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Describing a fungus |
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Professional mycologists often have to resort to a microscope and
the minute details of spore shape, size and colour to identify species.
Amateur mycologists are usually interested in what are known as macrofungi,
which are the ones big enough to see and describe with the naked eye. Even so,
a hand lens is very useful for examining features, and a dentist's
mirror handy for looking at the undersides of mushroom caps.
Most fungi of interest to the amateur are of the typical mushroom shape,
with a stalk sticking out of the ground, and with a cap on top. But these
are not the only kinds you might see on a fungus foray. There are jelly
fungi, such as Tremella or Heterotextus, easily recognised
because they look like jelly. There are earth stars and puff balls, which
look like little golf balls with a hole in the top, and there are
the stinkhorns, such as Anthurus archeri, which don't have a cap
or gills, but do have a nauseating smell.
But, if your unknown fungus is of the mushroom type, here are the kinds
of things we need to know before it can be identified:
- What shape is the cap (pileus)? What colour is it?
- Does it have gills? What colour are they, and how are they attached ?
- If it doesn't have gills, are there pores or spines under the cap?
- What is the colour of the stipe (stem)? Does it have a volva or ring?
Does it attach centrally to the cap, or off to one side?
- What is the colour of the spore print?
- Does the stem (stipe) discolour when broken? Does it exude latex?
Cole, Fuhrer, and Holland (1978) recommend the following procedure:
Using a hand lens:
- First determine whether or not the gills are attached to the stem.
You will probably need the lens to look at the point of gill
attachment to the stem, or break the cap away from the stem to see.
- Determine the spore colour. A spore print is essential, but you
may get a preliminary idea by looking along the gills, veil
or ring with a hand lens.
- Work through the dichotomous key by comparing the choices ('ring'
vs 'no ring').
- Eventually you will be led to a genus (e.g. Russula).
- Compare your specimen with the photographs, diagrams or descriptions
given in your references.
- There are several errors you may make at first. These are (a) whether
the gills are attached or free in some specimens; (b) whether gill
attachment is short-decurrent, adnexed, etc.; (c) if cap shape is
campanulate or umbonate expanding into a flat shape in older specimens.
The pileus or cap
The pileus can have a variety of shapes. Here are a few:
from Cole, M., Fuhrer, B. and Holland, A. (1978) A Field Companion to the Common Genera of Gilled Fungi in
Australia. Inkata Press, Melbourne
Gill attachment
If there are gills, how are they attached to the stem? The first thing to
work out is whether the gills are "free" (i.e. not attached to the
stem at all, or attached. The easiest way to see this is to slice along
the stem, through the cap, preferably between the gills. If they are
attached, they may be wavy (sinuate), they may extend down the stem
(decurrent), or they may be adnate (attached to the stem for their
total width). Here is what some of those attachment types look like.
from Cole, M., Fuhrer, B. and Holland, A. (1978) A Field Companion to the Common Genera of Gilled Fungi in
Australia. Inkata Press, Melbourne
Spore colour
The best way to find out the spore colour is to make a spore print.
Herte's how you do one:
- Place the cap (or a piece of cap) gills down on a piece of paper.
- Cover it with a container and leave for 2-3 hours
The gills will drop enough spores to give you a coloured print. Of course,
if the spore print is white and you use white paper, it may be hard to see.
Some people use acetate so they can change the background colour.
Last modified on 7 August 2003
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