Observation 182112: Agaricus xanthodermus Genev.
When: 2014-10-08
(38.5641° -121.431° 16m)
No herbarium specimen

Notes: Dozens of specimens found in large fairy ring under redwoods in the Sacramento State arboretum.
KOH: Yellow on gills, cap & other tissue.
NH3: Orange on cap. NR on gills & flesh.
Hemispheric cap smooth to lightly scaly with age.
Average cap had a 5cm diameter, 2.5cm height. Gray/white and tan coloration, with patches of yellow on cap margins.
Stalk 11mm thick, with 4mm central “pith” and subtle <1 mm central hole.
Immature specimens had a membranous veil. the central portion of the veil was smooth, the remaining 12mm portion was scaly and rough. Mature specimens had a mostly shriveled, small volva. Gill coloration was darker, almost buff. Gills were free and crowded, but short — only 20% of cap height was gills, the remainder was normal fruiting body tissue.


Fairy ring.
Fruiting bodies. Note yellow bruising on margins.
Spores at 1000×.
Chocolate brown spore print.

Proposed Names

50% (1)
Eye3 Eyes3
Recognized by sight: Yellow bruising on cap margins.
Used references: Arora, David: Mushrooms Demystified. Mykoweb.com
Based on microscopic features: Elliptical, smooth spores. ~4µm x 6µm.
Based on chemical features: KOH: Strong yellow reaction on gills & cap. NH3: Orange staining on cap. NR to IKI and FE2SO4.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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Created: 2014-10-10 00:40:58 CEST (+0200)
Last modified: 2014-10-13 20:34:35 CEST (+0200)
Viewed: 30 times, last viewed: 2015-11-11 17:40:40 CET (+0100)
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