1917] 
ZELLER—DURABILITY OF YELLOW PINE 97 
and water, but, if slow, the hard resins are laid down within 
the wood, thus increasing durability. 
We notice here that Mayr seems to lay as much stress upon 
specific gravity as a factor in the resistance of wood to 
fungous decay as he does on the resin content. Practically 
the same idea is conveyed by Falck (709), who says that all 
three species of Lenzites (L. saepiaria, L. abietina, and L. 
thermophila) will attack pine sap-wood more readily than 
heart-wood, and coarse-grained or non-resinous sap-wood 
more readily than dense or resinous material. Pine heart- 
wood is attacked with difficulty, even by Merulius lacrymans, 
and hard, resinous knots, ete., are always immune. 
Speaking of the decay of wood produced by Lenzites 
saepiaria, Spaulding (711) suggests that resin is a factor in 
the resistance of southern pine. He states that ‘‘Whether it 
is able to rot the resinous heart-wood of the southern pines 
seems questionable. The writer has seen no instance where 
this has taken place, except in the outer layers of heart-wood 
which were not so completely filled with resin as the inner 
ones.’’ 
Hoxie strongly advocates resin as a criterion of the 
durability of pine wood. However, he has advisedly included 
in his specifications (Hoxie, 715) density (specific gravity of 
about .48), percentage of summer wood (33.3 per cent), and 
growth rings per inch as factors of importance. In 1914 he 
performed a very simple experiment from which he concluded 
that ‘‘resin is the important factor in the hard pines. 
A block of longleaf pine 2 in. on a side, containing 18 per cent 
of resin, was sawed in two across the grain. Half of it was 
boiled in benzole and after the removal of the resin the ben- 
zole was driven off. Both pieces were cultivated in contact 
with wood containing living dry rot fungus. At the end of a 
year the specimens were dried and weighed. That from which 
the resin had been removed had lost 8 per cent in weight, the 
other only 2 per cent.’’ This is in accordance with Mayr ('94), 
who has said that of two blocks having the same specific 
gravity, but the one resinous and the other not, the resinous 
will be the more resistant. However, when we consider the 
