Identification of the Larger Fungi. Roy Watling
its close relative Gomphidius roseus (Fries) Karsten where the mycelium of two fungi are found intertwined forming a close association! Parasitism although rare is also found amongst the boletes, and an uncommon parasitism at that—a fungus on a fungus; for example in Britain although infrequent Boletus parasiticus Fries grows attached and ultimately replaces the spore-tissue of the common earth-ball (Scleroderma, see p. 192).
Those fungi which grow on dead and decaying substrates are called saprophytes and although the greater number of higher fungi would be included in this class of organisms the character is infrequent amongst the boletes. One British example of this type of fungus is the rare Boletus sphaerocephalus Barla which grows on woody debris.
Chemists have long been interested in boletes, for as noted above the flesh of some species when exposed to the atmosphere turns vivid colours, a feature often incorporated into the Latin name, e.g. Boletus purpureus Persoon, from the purple colours produced whenever the fruit-body is handled. The reaction appears to be an oxidation where in the presence of an enzyme and oxygen a pigmented substance or substances are produced. What the significance of these colour-changes is in nature is as yet unknown; however, what is interesting is that many of the chemicals involved are unique and have only recently been analysed completely; they are related to the quinones.
There is little doubt that it is this rapid and intense blueing of the flesh of many boletes that has lead to a belief that they are poisonous. It is uncertain whether there are any truly toxic species of Boletus but several have unpleasant smells and tastes which make them very unattractive. Boletus edulis is the important ingredient, however, which gives the distinctive taste to so-called dried mushroom soup. Thousands of fruit-bodies are collected annually in the forests of Europe to be later dried and processed for incorporation into soup. Boletes appear to form an important part of the diet of several rodents and deer and in Scandinavia in the diet of reindeer.
Probably one of the most obscure of our British boletes is Strobilomyces floccopus (Fries) Karsten, the ‘Old Man of the Woods’. It has a black, white and grey woolly, scaly cap and stem, and the flesh distinctly reddens when exposed to the air. The spores are almost spherical, purple-black in colour and covered in a coarse network when seen under the microscope. All these characters readily separate Strobilomyces from all other European boletes; however, in Australasia, members of this and related genera form a very important part of the flora.
Chroogomphus rutilus (Fries) O. K. Miller Pine spike-cap
Cap: width 30–150 mm. Stem: width 10–18 mm; length 60–120 mm.
Description:
Cap: convex with a pronounced often sharp umbo, wine-coloured, flushed with bronze-colour at centre and yellow or ochre at margin, viscid but soon drying and then becoming paler and quite shiny.
Stem: yellowish orange, apricot-coloured or peach-coloured, streaked with dull wine-colour, spindle-shaped or narrowed gradually to the apex from a more or less pointed base.
Gills: arcuate-decurrent, distant, at first greyish sepia then dingy purplish with paler margin, but finally entirely dark purplish brown.
Flesh: lacking distinctive smell and reddish yellow or pale tan in the cap, rich apricot- or peach-colour towards the stem-base.
Spore-print: purplish black.
Spores: very long, spindle-shaped, smooth, olivaceous purple and greater than 20 µm in length (20–23 × 6–7 µm).
Marginal cystidia: cylindrical to lance-shaped and up to 100 × 15 µm.
Facial cystidia: similar to marginal cystidia.
Habitat & Distribution: Found in pine woods, usually solitary or in small groups. Fairly common throughout the British Isles and characteristic of Scots Pine woods.
General Information: This fungus can be distinguished by the purplish or wine-coloured cap and the gills being pigmented from youth. There is only one other British species of this genus, i.e. C. corallinus Miller & Watling.
Chroogomphus is separated from Gomphidius by the flesh having an intense blue-black reaction when placed in solutions containing iodine, and the gills being coloured from their youth. In many books Chroogomphus is placed in synonymy with the genus Gomphidius. However, Gomphidius glutinosus (Fries) Fries, G. roseus (Fries) Karsten and G. maculatus Fries all have whitish gills when immature which gradually darken, and their flesh simply turns orange-brown in solutions of iodine. G. glutinosus is uniformly grey in colour and is most frequently found under spruce and other introduced conifers: G. roseus has a pale-pinkish coloured cap and white stem, and grows with pine; G. maculatus grows under larch and is flushed lilaceous at first but becomes strongly spotted with brown when handled.
Illustrations: Hvass 192; LH 213; WD 833.
Plate 4. Fleshy fungi: Spores blackish and borne on gills
Larger illustration
Paxillus involutus (Fries) Karsten Brown roll-rim
Cap: width 50–120 mm. Stem: width 8–15 mm; height 30–75 mm.
Description:
Cap: at first convex with a strongly inrolled, downy margin, but then expanded and later frequently depressed towards the centre, clay-coloured, ochre or yellow-rust, slightly velvety but becoming smooth or sticky particularly in wet weather and readily bruising red-brown when fresh.
Stem: central or slightly eccentric, thickened upwards, fibrillose-silky, similarly coloured to the cap but typically streaked with red-brown particularly with age.
Gills: ochre or yellow-brown then rust and finally darker brown, decurrent, crowded, often branched and united about the apex of the stem; easily peeled from the flesh with the fingers and rapidly becoming red-brown on handling.
Flesh: thick, soft and with slightly astringent smell and yellowish to brownish but becoming red-brown after exposure to the air.
Spore-print: rust-brown.
Spores: medium-sized, ellipsoid, smooth, deep yellow-brown and rarely greater than 10 µm in length (8–10 × 5–6 µm).
Marginal cystidia: numerous lance-shaped or spindle-shaped.
Facial cystidia: scattered and similar in shape to marginal cystidia.
Habitat & Distribution: Found on heaths and in mixed woods, particularly where birch has or is now growing, or even accompanying solitary birch trees.
General Information: This fungus is easily recognisable by the strongly inrolled, woolly margin of the cap and yellow-brown gills which are easily separable from the cap-flesh. P. rubicundulus P. D. Orton is similar but grows under alder and has yellow gills unchanging when handled and dark scales on the cap. P. atrotomentosus (Fries) Fries and P. panuoides (Fries) Fries both grow on coniferous wood and have smaller spores; the former is recognised by the dark brown to almost black shaggy stem and the latter by the shell-shaped cap devoid almost completely of a stem.
Illustrations: F 41c; Hvass 189; LH 185; NB 1158; WD 702.
Plate 5. Fleshy fungi: Spores brown and borne on gills
Larger illustration
Cortinarius pseudosalor