Observation 203674: Xanthoparmelia mexicana (Gyelnik) Hale
When: 2015-05-02
(35.4631° -120.6753° 277m)
Who: J-Dar
No herbarium specimen

Notes:
Sandstone boulder used as a parking block.

Foliose, light yellow-green lichen, roundish shape overall, isidia abundant, without soredia or apothecia. Thallus upper cortex dull to shiny at lobe tips, with blackish margins. Thallus underside pale to tan, brown at lobe tips, rhizines patchy but dense, black, simple. Medulla white. Thallus K-, C-, KC-, medulla K+Y turning dark red (salazinic acid).

Same rock as X. lineola, observation 203673.

Proposed Names

76% (2)
Eye3 Eyes3
Used references: Nash Sonoran V.2
Based on microscopic features: Isidiate
Based on chemical features: Medulla K+Y turning dark red

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Eye3 = Observer’s choice
Eyes3 = Current consensus

Comments

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No need to edit, you were perfectly clear
By: Jason Hollinger (jason)
2015-05-03 07:45:43 PDT (-0700)

I just wanted to reinforce what the Sonoran Flora says about the K test. Norstictic acid often gives a similar reaction to salazinic acid, but in this group it seems reliably never to turn dark red. Just like the key says! :)

I, too, found mexicana to be very common on the coast.

Yes, very quick dark red K test
By: J-Dar
2015-05-03 07:34:04 PDT (-0700)

I should probably edit that description above, it is definitely very quickly dark red, not yellow that turns red slowly. Thanks for the 400x tip, now that botany season is just about done here (very early and quick bloom season!) I really am going to get that compound scope!

Agreed
By: Jason Hollinger (jason)
2015-05-03 07:25:05 PDT (-0700)

Although it’s not foolproof, if you’re getting a relatively quick, dark red K test, then this is almost certainly salazinic. The other species with norstictic and/or stictic complex all react very slowly red at most, usually just orangish.

The foolproof test, for future reference :), is to apply K to a section at 400x and look for norstictic acid crystals — long needle-shaped red crystals. They usually take a minute or two to form if the concentration is weak. It helps to mount the section (thallus, apothecia, anything) in as little water as possible, and not to disturb the section after applying K to the side of the coverslip.

Created: 2015-05-02 18:49:54 PDT (-0700)
Last modified: 2015-05-03 07:25:25 PDT (-0700)
Viewed: 31 times, last viewed: 2016-05-14 20:09:49 PDT (-0700)
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