by Fungus Ken

To identify fungi accurately you need to understand something about the way a typical mushroom develops. There are two different types of veil - the universal veil and the partial veil.

If a universal veil is present, the sac envelops the whole mushroom when it is first formed as a primordium. As the mushroom grows the cap expands and the stem elongates, tearing the sac apart. The cellular structure of the veil will determine what then happens. In some cases there may be remains left as small patches on the cap and there may be signs of the sac at the bottom of the stem in the form of a volva. Amanita muscaria would be a typical and well-known example showing these remnants of the universal veil (NB this species also has a partial veil).

The other type of veil, the partial veil, runs from the edge of the cap to the stem, covering and protecting the immature gills. It can be present in the form of a membrane or it can be in the form of fine spider's web-like filaments (cortinate veil). When the cap expands this tears the veil. Again, the cellular structure of the veil will determine what happens. In some cases a distinct ring will be formed on the stem, in others you will get both a ring and veil remnants around the edge of the cap, and in yet others you may only see traces around the edge of the cap.

The ring may be free from the stem as in some species of Macrolepiota, which means you can move it up and down the stem. In some cases the veil remnants may be evanescent, which means they quickly disappear, so you would only find them in young specimens.

The type of partial veil called a cortinate veil (or cortina) is typical of species in the genus Cortinarius, giving an additional stature type - cortinarioid.

When trying to identify a mushroom you should always look closely to see if you can find remnants of either a partial veil or a universal veil because these can be critical in narrowing down the options to the right genus. Thinking in terms of stature types can be a useful reminder of the types of veil remnants you might expect to find in different groups of fungi.

Species with a pluteoid stature, for example, show no evidence of either a universal or a partial veil, hence the absence of a ring or volva. Vaginatoid species show signs of a universal veil but no partial veil - the ring is absent.

Don't forget to look closely to decide whether your specimen had one type of veil, both or neither. If the veils are present, the type and location of the veil framents can be vital pieces of information, both in identifying the genus and the species.

As we all know, for any mushroom you think you know, there are generally several other species which can look superficially similar and lead to confusion. This is why it is important to use all the information you have available to help in ruling out look-alikes.

The following photo in the gallery by widgeon0 is a helpful example.



At first glance, the brown cap colours and white stem could easily place it in the genus Hebeloma. It also seems to have the distinctive two-tone colours typical of Hebeloma mesophaeum, with the cap having a darker brown centre which becomes paler towards the edge. Growing in broadleaved woodland is the right habitat for this common and cosmopolitan species. Sorted. Job done.

Well actually, not quite. Let's think in terms of veils. Here we have evidence in the photo of a partial veil in the form of a membranous ring on the stem. There are two distinct groups in the genus Hebeloma, those without a partial veil (eg Hebeloma crustuliniforme) and those with a partial veil, Hebeloma mesophaeum probably being the most commonly recorded in this country. But along with Cortinarius and Inocybe, the group of species in Hebeloma which have a partial veil have a cortinate veil - they have a cortinarioid stature type. You would see this as fine threads running between the cap and stem in young specimens, or as woolly remnants in a ring zone on the stem or on the edge of the cap - the remains of the cortina.

Although the specimens in the photo clearly had a partial veil, in this case it was not present in the form of a cortina, but rather as a membrane, which has left a distinct ring on the stem. So we can actually rule out Hebeloma as an option on the basis of the information in the photo.

In fact the specimens in the photo are one of the species of Conocybe that possess a partial veil which forms a ring on the stem. These are included in the subgenus Pholiotina (which is sometimes given the status of a genus in its own right).

One species that typically fruits in the Spring is Conocybe aporos, but these species with a ring all look fairly similar and it would be difficult to be certain without microscopic information.

Ken