When I recently found a mushroom with a nitrous odour growing on a stump, Tom kindly pointed me in the direction of Mycena alcalina. As is often the case, a routine check at home to confirm the diagnosis revealed something surprising – there is no such thing as M. alcalina.
Buczaki p226 states “M.alcalina is a British mycological myth, no such species exists..”
Fungi of Switzerland is no more encouraging: M.alcalina “A nomen dubium variously interpreted”.
For something that does not exist, there are an awful lot of records in CATE2 – 755 in fact. So what is going on?
It turns out that, in 1987, somebody very observant realised that there were in fact two similar species with a nitrous odour growing on stumps – M. stipata and M. silvae-nigrae.
M.stipata fruits only in the autumn and has 4-spored basidia. M. silvae-nigrae can be found in spring and autumn and has 2-spored basidia.
As this specimen was found in spring, it fits the description for the latter and, helpfully, the basidia were 2-spored and the gill edge cystidia and spore size matched the published data.
The confusion in this area may explain why there are only 23 records on CATE2 for what is probably quite a common species.
Basidia with 2 sterigmata
Gill Edge Cystidia
Me = 13.8 x 9.1 µm ; Qe = 1.5