Hebeloma radicosum: The Ultimate Mushroom Guide
About The Hebeloma radicosum Mushroom
Hebeloma radicosum, known for its long ‘root’ and membranous ring, has regularly been recorded in Japan and been the subject of many studies revolving around ectomycorrhizal fungi exposed to high levels of nitrogen compounds and tripartite associations between fungi, host trees, and mammals, including moles, wood mice, and shrews.
This mushroom is poisonous and can cause gastrointestinal distress in those who consume it.
Fruit bodies of the Hebeloma radicosum can be identified by the tapering root-like stipe base, as well as the almond-like odor. Found in Japan, Europe, and North America, it is an ammonia fungus, and fruits on mole, mouse, or shrew middens.
Other names: Rooting Poison Pie.
Hebeloma radicosum Identification
The fruit bodies have caps 5–10 cm (2.0–3.9 in) in diameter that is initially convex before flattening out in age. The surface of fresh caps is sticky; the color, which ranges from yellowish tan to golden brown to ochre, or pale cinnamon, is lighter towards the margin. The margins of young caps are curled inward, and often have adherent hanging remnants of the partial veil.
The gills are notched to nearly free from attachment to the stipe, and have scalloped or fringed edges, especially in maturity. Initially white, the gills change from ochre to reddish-brown as the spores mature.
The stipe measures 7.5–18 cm (3.0–7.1 in) long by 1.3–2.5 cm (0.5–1.0 in) thick and is usually swollen in the middle and tapered on each end. The stipe base is covered with pale brownish fibers and cottony scales over a cream ground color. The stipe is solid (i.e., not hollow) and firm, with a ring on the upper portion.
The flesh has a mild taste and an odor of almonds or marzipan. Several aromatic compounds are responsible for the mushroom's odor, including benzaldehyde, 2-phenylethanal, 2-phenylethanol, phenylacetic acid, N-formylaniline, and 1-octen-3-ol.
Hebeloma radicosum produces a rusty brown to cinnamon-brown spore print. Spores are almond-shaped, covered in small warts, and measure 8–10 by 5–6 μm. The basidia (spore-bearing cells) are four-spored.
The Japanese species Hebeloma radicosoides resembles H. radicosum in appearance and habitat, but can be distinguished by its yellower cap and lack of odor. Additionally, H. radicosoides fruits after experimental application of urea to soil, while H. radicosum does not. Another lookalike, Hypholoma radicosum, has a rooting stipe, but it is more slender and smells strongly of the compound iodoform.
Hebeloma radicosum Taxonomy
The species was first described scientifically by Jean Baptiste François Pierre Bulliard in 1784 as Agaricus radicosus. Adalbert Ricken transferred it to Hebeloma in 1915. Historical synonyms have resulted from the transfer of the fungus to the genera Pholiota by Paul Kummer in 1871, Dryophila by Lucien Quélet in 1886, Myxocybe by Victor Fayod in 1889, and Roumeguerites by Marcel Locquin in 1979.
The molecular analysis places the species in a basal position of the Myxocybe clade. This grouping of phylogenetically related species contains members that form a pseudorrhiza, such as H. danicum, H. senescens, H. calyptrosporum, H. birrus, H. pumilium, and H. cylindrosporum.
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