8 BULLETIN 658, U. S. DEPARTMENT OF AGRICULTURE. 
‘ 
case an estimator wished to give a full estimate of a stand of white- 
bark pine (Pinus albicaulis Engelm.) growing upon a flat ridge. The 
trees of this stand upon closer examination were found to be almost — 
universally heart-rotted with Polyporus schweinitzii for a distance of 
5 to 12 feet up from the base. The trees were fairly large and if 
sound would have made excellent stull material, the chief product 
in the Big Hole Basin region of Montana. Giving a full estimate to 
these trees would have meant a serious overestimation of the stand, 
since it was finally estimated that about 40 to 50 per cent by volume 
was cull due to the heart-rot. Fruiting bodies of the causal fungus 
almost hidden in the dé- 
bris at the base of the 
trees gave the determin- 
ing clue, and soundings 
upon the trunk followed 
by notching completed the 
determination. | 
There has always been 
a serious need for some 
method by which a fairly 
accurate estimate can be 
made of the rate of decay 
of a stand of timber. 
Good results as to the 
probable cull percentage 
to be expected from rot 
upon a certain stand have 
been secured by expert and 
experienced cruisers and 
appraisers. Timber sur- 
veys have in most cases 
placed the estimates of 
Fic. 9.—Polyporus sulphureus, sulphur fungus, at sound timber within a rea- 
base of larch. sonable limit of error; but} 
evidently no attempt has ever been made to secure a more accurate 
result in respect to the cull in a stand due to rot other than thosef. 
results secured by ocular estimates. Occasionally in the administra- 
tion of National Forests the question arises concerning the probable 
rate of increase in rot per annum in a certain stand of timber. The 
resultant decision as to the time of disposal of the timber hanging 
in the balance depends upon the amount of accurate knowledge and 
the data at hand regarding the decay in the trees. If proper and 
sufficient data are secured, these will furnish the total volume and§ 
the total volume of rot for the stand in question. With these as a 
