Part 12

d. Medium, rarely large, agarics with dry, silky to innately fibrillose caps, slender stems and frequently with at least part of the fruit-body yellow, orange or reddish--Dermocybe

e. Medium to small agarics with silky fibrillose, non-hygrophanous caps which may become tacky in wet weather and then usually with robust, clavate-bulbous stems--Sericeocybe

f. Small, less frequently medium or large agarics, all with distinctly hygrophanous caps--Hydrocybe.

In several continental books some or all of these divisions are recognised as distinct genera in their own right. The subgenus Telamonia which occurs in many texts was formerly thought to differ from Hydrocybe in the presence of a universal veil; the universal veil is a second veil which completely envelopes the fruit-body when it is young and is in addition to the cortina. However, the modern treatment would seem to suggest that the presence of the universal veil is not of the utmost importance and so the two subgenera are incorporated into one. The name Hydrocybe reflects the character of changing colour as it dries out because of the loss of water. Within each subgenus the species are distinguished by the colour of the young gills and of the cap, the veil colour and texture, and microscopic characters of the spores, particularly their size.

The majority of species of Cortinarius are mycorrhizal and like the boletes possess very specific relationships with tree species. Thus some are typical of coniferous woodland and others typical of deciduous woodland in general, whilst others typify woods of a particular tree, e.g. beech, oak, birch, pine, larch. Some species are characteristic of woods on limestone or chalky soils (calcareous) whilst others are characteristic of woods on sandy, heathy acidic soils. For example, Cortinarius armillatus (Fries) Fries which is found in damp woods and possesses one or more cinnabar-red or scarlet zones on the stem and red fibrils at the stem-base appears to be connected with birch. Several species are associated with native trees whilst others have undoubtedly been introduced from abroad. They are very important in the economy of the woodland ecosystem.

One of the most beautiful and easily distinguished of our British species is Cortinarius violaceus (Fries) Fries which has uniformly deep violet-coloured stem and cap and coloured cystidia on the gill-margin, a character unusual in Cortinarius.

No species are known to be truly poisonous and many species are known to be edible, but many are too small to be of any value. Some of the larger species are regarded as good to eat, but frequently are too scarce. Thus the necessity for experience to recognise the different species, coupled with their often unpleasant tastes make them an unimportant group of agarics for eating.

~Russula ochroleuca~ (Secretan) Fries

Common yellow russula

Cap: width 50-100 mm. Stem: width 20-35 mm; length 50-100 mm.

Description: Plate 7.

Cap: yellow-ochre or dull yellow becoming paler with age, or flushed faintly greyish green, convex but soon expanding and becoming flat or depressed in the centre, smooth, or granular when young and slightly tacky in wet weather, faintly striate at the margin.

Stem: white at first then flushed slightly greyish, smooth or wrinkled, firm at first but quickly becoming soft and fragile.

Flesh: brittle, firm at first then soft, white, yellow under cap-centre.

Gills: white at first then flushed pale cream-colour, brittle, adnexed to free, rather distant.

Spore-print: faintly cream when freshly prepared.

Spores: medium-sized, hyaline, broadly ellipsoid or subglobose to almost globose, coarsely ornamented with prominent warts which stain blue-black when mounted in solutions containing iodine and which are faintly interconnected by low ridges, about 8 × 7 µm in size (9-10 × 7-8 µm).

Marginal cystidia: prominent, lance- to spindle-shaped and often filled with oily material.

Facial cystidia: similar in shape to marginal cystidia and projecting some distance from the gill-face.

Habitat & Distribution: Commonly found in mixed woods from summer until late autumn.

General Information: Easily recognised by the ochre-yellow cap, very pale cream-coloured spore-print and greying stem. Two other yellow-capped species of Russula are commonly found. R. claroflava Grove with yellow spore-print and blackening fruit-body which grows with birches in boggy places, and R. lutea (Fries) S. F. Gray which is much smaller, having a cap up to 50 mm and very deep egg-yellow gills and spore-print; it grows in deciduous woods.

Illustrations: F 22a; Hvass 226; LH 119; NB 137¹; WD 49¹.

General notes on the genus Russula

A large genus with nearly one hundred distinct species in the British Isles and several others yet unrecognised or undocumented. This genus is composed generally of large toadstools often beautifully coloured, indeed the majority have brightly coloured caps in reds, purples, yellows or greens depending on the species although a few are predominantly white bruising reddish brown or grey to some degree.

Such large and distinctive fungi one would think would be the easiest members of our flora to identify, unfortunately they are not. They form a group quite isolated in their relations, the only close relatives being members of the genus Lactarius, to be dealt with later (see p. 50). The flesh of members of both Lactarius and Russula contains groups of rounded cells, a feature unique amongst agarics and explains why in Russula the fruit-bodies, cap and gills and sometimes the stem are brittle and easily break if crushed between the fingers. The fruit-body does not exude a milky liquid when the flesh is broken.

The spore-print varies, depending on the species involved, from white to deep ochre and individual spores are covered in a coarse ornamentation which is composed of isolated warts or warts interconnected by raised lines, or mixtures of both. The ornamentation stains deep blue-black when the spores are mounted in solutions containing iodine and the pattern which is produced appears in many cases to be of a specific character.

The majority of the species, if not all north-temperate species are mycorrhizal and the familiar host-tree fungus relationship can be recognised:--

R. claroflava Grove, with birch in boggy places, R. emetica (Fries) S. F. Gray with pine in wet places, R. betularum Hora with birch in grassy copses and R. sardonia Fries with pines. Brief notes are here included giving the basic characters of eight common species, but it must be appreciated the identification of many species within this genus is difficult.