Observation 163084: Amanita magniverrucata Thiers & Ammirati
When: 2014-04-05
No herbarium specimen

Notes: It was found in an area with a lot of oak and bay laurel. It was about 7 inches in height, and the cap diameter was approx. 4 inches.

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They do look like A. magniverrucata
By: Ron Pastorino (Ronpast)
2014-04-08 16:49:37 PDT (-0700)

to me also.
I’ve added two observations of material that look the same but found in different areas of the Bay Area.
The question of spore measurments is again risen with regard to my consistency, especially with Amanitas.

remember Michael…
By: Debbie Viess (amanitarita)
2014-04-08 16:44:38 PDT (-0700)

the info in MDM is twenty five years out of date! What might have been believed then is in some cases no longer true.

We live, we learn, god willing.

Your mushroom is typical for our Amanita magniverrucata: prominent warts and a rooting stipe with lots of remaining volvar material in rings. They can get HUGE.

You don’t need a scope to tell the species: just a fingernail. Try and scrape those warts off of the cap with your nail … an easy thing to do in most other warted amanita species, including most other lepidella species, but not in the case of magniverrucata.

One more comment on sample size.
By: R. E. Tulloss (ret)
2014-04-08 15:00:09 PDT (-0700)

Assuming that spores are measured using a rigorously followed methodology, then you need about 450 – 500 spores before the averages and ranges really stabilize. This is both an observation (by an old guy obsessed with measuring spores for hundreds of species for 35 years) and by the statistics involved in the level of certainty produced by sample sizes.

Very best,


By: Christian (Christian Schwarz)
2014-04-08 14:45:16 PDT (-0700)

for that very informative comment, Rod.

I should’ve know you would have de facto included sample size (and number of fruitbodies, and number of locations).

I admire your prudence of not betting on this one, even if (being that I am historically imprudent) I would still call it A. magniverrucata.

I agree that the volva/cap inseparability is (at least often) macroscopically visible.
By: R. E. Tulloss (ret)
2014-04-08 14:35:05 PDT (-0700)

The volval warts in the photographs (although the images are not clear at higher magnifications) seem to be dragging material over the cap surface (note the striated surface between warts), which may mean that the cap expansion is stressing the cap surface that is not separated from the wart bases by gelatinization. If that interpretation is correct, then this could be magniverrucata.

Larger spores are often found in immature amanitas because when sporulation begins, many amanitas produce 1-, 2-, and 3-spored basidia before they settle down to making 4 spores per basidium. It’s as though each fruiting body has to practice while it “grows up.” Spores from a 2-spored basidium have about twice the volume of a spore from a 4-spored basidium. Roughly speaking this means that the length of such a spore and the diameter of such a spore must be multiplied by about the cube root of 2. I have observed this many times; and the the observation is built into the “Short list from spores” page of the WAO website as one of the tricks for adjusting spore size so that an observer’s spore measurements can be matched to the spore data that’s in the site’s data bases.

I used to think that a few species had spores or basidia that were different in different seasons; however, almost every one of those cases has involved what now appear to be possible cryptic taxa that were “revealed” by genetic studies.

I’d be more inclined to interpret variation in spore size in magniverrucata to be (1) spores from immature lamellae or (2) evidence of the presence of one or more cryptic taxa. I started to say I’d bet on number 1; then I thought of how many potential cryptic taxa we’re seeing in some sections of Amanita. So, as a teaching gimmick, this time I won’t bet.

With regard to sample size of measured spores: You can always tell my sample sizes precisely. In this case, the spore data is preceded by “[240/11/9].” This means that the data is based on 240 individual spore measurements from 11 fruiting bodies from 9 different collections. When I can give at least some of this data for the measurements of other authors, I provide it using the same “encoding.”

Very best,


I’ve heard that
By: Christian (Christian Schwarz)
2014-04-08 11:56:14 PDT (-0700)

and observed it in the field – at least I think it’s macroscopically visible.
A. magniverrucata doesn’t seem to show the smooth skin between warts that things like A. smithiana show in age.

The mushrooms in this observation appear to show that feature, yes?

There’s a lot of interesting microscopic anatomy in A. magniverrucata.
By: R. E. Tulloss (ret)
2014-04-08 11:51:00 PDT (-0700)

Take at look at the technical tab on this page:


Especially notice that there the volva and the flesh of the cap are not separated by a skin (pileipellis) in magniverrucata. In Amanita the cap skin is almost always a layer of hyphae that is tightly packed vertically. In most cases this is separated from the base of the volval warts by having the uppermost hyphae gelatinize (break up into small fragments and release contents) to lubricate the separation of volva and cap.

The giant warts of magniverrucata have an upper part made of the vertically aligned cells of the volva; however, because there is no cap skin, the cap flesh remains bound to the bottom of the warts and the cracking of the volva (into warts) extends down into the cap’s flesh (in which the larger inflated cells are roughly radially arranged). Hence the warts appear even larger than they would be if the volva alone were their source.

The microscopic details of these tissues are described on the above web page.

Very best,

Rod Tulloss

The name A. cokeri was misapplied in California (e.g., in Harry Thiers book).
By: R. E. Tulloss (ret)
2014-04-08 11:39:25 PDT (-0700)

I would be glad to look at any material that was determined to be cokeri from California. It has rather distinctive, large spores. Sequences for several genes have been posted in GenBank. I’d be interested in seeing what could be learned from the material that Michael and Ron have posted or will post on MO.

Very best,


Re: These seem to be…
By: Michael Wedgley (caliguy83)
2014-04-08 09:09:25 PDT (-0700)

I was really excited when I found it. It was a beautiful mushroom. As I read under A. Magniverrucata in David Arora’s MD, it really sounds to me to be A. Cokeri, and he says it occurs in California.

Re: These seem to be…
By: Michael Wedgley (caliguy83)
2014-04-08 09:09:22 PDT (-0700)

I was really excited when I found it. It was a beautiful mushroom. As I read under A. Magniverrucata in David Arora’s MD, it really sounds to me to be A. Cokeri, and he says it occurs in California.

Re: A very interesting species…
By: Michael Wedgley (caliguy83)
2014-04-08 09:03:36 PDT (-0700)

I have not dried material. I have yet to try to identify by use of microscope. This is only my second season of hunting, and this year was a tough one so my experience is minimal. I would like to start broadening my scope though. Do you have any suggestions on what I should do in the future?

These seem to be prolific in the S. F Bay Area
By: Ron Pastorino (Ronpast)
2014-04-08 08:09:20 PDT (-0700)

right now.
I have a couple that I’ll be posting later.
I’ve been wanting to call them A. magniverrucata but…

A very interesting species,Michael.
By: R. E. Tulloss (ret)
2014-04-08 05:45:58 PDT (-0700)

But it’s probably not Amanita cokeri, which is strictly an eastern species so far as is known.

There are some similarities between your material and the eastern species. I woulld very much like to know more about your material.



I see that you did not retain a herbarium specimen. Do you ever dry material for study?

Very best,

Rod Tulloss

Created: 2014-04-07 20:51:50 PDT (-0700)
Last modified: 2014-04-09 08:54:19 PDT (-0700)
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