Hebeloma helvolescens - A non-current Hebeloma species

According to our data Hebeloma helvolescens is not the name of a current valid species of Hebeloma. Our database has records for the following similar names

Full name: Hebeloma helvolescens S. Imai (1938)
Published: Journal of the Faculty of Agriculture, Hokkaido Imperila University 43 (2): 229 (1938)
Taxonomic status: This is a Homophron.
Notes: Current name: Homophron helvolescens (S. Imai) Beker & U. Eberh. Mycol Prog. 21: 467 (2022)

Types: JAPAN: Hokkaido, Sapporo Botanic Garden, Ishikari, Sapporo (approx. 43.0639°N, 141.3426°E, alt. approx. 30 m a.s.l.) on soil in woodland clearing, 4 Jul. 1932, S. Imai (Holotype. herbarium acc. no. SAPA10000035 (No. 312), HJB1000374).

Original diagnosis: Caespitosum. Pileo 4-8 cm. Iato, conico-convexo, dein umbonato, glabro, non viscido, cinnamomeo, margine pallidiore; carne roseola, odore subfarinaeeo, sapore aeri; lamellis emarginatis vel adnexis, eonfertis, primo "vinaeeous-buff", dein fulvis; stipite 5-8 em. longo, 8-16 mm. erasso, aequali vel attenuato, albo, obsolete fibrilloso, apiee furfuraeeo, eavo; sporis in eumulo fulvo-ferrugineis, ellipsoideis, laevibus, 8-10 X 4-5 µ; eystidiis laneeolatis vel subcylindrico-clavatis, saepe cristallatis, subhyalinis, 50-72.5 x 10-14 µ.

English translation: Caespitose. Pileus 4-8 cm broad, conical to convex, then umbonate, glabrous, non-viscid, cinnamon, paler on the margin; context pale flesh-coloured, smell almost mealy, taste acrid; lamellae emarginate or adnexed, crowded, at first "vinaceous-buff“, then fulvous; stipe 5-8 cm long, 8-16 mm thick, equal or attenuate, white, indistinctly fibrillose, scurfy at the apex, fistulose; spores fulvous-rusty in mass, ellipsoid, smooth, 8-10 x 4-5 μ; cystidia lanceolate or subcylindrical-clavate, often bearing crystals, subhyaline, 50-72.5 x 10-14 μ.

Commentary: Our examination of the type material is in good agreement with the description given by Imai (1938). Imai also mentions the caespitose habit of this species, and the presence of crystals on the cystidia. Morphologically, it appears to be closely related or even conspecific with Ho. spadiceum. Spore size of Ho. spadiceum is, according to Vašutová (2008), 8–9.5 × 4–5 μm, average 8.7 × 4.7 μm, Q 1.6–2.2 (−2.3) and according to Enderle (1989) who later collected the specimen that was selected as epitype by Örstadius (2001) (8.0)9–10.2(11) × 4.2–5.2(5.6) μm. Both authors stress the light spore colour of the species, under the microscope in water and in the spore deposit, according to Vašutová (2008) brick-beige (S40Y60M5, Küppers 1999). Vašutová (2008) suspected that Smith (1972) concept of Psathyrella spadicea might not coincide with what is called Ho. spadiceum in Europe, citing a difference in spore deposit colour as indication. Imai (1938) described the spores of Ho. helvolescens as cinnamon; S40Y60M5 (Küppers 1999) is lighter and more greenish than cinnamon; under the microscope the spores of Ho. helvolescens appear distinctly colored. The ITS of the eptitype of Ho. spadiceum is sequenced, as is the holotype of Ho. helvolescens and both are included in the “Homophron spacideum s.l.” clade of Fig. 3. This clade includes a number of supported (and unsupported) subclades that appear to have restricted geographical distributions. However, the sequence variation underlying these clades is so small (see scale in Fig. 3) and the data is only from a single locus that we hesitate to recognize them as hypotheses of distinct species. Vašutová et al. (2008) stressed that ITS is not sufficient for delimiting species in the Psathyrellaceae. Thus, it is not clear whether Ho. helvolescens is indeed a later synonym of Ho. spadiceum. Japanese name: Ko-wakafusa-take (Imai 1938).