Observation 80922: Usnea strigosa group
When: 2011-10-28
Who: vjp
No herbarium specimen

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Recognized by sight
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Eye3 = Observer’s choice
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I lied: chemistry and/or microscopy
By: Jason Hollinger (jason)
2011-11-04 00:37:48 CDT (-0400)

KOH test is most useful in this case. Scratch or slice it open to expose the white or pinkish cottony medulla, and apply a drop of strong KOH:

U. subfusca – salazinic acid = K+ yellow turning rapidly really deep blood or brick red
U. endochrysea – nothing or norstictic acid = K+ yellow turning orange-red or bright red
U. strigosa – various lichen acids, including sometimes even norstictic acid, unfortunately, but positive C (straight bleach) or UV (350 nm, in a very dark room) would rule out endochrysea

Also a white medulla will rule out endochrysea. But in the pathological (and common) case where you see pink medulla and K+ red, you have no alternative but to dissect an apothecium and measure spore length. U. strigosa is < 9 µm, U. endochrysea is > 9 µm, with almost no overlap (just measure a number and eyeball the average to be sure). The big “eyes” are apothecia. Even just scraping it with a needle and squashing the scrapings in a water mount can be sufficient.

By: vjp
2011-11-03 21:43:29 CDT (-0400)

the responses

New to lichen – what kind of chemistry are required?

I agree with zaca
By: Jason Hollinger (jason)
2011-10-28 18:44:46 CDT (-0400)

Fortunately, I happen to be very familiar with the flora in that area. Your only real choices are U. strigosa, U. endochrysea (usually requires chemistry to distinguish) and U. subfusca (mostly higher elevations, not piedmont, is discolored black near the base where it attaches to the bark).

I would just call it “Usnea strigosa group”. Any lichenologist will know exactly what you mean by that.

Usnea sp.
By: zaca
2011-10-28 16:08:37 CDT (-0400)

Without details like chemistry and/or microscopy maybe U. strigosa group.

Created: 2011-10-28 15:12:28 CDT (-0400)
Last modified: 2011-10-28 18:45:19 CDT (-0400)
Viewed: 66 times, last viewed: 2016-10-27 08:38:07 CDT (-0400)
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