Observation 115113: Myelochroa obsessa (Ach.) Elix & Hale
When: 2012-09-01
Herbarium specimen reported

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ID confirmed by Jim Bennett
By: Andrew Khitsun (Andrew)
2014-06-25 18:35:40 PDT (-0700)
It’s a funny one, too
By: Jason Hollinger (jason)
2012-11-01 17:12:25 PDT (-0700)

Because it looks completely different (to me) from Myelochroa aurulenta.

Good deal.
By: Andrew Khitsun (Andrew)
2012-11-01 17:06:40 PDT (-0700)

Since it’s a new species for me, no wonder I was stumped.

I think this confirms Myelochroa obsessa
By: Jason Hollinger (jason)
2012-10-31 22:49:30 PDT (-0700)

It has a complex cocktail of substances in the medulla: zeorin, galbinic acid, secalonic acid A, and “a trace of” salazinic acid. I’ve made notes of the spot tests on the medulla of four specimens, two from Alabama (thanks to Vitaly), two from the Smokies:

1. medulla white, K+ yellow turning bright red and persisting, C-, KC fading to yellow-orange and persisting
2. medulla yellowish, K+ yellow to orange in places
3. medulla orangish, K+ yellow or reddish
4. medulla yellowish, K+ yellow

Furthermore, yours looks exactly like some of my photos: lobe tips are shaped exactly the same. I think we can call it.

Did some chem tests
By: Andrew Khitsun (Andrew)
2012-10-31 18:20:08 PDT (-0700)

Thallus K+ something dark, C-. Medula K+ yellow turning red, C+ faint yellowish (maybe, unless I’m seeng things). Isidia not black-tipped, no cilia. Outer edges of lobes are dark as seen from above (“burnt”).
What the heck?

What about Myelochroa obsessa?
By: Jason Hollinger (jason)
2012-10-31 17:02:40 PDT (-0700)

Imshaugia should have pale underside (and isn’t often on rock). Parmelinopsis is a possibility, but doesn’t occur that far north(?) Medulla is pure white and K- in Parmelinopsis; faintly yellowish and faintly K+y KC+y in Myelochroa (variable amount of secalonic acid A). M. obsessa is also smaller, often very difficult to remove from the rock. Both it and Parmelinopsis usually have faint tiny cilia in the crooks of the lobes. If the medulla is C+, then definitely Parmelinopsis minarum (the one commonly on rock). Also check for black tips on the isidia, especially cilia budding from the tips of the isidia — that’s a characteristic of P. horrescens.

Can’t figure this one out
By: Andrew Khitsun (Andrew)
2012-10-31 16:49:33 PDT (-0700)

Is this some kind of Punctelia? The thallii are small – only an inch to an inch-and-half in diameter, isidiate. Lower surface black.

Created: 2012-10-31 16:44:09 PDT (-0700)
Last modified: 2015-12-27 18:28:12 PST (-0800)
Viewed: 32 times, last viewed: 2016-10-26 01:46:16 PDT (-0700)
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