HEART-ROT 81 
elms. When attacked by this fungus the heart-wood 
assumes a reddish-brown colour, and ultimately falls to 
dust, leaving the centre of the tree hollow. Large woody 
fructifications are borne inside the hollow trunk, white or 
ashy grey above and salmon coloured beneath, which provide 
spores for further infection by the fungus. Often b® the 
subsequent attack of other fungi the tree is killed, and then 
the mycelium of Fomes ulmarius spreads through to the 
bark and more fructifications are produced on the outside. 
I have cited the instance of the elm as it is familiar to 
every one. The hollowness of the trunk is commonly 
discernible from the outside, and the fructifications can 
frequently be found. With conifers this is not so. The 
destructive work of the fungus is the more insidious by its 
very secrecy. The heart of the tree is eaten away, and the 
evil is betrayed by scarcely an external sign which would 
warn the forester to cut the trees before the damage has 
progressed so far that the base of the tree has become 
worthless, and most foresters must have experienced the 
disappointment of finding some of their finest specimens of 
larch or Scots pine rotted up to 10 or 20 ft. from the ground, 
when they had expected to obtain sound healthy butts. 
It must be admitted at the outset that the cure of trees 
which are attacked by any of the heart-rotting species is 
impossible. It is thus of supreme importance that woods 
should be grown under conditions in which disease is not 
likely to occur, and the most essential part of our investiga- 
tion of the pathology of the fungi will be that concerned 
with the mode of infection of the pests. No detail which 
has any bearing on the problem of infection can be ignored, 
and since a fungus may become reproductive in any stage 
of its existence, we must familiarize ourselves with every 
part of its life-history. To prevent loss it is also necessary 
to keep a careful watch on all plantations and to adopt 
every means at our disposal of tracing the earlier symptoms 
of the rots. It may then be possible to thin out those trees 
which would afterwards have become reduced in value, and 
if whole woods are attacked it may be more profitable to 
1888 @ 
