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. Schweinitzti, 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 Portia 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 
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