Identification of the Larger Fungi. Roy Watling
R. nigricans (Mérat) Fries Blackening russula
Cap: width 75–200 mm. Stem: width 15–35 mm; length 25–75 mm.
Cap: cream-coloured then flushed sooty brown, finally black as if scorched by proximity to bonfire.
Stem: white then dark brown.
Gills: pale ochre reddening when bruised, thick and very distant.
Flesh: white slowly dull red on cutting then brown and finally changing soot-colour after some time.
Spore-print: white.
Common in deciduous woods.
R. xerampelina (Secretan) Fries
Cap: width 50–140 mm. Stem: width 15–30 mm; length 40–60 mm.
Cap: deep blood-red or brownish red.
Stem: white with a flush of red towards the base.
Gills: cream then ochraceous.
Flesh: white staining brownish and smelling strongly of fish- or crab-paste, and staining dark green when a crystal of green iron sulphate is rubbed into it.
Spore-print: deep cream-colour.
Common in mixed woods; a very variable fungus with many colour-forms, but easily recognised by the green reaction with ferrous sulphate.
Lactarius turpis (Weinm.) Fries Ugly milk-cap
Cap: width 60–200 mm. Stem: width 10–25 mm; length 40–75 mm.
Description:
Cap: firm, convex usually with a central depression at maturity, dark olive-brown or dark greyish olive with a yellow-tawny, woolly margin when young which soon disappears, and the whole cap becomes sticky with age and turns deep purple when a drop of household ammonia is placed on it.
Stem: short, stout, similarly coloured to the cap except for the distinctly ochraceous apex, slimy and pitted.
Gills: crowded, cream-coloured to pale straw-coloured, but soon spotted with dirty brown, particularly when bruised.
Flesh: white or greyish ochre exuding a milk-like liquid which lacks a distinct smell and is white and unchanging when exposed to the air.
Spore-print: pale pinkish buff.
Spores: subglobose or ellipsoid and covered in a network of strongly developed, raised lines interconnected by finer ones, both of which stain blue-black in solutions containing iodine, generally 8 × 6 µm in size (7–8 × 6–7 µm).
Marginal cystidia: lance- or spindle-shaped and filled with oily contents.
Facial cystidia: similar to marginal cystidia.
Habitat & Distribution: Common in woods and copses, or on heaths especially in boggy places but always where birch is growing.
General Information: Easily recognised by the dull colours and purple reaction with alkali; there is no British species with which L. turpis can be mistaken. The purple reaction is similar to that found in the familiar school laboratory reagent litmus, for the compound found in L. turpis turns purple in alkali and reddens in acidic solutions. First discovered by Harley in 1893 this reaction marked the beginning of a whole series of chemical studies on the agarics which has led to the discovery of many unique compounds.
Illustrations: Hvass 214 (but too green); LH 213; NB 1133; WD 381.
General notes on the genus Lactarius
There is little doubt that the genus Russula and the genus Lactarius are closely related; in fact they stand aside from the other agarics in the very important character mentioned on page 46. In Europe the easiest distinction between the two genera is that members of the genus Lactarius exude a milk-like juice which may be white or variously coloured depending on the species involved (e.g. purple in L. uvidus (Fries) Fries, yellow in L. chrysorheus Fries). The cap, stem and frequently the gills are brittle and when broken liberate the milk-like liquid; when the fruit-body is dry, however, the presence of this liquid may be difficult to demonstrate. The spores have a blue-black ornamentation under the microscope when mounted in iodine, and although when in mass the colours are not as varied as those found in the genus Russula there is every likelihood that they will play an important role in the classification of the group in the future. The colour of the spore-print has been rather neglected, although the genus includes some rather unusual fungi.
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