Cup Fungus Tarzetta cupularis
We start broad beans off, under glass, by planting seeds in compost inside cardboard tubes from inside toilet rolls. This colony was on the compost supporting the outsides of the tubes. The large white areas or large arcs are the tubes.
Such an extensive colony is a rare find.
The last single frame image is probably most typical of the stage first noticed.
The taxonomy of the genus is a bit confused but I will stick with T. cupularis for this upload.
For other information see the links:
Olympus EM-1 (aperture priority), Olympus 4/3 x2 TC, Olympus 4/3 50mm f2 macro, f11, sunlight hand-held.
The stereo is crosseye.
Some of the smallest fruiting bodies: