Observation 4405: Agaricus L.

When: 2007-09-17

Collection location: Fort Collins, Colorado, USA [Click for map]

Who: Dixie Smith (dixiesmith)

No specimen available

“Mushrooms Demystified”


Proposed Names

-53% (3)
Recognized by sight
53% (3)
Recognized by sight: Agaricus, but unknown, not A. campestris since there is yellow stains in the stipe.

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= Observer’s choice
= Current consensus


Add Comment
Bright pink gills
By: Nathan Wilson (nathan)
2007-10-20 15:40:54 CDT (-0400)

Dix Simth wrote in email:

“The bright pink gills are my primary reason for sticking with A. campestris. I know of nothing in the literature that suggests that gills of A. arvensis ever have that distinctive color. A. arvensis growing in the same area and time had white gills.

Spore prints are not very helpful. Mycologists have not adopted standardized color charts or terms. To me, they appeared to be dark brown."

Further discussion
By: Nathan Wilson (nathan)
2007-10-20 12:03:41 CDT (-0400)

In email, Dix Smith wrote:

“No stains were used for testing.”

I attempted to respond with:

“I just realized that my comment wasn’t completely clear. By ‘staining reaction’, I actually meant was the color just the result of cutting or bruising the stem. It sounds like it was. Given that, it cannot be Agaricus campestris.”

But was blocked by an irritating spam filter.

Dix Smith replied to my short spam filter version of the above with:

“I disagree respectfully. You’re the webmaster, remove the photo and ID if it offends you. I will not be offended.

I’m fascinated by your Wyoming experience. Was Hank Northern and Bill Solheim still around when you were at UW?"

To which I attempted to respond:

“It in no way offends me. The point of the site is to create discussion and allow for disagreement. I’d just be curious to know why we disagree. You haven’t given me any reason to support your conclusion that it is Agaricus campestris. In particular the yellow mark in the flesh needs to be explained. It also has a smoother, more pigmented cap than typical Agaricus campestris. It also lacks the sterile margin around the edge of the cap that is typical of A. campestris. On the other hand, the bright pink gills and the solid stipe are typical of A. campestris and point away from the Arvensis group. The real tests would be odor (sweet/almond for Arvensis, just ‘mushroomy’ for A. campestris) and the color it changes when KOH is applied to the cap (yellow for the Arvensis group and unchanging for A. campestris).

I’m not sure what you mean by my Wyoming experience. I’ve never been there. There are several observations on the site that others have made."

but was again blocked by the spam filter. Consequently, I moved the entire conversation to here. I don’t have the time to waste on interactive spam filters.

Is that a yellow stain?
By: Nathan Wilson (nathan)
2007-10-18 18:34:03 CDT (-0400)

Towards the bottom of what remains of the stipe there’s a yellow area. Do you know if that’s a staining reaction, the result of applying a chemical or from some other source? If it’s a staining reaction, that eliminates A. campestris since it never stains.