Marasmius rotula

Marasmius rotula is a tiny, delicate saprobic mushroom recognized by its white, deeply pleated parachute-like cap and a distinctive collar around the stem to which its widely spaced gills attach. It grows in clusters on dead hardwood twigs, branches, and woody debris, and is widespread across temperate northern latitudes. Bitter and far too small to eat, it is a non-toxic decomposer rather than an edible or medicinal species.

History

Marasmius rotula was first described by Giovanni Antonio Scopoli and later sanctioned by Elias Magnus Fries, who placed it in the genus Marasmius. The genus name comes from the Greek marasmos, "to wither," reflecting the ability of these mushrooms to dry out and then revive when moisture returns. The species epithet rotula is Latin for "small wheel," describing the radial, spoke-like arrangement of the gills around the collar that gives the fungus its common name, the pinwheel mushroom.

Overview

Marasmius rotula is a wood-decay saprobe that breaks down dead branches and twigs, contributing to nutrient cycling in temperate forests. The minute white cap rarely exceeds 2 cm across and is held on a slender, wiry, dark-based stem. Its defining feature is the collarium: a free ring around the top of the stem from which the few, well-spaced gills radiate, so they do not touch the stem itself. Like other Marasmius species, it can shrivel during dry spells and rehydrate after rain. It has no culinary or medicinal use and is considered inedible, though it is not poisonous.