Psilocybe semilanceata, commonly known as the liberty cap, is a species of fungus which produces psilocybin, psilocin and baeocystin. It is one of the most widely distributed psilocybin mushrooms in nature. The mushrooms have a distinctive conical to bell-shaped cap, up to in diameter, with a small nipple-like protrusion on the top. They are yellow to brown, covered with radial grooves when moist, and fade to a lighter color as they mature. Their stipes tend to be slender and long, and the same color or slightly lighter than the cap. The gill attachment to the stipe is adnexed (narrowly attached), and they are initially cream-colored before tinting purple to black as the spores mature. The spores are dark purplish-brown en masse, ellipsoid in shape, and measure 10.5–15 by 6.5–8.5 μm.
The mushroom grows in grassland habitats, especially wetter areas. Unlike P. cubensis, the fungus does not grow directly on dung; rather, it is a saprobic species that feeds off decaying grass roots. It is widely distributed in the temperate areas of the Northern Hemisphere, particularly in Europe, and has been reported occasionally in temperate areas of the Southern Hemisphere as well. The earliest reliable history of P. semilanceata intoxication dates back to 1799 in London, and in the 1960s the mushroom was the first European species confirmed to contain psilocybin. The possession or sale of psilocybin mushrooms is illegal in many countries.
Taxonomy
The species was first described by Elias Magnus Fries as Agaricus semilanceatus in his 1838 work Epicrisis Systematis Mycologici. Paul Kummer transferred it to Psilocybe in 1871 when he raised many of Fries's sub-groupings of Agaricus to the level of genus. Panaeolus semilanceatus, named by Jakob Emanuel Lange in both 1936 and 1939 publications, is a synonym. According to the taxonomical database MycoBank, several taxa once considered varieties of P. semilanceata to be synonymous with the species now known as Psilocybe strictipes: the caerulescens variety described by Pier Andrea Saccardo in 1887 (originally named Agaricus semilanceatus var. coerulescens by Mordecai Cubitt Cooke in 1881), the microspora variety described by Rolf Singer in 1969, and the obtusata variety described by Marcel Bon in 1985.
Several molecular studies published in the 2000s demonstrated that Psilocybe, as it was defined then, was polyphyletic. The studies supported the idea of dividing the genus into two clades, one consisting of the bluing, hallucinogenic species in the family Hymenogastraceae, and the other the non-bluing, non-hallucinogenic species in the family Strophariaceae. However, the generally accepted lectotype (a specimen later selected when the original author of a taxon name did not designate a type) of the genus as a whole was Psilocybe montana, which is a non-bluing, non-hallucinogenic species. If the non-bluing, non-hallucinogenic species in the study were to be segregated, it would have left the hallucinogenic clade without a valid name. To resolve this dilemma, several mycologists proposed in a 2005 publication to conserve the name Psilocybe, with P. semilanceata as the type. As they explained, conserving the name Psilocybe in this way would prevent nomenclatural changes to a well-known group of fungi, many species of which are "linked to archaeology, anthropology, religion, alternate life styles, forensic science, law enforcement, laws and regulation". Further, the name P. semilanceata had historically been accepted as the lectotype by many authors in the period 1938–68. The proposal to conserve the name Psilocybe, with P. semilanceata as the type was accepted unanimously by the Nomenclature Committee for Fungi in 2009.
The mushroom takes its common name from the Phrygian cap, also known as the "liberty cap", which it resembles; P. semilanceata shares its common name with P. pelliculosa, a species from which it is more or less indistinguishable in appearance. The Latin word for Phrygian cap is pileus, nowadays the technical name for what is commonly known as the "cap" of a fungal fruit body. In the 18th century, Phrygian caps were placed on Liberty poles, which resemble the stipe of the mushroom. The generic name is derived from Ancient Greek psilos (ψιλός) 'smooth, bare' and Byzantine Greek kubê (κύβη) 'head'. The specific epithet comes from Latin semi 'half, somewhat' and lanceata, from lanceolatus 'spear-shaped'.
Description
The cap of P. semilanceata is in diameter and tall. It varies in shape from sharply conical to bell-shaped, often with a prominent papilla (a nipple-shaped structure), and does not change shape considerably as it ages. The cap margin is initially rolled inward but unrolls to become straight or even curled upwards in maturity. The cap is hygrophanous, meaning it assumes different colors depending on its state of hydration. When it is moist, the cap is ochraceous to pale brown to dark chestnut brown, but darker in the center, often with a greenish-blue tinge. When moist, radial grooves (striations) can be seen on the cap that correspond to the positions of the gills underneath. When the cap is dry, it becomes much paler, a light yellow-brown color. Moist mushrooms have sticky surfaces that result from a thin gelatinous film called a pellicle. This film becomes apparent if a piece of the cap is broken by bending it back and peeling away the piece. When the cap dries from exposure to the sun, the film turns whitish and is no longer peelable.
On the underside of the mushroom's cap, there are between 15 and 27 individual narrow gills that are moderately crowded together, and they have a narrowly adnexed to almost free attachment to the stipe. Their color is initially pale brown, but becomes dark gray to purple-brown with a lighter edge as the spores mature. The slender yellowish-brown stipe is long by thick, and usually slightly thicker towards the base. The mushroom has a thin cobweb-like partial veil that does not last long before disappearing; sometimes, the partial veil leaves an annular zone on the stipe that may be darkened by spores. The flesh is thin and membrane-like, and roughly the same color as the surface tissue. It has a farinaceous (similar to freshly ground flour) odor and taste. All parts of the mushroom will stain a bluish color if handled or bruised, and it may naturally turn blue with age.
Microscopic characteristics In deposit, the spores are a deep reddish purple-brown color. The use of an optical microscope can reveal further details: the spores are oblong when seen in side view, and oblong to oval in frontal view, with dimensions of 10.5–15 by 6.5–8.5 μm. The basidia (spore bearing cells of the hymenium), are 20–31 by 5–9 μm, four-spored, and have clamps at their bases; there are no basidia found on the sterile gill edge. The cheilocystidia (cystidia on the gill edge) measure 15–30 by 4–7 μm, and are flask-shaped with long thin necks that are 1–3.5 μm wide. P. semilanceata does not have pleurocystidia (cystidia on the gill face). The cap cuticle is up to 90 μm thick, and is made of a tissue layer called an ixocutis—a gelatinized layer of hyphae lying parallel to the cap surface. The hyphae comprising the ixocutis are cylindrical, hyaline, and 1–3.5 μm wide. Immediately under the cap cuticle is the subpellis, made of hyphae that are 4–12 μm wide with yellowish-brown encrusted walls. There are clamp connections present in the hyphae of all tissues.
Other forms The anamorphic form of P. semilanceata is an asexual stage in the fungus's life cycle involved in the development of mitotic diaspores (conidia). In culture, grown in a petri dish, the fungus forms a white to pale orange cottony or felt-like mat of mycelia. The conidia formed are straight to curved, measuring 2.0–8.0 by 1.1–2.0 μm, and may contain one to several small intracellular droplets. Although little is known of the anamorphic stage of P. semilanceata beyond the confines of laboratory culture, in general, the morphology of the asexual structures may be used as classical characters in phylogenetic analyses to help understand the evolutionary relationships between related groups of fungi.
Scottish mycologist Roy Watling described sequestrate (truffle-like) or secotioid versions of P. semilanceata he found growing in association with regular fruit bodies. These versions had elongated caps, long and wide at the base, with the inward curved margins closely hugging the stipe from the development of membranous flanges. Their gills were narrow, closely crowded together, and anastomosed (fused together in a vein-like network). The color of the gills was sepia with a brownish vinaceous (red wine-colored) cast, and a white margin. The stipes of the fruit bodies were long by thick, with about of stipe length covered by the extended cap. The thick-walled ellipsoid spores were 12.5–13.5 by 6.5–7 μm. Despite the significant differences in morphology, molecular analysis showed the secotioid version to be the same species as the typical morphotype.
Similar species
There are several other Psilocybe species that may be confused with P. semilanceata due to similarities in physical appearance. P. strictipes is a slender grassland species that is differentiated macroscopically from P. semilanceata by the lack of a prominent papilla. P. mexicana, commonly known as the "Mexican liberty cap", is also similar in appearance, but is found in manure-rich soil in subtropical grasslands in Mexico. It has somewhat smaller spores than P. semilanceata, typically 8–9.9 by 5.5–7.7 μm. Another lookalike species is P. samuiensis, found in Thailand, where it grows in well-manured clay-like soils or among paddy fields. This mushroom can be distinguished from P. semilanceata by its smaller cap, up to in diameter, and its rhomboid-shaped spores. P. pelliculosa is physically similar to such a degree that it may be indistinguishable in the field. It differs from P. semilanceata by virtue of its smaller spores, measuring 9–13 by 5–7 μm.
P. semilanceata has also been confused with the toxic muscarine-containing species Inocybe geophylla,Bresinsky and Besl (1989), pp. 115–16. a whitish mushroom with a silky cap, yellowish-brown to pale grayish gills, and a dull yellowish-brown spore print.
Ecology and habitat
Psilocybe semilanceata fruits solitarily or in groups on rich and acidic soil, typically in grasslands, such as meadows, pastures, or lawns. It is often found in pastures that have been fertilized with sheep or cow dung, although it does not typically grow directly on the dung.
P. semilanceata, like all others species of the genus Psilocybe, is a saprobic fungus, meaning it obtains nutrients by breaking down organic matter. The mushroom is also associated with sedges in moist areas of fields, and it is thought to live on the decaying root remains. At least one study has demonstrated an association of P. semilanceata with the roots of the grasses Agrosiis tenuis, Poa annua, and the dicot Lolium perenne.
Like some other grassland psilocybin mushroom species such as P. mexicana, P. tampanensis and Conocybe cyanopus, P. semilanceata may form sclerotia, a dormant form of the fungus, which affords it some protection from wildfires and other natural disasters.