Misidentifying Fungi: Shades of Beige

Friday, 9 November 2018

Shades of Beige

I joined Sussex Fungus Group at Sussex Wildlife Trust's Malling Down reserve on Wednesday, looking for fungi associated with rock-rose, Helianthemum.

I hadn't done my homework for this foray, so had to confess to not knowing what Helianthemum looks like. But after I'd been introduced to its dark green oval leaves, I was reminded that I'd found a photo of Common Rock-rose Helianthemum nummularium in the photographic collection of my late friend, Heather Monie. There's a rather lovely photograph of Heather photographing this rock-rose, here; it gives me rucksack-envy whenever I look at it: they don't make 'em like they used to in 1972.

Common Rock-rose Helianthemum nummularium, Cleve Hill, 1972. © Heather Monie.

In the rabbit-grazed sward of 'the snout' (TQ42921078), the Helianthemum wasn't quite as eye-catching as it is in that picture. But easy enough to find once you'd got your eye in.

It wasn't long before we found what we were looking for: a Cortinarius, characterised by the web-like veil around the top of the stipe, coloured brown where it has caught the descending spores.

Kare Liimatainen and Martyn Ainsworth have published a paper on 'Fifteen Cortinarius species associated with Helianthemum in Great Britain: results of a DNA-based analysis' and thought this collection is likely to be Cortinarius epsomiensis, one of the species in the group 'Anomali'. They explain in their paper that, "C. epsomiensis is mainly characterised by the broadly ellipsoid spores. When large spores of 9 x 7 μm are found, one can be rather sure about the identification. Some specimens, however, have somewhat smaller spores and are then difficult to distinguish from those of C. albocyaneus. In such cases, an ITS sequence is needed for an unambiguous identification." — this specimen returned with Kare and Martyn to Kew, where hopefully its identity can be confirmed.

We peaked early in our search for Cortinarius, and that was the only specimen we found; despite Martyn recalling that the area was "a forest of fruit bodies" this time last year.

The rest of our foray was characterised by mushrooms in various shades of beige. Some possible Inocybe mushrooms, growing on the ant-hills among the Helianthemum, sparked quite a bit of interest. There was also this somewhat cartoonish-looking mushroom. Did someone say it might be Leucoagaricus?

Towards the top of the snout we came across as patch of Fairy Ring Champignon Marasmius oreades; their most distinctive feature being their distant gills, which you can't see in this picture.

And on the slopes to the north (around TQ428109), we found a big patch of Fool's Funnel Clitocybe rivulosa.

Malling Down is also the furthest inland location for the rare bracket fungus Perenniporia ochroleuca — one of the Lost & Found Fungi species, which we've recorded previously at Seaford Head. It grows here on the scrub at the top of the snout (TQ431108).

The Flora of Sussex shows that Common Rock-rose Helianthemum nummularium is present at sites all along the Downs, so it would be worth checking other sites to see if they also hold associated fungal species. If you enjoy the challenge of such enigmatic fungi as the Cortinarius, that is.