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. 



