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51.
Umbilicaria torrefacta [of cataracts?]. |
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Several
small species of Umbilicaria are frequent on shaded granite
boulders in the foothills canyons. They are dark brown or black,
with circular or angular convex apothecia crisscrossed with deep
furrows. This species has horizontal plates (called
trabeculae) on the underside radiating from the central
umbilicus. No other species has these. |
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52.
Aspicilia caesiocinerea [blue-gray]. |
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One of the
most ubiquitous of lichens on granite rocks, covering large areas
and giving the rock a gray color. The black apothecia are sunk in
the thallus, giving the impression of molar teeth with black
cavities. Very variable in thickness and lumpiness. Several species
occur, requiring chemical and microscopic analysis for
identification. |
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