HEART-ROT 85 
rots the centres of the trees without destroying the vital 
tissues, so that the trees continue their growth and appear 
to be healthy until they are cut down, when the basal part 
of the tree is found to be valueless.. The disease is some- 
times accompanied by a swelling of the base of the trunk, 
known to foresters as ‘ goutiness’, but it is by no means 
safe to diagnose the disease on the basis of this single 
feature. 
Conifers are not so often killed by the fungus when 
attacked at this later period, but when the trees are weakened 
by the overshadowing of other trees, death may ensue. 
And larch is killed in this way less often than spruce or 
Scots pine. At the same time larch is more frequently 
heart-rotted than either spruce or pine, at any rate in the 
south of England. I have never seen silver fir rotted by this 
fungus, though instances are recorded on the Continent. 
Since in pumped trees the fungus is confined to the heart- 
wood, fructifications are not generally formed on living 
trees. But when the trees die the fungus penetrates to the 
bark, and often bears large fructifications such as those 
shown in figs. 29 and 30. This accounts for the comparative 
infrequency of fructifications of Fomes annosus on larch 
trees, and consequently for the doubt that has often been 
expressed as to the connexion between this fungus and the 
rot. But I have twice found unmistakable fructifications 
of the fungus growing in direct connexion with the rot in 
living trees, once on the roots of a wind-blown larch near 
Tintern, and the other time on a tree which I had dug up 
at Terringham Wood in the Forest of Dean. Probably 
fructifications are frequently borne in this way on the roots, 
but being subterranean they remain unseen. 
If further evidence is needed to confirm the connexion 
between Fomes annosus and the larch heart-rot, it is pro- 
vided by series of cultures taken on the one hand from 
pieces of rotted wood, and on the other from spores of the 
fungus. These are identical in all respects, and agree in 
the possession of a peculiar type of conidiophore which is 
at present unknown in any other fungus. 
