140 _ College of Forestry 
study of the decay of one or two woods that the fungus 
destroys the pith-rays first, for example, since while such 
might be the case in woods with uniseriate or small pith- 
rays, the same course might not hold true in other woods 
possessing large multiseriate pith-rays. To my mind, in the 
past sufficient emphasis has not been laid upon the physical 
structure and chemical composition of wood when considering 
its decay by any particular fungus or when considering its 
predisposition to decay when subjected to known conditions 
under given uses. A knowledge of the chemical nature and 
physical structure of wood, however, has long been taken 
advantage of in connection with the preservative treatment 
of wood. In this connection a knowledge of both points 
would be of the utmost fundamental importance. For exam- 
ple, the Chicago, Burlington and Quincy Railroad has found 
by actual experimentation that it was not worth while to 
apply a preservative treatment to chestnut ties, since treated 
ties exhibited no greater resistance to decay and consequently 
no greater length of life in service than the untreated ones. 
The reason for this is that chestnut wood already contains a 
large amount of tannin which acts as a natural antiseptic or 
preservative and thereby retards the establishment and 
growth of wood-destroying fungi. Again, the abundance of 
tyloses in the vessels of the white oak group of woods has 
been found to render the wood very difficult to impregnate 
with preservative solutions. By reason of this peculiarity 
of structure, the woods of the white oak. group are especially 
suitable for making liquid-tight containers (tight cooperage 
stock). 
LOCALIZATION OF THE Decay. 
Undoubtedly the most peculiar and perplexing point m 
connection with the decay resulting from the action of Poly- 
porus pargamenus is its habitual tendency to produce a 
minute, inconspicuous pocket type of decay. Unlike a great 
number of decays that produce a rot in which the entire 
mass of the wood is immediately affected, Polyporus parga- 
