Visual characteristics of wild mushrooms

Field guides use a range of standard mushroom features when describing a species and you need to know what these mean. Some feature are obvious - such as cap size or stem length. Others require explanation - such as the types gill attachment.

This section helps to focus your observation to these specific features

Most fungi have a distinct cap sitting on the top of a stem. Many bracket fungi, however, have lateral stems, residual stems or no stems at all. The stomach fungi (puffballs) have no distinct cap but simply a body (although some do have more-or-less distinct stems).

Cap

When looking a cap there are a number of thing to look for. Firstly, there are the obvious characteristics of size, and colour. The shape of the cap is also useful, but it must be remembered that this is very likely to change as the fruit body matures. If you look at the surface of the cap does it have scales or obvious fibres? Is it dry, greasy or slimy?

Underneath the cap you will normally find gills. The Boletes, however have pores and some other species even have spines. When looking at the gills (or pores/tubes) note their colour, thickness and how crowded or widely spaced there are. Do they break easily? When you cut the cap in half how deep are the gills?

A point you’ll almost always see mentioned in descriptions is the gill attachment. This describes how (or whether) the gills join to the stem of the fungi. There are 5 terms commonly used:

Free

The gills don’t join the stem at all but curve-up to join directly back onto the cap

Adnate

The gills again curve up but join near the top of the stem

Adnex

The gills neither curve up nor down but join directly onto the stem

Sinuate

This is a combination of the previous two. The gills curved upwards but then curve back down as they join the stem

Decurrent

The gills curve down the stem

Stem

It’s very important to ensure that you have the complete stem when trying to identify a specimen as some characteristic features appear at the very base of the stem.

The two major features which may be present on the stem are the ring and the volva. The ring is a thin collar around the upper portion of the stem. The volva is a bag-like structure around the base of the stem.

Again, general observation should include size, colour, and shape. Is the stem cylindrical or does it taper from the top or bottom. Does it have a distinctly bulbous base? Does it have a circular cross-section or is it flattened? Is it smooth, rough or scaly

Flesh

If you cut the fruit body in half the flesh may offer other clues as to the fungi’s identity. The colour of the flesh is sometimes different from the colour of the skin. A surprising feature of some fungi is that the flesh changes colour when exposed to air. So the flesh may appear yellow when first cut and then turn blue. These colour changes can be almost instantaneous or happen gradually over a couple of hours.

Another useful features of the flesh to observe are its texture (woody, fibrous, soft, crumbly). The group of fungi called the Milkcaps exude fluid when cut (even from the smallest cut). The presence of this fluid (called latex) is enough to show that you have a Milkcap. The colour of the latex is useful in helping to decide which of the Milkcaps you have.