Confused by small white Mycena / Hemimycena / Phloeomana

**Steve_mt** · 26. September 2024

Some time ago I have found a cluster of small Mycena growing on decaying bramble sticks (Rubus ulmifolius) having a purely white and slightly transparent colour (esp. the stipe), fading a bit into beige when old. Cap 7-12 mm wide with non-numerous, spaced (not crowded) lamellae, horizontally-arched not particularly decurrent. Basidia 4-sporous (sometimes 2). There were swollen hyphae from sub-globose to broadly cylindrical, sometimes with a short foot (sphaeropedunculate) which I think were cheilo or/and pleuro cystidia (40-90 x 25-50 um). Spores 8-10 x 4.5-6 um (Q 1.5-1.9) ovate-elliptical to moderately broadly ovate, very rare to find in slides. I didn't check well the pileipellis. The stipe was more or less glabrous but I think I got a slide showing some caulocystidia.

Do you have any suggestions?

I shortlisted to Hemimycena gracilis, Mycena alba, Mycena pseudolactea, Mycene spiraea

**Steve_mt** · 26. September 2024

rare occurrence of caulocystidia

**larchbolete** · 26. September 2024

hi Steve,

Have you checked amyloidity?

regards Pit

**Steve_mt** · 26. September 2024

Zitat von larchbolete

hi Steve,

Have you checked amyloidity?

regards Pit

No unfortunately, but my heart tells me it is a member of the Phloeomana group (they are all inamyloid if I remmeber well). Still, I am not convinced it is P. hiemalis (best match) or alba, because there are some considerable mismatches. I discarded the option M. polyadelpha too. Those inflated hyphae are very peculiar!

**Mreul** · 26. September 2024

Hi Steve,

not always easy those small white ones and some of the features shown are not yet clear to me, but I'd have some suggestions.

First of all, Hemimycena gracilis has clearly narrower spores, always more than three times longer than wide. Phloeomana alba can be excluded as well, this one has globose to subglobose spores, Phloeomana speirea is normally 2-spored. Hemimycena pseudolactea with more crowded lamellae, Phloeomana hiemalis and Mycena polyadelpha both have cheilocystidia that you surely would have found in their typical form if they were present.

I don't believe you have a member of Phloeomana, but of Hemimycena (s.l.).

Some thoughts about the characteristics you mention:

- The large cells you show could be cells from the trama, either the lamellae or the pileus. I am not aware of any hemimycenoid fungus that would only have approximately as large cheilo or pleurocystidia. Since you did not find any other cells that can be clearly discerned as hymenial cystidia I currently believe they are absent here or at least very inconspicuous.

- Did you find any diverticulate hyphae in the pileipellis? I think I can see some, but as the resolution is very low, what I see could as well be some foreign elements (dust), etc.
I marked the places where I believe to see diverticulate hyphae in the picture composed of yours below (a)

- There are obviously very long, partially wavy, slightly thick-walled caulocystidia that clearly exceed the normal length for those of e.g. speirea, marked below in part b

Can you confirm those long thick-walled elements exist especially at the base of the stipe?

If I am right with my assumptions, you would have a species with spores of up to about 10 x 5 µm, 4-spored basidia, no hymenial cystidia, a diverticulate pilepiellis and very long thick-walled caulocystidia at lest at the stipe base. This together with the macroscopy leads me to Hemimycena pseudocrispula.

Clamps should be present, and the spores seem a bit large, is it possible they are mostly rather up tp 9 x 4-5 µm? This would then fit perfectly also to what I know as H. pseudocrispula, but those measurements alone would not convice me of another species.

Those are my thoughts so far, they don't need to be true, of course.

Cheers,

Matthias

**Steve_mt** · 27. September 2024

Matthias, I am hugely indebted to your time and explanation. I will review the images for the details you suggested. Yes, I agree this is a Hemimycena following you line of thought and findings.

Coincidently another member shared a link to a monograph on Hemimycena in Europe by Antonin and Noordeloos (together with other related Mycenoid genera)

**Steve_mt** · 27. September 2024

Dear Matthias

I have re-explored my images and I have some further information.

1. Spores:

(7) 8.2 - 9.3 (9.9) × (4.5) 4.55 - 5.1 (5.7) µm

Q = (1.5) 1.51 - 2 ; N = 7

Me = 8.7 × 4.9 µm ; Qe = 1.8

Not very common, based on 7 spores only, but it matches the measurments you suggested

2. Clamp junctions

I might have seen a few in the stipe but not abundant. I marked a few.

3. Inflated Hyphae

You are correct, must be trama / structural hypha under the hymenium

4. Stipe long hairs

Yes, these are very setiform hairs coming out from the stipe. I cant say if at the base or at the apex.

5. Lack of cystidia and pleurocystidia

Agree, absent - they should appear in my slides. I only see few basidia and basidiomes.

The only bad news is that I have not examined and photographed the pileipellis and maybe those you noticed are artefacts. I will study your suggested species shortly. (It looks like it at a glance!). Check some strange structures in one image (below) like a cluster of spores. Some kind of artefact I think.

**Mreul** · 27. September 2024

Hi Steve,

thanks for the additional information. Yes, clearly clamped, so in my opinion everything fits for pseudocrispula. I would not know a species that would only be distinguished by pilepellis, so this should be fine.

In Antonín and Noordeloos the spores are given as even larger, up to 11,5 long. I have never observed such large spores myself, but I know this species only from one site up to now. Your new spore measurements are almost perfectly those I obtained for my finds. I could not obtain a spore print so far for this species, maybe there spores would be somewhat larger.

Cheers,

Matthias

**Steve_mt** · 29. September 2024

I always experience poor spore amounts with the small white Phloeomana / Hemimycena ( / Mycena) spp. that I never even think of attempting a spore print. I should do amyloid test from now on, and better observations on the pilleipellis. I look forward this season to study more collections. I think I have some one or two old findings yet undetermined, which I may discuss in this group.

Thank you for your help and correspondence. I will insert a note Det. by Matthias ??? (what surname pls? - send me a private message if you wish to keep it secret from public domain) Btw Happy birthday tomorrow

Confused by small white Mycena / Hemimycena / Phloeomana

Steve_mt 26. September 2024

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