I thought this would be easy because I'd just have to find some mature '3-septate' spores showing the cell walls separating the spore into 4 compartments (like I observed here).
Despite scanning through squashes for AGES, I haven't found any 3-septate spores. But I have found some interesting-looking bits and bobs. This figure, which I stumbled upon on ResearchGate has been very helpful in making sense of what I'm seeing.
|Figure reproduced from Oberwinkler (2014) here. Life cycle of Dacrymyces stillatus. (a) Basidiocarps (b) Fructification with fragmenting hyphae (i). (c) Detail of hymenium and subhymenium. (d) Basidial ontogeny showing stages of nuclear divisions in basidia. (e) Basidiospores and spore germination. (f) Yeastlike budding of microconidia. (g) Spore germination with hyphae, illustrated from D. palmatus but also occurring in D. stillatus . (h) Fragmented hyphae producing microconidia. (i) Short-celled fragmentation of peripheral hyphae from anamorph fructification (b). Figures not to scale; originally from Oberwinkler (2012).|
These are what I observed in the field.
This tangled, branching mass of hyphae matches nicely with the illustration of the hymenium. As far as I could tell, there were no clamp connections.
Basidia (the microscopic structures which bear the spores)
I've got basidia at various stages of maturity here.
This shows nicely a mature basidia with spores growing on the tips. At top left a larger spore has been cast off to begin a life of its own. I make it about 11.5 x 6.5 microns in size – smaller than D. stillatus. Perhaps it's still got some growing to do?
I'm not sure what I'm seeing here... Perhaps "nuclear divisions in basidia"?
I could find very few spores in this collection. This one was starting to approach the dimensions of D. stillatus which the Collins (illustrated) Fungi Guide (Buczacki et al) give as 14 - 17 x 5 - 6 microns. Most were a bit smaller, around 11.5 microns in length.
I haven't been able to detect any septate structure to the spores – they look to just be filled with oil droplets – which I fear leaves things rather inconclusive as to the species identification.
For the record
Location: The Big Beech, Rowland Wood, East Sussex
Grid reference: TQ514150