HEART-ROT CAUSED BY OTHER FUNGI 127 
reason to suppose it is confined to those counties. The 
parasitology and method of attack of the fungus have not 
been worked out. The best papers on the disease are by 
Hartig (1878), who described it under the name of Polyporus 
mollis, Fr., and gave an account of two hundred-year-old 
Scots pines which had been attacked by the fungus, and by 
Schrenk (1900), who described the rot on American trees 
and made interesting observations on the fructification. 
Fractification. This may arise either from the roots, 
often at some distance from the trunk, or on the trunk 
itself up to 10 or 12 ft. When growing on roots that are 
buried its connexion with the tree may not be observed until 
the roots are bared of earth, but in other cases it may arise 
from parts of roots that are exposed to the surface. In 
either case it is stipitate, i.e. has a stalk with an expanded 
pileus as in fig. 46. Sometimes, as in the figure, two or more 
stalks may grow up side by side and their respective pilei 
grow into each other, or become congruent. The pores are 
borne on the lower side of the pileus, and the upper swollen 
part of the stipe also becomes pore-bearing, so that there 
is no sharp line of demarcation between the pileus and the 
stipe. When growing on the trunk the fructification has 
a totally different form. It is then bracket-shaped, as in 
fig. 47, with a more or less distinct stalk; and often the 
brackets are imbricated, borne closely one above another, 
in which case there is usually no stalk visible. The fruit- 
bodies are generally about 6 in. across, but specimens up to 
16 in. have been measured. 
Though the two forms of fructification are so different 
in their general shape, the details of structure are identical. 
The upper surface is dark, reddish brown in colour, and 
rough with excrescences. The pore-bearing under-surface 
is greenish when young, but changes to red on being touched, 
and during the period of active growth it exudes numerous 
drops of liquid. Unlike Fomes annosus, the fructification 
is not woody, but soft and fairly light. It hardens some- 
what with age and dries up and dies in the autumn. It 
generally falls from the tree in late winter unless it has been 
