166 College of Forestry 
grow very fast, and, after attaining maturity, they are 
destroyed by insect larve or they die and decay. During 
this time the mycelium of the fungus spreads rapidly, attack- 
ing hitherto sound sapwood, and in the following year new 
fruit-bodies are produced which give further indication of 
the spread of the mycelium throughout the wood, and, con- 
sequently, of the extent of the decay. After building up 
considerable strength in its saprophytic hfe the fungus pro- 
ceeds to attack the growing zone of the trunk, that is, where 
the sapwood joms fhe bark and where the living substance 
is produced by very thin-walled cells. Thus the host is slowly 
killed and the fungus continues to live on in its saprophytic 
way. The remaining sapwood soon becomes changed to a 
brittle substance having none of the properties of wood. 
These changes soon kill the tree by girdling it and eventually 
weaken the trunk so that it is only a question of time until 
the tree becomes broken by the wind. At this stage the 
basal portion of the trunk, up to a height of several feet, 
usually is surrounded entirely by a luxuriant growth of fruit- 
bodies froming a closely imbrieated mass (Plate XXXI, 
Bags al.) 
Polyporus pargamenus is one of the wood-rotting fungi 
which commonly appear on standing deciduous trees after 
forest fires have killed a portion of the cambium. One can- 
not help but take cognizance of the total destruction caused 
by a large forest fire, but few even apprehend the extent of 
damage done by a small surface fire which quickly consumes 
whatever superficial litter there may be lying on the ground 
at the time. Such fires, although they may not seem to 
have injured the trees at the time, usually generate sufficient 
heat to kill the inner, living bark and cambium over a consid- 
erable area at the bases of the trunks. The bark over such 
areas dries out and cracks, causing the death of the under- 
lying sapwood. It is in such dead areas that fungi find a 
ready entrance. The injury thus caused apparently is slight, 
but in reality the damage done may continue during the 
entire life of the tree and eventually cause its death. Such 
small fire scars are responsible for a large amount of fungous 
