What are Fungi?

The Hidden Kingdom

Fungi are not plants. Living things are organized for study into large, basic groups called kingdoms. Fungi were listed in the Plant Kingdom for many years. Then scientists learned that fungi show a closer relation to animals, but are unique and separate life forms. Now, Fungi are placed in their own Kingdom.

It is a hidden kingdom. The part of the fungus that we see is only the fruit of the organism. The living body of the fungus is a mycelium made out of a web of tiny filaments called hyphae. The mycelium is usually hidden in the soil, in wood, or another food source. A mycelium may fill a single ant, or cover many acres. The branching hyphae can add over a half mile (1 km) of total length to the mycelium each day. These webs live unseen until they develop mushrooms, puffballs, truffles, brackets, cups, birds nests, corals or other fruiting bodies. If the mycelium produces microscopic fruiting bodies, people may never notice the fungus.

Kingdoms of Organisms Chart, Plantae, Anamalia, Fungi, Protista (Protozoans), and Monera (Bacteria)

Most fungi build their cell walls out of chitin. This is the same material as the hard outer shells of insects and other arthropods. Plants do not make chitin. Fungi feed by absorbing nutrients from the organic material in which they live. Fungi do not have stomachs. They must digest their food before it can pass through the cell wall into the hyphae. Hyphae secrete acids and enzymes that break the surrounding organic material down into simple molecules they can easily absorb.

Fungi have evolved to use a lot of different items for food. Some are decomposers living on dead organic material like leaves. Some fungi cause diseases by using living organisms for food. These fungi infect plants, animals and even other fungi. Athletes foot and ringworm are two fungal diseases in humans. The mycorrhizal fungi live as partners with plants. They provide mineral nutrients to the plant in exchange for carbohydrates or other chemicals fungi cannot manufacture.

You probably use fungal products every day without being aware of it. People eat mushrooms of all shapes, sizes and colors. Yeasts are used in making bread, wine, beer and solvents. Drugs made from fungi cure diseases and stop the rejection of transplanted hearts and other organs. Fungi are also grown in large vats to produce flavorings for cooking, vitamins and enzymes for removing stains.


  • Hyphae (hí - fee) plural: the threads that form the body of a fungus. (singular: mycelium)
  • Mycorrhiza (my - koh - rý - zuh) singular; mycorrhizae (my - koh - rý - zee) plural: a beneficial combination between a fungus and a living plant root.
  • Symbiosis (sim - by - óh - sis) singular; symbioses (sim - by - óh - sees) plural: a partnership formed between two living organisms.
Morel Mushrooms in the Grass