bell-shaped mottlegill

Panaeolus papilionaceus var. papilionaceus, also known as Agaricus calosus, Panaeolus papilionaceus, Panaeolus campanulatus, Panaeolus retirugis, and Panaeolus sphinctrinus, and commonly known as Petticoat mottlegill, is a common and widely distributed little brown mushroom that feeds on dung.

This mushroom is the type species for the genus Panaeolus.

Psilocybin mushrooms, also known as psychedelic mushrooms, are fungi that contain psychoactive indole alkaloids. Multiple colloquial terms are used for psilocybin mushrooms, the most common being shrooms and magic mushrooms. Biological genera containing psilocybin mushrooms include Agrocybe, Conocybe, Copelandia, Galerina, Gerronema, Gymnopilus, Hypholoma, Inocybe, Mycena, Pluteus, and Psilocybe. About 180 species are found in the genus Psilocybe. Psilocybe cubensis is the most popular common psilocybin mushroom and is believed to be where the slang name shrooms originated.^{[citation needed]}

Psilocybin mushrooms have likely been used since prehistoric times and may have been depicted in rock art. Many cultures have used these mushrooms in religious rites. In modern Western society, they are used recreationally for their psychedelic effects. Recent studies done at Imperial College London and Johns Hopkins School of Medicine conclude, when used properly, psilocybin acts as an antidepressant as suggested by fMRI brain scans.

Psilocin (also known as 4-HO-DMT, psilocine, psilocyn, or psilotsin), is a substituted tryptamine alkaloid and a serotonergic psychedelic drug. It is present in most psychedelic mushrooms together with its phosphorylated counterpart psilocybin. Psilocin is a Schedule I drug under the Convention on Psychotropic Substances. The mind-altering effects of psilocin are highly variable and subjective and resemble those of LSD and mescaline.

Psilocybin (/ˌsɪləˈsaɪbɪn/ SIL-ə-SY-bin) is a naturally occurring psychedelic compound produced by more than 200 species of mushrooms, collectively known as psilocybin mushrooms. The most potent are members of the genus Psilocybe, such as P. azurescens, P. semilanceata, and P. cyanescens, but psilocybin has also been isolated from about a dozen other genera. As a prodrug, psilocybin is quickly converted by the body to psilocin, which has mind-altering effects similar to those of LSD and mescaline. The effects generally include euphoria, visual and mental hallucinations, changes in perception, a distorted sense of time, and spiritual experiences, and can include possible adverse reactions such as nausea and panic attacks.

Psilocybe is a genus of small mushrooms growing worldwide. This genus is best known for its species with psychedelic properties, widely known as "magic mushrooms". Psilocin and psilocybin are the psychedelic compounds responsible for the psychoactive effects of many species in the genus.

A psychoactive drug, psychopharmaceutical, or psychotropic is a chemical substance that crosses the blood–brain barrier and acts primarily upon the central nervous system where it affects brain function, resulting in alterations in perception, mood, consciousness, cognition, and behavior. These substances may be used recreationally, to purposefully alter one's consciousness, or as entheogens, for ritual, spiritual, and/or shamanic purposes, as a tool for studying or augmenting the mind. Many psychoactive drugs have therapeutic utility, e.g., as anesthetics, analgesics, or for the treatment of psychiatric disorders.

Psychoactive substances often bring about subjective changes in consciousness and mood that the user may find pleasant (e.g. euphoria) or advantageous (e.g. increased alertness) and are thus reinforcing. Thus, many psychoactive substances are abused, that is, used excessively, despite health risks or negative consequences. With sustained use of some substances, psychological and physical dependence ("addiction") may develop, making the cycle of abuse even more difficult to interrupt. Drug rehabilitation aims to break this cycle of dependency, through a combination of psychotherapy, support groups, maintenance and even other psychoactive substances. However, the reverse is also true in some cases, that certain experiences on drugs may be so unfriendly and uncomforting that the user may never want to try the substance again. This is especially true of the deliriants (e.g. Jimson weed) and powerful dissociatives (e.g. Salvia divinorum). Most purely psychedelic drugs are considered to be non-addictive (e.g. LSD, psilocybin, mescaline). "Psychedelic amphetamines" or empathogen-entactogens (such as MDA and MDMA) may produce an additional stimulant and/or euphoriant effect, and thus have an addiction potential.