122 HEART-ROT 



I sought for a similar line of resin in other roots, but they 

 were too far rotted to show any trace of it. Thus, though 

 these roots are killed because they grow deeply, it is not 

 necessary that their point of infection is deep. 



The statement that larch is more liable to heart-rot in* 

 pioneer stands than in subsequent rotations is not accepted 

 by all writers on the subject. In particular, Elwes (Elwes 

 and Henry, 1907, vol. ii, p. 363) holds that the rot is more 

 often found in the second rotation. This runs directly 

 counter to my experience, and the issue can only be settled 

 by the counting of woods in which the incidence of heart- 

 rot has favoured Elwes's view or mine. In discussing the 

 question, Elwes does not say which of the heart -rots he 

 was referring to, whereas my observations are only con- 

 cerned with Fomes annosus. Ribbentrop (1908) shows that 

 in Germany the first rotation has given most trouble with 

 root-rots generally. 



Methods of prevention. The only preventive measure 

 which, as far as I know, has been recommended for defence 

 against Fomes annosus, is digging a trench round all the 

 infected trees. This method was adopted by Hartig in the 

 forests near Eberswalde, and the trenches were apparently 

 dug with the object of cutting off all the roots so that infec- 

 tion should not pass from root to root from infected trees 

 to other parts of the forest. Kienitz found that, in one of 

 the trenches that Hartig had cut, fructifications developed 

 on the cut and exposed roots, so that in this case the remedial 

 measure proved to be a source of danger. He referred to 

 the treatment as ' waldverderblich ', an expression which 

 Brefeld quotes with relish. Hartig replied that a trench 

 could easily be watched for fructifications which could be 

 removed, and persisted in his recommendation. But the 

 conidia discovered by Brefeld present a fresh difficulty. 

 These cannot be removed, for they cannot generally be seen. 

 And now that we know that the mycelium can grow in the 

 humus itself, a trench does not seem a likely method of 

 preventing its further expansion. I have found, however, 

 that when 10 per cent, of lime is added to humus soil, the 



