Myriostoma coliforme (pepperpot earthstar)

Myriostoma coliforme has fruitbodies which are rounded when young and, as in all earthstars, comprise two main layers. Mature, unopened fruitbodies are mostly 3 – 8 cm in diameter. At this stage, the outer layer or exoperidium splits into 5 – 10 or so rays which turn back in a star-like pattern to expose the inner spore-bearing sac or endoperidial body. The exoperidium is 5 – 6 mm thick, and the rays turn back and arch somewhat under the fruitbody, raising it slightly, as in most earthstars, facilitating spore dispersal. The expanded fruitbody varies in size, but is commonly 5 – 10 cm diameter.

The spore sac is rounded, usually subglobose, varying mostly from 15 – 50 mm in diameter., and is attached to the exoperidium by multiple stalks each up to c. 5 mm high and rounded to angular or flattened in cross-section. The spore sac is grey to brown when mature, often shiny with age, and is perforated by numerous irregularly dispersed pores each roughly circular, 1 – 3 mm diameter, through which the spores are dispersed. It encloses the gleba which, at maturity, as in all earthstars and puffballs, comprises a powdery spore mass. Spores are brown in mass at maturity, and under the microscope globose with distinctive flange and 4 – 6 μm diam. It fruits mainly in autumn, but the fruitbodies are quite tough and resistant and may be found throughout the year.

The pepperpot earthstar was included in 2004 in a list of 33 species proposed for protection under the Bern Convention by the European Council for Conservation of Fungi (ECCF), and included on the Red Lists of 12 European countries.

Myriostoma coliforme was last collected in 1880 in Norfolk, and remained unrecorded thereafter until a specimen was discovered in Suffolk in 2006. It seems unlikely that such a distinctive fungus could have remained undetected in Britain for over 120 years, and a reintroduction seems plausible. However, it is interesting that the species was refound close to one of its original localities. The new collection was of an old, weathered specimen found in February 2006 on a sandy bank at the edge of oak woodland near Ipswich.