the stalwart …

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… a hardy birch at 9,000 feet in the Ashley National Forest in northwest Utah.

whirlpool …

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… on the underside of bark from a birch.

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… on the underside of bark from a dead birch.

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… of the bark of an old, crumbling birch tree. This is an area about two inches across.

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… in a paper birch’s bark.

27969657934_b3f29b3842_c … a yellow birch (so my botanical Ph.D. pal tells me) off Route 8A in Heath, Massachusetts.