Observation 220589: Agaricus subrutilescens (Kauffman) Hotson & D.E. Stuntz

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It may take some time
By: Sava Krstic (sava)
2015-10-29 04:55:00 CET (+0100)

… till somebody shows a dark-capped baby Leucoagaricus, but the possibility does not seem to be remote. Thanks to Christian for the always welcome healthy skepticism, and to all who contributed to the discussion.

well, darkish
By: Debbie Viess (amanitarita)
2015-10-29 03:46:15 CET (+0100)

a sort of nice, streaky brown, but nothing like that way dark cap in the photo, and certainly none of that red staining that you show and a very different PV (membranous and well developed and ready to drop here, as opposed to that typical abbreviated lep veil in your photo).

so maybe, kinda brownish, sure, but this obsie is certainly subrutilescens.

please share a photo of that “black cap” for a western Leucoagaricus tho, if you have it.

do you have photos of those dark brown capped Leucoagaricus?
By: Debbie Viess (amanitarita)
2015-10-28 21:51:11 CET (+0100)

please link to them!

The reason
By: Christian (Christian Schwarz)
2015-10-28 20:27:04 CET (+0100)

I doubted Agaricus was due to the pale gills. Most A. subrutilescens group I’ve seen have pinker gills (or at least dull pinkish-gray) even when the caps are still closed and “bleed” a bit where cut.

The slightly floccose-shaggy stipe is better for Agaricus however.

Debbie, I see quite a few brown-capped Leucoagaricus in CA, including a largish and very common one under cypress.

thanks Sava
By: Debbie Viess (amanitarita)
2015-10-28 16:04:43 CET (+0100)

for your insightful and measured first hand observations.

Young subrutilescens
By: Sava Krstic (sava)
2015-10-28 05:10:16 CET (+0100)

Danny Miller and I looked at this when I brought it and it was actually he who guessed the species name. We have A. subrutilescens almost every year at this OMS event; it’s common in the area. The next day people brought several collections of it and one was slightly older than these, so we could see how the caps change color with age, the brown fibrils taking less and less of the area. The stem is floccose in all stages. In my mind there is little doubt that it’s subrutilescens; it’s just that I haven’t seen it so young before.

As for Leucoagaricus, we have leucothites almost every year (this included), but no other species from what I remember.

We had a more puzzling young Agaricus collection at this camp five years ago: http://mushroomobserver.org/57703?q=2f5eA. It had an impressively black cap, and was a red-stainer.

alright …
By: Debbie Viess (amanitarita)
2015-10-27 23:30:31 CET (+0100)

which unnamed sp. of Leu. rubrotincti have these dark brown caps when young?

if you have actually seen some, then I believe you. Can you share photos here, even if they are unnamed as of yet? Who better than you?

as to a proposed (only) name of Agaricus “thiersii” … as only briefly described in CA Fu, this Agaricus doesn’t show a particularly “stocky” fb, and details of the cap are not obvious, other than the dark color.

It must’ve been one of the many Kerrigan Agaricus names in CA Fungi that were used as though they were already published, which of course they are not.

I look forward to the actual publication of Kerrigan’s Agaricus book, and the detailing of these new species, as well as the (hopefully) widespread use and acceptance of his new names. Until then … a bit premature, eh?

Yes, these are too young for a good ID, esp. only from a photo. If you have actually seen dark brown capped Leucoagaricus sp. in the west, then sure, this could be one of those, too. But I have never seen one, myself, nor can I find western examples elsewhere.

this or that, without more data we’ll never know.
By: else
2015-10-27 20:22:57 CET (+0100)

as i said it could be either.
most western species in Leucoagaricus sect. Rubrotincti have not been named yet.
Agaricus thiersii – is a coarser more truncate version of Agaricus subrutilescens – reference to it in the Dennis et al. California mushrooms book (under Ag. subrutilescens).

OK I’ll bite …
By: Debbie Viess (amanitarita)
2015-10-27 19:12:37 CET (+0100)

which western Leucoagaricus has a dark brown cap like this one? That seemed to be the deciding factor between those two possible genera.

Indeed, youth in this case is a disadvantage.

And what is “Agaricus thiersii?”

could be either
By: else
2015-10-27 19:02:58 CET (+0100)

These fruitbodies are so young, it is hard to tell what they would have become later in life. It could be either an Agaricus species (A. thiersii perhaps), or a Leucoagaricus.

agaricus gills can start out quite pale …
By: Debbie Viess (amanitarita)
2015-10-27 16:55:35 CET (+0100)

these mushrooms are barely developed!

all other features work for subrutilescens … dark brown cap, shaggy white hollow stem, slightly bulbous at base.

For a subrutilescens very similar to your example, see Doug Smith’s obsie here:

http://mushroomobserver.org/image/show_image/1597?obs=1432&q=2f52j

I know of no dark brown capped Leucoagaricus sp. here in the west. Do you?

Leucoagaricus?
By: Joe Cohen (Joseph D. Cohen)
2015-10-27 15:46:56 CET (+0100)

Christian:

Thanks for picking up on this.

The gill color (as indicator of spore color) was bothering me when I posted this.
But is there a Leucoagaricus with a cap color like this Observation?
Perhaps it simply had not sporulated.
And maybe Sava Krstic has some insight.

— Joe

I wonder
By: Christian (Christian Schwarz)
2015-10-26 02:10:54 CET (+0100)

if this is not a white-spored species, likely a Leucoagaricus

Created: 2015-10-26 01:36:24 CET (+0100)
Last modified: 2015-10-29 03:53:12 CET (+0100)
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