E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Features include very small size, white color, distant gills, a finely bristly stem, and growth on Populus.

Marasmius tremulae has been found at least in BC, AK, eastern Russia to central Europe, and Iceland, (Redhead). It has also been found in Finland (Hansen).

Cap:
0.2-0.4cm across, hemispheric then convex; white; very finely downy, (Moser)

Gills:
distant (3-8 gills), rarely dividing, (Moser)

Stem:
about 1cm long and 0.03cm wide, finely bristly, (Moser)

Microscopic spores:
spores 11-14 x 2.8-4 microns, cystidia with crystal heads; 2-spored basidia, hyphae without clamp connections, (Hansen), [spores presumably smooth]

Spore deposit:
[presumably whitish]