Pileus 6-35 mm. hemispherical then conico-convex, expanding to plano-convex, finally applanate with undulating marginal zone, with margin slightly to distinctly involute when young, not hygrophanous, not translucently striate, dark blackish blue, bluish grey or violaceous blue, uniformly coloured, while expanding with age turning violaceous brown as the context becomes visible between the dark blue fibrils (K. & W. 15-21E-F5-2; Mu. 10 YR 5f2, 6ÀŒ2 + blue), entirely rugulose or tomentose when young, becoming squamulose or squarrulose with age, especially at centre; at margin’ usually glabrous to radially fibrillose, shiny, especially when dry. Lamellae, L = 20-40, I = (1-)3-7, moderately crowded, adnate or emarginate, rarely subdecurrent, arcuate, then segmentiform, rarely ventricose, sometimes transvenose, pale to fairly dark blue when young. especially near margin of pileus, then greyish pink with strongly contrasting blackish blue crenulate to denticulate edge. Stipe 20-50 × 1.5-4 mm. cylindrical or compressed with longitudinal groove. rarely with swollen base, concolorous with pileus when young, soon paler and more greenish-olivaceous or brown-grey covered with darker. bluish, adpressed flocculose fibrils. rarely glabrous, at apex white pruinose. white tomentose at base. Context concolorous with surface except for pallid inner part, brittle. Smell none or weakly to strongly aromatic like flowers (violets). Taste none or nasty-rancidulous.

Spores 9.0-11.5 × .5-8.0 µm, Q = 1.15-1.6, Q av. = 1.25-1.3, ellipsoid in outline with 5-7 angles in side-view. Basidia 24-53 × 8-15 µm, 4-spored, clampless. Lamella edge entirely sterile. Cheilocystidia 25-100 × 3.5-20 µm, cylindrical to clavate, very abundant, forming a thick sterile band along edge, always with blue intracellular pigment. Pileipellis a cutis to a trichoderm at margin, a trichoderm to a hymeniderm at centre, made up of cylindrical to clavate 8-35(-40) µm wide terminal cells. Pigment blue, intracellular in pileipellis and upper pilei trama. Brilliant granules rare to abundant in pileitrama. Clamp-connections absent.

Habitat & distr. – In groups in poorly manured, semi-natural grassland on moist to relatively dry, sandy, peaty or clayey, acid to basic soil. Fairly common. July-Nov.

Entoloma serrulatum is the most common species of ‘Leptonia’ in Europe. and occurs in many types of poorly manured grassland, natural grasslands, etc. from sea-level up into the subalpine zone. It occurs also in N. America, where it frequently grows in forests.

- https://www.mycobank.org/...