Marasmius oreades, also known as Fairy Ring Marasmius, is a small agaric that produces characteristic rings in lawns. It has a bell-shaped to convex cap, which becomes flatter with a broad umbo as it ages. The mushroom belongs to the family Marasmiaceae, which contains about 500 species of agarics. It is widely distributed and commonly found in grassy areas, such as lawns, meadows, and pastures.

Cap at first convex, then flat to cup-shaped with a low central hump that is often a darker shade. The Colour varies from light beige to brown-yellow. The margins are usually crinkled and almost transparent and streaky in damp weather. They turn lighter in dry weather and regain their colour in more humid conditions. The flesh is whitish buff, thick at the centre, otherwise thin. Gills fairly broad, attached to the stem or free from it, appearing almost distant. They are creamy white at first, becoming ochraceous cream or pale tan in colour. Stem tall, coloured as the cap, smooth or finely scurfy, slender, more or less equal, whitish downy at the base and slightly rooting, stiff. It has no ring. Spore print white.

Microscopic Features: The spores are ellipsoidal to pip-shaped, exhibiting a smooth surface. They measure 8-11μm in length and 4-6μm in width and are inamyloid.

Marasmius oreades on the First Nature Web site.
Marasmius oreades on the mykoweb.com Web site.
Marasmius oreades on the MushroomExpert.Com Web site.