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43. Usnea
hirta [shaggy]. |
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This is a
small species of Usnea, usually found on the trunks of
Douglas-fir trees. The main branches are short and stiff, and the
entire thallus is studded with very short spinelike branchlets.
There are no soredia. If the lichen is moist, gently tugging on
each end of a branch will break the cortex, and reveal a stout
white cord (the innermost part of the medulla). This feature
separates Usnea from similar genera, such as
Alectoria and Ramalina. |
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44. Usnea
lapponica [of Lappland]. |
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Probably
the most common species, with a short, widely branched thallus of
which the branch tips erupt with patches of soredia. Species of
Usnea in the arid West require standing water in the tiny
crevices of bark, and their presence usually indicates a humid
microhabitat or the seasonal presence of a snow bank beneath the
tree. The species appear to be short lived, and after possibly five
years of growth, may suddenly disappear. |
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