Part 40

General Information: This fungus is recognised by the dark fibrils on the cap, the 2-spored basidia easily seen with the low power of a microscope, and the pink gills when young. Much confusion has existed over this fungus and its nearest relatives. It is similar to the ‘Cultivated mushroom’, A. hortensis (Cooke) Pilát, which is offered for sale in shops. However, it differs in several minor details and it may be that A. bisporus is the fungus from which the cultivated mushroom developed, very probably unconsciously by man, but the history of the cultivated mushroom is very obscure. The cultivated mushroom when bought in British shops is white but in the United States two varieties are sold, one with the brownish fibrils predominating and a snow-white one where the fibrils do not darken; the former is frequently found in Europe. The white form is sometimes found in gardens where spent-mushroom spawn is used as mulching around fruit-trees but it has a rounder cap than A. bisporus. The cultivated mushroom accounts for an annual income of £14 million in the British Isles.

Illustrations: A. hortensis--LH 133 (as the forma albida); NB 31⁷; WD 71¹. A. bisporus--Hvass 161; LH 133.

B. BRACKET-FUNGI AND THEIR RELATIVES

Key to major genera

A group of fungi which includes the bracket fungi, hedgehog fungi, fairy-clubs and their relatives; in the majority of species the margin continues to grow through the favourable part of the season and so often envelopes leaves, grass, etc.

1. Spore-bearing layer (hymenium) quite smooth, spread over veins or shallow pores; fruit-body top-shaped, fan-shaped or club-shaped, or spread over the substrate (resupinate) 2

Spore-bearing layer lining the inner surface of tubes or borne on warts or spines 17

2. Fruit-body club-shaped, coral-shaped or distinctly funnel-shaped, fan-like or resembling an agaric 3

Fruit-body resupinate or with poorly developed cap 11

3. Fruit-body coral-like or club-shaped with clubs grouped or branched 4

Fruit-body resembling an agaric or funnel-shaped to fan-shaped 9

4. Fruit-body large, branched with flattened and curled lobes and so resembling a cauliflower Sparassis

Fruit-body of single or grouped clubs or if branched then not resembling a cauliflower, the lobes being cylindrical or only slightly flattened and hardly bent 5

5. Fruit-body small arising from a seed-like structure or growing attached to dead herbaceous plant remains 6

Fruit-body medium to large, simple or branched and usually growing on the ground; one large species grows on wood 7

6. Fruit-body arising from a seed-like body embedded in the plant-tissue or found loose in the soil Typhula

Fruit-body on dead plant-remains but seed-like structure absent Pistillaria

7. Fruit-body much branched; spores ornamented (see also Thelephora below) Ramaria

Fruit-body simple or if with well-developed branches then spores smooth 8

8. Fruit-body branched irregularly with many to few branches, grey, white or drab-coloured; spores large, subglobose and smooth Clavulina

Fruit-body club-shaped or if branched then brightly coloured and spores not large and subglobose Clavaria, Clavulinopsis & Clavariadelphus

9. Fruit-body resembling an agaric with spores borne on fold-like, often forked and shallow ridges and veins, and often brightly coloured Cantharellus (compare carefully with Craterellus below)

Fruit-body funnel-shaped or fan-shaped 10

10. Fruit-body often drab colour or greyed with smooth or slightly veined outer surface Craterellus

Fruit-body wrinkled, irregular or smooth and powdery, lilaceous to chocolate-brown in colour Thelephora

11. Fruit-body sessile or resupinate and fleshy; spores borne on veins united to form shallow pores 12

Fruit-body resupinate or bracket-like, and spore-surface veined or rugulose but lacking distinct pores 13

12. Spores colourless Merulius