As we now know, mycology is the study of the fungi kingdom.
Fungi differ significantly in their size and shape, from tiny single-celled yeasts to the
largest living organism on Earth, the honey mushroom.
And within this kingdom, the most familiar organisms are certainly the wide variety of
mushrooms that exist.
Given the incredible diversity of mushroom species, it is crucial to know the general
structure of a mushroom in order to accurately identify a species when encountered.
For this reason, the best way to begin our study will be to discuss the morphology, or
structure, of a mushroom.
Here is a beautiful bright orange and red mushroom species, Amanita jacksonii.
The European variety is commonly known as Caesar’s mushroom because it was enjoyed
by Roman Emperors.
However, it can be confused with many poisonous fungi.
We are currently looking at the fruiting body, or the sporocarp, of this mushroom.
The fruiting body accounts for the reproductive function of a fungus and can vary significantly
between fungal species.
When you see a mushroom in the wild, or even in a market, you are looking at the fruiting
body, while you only see a small portion of the actual fungus.
Underneath the soil, there is a filamentous network that supports the fungus.
These filaments consist of thin fibers called hyphae, and the collective network of hyphae
is known as the mycelium.
The mycelium allows for nutrient acquisition, growth of the fungus, and production of the
fruiting body.
Many mushrooms form a symbiotic relationship between the mycelium and plant roots called
mycorrhizae, as we touched upon in the botany series, with myco meaning mushroom and rhiza
or rhizo meaning root.
Mycorrhizae represent an amazing interaction that allows for the growth and life of many
plants and mushrooms.
Now, although some fungi can be beneficial for the organisms they interact with, some
mushrooms retrieve nutrients through the breakdown of other living organisms.
This is known as a parasitic relationship.
For example, these are cordyceps fungi that have infected and killed these insects.
However, not all fungi have their mycelia networked with living organisms.
Fungi that decay dead organic matter such as leaf litter or rotting wood are known as
saprobic fungi.
Let’s return to Amanita jacksonii.
Any fruiting body of a mushroom is formed from dense bunches of hyphae.
When a mycologist looks at a mushroom fruiting body, they look at the presence of or lack
of different characteristics of the structure in hopes of identifying the species.
The top portion of the mushroom is called the pileus or the cap.
On the underside of the pileus, there are thin ribbon-like projections called lamellae
or gills.
The lamellae are the site of spore production for this specific fungus.
However, many other mushroom varieties have different structures that act as the site
of spore production.
We call the tissue layer of spore production in a fungus, the hymenium.
The spores in a fruiting body allow for sexual reproduction of the fungus.
This part holding the pileus or cap is called the stipe or the stalk.
At the base of the mushroom, there is a white cup encasing the stipe.
This is called the volva or universal veil.
The universal veil houses the immature fruiting bodies of mushrooms.
As you can see here, the maturing mushroom sprouts from the universal veil.
The ring of tissue below the cap and gills is called the annulus or partial veil.
It covers the hymenium throughout development and then detaches from the hymenium once the
fruiting body matures.
When identifying mushrooms, many of these traits can be of assistance in identifying
species.
Let us use our new knowledge of these structural components to identify another mushroom.
This mushroom’s cap is white and smooth.
It has white gills on the cap’s underside.
The stipe is white, and a partial veil is present.
At the base of the stalk, a white universal veil is present.
A mushroom with these characteristics can only be one thing, the death angel, Amanita
bisporigera.
The death angel is an extremely deadly mushroom that produces a poison called amatoxin that
causes liver failure if ingested.
Many mushrooms within the Genus Amanita produce amatoxin.
In general, if the mushroom has gills, a partial veil, and a universal veil, it is likely a
species from the Amanita genus.
When trying to identify any mushroom, we look at structural traits such as the cap, stipe,
and gills.
There are variations to each of these structures, and many of these variations have descriptions
that are outlined in any mushroom identification resource.
But these macroscopic features of a mushroom can only get you so far in mushroom identification.
Many mushrooms require the observation of microscopic features to be accurately described.
Mycologists will look at the gills or other spore producing structures to see the hyphal
tissue called the trama, the spore-producing cells, and the spore shape and size in order
to accurately identify a species.
Naturally, this process requires a microscope.
However, an easy method to assist in the identification of mushrooms is to create a spore print.
By placing a mushroom with the gills faced down on a piece of printer paper, aluminum
foil, or wax paper, the spores will be released from the mushroom cap and fall onto the surface
of the paper.
This produces the spore print which shows the color of the spores.
The spore color can be a key identifying trait that is especially useful when searching for
edible or medicinal mushrooms.
Not all fruiting bodies of fungi have a spore-producing structure that forms gills.
We call any spore-bearing structure, or hymenium bearing structure, the hymenophore.
So, Amanita jacksonii, being a gilled mushroom, would have a lamellate hymenophore.
Boletus edulis, or the porcini mushroom, forms spongy pores on the cap’s underside instead
of gills, so mycologists describe its hymephore as tubular.
Many shelf fungi or polypores have a hymenophore that forms into pores on the underside of
the cap.
This is the reishi mushroom from the genus Ganoderma.
It is considered a polypore mushroom and is also considered a medicinal fungus.
Puffballs have their hymenium inside the fruiting body, and the hymenium is not exposed to air.
So, as we can see, mushrooms are incredibly diverse.
And as we move through this series, we will continue to highlight some remarkable features
that will help us understand this kingdom as a whole, so let’s move forward and examine
fungal phylogeny and taxonomy next.