A small waxcap resembling Hygrocybe coccinea with a readily discolouring, orange-red to red cap, and a less smooth and slippery cap surface, microscopically distinguishable from coccinea due to its very slightly smaller but often slightly constricted basidospores. Very poorly known, but found in unfertilised grasslands between September and November.
Several species concepts have been applied to the name marchii in Britain, and most of the many current British and Irish records are probably of Hygrocybe reidii or other similar taxa. The concepts used here are following Boertmann (1995) The genus Hygrocybe, edn. 1.
Pileus (cap) 3-20 mm, generally hemispherical ranging from broadly domed to flat, in old specimens sometimes with upturned margin, greasy to slippery, orange to orange-red, sometime scarlet, discolouring to orange or yellow, sometimes with short translucent stripes near the margin. Lamellae (gills) broadly adnate (fully attached) to short decurrent (extending down the stipe), often remarkably broad, yellowish white, yellow to pale orange with paler edge, +- wider in the middle or somewhat curved. Stipe (cap) 15-40 x 2-3.5 mm, cylindrical or tapering downwards, straight or somewhat variably curved, dry, smooth and matt or with a slightly, silky sheen, orange-yellow to orange with paler base. Smell and taste not distinctive. Basidiospores (6-)7.5-9(-10) x 4-5 µm, Q = 1.5-2.3, average 1.8-2.0, oblong, cylindrical, ellipsoid, a minor part (max. 50 %) constricted, some with a concave side, some widened above, others below the constriction. Basidia 36 – 60 x 6-8 µm, 4-spored, often mixed with a few (1),2,(3)-spored basidia. Hymenophoral trama subregular (internal gill tissue not quite regular), with elements inflated, 45 – 115 x 9-15 µm. Pileipellis (cap “skin”) an ixocutis (composed of gelatinous parallel hyphae horizontal to the cap surface) with patches more like an ixotrichoderm (composed of gelatinous parallel hyphae perpendicular to the surface, like upright hairs), up to 60 µm thick.
Description following and adapted from Boertmann D (1995) The genus Hygrocybe. Fungi of Northern Europe 1. Danish Mycological Society, 1–184.