Identification of the Larger Fungi. Roy Watling
recognised by the poorly developed ring, overall golden-yellow colour and pale yellow viscidness on the cap which comes off on to the fingers when the fruit-body is handled. There are several closely related fungi which also grow with coniferous trees, e.g. Suillus luteus Fries, ‘Slippery jack’, but many need experience in order to identify them. All these fungi were formerly placed in the genus Boletus, because of the fleshy fruit-body with pores beneath the cap. The larch-bolete receives its common name from the close relationship of the fungus with the larch. On drying S. luteus and S. grevillei may strongly resemble one another but the former can be distinguished when fresh by the chocolate brown, sepia, or purplish brown cap and the large whitish, lilac-tinted ring.
Plate 1. Fleshy fungi: Spores borne within tubes
Larger illustration
Plate 2. Fleshy fungi: Spores borne within tubes
Larger illustration
Species of Suillus are edible and rank highly in continental cook-books, although they have disagreeably gelatinous-slimy caps, a character, in fact, which helps to separate them from other fleshy pore-fungi.
Illustrations: F 41a; Hvass 257; ML 187; NB 1044; WD 842.
Boletus badius Fries Bay-coloured bolete
Cap: width 70–130 mm. Stem: width 34–37 mm; length 110–125 mm. (36–40 mm at base).
Description: Plate 3.
Cap: hemispherical, minutely velvety, but soon becoming smooth and distinctly viscid in wet weather, red-brown flushed with date-brown and darkening even more with age and in moist weather to become bay-brown.
Stem: similarly coloured to the cap but paler particularly at the apex, smooth or with faint, longitudinal furrows which are often powdered with minute, dark brown dots.
Tubes: adnate or depressed about the stem, lemon-yellow but immediately blue-green when exposed to the air and with angular, rather large similarly coloured, pores which equally rapidly turn blue-green when touched.
Flesh: strongly smelling earthy, pale yellow but becoming pinkish in centre of the cap, and blue in the stem and above the tubes when exposed to the air, but finally becoming dirty yellow throughout.
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).
The boletes have long been classified in the genus Boletus, but instead of referring all the pored, fleshy fungi to a single large genus several genera are now recognised. The separation of these genera is based on differences in colour of the spore-print and differences in the anatomy of the tubes, cap and stem, etc., e.g. members of the genus Suillus have colourless or pale coloured dots on the stem exuding a resin-like liquid in wet weather, which is clear and glistening in some species but turbid and whitish in others, gradually darkening and hardening so that the stem is ultimately covered in dark brown or reddish smears or spots; members of the genus Leccinum on the other hand never exude liquid and have coarse or fine roughenings on the stem which are usually dark, but may commence white and ultimately darken depending on the species; many species of Boletus possess a very distinct raised network all over the stem, whilst others have it present only in part, or have minute, often brightly coloured, dots replacing it.
Plate 3. Fleshy fungi: Spores borne within tubes
Larger illustration
Within this single, yet not particularly large, group of fungi, several biological phenomena are demonstrable. There is good evidence that the majority of British boletes are mycorrhizal; several species are known to be associated only with one species of tree or group of closely related tree-species. Thus Suillus grevillei and S. aeruginascens (Secretan) Singer grow in association with larch trees; S. luteus and Boletus badius in contrast grow in association with pine trees; Leccinum scabrum with birch trees; L. aurantiacum (Fries) S. F. Gray, with poplar trees and L. quercinum (Pilát) Green & Watling, with oak trees.
Boletus edulis can be separated into several distinct subspecies which are associated with different trees; the two commonest subspecies are those associated with birch and with beech trees. It is well known that although present in this country during the warmer periods of the Ice-Age, larch neither survived the intense cold of the last advance of the ice nor migrated back into Britain after the ice had melted. Thus all larches which we see in Britain have been planted by man. There is little doubt that mycelia of many fungi were introduced along with these plants very probably including the mycelium of the larch-bolete. A similar pattern can be seen with other introduced trees, although not to such a marked degree, e.g. spruce trees. The beech tree, however, is native to the south of England, unlike the larch returning to this country after the ice had melted; it has been planted extensively outside its former range in northern areas of the British Isles taking with it its associated fungi. There is some evidence that some stocks of beech and fungi have been introduced from continental Europe in comparatively recent times.
A parallel, yet inexplicable association is found between the bolete Suillus