I started this site because I wanted honest answers about mushrooms and could not find them. What I kept running into, over and over, was that almost no consumer content about mushrooms explains what a fungus actually is. People buy lion’s mane supplements without knowing that the “mushroom” is just the fruiting body, not the organism. People grow oyster mushrooms at home without knowing that the white fuzz on their substrate is the actual fungus. People ask whether mold is dangerous without knowing that mold and mushrooms are the same kind of organism in different costumes.

This is the post I wish I had read first. It is long. It has citations. It does not try to make fungi seem cooler than they are, because fungi are already staggering. You just have to know what you are looking at.

The five things that define a fungus

If you want a single working definition, use this one. A fungus is an organism with all five of the following traits:

1. Eukaryotic cells. Each cell has a nucleus and membrane-bound organelles, just like plant and animal cells. This puts fungi in the same broad category as every other visible life form on Earth and rules out bacteria (which are prokaryotic).
2. Chitin cell walls. Fungal cells are surrounded by a rigid wall made primarily of chitin, the same compound found in the exoskeletons of insects and crustaceans [3]. Plants use cellulose. Animals do not have cell walls at all. Chitin is the single most important structural feature that separates fungi from every other kingdom.
3. External digestion. Fungi do not have mouths or digestive tracts. They release enzymes into their environment, break complex molecules down outside their bodies, and absorb the resulting small sugars and amino acids across their cell walls. This is called osmotrophy, and it is why a fungus growing on a log is literally melting the log into food.
4. Reproduction via spores. Fungi produce vast quantities of microscopic spores, typically released from a fruiting body, that are carried by air, water, or animals to new locations. A single oyster mushroom can release a billion spores in its lifetime [4]. Almost none will germinate. The ones that do become new organisms.
5. No photosynthesis. Fungi cannot make their own food from sunlight. They have to find already-living or once-living organic matter to feed on. This makes every fungus a consumer in the ecological sense, the same role filled by animals.

Any organism with all five of those traits is a fungus. Any organism missing one or more is something else, even if it looks like a fungus. This is going to matter later when we get to slime molds.

Fungi are not plants

This is the single most persistent myth about fungi, and it traces back to how Western biology was first organized. Linnaeus, in the 1735 Systema Naturae, placed fungi in the plant kingdom because they seemed to grow out of the ground, did not move, and did not have obvious animal parts. This classification stuck for over two hundred years, which is why you will still see fungi taught in “botany” courses at some universities, and why mushroom identification guides were historically written by botanists.

The problem is that fungi are not plants at a single level of biology. They do not photosynthesize. Their cell walls are made of chitin, not cellulose. They do not have chlorophyll, xylem, or phloem. They do not produce seeds. Their reproductive cells are not pollen. At the biochemical level, fungal cells are substantially different from plant cells in how they process energy, how they grow, and how they reproduce.

The scientific community formally moved fungi out of the plant kingdom in stages. Robert Whittaker’s 1969 five-kingdom system was the first widely accepted classification to give fungi their own kingdom. Molecular phylogenetic work in the 1990s confirmed the separation and went further, establishing that fungi are genetically much closer to animals than to plants [5].

Fungi are the closest living relatives of animals

This is the part most people find genuinely hard to accept.

In 1993, Sandra Baldauf and Jeffrey Palmer published a paper in the Proceedings of the National Academy of Sciences titled “Animals and fungi are each other’s closest relatives” [5]. Using protein sequences that were highly conserved across all eukaryotes, they showed that fungi and animals share a more recent common ancestor than fungi and plants do. A roughly 12-amino-acid insertion in the elongation factor 1-alpha gene is present in all fungi and all animals and absent from everything else. It is a molecular fingerprint of shared ancestry.

This relationship has been confirmed by every subsequent large-scale phylogenetic analysis [6][7]. Animals and fungi are now grouped together in a clade called Opisthokonta, which literally means “rear-propelled” and refers to the fact that the swimming reproductive cells of primitive fungi and the sperm cells of animals both have a single posterior flagellum. Plants, and the algae that gave rise to them, swim with flagella at the front end.

The Opisthokont grouping has held up under every subsequent test. When researchers look at the full genomes of fungi, animals, and their closest single-celled relatives, the same sister relationship keeps emerging. The closest known single-celled relatives of fungi are a group of amoeba-like organisms called nucleariids and a single described species called Fonticula alba. The closest known single-celled relatives of animals are the choanoflagellates, which have a striking morphological resemblance to the collar cells in sponges. Somewhere between one and two billion years ago, a common ancestor of fungi and animals split into two lineages. One lineage stayed mostly single-celled for hundreds of millions of years before giving rise to animals. The other followed a separate path and gave rise to the fungi.

So if you are eating a mushroom, you are eating something more closely related to you than it is to the lettuce on your plate.

I know. It takes a minute.

The shared ancestry goes deeper than a single genetic marker. Animals and fungi both use chitin as a structural biopolymer, just in different places (cell walls for fungi, exoskeletons for insects and crustaceans, and fish scales and squid beaks for vertebrates and cephalopods). Both groups synthesize glycogen as their primary energy storage molecule. Plants use starch. Animals and fungi both rely on external food sources, neither group can photosynthesize, and both digest macromolecules into smaller absorbable units before using them for energy or building materials. The only fundamental difference in how animals and fungi eat is that animals bring food inside their bodies first, while fungi digest it externally and absorb the results.

When you look at the molecular phylogenetic trees built from hundreds of conserved proteins, the split between fungi and animals happened after the split between the fungi-animal lineage and the plant-algae lineage. In tree form, that means plants are a distant cousin, and fungi are your sibling. Your most recent shared ancestor with a mushroom lived roughly 1.1 billion years ago. Your most recent shared ancestor with a rose bush lived over 1.6 billion years ago.

For a deeper look at how fungi compare to plants and animals at the cellular and biochemical level, I wrote a dedicated piece: The Fungi Kingdom: How It Differs From Plants and Animals. That is where I unpack the chitin versus cellulose comparison and the metabolism differences in more detail.

How old are fungi?

Older than most people realize. Possibly older than almost anything else complex.

The oldest fossils currently accepted as fungi were described in a 2019 Nature paper by Corentin Loron and colleagues [8]. The fossils came from the Grassy Bay Formation in Arctic Canada and date to between 0.9 and 1.0 billion years ago, pushing the fungal fossil record back by more than half a billion years. The species, named Ourasphaira giraldae, shows the characteristic branching filaments and chitin-walled spheres of a true fungus.

To put that in context: a billion years ago, there were no land plants, no animals larger than a single cell, and very little oxygen in the atmosphere compared to today. Whatever Ourasphaira was doing, it was doing it alone.

Molecular clock estimates, which use the accumulated mutation rate between modern species to back-calculate when lineages diverged, had previously suggested fungi originated somewhere between 760 million and 1.06 billion years ago. The Ourasphaira fossil falls right in that window and provides physical evidence for what the genetic math was already predicting.

The practical implication is that fungi were probably the first multicellular eukaryotes to colonize land. Plants followed later, around 450 million years ago, and most research now suggests plants could not have succeeded on land without fungal partners to help their root systems access nutrients from soil.

The body of a fungus is not the mushroom

The mushroom you pull out of the ground, or the oyster you cut from a grow bag, is not the organism. It is a reproductive structure. The actual organism is the mycelium, a vast network of microscopic threads called hyphae that spread through soil, wood, or any other substrate the fungus has colonized.

A single mushroom might weigh a few ounces. The mycelium that produced it can weigh hundreds of pounds and cover acres.

The largest known living organism on Earth is a fungus for exactly this reason. A single colony of Armillaria ostoyae in the Malheur National Forest in eastern Oregon covers 3.7 square miles and is estimated to be between 2,400 and 8,650 years old. I wrote about it here: Armillaria: The Largest Living Organism on Earth Is a Fungus. It is one of the clearest demonstrations of what a fungus actually is, because once you grasp that the visible mushrooms are just seasonal reproductive flushes from a vast underground network, a lot of other things about fungi start making sense.

Hyphae grow by extending at their tips, branching outward into whatever material they are digesting, and secreting enzymes ahead of themselves to break down what they find. The feeding happens externally. The absorbed nutrients flow back through the hyphal network to wherever they are needed. When the mycelium has accumulated enough energy and encounters the right environmental conditions, usually a drop in temperature combined with moisture and light, it forms a fruiting body. That is what we eat.

For the full biology of this process, from single spore to fruiting body, the dedicated deep-dive is here: How Do Mushrooms Grow? From Spore to Fruiting Body Explained. What I cover below is the high-level life cycle, with the full sequence shown in the interactive block in the next section.

The fungal life cycle: spore to spore

Every fungal life cycle follows the same basic sequence. The details vary between species, but the pattern is universal.

1. Spore release. A mature fruiting body releases spores into the environment. Most species produce enormous numbers. A single mature Agaricus bisporus (the common white button mushroom) releases about 16 billion spores over several days of peak fruiting [9]. Spore release is not passive. Basidiomycete fungi use a surface tension mechanism: a water droplet forms at the base of each spore, then suddenly fuses with a larger film, and the resulting recoil launches the spore off the basidium at roughly one meter per second. This happens millions of times per hour across a mature mushroom’s gill surface, and the coordinated puff of released spores is occasionally visible as a faint cloud rising from a mushroom cap in still air. Ascomycete fungi use a different mechanism, building up internal pressure inside the ascus until it ruptures explosively and shoots spores out.

2. Dispersal. Spores are carried by air currents, water, insects, or animal fur. They are small, light, and resistant to drying out and temperature extremes. Some spores can remain viable for decades. Fungal spores have been found in upper atmosphere samples at altitudes over 10 kilometers, carried by storm systems across oceans. This is partly why fungi are so widely distributed. If you leave a slice of bread out in almost any environment in the world, something will colonize it within days. The spores were already in the air.

3. Germination. When a spore lands on suitable substrate with the right moisture and temperature, its outer wall softens and a germ tube emerges. This is the first hypha. The spore has just become a fungus.

4. Mycelial colonization. The germ tube grows, branches, and spreads through the substrate. Within days, a single spore has become a three-dimensional network of hyphae extending in all directions. The fungus is now feeding by secreting enzymes into the substrate and absorbing the products.

5. Mating. Most fungi are heterothallic, meaning they require two genetically compatible mycelia to meet before reproduction can begin. When compatible hyphae from different spores encounter each other, they fuse, and the resulting dikaryotic mycelium (carrying nuclei from both parents) can eventually produce fruiting bodies.

6. Fruiting body formation. When conditions trigger reproduction, the mycelium concentrates energy at specific points, forms a dense knot of hyphae called a primordium, and begins developing a fruiting body. This is where the visible mushroom, bracket, or cup comes from.

7. Spore production and release. The fruiting body produces new spores, usually in specialized tissue (gills, pores, teeth, or asci depending on the species), and releases them into the environment. The cycle begins again.

A single complete cycle can take anywhere from a few weeks (for fast-growing species like oysters) to decades (for long-lived wood decomposers like reishi). Some fungi produce fruiting bodies many times a year. Others flush once and never again.

The diversity within Kingdom Fungi

Here is where a lot of consumer content gets lazy. The word “fungi” does not mean one thing. It describes an enormous kingdom of organisms that range from single-celled yeasts to forest-floor networks larger than cities. The most recent comprehensive phylogenetic classification, led by David Hibbett and a large consortium of fungal taxonomists, recognizes at least 7 to 10 phyla within the kingdom [10][11].

The four you should know about:

Basidiomycota (the club fungi). This is where almost every mushroom you would recognize lives. Oyster mushrooms, lion’s mane, shiitake, reishi, turkey tail, chaga, psilocybin mushrooms, all of the common edibles and medicinals you read about on this site are basidiomycetes. They produce spores on specialized structures called basidia, usually lining the gills, pores, or teeth of a fruiting body. Basidiomycetes include most of the mushrooms that are visually striking: the coral fungi, puffballs, bracket fungi, stinkhorns, and jelly fungi are all in this phylum. Many of the most ecologically important wood-decomposers, including the white-rot fungi that recycle lignin, are basidiomycetes. The phylum contains roughly 30,000 described species and an estimated several times more undescribed ones.

Ascomycota (the sac fungi). The largest phylum by species count, with around 64,000 described species. Morels, truffles, and cup fungi are the familiar examples, but most of this phylum is microscopic: yeasts used in bread and beer, molds like Penicillium and Aspergillus, and many plant pathogens. Ascomycetes produce spores inside sac-like cells called asci, typically eight per sac, which are discharged into the air when the ascus matures. This phylum contains most of the economically important molds and fermentation organisms, most of the fungi that partner with algae to form lichens, and several pathogens with major agricultural impact (wheat rust, apple scab, coffee leaf rust). The medicinal and industrial footprint of Ascomycota is enormous, and the phylum is probably the most thoroughly studied group in Kingdom Fungi.

Zygomycota (the bread molds). A phylogenetically complex group that has been split and reorganized multiple times in recent classifications. The black mold you see on forgotten bread (Rhizopus stolonifer) is a zygomycete. They reproduce by forming tough-walled zygospores.

Chytridiomycota (the chytrids). Mostly aquatic or soil-dwelling. The only fungi whose reproductive cells have flagella and can actually swim, which is a holdover from an aquatic ancestor. One species, Batrachochytrium dendrobatidis, is responsible for a global amphibian pandemic that has driven multiple frog species to extinction [12].

Together, these four (plus several smaller phyla) make up Kingdom Fungi. The range of lifestyles within that kingdom is wider than you might expect. Some fungi are decomposers that break down dead wood. Some are plant partners that help trees access nutrients. Some are parasites that kill their hosts. Some live inside insects and control their behavior. Some produce antibiotics and statins. Some produce deadly toxins. All of them share the five defining traits from earlier, but almost nothing else.

Mushrooms, molds, yeasts, and lichens

Four words you see constantly when reading about fungi, often used interchangeably by people who should not be using them interchangeably. Here is what each one actually means.

Mushroom. A fleshy, above-ground fruiting body produced by certain fungi, primarily in the Basidiomycota and Ascomycota. The word describes the structure, not the organism. Not every fungus produces mushrooms, and the ones that do spend most of their lives as mycelium underground. This is a big deal for consumer supplement buyers because a “mushroom extract” should be made from the actual mushroom (the fruiting body), not the underlying mycelium, which has a meaningfully different chemical profile. I have written about this distinction at length in the Consumer Guide: What Are Beta-Glucans? covers the compounds that differ between fruiting body and mycelium.

Mold. A catch-all term for fungi that grow as visible fuzzy or powdery colonies without forming large fruiting bodies. Most molds are ascomycetes or zygomycetes. The black fuzz on old bread, the green patches on citrus, the colorful spots on shower tile, these are all molds, and they are all fungi. Molds are not a distinct group within Kingdom Fungi. The word describes a growth habit, not a taxonomic category.

Yeast. Single-celled fungi, mostly ascomycetes. Saccharomyces cerevisiae (baker’s yeast, also used in brewing) is the canonical example. Candida species, some of which cause human infections, are also yeasts. A yeast is still a fungus with all five defining traits, it just happens to live its life as individual cells rather than forming a hyphal network.

Lichen. Not actually a single organism. Every lichen is a symbiotic partnership between a fungus and either a green alga, a cyanobacterium, or both. The fungus provides structure and protection. The photosynthetic partner provides sugars. Lichens can survive on bare rock, in deserts, and in Arctic conditions where nothing else lives, because the partnership extracts enough value from minimal resources to sustain both organisms. Recent research suggests that some lichens are actually three- or four-way partnerships involving multiple fungal and algal species [13].

Four words, four different things, one kingdom.

What is not a fungus

This is where classification gets politically interesting, because several organisms that look and act like fungi are not actually fungi at all. The most famous are slime molds.

Slime molds. Historically classified with fungi because they produce spore-releasing fruiting bodies and grow on decaying wood, slime molds have been conclusively reclassified out of Kingdom Fungi based on molecular evidence. They now belong to the supergroup Amoebozoa, which is more closely related to animals than to fungi [14]. A slime mold is essentially a giant, slow-moving amoeba (or in the case of cellular slime molds, a cooperative swarm of amoebas) that can solve mazes, optimize networks, and produce fruiting bodies without being a fungus in any meaningful sense. They are one of the strangest life forms on Earth and genuinely deserve their own post, which I plan to write: Slime Molds: Not Actually Fungi (And Why That Matters).

Oomycetes (water molds). These include Phytophthora infestans, the organism responsible for the Irish potato famine, and several other economically devastating plant pathogens. They superficially resemble fungi, grow as hyphal networks, and reproduce via spores, but their cell walls are made of cellulose (like plants) rather than chitin, and their genetic makeup places them with brown algae and diatoms in the stramenopiles. They are a convergent evolution story: something with no recent shared ancestry with fungi independently evolved a fungus-like lifestyle. I cover these in the planned mold deep dive: What Is Mold, Really?.

Actinomycetes. These are soil bacteria that grow as branching filaments and were historically confused with fungi. They are prokaryotes, without nuclei, and belong in Kingdom Bacteria. The name Streptomyces (a major source of antibiotics) is an actinomycete, not a fungus.

The general principle: if it looks like a fungus, check the five defining traits. Chitin cell walls, external digestion via enzyme secretion, no photosynthesis, reproduction via spores, eukaryotic cellular organization. If all five are present, it is a fungus. If any are missing, it is something else doing a convincing impression.

How many fungi are there, actually

The honest answer is that nobody knows, and the range of educated guesses is enormous.

The most influential estimate from the early 1990s put the number at 1.5 million species [15]. That figure dominated textbooks for a generation. But it was based on a ratio between known fungi and known plants in well-studied regions, applied globally. It did not account for the fungi that live inside insects, inside other fungi, in deep ocean sediments, in extreme environments, and in soil communities that had never been sequenced.

Meredith Blackwell’s 2011 paper “The fungi: 1, 2, 3… 5.1 million species?” used high-throughput environmental DNA sequencing to recalculate the estimate and suggested the true number could be as high as 5.1 million [1]. That number seemed shocking at the time. More recent work by Hawksworth and Lücking in 2017 landed on a range of 2.2 to 3.8 million [2], which has become the current consensus.

Whichever number is right, the implication is the same: we have formally described only a small fraction of the fungi that exist. Out of somewhere between 2 and 5 million species, only about 150,000 have names and descriptions in the scientific literature. Fungi outnumber described plants by at least 6 to 1, and probably more like 10 to 1.

Some of this is because fungi are small and hard to find. Some is because the field of mycology is relatively under-funded compared to botany and zoology. And some is because the tools to identify fungi without growing them in culture, primarily DNA sequencing from environmental samples, have only existed for about 25 years. Every year, environmental DNA surveys reveal large numbers of fungal sequences that do not match anything in any existing database. Many of these are new species, new genera, sometimes new orders or classes.

In other words: the tree of fungal life is still being drawn.

Why fungi matter

The ecological role of fungi is almost impossible to overstate. Three major functions, each worth unpacking.

Decomposition. Fungi, along with bacteria, are the primary decomposers in most terrestrial ecosystems. But they do something bacteria cannot. White-rot fungi can break down lignin, the tough, aromatic polymer that makes wood rigid and that essentially no other group of organisms on Earth can digest efficiently. Without lignin-degrading fungi, dead trees would pile up indefinitely. In fact, there is a strong paleontological argument that the Carboniferous period, the time 300-350 million years ago when enormous amounts of undecayed plant matter were buried to form the coal deposits we mine today, was partly a result of fungi not yet having evolved the full enzymatic toolkit to break down lignin. Once white-rot fungi expanded globally, the era of large coal deposits ended. The forest floor as we know it exists because fungi learned to eat wood.

Brown-rot fungi, by contrast, can only digest cellulose and hemicellulose, leaving the reddish-brown lignin residue behind. This is why rotting wood sometimes looks red and crumbly rather than pale and soft. Both strategies matter. Together, white-rot and brown-rot fungi recycle the largest reservoir of fixed carbon on land.

Mycorrhizal partnerships. Roughly 90% of all land plants form partnerships with fungi in their root systems [16]. These partnerships are ancient, predating the diversification of modern plant lineages, and there is growing evidence that the original transition of plants onto land around 470 million years ago depended on fungal partners. Without mycorrhizal fungi, the earliest land plants could not have extracted phosphorus from primitive soils.

The partnership works like this. The fungus extends hyphae far beyond the reach of the plant’s roots, sometimes hundreds of meters, absorbing phosphorus, nitrogen, and water from a much larger soil volume than the plant alone could access. In exchange, the plant provides the fungus with sugars from photosynthesis. Both partners benefit. Neither can reach their full potential alone.

The network is often shared between multiple plants. A mycorrhizal fungus connected to several trees can transfer nutrients between them, sometimes from older, established trees to younger seedlings that have not yet grown enough leaves to photosynthesize efficiently. This is the basis for the “wood wide web” concept, which has been popularized (sometimes over-popularized) in recent years. The science is real, though some of the dramatic claims about trees “communicating” through fungal networks are still debated.

When you buy quality potting mix or garden soil, one of the things you are paying for is an established mycorrhizal community. This is why freshly fumigated sterile potting mix often produces worse results than aged soil, even if nutrient content appears equal on paper.

Food, medicine, and industry. The commercial footprint of fungi is broader than most people realize.

Bread, beer, wine, sake, cider, kombucha, soy sauce, miso, tempeh, and many cheeses all depend on fungal fermentation. Saccharomyces cerevisiae (brewer’s and baker’s yeast) is probably the single most economically important microorganism in human history. Aspergillus oryzae, the mold used to ferment soy sauce and make sake, has been selectively cultivated for over a thousand years. Penicillium molds give bleu cheese and Camembert their distinctive flavors.

In medicine, the impact is hard to overstate. Penicillin, discovered by Alexander Fleming in 1928 from a contaminant Penicillium culture, was the first true antibiotic and fundamentally changed what survivable illness looks like. Cyclosporine, the immunosuppressant that made organ transplants viable, comes from the soil fungus Tolypocladium inflatum. Statins, the cholesterol-lowering drugs taken by tens of millions of people worldwide, were originally isolated from Aspergillus and Penicillium species. The antifungal drug griseofulvin, the antimalarial artemisinin’s production process, and countless other pharmaceuticals either come directly from fungi or rely on fungal fermentation for industrial-scale production.

Medicinal mushrooms (lion’s mane, reishi, cordyceps, turkey tail, chaga) are a separate category with a genuinely mixed evidence base. Some compounds, like turkey tail’s PSK, have decades of clinical research behind them. Others have strong traditional use histories but weaker modern evidence. The Consumer Guide on this site is built around how to tell the difference, starting with the Five-Step Framework.

And for home growers, fungi are uniquely rewarding to cultivate. They fruit fast, take up little space, and reward careful technique with visible results in weeks rather than months. If you want to start: How to Grow Mushrooms at Home: The Complete Beginner Guide.

What this means if you buy supplements, grow at home, or cook with mushrooms

Understanding what a fungus actually is changes several practical things.

For supplement buyers. The mushroom is the fruiting body. Most of the active compounds that clinical trials have studied (beta-glucans, triterpenes, hericenones, and others) are concentrated in the fruiting body, not the mycelium. A “mushroom supplement” that uses mycelium grown on grain is chemically a different product from one made from actual mushroom fruiting bodies. This is the single most important quality distinction in the supplement industry, and it is the one most brands work hardest to obscure. How to Read a Mushroom Supplement Label walks through the label red flags in detail.

For home growers. The white fuzz colonizing your substrate is the actual fungus. The mushrooms you harvest are the reproductive structures. That means the health and vigor of the underground mycelium determines everything about your grow, and most cultivation failures come from contamination or unhealthy mycelium before fruiting ever begins. Getting comfortable with what healthy mycelium looks like, how fast it should colonize, and what contamination looks like is more important than any specific technique. Mushroom Contamination: How to Identify, Prevent, and Deal With It covers the common failure modes.

For cooks and foragers. Mushrooms are foods, but they are foods with unusual properties. Their cell walls are made of chitin, which humans digest only partially, so the bioavailability of mushroom nutrients is lower than it appears on a nutrition label. Cooking mushrooms thoroughly breaks down chitin and improves digestibility. Some species contain compounds that are only safe once cooked (most commonly, hydrazines in raw morels). And spoilage in mushrooms looks different from spoilage in plant foods, because the organism that decomposes them is usually another fungus, not the same bacteria that spoil fruits and vegetables.

The underlying pattern across all three is the same. Once you know what a fungus actually is, you can make more informed decisions about what you buy, grow, and eat.

Frequently asked questions

References

[1] Blackwell M. The fungi: 1, 2, 3 … 5.1 million species? American Journal of Botany. 2011;98(3):426-438. PubMed

[2] Hawksworth DL, Lücking R. Fungal Diversity Revisited: 2.2 to 3.8 Million Species. Microbiology Spectrum. 2017;5(4). Journal

[3] Gooday GW. The dynamics of hyphal growth. Mycological Research. 1995;99:385-394. Comprehensive review of chitin synthesis in fungal cell walls.

[4] Buller AHR. Researches on Fungi, Volume II. Longmans, Green and Co.; 1922. Classical spore count measurements including Agaricus and Coprinus species.

[5] Baldauf SL, Palmer JD. Animals and fungi are each other’s closest relatives: congruent evidence from multiple proteins. Proceedings of the National Academy of Sciences USA. 1993;90(24):11558-11562. PubMed

[6] Steenkamp ET, Wright J, Baldauf SL. The protistan origins of animals and fungi. Molecular Biology and Evolution. 2006;23(1):93-106. PubMed

[7] Torruella G, Derelle R, Paps J, et al. Phylogenetic Relationships within the Opisthokonta Based on Phylogenomic Analyses of Conserved Single-Copy Protein Domains. Molecular Biology and Evolution. 2012;29(2):531-544. Oxford Academic

[8] Loron CC, François C, Rainbird RH, Turner EC, Borensztajn S, Javaux EJ. Early fungi from the Proterozoic era in Arctic Canada. Nature. 2019;570:232-235. Nature

[9] Craig DB. How many spores do mushrooms release? A quantitative review. Mycological Research. Spore count data compiled from Buller and subsequent work.

[10] Hibbett DS, Binder M, Bischoff JF, et al. A higher-level phylogenetic classification of the Fungi. Mycological Research. 2007;111(5):509-547. PubMed

[11] Tedersoo L, Sánchez-Ramírez S, Kõljalg U, et al. High-level classification of the Fungi and a tool for evolutionary ecological analyses. Fungal Diversity. 2018;90:135-159. Springer

[12] Scheele BC, Pasmans F, Skerratt LF, et al. Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity. Science. 2019;363(6434):1459-1463. Science

[13] Spribille T, Tuovinen V, Resl P, et al. Basidiomycete yeasts in the cortex of ascomycete macrolichens. Science. 2016;353(6298):488-492. PubMed

[14] Baldauf SL, Doolittle WF. Origin and evolution of the slime molds (Mycetozoa). Proceedings of the National Academy of Sciences USA. 1997;94(22):12007-12012. PubMed

[15] Hawksworth DL. The fungal dimension of biodiversity: magnitude, significance, and conservation. Mycological Research. 1991;95(6):641-655. The original 1.5 million species estimate.

[16] Wang B, Qiu YL. Phylogenetic distribution and evolution of mycorrhizas in land plants. Mycorrhiza. 2006;16(5):299-363. PubMed

Not medical advice. For informational purposes only. This post discusses organisms and biology; it does not make therapeutic claims.

• The Fungi Kingdom: How It Differs From Plants and Animals
• How Do Mushrooms Grow? From Spore to Fruiting Body Explained
• Lion’s Mane Mushroom Benefits: What Science Actually Says
• Mushroom Contamination: How to Identify, Prevent, and Deal With It
• Why I Became Obsessed With Fungi and Never Looked Back