Full name: Hebeloma flexuosipes Peck (1911)
Published: Bull. N. Y. St. Mus. 150: 55 (1911)
Taxonomic status: This is a Agrocybe.
Notes: Current name is: Agrocybe flexuosipes (Peck) Beker & U. Eberh., Mycologia 114: 378 (2022).

Types: UNITED STATES: Pennsylvania: Allegheny County, Pittsburgh, Schenley Park (approx. 40.43°N, 79.99°W, alt. approx. 250 m a.s.l.) on soil, Jul. 1909, D.R. Sumstine, det: C.H. Peck (Holotype. herbarium acc. no. NYS-F-001221, HJB1000085; Isotype. herbarium acc. no. WTU-F-039659, HJB1000358).

Original diagnosis: Pileus tenuis, convexus, glaber, viscidulus, luteolus vel argillaceo-brunneus, carne alba; lamellae confertae, adnatae, brunneo-ferrugineae; stipes fibrosus aequalis vel leviter basi incrassatus, flexuosus, solidus farctusve, ad apicem pruinoso-pubescens et minute glandulosus, pallidus vel pileo in colore similis, velo nullo, mycelio fibrilloso, abundante, candido; sporae subellipsoideae, brunneo-ferruginosae, 12-16 X 7-9 μ.

English translation: Pileus thin, smooth, slightly viscid, yellowish or argillaceous-brown, with white context; lamellae crowded, adnate, brownish-rusty; stipe fibrous equal or slightly enlarged at base, flexuous, solid or stuffed, pruinose-downy and finely glandular at the apex, pale or same colour as pileus, veil none, mycelium fibrillose, abundant, pure white; spores subellipsoid, brownish-rusty, 12-16 x 7-9 μ

Commentary: This is an Agrocybe. The spores are elliptical with a germ pore, with indistinct ornamentation, perispore not loosening and strongly dextrinoid, on average 12.1 × 7.7 μm; the cheilocystidia are ventricose. The assignment to Agrocybe is supported by phylogenetic analysis of ITS data. Thus, the taxon is recombined. The ITS of A. flexuosipes is very similar to sequences from material identified as A. putaminum (described from France, Maire 1913) and A. smithii (described from Massachusetts, Watling and Bigelow 1983). The two species are very similar; the most important difference is the presence of pileocystidia in A. putaminum and their absence in A. smithii (Vellinga 2008; Halama 2016). Pileocystidia were not observed in the type material of A. flexuosipes. If regarded as conspecific, A. flexuosipes would have nomenclatural priority over both A. putaminum and A. smithii, however, basidiome samples from the type localities have not been sequenced.