Observation 47844: Amanita pachysperma G.F. Atk.
When: 2010-06-26
Herbarium specimen reported

Notes: Cap diameter about 2 cm. Annulus present. I am unable to determine if the stipe base has a bulb… looks to me more like a volval sac that’s partially clinging to the base. Amanita subgroup? Annulus, volval sac, striate cap all fit in with caesarea… but I don’t recall ever seeing any pics/descriptions of a Caesar with this color scheme. Spore print was very light, so i was unable to determine if amyloid. Spores at 400x in Meltzer’s.

Border of hardwood forest nearby an oak.

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Eye3 = Observer’s choice
Eyes3 = Current consensus

Comments

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A. virginiana min spore size is 11.5.
By: Dave W (Dave W)
2010-06-30 19:39:16 PDT (-0700)

That’s why I favor pachysperma. Though I do wonder about the accuracy in measurement for my old hand me down 400x scope.

Specimen is dried, stored, and referenced via MO 47844.

Light spore print could mean sporulation was not well under way.
By: R. E. Tulloss (ret)
2010-06-30 17:47:57 PDT (-0700)

Maybe larger spores are on the part of a gill near to the stem?

Very best,

Rod

Posted spore pic does not provide a closeup,
By: Dave W (Dave W)
2010-06-30 04:42:44 PDT (-0700)

but this may just be a temporary problem with my office computer. Some of the spores do appear to be over 10 mu long, and most are at least around 10 mu. Otherwise, this specimen matches well with the description on the AS website.

Material is currently drying for preservation.

From everything you’ve said,…
By: R. E. Tulloss (ret)
2010-06-29 19:46:36 PDT (-0700)

I think that you may have Amanita virginiana (if the cap center is distinctly brownish) or Amanita pachysperma (if the cap center is a shade of gray with no brown tint.

In either case, at least 30% of the basidia are probably 2-spored. The spores should be rather large for amanitas (because many have double the normal spore volume due to originating on 2-spored basidia.

Both taxa of some coverage on the Amanita Studies site. Both are species in section Caesareae. Both taxa are associated with oak. Neither taxa is particularly rare; however, they are rarely collected (probably because of their size).

If my guess is correct, this is a neat find.

Congratulations on your analysis of the material.

Very best,

Rod

Created: 2010-06-29 17:11:58 PDT (-0700)
Last modified: 2010-07-26 22:41:54 PDT (-0700)
Viewed: 116 times, last viewed: 2017-02-04 08:07:59 PST (-0800)
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