A rare British truffle

[Chris Yeates]

hah! - that got you reading! . . . .

I am currently curating my personal mycological herbarium, with a view to making sure that the more significant finds are lodged with suitable institutions (principally at RBG Kew). Coming across a packet labelled Melanogaster intermedius, I decided that it would be worthwhile checking the identification, and also taking some photo's down the microscope – something I was not able to do in 1991.

Pegler, Spooner & Young in British Truffles, (Kew, 1993) say of this species

"A very rare species, which was based on only one collection. According to Svrcek (1958) it is known from Germany and Czechoslovakia, and Zeller & Dodge (1936c) list the species from California, U.S.A."

That type collection was made by C.E.Broome from Spye Park, Wiltshire in 1843; there have been further collections, both in 2004, from Windsor Great Park and Epping Forest. So presumably this collection was the second British one.

The distinction between the three British species of Melanogaster is based around spore shape and dimensions; as the name implies M. intermedius lies in the middle with regard to spore size.

Melanogaster broomeianus – spores 6.5-10.5. x 3.5-5 microns, narrowly oblong or cylindrical
Melanogaster intermedius – spores 10-14.5 x 6.5-9 microns, obovoid to ellipsoid
Melanogaster ambiguus – spores 14-20 x 8-10.5 microns, soon rhomboid or lemon-shaped

The spores of my collection are rather narrow with regard to the descriptions above, being in the range 10.4-12.4 x 6-6.5 microns, but the shape is absolutely spot-on and the spore dimensions do not come anywhere near the other two species, so I am happy with my original (and re-checked) ID.

The members of the old pseudo-taxon "Gasteromycetes" have now been re-disposed within other, often more familiar groups; so for example Melanogaster has now been placed within the Boletes - close to Paxillus in fact; not that you would ever guess that from its general appearance:



the specimen was a little over 1 cm in diameter; I collected it on one of the British Mycological Society's now-defunct Truffle Hunts, at Slindon Common, West Sussex in July 1991 - in fact I think I actually found all three British Melanogaster species that week (happy days), but hadn't appreciated at the time how rare intermedius is

here are some views of the spores:



oh! and while you could eat it - it is not edible, and I must concur with Andreas - there are no British truffles worth eating

cheers

Chris

[FungiJohn]

Nice one Chris

[Chris Yeates]

Another Melanogaster . . .

Working through further collections in my herbarium I came across a packet containing a collection (from the same BMS Truffle Hunt), made at The Cut area of the woodland known as The Mens, NE of Petworth in Sussex

two basidiomes were found by Helen, a former partner (and - as a trained archaeologist - very good at finding buried stuff!); I am pleased to see that again my I/D made in 1991 is OK

it's Melanogaster ambiguus: much more common than the previous species, but nonetheless requiring careful searching for

here are views of a sectioned fruit-body (about 1.5cm diameter when fresh) showing the internal and external appearance; (remember this is dried material, but you can clearly see the compartmentalised interior)



and here are the spores which show the characteristic lemon shape (technically 'limoniform'), with a drawn out apical 'nipple' quite unlike the spores of M. intermedius above:



the spores are also distinctly larger

I am now hoping to find the specimen of M. broomeianus which I am sure we also made on that foray - to complete the set . . . .

cheers

Chris