Psilocybe

Key takeaways

Psilocybe belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Psilocybe to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Psilocybe from memory before moving on to harder problems.

Reference excerpt

Psilocybe ( SY-loh-SY-bee) is a genus of gilled mushrooms, growing worldwide, in the family Hymenogastraceae. Many species contain the psychedelic prodrug psilocybin.

Taxonomy

Taxonomic history

A 2002 study of the molecular phylogeny of the agarics indicated the genus Psilocybe as then defined was polyphyletic, falling into two distinct clades that are not directly related to each other. The blue-staining hallucinogenic species constituted one clade and the non-bluing species the other. The previous type species of the genus, Psilocybe montana (now Deconica montana), was in the non-bluing clade, but in 2010, the type species was changed to P. semilanceata, a member of the bluing clade. A 2006 molecular phylogenetic study of the Agaricales by Matheny and colleagues, further demonstrated the separation of the bluing and non-bluing clades of Psilocybe in a larger, strongly supported phylogenetic tree of the Agaricales. Psilocybe had been placed taxonomically in the agaric family Strophariaceae based upon its spore and pileipellis morphology. The phylogenetic study by Matheny et al., placed the non-bluing Psilocybe and its close relatives in a basal position within the Strophariaceae, a sister taxon to a clade containing the other genera within that family. The bluing Psilocybe, however, form a clade that is sister to Galerina in the newly revised family, Hymenogastraceae which used to be restricted to secotioid, false-truffles. The phylogenetic study by Moncalvo, et al. confirmed that the agaric genus Melanotus is simply a subgroup of the non-bluing Psilocybe, all of which are placed in Deconica, and also pointed to a close relationship between the latter genus and the genera Kuehneromyces and Phaeogalera.

Modern classification In 2007, a paper by Redhead et al. proposed conserving the genus Psilocybe with Psilocybe semilanceata as its type species. The suggestion was accepted by unanimous vote of the Nomenclature Committee for Fungi of the International Botanical Congress in 2010, meaning that P. semilanceata (a member of the bluing clade) now serves as the type species of the genus. Since P. semilanceata is now the type species of the genus, the bluing hallucinogenic clade remained in the genus Psilocybe (Hymenogastraceae) while the non-bluing clade were transferred to the genus Deconica (Strophariaceae). However, it has been demonstrated that P. fuscofulva, a species which used to be known as P. atrobrunnea, belongs to the genus Psilocybe s.s., but does not contain psychotropic compounds. Negative results have also been published for P. fimetaria.

Etymology The genus name Psilocybe is a compound of the Greek elements ψιλός (psilós) 'bare' / 'naked' / 'bald' and κύβη (kúbe) 'head' / 'swelling', giving the meaning "bare-headed" (i.e. bald) referring to the mushroom's detachable pellicle (loose skin over the cap), which can resemble a bald pate.

Description

Psilocybe fruit bodies are generally small, undistinguished mushrooms with a typical "little brown mushroom" morphology. Macroscopically, they are characterized by their small to occasionally medium size, brown to yellow-brown coloration, with a hygrophanous cap, and a spore print-color that ranges from lilac-brown to dark purple-brown (though rusty-brown colored varieties are known in at least one species). Hallucinogenic species typically have a blue-staining reaction when the fruit body is bruised. Microscopically, they are characterized by pileipellis with hyphae that run parallel to the pileus surface, forming a cutis, by their lack of chrysocystidia, and by spores which are smooth, ellipsoid to rhomboid to subhexagonal in shape, with a distinct apical germ pore. Ecologically, all species of Psilocybe are saprotrophs, growing on various kinds of decaying organic matter.

Distribution and habitat

Geographically, species in this genus are found throughout the world in most biomes. The greatest species diversity seems to be in the neotropics, from Mesoamerica through Brazil and Chile. Psilocybe are found in a variety of habitats and substrates. Many of the species found in temperate regions, such as Psilocybe cyanescens, seem to have an affinity for landscaped areas mulched with woodchips and are actually rather rare in natural settings removed from human habitation. Contrary to popular belief, only a minority of Psilocybe species, such as P. cubensis and P. subcubensis, grow directly on feces. Many other species are found in habitats such as mossy, grassy, or forest humus soils. Psilocybe arose about 65 million years ago. In 2023, two new Psilocybe species (Hymenogastraceae), P. ingeli and P. maluti, were described from southern Africa.

Psychoactivity

Biochemistry and pharmacology

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Illustrations

Worked examples

Example 1 — a first encounter with Psilocybe

Start with the simplest possible case. Write down what Psilocybe claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Psilocybe before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Psilocybe ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Psilocybe

In research: Psilocybe appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Psilocybe in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Psilocybe is common in secondary-school and first-year university syllabi. It links to neighbouring topics Agaricales genera, Entheogens, Psilocybe, so understanding it makes those chapters shorter.
In everyday life: Look for Psilocybe outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Psilocybe in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Psilocybe means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Psilocybe out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Psilocybe in simple terms?

Psilocybe ( SY-loh-SY-bee) is a genus of gilled mushrooms, growing worldwide, in the family Hymenogastraceae. Many species contain the psychedelic prodrug psilocybin.

Why does Psilocybe matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Psilocybe?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Psilocybe.