Observation 103386: Agaricus crocodilinus Murrill
When: 2012-07-26
Herbarium specimen reported

Notes: This unidentified Agaricus was collected in sparsely irrigated grass, but otherwise very dry conditions. I’m assuming that the cap ornimentation is a result of the conditions, as opposed to a feature of the mushroom.


2nd specimen
2nd specimen
2nd specimen
Copyright © 2012 Debbie Viess
Copyright © 2012 Debbie Viess

Proposed Names

55% (4)
Recognized by sight
Based on microscopic features: if you bring me a slice, I will check the spores for ya. crocodilinus is easy to separate out by spore size.
45% (2)
Recognized by sight: looks like an Agaricus from the top…
Based on microscopic features: but chocolate brown spores are small and lumpy.
-31% (3)
Recognized by sight
55% (1)
Recognized by sight: cracked cap, growth in grass.
Based on microscopic features: spores larger than other CA AGaricus sp. ten spores measured, not too big, not too small, well-colored. 9 × 6, 9.5 × 7, 9 × 6.5, 9 × 6, 8 × 6, 9 × 6, 8.5 × 7, 9 × 6.5, 9 × 6.5, 9 × 7.
Based on chemical features: pleasant sweet odor.

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

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Send me a piece to check the spores.
By: Dimitar Bojantchev (dimitar)
2012-08-03 15:57:51 CDT (-0500)

We need reliable spore data. This seems like a typical garden variety Agaricus. I would like to check the spore size precisely.


Spore data rules, but
By: Mike McCurdy (lesmcurdy)
2012-08-03 15:36:26 CDT (-0500)

still, the stature of this mushroom is slight in all respects relative to the normal range for A. crocodilinus. The surface of the mushroom was too dry to elicit staining, but the context, still moist, did not stain.

from Rick Kerrigan (with permission):
By: Debbie Viess (amanitarita)
2012-08-03 12:51:00 CDT (-0500)

It’s most useful to determine size averages of at least 10 ‘ordinary’
spores, or the range of such averages. Largest and smallest are
absolute limits of the size range and will vary much more. A.
crocodilinus in North America has spores with size averages ranging 9.2-11.2 × 6.2-7.7 um. So yours is not excluded yet, but averaged measurements of 10 or more spores are needed.

We know of no other species here with spores so large. The relatives
of A. campestris, which can look similar, have spores that are, on average,

It’s OK to share this info if you wish.

Cheers — Rick"

Ok, kisses now…
By: Dimitar Bojantchev (dimitar)
2012-08-02 22:15:09 CDT (-0500)

on the cheeks… just that part “but i also do up to three preps per slide” is a bit unorthodox. Have fun!

we knew that the spores didn’t fit, we just couldn’t at first determine why…
By: Debbie Viess (amanitarita)
2012-08-02 15:39:27 CDT (-0500)

of course i wash my slides. but i also do up to three preps per slide. I did two on the one where I looked at the wrong prep in error. shit happens.

hello? of COURSE the lactarius slide was stained by Meltzers, and is done whenever one looks at members of the russulacea or amanita. Basic. Next you’ll be taking credit for discovering the Internet! :)

and again, do a more careful scrutiny before going off. I presented two micrographs on the addended post: one at 400x showing many spores and the micrometer; the second was at 1000x under oil immersion and w/out the micrometer. my camera tends to focus on the micrometer lines rather than the spore details, which is why I left it off the second shot. the first shot provided more spore variety.

but there is usually a bit of wheat in your posts, so i am willing to read through the chaff. for now. just tone down the superior tone, bro.
it is very unappealing and wholly unnecessary.

Better, but…
By: Dimitar Bojantchev (dimitar)
2012-08-02 15:09:08 CDT (-0500)

Ok, good, I am glad that we resolved that.

As far as sweet or nasty, I am half-kidding with my tone, but let’s play tough for a minute. It is deserved and there are key lessons to be learned about microscopy – again, if not well done it is not just useless, it is harmful!!

1) “we were all scratching our heads over the odd spores. “

When someone passes me Russulales for Agaricales (while scratching their whatever..) and that person has a pretense of being remotely close to mycology, I have to kid/joke a bit…

2) “Apparently, in wanting to save time/money”

Wash your slides. No money component, takes 20 seconds. Think about it — this time the error was dumb & dumber, but next time it may be far more subtle and confusing. It can be very harmful to data gathering — that’s how ghost species are created. The reputation of a clean worker and precise scholar that creates confidence in the data is key.

3) “altho the lactarius and the photo posted here WAS under immersion oil. guess that it is clear and impossible to see in a photo, eh DB?)”

Ok, my error, I see that it is in max magnification and it is not the immersion oil the problem, but the medium used for the slide. Debbie, for your Lactarius studies – there is no value to look at spores of Russulaceae without Melzer’s. We’ve covered that in my microscopy class many times.

The Agaricus spores are not in max magnification though – you can easily tell by the scales of the micrometer. I suggest that you never ever measure spores and present them as evidence until you do the extra 2 minutes to do it right – 100x and immersion oil. There are many important things that can be observed with a light microscope. For small spores species like the typical Agaricus this is critical.

Take it in stride.


Well, that was exciting, Okay then,
By: Mike McCurdy (lesmcurdy)
2012-08-02 14:40:43 CDT (-0500)

the odor was mild, mushroomy, and maybe a little sweet. Definitly not phenolic. The cracking shown in the Agrocybe photos is very similar.

your message is reasonable but your nasty tone all too familiar, DB…
By: Debbie Viess (amanitarita)
2012-08-02 14:24:03 CDT (-0500)

we were all scratching our heads over the odd spores.

I had planned on redoing the micro and I just did.

Indeed this is an Agaricus sp; the dessicata clearly shows free gills.

The spores are also completely agaricoid, but not cross-contaminated on the mushroom itself.

Apparently, in wanting to save time/money, i put my gill mount on a slide that already had a former lactarius prep. Over time, and with the application of Meltzers, those white gills had also turned chocolate brown. When i put it under the scope, i mistakenly looked at the first rather than the second prep. it was obvious after the fact because the actual first Agaricus prep had never been looked at under oil (altho the lactarius and the photo posted here WAS under immersion oil. guess that it is clear and impossible to see in a photo, eh DB?)

You can see both slide preps in the attached photos in the obsie that I just made, an addendum on this sighting here:


Mystery solved, at least insofar as this being an Agaricus with perfectly normal spores. Which Agaricus tho, still an open question. This cap was pure white, not with the darker center of a californicus, nor yellowing like a xanthodermus. Also, I don’t believe that Mike noticed a phenolic odor when it was fresh; there is certainly none now that it is dried.

Agaricus most likely
By: Dimitar Bojantchev (dimitar)
2012-08-02 13:07:09 CDT (-0500)

Reminds me of the dried Agaricus californicus / xanthodermus that we get this time of year:

But Agrocybe is not a bad guess either, note the pattern of the cracking on the cap, it is a bit more like Agrocybe.

In all cases the spores should have smooth walls. If you have it, send a piece and I will check the spores when I come back from Scandinavia in a week.

Who did the microscopy on this one?
By: Dimitar Bojantchev (dimitar)
2012-08-02 13:02:55 CDT (-0500)

These are spores from a Russulaceae, most likely, with a far distant chance of something around Leucopaxillus/Melanoleuca, but where the hell is my immersion oil and quality spore photography? Bad microscopy is worse than no microscopy at all. On top of that I bet there was some contamination.


By: Mike McCurdy (lesmcurdy)
2012-08-01 21:06:26 CDT (-0500)

Any ideas?

By: Christian (Christian Schwarz)
2012-08-01 20:39:52 CDT (-0500)

those are bizarre spores to have come from that mushroom.

Gills free?
By: Mike McCurdy (lesmcurdy)
2012-08-01 20:07:13 CDT (-0500)

They appear to be, but the specimen was nearly dried when I found it making it hard to tell. Thanks to Debbie Viess for the photo of the spores.

yeah, I thought of Agrocybe too…
By: Debbie Viess (amanitarita)
2012-08-01 12:49:26 CDT (-0500)

but what Agrocybe (or Agaricus, for that matter) has lumpy, warted spores?

ARE those gills free in your second collection of this, Mike? Hard to tell in these photos.

Created: 2012-07-30 10:52:00 CDT (-0500)
Last modified: 2013-07-22 15:27:51 CDT (-0500)
Viewed: 751 times, last viewed: 2017-05-12 11:10:32 CDT (-0500)
Show Log