Field Mycology Volume 6(3), July 2005
THE GENUINE BOLETUS ARMENIACUS IN BRITAIN Alan Hills1 & Geoffrey Kibby2 ʻMegeraʼ, Acremead Road, Wheatley, Oxon OX33 1NZ & 2editorial address
oletus armeniacus Quél. (often placed in the genus Xerocomus) was described in 1884 but in the 121 years since it has been the subject of constant confusion. Although most frequently recorded in Italy, France and Spain, there have also been records from as far north as the Netherlands. There are also scattered records from a number of British counties. All of these latter records must be treated with caution however, since they are usually based entirely on field characters, in particular cap colour, and have little hard evidence to back them up.Thanks to the recent work of boletologists Heidi Ladurner and Giampaulo Simonini
(2003), we now have a much clearer understanding of its specific characteristics and delimitation. Although the cap usually has the distinctive apricot-orange to reddish tones that gives the species its name (the common apricot is Prunus armeniaca), this colour can also be found in several other species and is in any case extremely variable. Note also that the cap can crack extensively and can again cause confusion with species such as B. ripariellus, B. cisalpinus and B. chrysenteron etc. The best distinguishing characters are microscopic and chemical: (1) The hyphae of the cap cuticle when treated with a solution
Boletus armeniacus found by Alan Hills and Steve Kelly in an Oxfordshire woodland growing under Quercus petraea, September 1, 2004. This large collection not only showed the striking reddish-apricot cap colours which give the species its name, it also fitted microscopically! Photograph © A. Hills.
Field Mycology Volume 6(3), July 2005
Photographs of the cuticular hyphae (above) and the cheilocystidia (below) of Boletus armeniacus © A. Hills.
bright reddish-apricot cap colours and orange-buff stems, often strongly cracked cap cuticle and apricot flesh in the stem base. Subsequent microscopic examination revealed the distinctive plaques on the cuticular cells. This was undoubtedly a large collection of the genuine B. armeniacus. So the species is indeed present in Britain and is likely to be found in other counties in the south and perhaps warm locations further north. As Ladurner and Simonini say: “X. armeniacus is one of the frequently misidentified taxa in Xerocomus. Macroscopic delimitation from similar species is difficult and not always satisfying”. Collections and dried herbarium material must be examined microscopically if one is to be certain of this species. Only this way can we discover its true distribution in Britain.
of Congo red usually reveal small congophilous plaques adhering to the outside of the cell walls. These can be clearly seen in the photograph at the top of this page. The cheilocystidia, although prominent, are typical for most members of this group. (2) The context of the stem base and of the cap surface becomes a deep green-blue when treated with a solution of ferrous sulphate. Corroborating macroscopic features apart from the cap colour include a strong apricot to rhubarb colour in the flesh of the stem base. All parts of the fungus can fade to a dull ochraceous buff with age. B. armeniacus is a thermophilic species growing in association with Quercus, Tilia, Fagus, Castanea and even Pinus, to be expected in the warmer southern counties of Britain. However, examination by the senior author of collections in the Kew herbarium revealed that none of them showed the necessary characteristics of this species and their identifications must be considered as highly doubtful. So while out on a mushroom foray with Steve Kelly in a wood in Oxfordshire he was greatly surprised to come across a large collection of fruitbodies which seemed to fit the profile of this species.They all showed the
Reference Ladurner, H. & Simonini, G. (2003). Fungi Europaei Vol. 8, Xerocomus s.l.