Observation 65005: Paxillus Fr.
When: 2010-07-14
Herbarium specimen reported

Notes: I’ve known that there are several Paxillus species passing under the too-generic name of “Paxillus involutus” but this one is rather curious. The fungi in the picture are tiny – the largest one is maybe 35 mm in diameter. There were 5 or 6 of them there and they looked healthy enough for me to think that this is a more or less normal size for this taxon.

I’ve looked at it through the microscope and apparently it has rather unusual cystidia (more or less the same on gill edges and surfaces). They’re profoundly mucronate and the only species in Funga Nordica with mucronate cystidia is an obscure and large species P. validus, but it has other specified hosts (Tilia, Populus, …, not Birch).

They grew on soil stuck on the roots of an uprooted birch (Betula pendula) tree.
We also have a huge, thick-stemmed, rather uniformly colored species which grows under birch early in the season, I’ll post it as soon as I find it this year.

Any ideas?
I’ll be very grateful if anyone could recommend something to read on Paxillus (or, in a perfect scenario, a Paxillus expert I could show our Paxillus varieties to).

Images

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unripe basidia – there are a lot of clamps in all tissues
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lamella cross-section – you can see the subhymenial hyphae, long, parallel and with clamps, and mucronate pleurocystidia (the apices of the cystidia are often colored).
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hymenium, another view
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mashed subhymenium, not a very informative shot but you can have the general idea of the thickness, length, and the amount of clamps on the subhymenial hyphae.
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clamp shape on the larger hyphae going from the center of the lamella to the basidia and the subhymenial layer
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hyphae of the pileipellis. The swollen elements are quite typical and can be seen here and there.
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pileipellis again, there are some colored elements interwoven into more typical hyphae (like on the picture above).
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a crappy picture but it gives the idea of what the cap flesh is composed of – thick, short, branching, randomly arranged hyphae with rounded terminal elements and numerous clamps.
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a typical pleurocystidium and a strange cell which has the shape of a cystidium and contents of a basidium.
139430
there are 4, 2, and 1-sterigmate basidia in the hymenium

Proposed Names

83% (1)
Eye3 Eyes3
Recognized by sight
Based on microscopic features

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Eye3 = Observer’s choice
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Comments

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Thank you!
By: Tatiana Bulyonkova (ressaure)
2011-04-02 09:28:17 MST (-0700)

… my Amanitas will have to wait tonight now that I’ve got some Paxillus reading to do :)

I also noticed that microstructures are practically ignored in most of the descriptions I’ve seen. Imho the coluor&texture features are a bit unreliable, I sometimes see substantial variation of within one mycelium depending on weather and lighting, I mean felty – smooth, pale – dark, etc. I haven’t tried checking the spore print colour and I didn’t know about the importance of rhizomorphs (according to the Boletales website, they are important).

Impressive documentation!
By: Irene Andersson (irenea)
2011-04-02 01:53:09 MST (-0700)

The keys I have seen are focusing more on spore and gill colours, and don’t describe the cystidia very carefully, so they may be variable in the Paxillus involutus complex. But that character is certainly worth more investigations.

A Paxillus key here:
http://www.tham-thueringen.de/tham/html/paxillus.html
contains the same 5 species you find in Funga Nordica.

3 more species are known from Europe according to the Boletales site:
http://boletales.com/genera/paxillus/
Still not complete, but a promising initiative!

Let’s see if Else notices this observation, she has done some work with Paxillus.

Created: 2011-04-02 00:32:35 MST (-0700)
Last modified: 2011-04-02 00:41:32 MST (-0700)
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