THE HONEY FUNGUS 163 
only one tree, a Corsican pine, has so far been attacked. 
(There is no plot of Scots pine.) Not a single larch, deodar,1 
or Norway spruce has been affected, though from other 
woods I have obtained specimens of each of these species 
killed by the fungus. If perfectly healthy roots were liable 
to be penetrated by the rhizomorphs, I do not think that such 
immunity could have been expected. 
In a larch tree in a neighbouring plantation, about eighteen 
years old, which showed only the early stages of attack, I 
found that the rhizomorphs had entered through a wound 
in the bark at the base of the trunk. In this case the roots 
and rootstock presented more than a square foot of un- 
damaged bark, and yet the fungus found out the square 
inch of wound. Further instances might be quoted from 
other observations, but enough has been said to show the 
improbability of infection through healthy bark. 
From Brefeld’s experiment we know that rhizomorphs 
can enter dead roots, and it is probable that this faculty is 
commonly employed by the fungus. The importance of 
dead roots has been fully discussed in the chapter on Fomes 
annosus, and need not be reiterated; and though this 
method of attack by Armillaria raises some further questions, 
these have not yet been investigated. Infection through 
dead roots may account for a phenomenon that is frequently 
observed—I refer to the case of larch woods which remain 
practically free from infection by Armillaria until they 
reach an age of more than fifteen years, after which many 
trees succumb within a short time. The presence of the 
fungus may have been detected many years previously, 
but it had to wait until the death of some of the tree 
roots afforded'a means of entrance into the living trees. 
Means of prevention. The forester is too often taken 
unawares by the honey fungus, but generally a surprise is 
due to lack of previous observation. When oak or beech 
woods are cut down the fungus must be expected, and any 
coniferous plantations on a site which has previously been 
occupied by such trees are especially liable to attack. 
1 One deodar was killed this year (1919). 
M 2 
