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A Natural History Lexicon: Mycelium

Welcome to Wingtrip’s Natural History Lexicon, a regular rundown of natural history terms. To find future and past posts on this subject, simply search “natural history lexicon” or find it in the tags. Thanks for reading!

Mycelium –

\mahy-see-lee-uh m\

-the mass of hyphae that form the vegetative part of a fungus.

Picking across the tumbledown forest floor surrounding my home, I stumbled over a branch slowly becoming one with the soil and accidentally kicked it loose from its earthen cradle. Next to it were a smattering of small white mushrooms, nothing visually remarkable in a moment in space and time where fungi are obvious and abundant. However, in dislodging this rotten branch I revealed what was below these mushrooms. A twisting cobweb of white tendrils looked as if it could be plant roots or unrelated mold, but the closeness was too coincidental. This was mycelium of the mushrooms above.

We see mushrooms frequently, various species grow in cities and wild spaces equally well. Mostly we don’t consider that they are just a small section of a greater fungal body. A mushroom after-all is just the fruiting, reproductive arm of the organism. Beneath the surface, be that soil, leaf litter, or wood, is the part of a fungus that does the bulk of the work. All fungi are heterotrophs, meaning they cannot fix their own carbon and make a life out of breaking down dead or decaying organic material into sustenance. In some sense the mycelium does what the roots of any plant would do, except once ephemeral mushrooms decay, mycelium is all that persists.

For our purposes we should know that collectively the branching filaments known as hyphae make up mycelium. They grow and spread in and around any porous matter they set their sights, on secreting enzymes to break them down. Once broken into smaller pieces, they are absorbed by diffusion through the hyphae.

Their role in decomposition is vital. We don’t notice it, but they and other detritovores are constantly breaking down the plant matter all around us (mycelium is also a great source of food for many invertebrates). Without them we’d be piled high with leaves, wood, and other plant matter (while there are fungus that have colonized constantly freezing or dry environments, fungi appreciate moisture and don’t do well without it, partially why a wooden building lasts much longer in the desert than in the rainforest).

Equally important are the mutualistic role of many myceilium with plants. The vast majority of the plants we know have mycorrhizal association with fungi, wherein the roots of the plant form links with mycelium. Generally the fungi benefit from the carbohydrates a plant creates through photosynthesis and the plants gain better mineral and water absorption. Mycelium are much smaller in diameter than most roots and can explore a greater surface area as a result. Mycorrhiza have also been noted for creating structures that house nitrogen fixing bacteria, a benefit to plants that may live in or expand into nitrogen poor soils. There’s also much evidence they protect plants from pathogens.

As there are people who explore any number of corners of the natural world, there are mycologists, the people who study fungi. I myself am not so disposed, so when I look at fungi, be it mushroom or mycelium I’ve accidentally exposed, I look more out of wonder and curiosity and questions than understanding or the ability to identify. However, that, if I may say so myself is the mark of a good naturalist: infinite curiosity, and sometimes a light touch. So, I replaced the branch as best I could and continued on, trampling who knows what else as I passed.

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