168 College of Forestry 
growth of fungi, the most favorable temperature being about 
90 degrees F’. They cannot grow in extreme cold, although 
no degree of cold that occurs naturally will kill them after 
they have become well established.”4 
Like all sap-rotting fungi, Polyporus pargamenus is 
especially dependent for its development upon the presence 
of a sufficient quantity of water and air. It usually grows» 
with the greatest vigor close to the surface of the soil. Its 
fruit-bodies may therefore be looked for at the base of trees 
and at or near the ground line on ties, posts, and all timbers 
exposed to the soil. Where wood has time to dry partially 
on the outside after it has been cut, the spores will not ger- 
minate owing to the lack of moisture. Infection of such 
partially dried wood usually takes place through some season 
check. 
Polyporus pargamenus may start development in a stick 
of wood within a few weeks after it has been cut, or, in 
other words, shortly after the wood becomes sufticiently dried 
on the outside to form season checks. After it has once 
gained entrance below the surface the mycelium will grow 
vigorously in the wood and give absolutely no macroscopic 
evidence ‘of its presence on the outside until the mycelium 
has become sufficiently developed to form fruit bodies, which 
then usually form by growing out through the season checks 
to the outside air. It is on account of its ability to produce 
decay in the interior of the wood that this fungus is so very 
destructive, and it is for this reason that the greatest care 
should be taken to guard against its possible entrance. In 
moist climates the fr uiting Bache: will form above the ground 
on moist wood which may be several feet above the eround. 
Where wood has a chance to have air circulate around it 
continuously, however, the possibilities of its becoming 
infected with this fungus are remote. 
* Buller (1912) showed that the fruit bodies of Schizophyllum com- 
mune Fr., after having been kept dry and exposed to air for 2 years and 
8 months, are able to “retain their vitality when subsequently they have 
been dried in vacuo and subjected to the temperature of liquid air 
(— 190° C.) for three weeks. ‘The retention of vitality was indicated 
by the fact that, upon being moistened, the fruit-bodies commenced to 
shed spores. 
