Out of my depth

UPDATE 08/11/2016 – As sometimes happens with field identifications, the post below picks up the wrong trail and follows it to some erroneous conclusions. I'll leave it here as a tribute to this blog's title: Misidentifying Fungi. Feel free to skip to the comments for an accurate ID.

I arrived at work on Friday to find this sitting on my desk.

"Who's left their lunchbox on my desk?" I said. And, peering through the lid, I was convinced I could see the remains of a banana in that plastic bag.

However, upon opening my emails, the mystery was solved. I'd received this short missive from Graeme Lyons, the Sussex Wildlife Trust ecologist:

"Hi Clare

I have left a webcap in a lunch box on your desk. I believe it could be the rare Splendid Webcap. Any chance you could look at the spores please?

It’s meant to be deadly poisonous!

Graeme"

Well, asiduous readers of this blog will know that I only found out what Webcaps (Cortinarius species) look like about two months ago, on a trip to Birchden Wood with Sussex Fungus Group. So it was with some trepidation that I took the mushroom out of bag.

This is what I found...

(Ignore the dark line around the top of the stem. I forgot to take a picture before I sliced the stem off to get a spore print.)

It looked fairly orangey-brown by the time it got to me. But Graeme says it looked a bright brilliant yellow in the field.

To be honest, I wouldn't have thought to put it in the genus Cortinarius because I couldn't make out any trace of a cobwebby veil. But let's proceed on the assumption that it is a Cortinarius.

I found that Michael Kuo has written a helpful introduction to the genus Cortinarius, here, which goes through the various features that can be observed to confirm an identification. These include:

• Mycorrhizal association
• Sliminess
• Hygrophanous-ness (yes, he recognises this isn't a word)
• Colour of the young gills
• Stem details
• Odour and taste
• Reaction to KOH
• Microscopic details

I messaged Graeme for some more details and he explained he'd found them growing under Beech – looking HUGE and brilliant bright yellow.

Mycorrhizal association – Beech.

I imagine Graeme's brought me a specimen which had already broken off from its base, so I only had a bit of the stem to look at. The specimen looked to be reasonably mature and fairly dry, so ...

Sliminess – Not slimy.

Hygrophanous-ness – None observed.

Colour of the young gills – Not observed.

Michael Kuo explains that, "The base of the stem is another important feature in Cortinarius identification ... The stem may be more or less equal, or club-shaped ("clavate" in Mycologese), or swollen dramatically and suddenly at the base, so that the basal bulb has a rim (in which case the bulb is said to be "marginate")." And the remains of the veil are another feature to look out for.

Stem details –  Base not observed. No veil observed. 

Odour and taste – Doesn't smell of much. And I'm definitely not tasting it.

Reaction to KOH – Haven't got any KOH, sorry.

*Hmm... I don't feel like this mushroom identification is going that well...*

Microscopic details – I can do this! Well, kind of. I can have a look at the spores but I can't measure them because I haven't got a graticule (a measuring thing).

I got a spore print which looks like this. RUSTY! Or tobacco-brown. This is a good sign. Cortinarius are supposed to have tobacco-brown spores.

Getting the spores under the microscope, they look like this:

i.e. Sort of a bit lemon or almond shaped. With bobbles on.

I looked in Funga Nordica to see what Cortinarius spores are supposed to look like. A lot of them look broadly like this:

Unfortunately neither my microscope nor my microscopy skills seem quite up to the job of examining the spore ornamentation in great detail. 

So, in conclusion, I have no idea what species of mushroom this is that Graeme left in a lunchbox on my desk.

But for a bit of Saturday morning fun, while I've got Funga Nordica off the shelf, let's see what features we'd need to observe if we did want to make this the Splendid Webcap Cortinarius splendens.

There are over 100 pages of keys to the Cortinarius species in Funga Nordica. A specimen with an indistinct veil, dry cap and dry stem (often with a bulbous base) will get you to the subgenera Phlegmacium in which C. splendens resides.

From there, a bulbous stem and gills which are "initially yellow, green or olivaceous" will get you to Key A to the subgenera Phlegmacium. And these are the features you can observe in the field which will take you to C. splendens:

1. Cap not hygrophanous ...
2. Smell faint, weak malty, farinaceous, like black pepper, boiled potatoes, aniseed, radish, unripe banana, apple, marjoram or lemon cake [OK ...]
3. KOH on cap negative, brownish to ± red brown, or weakly olivaceous [Hmm, must get some KOH...]
4. Young gills greenish yellow, flesh in stem top not brownish when young [Evidently important to get them while they're young...]
5. Flesh in both bulb and cap bright yellow or greenish yellow; fruit body intensely coloured... [This would match with Graeme's field observations ...]
6. With Beech (or very rarely Limes) [Yes!]
7. Fruit body bright yellow, hardly with any greenish tinges when young. Gills bright lemon yellow when young. Stem bright lemon yellow with a marginate bulb. Smell indistinct.

Simples! 

POSTSCRIPT 05/11/2016 - Here are Graeme's photos of his mushrooms:

@__clare__ and here are the big bright Cortinarius! pic.twitter.com/tuPoksC9oZ

— Graeme Lyons (@graemelyons) November 5, 2016

For the record
Record to be submitted by Graeme Lyons