Arcyria cinerea is one of the most common slime moulds.
Young pale brown fruit bodies (sporocarps), on a stalk are round then ovate.
Mature fruit bodies, 2 or 3 mm high are on a stalk.
The hypothallus at the base of their stalk can be pale brown, grey, yellowish or translucent.
The stalk and hypothallus may be joined to those of adjacent fruit bodies.
The spore containing sacs (sporotheca) are ovate to cylindrical with a rounded tip.
Up to 3 mm high and under 1 mm wide they are a pale grey, pale brown or yellow-brown.
The wall around sporotheca (peridium) breaks down early.
Inside the sporotheca the spores are among a network of thin threads (the capillitium).
The threads have tiny projections or spines along them.
The spores are pale yellow or grey.
J.F.
