HEART-ROT 81 



m 



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 gi'ey above and salmon coloured beneath, which provide 

 spores for further infection by the fungus. Often by the 

 subsequent attack of other fungi the tree is killed, and then 

 the mycelium of Fomes ulmarins 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 holloAvness 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 mu.st 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 imjoortance that woods 

 should be grown under conditions in which disease is not 

 likely to occur, and the most essential jiart of our investiga- 

 tion of the pathology of the fungi will bo that concerned 

 \vith 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 earher 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 Q 



