Occurs in seminatural grasslands, inner dune areas and other open areas. Autumn. Distribution not fully understood but apparently widespread.
Pileus 25-50 mm wide, conical to flat, hygrophanous, sulphur yellow at centre, ± reddish grey towards margin. Lamellae adnate to subdecurrent, greyish rose. Stipe 65-80 mm long, cylindrical, reddish grey. Spores (according to the protologue) 5.6-7.3 x 2.8-3.8 μm, Q 1.7-2.4, Qav = 1.95, ovoid, amyloid.
I have studied one Danish collection (C no 46691):
Basidia 22-25 x 6-7
μm, slender-clavate, 4-spored, with sterigmata up to 5 μm long. Spores (n=20) 6.5-8 x 3.2-4 μm, Q 1.8-2.2, Qav = 1.97, pip-shaped, amyloid. Cheilocystidia 22-81 x 10-22 μm, forming a sterile band, fusiform, clavate or utriform, apically broadly rounded to somewhat attenuated, rarely with one or two cylindrical excrescences. Pleurocystidia similar. Lamellar trama dextrinoid. Hyphae of the pileipellis 2-6.5 μm wide, smooth, rarely with a short cylindrical excrescence. Hyphae of the cortical layer of the stipe 1.8-4 μm wide, smooth; caulocystidia 18-100 x 9-10 μm, fusiform or clavate, smooth. Clamp connections present in all tissues.
This taxon has been well known as a rather recognizable variety or form of M. pura. Harder et al. (2013) raised it to species level, based on molecular phylogenetic analyses. It is characterized by a yellow cap and slightly smaller spores than in M. pura. Besides, it is a grassland specialist, in contrast to the other species of the section, which all typically inhabit forest litter.
Microphotos of cheilocystidia
Microphotos of pileipellis