Nov., 1922] KAUFFMAN AND KERBER HEART-ROT OF LOCUST 
Table 4. Apparently Sound Wood Taken from Section IV 
Blocks I, 2, and 3, nearest the decayed area; blocks 3, 4, 5 and 6, farthest away from 
the diseased area. 
Block 
Size (Inches) 
CrUvShing Strength 
Crushing Strength per Sq. In. 
1st Fail 
2d Fail 
3d Fail 
I 
2 
3 
I 
1.87 X 1.87 
20,000 
20,000 
20,500 
5,714 
5,857 
5,857 
2 
1.85 X 1.87 
19,000 
20,000 
20,000 
5,277 
5,555 
5,555 
3 
1.80 X 1.80 
22,000 
22,000 
22,000 
6,790 
6,790 
6,790 
4 
1.82 X 1.79 
26,500 
27,000 
27,000 
8,134 
8,250 
8,250 
5 
1.79 X 1.75 
29,000 
29,000 
29,000 
9,257 
9,257 
9,257 
6 
1.83 X 1.80 
26,000 
26,000 
26,000 
7,893 
7,893 
7,893 
grain, whereas blocks 4, 5, and 6, which were taken from a greater distance 
away from the rot, run much higher but still do not approach normal except 
in the case of block 5, which shows the highest strength per square inch 
but no resiliency of the wood. In blocks taken from section VI, there is a 
distinct difference between the first failure and the third failure of about 
500-900 pounds, but it should be compared with the test of section IV, in 
which the failure is final in most cases for a certain load. When the blocks 
give, they give all at once, which is contrary to what we expect from normal 
locust wood. It was also noticed in the testing of all the blocks that up to 
about the fir^al 2/3 pounds per square inch the blocks behaved quite nor- 
mally, but after heavier weights were applied, the wood reacted in general 
like one of the softer deciduous woods. 
Discussion and Summary 
Several points brought out in this study may prove of far-reaching 
significance. As already indicated in the remarks about the blackish- 
brown zone (page 501), certain ideas concerning the occlusions in the ele- 
ments of this zone must be revised . In this case, at least, these occlusions can 
play no part as a protection against invading mycelium, as was suggested by 
Lindroth (1904) and others. Nor can we generalize, as did Rhoads (1917), 
that "the brown substance ... is indicative of the first stage in the de- 
composition of the wood"; for the beginnings of the weakening of infected 
wood, as shown by the tests, are already initiated outside the black zone 
for a considerable distance, and are probably much more advanced than a 
microscopic observation alone shows. 
"Advance rot" has in recent years been given considerable attention, 
and during the world war the price paid in human lives as a result of weak 
spots in aeroplane timber instigated special research along this line by the 
national government. Unfortunately the results of these studies are not 
yet available in the Hterature. Boyce (1920, p. 15) found in the dry rot 
of incense cedar, where the decayed areas alternate with apparently sound 
wood, that "hyphae were commonly present in the apparently sound wood 
