Spore-print: brown with a distinct olivaceous flush.
Spores: long, spindle-shaped, smooth, honey-coloured under the microscope and greater than 12 µm in length (13-15 µm long × 5 µm broad).
Marginal cystidia: numerous, flask-shaped and slightly yellowish.
Facial cystidia: scattered and infrequent and similar to marginal cystidia in shape.
Habitat & Distribution: Found in woods, especially accompanying pine trees, but often found fruiting on the site of former coniferous trees, even years after the trunks or the stumps have been removed.
General Information: This fungus is recognised by the rounded, red-brown cap, coupled with the pale yellow flesh and greenish yellow tubes, both of which become greenish blue when exposed to the air. There are several species in the genus Boletus which stain blue at the slightest touch or when the flesh is exposed to the air, e.g. B. erythropus (Fries) Secretan, a common bolete with a dark olivaceous cap, orange pores and red-dotted stem.
The flesh of some species of Boletus, e.g. B. edulis Fries, however, remains unchanged or at most becomes flushed slightly pinkish. Although many people say they recognise B. edulis, the ‘Penny-bun’ bolete—a name derived from the colour of the cap, there is some doubt as to whether the true B. edulis is common in Britain as we are led to believe. B. edulis and its relatives are highly recommended as edible (see [p. 35]). B. badius is also edible, but it is ill-advised to eat any bolete which turns blue when cut open.
Illustrations: B. badius—F 38c; Hvass 248 (not very good); LH 191; NB 1095; WD 851. B. edulis: F 42a; Hvass 246; LH 191; NB 1433.
General notes on Boletes
There are nearly seventy boletes recorded for the British Isles and evidence of others which have as yet not been fully documented. As a group they are characterised by being fleshy, possessing a central stem and producing their spores within the tubes, and not on gills as in the common mushroom. It is the first character by which the boletes differ so markedly from the other pored fungi, such as the ‘Scaly Polypore’ (see [p. 140]).