HEART-ROT 87 



criticism. Certainly the discovery of conidia profoundly 

 affected the value of the measures by means of which Hartig 

 sought to combat the disease. A more general account of 

 the fungus and its effects on trees may be found in the 

 translation (1894) by Somerville and Marshall Ward of 

 Hartig 's Diseases of Trees. 



Heart-rot is the cause of very serious financial loss to 

 foresters. It occurs with alarming frequency in woods 

 which are planted as a first rotation on land that has pre- 

 viously been arable or waste, and acres of plantations may 

 be reduced through it to two-thirds their value or less. 

 And since in Britain new land is frequentty being converted 

 into forest, a conversion which is likely to be much accele- 

 rated in the near future, the disease must be regarded as 

 one of our most serious enemies. Plantations on old forest 

 land, however, remain comparatively free from heart-rot, 

 so that we may look forward with more confidence to the 

 yield of later rotations on land which is at present being 

 afforested. 



Though Fomes annosus is found in North America, it 

 does not appear to do so much damage there as other heart- 

 rotting fungi. Butler (1903) records its occurrence on 

 deodar in India, but his description and figures suggest that, 

 if this fungus was present, it was working in collaboration 

 with Armillarla mellea. 



In the following sections I shall describe in detail the 

 various characteristics of the disease as it appears in the 

 larch. Afterwards I shall deal with the methods by which 

 the fungus attacks the trees, and with the means of com- 

 bating it and minimizing its depredations. 



Secretions induced by Fomes annosus. (i) Turpentine and 

 resin. In the early stages of attack by the heart-rot fungus 

 the wood assumes a reddish-brown aj)pearance. This red 

 region usually surrounds all parts which are actually rotted 

 by the fungus, and advances in front of the heart-rot as it 

 ascends the tree. At first it resembles a red duramen, but 

 its tone is generally redder and deeper than that of normal 

 duramen, and the outside limit of red coloration may cut 



