Given that the mushroom I was looking at was yellow, and in a field, it seemed a bit too easy when I came across Yellow Fieldcap (Bolbitius titubans).
- Bright yellow
- Sticky (or "viscid") to the touch
- Slender, cylindrical, pale yellow & hollow stem (or "stipe") up to 8 cm long
- Gills crowded; pale yellow at first and later cinnamon
- Cap 1 - 4 cm across, acorn-shaped then bell-shaped, finally expanding to almost flat; chrome yellow at first, fading to grey-brown at the margin
I'd found it on improved grassland, used for grazing, so the habitat is also right for B. titubans as they like rich or manured grasslands.
Only Michael Jordan's Fungi has thrown a spanner in the works with reference to a similar, "infrequent", species: B. vitellinus. Apparently the two can be distinguished by colour, "pruinosity of stipe" (had to look this up - it means the extent to which the stem is covered in a fine powder), and spore size.
This is where it gets confusing, because the British Mycological Society GB Checklist of Fungal Names lists B. vitellinus as a synonym for Bolbitius titubans. Which means... they're the same thing?
Wikipedia says they're the same thing too, so it must be true. Maybe I have successfully identified Bolbitius titubans to species level after all?
For the record
Location: Field between Horton Wood & the River Adur, Small Dole
Grid reference: TQ20671274
Added to FRDBI: 13/02/2017