[VoL. 4 
98 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
variableness in weight of samples of the same species of wood 
the value of Hoxie’s experiment may be questioned. 
Hoxie’s specification of “поё less than 4 per cent resin’’ 
was based on ‘‘the percentage of resin in the sound centers 
of rotted beams taken from a mill.’’ This resin content **was 
determined in order to get an idea of the amount required to 
stop fungous growth under ordinary mill conditions. In rotted 
beams of the poorest of hard pine there is generally a sound 
center which contains more resin than the remainder of the 
section. Sometimes it is not bounded by the growth rings but 
is very irregular, the cause being that resin has been irregu- 
larly deposited in the section owing to knots or injuries to the 
tree. The limits of the sound centers are frequently not the 
same as those of Ше heart-wood.’’ In these cases Hoxie found 
that the limiting amount of resin which is just sufficient to 
stop the fungus is in the neighborhood of 3 per cent. Fur- 
ther, “Тһе limiting power of resin is undoubtedly not absolute 
but varies with the moisture, variety of fungus and time of 
exposure. "Therefore, it is safe to assume that a mill beam 
should have not less than 5 per cent of resin throughout suc- 
cessfully to withstand fungus under ordinary conditions of 
dampness and allowing a reasonable factor of safety." 
While Hoxie has considered that the irregularity of the 
limits of the sound centers described above is due to the 
irregular distribution of resin, he has said nothing of the 
cracks in the beams due to seasoning. It has been the experi- 
ence of the writer that fungous decay generally proceeds far- 
ther toward the pith of a timber along such seasonal eracks. 
This may also account for an irregular decay. 
Another factor which Hoxie ('14) has considered is the 
relation of relative humidity of the air to fungous decay. He 
says: ‘‘Wood will become dryer or wetter in proportion to 
the relative humidity of the air; . . . Moreover, the sus- 
ceptible varieties absorb moisture more rapidly than those 
which are more resistant to fungi.” 1 
the 
fungi will be prepared by the writer. The relation of the relative humidity of 
the air to the absorbing power of various species of yellow pine will be a pre 
liminary consideration. 
