For some time we have been looking at the order Agaricales. In this tutorial,
we will be discussing a number of additional families within Agaricales,
including Pleurotaceae, Pluteaceae, Hygrophoraceae, Clavariaceae
and Physalacriaceae, as well as a species within the genus Schizophyllum.
First, we will discuss a single species, Schizophyllum commune or the split gill fungus.
This mushroom can be found on all continents, so the species epithet, commune, represents
our shared relationship with this mushroom. This one to four centimeter-long mushroom resembles an
oyster and hangs off rotting wood. The underside has structures that resemble gills,
but upon further investigation, they turn out to be folds in the mushroom's surface. As discussed
in the tutorial on the basidiomycete life cycle, fungi sexually reproduce via the fusion of hyphae.
This fusion, called plasmogamy, depends on genetic differences at two genetic loci,
locus A and locus B. Schizophyllum commune is unique because the fungus has 223 alleles at
Locus A and 81 alleles at Locus B. If there is a single difference between any of these alleles,
the two fungal individuals will be able to mate sexually. With all of these potential matches,
mycologists have defined the number of unique sexes to be over 22,000 in Schizophyllum commune.
Let’s begin discussing two species in the same family, Physalacriaceae. The first is Flammulina
velutipes, commonly known as the velvet shank. You may have seen spindly white clusters called
enoki in stores. This is the cultivated version of Flammulina velutipes. Grown in the dark and
in a CO2-rich environment, the mushrooms form this spindly shape and white color.
Enoki mushrooms are a popular ingredient in soups, especially in Asian cuisine. In nature,
Flammulina velutipes mushrooms look quite different. The mushrooms have a sticky, brown cap.
They grow on stumps, roots, and logs of hardwood trees in late fall to winter. The mushroom’s
stipe is a dark brown color with a velvety soft texture, hence the common name velvet shank.
Next in the family Physalacriaceae, we will discuss the genus Armillaria. Commonly known as
honey mushrooms, they grow in clusters on conifers and hardwoods. Growing on a healthy tree can be
a good edible fungus, but there have been reports of gastric distress after eating these mushrooms.
So cook these mushrooms well before trying them. Along with this, be sure only to eat a
small amount if it is your first time eating any mushroom species. Everyone has a unique stomach,
so this should limit any adverse reaction you may have after eating. Besides Armillaria
mushrooms’ potential use as an ingredient for a meal, it acts as a plant pathogen to
trees and forests worldwide. They can be quite debilitating to an ecosystem because of their
mechanism of colonization and effective dispersal strategies. Armillaria is a white-rot fungus,
so it decomposes the brown lignin in wood, leaving only the white cellulose. It will
begin decomposing the wood of a living tree and kill it before the mycelium has fully spread.
It kills the tree by either causing extreme root damage or girdling the tree, which destroys the
bark along the entire circumference of the tree. In addition to Armillaria’s ability to quickly
kill their host, they have a dispersal strategy using unique structures. Many gilled mushrooms
have wind-dispersed spores that, when in good conditions, will produce hyphae from their
apical germ pore. Armillaria mushrooms also have wind-dispersed spores, but these spores contribute
little to this fungus’ ability to spread as a forest pathogen. They produce rhizomorphs,
meaning root-like structures. Rhizomorphs, also known as mycelial cords, are thick
aggregates of hyphae that spread slowly underneath the soil, inside the bark of trees, or in the air.
The cords have four tissue layers. The outermost layer at growing points of the cord consists of a
gelatinous sheath. Inner to the gelatinous layer is a melanized layer, which protects the cord
from bacteria and other fungi. It also possesses the molecule melanin, which protects the tissue
from damage due to ultraviolet radiation. Inner to the melanized layer is the medulla, which conducts
water and dissolved nutrients. The innermost layer is the central line that transports air.
Rhizomorphs are sturdy structures and can survive harsh weather conditions, which allow a long-term
spread of an individual honey mushroom. One individual from the species Armillaria ostoyae,
commonly called the humongous fungus, has colonized over 770 hectares, or 7.7 square
kilometers, and weighs over 440 tons, making it one of the largest recorded organisms.
Now we will transition to mushrooms in the family Hygrophoraceae. Mushrooms in this
family are commonly called waxy caps because many species have thick, waxy gills, and often waxy or
slimy caps. All mushrooms in the family have white spore prints. We will discuss three genera in this
family: Hygrocybe, Hygrophorus, and Gliophorus. Hygrocybe mushrooms are small mushrooms
with convex caps that are often brightly colored in shades of red, orange, or yellow.
Most Hygrocybe species are mycorrhizal with plant roots. A notable species is Hygrocybe conica,
commonly known as the witch’s hat. This mushroom has a bright red/orange cap and yellow stipe,
but when damaged or bruised, it blackens in color. Mushrooms in the genus Hygrophorus, commonly
called wood-waxes, are medium-sized mushrooms with slimy dull-colored caps. You will find these
mushrooms on the ground and they are mycorrhizal with various conifers and hardwood trees.
The type species for the genus is Hygrophorus eburneus, commonly called the ivory waxycap.
These are edible mushrooms that are entirely white, have very slimy caps when wet,
and some fungicidal and bacteriocidal chemicals have been isolated from the mushroom.
Lastly, from the family Hygrophoraceae, we will discuss the genus Gliophorus,
particularly the species Gliophorus psittacinus, commonly called the parrot mushroom because of
its bright green and red color. It can be found around the world and is quite slimy when young.
Gliophorus psittacinus can be an indicator of grassland health, appearing in yards after
years of low nutrients in the soil. The genus Gliophorus was originally part of Hygrocybe,
but developments in genetics elevated these types of mushrooms to their own genus.
Our next family, the Pleurotaceae, comprises mushrooms that are white-rot fungi
saprobic on wood and have white spore prints. Within this family, the genus Pleurotus consists
of mushrooms that generally form clusters along the trunk of a tree. The greek origin of Pleurotus
stems from “pleur” which means side and “ot” which means ear. Pleurotus mushrooms have
stipes that form laterally along the trunk and are commonly called oyster mushrooms. A classically
cultivated and foraged Pleurotus species is Pleurotus ostreatus or the gray oyster mushroom.
You can likely find this species sold at stores or markets that have a mushroom selection larger than
just Agaricus bisporus or the cremini, portobello, and button mushrooms. In addition, there are a
number of other cultivated oyster mushrooms, such as Pleurotus eryngii or the king oyster mushroom.
A similar family genetically to Pleurotaceae is Pluteaceae, containing pink to brown spored
mushrooms with free gills and saprobic on wood. Although mushrooms in the family Entolomataceae
also have pink spores, under a microscope, these mushrooms have smooth and round spores
compared to Entolomataceae’s ridged spores. Generally, Pluteaceae is split into two genera,
Pluteus and Volvariella. Pluteus mushrooms are known to have a smell and taste resembling radish.
A classic species is Pluteus cervinus, commonly called the deer mushroom. You will find this
mushroom decaying logs, tree stumps, and roots. The mushroom is edible and has a gray to brownish
cap with a white stipe. Volvariella species are not common and are generally entirely white,
resembling species in the Amanitaceae family because of the sac-like structure at the base
of the stipe called a volva. We will discuss the Amanitaceae family in depth in the next tutorial.
The last family in this tutorial will be Clavariacaeae, commonly known as coral fungi.
There are a number of genera in the family, but let us focus on the genus Clavaria. Fungi in
the genus Clavaria produce fruiting bodies forming club or coral-shaped clusters. You will find these
saprobic mushrooms decomposing leaf litter and other organic material on the forest floor.
Clavaria vermicularis, commonly called fairy fingers, is the type species of the family.
The species forms clusters of fragile white clubs that are fused at the base
of the cluster. Clavaria vermicularis has been recorded in five continents. In Great Britain,
the species is common in old grasslands and along the forest floor in North America.
Now let’s move forward and wrap things up with Agaricales.