CHAPTER VII 
HEART-ROT CAUSED BY OTHER FUNGI 
Polyporus Schweinitziit, Poria vaporaria, Polyporus sulphureus, Trametes 
Pini. 
Heart-rot caused by Polyporus Schweinitzii, Fr. Next to 
Fomes annosus this fungus is the most frequent cause of 
heart-rot. Though in many respects resembling the two 
following diseases, this rot may easily be distinguished from 
that caused by the Fomes by the rotted wood being very 
dry, light, and friable, and not spongy or fibrous. It has 
marked cleavage surfaces which are at right angles to each 
other, so that the wood breaks up easily into more or less 
cubical blocks, and, owing to shrinkage, the cracks often 
open before the tree is felled and the interstices become 
filled with white mycelium which frequently becomes 
embedded in resin and assumes a chalky consistency. When 
the rot is far advanced the wood is usually light or dark 
brown and reeks strongly of turpentine. 
The fungus enters by the roots and grows up the stem, 
and is in the vast majority of cases confined to the heart- 
wood. But dead trees are occasionally found in which all 
the wood up to 20 ft. or more from the ground is rotted. 
The disease is reported as fairly common on the -Con- 
tinent, especially on Scots pine, Weymouth pine, and 
larch. There are frequent notices of it in the United States 
of America on Weymouth pine, balsam fir, white and red 
spruce, and arbor vitae, and in New England it is con- 
sidered one of the most destructive diseases (Schrenk, 1900). 
In Scotland, Murray (1916) reports it as occurring on 
Douglas, spruce, and Scots pine. My own observations 
have been made in the south of England, where I have 
found it on Scots pine, cluster pine, and larch, chiefly in 
Sussex, Surrey, Berkshire, and Devonshire, but I have no 
