Dr. Robert Norman, Clinical Professor, Dermatology, Nova Southeastern University
Depending on the size, shape, and composition, what are these called?
1. Bracket fungi
2. Shelf fungi
3. Woody shelves
5. All of the above
Answer = 5. All of the above
What is Shelf Fungi?
These fungi make shelves or brackets to produce spores above the ground. They are known as polypores (many pores) because the spore-producing cells line pores. The pores make them different than many mushrooms. They also differ in not having a stem or only a short lateral stem. The boletes are the only mushrooms having pores instead of gills. The boletes have central stems and a fleshy texture.
Shelf fungi are woody, leathery, or fleshy. If fleshy, they do not have a central stem. Their pores range in size from tiny to large and are the same size within a species. Basidia, spore-producing cells, line the walls of the pores. The spores have to drop down the pore into the air without sticking to the sides. The pores, as a result, are perfectly vertical. Occasionally, a shelf will continue to grow after a tree leans or falls.
The new pores will be vertical, but at an angle to the old pores. Woody shelves that resemble horse’s hoofs are called “conks”. The confusion caused by all of these names is the reason scientists use scientific names. A scientific name is only used once for one species.
Woody shelves may be several years old. They add a new layer of spore tissue every growing season. The old layer is covered by the new one. These layers look like growth rings in a tree. One author reported counting 37 rings. Ten layers may mean the shelf is 10 years-old if there is only one growing season (spring). If there are two growing seasons per year (spring and fall), it may only be 5 years-old.
One of the largest shelves weighs 300 pounds. Unfortunately, it isn’t known how many growth layers it contains. Woody shelves are a micro (small) habitat. They provide a unique place for animals to live. Spiders, mites, and insects live in large shelves. A few of the insects are specialized and only found in shelf fungi.Some beetles are very slim so they can fit inside a pore. They hide in a pore and eat spores. There are enough insects and other animals that a food web is created. The spiders and some insects are predators that feed on other insects. Their prey includes fly larvae and small insects.
Woody shelves are impossible to break with your hands and difficult to cut. This toughness results from the kinds of hyphae (filaments) that are used to construct the shelf. Easily crushed mushrooms are made of thin-walled hyphae. Some of the hyphae in woody shelves are thick-walled and the hyphae are interwoven making them tougher.
They resist tearing or splitting because there are no planes to split along in the tissue.
Artists use shelf fungi to make etchings and beads. The pore surface of the Artist’s Conk, Ganoderma applanatum, changes color when bruised. A nail produces broad lines and sharp needles produce very fine lines. An intricate etching takes great patience and time. Beads are made by carving large shelves much like you would a block of wood.
Shelf fungi are used as herbal medicines. A bag on the body of the 5,300 year-old Ice Man mummy contained pieces of Piptoporus betulinus. This shelf fungus when eaten causes diarrhea. He probably carried it to control a whipworm infection in his colon. The reishi or Ling Chi shelf fungus, Ganoderma lucidum, is a traditional Asian medicine.
Tree bracket fungus is often referred to as shelf fungus because of the way it sticks out from the infected tree. They are called polypores. Instead of having spore producing gills, they have many pores lined with spore producing cells called basidia. These basidia form woody tubes through which the spores are released into the air.
A new layer of spore tissue is added each season on top of the old; and as time passes, these layers grow into the large and familiar bracket. The rings can give clues to the age of the growth because each ring represents one growing season, but before that can be determined, one needs to know if there is only one growing season per year in the spring or two seasons, one in spring and one in fall. Depending on the number of seasons, a tree bracket fungus with twenty rings may be twenty years old or only ten.
There have been reports of shelves with forty rings and weights up to three hundred pounds. As long as the host plant survives, the shelf will continue to grow, so the simplest answer to how long does bracket fungus live is — as long as the tree it infects.
Tree bracket fungus is a disease of the tree’s heartwood. As stated before, the shelves are the fruiting bodies and by the time they appear, there is usually a significant amount of interior damage. The fungi that cause bracket fungus — and there are many — attack the hardwood interior, and therefore, the structural integrity of the tree and are the cause of white or brown rot. If the rot occurs in a branch, it will weaken and eventually drop. If the disease attacks the trunk, the tree can fall. In older trees with massive trunks, this decay can take years.
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