bitter tannflathatt (tidligere tannrotsopp eller bitter rotsopp), Collybia fodiens. Rhodocollybia fodiens is a species of fungus in the mushroom family Marasmiaceae. Evt. men sannsynligvis ikke flekket flathatt, Rhodocollybia maculata. This small to medium-sized mushroom is recognized by its whitish cap, which develops cinnamon spots and stains as it matures; its very crowded, attached gills; its ecology (decomposing the wood or litter of conifers); its bitter taste. Saprobic; decomposing the deadwood or litter of conifers; spring (in warmer climates), summer, and fall.
Cap: 2–6 cm across; convex, becoming broadly convex or nearly flat, with an inrolled margin; dry; bald; white to whitish, developing cinnamon spots with age, or sometimes very pale tan; the margin not lined.
Gills: Narrowly attached to the stem; very crowded; short-gills frequent; white; sometimes developing rusty spots with age.
Stem: 5–7 cm long; 0.5–1 cm thick; equal, with a tapered rooting portion; bald; white; sometimes developing cinnamon to rusty spots with age; basal mycelium white.
Flesh: White; unchanging when sliced. Odor and Taste: Odor sweetish, or not distinctive; taste slightly to moderately bitter. Chemical Reactions: KOH negative on cap surface—or dull olive on darker caps. Spore Print: White or, in a very thick, fresh print, slightly pinkish