From the top (second photo) these look like Bisporella citrina, relatively common in my area. But as far as I know Bisporella citrina does not have a stem. Perhaps this is some type of Chloroscypha or Hymenoscyphus?
Found on a piece of well decayed tan oak log.
Micrograph shows pileipellis with corkscrew cystidia, spores and a basidium 1000x.
Cheilocystidia fusiform.
Spores from the cap / gills measure:
(8.5) 8.6 - 10 (10.4) × (2.9) 3 - 3.3 (3.4) µm
Q = (2.8) 2.82 - 3.29 (3.3) ; N = 12
Me = 9.4 × 3.1 µm ; Qe = 3
I wasn't able to find the host. At the base of a palm tree.
Under Fagus sylvicola. Likely the European species because the volva is white and host tree is European.
Crossing road.