How to tell Oak milkcap from Brown rollrim

The cap is 3 to 10 cm across, usually 4 to 8 cm, convex with an inrolled margin at first, then flattened with a shallow central dip and finally shallowly funnel-shaped; a central bump is rare.

It's a dull reddish brown, cinnamon or yellow-brown, darker in the centre, with faint darker concentric zones or rings of spots. The surface is matt and dry, though it can look a little shiny in wet weather.

Cap 5–15 cm across, convex in young mushrooms, then depressed or funnel-shaped. Surface smooth, hairy-felty in young ones, almost bare in mature ones, olive brown or yellowish brown, sticky in wet weather. The margin stays rolled under for a long time — a characteristic feature.

The gills run slightly down the stem and are crowded and narrow, cream or pinkish buff at first, later reddish brown, often with rusty spots. Broken gills release plentiful white to creamy-white milk that doesn't turn bright yellow.

The spore print is cream with a slight salmon-pink tinge.

Gills crowded, thin, ochre-yellow or olive, easily separating from the flesh when pressed, browning when damaged. They run down the stem. This tendency to brown when pressed is a useful identification feature.

The stem is 3 to 7 cm tall and 0.5 to 1.5 cm thick, the colour of the cap and darker reddish brown towards the base, cylindrical, often furrowed lengthways, solid at first and later hollow. There's no ring.

Stem 3–8 cm tall, 1–2 cm thick, firm, solid, cylindrical or tapering downward, the same colour as the cap or slightly paler. No ring and no volva.

The flesh is firm, brittle and whitish, reddish brown in the stem base, and browns with age.

Flesh yellowish cream or brownish, firm in young ones, looser in mature ones. Browns when damaged. Has a slightly acrid or sourish taste. Does not exude milk.

An oily smell, often said to be like bugs, strongest in old or drying caps. The taste is mild to slightly bitter, not hot.

Smell sourish and pleasant, like fruit or vinegar, especially in mature mushrooms. This neutral, even pleasant smell is exactly what helped the mushroom pass as edible for so long.