Observation 27596: Agaricus semotus Fr.

When: 2009-10-26

Collection location: Novato, California, USA [Click for map]

Who: John Kirkpatrick (natashadak)

No specimen available

grassy habitat; v dark brown spore print; pileus ~4cm, ~matted tomentose; no annulus

Proposed Names

29% (2)
Recognized by sight
51% (3)
Recognized by sight

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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trees and almonds in the distance
By: John Kirkpatrick (natashadak)
2009-11-03 01:22:19 -05 (-0500)

The nearest trees (a bay and buckeye) were at least 10 meters away. I’ve added a shot of the site – the stick is marking another find; the specimen in question was on the other side of the pitch. There MAY have been an almond scent (I initially thought so), but my nose is really not to be trusted. If there was staining it was v subtle.

I included a spore shot hoping it might help narrow possibilities; I was not confident about the genus because there was no apparent annulus. As noted, the photo was second rate …

By: Dimitar Bojantchev (dimitar)
2009-11-01 11:07:28 -05 (-0500)

>I’d call them subglobose and say Q is between 1.1 and 1.4, close to 1.2. Greater precision measurements of Q aren’t really useful anyway

Ohh, I see. Thank you. Sorry for any hurt feelings I might have caused. You are perfectly free to feel good and do things your way.

By: Paul Derbyshire (Twizzler)
2009-11-01 11:00:07 -05 (-0500)

We also have an opportunity here to contribute to a more collegial environment. Calling one another names, accusing people of “noise pollution”, and similarly hostile behavior will not accomplish such a goal. I notice a slow but steady degradation of civility on this site of late, with another recent obs (I think of Psilocybes) having had several rude comments (much worse than yours) and now this.

This site is about mushrooms, not us or our opinions of one another. Please try to keep that in mind and avoid making remarks that insult, belittle, goad, or otherwise attack people personally.

As for the spore boundaries, they’re clear enough to gauge Q, though not to measure the actual size of the spores. In this instance they’re clearly neither globose nor cylindrical, nor in the longer part of ellipsoid. I’d call them subglobose and say Q is between 1.1 and 1.4, close to 1.2. Greater precision measurements of Q aren’t really useful anyway; the natural variability of Q in most species is as large as the uncertainty from this photo being fuzzy.

Ok, if you insist, but…
By: Dimitar Bojantchev (dimitar)
2009-11-01 10:38:50 -05 (-0500)

Paul, justification for sloppiness gets me a bit intense. See, estimated and measured are different things. You cannot do anything reliably with the precision required for the purposes of mushroom identification with such a spore shot — the spore boundaries are not clear at all. The spore shapes take a different life in medium. Yes, my tone reflected slight irritation when a reasonably important message to a starter is being diluted by noise. See, we have an opportunity to do some teaching here too and contribute to a more studious environment.

Q = 1.2 or so here (subglobose to mildly ellipsoidal)
By: Paul Derbyshire (Twizzler)
2009-11-01 09:52:00 -05 (-0500)

Q (aspect ratio) can be estimated reasonably well from a photo like this one. You’re right that the exact size cannot.

I don’t think there was any need for the unpleasant tone, by the way.

Wow, what a bright idea…
By: Dimitar Bojantchev (dimitar)
2009-11-01 09:09:30 -05 (-0500)

That would have never crossed my mind…

But seriously, Paul you’ve been around long enough to know better — from such low resolution, you cannot do so RELIABLY. As I said earlier, and I speak from some experience — you need max optical resolution to do this. That’s true to most all species, but especially so for Agaricus — these spores are on the smaller side 5-8 by 4-6µ, typically… It is very useful to know RELIABLY whether the average width is 4.5µ, or 5.4µ. Of course the spores can very somewhat between populations, maturity, etc (don’t wanna get into a long Agaricus discussion), but the part that depends on us needs to be impeccable. Do you have any other suggestions?

Have fun,

You can measure the Q of spores from any photo of them.
By: Paul Derbyshire (Twizzler)
2009-11-01 08:49:49 -05 (-0500)
A. semotus
By: Dimitar Bojantchev (dimitar)
2009-10-31 22:45:12 -05 (-0500)

These do look like Agaricus semotus. Irene is right on. What you should have noted is the odor, which should be slightly to more almondish. And a degree of yellowing upon bruising. Where there Oaks around? Also, John, good job ont he spore shot — I used to do them the same in my early days, but it is utterly useless unless you specify exact spore sizes, measured under immersion oil at max magnification. The spores of Agaricus are not an easy factor to interpret.

By: Shane Marsh (Mushane)
2009-10-31 13:07:21 -05 (-0500)

any trees nearby? oak maybe?

odor? staining? annulus is there, just ephemeral.
By: Debbie Viess (amanitarita)
2009-10-31 12:08:36 -05 (-0500)

Created: 2009-10-31 03:04:06 -05 (-0500)
Last modified: 2009-10-31 03:04:06 -05 (-0500)
Viewed: 127 times, last viewed: 2017-06-06 04:46:12 -05 (-0500)
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