Stropharia

The genus Stropharia (sometimes known by the common name roundheads) is a group of medium to large agarics with a distinct membranous annulus. The scientific name is derived from the Greek 'στροφος/strophos' meaning "belt", in reference to it. Spore print color is generally medium to dark purple-brown, except for a few species that have rusty-brown spores. There is a great deal of variation, however, since this group as presently delimited is polyphyletic. Members of the core clade of Stropharia are characterized by crystalline acanthocytes among the hyphae that make up the rhizoids at the base of the mushroom.

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Well-known members of this genus include the edible Stropharia rugosoannulata and the blue-green verdigris agarics (Stropharia aeruginosa and allies).

Section Stropholoma is often treated as part of Stropharia, though some authorities place it in the genus Hypholoma. It has features that are intermediate between the two genera, lacking the distinct membranous annulus of other Stropharia. This group includes a number of mushrooms found commonly in woodchip beds, such as Stropharia aurantiaca, S. percevalii, and S. riparia.

Recent molecular work shows the a core group of the genus most closely related to Hypholoma and Pholiota. Other such as S. semiglobata are more distantly related.

Stropharia are not generally regarded as good eating and there are doubts over the edibility of several species. However S. rugosoannulata is regarded as a good edible and is often cultivated.