HEART-ROT 83 



distance from the trunk. The fungus is especially frequent 

 in the south of England, and grows on the Scots pine and 

 maritime pine as well as the larch. 



Heart-rot of the larch is also caused by Polyporus sul- 

 phureus, a fungus which is easily recognized by its bright 

 yellow, bracket-shaped fructifications which appear in July 

 and August. It is most common on oak, in which tree it 

 also produces heart-rot, but I have also a specimen of larch 

 which has been rotted by this species. The rot is similar 

 to that caused by P. Schweinitzii, but fractures occur 

 especially in the first-formed elements of the spring wood, 

 so that the annual rings become separated from each other. 

 Also the turpentine smell is absent. 



In Germany Poria vaporaria has also been frequently 

 recorded as a cause of heart-rot in larch and other conifers. 

 It is very doubtful whether the species which is alluded 

 to in these records ever occurs in Britain. The name 

 has been made to cover a large number of closely associated 

 species, and though I have found a Poria growing on dead 

 larch trunks and apparently causing a rot closely resembling 

 that described by Hartig, I have never been able to deter- 

 mine its capacity to grow in living trees. This fungus also 

 causes a rot which resembles that of Polyporus Schweinitzii. 



Trametes Pini is another wound parasite which attacks 

 the larch through branch stubs near the crown of large trees. 

 It causes a very distinctive rot, which is described on p. 140. 



There are thus four, or perhaps five, distinct species of 

 fungi which attack the heart-wood of the larch, and each 

 of these will be more fully described in the ensuing chapters. 

 But before closing this general introduction to the heart - 

 rots, it should be noted that the first two differ from the 

 remainder in one all -important respect. Fomes annosus 

 and Polyporus Schweinitzii are essentially root fungi, that 

 is to say, they attack the roots first, and always advance 

 from the roots to the trunk. Polyporus sulphureus and 

 Trametes Pini, on the other hand, gain admission in the 

 same way as Fomes ulmarius on the elm. They attack the 

 heart-wood which is exposed when branches fall off, and 

 o 2 



