Kuehneromyces mutabilis, also known as Sheathed Woodtuft, is a medium-sized agaric that has an umbonate honey-brown to yellow hat, which dries from the centre, often producing a two-tone effect. It also has gills that are pale ochre at first and become cinnamon as the spores mature and a ring on the stem. It grows clustered on stumps and logs of broad-leaf trees, favouring birch. The mushroom can easily be confused with Galerina marginata (Deadly Galerina).

Cap convex, becoming broadly convex or nearly flat, and hygrophanous which means it is changing colour as it dries out and fading from tawny to orangish brown to yellowish or brownish (often passing through a two-toned stage). The cap flesh is pale tan, quite thin and unchanging when sliced. Gills adnate (broadly attached to the stem) and crowded, whitish to pale tan when young, becoming cinnamon brown as the spores mature. Stem pale and smooth above the fairly persistent stem ring, fibrous, scaly and dark tan below, graduating to almost black at the base. Spore print cinnamon brown.

Microscopic Features: The spores of the mushroom are broadly ellipsoidal, and smooth, measuring approximately 5.5-7.5 x 4-5µm. They possess an apical germ pore.

Similar species include Galerina marginata (Deadly Galerina).

Kuehneromyces mutabilis on the First Nature Web site.
Kuehneromyces mutabilis on the MushroomExpert.Com Web site.