What You Should Know
Tricholoma sejunctum is a medium-sized mushroom with a greenish brownish yellow, slightly viscid cap adorned with abundant, well-defined, blackish fibrils that radiate from the dark center, and whitish to pale yellow gills and stipe. The odor is mild to farinaceous and the taste mild to unpleasant.
The species is classified as inedible by some field guides, though it does seem to have been traditionally consumed in much of the world without noted ill effects. More recently, in Europe, it has been identified as responsible for poisonings. However, it also shows promise as an anti-viral or anti-cancer mushroom.
Caps of Tricholoma sejunctum are rarely regular because usually these mushrooms occur in tightly packed clumps or tufts and the caps become distorted as they jostle for space.
First described from England during the reign of Queen Victoria, Tricholoma sejunctum is a hardwood-associated, yellow-green species of Tricholoma that features a moderate covering of slightly darker, radiating, appressed fibrils, along with white gills. Its odor is strongly "farinaceous" (mealy, or cucumber-y) and, under the microscope, it lacks clamp connections.
Other names: Deceiving Knight, Braungelber Ritterling (German), Streephoedridderzwam (Dutch).
Tricholoma sejunctum Mushroom Identification
Mycorrhizal with oaks and other hardwoods in temperate zones; growing scattered or gregariously; North American distribution uncertain; late summer and fall.
4–9 cm; convex with a central bump, becoming broadly convex, broadly bell-shaped, or nearly flat; sticky when fresh and young but soon dry; yellowish to olive-yellow, moderately covered with grayish to olive, radiating, appressed fibers (especially over the center); the margin often brighter yellow and somewhat inrolled when young.
Attached to the stem by a notch; close; short-gills frequent; white, sometimes developing yellow stains toward the cap margin.
3–10 cm long; 1–1.5 cm thick; equal; bald; dry; whitish, sometimes with yellow tinges or yellowish overall; basal mycelium white.
White; not changing when sliced; thick.
KOH on cap surface negative.
Spores 5–8 x 3.5–5.5 µm; ellipsoid, with a small apiculus; smooth; hyaline in KOH; inamyloid. Lamellar trama parallel. Cheilocystidia sometimes present; 15–40 x 5–15 µm; clavate, sublageniform, cylindric, or somewhat irregular; thin-walled; smooth; hyaline in KOH. Pleurocystidia not found. Pileipellis an ixocutis; elements 2.5–8 µm wide, brownish walled, smooth or a little encrusted, hyaline in KOH. Clamp connections not found.
Tricholoma sejunctum Look-Alikes
Has a yellow cap with a brown-olive central area, and yellow gills even when young.
Has a darker hat.
Grows in coniferous forest.
Distinguished by it's volva, stem ring, and free gills.
Tricholoma sejunctum Taxonomy and Etymology
The basionym of this species dates from 1799, when British mycologist James Sowerby (1757 - 1822) described this species and gave it the binomial name Agaricus sejunctus. It was the famous French mycologist Lucien Quélet who, in 1872, transferred this species to the genus Tricholoma, whereupon its scientific name became Tricholoma sejunctum.
Synonyms of Tricholoma sejunctum include Agaricus sejunctus Sowerby, Gyrophila sejuncta (Sowerby) Quél., and Melanoleuca sejuncta (Sowerby) Murrill.
Tricholoma was established as a genus by the great Swedish mycologist Elias Magnus Fries. The generic name comes from Greek words meaning 'hairy fringe', and it must be one of the least appropriate mycological genus names because very few species within this genus have hairy or even shaggily scaly cap margins that would justify the descriptive term.
The specific epithet sejunctum comes from Latin and means 'having separated'; it refers to the almost complete (deeply notched) separation of the gills from the stem.
Photo 1 - Author: Archenzo (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 2 - Author: Jerzy Opioła (Creative Commons Attribution-Share Alike 4.0 International)
Photo 3 - Author: Geoff Balme (geoff balme) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 4 - Author: Gerhard Koller (Creative Commons Attribution-Share Alike 4.0 International)
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