Cap surface

In mycology, the outer layer of a mushroom cap is called the cuticle (skin) or pileipellis. Like an animal's skin, this surface is the first line of defense for the mushroom's delicate, vulnerable flesh against a harsh environment.

The cuticle protects the fruiting body from two main enemies:

1. Drying out: holding on to moisture is critical for spores to mature.

2. Insects and slugs: some surfaces secrete bitter slime or become tough so the mushroom isn't eaten before it reproduces.

How weather changes things

David Arora stresses that the cap surface should only ever be assessed with the weather in mind.

A mushroom's texture is a very dynamic feature. If a field guide says a mushroom has a "slimy" cap (like a slippery jack), then during a two-week summer drought that same cap will become perfectly dry and shiny, and may even crack. On the other hand, the "dry", velvety bay bolete will feel damp and slightly sticky after a heavy downpour.

M.Ya. Zerova recommends always slightly moistening a finger (or your tongue) and touching the cap to check whether a thin layer of slime that has simply dried is hiding under a film that looks dry.

Main texture types

When identifying mushrooms, mycologists divide surfaces into several clear categories:

1. Smooth: the most common type, with no scales, slime or hairs.

2. Slimy / sticky: covered with a layer of slime or gelatin.

3. Velvety / suede-like: covered with microscopic down.

4. Fibrous: has radial "threads" ingrown into the skin.

5. Scaly: the skin breaks up, forming tile-like scales or flakes.

6. Cracked: deep fissures that expose the flesh beneath the skin.

Each of these surfaces can tell you a lot about exactly which mushroom you're holding and how safe it is.

Sources

1.Зерова М.Я. та ін. Визначник грибів України. 1979
2.Roger Phillips. Mushrooms (Roger Phillips)
3.David Arora. Mushrooms Demystified
4.Index Fungorum