Porpoloma metapodium

This rather robust species has no veil and with its rather dull grey brown colours has the general outline of a member of the genus Tricholoma. Indeed both genera have white spores but beyond this there are differences that have split the two apart. The white spores of Porpoloma show an amyloid reaction (turning blue black) in the iodine based solution ‘Melzer’s Reagent’, which Tricholoma spores do not. The emarginate gills (rising towards the cap before joining the stem) that are so characteristic of Tricholoma are not as distinct in Porpoloma, where they are described as being adnate to emarginate. Another big difference is that where Tricholoma are believed to be ectomycorrhizal (symbiotic with trees), Porpoloma is thought to be a saprotroph (feeding off dead organic matter) – something that frees it from needing a symbiont/partner and enables it to take advantage of the dead plant matter found in the unimproved grassland habitats of the UK.

Whilst it is not formally one of the Waxcap Grassland (see references below) species used to assess the conservation interest of some of our old unimproved grasslands i.e. CHEGD species:

• Clavariaceae (Fairy Clubs),

• Hygrocybe (Waxcaps),

• Entoloma (Pinkgills),

• Geoglossaceae (Earthtongues) and

• Dermoloma (Crazed Caps),

Porpoloma is certainly worth noting and is usually a species that would be mentioned if found when assessing an old grassland for its fungal importance.

Fruiting

In Scotland this species starts to appear in July (6 records), peaks in September (41 records) and tails off in October (9 records) with no records so far out with this time period.

Habitat

Usually associated with dry, unimproved grassland. Funga Nordica suggests that it is also known from forests in some areas of continental Europe but this is not the case so far in Scotland.

Distribution

The Checklist gives the distribution as ‘unknown’ throughout but in general widespread. The total number of sites for this species on the Fungal Records Database of Britain and Ireland (FRDBI) is 178 with 104 of these from Scotland. The species is clearly widespread but closer investigation of the figures suggest that there are actually only about 30 sites known for this species in Scotland with repeat visits to known sites suggesting that this is a regular fruiter. Indeed a site on Mar Lodge has only missed 3 years since 1999. You can view the FRDBI records to 2007 here.

Listen to

• BBC Radio 4: The Living World: Waxcap Grasslands

See also

• Aberystwyth Waxcap Website

• Guidelines for selection of biological SSSIs: Chapter 20 - Grassland Fungi

• Status, distribution and definition of mycologically important grasslands in Scotland

• A comparative survey of waxcap-grassland fungi of Ireland and Britain

Liz Holden,

August 2012