528 Fischer. — The Biology of A r miliaria mucida , Schrader . 
was reinoculated with pieces of mycelium from a pure culture, in incisions 
extending to the wood. It was then placed in a vessel of water standing in 
a stoppered jar. In a short time white mycelium in abundance appeared 
on the outside of the twig and soon spread around, attaching the twig 
to the side of the vessel. On microscopical examination it was ascertained 
that the hyphae had penetrated right to the centre of the wood, and 
no starch reaction was obtained with iodine (the fungus absorbs the starch, 
as will be seen later). In places the mycelium had found its way between 
the epidermis and the cortex, and had separated the two in waved lines, 
raising the epidermis in a blister-like manner. 
The two last described experiments were repeated with the same 
results, which seems to show that the fungus is unable to effect an entry so 
long as a certain proportion of moisture in the wood is exceeded, with 
a corresponding lack of air. This is quite in accord with the results of 
Munch’s researches with Nectria ditissima , Cerastomella coemdea , and other 
facultative wood parasites (18). 
On sterilized thin unbarked beech twigs, mycelium inoculated from 
a pure culture grew very rapidly, entering the wood at the cut surfaces. 
An abundant dense, pure white mycelium overspread the twigs and extended 
all round and over the inside of the glass receptacle, and eventually it gave 
rise to two carpophores. 
Deductions as to Parasitism. 
We can now consider how all the experiments described above affect 
the question of the parasitic nature of Armillaria mucida. We have seen 
that attempts to grow the fungus as a parasite have failed, but on the other 
hand it was readily cultivable as a saprophyte on several nutritive media. 
It could also be grown on dead beech wood, on which it produced fructifica- 
tions. In fact, the evidence so far available nowhere records the appearance 
of fruit bodies on living wood, though it is to be seen on dead parts of living 
trees. It is possible that it is a facultative parasite demanding specially 
favourable conditions to enable it to attack living tissues. It seems possible 
that it must first develop saprophytically and then, after a start, during 
which it has gained vigour, is able to enter upon a parasitic existence. 
These conditions would be secured at a point where a branch has broken 
off and the surface tissues have died from loss of moisture, but as yet 
we have no certain evidence in support. 
It may be noted, also, that no one has recorded the occurrence of 
the fungus on young beech plants. 
