About Clavulinopsis helvola (Pers.) Corner
Clavulinopsis helvola has fruit bodies that are cylindrical to narrowly club-shaped, measuring up to 60 mm in height and 3 mm in width. Fruit bodies range in color from lemon yellow to deep yellow and have an indistinct stem. Microscopically, its basidiospores are hyaline, shaped from subglobose to ellipsoid, and measure 5 to 6.5 μm by 4.5 to 6 μm. The spores have large, sparse spines that can reach up to 1.5 μm in length. This species was first described from Europe, with a recent epitype collected from Slovakia. It is widely distributed across Europe, and has also been reported from India, Japan, China, the United States, and Brazil. Clavulinopsis helvola grows singly or in small clusters on the ground, and is presumed to be saprotrophic. In America and Asia, it grows in woodland; in Europe, it generally grows in agriculturally unimproved, short-sward grassland such as pastures and lawns. This type of habitat, called waxcap grassland, is declining and threatened, but Clavulinopsis helvola is one of the more common species found in these grasslands and is not currently considered a species of conservation concern.
