Observation 52259: Myelochroa aurulenta (Tuck.) Elix & Hale

When: 2010-09-07

Collection location: Sewanee, Franklin Co., Tennessee, USA [Click for map]

Who: Chris Parrish (kitparrish)

Specimen available

Axillary setae occasionally present, but cilia almost entirely lacking around outer lobe margins.

Tubercles developing along ridges and densely clustered in the center of the thallus, degenerating into granular soredia, and sometimes even leaving a perforated thallus, with exposed gaping soralia.

Medulla mostly very pale yellow, but sometimes white, and always so pale that one must look several times to be sure that it really is pale yellow rather than white.

Lower cortex jet black under most of the thallus, pale creamy tan under outer lobes.

Rhizines jet black, abundant, quite long, mostly simple, occasionally somewhat furcate at the tips, but shorter, more sparse, and lighter-colored under outer lobes.

Cortex: K+ yellow, C-, KC+ pale yellow
Medulla: K+ yellow, C-, KC+ deeper yellow (immediately), P+ deep yellow (over 1 or 2 minutes)

Identification: Yellowish medulla, jet black lower cortex, simple rhizines, axillary bristles, “coarsely granular soredia in irregular soralia, developing from a breakdown of the cortex or burst pustules” (Brodo, 2001, p.447), and chemistry suggest Myelochroa aurulenta, but Jason points out that degenerating tubercular soralia are also found in Hypotrachyna, We are still working on this one!

Update on the chemistry of Myelochroa aurulenta and similar species:
Dey (1978, pp.62-63) reports the chemistry of Myelochroa aurulenta (under the older name Parmelia aurulenta) as “Cortex K+ yellow; medulla K+ yellow, C+ yellow, PD + yellow,” and goes on to say “When testing unpigmented portions of the medulla or specimens in which the yellow pigment is very diffuse, the spot reactions with the K, C and PD reagents will all be negative.” He continues with a thorough discussion of Appalachian lichens with laminal pustular soralia, and their comparative chemistries.

Dey, 1978, “Fruticose and Foliose Lichens of the High-Mountain Areas of the Southern Appalachians,” The Bryologist, Vol. 81, No. 1 (Spring, 1978), pp. 1-93

Lendemer and Harris, 2006, Hypotrachyna showmanii, A Misunderstood Species From Eastern North America, Opuscula Philolichenum, 3: 15-20. Contains a key to the pustulose species of Hypotrachyna and Parmelinopsis.

Ryan, notes on Myelochroa. Chemistry, distribution, and key to the species of Myelochroa.

Voucher specimen:
Tennessee, Franklin County, Sewanee, Alto Road, 07 Sep 2009, Chris Parrish 0172

Species Lists


apothecia destroyed by herbivore
axillary cilia, laminar tubercles degenerating into soralia, 20x
laminar tubercles degenerating into soralia, 40x
laminar tubercles degenerating into soralia, 40x

Proposed Names

-28% (1)
Recognized by sight
28% (1)
Eye3 Eyes3
Used references: Brodo, Sharnoff, and Sharnoff, 2001, pp.447-448

Please login to propose your own names and vote on existing names.

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Ha! I was no help!
By: Jason Hollinger (jason)
2010-09-07 18:19:19 PDT (-0700)

Blast, thought all those yellow-medulla species were UV+. Secalonic A (in other Myelochroa, yellow Physconia, etc.) is UV+y, but I guess… err, leucotylic acid?… is not. Good to know. Heh, are we writing these down anywhere?? :)

Don’t know why this species consistently fools me. Tricky devil.

Thanks for your help with this one, Jason!
By: Chris Parrish (kitparrish)
2010-09-07 18:03:09 PDT (-0700)

I immediately went for the UV flashlight in my lichen bag, but in the UV department this fellow seems to be a dud.

By: Jason Hollinger (jason)
2010-09-07 17:43:16 PDT (-0700)

Oh damn, you were right from the start — this must be Myelochroa aurulenta. I’d totally forgotten it also has those weird pustules. The chemistry and simple rhizines probably clinch it. I bet it has UV+ medulla, too?

Wow, fertile specimen! Nice one.

Created: 2010-09-07 17:25:01 PDT (-0700)
Last modified: 2010-09-08 06:32:05 PDT (-0700)
Viewed: 491 times, last viewed: 2018-07-15 12:55:22 PDT (-0700)
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