Inocybe praetervisa

Inocybe praetervisa is a small, yellow and brown mushroom in the family Inocybaceae, distinguished from other members of the genus by its unusual spores and bulb. The unusual spores led to the species being named the type species of the now-abandoned genus "Astrosporina"; recent studies have shown that such a genus could not exist, as the species with the defining traits do not form a monophyletic group. However, it is a part of several clades within the genus "Inocybe". "I. praetervisa" grows on the ground in woodland, favouring beech trees, and is found in Europe, North America and Asia. It is inedible and probably poisonous due to the presence of muscarine. The ingestion of muscarine can lead to SLUDGE syndrome, and could potentially lead to death due to respiratory failure.
Taxonomy and naming.
"Inocybe praetervisa" was first described by Lucien Quélet in the first volume of Giacomo Bresadola's 1883 publication "Fungi tridentini". The species was moved to the genus "Astrosporina" by Joseph Schröter in 1889, but this was rejected, and the name "Astrosporina praetervisa" is now considered an obligate synonym. "Astrosporina praetervisa" was the type species of the no longer recognised genus. The specific epithet "praetervisa" comes from the Latin word meaning "overlooked".
Within the genus "Inocybe", "I. praetervisa" has been placed in the subgenus "Inocybe". Mycologist Rolf Singer places the species in the section "Marginatae"; mycologist Thom Kuyper considers "Marginatae" a supersection, and includes "I. praetervisa" along with "I. abietis", "I. calospora" and "I. godeyi". Phylogenetics has shown that, in addition to the large clade of subgenus "Inocybe", "I. praetervisa" forms a clade with "I. calospora", "I. lanuginosa" and "I. leptophylla". The species are similar in that all four have basidiospores with small nodules; it was this feature that defined the genus "Astrosporina", with then "A. praetervisa" as its type species. However, when phylogenetic analysis later concluded that nodulose-spored "Inocybe" species do not form a monophyletic group, the name "Astrosporina" was deemed inappropriate at a generic level. But it may be considered useful at a lower level to refer to the clade of the four "Inocybe" species. Of those four, "I. praetervisa" is most closely related to "I. calospora", with which it forms a smaller and closer clade. A different study also found the close relationship between "I. praetervisa" and "I. calospora"; it also named "I. teraturgus" as a part of the clade containing "I. praetervisa", "I. calospora", "I. lanuginosa" and "I. leptophylla".
Description.
"Inocybe praetervisa" has a bell-shaped (later expanding) cap of in diameter, which is a yellowish-brown colour. It is fibrous, and splits from the margin (which curves inwards) to the centre. The stem is from in height, and from thick. It is white, maturing to a pale straw-yellow, and the whole stem is farinaceous, meaning it is covered in particles resembling meal. The stem has a distinct bulb at the base, which is moderately marginate, and lacks a ring. The flesh is white, and discolours to yellowish in the stem. The gills are initially whitish, but later become a clay-brown with toothed, white edges. They are adnexed, meaning they connect to the stem by only part of their depth, and are crowded closely together.
Microscopic features.
"Inocybe praetervisa" leaves a clay-brown spore print, while the spores themselves are rectangular with a large number of "distinct, angular knobs". In size, the spores measure between in length by between in width. "Inocybe praetervisa" has both pleuro- and cheilocystidia which are relatively spindle-shaped with apical encrustation. The cystidia have hyaline or pale yellow walls.
Similar species.
The species can be differentiated from the similar "I. cookei" by its "irregular, lumpy spores". It is also similar to "I. rimosa", but differs in the presence of a bulb. Another species that can be differentiated by the lack of a bulb is "I. numerosigibba".
Habitat and distribution.
"Inocybe praetervisa" is an ectomycorrhizal species, and is found on the ground in mixed, deciduous or even coniferous woodland. It typically favours beech. Mushrooms grow solitarily or in "trooping groups" in late summer and throughout autumn, though it is not commonly encountered species. It is found in Europe, Asia and North America.
Edibility and toxicity.
The species has a mild, indistinct taste, and a faint smell of flour. Mycologist Roger Phillips describes its edibility as "suspect", recommending that it be avoided, and notes that it is possible that the species is poisonous; most species of "Inocybe" have been shown to contain poisonous chemicals. Mycologist Ian Robert Hall lists the mushroom as containing the poisonous compound muscarine. Consumption of muscarine could lead to a number of physiological effects, including: excess salivation, lacrimation, uncontrollable urination and defecation, gastrointestinal problems and emesis (vomiting); this array of symptoms is also known by the acronym SLUDGE. Other potential effects include a drop in blood pressure, sweating and death due to respiratory failure.