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THE ESSEX NATURALIST
Armillaria mucida, it is especially associated with beech,
although more rarely it is found on other broad-leaved
trees. It may also occur as a saprophyte, and the slate-grey,
fleshy fruit-bodies are commonly to be seen on felled beech
trunks. This is a well-known edible fungus. In France,
fallen trunks bearing the mycelium of this species are kept
watered to produce crops of sporophores for the pot.
Bather similar to the Oyster Fungus in its relationship to
beech is Bulgaria inquinans (Plate 10). This is a cup-fungus
forming black gelatinous apothecia with the texture of
india-rubber. This species attacks the bark rather than the
wood, but so far as living trees are concerned, it is only old
ones that are affected. It is also a common and conspicuous
saprophyte of felled trunks. It is equally common on oak.
So far I have discussed fungal diseases as they affect
mature trees, but the beech may also be attacked at an
earlier stage. In very damp seasons there is considerable
seedling loss due to the activities of Phytophthora cactorum.
Again, young trees up to 20 years old are often seziously
affected by Nectria ditissima, which causes stem cankers.
The same organism is responsible for apple canker, one of
the worst diseases of orchards.
Although there are quite a number of fungi that attack
the beech, particularly when it is mature, I think it is true
to say that living beech is not very prone to fungal attack.
However, once the tree is dead, the fungal flora developing
saprophytically on the stumps, fallen trunks and larger
limbs, and also on the finer dead twigs, is very considerable.
Indeed, a complete list of the wood and bark fungi growing
on beech is a very long one, including about 90 Basidio-
mycetes and twice that number of Ascomycetes*.
I would turn aside for a few moments to consider dead
beech stumps and trunks as a substratum for the growth
of fungi. First, some species grow on the bark. Mention
has already been made of Bulgaria inquinans, but most
bark species belong to Pyrenomycetes, for example,
Hypoxylon coccineum, with hard, dark-red perithecial
stromata often occurring in great numbers on dead
trunks, and Diatrype stigma, which forms extensive
*Data from Oudemans' Enumeratio Systematica Fungorum.