HEART-ROT CAUSED BY OTHER FUNGI 133 
into the stem. This appears to be invariably the case, as 
no instances have been reported in which the fungus has 
attacked the tree through sub-aerial wounds. The mode 
of growth of the fungus in the tree suggests that, if it is 
a parasite at all, it is a very feeble one, and it is extremely 
improbable that the fungus can attack a living root, even 
when it is wounded, unless some of the dead wood is exposed. 
Very likely its habit is to gain entrance to the tree through 
dead roots, but by what means it reaches dead roots is at 
present entirely unknown. 
Cure of the disease is, of course, impossible. The forester 
must remember that he has a sixth sense in his Pressler 
borer, a sense which he should use with enthusiasm and 
discernment. If he watches carefully for the incidence of 
heart-rot caused by Fomes annosus (yee p. 122) he will be 
equally guarded against this other heart-rot; at any rate 
he will not receive his first intimation of it when the woods 
are cut, but being warned beforehand, he will be able to use 
his discretion as to whether the woods should be cut before 
normal financial maturity is reached. But apart from the 
borer, the presence of P. Schweinitzii can generally be 
detected by its fructifications. It fructifies much more 
freely than Fomes annosus in the early stage of rot, and as 
the fructifications are sub-aeria]l they can always be seen. 
A special look-out should be maintained for the upright 
fructifications, like that in fig. 46, which grow from the roots, 
and may have no obvious connexion with the tree on which 
they are feeding. These may be formed before the trunk is 
appreciably affected, whereas fructifications are not borne 
on the trunk itself until it is either dead or very severely 
damaged. August is the best month in which to look for 
these growths, and when they are found they should be 
picked and destroyed in order to restrict the further dis- 
tribution of the fungus. Of course the removal of the 
fructification will not help the tree that is actually attacked, 
and an investigation of the roots of the tree is advisable, 
as if the attack is not far advanced it may be possible to 
remove all the diseased roots, which are very probably 
