Beach Brittlestem

Typically small- to medium-sized, P. ammophila is found growing terrestrial or in small clumps near marram grass. The cap is a light clay-brown or tan when younger and about 1 to 4 centimetres (0.4 to 1.6 in) in diameter. Although the cap is generally smooth, it possesses microscopically tiny hairs and is often coated with sand particles. The tissue is not hygrophanous and therefore does not change colour with moisture loss and absorption, but the mushrooms do darken to a dark brown as they age. Cap shape begins as campanulate or convex, gradually flattening and possibly becoming depressed in shape. The gills of P. ammophila are crowded and attached to the stem usually broadly (adnate) but occasionally narrowly (adnexed). At a very young age they may be a pallid brown, but for most of the lifespan are dark brown, sometimes turning black. The stipe/stem is light grey to pale brown and centrally attached to the cap. The surface is smooth, sometimes with small vertical ridges. It is deeply rooted in the substrate for feeding on the roots of marram grass and for stability in its sand dune habitat. Above ground, its height is typically 3 to 7 cm (1.2 to 2.8 in) tall and its diameter is slender, about 2 to 5 mm (0.08 to 0.20 in). There is no ring. The basidia bear four spores. The spores are dark brown and smooth, ellipsoid in shape, and 10 to 11 μm × 6 to 7 μm. …

Psathyrella ammophila has a wide but sparse distribution throughout the European continent and in limited coastal locations outside Europe, with records of collection in Algeria, New Zealand, and Canada. It can sometimes be found near the shoreline, inside the littoral zone, but is most often encountered in more stable and established sand dunes and dune slacks inland. The presence of marram grass nearby is a key aspect of its habitat, as it has a symbiotic (specifically, commensal) relationship with the plants, using their decaying roots as food. The mushrooms grow singly or in clumps and are, to some degree, sympatric with the fly Delia albula. The fungivorous larvae of the fly develops in P. ammophila parasitically, though will also attack other fungi.