Observation 56905: Agaricus augustus Fr.

When: 2010-10-27

Collection location: Foster City, California, USA [Click for map]

Who: Tom (LanLord)

No specimen available

Not sure if this was brunneum or Rachodes as it was the only one and I didn’t pick it to look at the base of the stipe.



Proposed Names

-55% (4)
Recognized by sight
39% (7)
Recognized by sight
6% (3)
Recognized by sight: Cap, gills, stipe. Wondering if brown stipe coloration may be spore drop, which would eliminate Chlorophyllum and Agaricus.
84% (3)
Recognized by sight

Please login to propose your own names and vote on existing names.

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
I think Tom’s new photos
By: Christian (Christian Schwarz)
2010-10-29 12:41:16 EDT (-0400)

confirms A. augustus.

The veil is there. The colors are right (the specimen at left in my obs wasn’t parasitized at all, that is the partial veil stretched over the gills).

Probably Agaricus
By: Tom (LanLord)
2010-10-29 11:56:18 EDT (-0400)

I took a morning bike ride back to the park where I found these on Wednesday.

The remains were pretty well worn, but I think it shows enough to determine that the gills are brown. I am assuming they were brown from spores rather than age/spoilage as they weren’t yet gooey.

I added a few pics to the observation.

There was also remnants of significant amounts of partial veil which remained attached to the cap margin as well as one area where it appeared to still be attached to both cap margin and stipe.

This has been an interesting one for me, taught me to not make macroscopic assumptions. Thanks all for your input.

Here is….
By: Tim Sage (NMNR)
2010-10-29 11:03:21 EDT (-0400)
If this is not an Agaricus…
By: Tim Sage (NMNR)
2010-10-29 10:57:30 EDT (-0400)

I will eat my cat. Those colors and scales scream Agaricus to me, but I am no expert.

Hopefully Tom will be able to go back and solve this for us with a gill shot!

Appreciate the photo, Christian.
By: Daniel B. Wheeler (Tuberale)
2010-10-29 10:23:33 EDT (-0400)

I do see areas of brown/tan on the stipe in your link. However the stipe in this observation does not match your linked observation. Also, it looks like the specimen on the left in your linked observation may be parasitized, which could dramatically affect colors.

Agaricus augustus often (but not always) has a thick felty annulus. In this observation it is curious by its absence and almost no annulus remains on the stipe.

Check this one
By: Christian (Christian Schwarz)
2010-10-29 10:02:01 EDT (-0400)

I just posted a photo of A. augustus that shows a cluster of rain beaten specimens, with cap going all the way to orange-brown! Hopefully this will help folks see the connection between this obs and A. augustus


What other species fits as well with all these clues? It is fairly large, growing in mulchy, cultivated soil, cap color golden brown to yellowish with apressed scales, stipe slightly scurfy and relatively robust, appendiculate cap margin, early season fruiting… Despite the lack of gill description, I feel pretty confident that this is A. augustus

Also, brown spore drop on the stipe would not eliminate Agaricus – they have chocolate brown spores, and of course a light dusting on the stipe will appear lighter than a full spore print.

Not umbonate.
By: Daniel B. Wheeler (Tuberale)
2010-10-29 09:54:42 EDT (-0400)

Thanks for correcting me, Christian. You are correct.

Have just checked out several pages worth of A. augustus posted here, and not found a single specimen to match the coloration of cap, stipe, or yellow-brown scurffy stipe of this observation. While I suppose it could be an Agaricus species unknown to me. It cannot be A. augustus IMO.

The light brown coloration of the entire stipe suggests it might be a completely mature Chlorophyllum. C. brunneum in my experience never has this dark a brown until after handling, though. And the discoloration is almost always local, usually matching the fingers or where plucked. This stipe looks untouched. Is there another option within the Chlorophyllum family that might match this observation?

By: Tom (LanLord)
2010-10-28 22:12:30 EDT (-0400)

The center portion was depressed. The part that looks like one large patch was depressed with the edges pulled up from the rest of the cap. That was one of the features which lead me to Chlorophyllum.

I haven’t had a chance to go back, hopefully tomorrow.

This obs is not umbonate
By: Christian (Christian Schwarz)
2010-10-28 21:07:26 EDT (-0400)

but neither is Agaricus typically umbonate. Umbonate doesn’t mean ‘umbrella-like’, in the sense that umbrellas are convex. An umbo refers to a raised, central ‘knob’ or ‘hump’ on the cap.

That said, Agaricus (especially these larger, flat-topped species) can have depressed centers in age (and especially when a bit beaten down by rain).

Another clue: check out the photo from the side – there are appendiculate partial veil remnants hanging off the edge of the cap – this feature plus the golden colors and slightly scruffy stipe make me think of A. augustus.

Another feature of this observation
By: Daniel B. Wheeler (Tuberale)
2010-10-28 20:54:17 EDT (-0400)

The center of the cap appears (to me) depressed. In Agaricus and Tricholoma, it would typically be umbonate (umbrella-like). Tom, does this observation have/had a depressed center?

Difference in scale types
By: Christian (Christian Schwarz)
2010-10-28 12:51:02 EDT (-0400)

In Agaricus (this observation), the scales are almost always appressed clumps of fibers (appressed means held close to the surface of the cap).

In Chlorophyllum, this can also be present, but then the fibers terminate in a discrete patch of the original cap covering, like a flat flake or patch of darker colored tissue.

Compare to Obs. 56763
By: Daniel B. Wheeler (Tuberale)
2010-10-28 12:44:57 EDT (-0400)

Your observation does not have the same smooth stipe (stem), which makes Chlorophyllum unlikely. I can’t place the kind of scurffy stipe your photos show. Just below the annulus. Compare to obs. 56763 which is a Chlorophyllum.

Brunneum vs. rachoides
By: Daniel B. Wheeler (Tuberale)
2010-10-28 12:28:16 EDT (-0400)

Need to pick it. If brunneum, the stipe especially near the base will bruise brown almost immediately upon handling. Rachoides doesn’t.

Really need photo of gills.
By: Daniel B. Wheeler (Tuberale)
2010-10-28 12:26:34 EDT (-0400)

Pretty certain this is not Chlorophyllum. Nor Agaricus. But certainly in the Agaricaceae. I suspect Tricholoma, but until I can see some gills even that has to be just a guess.

By: caphillkid
2010-10-27 18:22:04 EDT (-0400)

It’s possible, but the stipe doesn’t seem smooth like in Chlorophyllum rhacodes. I’m not familiar with brunneum, but I believe its stipe is also smooth.

I was pretty certain …
By: Tom (LanLord)
2010-10-27 18:10:01 EDT (-0400)

that these were Chlorophyllum, around here they turn somewhat coffee coloured when they age. However, I didn’t get a shot of the gills to verify that they are white/light so I can’t be sure they aren’t Agaricus.

By: caphillkid
2010-10-27 15:13:17 EDT (-0400)
the stipe looks like it was rather cottony in the early stages of development, which would point more towards Agaricus.
By: caphillkid
2010-10-27 14:57:35 EDT (-0400)
I agree with Tim. I’ve never seen Chlorophyllum with such uniform dark brown colors before.
Looks more like
By: Tim Sage (NMNR)
2010-10-27 14:56:31 EDT (-0400)

Agaricus sp. to me with those colors and less prominent scales.

Created: 2010-10-27 14:54:46 EDT (-0400)
Last modified: 2010-10-29 13:28:34 EDT (-0400)
Viewed: 213 times, last viewed: 2018-07-16 13:25:34 EDT (-0400)
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