Rhizomarasmius undatus

A species of Rhizomarasmius.

Here's a description of the species: The cap, initially whitish and convex with a powdery (pruinose) surface, later flattens out and turns brownish grey, reaching about 2.5 cm across. The gills are widely spaced and whitish, either broadly attached to the stem (adnate) or slightly running down it (decurrent). The spore print is white. The firm stem can reach approximately 12 cm in length and 2 mm in diameter. It is white towards the top, transitioning to dark brown or black lower down, and covered with a fine layer of short white hairs (pruinose). There is no notable smell or taste. The spores are lemon-shaped to ellipsoid, measuring approximately 9-12 µm by 5-7 µm.