very common on sandstone and
granitic rocks. In areas where the lichen is scoured by wind-blown
sand or ice, the softer areoles are often eroded away, leaving a
"ghost thallus" and the more dense and resistant apothecia standing
alone. |
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56.
Parmelia saxatilis [of rocks]. |
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A gray
foliose lichen with isidia covering the upper surface; the
underside is black, and the rhizines are simple or only forked. It
occurs in the same places as P. sulcata, but is not quite as
common. Neither species ever has apothecia. |
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