1917] 
ZELLER—DURABILITY OF YELLOW PINE 101 
practically untouched, while others may decay only the sap- 
wood, or both. Falck (’09) points out that Lenzites abietina 
and L. thermophila attack the sap-wood, while in cultures set 
up in the same, L. saepiaria will decay both Ше sap- and Ше 
heart-wood. Hartig (’02, p. 44) has shown that the sap-wood 
of Pinus sylvestris (Kiefernholz) is attacked by Merulius 
lacrymans more readily than the heart-wood, while the heart- 
wood of Picea excelsa (Fichtenholz) is more readily decayed 
by the same organism than the sap-wood. These are striking 
examples of the specificity of certain organisms, and indicate 
how the chance of infection of wood may vary with circum- 
stances. 
Hoxie (715, р. 60) has taken these results obtained by Har- 
tig, and on the basis of average resin analyses made by Mayr 
(794) has concluded that this difference of resistance in the 
two species of wood is due to their resin content. However, 
since resin is so variable within the same species of wood, the 
analyses made by Mayr could hardly be considered compatible 
with decay experiments conducted by Hartig on different sam- 
ples, although for the sake of argument there does seem to be 
a relation. This, nevertheless, could not apply to the resin in 
the sap-wood if we accept the results of Mayr ('94, p. 70), 
who shows that fungi thrive on resin in the liquid state as it 
is found in the sap-wood. 
Humphrey (716) has started a series of laboratory tests on 
the durability of American woods, the first of which reports 
the deeay of various species of conifers induced by Lentinus 
lepideus Fr. Before the experiments were set up the test 
blocks were weighed, but no record was kept of their relative 
specific gravity, percentage of summer wood, resin content, 
etc. The test blocks were allowed to decay for intervals of 
4, 6, and 12 months, and it is interesting to notice that after 
12 months the sap-wood and heart-wood of longleaf pine were 
reduced in weight more than those of shortleaf. Humphrey 
says that ‘‘the specimen of longleaf pine, which did not ap- 
pear very highly resinous, did not prove as resistant (51.1 per 
cent reduction) as shortleaf pine (20.7 per cent reduction), 
which was of a good grade.’’ Since these tests are on one sam- 
