Collybia (Gymnopus) fuscopurpureus revisited

[RobSutton]

About this time last year I posted a thread partly about this specimen:



and got a great deal of help from various people including these comments:

ManwithNoname

Re: An Asco and a small brown job for ID
I'd agree with your suggestion of Gymnopus fuscopurpureus, although, when I've found it, it was growing more in a dense cluster. The spores are the right shape and in the appropriate size range.

That's what it would key out to with Antonin and Noordeloos's monograph, although the photo there doesn't help much. Interestingly, though, there is some debate about whether the species found in Britain is actually the Gymnopus fuscopurpureus in their monograph, or actually an American species known as Collybia biformis, which makes it a bit difficult to key out since that species is not included in the version of the monograph I have.

PS Just checked the notes in the Checklist and here is what it says:

'Notes: Previously considered a rarity, this has become commoner, at least in southern England, and there is a single collection from Wales (Denbighshire). There is some doubt that this is the species described in A&N1: 109, since British collections do not show a green reaction with alkali. It has been suggested that British material may represent the North American Collybia biformis (Peck) Singer.'

Antonin and Noordeloos say 'walls of all hyphae, including most hymenial elements and especially the crustations on the hyphal wall turn green in alkali'. So there's a test for you to try out. But if it doesn't work it could still be the British form currently with the same name!

ManwithNoname
Wild Member

The Collybia fuscopurpurea in Fungi of Switzerland is synonymised with Gymnopus fagiphilus in the monograph, and the monograph refers to this photo in FoS as representing G. fagiphilus (there is no photo in the monograph). The specimens in the photo in FoS actually look more like the ones I photographed, although the habitat and nearby trees associated with that species don't fit with my specimens.

The Collybia alkavirens in FoS is synonymised with Gymnopus fuscopurpureus and the true G. alkavirens is not considered to be a European species. Your specimens look more like the Collybia alkavirens in FoS, so you may have Gymnopus fuscopurpureus as defined in the monograph. I wonder whether your specimens would have shown the green reaction with alkali under the microscope?

I doubt that has made things any clearer.

I've found what I think is the same species (it looks very different as it is strongly hygrophanous) in the same habitat and more or less identical location.



This year I've managed to do the alkali test (mounted a section in water and then allowed 10% KOH to diffuse in from the edge whilst looking at it under the microscope) and did see some green developing in the cap tissues where there were small amounts of encrusting pigments around some of the hyphae:





This is really interesting as the Basidiomycota Checklist quoted above says collections from UK do not show this reaction. I didn't see any green colour developing when applying a small drop to the cap or stem - it just rewetted that section and it turned very dark brown but under the microscope the change was quite distinct but only in small areas of pigment rather than to the tissues themselves.

[Ken Burgess]

Hi Rob

I have only had time for a quick look at this but here is what I have found:

Using the key in the 2010 edition of Antonin and Noordeloos's monograph I have assumed that your specimens are collybioid, have no distinct smell and the stem is hairy-tomentose to strigose, particularly in the lower half. Following this line, you get to a section of the key that includes 5 species which apparently show a reaction in which the hyphae in the pileipellis turn green in KOH. The good news is that the first couplet for these species appears to solve the problem on spore size alone:

41 Spores (6.0) 6.5-8.5 x (2.5) 3.0-5.0 (5.0) microns; pileipellis in the form of a Dryophila-structure... Gymnopus fuscopurpureus

41* Spores larger, 8.0-14 x 4.0-5.5 microns; pileipellis never forming a Dryophila-structure or only transition to the true Dryophila-structure... 42

You measured your spores as 6.5 x 3.5µ, which would fit neatly into the size range for Gymnopus fuscopurpureus and appears well outside the range for the other four species.

Under chemical reactions it says for this species: 'walls of all hyphae, including most hymenial elements and especially the encrustations on hyphal wall turn green in alkali'. Again, that seems to fit with your findings.

Other possibilities such as G. fagiphilus should be ruled out because they do not show the green reaction with alkali.

The key for Gymnopus isn't perfect because to get to the couplet at 40you have to assume that your pileipellis is a cutis, rather than having a Dryophila-structure, but when you get to 40, you find that one species should have a Dryophila-structure ('with lobed to coralloid terminal elements' to the cap hyphae), namely G. fuscopurpureus. I think there may well be some lobed to coralloid elements in your first image of the cap cuticle.

So Gymnopus fuscopurpureus (Pers.:Fr) Antonin, Halling & Noordel. seems the most likely candidate for your specimens. This species is described as widespread but rare in Central Europe. It grows under Fagus on calcareous soils.

That's all I've had time to look at.

Ken

[RobSutton]

Originally Posted by Ken Burgess

Hi Rob

I have only had time for a quick look at this but here is what I have found:

.........

The key for Gymnopus isn't perfect because to get to the couplet at 40you have to assume that your pileipellis is a cutis, rather than having a Dryophila-structure, but when you get to 40, you find that one species should have a Dryophila-structure ('with lobed to coralloid terminal elements' to the cap hyphae), namely G. fuscopurpureus. I think there may well be some lobed to coralloid elements in your first image of the cap cuticle.

So Gymnopus fuscopurpureus (Pers.:Fr) Antonin, Halling & Noordel. seems the most likely candidate for your specimens. This species is described as widespread but rare in Central Europe. It grows under Fagus on calcareous soils.

That's all I've had time to look at.

Ken

Thanks Ken - you're a star. It doesn't have any distinctive smell or taste and the cap certainly does seem to have coralloid elements:




and the habitat is correct, under beech on limestone. It's taken me a year but this looks pretty good to me - it's at this point that someone else usually comes along with the "fly in the ointment" bit


.......... I'm waiting